Intervet/Schering-Plough Animal Health has released diagnostic data which the company says indicates that calf scour problems caused by cryptosporidia are on the increase.

A summary of 2010 results from the company's ScourCheck scheme, which identifies infectious scour pathogens in calf faeces, show the protozoan parasite Cryptosporidium parvum being present in 37% of samples.

Intervet/Schering-Plough ruminant veterinary adviser Drew McGurren said: "Ever since we started testing calf faecal samples in the 1990s, rotavirus and cryptosporidia have always been identified as the two main pathogens implicated in infectious scour problems. But the latest data - and feedback from vets in practice - suggest cryptosporidia incidence is on an upward trend.

"Ten years ago our top line reporting used to refer to rotavirus being implicated in around a third of all infectious calf scour problems and cryptosporidia in roughly a quarter. But in 2009, we detected cryptosporidia in 30% of samples. And this year - from the 250 plus faecal samples we have looked at so far - the incidence seems to be even higher."

Drew stressed that scours caused by cryptosporidia are not always confined to housed calves: "Suckler calves between one and two weeks of age can be very susceptible to infection at grass, particularly if conditions underfoot are muddy around ring feeders. Early May has seen quite a lot of rain, and the parasite thrives in damp conditions."

The major source of cryptosporidia is thought to be either adult cows (which act as carriers without showing signs of disease) or infected scouring calves passing the parasite in their faeces. Drew said: "The infectious dose of the organism is very low and if ring feeders are not moved regularly the disease threat that builds up can be very similar to the housed situation. Faecal contamination of feed and water troughs can also be reduced by raising and covering them.

"Cryptosporidiosis in calves is often seen in combination with other diseases, particularly rotavirus. So vaccinating cows against rotavirus with Rotavec-Corona one to three months pre-calving - as well as a sound colostrum feeding regime and maintaining high hygiene standards - can often tip the balance in your favour."

Intervet Schering-Plough says that if cryptosporidia is diagnosed as the problem, parasite replication and excretion can be reduced with Halocur. This is the only product licensed to treat and prevent cryptosporidiosis. Administered orally to calves after feeding (daily for seven days), it can reduce the severity of diarrhoea and prevent the infection spreading to other calves. Treated calves have also been shown to require fewer antibiotic and anti-inflammatory treatments, as well as less rehydration therapy.

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