General information

Cryptosporidia are very small, unicellular parasites of the gastrointestinal tract. They are classified as coccidia. Different species are described with very similar morphology. Some of these are host-specific; others (e.g. Cryptosporidium parvum) can infect various animal species and humans (zoonosis).

Infections occur after intake of sporulated oocysts. The infectious dose is very low (approx. 100 oocysts). Subsequently the liberated sporozoites infect the intestinal epithelial cells, followed by a development cycle over trophozoites, meronts, merozoites, gamonts, zygotes and in the end again oocysts are formed. The oocysts excreted in the faeces show a high tenacity, are resistant to many disinfectants and can remain infectious for months. Therefore, e.g. contaminated pens or terrariums are frequent sources of infection.   

In cattle cryptosporidia is a very common endoparasite. A large proportion of calves go through an infection with C. parvum. Clinically apparent courses with enteritis and diarrhoea occur especially in calves up to 3 weeks of life, often related to co-infections. Not infrequently lambs, piglets and foals are affected.

A much lower prevalence is seen in dogs and cats, with usually asymptomatic infections. However, oocysts are excreted in the faeces here too for about 2 weeks. Manifest infections can be seen in puppies or immunosuppressed animals (e.g. FeLV, FIV, distemper, neoplasia etc.).

In reptiles, cryptosporidia is a serious pathogen that can cause severe losses, especially in snake and lizard stocks. C. serpentis is an important parasite in snakes and infects the gastric mucosa. Due to the chronic inflammation a subsequent swelling and hardening of the connective tissue in the gastric area can occur. Typical symptom is regurgitation of food days after digestion. C. saurophilum (also called C. varanii) however destroys the lining of the intestinal walls of affected lizards and snakes. Clinically malabsorption with excretion of undigested food, profound weight and fluid loss is observed. Both pathogens are not pathogenic to humans.  Quite often, C. muris and C. parvum is found as passers in reptile faeces (origin: infected food animals). Therefore a differentiation is absolutely necessary by a positive Cryptosporidia result.

Laboratory diagnostically several methods are available for detection. Already during the microscopic examination after specific enrichment (MIFC) oocysts can be found.  Like all parasitological faecal examinations, the sensitivity here is relatively limited by around 60%.

In cattle, ELISA testing (detects C. parvum) is recommended. The immunofluorescence test includes a wider range of Cryptosporidium species and is therefore suitable for dogs, cats, but also small rodents (guinea pig: C. wrairi).

Reptile faecal samples are additionally stained (modified Ziehl-Nielsen) to increase the detection rate upon microscopic examination. In reptiles, one cannot distinguish between pathogen strings or passers by positive IFAT results. Here PCR testing is recommended with subsequent differentiation.

It should be noted that a single negative result does not completely rule out a Cryptosporidia infection, as the pathogen can be excreted intermittently. Symptomatic therapy and hygiene management are the best options in the fight against Cryptosporidium.