Pathophysiology and Transmission of Brucella Abortus

Bovine Brucellosis is a systemic bacterial infection caused by Brucella abortus. Unlike localized environmental conditions like Ovine Foot Rot, *Brucella

  • acts as an intracellular pathogen. Once ingested or inhaled, the bacteria are phagocytized by neutrophils and macrophages. They survive and replicate within these cells, effectively hiding from the host's humoral immune response.

Mechanisms of Reproductive Failure

During pregnancy, the bacteria reach the uterus. They specifically target the placental trophoblasts, causing severe inflammation of the cotyledons (placentitis). This disrupts fetal-maternal nutrient exchange, leading to fetal death and late-term abortion. It is crucial to differentiate this from non-infectious reproductive failures or other viral causes seen in livestock, such as Swine Influenza.

Clinical Manifestations and Identifying Infection

The most recognizable sign of the infection is the 'abortion storm' within a herd. While other pathogens like Swine Erysipelas might present with acute cutaneous or systemic fever, Brucellosis is often insidious until a sudden rise in pregnancy terminations occurs.

Reproductive and Systemic Signs

  • Late-term abortions (usually occurring after 5 months of gestation)

  • Retained fetal membranes (placentitis)

  • Metritis (uterine infection) leading to decreased fertility

  • Epididymitis and orchitis in bulls (swollen testicles)

  • Hygromas (swollen knee joints) due to bursitis

  • Decreased milk production across the herd

Diagnostic Framework and Laboratory Surveillance

Diagnosis is rarely based on clinical signs alone, as these can mimic other reproductive disorders. Veterinarians utilize serological testing, such as the Milk Ring Test or Enzyme-Linked Immunosorbent Assay (ELISA), to screen entire herds. Unlike diagnosing Ovine Foot Rot which involves visual examination of the hoof, *Brucella

  • requires rigorous laboratory confirmation.

Bacteriological Confirmation

  • Brucella Milk Ring Test (BRT) for herd screening

  • Serum Agglutination Test (SAT)

  • Polymerase Chain Reaction (PCR) testing of fetal tissues or placental samples

  • Culture and isolation of the organism (performed only in high-containment bio-secure labs)

Management Strategies and Zoonotic Risks

There is no effective cure for Brucellosis in cattle; therefore, treatment is generally not attempted. Infected animals are typically culled to prevent spread. This stands in stark contrast to treatable infectious diseases like Swine Erysipelas, where antibiotic intervention is often successful. Prevention focuses heavily on biosecurity, vaccination with Strain 19 or RB51, and strict control over animal movement. Owners must prioritize the safety of human handlers, as human brucellosis (Undulant Fever) is a debilitating long-term illness.