Plague in Animals

Plague in Animals: An Overview

Etiology and Transmission

  • The bacterium causing plague, Yersinia pestis, is a gram-negative, facultative, nonspore-forming coccobacillus within the Enterobacteriaceae family.

  • Maintained in a rodent-flea transmission cycle involving many wild rodent species. Non-rodent mammals (canids, felids, lagomorphs, mustelids, and occasionally ungulates) can also be infected. Birds and non-mammalian vertebrates are not susceptible.

  • Common infection routes in pets: consuming infected rodents/lagomorphs and bites from infected fleas.

  • Transmission from pets to humans can occur via transportation of infected fleas, bites, scratches, aerosol droplets, and contact with infectious tissues.

  • Incubation period: 1-7 days.

  • Risk factors for pets include roaming in enzootic areas, hunting, consuming infected wildlife, and flea exposure.

Clinical Findings

  • Cats show three clinical manifestations of plague:

    • Bubonic plague: characterized by high fever, lethargy, anorexia, and lymphadenopathy, often with abscessed submandibular lymph nodes. Potential additional symptoms: oral lesions, skin abscesses, ocular discharge, diarrhea, vomiting, cellulitis.

    • Septicemic plague: presents with fever, lethargy, anorexia, and sepsis signs (vomiting, diarrhea, tachycardia, cold extremities, pale mucous membranes, and multiorgan failure).

    • Pneumonic plague: develops secondarily; symptoms include fever, dyspnea, oral/nasal discharge, coughing, and sneezing. Highly contagious via respiratory droplets.

  • Dogs are less likely to show severe clinical signs but transient fever and anorexia can occur along with rare lymphadenopathy. Severe cases can lead to pneumonia and potential death.

  • Domestic production animals rarely get infected; clinical illness noted in camels, camelids, and goats.

Diagnosis

  • Key diagnostic methods:

    • Culture (gold standard, time-consuming)

    • PCR

    • Direct fluorescent antibody testing

    • Serology (may yield false negatives)

  • PPE required during specimen collection. Preferred specimens: lymph node aspirates, whole blood, or fresh tissue.

Treatment

  • Antibiotic therapy significantly improves outcomes; starts immediately, regardless of diagnosis. Recommended antibiotics include fluoroquinolones, doxycycline, trimethoprim-sulfonamide, gentamicin, and chloramphenicol.

  • Patients typically become non-infectious after 48-72 hours of treatment.

Control and Public Health Response

  • Immediate isolation of suspect plague cases; notify public health authorities.

  • Infection control measures: PPE, proper disinfection, and education for pet owners in endemic areas.

  • Recommendations for owners include preventing pets from roaming, regular flea control, and immediate veterinary assessment for sick pets.