BRUCELLOSIS

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Causative Agent(s)

Brucellosis is an infectious disease caused by bacteria of the genus Brucella. In pigs Brucella suis is the primary and most important cause of infection. B. suis is a gram-negative coccobacillus measuring 0.6–1.5 μm in length and 0.5–0.7 μm in width.

Clinical Presentation and Epidemiology

Brucella suis is distributed worldwide.

It is widely spread across sub-Saharan Africa; however available data are limited, and the number of pigs infected are relatively small when compared to the rest of the world where pigs are raised.

Pigs get infected when they ingest aborted foetuses, foetal membranes or fluids that are discharged following abortion. Brucella can also be transmitted in infectious semen either

through natural breeding or artificial insemination or through abraded skin, conjunctiva, and nasal mucous membranes.

Brucellosis manifests as infertility in a herd of pigs. This is when a large number of sows or gilts return to heat at the next cycle after breeding. Sometimes, sows abort in their third trimester or farrow dead and weak piglets and apparent recovery is noticed. Few clinical signs are noticed in boars such as reduced fertility and libido.

Chronic infections that are usually in breeding stock manifests as fibrinous or fibrinopurulent arthritis of large joints of the legs. Osteomyelitis of the lumbar vertebrae occurs with paralumbar abscesses in infected pigs.

Diagnostic Considerations

The samples to be collected are mammary glands tissues, placentas, and synovial tissues, seminal vesicles, prostate gland, epididymis, testes, uterus, oviducts, liver, spleen, bones, tendons, bursae, brain, and lymph nodes, uterus, uterine tubes, and aborted foetus.

The presumptive diagnosis of brucellosis in pigs is by microscopic examination of smears of samples. Brucella organisms grow well on blood agar. Selective media can also be used where plates are incubated at 37°C with 5–10% Carbon dioxide to eliminate contaminants.

Serological tests for brucellosis in pigs are of little diagnostic value. All the conventional serological tests used for the diagnosis of brucellosis in domestic ruminants are unreliable when used on individual pigs. However, Complement Fixation Test (CFT), indirect (iELISA) and competitive (cELISA) enzyme-linked immunosorbent assays (ELISAs)have been used to diagnose this disease but the ELISAs have not been fully standardized for use in pigs. Polymerase chain Reaction has been used to confirm cases.

Management and Treatment

There is no published information on the efficacy of antibiotics for treating brucellosis in pigs.

Since there is no antibiotics for treating brucellosis, emphasis should be placed on prevention of the disease.

Prevention of brucellosis in pig herds can be achieved by instituting biosecurity measures on farms. Sows that abort and are infertile should be culled routinely. In addition, serological tests should be carried out to survey the disease and infected herds should be depopulated.