The Nadis data show that the number of cases of coccidiosis is at its lowest in late winter, and then rises during the spring to peak in June and July. This peak is followed by a slight,short-lived fall in late summer, and then another rise to a peak in November.
Coccidiosis is caused by single-celled parasites (not bacteria) known as coccidia. There are several species in cattle, not all of which cause disease. The species that cause disease are primarily found in the large intestine, and the diarrhoea results from damage to the cells lining it.
Coccidiosis is seen in animals up to two years old, and is particularly common in calves between three weeks and six months of age. Cattle become infected when placed in environments contaminated by older cattle or other infected calves. This can happen either indoors on bedding, or outdoors around drinking or feeding troughs. In order for the coccidial oocysts (the egg stage of the parasite) to become infective they require warmth and moisture. It is probably the lack of moisture in late summer and the low temperatures in late winter that result in the low level of coccidiosis during these times, however coccidiosis can be a significant problem at any time of year.
The most common sign is a watery diarrhoea, which because the coccidia damage the large intestine is often accompanied by straining (which can become very severe), mucous and blood. Other signs can include depression, loss of appetite, weight loss, and, much more rarely than with diarrhoea in milk-fed calves, dehydration. Death is rare. Infections that fail to produce diarrhoea can, nevertheless, result in reduced growth and weight gain. This sub-clinical infection is very common, with up to 95% of cases being of this type.
To achieve effective control of coccidia, good management and hygiene is vital. This should include: