This is a subscriber-only article
Coccidiosis is one of the most common causes of "blood scour" in young calves in this country as in Figure 1.
Figure 1.
It is caused by protozoan parasites, Eimeria zuernii and Eimeria bovis, and most commonly affects calves from three weeks of age onwards.
An animal becomes infected by ingesting faeces (dung) containing coccidial oocysts (resistant eggs).
Following entry into the intestines, the parasite eggs hatch and immature parasites invade the cells lining the gut wall where they mature, reproduce, multiply and essentially rupture the cells lining the intestines.
Many affected calves will go on to carry these parasites as adults and, therefore, act as one of the primary sources of infection on the farm. Occasionally, weanlings and adult animals will suffer clinical disease due to coccidiosis, especially if there is a heavily contaminated environment or if animals are immunosuppressed due to other diseases, stress or nutritional imbalances.
Coccidiosis can also be a significant disease in sheep flocks, although the diarrhoea may not be as marked in many cases.
Symptoms
This disease is most commonly associated with profuse watery brown/green diarrhoea, frequently containing blood. In severe cases, the diarrhoea can be red in colour but is usually not as foul-smelling as Salmonellosis.
As with all cases of diarrhoea, calves may become dehydrated and weak if treatment is not initiated early. The severe inflammation of the large intestine, and in particular the colon and rectum, can cause an affected calf to show continuous signs of straining to pass faeces, with a raised tail as in Figure 2.
Figure 2
In some cases, this continuous straining can result in prolapse of the rectum, which can have fatal consequences if the exposed rectum becomes traumatised.
One of the most significant economic effects of coccidiosis is the stunting it commonly causes in infected calves. Many calves have poor weight gain subsequently and never reach their growth and production potential.
Diagnosis
While the age of the affected calf and the clinical presentation can be highly characteristic of coccidiosis, definitive diagnosis can only be confirmed by the laboratory analysis of dung samples from affected animals.
Treatment
There are two effective coccidostats on the market for the treatment of bovine coccidiosis. The products available are the oral drenches "Vecoxan", which contains diclazuril, and "Baycox Bovis", which contains toltrazuril. These products will certainly treat affected animals effectively, but they are most efficient when used as preventatives on in-contact or at-risk calves prior to clinical signs.
Sulphonamide or potentiated sulphonamide antibiotics are also useful in the treatment of coccidiosis. They have been shown to inhibit the development of immature coccidiosis parasites, and also play an important role in controlling secondary bacterial overgrowths that occur in the intestines of affected calves.
It is also crucial to pay strong attention to calf dehydration risk and administer fluids when necessary. If the calf is very weak, with sunken eyes and difficulty or inability to stand, it is crucial to seek veterinary intervention and intravenous fluid therapy.
In cases where calves/ lambs show persistent straining, long-acting epidurals can be administered by your veterinary practitioner, together with anti-inflammatories. If rectal prolapse occurs as in figure 3, the rectum must be replaced and sutures may be needed to keep it in place.
Figures 3.
If the prolapsed rectum becomes traumatised, surgical removal of the damaged tissue may be necessary.
Control/prevention
Coccidia are shed in the environment as resistant oocysts in faeces. These oocysts can remain infective for years and can maintain infection in housing if proper cleaning is not carried out. These eggs are also resistant to most disinfectants, including iodine and chlorhexidine.
Disinfectants such as Kilcox and Oo-cide (off the market currently) are effective when applied to surfaces following the initial removal of organic matter. Apart from reducing the environmental load through cleaning and disinfection, it is vital to prevent new infections in problem herds by the strategic use of coccidostats.
One affected calf can excrete up to a billion oocysts over the course of a full infection leading to the rapid spread of this highly contagious disease. Therefore, as always, prevention is better than cure.
Calves on farms where coccidiosis has been diagnosed should be strategically treated with coccidiostats at seven to 10 days of age, and again two weeks later where environmental contamination is high. Infected calves showing clinical signs should also be removed from the group as soon as possible, and strict hygiene measures employed in relation to feeding utensils and footwear.
SHARING OPTIONS: