Cryptosporidiosis is caused by a single-celled parasite (protozoa): Cryptosporidium.

These protozoa can multiply rapidly in the intestine, forming oocytes, (a type of eggs). The oocytes are excreted in the manure/faeces and thus end up in the environment. Then the oocytes undergo a few changes that make them contagious and can therefore lead to disease when admitted by other animals (or humans).  Infection usually occurs orally, (through the mouth).


Diarrhea in young calves remains one of the biggest problems on most farms during the entire rearing of calves. In addition to annoyance, this often costs extra work, treatment costs and there is serious growth reduction in the affected animal. 

In contagious calf diarrhea we often think of the Rota- and Corona virus, or the bacterium Escherichia coli (E. Coli), but also the parasite Cryptosporidium parvum. This Cryptosporidium parvum is in about 65% of cases the underlying (co)cause of (non-nutritional) diarrhea in young calves.


Cryptosporidium parvum is a single-celled parasite. So it's not a bacterium, it's not a virus. Therefore, antibiotics in these cases will NOT remedy diarrhea. 

The eggs (oocytes) of this parasite are encased in a protective layer. These eggs are located in the manure of calves and cows. The calf absorbs the eggs through the mouth, after which the parasite is released into the small intestine and enters the intestinal cells. The parasite multiplies in the intestinal cells, damaging them, greatly reducing the digestive capacity. Eventually, the parasite itself produces eggs that are excreted through the manure of the calf. The circle is now complete.



This parasite is a zoonosis, which means that people can also become infected and get sick from it. Mainly young and old people, pregnant women and people with immunodeficiency are at increased risk.


Cryptosporidium can cause diarrhea in calves from the 3rd to about 40th day of life. In practice, we see cryptosporidiosis diarrhea in calves usually between 5 and 15 days.

However, when making the diagnosis, do not limit yourself to this age.

The diagnosis can be made by confirming present oocytes (eggs) in the manure, and (immunologically), by the antigens present in the manure. Your veterinarian will take fresh manure (rectal) for examination. 


Calves without symptoms usually also excrete oocytes.

Infected calves do not always have to be visibly ill.