Calf Enteritis Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is a primary etiological agent responsible for neonatal diarrhea in calves, 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.

Type of Agent: Bacterium(merckvetmanual.com)

Classification of the Agent:

• Family: Enterobacteriaceae(merckvetmanual.com)

• Genus: Escherichia

• Species: Escherichia coli

• Pathotype: Enterotoxigenic Escherichia coli (ETEC)

Clinical History:

• Primarily affects neonatal calves, especially within the first 3–5 days of life.

• High morbidity with variable mortality rates.

• Sudden onset of clinical signs, often within hours post-infection.

Transmission of the Disease:

• Fecal-oral route.

• Ingestion of ETEC-contaminated feed, water, or contact with contaminated environments.

• Carrier animals, including asymptomatic adults, can shed the bacteria, contaminating the environment.

Causes:

• Ingestion of pathogenic ETEC strains possessing specific virulence factors, notably fimbrial adhesins (e.g., F5 [K99] antigen) and enterotoxins (e.g., heat-stable toxin Sta).(merckvetmanual.com)

Clinical Presentation:

• Profuse, watery diarrhea leading to rapid dehydration.

• Depression and weakness.

• Anorexia.

• Hypothermia or normal body temperature; fever is uncommon.

• Without prompt treatment, hypovolemic shock and death can occur within 12–24 hours.(merckvetmanual.com)

Changes in Clinical Pathology Tests:

• Hemoconcentration due to dehydration.

• Electrolyte imbalances: hyponatremia, hypokalemia.

• Metabolic acidosis.

• Possible hypoglycemia.

Differentials:

• Rotavirus enteritis.

• Coronavirus enteritis.

• Cryptosporidiosis.

• Salmonellosis.

• Clostridium perfringens infection.

Diagnostic Tests to Confirm:

• Bacterial culture and isolation of ETEC from fecal samples.

• Detection of fimbrial antigens (e.g., F5 [K99]) using immunoassays.(merckvetmanual.com)

• PCR assays targeting virulence genes (e.g., sta encoding heat-stable enterotoxin).(merckvetmanual.com)

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

• Imaging is typically not utilized for diagnosis.

Possible Treatments:

• Supportive Care:

  • Oral rehydration solutions containing electrolytes and glucose for mild cases.

  • Intravenous fluid therapy in cases of severe dehydration.

  • Correction of acid-base imbalances.

• Antimicrobial Therapy:

  • Indicated to reduce bacterial load and prevent septicemia.

  • Selection should be based on antimicrobial susceptibility testing.(merckvetmanual.com)

  • Common choices include:

    • Ampicillin: 10–20 mg/kg IV or IM every 8–12 hours.

    • Ceftiofur: 2.2–4.4 mg/kg IV or IM once daily.

    • Trimethoprim-sulfamethoxazole: 15–30 mg/kg PO every 12 hours.

• Other Medications:

  • Nonsteroidal anti-inflammatory drugs (NSAIDs) for pain and inflammation management, e.g., flunixin meglumine at 1.1–2.2 mg/kg IV once daily.

Zoonotic Risk:

• Certain ETEC strains can be zoonotic, posing a risk to humans, especially immunocompromised individuals.

• Strict hygiene and biosecurity measures are essential to mitigate this risk.

Reportable Status:

• ETEC infections in calves are generally not reportable; however, reporting requirements may vary by region.

Disease Control:

• Prevention:

  • Ensure adequate colostrum intake to confer passive immunity.

  • Implement strict biosecurity measures to prevent introduction and spread.

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

  • Vaccination of pregnant dams with ETEC vaccines to enhance colostral antibodies.

• Management During Outbreaks:

  • Isolate affected animals to reduce transmission.

  • Enhance supportive care to affected calves.

  • Thoroughly clean and disinfect contaminated environments.

Prognosis:

• Generally favorable with prompt and appropriate supportive care.

• Delayed or inadequate treatment can lead to increased mortality.