Calf Coccidiosis Enteropathy

Calf coccidiosis is an enteric disease caused by protozoan parasites of the genus Eimeria, leading to significant economic losses in the cattle industry. Understanding its pathogenesis, clinical manifestations, diagnostic approaches, and management strategies is crucial for veterinary professionals preparing for the NAVLE examination.(scielo.br)

Type of Agent: Protozoan parasite

Classification of the Agent:

• Phylum: Apicomplexa(scielo.br)

• Class: Conoidasida(msdvetmanual.com)

• Genus: Eimeria(scielo.br)

• Species: Notably Eimeria bovis and Eimeria zuernii are the most pathogenic in cattle. (nadis.org.uk)

Clinical History:

• Typically affects calves aged 3 weeks to 6 months, with peak incidence around 1 to 2 months. (merckvetmanual.com)

• Outbreaks often associated with stressors such as weaning, transportation, overcrowding, or sudden dietary changes.

• High morbidity with variable mortality rates, depending on the Eimeria species and management practices.(msdvetmanual.com)

Transmission of the Disease:

• Fecal-oral route.(msdvetmanual.com)

• Ingestion of sporulated oocysts from contaminated feed, water, or environments.(msdvetmanual.com)

• Oocysts are highly resistant and can survive in the environment for extended periods.

Causes:

• Ingestion of infective Eimeria oocysts.(nadis.org.uk)

• Predisposing factors include poor sanitation, high stocking densities, and environmental stressors.

Clinical Presentation:

• Diarrhea, which may range from watery to bloody.

• Tenesmus (straining to defecate).

• Dehydration and weight loss.

• Depression and reduced feed intake.

• In severe cases, dysentery and death.

Changes in Clinical Pathology Tests:

• Hemoconcentration due to dehydration.

• Hypoproteinemia resulting from protein-losing enteropathy.(msdvetmanual.com)

• Electrolyte imbalances: hyponatremia, hypokalemia.

• Metabolic acidosis.

Differentials:

• Enterotoxigenic Escherichia coli infection.

• Salmonellosis.

• Cryptosporidiosis.

• Rotavirus or coronavirus enteritis.

Diagnostic Tests to Confirm:

• Fecal flotation to detect Eimeria oocysts.(scielo.br)

• Quantitative oocyst counts to assess infection intensity.

• Histopathological examination of intestinal tissues revealing developmental stages of Eimeria and mucosal damage.

Changes in Other Tests (e.g., Imaging):

• Imaging is typically not utilized for diagnosis.

Life Cycle of Eimeria spp.:

1. Ingestion of sporulated oocysts by the host.(msdvetmanual.com)

2. Excystation in the small intestine releases sporozoites.

3. Sporozoites invade intestinal epithelial cells and undergo asexual replication (schizogony).

4. Merozoites released from ruptured cells invade new cells, continuing asexual cycles.

5. After several asexual generations, merozoites develop into sexual stages (gametogony), forming microgametes (male) and macrogametes (female).

6. Fertilization results in the formation of oocysts, which are shed in feces.

7. Oocysts sporulate in the environment, becoming infective to the next host.

Possible Treatments:

• Supportive Care:

  • Oral or intravenous fluid therapy to correct dehydration and electrolyte imbalances.

  • Provision of easily digestible, high-quality feed to support recovery.

• Anticoccidial Therapy:

  • Sulfonamides (e.g., sulfadimethoxine): 55 mg/kg orally as an initial dose, followed by 27.5 mg/kg daily for 4 days.

  • Amprolium: 10 mg/kg orally daily for 5 days.

  • Toltrazuril: 15 mg/kg orally as a single dose.

  • Note: Dosages may vary; consult current veterinary guidelines.

Zoonotic Risk:

• Eimeria species affecting cattle are host-specific and do not pose a zoonotic risk.(en.wikipedia.org)

Reportable Status:

• Coccidiosis is generally not a reportable disease; however, reporting requirements may vary by region.

Disease Control:

• Prevention:

  • Maintain proper sanitation and hygiene in calf-rearing areas.

  • Avoid overcrowding and reduce environmental stressors.

  • Implement strategic use of anticoccidial feed additives (e.g., ionophores like monensin or lasalocid) as preventive measures.

• Management During Outbreaks:

  • Isolate affected animals to reduce transmission.

  • Administer therapeutic anticoccidial treatments to clinically affected calves.