The incidence of “crypto” diarrhea is most definitely higher on dairy farms where calves are raised in close confinement and the wet moist environment is conducive to the transmission of these protozoa. We as large-animal veterinarians are detecting it more often in our beef herds out west. “Crypto” is a protozoa with a very similar life cycle to coccidia which is probably much more familiar to Canadian cattlemen. The detection can at times be difficult to establish but with newer tests and other methods described in this article look for it and you may find it even in well-managed cattle operations.
Dairymen watch for it diligently and you as beef producers should discuss it with your veterinarian and be especially vigilant if scours crops up in older calves that seem unresponsive to traditional scour treatments. Bringing in dairy calves to be adopted onto beef cows can be a source of infection. I always suggest clients should use calves from their own herds if possible.
Crypto is usually caused by the species C. Parvum in cattle and it is also zoonotic meaning it’s transmissible to humans. So, as a general rule, be cautious when handling diarrheic calves. Be extra vigilant cleaning and disinfecting areas where sick calves are gathered. Most human cases involving producers, farm workers, and veterinary students result from exposure to sick calves. As with all zoonotic diseases people under stress or immunosuppressed are highly susceptible. Be sure to clean boots, coveralls and wash your hands thoroughly especially after dealing with diarrheic calves. As a precaution treat the diarrheic calves last to avoid carrying the oocysts between calves.
The organism is very similar to coccidia in the sense oocysts (eggs) are passed in the manure in very large numbers (up to 10 million per gram of manure). Oocysts are ingested by the calf and in completing their life cycle can damage the large intestine and the end of the small intestine. We see it primarily in calves anywhere from three to 30 days of age. The clue is calves that seem unresponsive to treatment. The diarrhea generally appears yellow and sort of foamy. The organism destroys the inner lining of the intestine so the milk comes through essentially undigested and calves dehydrate.
Keep in mind half the time crypto is involved in mixed infections with other scour organisms so you may be dealing with essentially two diseases at the same time. That is why you must follow all the preventative steps in your power to avoid a scours outbreak. These are the tools I have talked about in past articles, new calving areas, lots of room and bedding, good nutrition for the dam prior to calving to produce high-quality colostrums. Make sure the calves are up and sucking within a couple hours and if in doubt supplement with home stored frozen colostrum or a good substitute such as Headstart.
Vaccinate your cows and heifers for scours but keep in mind good vaccines cover the most common causes of viral and bacterial scours in calves but not the protozoan type, coccidia and cryptosporidiosis.
One of the real issues in the past has been the initial diagnosis. Crypto was always hard to prove. Fecal samples can be taken and labs are getting better at spotting it but the oocysts are much smaller than worm eggs so they can be hard to see. Now there is a check strip called Eentericheck from Biovet Labs that you insert into the manure, which is a fairly sensitive and specific. We recently learned from U of Calgary veterinary student Dayna Goldsmith who was attending our clinic on a rotation that crypto is what they call an acid-fast organism. This means it takes up acid-fast stain so another way to test for this organism is to smear a sample of the manure on a microscope slide, stain it, and like magic the oocysts appear when they take up the stain. At our clinic we’ve learned you can be very confident of this diagnosis.
The next real issue with crypto has been the treatment, or should I say lack of treatment options. Standard treatments such as electrolytes are always warranted. Vets would prescribe sulfa drugs similar to a coccidiosis treatment, but the best solution is to cut down on the number of organisms being excreted.
Merck Animal Health has just had a product called Halocur licensed for this very thing. It’s been used in Canada for a few years under an experimental drug release so it has a successful track record. In outbreaks or after a first case is diagnosed subsequent calves are put on it for seven days in a row. It controls the crypto by breaking its life cycle and substantially reducing the number of oocysts that can reinfect the calf or other calves.
Halocur is given orally at a rate of two cc per 10 kg daily. It is very important that you give the proper dose with Halocur. Unlike most products the safety margin with this one is quite low. At twice the normal dose you could get depressed calves, blood in the diarrhea and other signs very similar to the disease itself. So don’t give more medication if those signs show up. At four times the normal dose it can be fatal. Always treat the calves on a full stomach and don’t treat calves that are already sick.
There are other coccidiostats, which have been tried against cryptosporidiosis on an experimental basis. Halocur was developed as a coccidiostat for chickens but resistance developed.
Isolation of sick calves is another necessary step to any treatment protocol for crypto combined with regular cleaning and disinfection of the isolation area. The oocysts are very resistant, although high temperatures will kill them. The key with this disease is to reduce the number of oocysts in the environment around these young calves. As they become older the calves will develop resistance to this organism.
If you see unusual diarrhea with a frothy content that looks like undigested milk, don’t delay. Call your veterinarian to rule out cryptosporidiosis. C