Fighting the War on Coccidiosis

Everything is set up; the bedding is fresh, the feeders are in situ and the latest group of happy, healthy calves are wandering about exploring their new home. For a farmer, there are few things more satisfying. In a few short weeks though, it can start to feel like an ambush is taking place as one by one, the calves start to scour, writes Susan McKay, Companion Consultancy.
calendar icon 12 September 2012
clock icon 4 minute read
Companion Consultancy

It’s frustrating, but calves born and/or raised in indoor housing are exposed to a unique set of disease risks when compared to those kept out at pasture. With animals kept together in a more confined space, the infective agents of certain diseases can take advantage of poor hygiene and cause disease.

A common problem

Of particular concern in calves is coccidiosis, caused by the protozoal parasite, Eimeria. Commonly found in the environment, there are three main species that cause disease in cattle in the UK; E.zuerni, E.bovis and to a lesser extent E.alabamensis. Eimeria is described as ‘host specific’, meaning that a particular species of the parasite can only infect one specific host species.

The pattern of disease is one that all farmers dread; rapid spread through a group of calves. The parasite in the gut produces the infective life-stage, called oocysts, that are passed out in the animals’ faeces. These infect another calf when they are accidentally eaten and go on to develop within the gut before producing oocysts themselves.

Spotting the signs

Diarrhoea (scours), the most common clinical sign of coccidiosis, is caused by the parasite damaging the lining of the gut. The diarrhoea is profuse and foetid, often containing flecks of blood. The condition is painful, with affected calves straining and displaying signs of abdominal discomfort, such as hunching. Subclinical disease is alarmingly common though, where appetite is greatly reduced and rapid weight loss is commonly seen but with no other obvious external clinical signs. This form of disease is responsible for ‘silent’ production losses and can be very damaging to profit margins if not spotted and dealt with early.

Coccidiosis isn’t the only cause of scouring in calves, so correct diagnosis is important for effective treatment. Eimeria seems keen to dodge the blame though and can make this difficult. Oocysts are found commonly in the faeces of normal, healthy animals and the number of oocysts produced at different stages of the disease also varies considerably. Just to throw another spanner in the works, it can be difficult for anyone but a handful of experts to distinguish between the Eimeria that cause disease and those that don’t just by looking at the oocysts. Diagnosis should therefore be established by a vet through a combination of faecal oocyst counts, disease history and specialist identification of the specific Eimeria species if possible.

Stopping the spread

In order to gain the advantage against Eimeria, farmers need to know their enemy and use that to form a strategy. There are two main factors that affect the likelihood of a coccidiosis outbreak; poor immunity or a high ‘infective dose’ of oocysts.

Due to oocysts being present pretty much everywhere, some low level exposure for calves is normal and actually generates active immunity when the passive immunity received from colostrum wanes at around three weeks of age. Immunity can be compromised though when a calf is exposed to stress, even briefly. ‘Stressors’ include common management factors such as weaning, castration and mixing groups of calves. Mixing age groups is a big risk factor for outbreaks as younger calves have a much less robust immunity than older calves and infected older calves excrete oocysts in large numbers, making these young animals susceptible.

High infective doses occur either as a result of poor immunity allowing rapid multiplication of the parasite within the group or because of poor hygiene. The more faecal material there is in the environment, the more oocysts there are too. High traffic areas, such as around water troughs and feeders are particularly prone to faecal matter build up, making them prime hotspots for oocysts.

With this is mind, outbreaks of coccidiosis can be pre-empted by administering a ‘coccidiocidal’ drug such as diclazuril to susceptible animals. On some farms the same management ‘stressors’ result in the development of coccidiosis 21 days after the event (the length of the parasite lifecycle).

Treating these animals metaphylactically, 10-14 days after the stressor, can be a useful way of tackling the disease. All animals in the group should be treated to ensure that sub-clinical disease is not allowed to prevail. After treatment with a ‘coccidiocidal’ drug calves still develop immunity that will help protect them in the future and keep recurrence of disease to a minimum.

Keeping it clean

As part of on-going coccidiosis prevention, as well as helping to fight a whole host of other diseases, it is vitally important to maintain hygiene within housing areas. Regular removal of soiled bedding material and moving troughs and feeders around where possible all help to keep the infective dose of oocysts as low as possible. Housing should be emptied of all bedding and thoroughly disinfected between batches of calves.

By knowing how Eimeria spreads and using that to target coccidiosis thorough management and strategic dosing with a ‘coccidiocidal’ drug, farmers can avoid the sinking feeling that an outbreak causes and remain triumphant against Eimeria.

Further Reading

Further Reading

Find out more information on Coccidiosis by clicking here.

September 2012

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