Coccidiosis in Calves

Coccidiosis in calves is a disease that can strike at any time of the year, without warning, and left untreated – or treated too late, can cause severe loss of condition with consequent economic loss.

The following article, written by Susan Mckay of The Companion Consultancy and generously sponsored by Janssen Animal Health, will help the smallholder understand the disease, and what to do to minimise its impact on their herd.

Companion Consultancy website


Coccidiosis in Calves

Scour is just one of the signs you might observe if your calves have coccidiosis but sometimes the signs are harder to spot, and they can still be damaging.

Signs of Coccidiosis

highland-calvesCalves can suffer from coccidiosis at any time of the year and most commonly calves from 3 weeks to 6 months of age are affected. Although some calves will show obvious clinical signs of coccidiosis, larger numbers tend to have sub-clinical disease, where there are few or vague signs. In herds, most of the economic loss is likely to be due to the subclinically affected animals.



  • Clinical disease is characterised by bloody diarrhoea, weakness, dehydration and weight loss.
  • Sub clinical disease results in weight loss or failure to gain weight, poor appetite and a rough, dry coat.

Causes of Coccidiosis

gloucester-cattleCoccidiosis is caused by a microscopic parasite called Eimeria. Not all Eimeria species cause disease. The parasite is widely distributed and likely to be present on most farms. Although some Eimeria species cause disease, they only cause signs if the animal’s normal immune responses are compromised, and/or if the animal is infected by a high parasite load. A low background dose of Eimeria will most usually just help a healthy animal go on to develop future immunity against the parasite.

So the situations where coccidiosis may be observed are after any stressful event that adversely affects the immune system, or where there are high parasite numbers, such as in conditions of poor hygiene, overcrowding, or where older calves excreting parasite oocysts are mixing with younger unaffected calves. Stressful events include poor weather, castration, inadequate intake of colostrum, transport or turn out. In some farms there is an obviously identifiable trigger event that tends to lead to signs around 14-21 days later as the parasite completes its lifecycle. It is important to remember that when the signs appear, most of the gut damage has already occurred.

Implications for Treatment

belted-gallowayCoccidiosis can be treated with diclazuril (Vecoxan®2.5mg/ml Oral Solution). This  kills the Eimeria parasites which cause the disease while allowing the development of protective immunity1, although it is important to treat at the optimum time. Some animals that have already started scouring may need additional antibiotic therapy as well as treatment to address dehydration.



There are two ways to approach the timing of treatment with diclazuril. If there is an obvious identifiable trigger of coccidiosis on the farm, which is known as a result of previous experience, then calves should be dosed 10-14 days after the trigger. This is around one week before any signs are seen and is referred to as metaphylactic treatment. The other approach, if coccidiosis is suspected, is to treat all the animals in the batch as soon as one or two animals start scouring.

Diagnosis of coccidiosis can prove difficult, as faecal oocyst counts do not always differentiate between pathogenic species that cause disease and non-pathogenic species of Eimeria.  It is always best to work with your vet to establish whether treatment is needed and to determine the optimum timing of any treatment on any individual smallholding.


In many cases it is not possible to completely prevent animals from becoming ill due to coccidiosis through management alone, but it helps to keep over crowding to a minimum, practice good hygiene, batch up calves by age and avoid mixing of batches, ensure adequate intake of colostrum, feed from troughs and minimise ‘stress’.


Agneessens J, Goossens L, Louineau J, Daugschies A, Veys P. Build up of immunity after a diclazuril (Vecoxan®) treatment in calves , Poster at 24th World Buiatrics Congress, Nice 2006

Vecoxan® 2.5 mg/ml Oral Suspension contains diclazuril 2.5mg/ml. Legal Category POM-VPS.

Contraindications and side effects

None known.

Warnings and precautions

No known contraindications or interactions with any other medicine.

For oral use in lambs and cattle only. Shake well before use.  It is advocated to treat all animals in a group. Always consider other causes for the symptoms.  In cases of acute clinical coccidiosis fluid therapy is essential and the use of an antibiotic should be considered.

Meat withdrawal period: zero days.

Wash hands after administration of the product.

Do not store above 30ºC. Protect from frost.

Any unused product or waste material derived from such a veterinary medicinal product should be disposed of in accordance with national requirements.

Always seek advice on the correct use of medicines from the prescriber – your veterinarian or suitably qualified person.


For full contraindications and warnings please refer to the SPC

Further information about Vecoxan® and coccidiosis is available from Janssen Animal Health, 50-100 Holmers Farm Way, High Wycombe, Bucks, HP12 4EG Tel 01494 567555 Fax 01494 567556 Email: This email address is being protected from spambots. You need JavaScript enabled to view it.">This email address is being protected from spambots. You need JavaScript enabled to view it.