What causes coccidiosis
Coccidiosis is caused by parasites that infect the cells lining an animal’s intestine. Animals get infected by swallowing the parasites. This can happen by eating infected pasture and feed, drinking contaminated water, or by grooming themselves.
The parasites that cause cocciodiosis (coccidia) are widespread, and only a small proportion of infected animals will become sick. Disease tends to occur when animals consume large numbers of parasites, while also being exposed to stress, such as overcrowding or poor weather conditions. The effect of the disease can range from very mild to severe. Severely affected animals may die.
Signs in animals
Coccidiosis is most commonly a disease of cattle aged three to eight months. Occasionally the disease is seen in animals as young as four weeks, and in older animals. Subclinical infections will cause reduced feed intake and weight gain, which can often go unnoticed.
In animals that become sick, the first sign of illness is usually the sudden onset of diarrhoea. The diarrhoea may contain mucous and blood, and the animal may have frequent straining to pass faeces. The animals will be obviously unhappy and uncomfortable, will be off their feed, and frequently become dehydrated. It can take 16 to 30 days after being infected with the parasite for an animal to get sick. The worst symptoms will usually last for five to seven days, and if the animal survives, recovery begins seven to 10 days later.
Affected calves lose weight quickly. Due to the damage caused to their intestinal lining, regaining condition takes a long time. Recovery typically takes many weeks and some animals will become chronically unthrifty. Mild or chronic cases can also happen, where mild diarrhoea occurs but there is no mucous or blood.
Diagnosis is usually based on clinical signs. Faecal samples can be used to confirm the diarrhoea is being caused by coccidia parasites. Treatment is with Baycox (a coccidiostat) or injectable Amphoprim (an antibiotic). Treatment is usually successful if it is started early and there are no other underlying diseases, such as BVD.
How it is spread
Animals infected with coccidia pass parasite eggs in their faeces. These eggs can survive for up to two years in moist environments such as soil and calf sheds, which means that infection can be carried over from one season to the next. However, the eggs are destroyed by drying and heat. Steam cleaning, and drying out buildings and feeding equipment, will reduce build-up of eggs and minimise the spread of infection.
Infection is more likely to occur when there has been a significant build-up of coccidia eggs on paddocks and in calf sheds, especially when the stocking density is high. Animals are also more likely to get sick when they have lowered immune resistance. This can happen from poor nutrition, being sick with other diseases, and stressful events such as cold, wet weather.
Management, prevention and control of coccidiosis
To achieve effective control of coccidiosis, good management and hygiene is vital. This includes reducing stocking densities, preventing contamination of feed and water troughs, increasing bedding to reduce faecal contamination, and cleaning and disinfecting buildings. Buildings should be steam cleaned or water blasted, then sprayed with a product that kills coccidia eggs. For pasture grazed calves, rotational grazing with reasonable stocking rates will reduce exposure to infection.
Prevention of infection can be achieved by feeding calves meal containing drugs that slow the growth of coccidia, called coccidiostats. However, this needs to be at the correct rate and for long enough after weaning to provide effective prevention.
If an outbreak of coccidiosis occurs, affected calves should be separated from calves not showing signs of infection, and provided with treatment for diarrhoea. Treatment specifically for coccidiosis should be given to all calves in the group, even those showing no clinical signs. All calves should also be moved to an uncontaminated area, stocking rates should be reduced, and any stressful procedures minimised.
Animals that survive the disease outbreak will take time to recover and may require preferential feeding to obtain satisfactory growth rates.