Cryptosporidiosis is a protozoal disease, similar to coccidiosis. Protozoa are one-celled animals and most kinds are harmless. But several types cause disease and most of these are transmitted by the fecal-oral route—passed in feces of an infected animal and ingested by a susceptible animal via contaminated feed/water or when licking a dirty hair coat or suckling a dirty udder.
Various types of protozoa infect humans, sheep, or other animals, but Cryptosporidium parvum infects cattle—and can also infect humans.
Geof Smith, DVM, North Carolina State University, says stockmen need to understand that this intestinal infection is hard to prevent or treat because it’s not viral or bacterial.
“We’re probably never going to have a good vaccine, because there are almost no vaccines for protozoal diseases,” he explains.
Treatment is also challenging. “Unlike bacteria, we can’t kill these protozoa with antibiotics. We don’t have any drugs in this country that have been shown to work as an effective treatment for crypto.”
It therefore comes down to management—nutrition, hygiene and trying to minimize fecal-oral contact. The best defense against crypto is a healthy herd in good condition, in a clean environment. Herd health can be compromised by improper nutrition, so if you experience crypto you need to look at trace mineral status—especially selenium and copper, since those are crucial to a strong immune system.
“We also see problems when there’s overcrowding in a calving pasture, or snow and bad weather. If stockmen keep moving the calving cows to clean pastures (Sand Hills calving system) and have calves born in clean areas, this disease can be minimized. The later-born calves in contaminated pastures are the ones that get sick,” he says.
These protozoa don’t live in the environment forever but can live several weeks or months. After being ingested, they multiply in the calf’s intestine, causing diarrhea. Calves are generally infected during their first weeks of life.
“This is a disease of young calves, especially 1 to 3 weeks of age. It’s not something you’ll see in calves 3 or 4 months old.” This is different than coccidiosis, which takes several weeks’ incubation—you won’t see coccidiosis until a calf is at least 4 weeks old—and can affect older calves.
In a herd, there may be several calves that pick up a few oocysts—and there might be some in a fecal sample—but whether calves get sick may depend on how much they get exposed to. “This is similar to coccidiosis. It’s not uncommon for a calf to have a few oocysts; it’s when they get loaded up that we start to have problems,” says Smith.
Though crypto is often mild and self-limiting (runs its course without treatment and the animal recovers), it can be life-threatening in any human or young animal with a compromised immune system or concurrent illness. Crypto can be deadly if young calves are challenged with several pathogens at once, such as bacterial and/or viral scours along with the protozoa. Calves with severe, hard-to-treat diarrhea usually have mixed infections.
“If calves do get diarrhea, we try to keep them hydrated, and provide good supportive care. Antibiotics probably won’t be helpful.”
David Rethorst, DMV, of Beef Health Solutions, says that in order to save these calves you need to use a good electrolyte solution that’s high in bicarb content, and lots of it.
“Give 2 quarts, three to four times a day,” says Rethorst. The more often, the better. You can’t overdo the fluid/electrolytes for these calves.
Smith says suggests bringing the cow and calf in from the pasture, to have access to the calf for daily care.
“Then you don’t have to chase him around to catch him and stress him. Sometimes he’ll look better after a couple days of electrolytes and you think he’s ok and then two days later he’s gone downhill again. If you can keep him in, however, where you can stay on top of it and give electrolytes several times daily, you make better progress,” says Smith.
Try not to bring crypto to your place if you don’t have it already.
“Since it’s common in dairy calves, don’t buy dairy calves to raise on bottles or nurse cows, or to graft on beef cows that lost their calves—unless you are sure the dairy calves are healthy and have never been exposed to crypto,” Smith says.
Even if they look healthy, isolate them for five days after you bring them home, to be sure they are not incubating the disease. Then if they develop diarrhea you can clean up the isolation pen and haven’t exposed other calves.