By Dr Zoe Vogels
Coccidiosis is a protozoal infection of calves and heifers that can cause diarrhoea (scouring) and poor weight gain.
As seen in the diagram below, calves become infected by ingestion of the “egg” or oocyst of coccidia from the pasture. Once infected, the parasite multiplies in the intestine of the calf damaging the lining of the bowel. Coccidia is then shed in faeces of clinically affected calves, contaminating the environment further.
Coccidia oocysts are extremely resistant to drying out in the environment and can even survive for up to 2 years in moist, cool conditions. They can persist in a farm’s calf rearing paddocks from season to season.
Signs of coccidiosis occur 5–20 days after exposure and are generally seen in calves 3 weeks and older: often in mobs of calves which are moved from a shed at weaning time, into a paddock with reasonably high levels of contamination.
Clinical signs may include passing fresh blood or blood-stained faeces and straining. The scour is often smudged around the rear end and around the hocks. A form of the disease in which the calf shows nervous signs is seen on rare occasions. Few animals die from the disease but calves that have had coccidiosis can take some time to regain losses in body condition.
Prevention: increase immunity, decrease exposure
Severity of disease is a balance between infective load and the immune system’s ability to fight off infection – stress such as cold, wet, windy weather – can precipitate disease. Ensure calves receive adequate nutrition, are provided with shelter from the elements and have an effective worm control program.
Reducing stocking rates or changing calf paddocks will reduce exposure from grazed grass. Feed and water troughs should be raised to reduce faecal contamination.
Lasalocid and Monensin can help prevent the signs of coccidiosis and heifer starter mixes (either pellets or muesli mixes) should contain one of these products. However, it is important to be aware that calves need to be eating adequate amounts of starter for them to be effective. Ensure that the starter has less than 5% fines to ensure palatability and ensure adequate access.
There are several other diseases of calves and heifers that can cause similar clinical signs, such as the bacteria Salmonella and Yersinia, intestinal worms, Pestivirus and grain overload. Correct diagnosis to confirm coccidia and rule other diseases in or out will enable prescription of the most suitable products for treatment of sick calves and prevention in other calves.
Diagnosis is through detection of coccidia eggs in faeces under the microscope. The Vet Group supply kits with instructions so that you can collect faecal samples to send off for diagnostics.