Clostridia are sneaky bacteria. They have the ability to form a protective waxy covering in a dormant stage, morphing into spores in reaction to adverse conditions such as drought. In this state they can survive in the soil almost indefinitely just waiting to be eaten or rubbed into an open wound by unfortunate cattle.
Spores can also linger inside the gut in a latent state just waiting for the right conditions to spring to life producing toxins that can kill when they get into the bloodstream. Since most of these bacteria are ever-present in the environment and cattle are always exposed to them the only way to protect cattle is by vaccination.
Blackleg is probably the most prevalent, says John Campbell, head of Large Animal Clinical Sciences at the Western College of Veterinary Medicine in Saskatoon. The bacterial spores are everywhere. Clostridial diseases occur most often in young, unvaccinated cattle, he says. Older animals may have been exposed earlier in life (with low levels of bacteria) and developed resistance.
There are certain geographic regions where redwater is very common, says Campbell. In regions with liver flukes, stockmen may have to vaccinate for redwater twice a year. Flukes damage the liver, enabling bacteria to gain entrance to these tissues.
Blackleg and malignant edema are very similar and we see these diseases quite often unless cattle are vaccinated, says Campbell. There are 7-and 8-way vaccines combining protection against most of these diseases, including blackleg, redwater, malignant edema, black disease, enteroxemia (gut infection caused by C. perfringens types andD).
There is one 8-way vaccine here in Canada, a Schering-Plough product, that includes tetanus, says Campbell. All clostridial diseases can be deadly, but they are also unique in that they can be very effectively prevented by vaccination.
Dr. Steve Hendrick of WCVM says clostridial diseases aren t contagious in the usual sense. We are used to diseases where one animal gets sick and can pass the disease directly to another. This is not the case with clostridial diseases. They are caused by spores that live happily in the environment for many years. The spores are resistant to heat, cold and any other harsh environmental conditions. We joke that these diseases are very happy, even living in the cold weather of Saskatchewan, he says.
It just depends on whether or not the environment on your farm or ranch has been contaminated in the past.
In wet conditions we see more cases, so clostridial diseases could potentially be a serious issue this year, says Hendrick. Dormant spores are brought up to the surface with the moisture where they float on top of the puddles and gradually concentrate on the surface as the puddles dry up.
As cattle graze in low areas, or drink from shrinking puddles, they may pick up spores, explains Hendrick.
With these diseases, you usually don t see sick animals. You generally go out to the pasture and find one or two animals dead. Some are brought in for treatment, but usually they die so quickly that you just find them dead.
Clinical signs, such as swelling in a muscle (typical of blackleg), particularly if there is no wound may be diffi cult to notice.
The animal ingested the spores, which eventually end up in the muscles. It s usually a very fast-growing calf (one of your best animals) that s affected. If the muscles don t get enough oxygen, the spores proliferate in the muscle. Bruised tissue creates ideal conditions for spores to grow, says Hendrick.
Many of the cattle we ve looked at that died from blackleg also had infection around the lining of the heart, says Campbell. It can affect the muscle around the heart.
One of the first cattle vaccines was created for blackleg. Some of the clostridial vaccines have been developed in different countries, where there are different disease conditions. The big difference is the inclusion of tetanus in some of the combination vaccines. Producers here should be aware that tetanus is not included in all clostridial vaccines in North America, says Hendrick. The single tetanus vaccines are only used in horses, and are expensive.
We ve seen outbreaks of tetanus when people are banding bull calves at weaning time or when coming into a feedlot, says Campbell. We don t see it so much in baby calves, but more in the larger calves. For these big calves, many people use banders. All clostridial organisms thrive in an anaerobic environment (without oxygen). The clamp against the testicles provides a perfect place for bacteria to grow. We ve seen producers do this and get away without using tetanus vaccine year after year, and all of a sudden one year they have a large number of banded cattle develop tetanus a few weeks later, he says.
There are many clostridial diseases. People might be aware of botulism or tetanus because humans get these. Unfortunately, we don t have a cattle vaccine for botulism in Canada. But we can protect cattle against tetanus, blackleg, gas gangrene, malignant edema, etc. Some of those spores can get into the body through a wound, if it is contaminated with soil, says Hendrick.
In other instances the animal ingests spores with feed and the spores get into the liver or muscles. Many people don t realize that redwater disease starts with liver damage. In an area that has liver flukes, cattle are at risk for redwater. The difference between a 7-way and an 8-way vaccine is the inclusion of redwater, he explains.
Calves are at risk for gut infection from Clostridium perfringens. These clostridia can cause intestinal damage and severe hemorrhagic diarrhea, he says. Calves may die suddenly if the gut damage allows bacterial toxins to seep through into the bloodstream. The animal quickly goes into shock and dies within a few hours. It s often the biggest, fastest-growing calves that suddenly develop gut infection, often called enterotoxemia by ranchers.
Most cattle have clostridium perfringens in the GI tract. There are several different types, such as A, B, and D. It s common to find some of these types in the GI tract, without disease. This makes it more difficult to accurately diagnose a problem, but typically when a calf dies from this kind of infection there is very severe hemorrhagic enteritis with bloody diarrhea due to extreme gut damage. The animal may die so quickly, however, that there is no evidence of diarrhea.
The clinical signs may be severe gut pain (the calf kicking at its belly or throwing itself on the ground) and then the calf goes into shock and dies. The bacteria are normally found in the gut, and spores are passed in feces. If cows are passing some of the spores, they may pass even more when stressed at calving time. Depending on the ranch management, there may be more exposure for calves, says Hendrick.
Certain conditions within the gut also make a calf more likely to have a problem, such as when a calf has been off feed awhile and then loads up on a large amount of milk. This creates an ideal environment for certain types of
C. perfringens to proliferate.
Prevention is crucial. The vaccine is relatively inexpensive probably the cheapest one and works very well, compared to some of the other vaccines. Efficacy of clostridial vaccines (even though they have multiple components) is great, giving good protection as compared with some of the respiratory vaccines, says Hendrick.
Clostridial vaccines have been in use for many years and have dramatically cut down the incidence of these diseases, says Campbell. I still see some cases, on farms where people try to save money and didn t vaccinate. The disaster that can happen especially with blackleg can be tremendous. One farmer lost about half his calf crop to blackleg, dying at pasture, says Campbell.
There is no reason to not vaccinate for clostridial diseases. It is an irritating vaccine, however, so you want to give it under the skin and not into the muscle, says Campbell. Some animals react more adversely than others, developing swelling at the site. The vaccine companies are working on trying to make these vaccines less irritating, he says.
One challenge for people who calve on pasture later in the year is that they have to round up the calves at some point to vaccinate and make sure they get their first clostridial vaccine. In the more traditional setting, where ranchers calve in March and April, they gather and vaccinate cattle before they are turned out to summer pasture. It s more challenging for people who calve later, out on summer pasture, to vaccinate calves at one or twomonths of age, he says.
In other aspects of prevention, I try to promote proper disposal of the carcass when an animal dies, says Hendrick. This topic came to the forefront with anthrax, when people started asking what to do with dead animals. The clostridial diseases are no different. If you leave the carcass for scavengers to scatter, you are creating the same scenario as you would with anthrax. The bacteria create spores and contaminate the surrounding environment. These may create problems later maybe not the next year, but possibly sometime in the future. The spores last forever, and may affect cattle many years from now, he explains.
Everyone got worried about anthrax, and I ve been amazed at the extent people will go to, burning carcasses and burying them which is good. Yet if they find a dead calf and assume it was blackleg, they don t seem to worry about it. They need to realize that these carcasses should also be properly disposed of, he says.
The disaster that can happen especially with blackleg can be tremendous