Coccidiosis is a parasitic disease which primarily occurs in young cattle between three and eight months of age, but can appear from as young as four weeks, and occasionally can affect adult cattle. Coccidiosis can affect nearly all the animals in a mob to some degree, can cause deaths and does have long term impacts on productivity.

There are 13 different species of coccidia in cattle, and the parasite is present in most normal animals, causing minimal damage. Clinical disease only occurs if animals are exposed to heavy infections or if their resistance is lowered due to stress, poor nutrition, concurrent disease or heavy worm burdens. The coccidia live in the lower bowel, breed and shed oocysts (eggs) into the faeces. Infection occurs through calves eating infected pasture, feed, water, or from grooming themselves. Oocysts will be destroyed by drying and heat but can survive up to two years in moist conditions.

Infection often occurs when there is significant build-up of coccidia oocysts on paddocks and overstocking, especially in wet conditions. Another trigger for coccidiosis is the discontinuation of meal feeding. Most meals contain coccidiostats which prevent the infection becoming established, but if inadequate meal is being fed or meal feeding is stopped then infection can establish. The incubation period is 16 to 30 days and signs start with the sudden onset of diarrhoea.

The incidence and severity of the disease is often directly related to the level of stress and varies from mild to fatal. The diarrhoea contains mucus and often blood, and calves frequently strain repeatedly to try to pass faeces. Animals are unhappy and uncomfortable, are frequently off their food and are dehydrated. The acute phase of the disease lasts 5 to 6 days and if the animal survives, recovery begins at 7 to 10 days. Affected calves lose weight rapidly, and due to gut damage, regaining condition takes a long time. Convalescence typically takes many weeks and some animals will become chronically unthrifty. Mild or chronic cases can also occur, where mild diarrhoea occurs but there is no mucus or blood. There is also a high incidence of subclinical infections causing reduced feed intake and weight gain, which can often go unnoticed.

Diagnosis is usually made on clinical signs and facel samples are useful to confirm the presence of coccidia oocysts. Treatment is with Baycox or injectable Amphoprim, and is usually successful if instigated early on in the disease and, there are no underlying diseases such as BVD. Subsequent growth depends on the degree of damage sustained by the gut.

Prevention of in-contact animals is important and treating the whole group with Baycox can be useful. If the disease is in the early stages, then coccidiostats in medicated feed can be given. This needs to be fed for 28 days during periods of exposure, or timed from experience of previous outbreaks. However, removing sick calves, reducing stocking density, avoiding stress and increasing rotation frequency is often sufficient to control an outbreak.

Coccidosis appears to be on the increase and this is probably due to:

• intensive grazing of calves on the same paddocks or runoffs every year
• using medicated feed; but not feeding in sufficient quantities or for long enough
• environmental conditions have been more favourable for survival and development of coccida oocysts