These information sheets are provided for your interest. They should not replace veterinary advice from your veterinary surgeon.

Whilst every effort is taken to ensure the accuracy and completeness of the information provided at the time of writing, your specific circumstances must be discussed before advice can be given.


Cryptosporidiosis is most commonly caused by the small protozoan parasite Cryptosporidium parvum. This is transferred either faecal-orally or through a contaminated water supply. It infects the epithelial lining of the digestive tract where it reproduces and oocysts are shed in the faeces after about a week (pre-patent period). Cryptosporidiosis is zoonotic and can infect many other species as well as calves, such as lambs, pigs and foals.

Clinical Signs

  • Diarrhoea – unresponsive to treatment and lasting longer than would be expected with viral (Rotavirus, Coronavirus) or bacterial (E. Coli) causes
  • Dehydration
  • Weight loss
  • Can be very severe and lead to death in young calves or be asymptomatic in adult animals


  • Faecal samples – oocysts can be detected in faeces using light microscopy or by faecal flotation techniques (more sensitive, 83%).
  • Post mortem examination – Sometimes intestinal lesions may be seen if the calf has had chronic diarrhoea for a long period of time.


Support calves with fluids/electrolytes.

Continue to provide calves with milk to reduce energy deficits.

Good hygiene and management is vital in limiting transmission: clean, dry bedding; ensuring adequate colostrum intake; not mixing calves of different ages; and ideally conducting an all in/all out system with thorough cleaning between batches.

Halocur (halofuginone lactate) is licensed for prevention and treatment for cryptosporidiosis in calves. This is given orally with feed once a day for seven consecutive days. Once one calf is treated all newborn calves should be treated to prevent infection from the environment.