Silent killers:  Coccidiosis

Coccidiosis (Eimeria) is a parasitic disease, caused by coccidia, single-celled organisms (protozoa), which live and reproduce in animal cells.  The disease can cause gastrointestinal infections across species, but the parasites which cause it are host-specific so that the pathogenetic (disease-causing) coccidia that affect calves will not affect lambs. 

Across species Coccidiosis is one of the most widespread and costly diseases.  While mortality rates from the disease are not high, it does cause significant gut damage leading to production losses.  Coccidia are very common in the environment and when they are ingested, they invade the intestinal lining and can lead to severe diarrhoea and weight loss.

In sheep

Almost all lambs will become infected with coccidia in early life – and with one or more species.  However most of the species found in sheep are harmless and it is only two pathogenic species (Eimeria ovinoidalis and Eimeria crandallis) that cause clinical disease when there is either a heavy infestation in lambs or if they have lowered immunity.

Lambs take in the coccidia oocysts (eggs) by mouth and these then multiply dramatically in the gut cells, resulting in many million more eggs being shed in faeces than were originally ingested.  Clinical signs of disease are most often seen in lambs aged four to eight weeks old and Coccidiosis is not common in animals over three months old unless they are debilitated (although ewes shed low numbers of oocysts which can initiate infection).  The infection causes diarrhoea, often accompanied by straining, pain and weight loss and, sometimes, the death of the lamb.  Post clinical infection, older lambs may continue to show poor growth rates as the gut has a reduced ability to absorb nutrients from food.

Whilst clinical signs can be highly suggestive of Coccidiosis, the disease should be confirmed by testing.  However, the usual oocyst count will not identify the different species contained within the sample.  To establish the presence of pathogenic oocysts, an additional speciation test is available which can help with diagnosis and treatment decisions.

There are three licensed ingredients available for treating or preventing Coccidiosis in sheep and these include in-feed medications and oral drenches.  Lambs with severe diarrhoea and dehydration will also need oral electrolyte solutions and nursing care.

Preventative measurements are good biosecurity, hygiene and management plus timed and targeted preventative treatment.  It is important to remember that there is no cross protection of immunity to different species of coccidia so maintaining a closed flock or following strict isolation and quarantine measures can reduce the risk of new animals bringing in a species new to the flock.

On grazing land, contamination levels can be reduced by regularly moving to clean grazing and avoiding fields that carried young lambs in the previous season.  Creep feeders should be moved daily onto fresh ground to avoid the areas around them becoming heavily contaminated.  And lambs with ewes at lower stocking densities carry much lower risk.

In goats

Wild goats rarely suffer from coccidiosis as they’re browsers and feed over large areas and infection is more commonly seen in intensively reared animals in young growing kids, with kids between one and six months being most commonly affected. In a survey conducted in the UK, four to eight week old kids were the most likely to be affected and four week old kids were the most vulnerable to clinical disease. Many disease outbreaks occur shortly after weaning, as this is a very stressful period in the kid’s life. Bad weather may also trigger disease outbreaks.

Two species of coccidia affect goats - E. ninakohlyakimovae and E. caprina.  If infected, kids begin to lose their appetite and become weak and lose weight. They may become anaemic and strain to pass faeces. As the disease condition worsens, affected kids may experience severe diarrhoea, with streaks of blood, followed by severe dehydration and death.

There are no products licensed for use in goats although a veterinary surgeon may advise the use of products licensed for use in sheep as anti-coccidals.

In cattle

In cattle, there are three parasites which are the most common and pathogenic :  Eimeria zuernii, Emeria bovis and Emeria alabamensis.  Disease outbreaks are most commonly seen in calves of three to four weeks of age, after mixing groups of recently-weaned dairy calves.  For young spring-born calves at pasture during summer, contaminated watercourses are a major risk.

With cattle, the main clinical indicators are chronic wasting and poor appetite.  More severe clinical signs are profuse sudden onset diarrhoea containing mucus and flecks of fresh blood.  Straining with partial eversion of the rectum may occur in severe cases, but affected animals will not have an elevated rectal temperature.  Loss of animals to the disease is rare, but morbidity is high with a long convalescence period leading to financial losses due to poor weight gains.

Veterinary diagnosis of Coccidiosis in cattle is based on typical findings affecting a large number of calves in the group.  As with sheep, faecal samples must be speciated to determine whether any coccidia present are pathogenic and, due to cost, these are rarely undertaken in field outbreaks.  Treatment will depend on individual situations but it is important to move calves from infected pastures immediately. 

In pigs

While scouring in piglets can be caused by a number of factors, Coccidiosis is probably the most common cause of scour when they are aged between 10 and 20 days.

Coccidiosis in pigs is caused by the parasite Isapora suis and other coccidia of the Emeria species are generally thought to be harmless in piglets, although in rare cases they can cause disease in young adults.

In pigs, oocysts shed from one animal into the environment will undergo a temperature-dependant maturation process before they go on to infect other animals orally.  The organism then colonises the small intestine causing gut damage leading to scour.  While a reservoir of infection may exist in adults, infection of piglets is most commonly from an environment which remains contaminated from a previous litter.  The disease can occur in both indoor and outdoor systems – outdoors either in summer where sows have heavily contaminated udders from wallowing or in wet weather where beds are not renewed between batches.

As well as scouring, the main clinical sign of the disease is loss of condition which will lead to reduced weaning weights, with implications for overall growth to slaughter.

Good hygiene is the major preventative measure but the oocysts shed in the pigs’ faeces are highly resistant to conventional disinfectants and a specific anti-coccidial disinfectant is no longer available.  Thorough washing of pens with a detergent is vital and effective treatments are also fire (flame gun) and lime washing.  In outdoor herds, arcs must  be moved between consecutive farrowings and where problems occur, boards should be avoided and burning of used bedding after each weaning is considered more effective than lifting and removal.

Once an individual pig is affected, treatment is of limited value with the most effective cure being withdrawal of milk, but preventative medicine is available and highly effective.

Hygiene is the key

In the battle against the disease, one of the most important weapons is hygiene.  Coccidiosis is spread by faeces through oral transmission and eggs can survive for more than a year, even withstanding freezing conditions.  Contaminated water troughs, dirty udders, housing that is not properly cleaned can all harbour the eggs and, as they are sensitive to sunlight, dark corners in sheds can be a hot spot unless properly decontaminated.  To disinfect against coccidiosis, it is essential to ensure you are using a product that is labelled coccidiocidal or oocidal and that you follow the correct dilution rates.

There is no cross-protection between different species of Eimeria, so lambs or calves exposed to one species when housed, will not have immunity against a different species they may be exposed to when turned out.  Outdoors, a pasture-rotation plan can help reduce risk as a field contaminated in one season is likely to infect animals turned out in it the next.


For more detailed information on the occurrence, prevention and treatment of Coccidiosis, visit