Special Veterinary Pathology

BRUCELLOSIS

Synonym

• Mediterranean fever, Gastric fever, Bruce septicaemia, Malta fever, Bang’s disease, undulant fever in humans.

Incidence

• 1887 – Spleen of patients (Brucella mellitensis)
• 1905 – The infection was traced to goat’s milk
• 1897 – Isolation and identification of organism in aborted bovine fetuses and fetal membrane (Brucella abortus)
• 1914 – Identification of Brucella suis in pigs
• 1950 – Brucella ovis in rams
• 1960 – Bruella canis in dogs

Etiology

• Gram negative, mostly rod shaped or coccoid, Brucella mellitensis, B. abortin, B.suis, B. ovis, B. canis.

Pathogenesis

• Entry of organism by ingestion
• Localized in regional lymph node
• Enter into intestinal epithetial cells
• Enter lymphatics
• Bactermia
• Localize in reproductive organs, placenta, fetus, mammary glands, lymph nodes, spleen, liver, joints, bones.
• Organism proliferates within the cells
• Affinity of bacteria to placenta and focus esp. chorio – allantoic trophoblast
• Due to erythritol in these tissue
• Abortion.
• Brucell a organism
• Phagocytosis by macrophages
• Survive inside the macrophages
• Prevents fusion of lysosone with phagosomes
• Bacteria not exposed to lysososmal enzymes
• Bacteria grows inside phagosomes of macrophages
• Hence antibodies are in effective against bacteria
• Macrophages rupture, release the bacteria

Transmission in cattle

• By contact
• Ingestion of infective uterine discharge, aborted foetus or placenta
• Organisms are excreted in milk
• Rare through coitus
• Bulls are resistant

Clinical signs

• Cattle
• Abortion in 7^th and 8^th months of gestation
• Persistent infection in cows exposed after puberty
• Pigs
• Transmission through coitus.
• Abortion in 2^nd and 3^rd months of gestation
• Orchitis in infected boars
• Localization in other tissues like skeleton more common
• Sheep and goats
• Transmission same as cattle
• Abortion in ewes
• Orchitis, epididymitis in male sheep and goats.
• Dogs
• Caused by B. canis
• Transmitted by exposure to uterine discharges or aborted fetuses or by coitus.
• Abortion in 50 days of gestation
• Male dogs – orchitis / epididymitis.
• Horses
• B. abortus + Actinomyces bovis
• “Poll evil” and “Fistulous withers”

Lesions

• Bacterial granuloma in tissues, especially in lymphoreticular system.
• No multinucleated giant cells. These ganulomas are visible grossly, or may be of microscopic size- classical lesion of Brucellosis

Gross lesions

• Necrosis of cotyledons
• Inter – cotelydonary chorion is oedematous and filled with odourless, sticky, brownish exudates
• Yellowish granular, necrotic areas in colytedon.
• Rest of chroion is opaque, thickened and leathery
• Induration of bovine mammary glands and supramammary lymphnodes
• Epidydymis and testicles of bulls become enlarged and hard
• Scrotal contents – suppuration & rupture

Pigs

• Tiny white yellowish nodules in all organs

Rams

• Tail of epididymis a inflammed

Bitches

• Uterine and placental lesions
• Bronchopneumonia in aborted pups
• Osteomyelitis in dogs

Horses

• Necrotizing and purulent lesions in ligamentum nuchae
• Necrotizing and purulent lesions in region of thorasic attachment of ligamentum nuchae.

Microscopic lesion

• Bovines
• Organisms in chorionic epithelial cells
• Necrosis and inflammatory exudates with macrophages and neutrophils
• Collection of epithelioid cells in endometrium.
• Mammary gland
• Diffuse inflammation, with lymphocytes and neutrophils.
• Collection of epithelioid cells with langhan’s giant cells.
• Later atrophy of glands and fibrosis
• Pigs
• Typical Brucella granulomas with necrosis
• Rams
• Perivascular oedema and lymphocytic infiltration
• Hyperplasia and degeneration of tubular epithelium and intertubular fibrosis
• Escape of spermatozoa from damaged tubules produced granulomatous response
• Bitches
• Hyperplasia and plasmacytosis of lymphnodes
• Orchitis
• Epididymitis
• Prostatitis
• Hyalinization of glomeruli

Diagnosis

• Symptoms and lesions
• Agglutination test to detect antibodies
• Immunological staining or molecular probes