Cryptosporidiosis is the most common cause of calf scour in the UK, being responsible for 38 per cent of cases. Farmers Guardian takes a look at recent research into the topic.
While few cases of pure cryptosporidiosis result in death, it can take a calf four to six weeks to recover from the disease, which can result in weight loss or reduced weight gains.
Cryptosporidiosis is caused by a parasite called cryptosporidium and is usually seen in young calves less than six weeks old.
Symptoms include diarrhoea, dehydration, loss of appetite, fever and abdominal pain.
The diarrhoea, which is pale yellow in colour, can vary from mild to severe and can last up to two weeks.
Sarah Thomson, of the Moredun Research Institute, was funded by AHDB Beef and Lamb to carry out a PhD on the disease.
Of the four species of the cryptosporidium parasite which infect cattle, Ms Thomson found cryptosporidium parvum (C.parvum) was the most predominant species detected in calves less than six weeks of age.
Calves become infected with cryptosporidium when they ingest C.parvum oocytes (eggs).
AHDB Beef and Lamb senior livestock scientist Mary Vickers says: “These oocytes reside in bedding, pasture, soil and drinking water. They are very infectious, with only 10 oocytes required to cause disease in susceptible calves.
“Considering an infected calf can spread billions of eggs, it is easy to see why the disease spreads so quickly on-farm.”
It is not only young calves with clinical signs of the disease, such as diarrhoea, which are shedding oocytes into the environment.
Ms Thomson found infected calves at six-seven weeks old showed no clinical signs of infection, even though they were still producing oocytes.
This suggests mixing calves of different age groups should be avoided to prevent older calves infecting younger ones and causing clinical cryptosporidiosis.
Adult cattle can act as potential reservoirs for the C.parvum parasite. They also shed oocytes, but do not necessarily show any symptoms of the disease.
Ms Thomson’s study found of the 80 per cent of adult cattle infected with cryptosporidiosis, 98 per cent of cows were shedding C.parvum oocytes.
It is also important to consider that animal handlers can act as potential sources of infection, making good hygiene procedures, such as the provision of footbaths and clean clothing, important when trying to prevent spread of the disease.
Once ingested, the oocyte hatches in the gut and releases four sporozoites, which individually attach to the gut wall and multiply and develop into oocytes. These oocytes are then passed out of the calf in diarrhoea.
This multiplication results in damage to the gut which reduces an animal’s ability to digest food and leads to clinical signs seen in calves infected with cryptosporidium.
It is difficult to diagnose cryptosporidiosis by clinical signs alone because they are similar to other gastrointestinal infections.
Mrs Vickers says: “Currently, there is no vaccine available and treatment options are limited.
Infected calves should be isolated in a well-bedded pen and should remain isolated for at least one week after scouring has stopped. This should prevent the spread of eggs to other animals.
“Rehydration of calves is key for survival, therefore feeding one-two litres of oral electrolytes two-four times a day is recommended.”
The incidence of cryptosporidiosis can be reduced on-farm through good hygiene and animal management. Other preventative measures include ensuring cattle are regularly bedded down so exposure to faeces is minimised, and feed and water troughs are raised 0.75 metres (2.5ft) off the ground to minimise contamination.
Newborn calves should receive at least three litres, or 10 per cent of their bodyweight, of colostrum within two hours of birth. This will ensure the calf has a strong immune system to fight disease.