Coccidiosis
Coccidiosis
Summary.
Coccidiosis in calves is an important disease that has a damaging effect on the gastrointestinal tract.
Animals eventually develop immunity to the parasite but there is a significant cost from infection that affects gut health and productivity of the young, growing animal.
Metaphylactic use of toltrazuril following weaning from meal kills all stages of the coccidia lifecycle, prevents disease, and maintains calf health and productivity over this important period.
Coccidiosis is a protozoan parasite that infects the intestinal tract of many species of animals and is often found in calves aged 3 – 8months of age. In heavily contaminated environments calves may show clinical symptoms signs as early as four weeks of age.
The source of infection is generally from faeces of infected animals that are shedding oocysts. The calves ingest oocysts from contaminated pasture, feed and water or by grooming each other. Dry conditions and high temperatures in the pasture will destroy oocysts within a few weeks. However, under favourable conditions characteristic of many New Zealand farms the oocysts can survive for up to two years.
Steam cleaning, and drying out buildings and feeding equipment, will reduce build-up of eggs and minimise the spread of infection.
The incidence and severity of the disease is often directly related to the level of stress, overcrowding or poor weather conditions and varies from mild to fatal.
Clinical symptoms.
Typically, coccidiosis has high morbidity (sickness) and moderate mortality, with long term effects on growth rates in animals that survive. The gut mucosa becomes denuded and stripped of villi which results in possible haemorrhage and impaired water absorption. The severity depends on the level of infestation and the calf’s immune response. The impact of coccidiosis may be heightened via stress, poor nutrition or concurrent diseases.
Symptoms may be classified as:
Clinical coccidiosis: In animals that become sick, the first sign of illness is usually the sudden onset of diarrhoea. Blood and mucous stained faeces are often the first sign of disease. Infected calves go on to exhibit severe unproductive straining while defecating. Temperature is mildly elevated (39.0 - 39.5ºC). Dehydration and lack of appetite are common. Faecal staining of the tail, hind quarters and hocks is a strong indication of the presence of coccidiosis.
The acute phase of the disease lasts 5 to 6 days and if the animal survives, recovery begins at 7 to 10 days. Affected calves lose weight rapidly, and due to gut damage, regaining condition takes a long time.
Severely affected calves typically undergo a convalescence of many weeks, during which feed intake and weight gains are reduced.
Subclinical coccidiosis: Mild and/or chronic cases typically show weight loss (or lower than expected weight gain which may go unnoticed), with possible anaemia and mild or no diarrhoea. Calves may have droopy ears and rough coats.
Diagnosis of Coccidiosis:
An accurate definitive diagnosis can be made at post-mortem examination. Laboratory tests for coccidia oocysts are of limited use due to:
Few oocysts present in the faeces despite sever damage to the gastrointestinal tract,
Non-pathogenic oocysts ay be present in large numbers
Oocysts numbers may be under-estimated because of the dilution effect of fluid faeces
If there is a clinical picture consistent with coccidiosis but only small numbers of coccidia oocysts are detected in the faeces it could still be a coccidial infection.
Coccidiosis outbreaks:
Outbreaks often occurs when there is significant build-up of coccidia oocysts on paddocks and overstocking, especially in wet conditions.
As a preventative most calf meals/pellets contain a coccidiostat such as Monensin or Lasalocid which suppress coccidia but do not kill them thus maintaining infective coccidiosis challenges low while they are consuming treated feed.
However the calves have little opportunity to build up an immunity against the parasite and once the feeding of meal/pellets discontinues (often at two to four months of age) outbreaks can occur especially if the same ‘calf paddocks’ are used each year.
Stresses associated with transport, feed changes, poor nutrition, concurrent disease or heavy worm burdens may increase the incidence of coccidiosis outbreaks.
Rotational grazing post weaning preferably on fresh pastures grazed by adult cattle reduces the challenge whilst the calf is building up immunity.
Treatment/prevention.
The incubation period for the coccidiosis parasite is 2-4 weeks so both subclinical and clinical coccidiosis commonly occurs approximately four weeks after weaning from meal.
Oral treatment of the whole group of animals with a toltrazuril based product at weaning will kill all the intracellular stages of the parasite and is an effective preventative treatment. Even when faecal counts indicate a low level of infection with coccidia there is a consistent weight gain advantage of 3kg – 5kg during the five weeks after weaning.
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.
References: https://www.dairynz.co.nz/animal/cow-health/coccidiosis/
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