Foot-and-mouth is highly contagious, making it a serious threat to the agriculture industry. Viral strains can be stored in vaccine banks, but right now there’s no computer model to predict which strain will best control an outbreak.

Successful small businesses will receive up to $150,000 to refine their research, through Innovative Solutions Canada. If accepted into the second phase, a small business could receive up to $1 million to develop a working prototype. The government would then act as a first customer, which would help small businesses commercialize their innovations and scale up their business.

The call for proposals closes on October 29. For more information, visit ‘Challenges’ at the Government Canada website.

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Cattle can become exposed to BVD in several ways, and some U.S. studies have estimated that 70 to 90 per cent of infections go undetected, without visible symptoms. The only clue you might have that BVD virus is in your herd may be a poor reproductive rate due to pregnancy losses, or a higher than normal rate of sickness in calves.

• Read more: BVD screening and control program in Saskatchewan

Acute infections, in which a naive animal becomes exposed, triggers an immune response. The body fights off the infection and recovers. This form of BVD is not as big a concern as persistent infections in which the animal never gets rid of the virus. PI (persistently infected) calves are the result of the dam coming into contact with a certain type of BVD virus during early pregnancy, before the fetus’ immune system is fully developed. After this fetal infection, the calf is born carrying BVD virus for the rest of its life because it cannot recognize it as foreign and does not mount an attack against it.

Acute infections can raise havoc in a herd, resulting in abortions, sick calves, poor performance such as a drop in milk production, poor weight gain, reproductive inefficiency, and lowered resistance to other diseases. But persistent infection is the silent, sneaky thief. A persistently infected (PI) animal continues to shed the virus and creates a constant source of infection for the rest of the herd.

There are tests a producer can utilize to see if cattle are harbouring BVD virus, which is particularly important for seedstock producers.

There are two kinds of tests for BVD. One looks for the virus itself. The other tests look for antibodies to the virus, to know if the animal has been exposed.

Antibody tests are useful in some circumstances but a positive antibody test just means the animal has been exposed to the virus or has been vaccinated at some point in its life.

This test proved useful as a screening tool with unvaccinated dairy calves in some studies but didn’t work as well in large-scale studies with beef calves.

“This is probably because we don’t have that many unvaccinated animals in beef herds,” says Dr. John Campbell, with the department of large animal clinical sciences at the Western College of Veterinary Medicine in Saskatoon.

“So we mainly just use this test in outbreak situations to try to figure out if the animals have been exposed to the virus. Even then it can be confusing if they were vaccinated. It can be hard to decipher whether the titer is due to vaccination or due to natural exposure.”

The ultimate test is to look for the virus, primarily to find PI animals. “Those are the ones that were infected before they were born, at a certain stage of gestation. Those calves, from the time they are born, are little virus factories, shedding more virus than acutely sick animals. In many outbreaks these PI calves may not be the only source of the virus but they can be the main source,” says Campbell.

“Usually the reason we are doing BVD testing is to try to find those PI animals and get them out of the herd. They excrete large quantities of virus, and the virus test works fairly well to find them. If you test them with the antibody test they may not have a titer, however, because their immune system doesn’t recognize the BVD virus and they may not create antibodies. They may have a slight titer to a different strain of the virus and that doesn’t help us much,” he says.

There are a couple of virus tests. The most common ones require a skin sample, which could be from the ear.

“An ear notch is easy to do, and I often use a brisket punch to get a sample from the ear,” says Campbell.

“The test used at the lab here in Saskatchewan is immunohistochemistry which is a staining test. We fix the tissue sample in formalin and then stain it with a special stain that has antibodies attached to it. The sample actually lights up under the microscope when it has the virus in it — and this makes it easy to see,” he says.

If the virus is in the skin sample, this is a good indication the animal is probably persistently infected and it’s not just a transient infection. “The transient infections don’t get high quantities of virus in the skin,” says Campbell.

Some labs use an antigen capture ELISA test. “For that one they use fresh tissue rather than fixed tissue, so you don’t put it in formalin. It’s a slightly different test, measuring the virus in a slightly different way. It doesn’t have to go under the microscope and it uses different technology,” he says.

The fresh samples can be collected (such as a skin sample from each new calf at birth), frozen and shipped in a single batch. Then the lab can do either test.

“At our lab there is some benefit in testing multiple samples at a time because it is cheaper. A number of samples can be pooled on one slide for the immunohistochemistry test. A slide costs approximately $50 so it is cheaper per sample to pool them. With the antigen capture ELISA test they put the skin sample in saline fluid and let it sit there awhile, and then analyze the fluid for the virus.” Some labs can put multiple skin samples in the same vial/fluid and test them all together. If there’s a positive, however, then they have to retest the individual samples to identify which one it is.

With the immunohistochemistry test, individual samples are identified before they are put on the slide so they don’t have to retest if one or two show up positive on that slide.

“Check with your local laboratory to see if there is a possibility of pooling the antigen capture ELISA test samples,” says Campbell.

The virus can be identified from a blood sample, but the disadvantage is that you should probably retest that animal in a week or two if it shows up positive to be sure it’s not a transient infection. “We can’t be sure that this animal is persistently infected, with just one test,” says Campbell.

With a transient infection the virus is in the blood for a short period, but if that’s when you took the sample you might think it was a PI animal.

When PI animals are found, they should be removed from the herd, before breeding season. “You don’t want animals shedding the virus when you’ve got cows in early gestation, since that’s the biggest risk. If the cows are well vaccinated, the risk is much less, but the vaccines — even though they are good — are not 100 per cent protective. That’s the main reason for testing and trying to get rid of any PI cattle,” says Campbell.

There may be a few cows in the herd that for some reason don’t mount a good immunity when vaccinated, or you miss some, or the vaccine isn’t given appropriately. If the cow jumps when you administer the vaccine and some of it doesn’t get into the cow, she may not have enough of it to be effective. And you want every cow protected.

“In a dairy herd there might be the odd cow that encounters the virus at the right stage of gestation to have the fetus affected, but there’s more risk in a beef herd where we are calving and breeding them all in a short period of time. There could be a lot of cows at that vulnerable stage of gestation, and this could create a major problem. So it’s very important to vaccinate and also have good biosecurity to make sure you don’t get BVD coming into your herd in the first place,” he says.

If you do suspect you have BVD, testing is recommended. Even if you never bring new cattle into your herd, your cows could be exposed through fenceline contact with neighbouring cattle.

“If your herd is well vaccinated the risk is less, but if you have an abortion problem or something suspicious (like a bunch of calves that are sick and not improving) or evidence of BVD on a post-mortem examination, then it’s wise to test those animals,” Campbell says.

Seedstock producers may want to test, simply to make sure that cattle they are offering for sale are free of BVD. “There is more tendency today to test and prove that yearling bulls are negative, and it’s also a good idea to test replacement heifers,” he says.

“The main thing I try to get people to understand is that we are trying to protect the fetus. If a bull or a cow gets BVD they might be sick for a few days but unless it’s a violent strain they usually recover. The main concern with BVD is to protect the fetus from infection at the wrong time, and to prevent PI calves. So we try to protect the fetus in two ways — by vaccinating the cow as close to early gestation as we can, so her immunity is high at the proper time, and trying to prevent exposure via biosecurity and maybe testing if there may have been some exposure.”

The recommendation is to test young stock, and if you get a positive, you should test the dam. “A person could spend a lot of money testing the whole herd looking for the odd older cow that is PI because that doesn’t happen very often. So we usually just suggest testing young stock, or a dead calf, and then test their dams if they turn up positive. This can save a lot of time and money,” he says.

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BRSV is suspected with pneumonias that do not respond to antibiotics or produce lots of fluids and frothing as well as runny eyes. Temperatures can be very high and these cases are often acute. In the feedlot they often appear as sudden deaths with the post-mortem diagnosis providing the final answer.

On the post-mortem the veterinarian will often find various levels of edema and emphysema throughout the entire lung. Once we see how quickly it comes on and the damage the lungs undergo it is not surprising that mortality is so high.

Usually it is more evident in the fall with the stress of weaning or during times when temperatures flit below or above freezing leading to pulmonary edema (fluid in the lungs), thus providing a great medium for the virus to grow. Stress from weather changes or poor ventilation can also bring on BRSV. Morbidity can range up to 10 per cent to 20 per cent but generally only a few cases are seen at one time.

The vast majority of our vaccination programs include BRSV as one of the key viral components, which means most calves should get an initial vaccination at two to three months of age followed by a second dose at or before weaning. This is included in the classical preconditioning shots.

Cows are often boostered annually in a viral program that also includes IBR, BVD, and PI3. As with all vaccination programs increased stress or exposure to the organism can still result in disease. Five-way vaccines also contain BRSV, so cows on this program should pass some colostral immunity off to the calves.

In these cases where the herd is previously vaccinated, especially with BRSV, I always feel there is a greater likelihood of saving the calf.

The BRSV virus is very sensitive so even though one suspects it as a cause of sickness, a veterinarian may be unable to get a positive confirmation from lab tests. Experienced veterinarians will make their diagnosis based on clinical signs, and gross autopsy findings, if they do a post-mortem. I always say to veterinarians and producers, if it acts and looks like BRSV, there is a very good chance that’s what it is.

Treatment is much more frustrating as we often see some of these cases during the cattle show season when cattle are being watched intently and producers notify us within a few hours of sickness appearing. With BRSV causing damage so quickly, you treat the symptoms with anti-inflammatory drugs to reduce the inflammation and the fever.

I have had success using antihistamines as well as diuretics to try and reduce the fluid in the lungs. Antihistamines help dry out the lungs and make breathing easier. Other than allergic reactions this may be one of the few times veterinarians prescribe antihistamines.

Getting the calves out into a fresh, cool area is also critical. This is difficult to do in dairy calf and veal barns so good ventilation is critical for prevention in housed cattle. Veterinarians will often prescribe antibiotics, as well, more because pneumonia is a definite possibility with damaged lungs.

Initially fluids may need to be given to ward off dehydration. The newer immune stimulants may be another tool your veterinarian may prescribe in the future. One must treat these cattle gently as even the stress of treatment or catching in a chute can push them over the edge. I have found with better vaccination for bacterial pneumonias and antimicrobial therapy, we vastly reduced those types of pneumonia, but the viral ones, especially BRSV, are our nemesis.

I have found that even in recovered cases there has been enough permanent damage that they may do poorly. In commercial cattle I would not recommend keeping them as replacements. Even valuable breeding stock may end up being poor breeders as they don’t grow as well and have trouble keeping weight on.

BRSV can be a costly disease both in terms of the high mortality and the chronics it can create. As with other respiratory diseases keep the vaccinations up to date. Some companies tout a one-shot BRSV but that is a moot point as you always combine it with the other viral vaccines anyway. Minimize stress and worry about ventilation in housed cattle.

I recommend that show cattle get a booster shot a week before show season with either injectable or intranasal vaccines to booster immunity to all types of respiratory disease including BRSV.

I have seen severe cases of BRSV turn around and other cases relapse in a few months resulting in mortality. This is one of the biggest reasons show cattle have lots of air blown over them to minimize heat stress and susceptibility to all types of pneumonia, but BRSV is one of the most difficult to treat.

The advent of many anti-inflammatory drugs has gone a long way to helping you and your veterinarian treat BRSV cases but prevention remains our primary goal.

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Laboratory tests confirmed malignant catarrhal fever (MCF). The only way known for cattle to get this disease is by ingesting or inhaling ovine (sheep) herpesvirus-2 (OvHV-2) shed in nasal, oral and possibly eye secretions of sheep, or the alcelaphine herpesvirus-1 shed by wildebeest found only in zoos and wildlife parks in North America.

This cow was never near wildebeest and the only time it would have been anywhere close to sheep was at livestock events.

With show season and 4-H events just around the corner, the family urges beef producers to take time to learn about MCF and discuss biosecurity measures with show organizers and at the club level.

“Sure, we know there are health risks whenever we take cattle to shows, but we have vaccinations to protect against those. There is no vaccination for MCF and no cure. That’s why biosecurity is so important — so we can happily exist with sheep and beef. For us, no ribbon, prize or amount of camaraderie is worth the risk if biosecurity isn’t in place.”

The first signs in their cow were puffy eyes and an extremely high fever of around 44 C (38.5 C is normal). As days went by, the eyes gradually turned opaque blue, ulcers developed in the mouth and nose, and swelling in the joints became noticeable. When the virus attacked the nervous system causing erratic eye twitching and loss of balance, they knew it was time to say goodbye.

These are classical signs of MCF. The word “catarrhal” refers to inflammation of mucous membranes. Watery to thickened discharge from the upper respiratory tract, salivation, laboured breathing, ulcerations on the skin and loosening or sloughing of hooves are other signs. Swollen lymph nodes throughout the body are more common in cattle than bison, while diarrhea and bloody urine are more common in bison than cattle.

The disease is usually fatal once signs begin to appear and they become more pronounced and widespread throughout the body the longer the animal survives. Many animals might look depressed for a day or two and then just die without showing any signs.

Cattle appear to have much higher levels of natural resistance to the OvHV-2 virus than bison, which experiments have shown to be 1,000 times more susceptible than cattle, according to Washington State University’s (WSU) MCF website that summarizes findings from global research and disease investigations.

Studies to date indicate many healthy cattle and bison have antibodies for OvHV-2, suggesting that they were exposed and fought off an active infection. Research is looking into the possibility of latent infections becoming active later in life.

One thing research is clear on is that the herpesvirus forms that cause MCF in susceptible animals do not make people sick.

In addition to the MCF viruses carried by sheep and wildebeest, new laboratory tests have identified four other herpesvirus types in other host species that might cause MCF in other susceptible species, one being farmed deer.

An MCF virus usually doesn’t cause disease in its host species, and susceptible species are considered dead-end hosts because they don’t shed the virus.

There is no indication that MCF spreads from bovine to bovine or to other species. The same is true for bison.

Direct face-to-face contact with sheep or with their nasal/respiratory secretions left in water sources, feed bunks, stock trailers and on other equipment are known routes of transmission.

Cool, moist conditions favour survival of the virus and increase the risk of transmission, although it’s unlikely that it would survive more than 48 hours outside the host.

Finally, MCF is not a new disease. Wildebeest-associated MCF was described in Africa some 200 years ago and research began in the early 1900s. Sheep have long been established as a universal reservoir host of the OvHV-2 virus. The first confirmed case of OvHV-2 causing MCF in farmed bison in North America was in the U.S. in 1973.

For as old as this disease is, there are still many unanswered questions. Why is it that cattle and sheep have for many years co-existed on ranches without incidence? Why are there MCF cases when carriers aren’t anywhere near? Airborne transmission over distances of up to five kilometres has been suspected based on observations such as animal density, separation distance and environmental conditions related to outbreaks in bison herds, but could vectors, such as insects, birds or rodents have a role in spreading the virus?

A WSU fact sheet suggests discoveries have been hampered by the difficulty developing a reliable laboratory test for the virus, and the sporadic, unpredictable nature of the disease. The low number of losses in cattle due to this disease also make it a low priority for research funding.

As the bison industry expanded, so too did the economic impact and the MCF research program established at WSU in collaboration with U.S. Agricultural Research Services (ARS) and other institutions in the 1990s.

Overall, research summaries suggest MCF is seriously under-reported either because it is mistaken for another disease, or not investigated because of the cost involved.

The incubation period can be long in a natural setting, maybe 200 days or more. One investigation of an outbreak that ended with 19 deaths among the 132 cattle housed in the same barn as sheep at a state fair in the U.S. reports that the number of days between exposure and clinical signs ranged from 46 to 139 days, averaging 76. Clinical signs appeared on average six days before death but ranged from one to 26 days. The report published in 2010 suggested that fair boards and veterinarians should re-examine biosecurity recommendations for livestock exhibitions.

Biosecurity

According to Alberta and Saskatchewan fact sheets most sheep in North America are assumed to be carriers of MCF, although a Saskatchewan MCF Task Force report in 2011 acknowledged the prevalence in Canadian sheep is basically unknown.

Young lambs at around two months of age start to pick up the OvHV-2 virus from older animals in the flock that are shedding. Shedding appears to be intermittent among individual animals and increases when they are under stress. It has been established that the highest risk time is when lambs are weaned around six to nine months of age and grouping them together concentrates the source.

Processing, transportation, poor nutrition or health in general, and inclement weather are other stressful times believed to be potential risk factors for shedding as well as for susceptible species to develop MCF.

Keeping those risk factors in mind, Dr. Wendy Wilkins, disease surveillance veterinarian with Saskatchewan Agriculture and a member of the Saskatchewan MCF Task Force, says the risk of transmission at shows is low but always present.

The basic biosecurity rule of thumb is to avoid contact between cattle and weaned lambs (up to 11 months of age). The state fair outbreak illustrates the need to house cattle and sheep in separate facilities, and water buckets, feed bunks and other equipment should never be shared.

In most cases, cattle and sheep can be raised together without problems provided a few basic guidelines are followed. Again, keep lambs away from cattle, don’t mix sheep and cattle during times of stress, don’t house sheep and cattle together indoors, don’t pen sheep and cattle together in crowded conditions, and don’t allow access to the same water bowls and feed bunks.

These guidelines should be applied at sales venues as well.

Wilkins adds that producer awareness of MCF is key to implementing appropriate biosecurity measures and knowing when to get your veterinarian involved, not only to confirm MCF, but to rule out foreign animal diseases with similar symptoms.

MCF is not a reportable disease in Canada, however, Alberta and Saskatchewan have made it a notifiable disease for monitoring and information purposes only.

Prairie Diagnostic Services at Saskatoon, the B.C. Animal Health Centre veterinary lab at Abbotsford, and Veterinary Diagnostics Services at Winnipeg, offer testing services, including the PCR test to detect viral DNA.

For more information, contact your local or provincial veterinarian. Saskatchewan Agriculture and Alberta Agriculture websites have brief fact sheets on MCF in cattle and/or bison. More information can also be found on the WSU Veterinary microbiology and pathology website.

The post Malignant catarrhal fever — learn about it; guard against it appeared first on Canadian Cattlemen.

Dr. Tye Perrett, a managing partner with Feedlot Health Management Services, Okotoks, Alta., oversaw the project that reviewed Canadian feedlot records on 1.4 million calves born between 2007 and 2014 to compare health outcomes of Express-Verified (EV) calves to those of non-EV calves with similar health-risk profiles.

Express-Verified calves were those born to cows and heifers vaccinated before breeding with one of the eligible Express FP products given according to label directions. Veterinarians provide a certificate of purchase to producers, who then Express-verify the calves by entering the certificate number when age verifying the calves in the Canadian Cattle Identification Agency’s (CCIA) age-verification database.

Express FP vaccines protect against respiratory and reproductive viral diseases, the main ones being BVD types 1 and 2, IBR, PI3 and BRSV. Most importantly from a calf-health perspective, the vaccines protect the fetus from internalizing the BVD virus and being born a persistently infected (PI) animal that spreads prolific amounts of the virus for as long as it lives.

The company’s Express-Verified BVD PI guarantee still stands in Canada. It will pay fair-market value plus the cost of testing for any BVD PI from a dam properly vaccinated with one of the appropriate Express FP products. The guarantee is transferable to a new owner because of the program’s tracking feature with the tie to individual animal radio-frequency identification (RFID) numbers.

Feedlot Health’s third-party review was conducted for Boehringer Ingelheim to dig for answers to questions often asked by feedlot operators. They wonder whether EV calves on the whole actually do better than calves with unknown mother-cow vaccination histories and, if so, could those non-EV calves cancel out the EV health advantage when the calves are penned together.

“We are the only company that has the ability to do this type of research and it is because of the CCIA age-verification database, Feedlot Health Management Services’ extensive database, and our Express-Verified program that gives us the ability to follow calves through to the feedlot,” says Boehringer Ingelheim Canada sales manager Lee Irvine at Red Deer, Alta.

Boehringer Ingelheim provided the RFID tag numbers for all EV calves in its database to cross reference with Feedlot Health’s database.

Perrett explains that the Feedlot Health database is a proprietary software program for collecting health and management data on individual animals to help feedlot clients manage animal health. Algorithms based on several risk factors for bovine respiratory disease (BRD) complex automatically assign a BRD-risk category at the time animals enter a feedlot. Feedlot Health’s protocols for health management are then connected to these risk categories.

The accompanying table (with bolded P values highlighting significant differences) indicates that EV calves at high risk for BRD had consistently lower pull rates (sickness), lower death loss from all causes, and lower death loss from BRD than non-EV calves in the same pen and than non-EV calves in pens without EV calves.

Express-Verified calves at low risk for BRD were less likely to get sick and less likely to die from BRD or any other cause than non-EV calves in pens without EV calves.

There were no detectable animal-health improvements in EV calves at medium risk for BRD compared to the other groups. Perrett says this could be because of greater variation in individual health risk within this category that either nullifies or makes it difficult to detect potential differences in animal-health outcomes.

The bottom line is that even though 90 per cent of the pens with EV calves had less than four per cent EV calves in the group, there were improved animal-health outcomes for the high-risk EV calves as well as their non-EV pen mates.

“From first principles, a breeding-herd vaccination program should result in healthier calves at the feedlot, but in the course of commercial trade, calves are transported and commingled with other calves of unknown breeding-herd vaccination status at the auction and/or feedlot, which can make it very difficult to observe any effect of breeding-herd vaccination on health outcomes at the feedlot, Perrett explains.

“To our knowledge, this retrospective analysis is the first to quantify statistically significant differences in animal-health outcomes at the feedlot from calves that were verified to be from cows that received pre-breeding vaccinations.”

For more information about this study contact Lee Irvine at 403-671-4878.

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Nathan Erickson, assistant professor of large animal clinical sciences at the Western College of Veterinary Medicine in Sask­atoon says it pays to discuss this with your veterinarian. “Recommendations regarding which vaccines to use and when will depend on what type of vaccination program the producer has already been on, or if the cows have been vaccinated before. Usually producers vaccinate pre-breeding or at preg-check or, less commonly, pre-calving. We are trying to develop a program that will protect the fetus that results from the upcoming breeding season,” he says.

• Read more: Calf Health: The diarrhea diaries
• Read more: Antibiotic alternatives for livestock producers
• Read more: Intranasal vaccines get around maternal antibodies

“Mainly we are interested in protecting the fetus from diseases that cause abortion but there are also some diseases that can cause malformation of the fetus or persistent infection. The BVD virus, for instance, can affect the fetus in several ways,” he says.

BVD and IBR

These two viral diseases commonly cause abortion. “We want to make sure cows have some immunity against these diseases before they are bred, to protect the fetus during the highest risk period — the first three to four months of gestation. With BVD we are trying to avoid early term abortion, fetal malformation, and development of persistently infected (PI) calves,” explains Erickson. Those PI calves may look normal, but they carry BVD virus — shedding it continually throughout their lives — and thus present a serious health risk to other cattle.

“PI calves are the result of the cow being exposed to the virus in early pregnancy, prior to development of the immune system in the fetus or while it is being developed. The immune system is self-identifying. In other words it must be able to differentiate what belongs to its own body and what is foreign (such as disease pathogens),” he explains. The immune system’s job is to recognize invaders and attack them — and only attack the foreign cells, and not their own body. There are a few auto-immune diseases in which the immune system attacks cells within its own body. A normal immune system, however, just protects the body from outside invaders.

If the BVD virus is present and circulating within the cow and her fetus during the crucial period when the fetal immune system is forming but not yet mature and functioning, it thinks this virus is part of the normal components of its body. “Because the body thinks it’s normal, it never mounts an effective attack against that virus, so the calf is persistently infected and becomes a super-shedder of BVD virus. This can cause major problems in the cow herd, and also in the feedlot if that calf goes to the feedlot, spreading the disease to other animals,” says Erickson.

“BVD causes severe immune suppression (which leaves these animals vulnerable to other diseases). In the cow-calf herd, PI calves can appear normal while shedding large numbers of virus particles — which may infect many other animals in the herd. This can cause disease in those animals and development of more PI calves when cows are in early gestation.”

Infectious bovine bhinotracheitis (IBR) is another serious disease in the cow herd, and a major cause of abortion. “It can cause abortion storms with high numbers of abortions,” says Erickson. “Typically the IBR abortions are later in gestation, such as four or five months, but occasionally we see early abortions from IBR as well as BVD. These are the two most important viral causes of abortions that we can vaccinate for,” he says. Your herd can be at risk for IBR or BVD if they have fence-line contact with other cattle that might be infected.

Bacterial diseases

There are several bacterial pathogens that can cause abortion. “There are vaccines for several species of leptospirosis, for instance. We can also vaccinate against campylobacter (vibrio),” says Erickson. Vibrio is spread by breeding, so it’s wise to vaccinate cows before going to a community pasture where they might be exposed to other cattle potentially carrying the disease.

“With vibrio, the bulls usually become shedders of that bacteria and spread it to the cows they breed. The cows become pregnant but the embryo dies early, so the cow comes back into heat. The cows eventually clear it and are able to carry a pregnancy, but that first season they come up open or calve very late. This can really destroy your calf crop for that year,” Erickson says. You want to protect your cows by vaccinating ahead of the breeding season so they will have immunity before they are bred.

“This is especially important if you are using community pastures, buying cows that may have been exposed, or buying non-virgin bulls,” says Erickson. Your herd may also be at risk if you have a neighbour who brings in cattle that might carry this disease, if any of those cattle get through the fence or your bull goes through the fence to breed one of the neighbour’s cows — and brings home the disease to your cows.

Dr. Steve Hendrick of Coaldale Veterinary Clinic, Coaldale, Alta., says vibrio and lepto are the most common bacterial diseases producers vaccinate cows for. “But we don’t recommend these vaccines to everyone. We base this on herd history, and what they have experienced with pregnancy loss, if we’ve been able to confirm this with diagnostics,” he says.

“When I was at the veterinary college in Saskatoon we developed a PCR test for vibrio. If there was a herd issue, we generally found more than one bull infected, and in those cases vaccinating the cows made good sense. If cattle are going to communal pastures for summer grazing/breeding, it also pays to vaccinate the cows.”

In a normal herd that has a 95 per cent or greater pregnancy rate year after year in a 60-day breeding season, chances of that herd having vibrio are very low. “If they are not having abortion issues with leptospirosis, and there’s not much risk for vibrio, these herds may not need to be vaccinated for these diseases,” Hendrik says.

“The combination vaccines that contain vibrio and lepto are not as protective for the vibrio portion as we’d like. The oil-adjuvanted vibrio vaccines, and even some of the killed IBR-BVD vaccines that are available with vibrio and lepto fractions, are probably more protective than modified-live vaccines with these added. Part of the reason is they have to be water-soluble, to mix up the modified-live vaccines, so they are not adjuvanted with oil. The oil acts as a carrier to create more of a depo for that vaccine (with longer-lasting effect), but they can’t do this with a modified-live product,” he says.

A person would be better off to use the separate vaccines, if they want optimum protection. “The lepto vaccine specific for Lepto hardjo might be best if a herd has an issue with chronic carriers of lepto. But you need proper diagnosis to know this.” You should be working with your veterinarian to figure out the issues and then utilize the vaccine that would provide the most protection in your herd. Even if it’s more expensive, the loss of one or two calves would more than pay for vaccine for the entire herd.

“Lepto tends to cause mid- to late-term abortions, and if you are really concerned about lepto you might consider vaccinating twice a year and not just pre-breeding. In some herds it would pay to give another vaccination at preg-check time or to check the titers of those cows. In our studies we looked at titers of cows going out in the spring and coming back in the fall. We were surprised by a number of herds that vaccinated cows in the spring and then when we measured their titers when they came off pasture in the fall they were low. The vaccine may not trigger as much of an antibody response as we would like,” Hendrick says.

Protection is short-lived, so you need to booster annually, and it may help to booster semi-annually if it’s a concern in a certain herd. With all vaccines, cattle need a primary series of injections at the proper timing, to start the immunity (usually when they are heifers) and then the annual or semi-annual vaccinations act as a booster.

Timing

Some people vaccinate cows just before they turn the bull out, or before they load the cows up to take them to pasture. “This is not ideal, but in some cases it’s most practical for the ranchers — the only time they have a chance to have cows in the corral for vaccination. This is better than not vaccinating them at all, and may be fine if it’s not their first vaccination,” says Hendrick.

“The biggest reason for vaccinating cows pre-breeding rather than at preg-check time is that we are trying to prevent disease like BVD that can cause issues all the way through pregnancy,” says Hendrick. “If this is the disease you are most concerned about, you need to make sure cows have optimal immunity before breeding so they have immunity all the way through the pregnancy,” he explains.

“IBR, on the other hand, typically causes late-term abortions. In this case, preg-check vaccination may be adequate, but we advise producers to work with their veterinarians to figure out which diseases pose the biggest risk for their own herd. Then they can determine the opportune time to vaccinate. My preference is to vaccinate pre-breeding, but I realize this doesn’t work for everyone,” says Hendrick.

“If vaccinating cows pre-breeding, we generally use modified-live vaccines that combine protection against IBR and BVD,” says Erickson. “These vaccines can be given to cows after calving and before breeding. Several different vaccine companies provide vaccines with FP (fetal protection) claims. This label claim means that if you vaccinate according to label directions, they guarantee protection against development of PI calves, and protection from IBR abortion,” says Erickson.

“These vaccines are given as an annual booster, if the cow herd has already been on a program to establish immunity. If cows have never been vaccinated, work with your veterinarian to get the herd onto an appropriate vaccination schedule (with proper boosters). The best situation is to start the immunity in heifers,” he says. They can be given their vaccinations after weaning, and a booster before they are bred the first time — with annual boosters before breeding from that point on.

Hendrick says replacement heifers should be vaccinated with modified-live vaccines at least twice, and preferably three times before their first breeding season. They can be vaccinated as calves, and again post-weaning, and the last dose about a month before breeding. This will give them a strong immunity before they become pregnant, protecting them from the viral diseases (IBR and BVD) that could result in abortion.

“If you purchase replacement heifers and don’t know what they’ve had for vaccination, you should vaccinate them several weeks before breeding, since giving them a modified-live vaccine just before breeding could be detrimental. The IBR fraction of the vaccine has been shown to cause swelling of the ovaries, which could interfere with cyclicity — and they wouldn’t be able to become pregnant until after that problem resolves. Even cows can have this problem, so we recommend giving these vaccines at least a month before breeding,” Hendrick explains.

“Cows are a bit more difficult to get onto a modified-live program if they haven’t been vaccinated before, because you need a bit more time — between calving and pre-breeding,” says Erickson. “There are some different types of vaccine that can be used, to get them onto a program (such as killed vaccines that are safer to give during pregnancy), and your veterinarian can advise you on what to use, and when,” he says. Every herd is different with regard to when it’s most feasible to vaccinate.

It’s important to give vaccines far enough ahead of breeding to build immunity before cows are bred, yet some people don’t have hands on cows until they are branding and vaccinating the calves, or the day they turn out the bulls. Some modified-live viruses may have effects on the animal which could temporarily interfere with fertility.

“It’s always best to vaccinate three or four weeks before you turn bulls out,” Erickson says. “The cows (and bulls) need time for the immune system to respond and build protection. There is some evidence that modified-live vaccines can cause temporary interruption of cyclicity in cattle in some cases. This study was done on naïve animals (that had never been vaccinated), however, and may not apply in all situations. It’s always best to vaccinate cattle several weeks before breeding, to avoid this type of problem, and also to give them more chance to respond,” he says.

“Immune response may also hinge on the condition of the cows,” says Hendrick. “If they’ve had a tough winter or spring (short on feed, or a severely cold winter), you can expect poor immunity. It’s important to focus on nutrition because this goes hand in hand with immunity. One can’t function without the other.” A cow can’t mount a very good immune response to vaccine if she’s thin and in poor condition. If a person is going to the expense and effort to vaccinate cows pre-breeding, make sure the cattle have optimum conditions to develop good immunity.

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As a result, we assumed for a long time that vaccinating calves at an early age was a complete waste of time and money as the maternal antibodies would attack any pathogens introduced in the vaccine.

Today, explained Dr. Philip Griebel in a recent talk to the University of Calgary veterinary medicine’s beef cattle conference, we know how to get around those maternal antibodies and give the calf’s immature immune system a little more protection against disease.

Griebel, a veterinarian and research fellow with the Vaccine and Infectious Disease Organization — International Vaccine Centre (VIDO-Intervac) at the University of Saskatchewan, fast-forwarded through a decade of research on calfhood vaccination strategies carried out by his team and at the University of Guelph.

The measure of immune response to a vaccine has always been increased levels of antibodies in the blood specific to the pathogens introduced by the vaccine. When scientists started looking at immune response from other angles, they discovered that even though maternal antibodies inhibit most of the modified live virus (MLV) in intramuscular (IM) vaccines, some T-cells did respond. T-cells are the first line of defence because their initial job is to recognize foreign invaders and set the chain of immune response in action. And the T-cells responded even better after a second vaccine given two to three months later.

Building on this work, others began looking at killed bacterin vaccines given during the first two months of life. With the immature immune system there was a low response, but never enough to protect the calf from a disease challenge.

“Producers would still not be getting a lot of value, so we started asking if we could deal with the problem of maternal antibody interference by changing the route of vaccine delivery to a mucosal surface,” he says. Mucosal surfaces are special epithelial surfaces in the lining of the nose, intestinal tract and reproductive tract that produce a type of antibody called IgA.

Maternal antibodies that circulate in the bloodstream are a type called IgG. One of VIDO-Intervac’s first studies showed that maternal IgG transfers very well to blood serum, but did not get across the epithelial barrier to enter the nose. The small amount of maternal IgA transferred to the calf disappeared within three days of birth because it was secreted in the mucous produced in the nose.

Use of an MLV intranasal (IN) vaccine to protect against respiratory disease failed to have any effect on circulating IgG levels, but all was not lost. Nasal secretions showed calves that received the MLV IN vaccine at birth started to produce their own IgA in nasal secretions within 10 to 12 days, whereas all of the maternal IgA disappeared from nasal secretions of calves that hadn’t received the vaccine.

“So the mucosal immune system is functional in these newborn calves,” Griebel says. “We can access it despite early high levels of maternal antibody transfer and we can get very good levels of antibody produced there. We saw that within five to six weeks after vaccination, the IgA starts to wane but a second vaccination at that time gave an even greater (IgA) antibody response.”

Maternal antibodies unpredictable

One reason is that the quantity, quality and timing of colostrum beef calves receive varies considerably. Maternal antibodies are transferred through colostrum but can only be absorbed through the calf’s gut into its bloodstream within the first hours of life. There’s no way in an everyday ranch setting to be sure of the level of maternal antibodies, the specific diseases those antibodies target, or the duration of the passive immunity.

Field trials were carried out in co-operation with a rancher from southern Sask­atchewan. The cows were vaccinated with a five-component MLV IM vaccine given three to six weeks before breeding to find out whether the levels of maternal antibodies transferred to the calves the following spring would be sufficient to block infections. Blood was drawn from 90 calves before vaccinating at branding when the calves were three to six weeks old.

Griebel says maternal antibody levels were incredibly high for BVD (bovine viral diarrhea) type 1 and type 2, very high for PI-3 (parainfluenza), but low for BHV-1 (bovine herpes virus) and BRSV (bovine respiratory syncitial virus). Testing again at weaning in October when the calves were six to seven months old showed that some had low levels of maternal antibodies against both BVD types, but upwards of 80 per cent of the calves no longer had immunity to any of the other viruses.

The level of maternal antibodies declines by about 50 per cent every three weeks. Projecting that out, Griebel calculates that if calves suckled lots of colostrum high in antibodies, the level of protection would be low by three to four months of age. Calves that didn’t receive much colostrum or colostrum with low levels of antibody could have little protection remaining by one month of age.

“So, we really don’t know when we should be starting to vaccinate,” he says.

Immune memory a powerful tool

“Using a vaccine to put in place immune memory is a very valuable way of enhancing disease protection in your herd. If we use immune memory in our vaccination program, we can get protective immunity in place within three to four days as compared to giving a vaccine for the first time, when it could take three to four weeks before protective immunity is achieved,” Griebel explains.

Results from the study of the 90 ranch calves illustrates this point. Half of them received a dose of MLV IN vaccine and the other half received a dose of water in the nose at branding. At weaning, blood samples showed that none of the calves had any remaining maternal IgG antibodies.

A week later, 20 of the calves from each group of 45 were pulled off the cows and transported to the research facility in Sask­atoon. Half of the 20 vaccinated calves received a booster with the same IN vaccine the day after they arrived and the other 10 were not revaccinated. The 20 calves that had not been vaccinated at branding were also split into two groups: 10 received their first dose of MLV IN vaccine and 10 were not vaccinated.

This gave them four study groups: never vaccinated, vaccinated only at weaning, vaccinated only at branding, and vaccinated at branding with a booster at weaning. All calves were infected four days later with a high dose of IBR (infectious bovine rhinotracheitis) virus. Fever was the measure of the onset of clinical disease and weight loss was an indicator of the severity of the infection.

The never-vaccinated calves developed high fevers within two to three days and the high fevers were sustained through day seven. Relative to the day of challenge, these calves lost almost 10 per cent of their body weight, or 40 to 45 pounds.

The calves vaccinated once at branding had lower fevers that came down sooner and they lost less weight than the calves in the never-vaccinated group, but the differences were not statistically significant.

It was the same story for the calves vaccinated once at weaning. The vaccination appeared to be of benefit, but the differences weren’t statistically significant.

Fever was completely eliminated in the calves that had been vaccinated at branding and again at weaning. These calves maintained their weight through the seven days post-weaning, despite undergoing the same stresses of abrupt weaning, transport to a new environment and diet change topped off with the disease challenge.

The twice-vaccinated calves were also the only ones with very little virus shedding. This was measured in all groups because it indicates the usefulness of a vaccine strategy in providing protection at the herd level. Sick animals shed copious amounts of virus, thereby adding to the environmental load and increasing the risk of disease transmission to herdmates. If the infection level is high enough it will overcome protection provided by vaccinating, Griebel adds.

In another IBR-challenge study, groups of calves were vaccinated once or twice with either a killed IM vaccine, MLV IM vaccine, MLV IN vaccine, or saline solution. Control calves shed more than one million virus particles per millilitre of nasal secretion for up to 10 days after infection.

The killed vaccine didn’t reduce the incidence of clinical disease (fever) nor the level of virus shedding. The MLV IM vaccine eliminated most of the clinical disease, but had very little effect on the level of shedding. The MLV IN vaccine eliminated fever and reduced shedding to 10 virus particles per millilitre of nasal secretion and there were no virus particles in the nasal secretions after six days.

The surprise finding, says Griebel, was 60 per cent of the never-vaccinated calves died of secondary bacterial pneumonias within the seven days following infection.

“This shows how important stress is because, if we take unvaccinated, weaned calves that have been in our facility for a month or two and then infect them with IBR, they get sick and recover very well. If we take abrupt-weaned calves, transport them and infect them, 60 per cent develop fatal secondary bacterial pneumonias. Management is important because a relatively severe disease can turn into a fatal disease,” he stresses.

Vaccination is important because none of the calves in any of the other groups developed a fatal pneumonia.

“All we have to do is change the site of delivery by about one foot, from the neck to the nose, and we can completely circumvent the problem of maternal antibody interference,” he says.

Options for calfhood vaccinations

Often producers think of using vaccines when it’s convenient even if handling cattle one extra time could save problems in the long run. His challenge to producers is to think about how you could integrate the vaccination program for cows with a much better vaccination program for calves to set them up for their entire lives and get immunity in place for weaning.

Consider the pros and cons of the following strategies:

1. A single MLV IN vaccine given at three to six weeks of age provided some persistence of immune memory. It significantly reduced deaths, but didn’t have much effect on clinical disease when challenged with the same viral respiratory infection at the time of weaning.
2. A MLV IN vaccination given at weaning without a primary MLV IN vaccine at branding significantly reduced clinical disease, mortality and virus shedding. From a herd health perspective, this gives the biggest bang for the buck.
3. A MLV IN vaccination at branding, boosted with the same vaccine at weaning achieved rapid onset of immunity within four days with a high level of protection during the high-stress weaning period.
4. A single MLV vaccination, whether IN or IM, given three weeks before weaning reduced post-weaning respiratory disease and, therefore, virus shedding. This protection is as strong as vaccinating at branding and again at weaning.
5. An MLV IM vaccination at branding with a booster of the same vaccine at weaning did not improve disease protection compared to a single injection of MLV vaccine for the first time at weaning. There is no significant benefit from giving a MLV IM vaccine at branding if you are going to give a MLV IM vaccination at weaning.

Quick sorting

University of Calgary veterinary researcher Dr. Philip Griebel says a common barrier to delivering vaccines at the most appropriate time is the hassle involved in sorting the calves from the cows. Here, he gives a big shout-out to his colleague in the Western College of Veterinary Medicine, animal behaviour, welfare and beef specialist Dr. Joseph Stookey, who published a YouTube video on an efficient way to very quickly get the job done without stressing animals and handlers. Stookey and his team got the idea from Alberta rancher Dylan Biggs when they were researching low-stress weaning options.

Pairs are gathered into one corral where they instinctively move to the opposite end and then turn around to wander back toward the gate, where they find an open alley leading to a second corral. Adjacent to the entrance to the alley is a panel with the bottom two bars removed so the calves can duck under and into a separate corral. A person standing at the entry to the alley controls the flow by taking a small step back to allow cows to drift into the alley or a small step forward as a calf approaches. Calves are more leery of people, so a small step toward the alley entrance is enough to send them scooting under the panel to keep them following along beside the cows in the adjoining alley.

The easiest way to find his videos on easy sorting and two-stage weaning is to search for Joseph Stookey on YouTube.

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Emergencies in the cattle business cover the spectrum of missed chances, bad choices or just bad luck. Today’s narrative should be about how industry better understands the anatomy of an emergency, about building co-ordinated response plans within and between segments, how it reassembles the pieces for recovery, and how it sustains industry infrastructure through vacuums created by an emergency (processing and trucking industries are examples). By their very nature, disease events tend to be unexpected and the variety of eventualities, limitless. Though planning and preparation for emergencies take place in artificial settings, we’re better equipped because we learn the right things.

In preparation for emergencies, the livestock industry must remain mindful of the successes and failures associated with human disease outbreaks and the crossover that often occurs between people and animals. Ongoing influenza outbreaks, the horror of the West African Ebola epidemic, and the international emergence of Zika virus, dengue fever and Chikungunya are real-life illustrations of disease emergencies and the potential gaps in both veterinary and medical infrastructure that permit them.

For the North American cattle industry, the greatest threat regionally and nationally is foot-and-mouth disease (FMD). The United States has been FMD free since 1929, Canada since 1952, yet the highly contagious disease remains endemic throughout much of the world. Recent studies by the USDA, Colorado State University, University of Warwick in the United Kingdom and Linköping University in Sweden showed that rapid implementation of movement controls at a regional level play an important role in stopping or slowing the spread of rapidly transmitted animal diseases like FMD.

Without early detection and intervention, the economic impact of FMD reaches into the billions of dollars very quickly. FMD in Canada could potentially cost $6 billion for a small, quickly contained outbreak, while losses attributable to a larger, more extensive outbreak could easily reach $45 billion. U.S. estimates place potential FMD losses at $188 billion. Even when dealing with unpredictable emergencies, a little preparation goes a long way.

Through 2014 and 2015, Canada’s cattle-feeding sector took an in-depth look at sector-wide emergencies in an attempt to formulate emergency preparedness plans that would help guide feedlot owners through potential disasters, especially those associated with disease outbreaks.

In April 2015, the Alberta Cattle Feeders’ Association reviewed and tested the plan with the goal to eventually hand it off to the National Cattle Feeders’ Association for use as a blueprint in other provinces.

The project generated draft guidelines and a workbook that producers, feedlot operators and allied industry organizations could take home, work through and systematically prepare for disease-related, sector-wide emergencies. The Lethbridge workshop reinforced that sector-wide emergencies can and do occur. Owners and operators were reminded that the cattle they control are their responsibility and they alone are accountable for their well-being. The essential constituent of managing an emergency is recovery by having tools and information in hand to minimize losses, to demonstrate due diligence and enable a faster return to normal.

The workbook consists of the following sections:

• Self-assessment.
• An overview describing how a major disease outbreak looks from a feedlot operator’s perspective along with the expectations placed on feedlot operators.
• Guidelines covering the recognition of “disease triggers” and appropriate response to unusual animal health events. Mention is made on topics like mass vaccination protocols, zoning, the challenges of mass depopulation and disposal, personal safety, and quarantine. The guidelines briefly describe the Incident Command Structure, how it works and the absolute necessity of maintaining ICS for successful organizational control and communication.
• Tools for getting prepared, training staff and organizing a register of specific information for each feedlot needed during emergencies, including feedlot objectives, farm schematics, inventory lists, contact directories, and visitor controls.
• Recovery.

Unfortunately, mass destruction and disposal, and real-time surveillance able to detect unusual disease events early in the course of an outbreak are two major components of emergency planning that remain glaring breaches, and have remained so for many years.

Early detection and rapid response to animal disease outbreaks is crucial to ensuring global security. Every hour a disease like FMD goes undetected adds an additional $3 million to control costs. A gap in surveillance capability also plagues response to human epidemics. The world wasn’t prepared for Zika to fly across continents in the span of a few months. The response to Ebola in West Africa, was built on sheer will with very little permanent scaffolding established for long-term changes to the health-care system.

The issue around a deficiency in surveillance goes back to funding priorities. Much of the funding devoted to infectious disease today is in reaction to outbreaks. With that, veterinary and human health communities are not generally prepared to respond quickly. Although we’re not stuck with what we’ve got, serious discussion between federal funding agencies and private organizations is necessary to prioritize resource spending.

Sustained disease vigilance is crucial. By aiming at the end of the epidemic, we miss the larger point. We cannot live as a world that moves from responding to one epidemic after another. Rather than thinking of beginnings and ends, we need continuous surveillance for threatening infectious diseases that are both known and yet to be discovered. We need to move from a culture of outbreak response to one that focuses on prevention. Small clusters of infectious disease cases are inevitable, but outbreaks and epidemics are preventable. (Nahid Bhadelia, Infectious Disease physician at Boston Medical Center and the director of Infection Control at National Emerging Infectious Diseases Laboratory.)

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Previously, the most common vaccines used to control the occurrence of BRD were administered either subcutaneously or intramuscularly. In a recent study, Dr. Philip Griebel, from the University of Saskatchewan, developed an effective vaccination strategy that begins early in the life of a calf and provides effective immunity against BRD before the cattle enter the feedlot.

During his research, he assessed the efficacy of both intranasal (nasal spray) and intramuscular (injected) routes using several commonly used commercial vaccines administered at branding and at weaning. The results showed that an intranasal vaccination at branding and weaning resulted in better protection from BRD compared to the same vaccine administered intramuscularly.

“The project data clearly shows that the intranasal vaccination at branding led to persisting immunity until calves were six to seven months old,” said Griebel in a release from the Alberta Livestock and Meat Agency that supported this research. A second intranasal vaccination at weaning resulted in complete protection against BRD. Meanwhile, the intramuscular vaccination at weaning did not prevent the disease.

The key is in circumventing the maternal antibodies present in calves. These antibodies, present in the animal’s blood, neutralize the intramuscular vaccines and reduce the animal’s immunity during booster follow-ups. However, the antibodies in the nasal cavity are cleared from calves within three to five days after birth, allowing the intranasal route to work more effectively.

Dr. Susan Novak, ALMA’s executive director, strategic initiatives says the use of intranasal route to administer vaccines at branding and weaning could reduce antibiotic usage at the feedlot and potentially reduce the cost of antibiotics to the cattle industry.

For more details contact Dr. Griebel at philip.griebel@usask.ca.

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Once an animal is infected, they are lifetime carriers and the disease can be spread through contact with blood, milk, and in utero.

Most positive cows show no symptoms, and are generally considered to be as productive as uninfected cows. In later stages of disease, especially if tumours begin to form, cattle experience weight loss, decreased milk production, and sudden death. Leukosis tumours are often a leading cause of carcass condemnations.

Leukosis is traditionally associated with dairy animals, but beef cattle can be affected. In 1980, a national study determined that 40 per cent of dairy and 11 per cent of beef herds were infected across Canada. More recently, a 2010 M.Sc. pro­ject from the University of Saskatchewan reported an infection rate of 12 per cent in beef cattle herds across the country.

BLV is closely related to a virus that causes adult T-cell leukemia in humans, which has resulted in a great deal of research into a possible human health risk from animals infected with BLV. Most recently, a report in PLOS ONE titled, “Exposure to Bovine Leukemia Virus is Associated with Breast Cancer: A Case-Control Study,” indicated that the frequency of BLV DNA in breast tissue cells from women with breast cancer was 30 per cent higher than the normal controls. The authors of this study do not claim that BLV causes breast cancer, or even that it is definitively a significant risk factor for breast cancer, but they do raise the possibility of using BLV as a biomarker to identify higher-risk individuals.

Many media reports have spun this as a “link” between BLV and breast cancer, which is overstating the findings. This report in PLOS ONE was a case control study and case control studies are unable to establish causation. The authors themselves state: “Validation by other investigators is essential, and a prospective study showing that viral infection preceded detectable cancer development would be desirable to support the idea of a causal association of BLV with breast cancer.”

There is no way of knowing whether the subjects were infected with the virus before or after the onset of their breast cancer. The route of exposure to BLV is not clear — both pasteurization and proper cooking inactivate the virus, which renders it harmless. A large body of previous evidence has indicated little to no risk of transmission of BLV to humans, and in fact, this research group is the only one to have suggested otherwise.

Further, the methodology used in the PLOS ONE study to detect the BLV proviral DNA, in situ polymerase chain reaction (IS-PCR), is known to generate a high rate of false positives and background amplification. A report in the British Medical Bulletin in 2011 titled, “XMRV, prostate cancer and chronic fatigue syndrome,” reviews a similar situation where an endogenous retrovirus was implicated in chronic fatigue syndrome, but these results were unable to be replicated by other research groups.

Just as correlation does not equal causation, an association does not equal a link. We can’t say that a link between BLV and breast cancer is impossible, because it is impossible to prove a negative. But until another research group using different methodology replicates these results, we can feel safe being quite skeptical of any “link.”

Karin Schmid is a Beef Production Specialist with Alberta Beef Producers and Dr. Reynold Bergen is science director at the Beef Cattle Research Council.

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