Control of calf scour – is it possible?

Adult carrier cattle are the main source of infection of cryptosporidiosis and can shed small quantities of oocysts in their faeces without showing any clinical signs. These oocysts can easily infect the new born calf during or directly after calving via the faecal-oral route. Once ingested, the parasite rapidly multiplies, damaging the cells of the small intestine. Shedding from the calf can start within four days of initial infection leading to rapid re-infection of the calf as well as other calves within the same environment. This in turn can lead to massive environmental contamination within a short period of time. Disease can occur anywhere from one to four weeks age. However, calves from seven to thirteen days old are most commonly affected.

Herds infected with a pure cryptosporidiosis infection generally have a high morbidity and low mortality. However, as most herds in Ireland typically have a concurrent infection with rotavirus for example, this in turn can result in higher mortalities. Clinical signs initially include a reduction in appetite and apathy without scour. This can progress to a mild to moderate diarrhoea over several days which is unresponsive to usual therapies. Concurrent infections can lead to a more severe dehydration, emaciation and death.

Diagnosis

Diagnosis forms an important part of differentiating the infection from other enteric pathogens such as rotavirus, salmonellae, E. coli and corona virus, as treatment and control methods can be slightly different. On-site kits can be a convenient diagnostic tool and can give a result within minutes otherwise samples can be sent to a suitable laboratory for analysis. To do so, sample faecal content directly from a group of at least 5 affected calves and ideally, samples should be taken from twelve-day old calves.

Treatment

Once cryptosporidiosis has been confirmed on farm, ensure all affected calves are isolated as quickly as possible to limit further infection. Symptomatic treatment including rehydration fluids should be administered to combat dehydration. Halofuginone lactate reduces diarrhoea cases due to diagnosed cryptosporidiosis infection. Halofuginone lactate suppresses the parasite instead of killing it and as a result does not interfere with host immunity. It also causes a marked decrease in faecal oocyst shedding thereby limiting further environmental contamination.

To prevent further infection of calves on farm after a positive diagnosis with cryptosporidiosis, halofuginone lactate can be used on all new-borns and should be started within the first 24-48 hours. It is not recommended to administer halofuginone lactate, on its own, on an empty stomach or to cases where diarrhoea has been present for more than 24 hours and should be given after feeding. For treatment of anorexic calves, halofuginone lactate should be administered in half a litre of electrolyte solution.

 Control

• All new born calves MUST get at least 3 L of colostrum within 2 hours of birth.
• Healthy calves must be separated from sick calves and a “hospitalisation” unit established for the sick calves.
• Healthy calves should be fed first each day and hospitalised calves attended to last so as not to transfer disease from the sick animals to the healthy unit.
• Designated overalls and boots should be worn when working in the hospital unit and hands should always be washed between each group of calves.
• Strict, thorough hygiene of feeding equipment including bottles, nipples and buckets must be practised.
• Raise feed and water troughs so that calves can eat and drink out of them but cannot defaecate into them.
• Antibiotics are NOT effective against cryptosporidiosis. All calves clinically affected should be treated with a product licensed to reduce diarrhoea due to Cryptosporidium parvum. There is a product containing halofuginone lactate that is licensed for this purpose and administration should start within 24 hours after the onset of diarrhoea and continue daily for 7 days.