Bovis ISSN 2398-2993

Coccidiosis

Synonym(s): Eimeria spp, E. bovis, E. zuiernii, E. alabamensis, E. aubernensis, E. basiliensis, E. bukidnonensis, E. canadensis, E. cylindrica, E. ellipsoidalis, E. pellita, E. subsherica, E. wyomingensis

Contributor(s): Mike Taylor , Andrew Forbes

Introduction

  • Causes: Eimeria spp, E. bovis, E. zuiernii, E. alabamensis, E. aubernensis, E. basiliensis, E. bukidnonensis, E. canadensis, E. cylindrica, E. ellipsoidalis, E. pellita,  E. subsherica, E. wyomingensis.
  • Signs: most infections are non-pathogenic. Diarrhea and dysentery associated with infections of E. bovis and E. zuernii; watery diarrhea with E. alabamensis.
  • Diagnosis: history, clinical signs, identification of oocysts in feces.
  • Treatment: diclazuril, toltrazuril, decoquinate.
  • Prognosis: most infections asymptomatic. Infections with pathogenic species can cause severe diarrhea, dysentery, dehydration and death.
Print off the farmer factsheet on Coccidiosis to give to your clients.

Pathogenesis

Etiology

  • Clinical disease is associated with the presence of pathogenic coccidian (E. zuernii Eimeria zuernii or E. bovis), infections, which occur in the lower small intestine, cecum and colon Eimeria species.
  • E. alabamensis has been reported to cause enteritis in first-season grazing calves in the first week following turnout and also later in the grazing season.

Predisposing factors

General

  • The disease is usually associated with a previous stressful situation such as weaning; transport; overcrowding; changes in feed; severe weather; or concurrent infection with parvovirus.

Pathophysiology

  • Following ingestion, sporulated oocysts excyst releasing sporozoites, which invade epithelial cells in the gut mucosa.
  • Infected endothelial cells become hypertrophic forming first generation (“giant”) meronts.
  • These rupture and the resulting merozoites infect epithelial cells in the large intestine producing second generation meronta and then gamonts.
  • The most severe pathological changes occur in the cecum, colon and terminal part of the ileum, and are due to the gamonts.
  • The mucosa appears congested, edematous, and thickened with petechiae or diffuse hemorrhages and the gut lumen may contain large amounts of blood.
  • Later in the infection the mucosa is destroyed and sloughs away and the sub-mucosa may also be lost.
  • In areas where damage to the mucosa is widespread, the mucosa may ulcerate and granulate, whilst in other less affected areas, the sub-mucosa shows signs of regeneration with hyperplastic crypts.

Timecourse

  • First generation meronts appear about 2 weeks post infection and gamonts thereafter.
  • The prepatent period is 2-3 weeks for most species of coccidia.
  • Clinical signs generally appear 2-4 weeks post infection and following a period of stress.

Epidemiology

  • High stocking densities and intensive husbandry systems with overcrowding in unhygienic yards or feedlots lead to a build-up infective oocysts and disease outbreaks.
  • Stress factors, such a poor milk supply, weaning, cold weather and transport, will reduce any acquired resistance and exacerbate the condition.
  • Year round calving can present problems with constant use of calf pens with successive batches of young calves added to pens or buildings already housing older calves.
  • The season of the year can play a role in the appearance of coccidiosis.  
  • Coccidiosis is common in spring when young calves are born and turned out onto permanent pastures close to the farm buildings. Inclement weather at this time may cause stress at this stage lowering immunity and precipitating disease.
  • Cold winters favor survival of overwintering oocysts in large enough numbers to represent sufficient disease challenge at turn out in spring; conversely mild wet springs favor sporulation, and rapid accumulation of large numbers of infective oocysts.
  • Autumn born calves may be born into an already heavily contaminated environment.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Phillipe P, Alzieu J P, Taylor M A & Dorchies Ph (2014) Comparative efficacy of diclazuril (Vecoxan®) and toltrazuril (Baycox bovis®) against natural infections of Eimeria bovis and Eimeria zuernii in French calves. Vet Parasitol 206, 129-137 PubMed.
  • Zechner G, Bauer C, Jacobs J, Goossens L, Vertenten G & Taylor M A (2014) Efficacy of diclazuril and toltrazuril in the prevention of coccidiosis in dairy calves under field conditions. Vet Rec 176 PubMed.
  • Taylor M A (2000) Protozoal Disease in Cattle and Sheep.  In Practice 22, 604-617.
  • Taylor M A & Catchpole J (1994) Coccidiosis of Domestic Ruminants. Applied Parasitology 35, 73-86

Other sources of information

  • Taylor M A (2004) 1.4.1 Antiprotozoals. In: The Veterinary Formulary. 6th edn. Royal Pharmaceutical Society of Great Britain and British Veterinary Association. London.  pp 171-179.


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