Cryptosporidiosis in Sheep: An Important Cause of Diarrhea in Young Lambs

Cryptosporidiosis is a parasitic gut disease seen often in young lambs. The culprit is Cryptosporidium, a genus of protozoan parasites that infect the gastrointestinal tract of many animal species. In sheep, infection turns up most often in the first few weeks of life and is frequently tied to neonatal diarrhea.

Lambing environments are where the disease causes most trouble, since animals and contaminated surroundings sit in close contact, which helps infection spread.

Cryptosporidium Species in Sheep

Several Cryptosporidium species have been reported in sheep. The ones identified most often are Cryptosporidium parvum, C. ubiquitum, and C. xiaoi.

C. parvum is the species most closely tied to diarrhea in neonatal lambs. It also carries zoonotic significance, meaning infected animals can pass infection to humans.

C. xiaoi is another species commonly found in sheep and goats. Unlike C. parvum, it is generally viewed as more host-associated with small ruminants. C. ubiquitum has also been reported in sheep and is known for its broad host range.

Knowing which species are involved matters when studying the epidemiology of Cryptosporidium infections in sheep flocks.

How Does the Infection Spread?

Lambs pick up infection mainly through the fecal–oral route. Cryptosporidium oocysts are shed in the feces of infected animals and can contaminate bedding, feed, drinking water, and other surfaces.

Once ingested, the oocysts release infective sporozoites in the intestine. These attach to and develop along the intestinal epithelial cells. New oocysts are then produced and passed in feces, which keeps the infection spreading.

Cryptosporidium oocysts persist well in the environment, so contaminated lambing pens and shared facilities become important sources of infection.

Clinical Signs of Cryptosporidiosis

Diarrhea is the clinical sign seen most often in affected lambs. It may come with reduced appetite, dehydration, weight loss, and poor growth.

Disease severity varies. Some lambs show mild digestive disturbances, while others develop more serious diarrhea, particularly when Cryptosporidium infection occurs alongside other intestinal pathogens.

These signs are not specific to cryptosporidiosis, so identifying the actual cause of diarrhea is an important part of veterinary investigation.

Diagnosis of Cryptosporidium Infection

Fecal samples are commonly used to diagnose cryptosporidiosis. Oocysts can be examined under a microscope using modified acid-fast staining. Antigen detection tests can also identify Cryptosporidium antigens in fecal samples.

PCR testing is used when more detailed identification is needed, particularly for distinguishing different Cryptosporidium species.

For routine veterinary investigations, fecal antigen detection offers a practical way to identify Cryptosporidium infection. The Ovine Cryptosporidium Antigen Test is designed to detect parasite antigens in sheep fecal samples using an immunochromatographic method.

References

1. Ryan, U., Fayer, R., & Xiao, L. (2014). Cryptosporidium species in humans and animals: Current understanding and research needs. Parasitology, 141(13), 1667–1685.

2. Robertson, L. J., Björkman, C., Axén, C., & Fayer, R. (2014). Cryptosporidiosis in farmed animals. In Cryptosporidium: Parasite and Disease.

3. Thomson, S., Hamilton, C. A., Hope, J. C., Katzer, F., Mabbott, N. A., Morrison, L. J., & Innes, E. A. (2017). Bovine cryptosporidiosis: Impact, host-parasite interaction and control strategies. Veterinary Research, 48, 42.

4. CDC. DPDx – Cryptosporidiosis.