Although coccidiosis is widely considered to be a year-round problem on farms, research compiled by NADIS and DEFRA, and a new survey conducted by Janssen Animal Health, suggests cases may be seen more in the warmer months.
Farmer feedback has generated preliminary data from Janssen's Vecoxan Coccidiosis Survey for 2009, which shows that more than 60 per cent of cases are reported by farmers to occur in spring and summer. The Vecoxan Coccidiosis Survey for 2008 identified the same trend: 68 per cent of cases appeared in spring and summer.
Coccidiosis, caused by Eimeria parasites, is a prevalent condition and most calves will become infected. As they get older they will go on to develop immunity but those exposed to high doses of the parasites or those that are stressed in some way, can become adversely affected. Infection is often sub-clinical representing severe economic loss. The decrease in growth performance can be from 10 up to 30% without obvious clinical signs.
Nigel Underwood of Janssen Animal Health is a veterinary surgeon and feels that although the data on summer cases appears to be clear, the reality of the situation may actually be more complex.
"There are several confounding figures at work here," he said.
" Eimeria species are common and most calves will have evidence of Eimeria on eggs per gram faecal counts. Not all species are pathogenic and not in every case is there a high enough level of the pathogenic species present to say that it is the definitive cause of the disease – we really need very high epg counts to be sure of that and in some cases we must make conclusions based on the balance of probability, taking the history and disease picture into account.
"General scour is common in the summer months and the high level of reported cases may just reflect increased sampling and therefore increased identification of the disease and the parasite. In spring and summer we are also seeing spring and even autumn born calves turned out to pasture, possibly coming into contact with immune adult animals that are excreting the parasite; or becoming stressed enough by the change in environment to trigger active disease."
Janssen Animal Health is offering free tests to vets to help identify whether pathogenic species of Eimeria are present in cases of scour. According to the company, the test is not quantitative – so it is not a definitive test but it gives vets some indication as to whether "cocci" should be on the list of possible diagnoses. For details, contact a Janssen territory manager or telephone 01494 567555.
In the meantime farmers are advised to be on the look out, particularly for the sub-clinical form of the disease which causes reduced growth, a poor dry coat and loss of appetite. This form is hard to identify and causes the greatest economic losses.
Cocci can also present as scour, weakness, anaemia and even death. Ensuring adequate colostrum intake, hygiene around food and water troughs and avoiding over crowding can all help reduce the incidence of active infections.