Brucellosis

Brucellosis is a global problem because of its public health and economic implications. It is one of the serious diseases affecting livestock all over the worlds that can be transmitted to human beings through the ingestion of contaminated animal products and handling of infected animals. Brucellosis is an occupational hazard in farming, veterinary practice and meat processing, where Brucella can enter through the skin, particularly in areas of minor abrasions. In animals, it tends to localize in the genital tract but it involves the reticuloendothelial system in humans. Brucellosis is caused by several species of Brucella, viz. B. abortus, B. melitensis, B. suis. B. canis and B. ovis. A human being gets infected with Brucella through ingestion, contact, inhalation and accidental inoculation. Goats, sheep, cattle, water buffaloes and swine are the principal group of animals which serve as sources of human infection. Unpasteurised milk, butter, cream and cheese prepared from milk obtained from infected animals are commonly involved in the transmissions. Meat and meat products, particularly when they are not properly cooked, are a potential source of infection. The vaginal discharges, fetuses and placenta of infected animals are the richest sources of Brucella infection. Contact with these materials as well as contact with urine, manure and carcasses is mainly responsible for occupational brucellosis.Infection is common in veterinarians, farmers, packing-house workers, animal handlers, factory workers engaged in primary processing of wool, and abattoir and laboratory workers. Laboratory workers and veterinarians also are exposed frequently to the risk of infection by accidental inoculation or inhalation.

Clinical features: The incubation period is variable. It is usually 10 to 30 days but sometimes takes several months. The onset of the symptoms is usually insidious with  malaise, chills, fever, sweats, weakness myalgia and headache. Fever may be remittent particularly with B. melitensis (undulant fever). Bodyache, particularly backach, headache, insomnia, and anorexia are common and a nonarticular arthralgia develops affecting the knee, ankle, shoulder or elbow. There is weight loss. Infection with B. abortus is usually milder than with B. suis or B. melitenis.

Laboratory diagnosis: Laboratory tests for diagnosis of human brucellosis include bacteriological, serological and allergic tests. Bacteriological tests for isolation of the organism, serum agglutination test (plate and tube agglutination test), complement fixation   test/ Coomb ’s   test ,   indirect   haemagglutination   test ,   indirect immunofluorescence test, intradermal test are the various tests used fordiagnosis. Molecular diagnosis is done by polymerase chain reaction (PCR) using their specific primers.

Control and prevention: Strict hygienic and sanitary conditions are the primary measures for controlling brucellosis, particularly in the occupational group. The following measures are helpful in eliminating the infection:
1.  Adequate heat treatment of all consumable products of animal origin.
2.  Use of protective clothings by the occupational groups at risk.
3.  Removal of the after birth and excreta of animal and their sanitary disposal.
4.  Disinfection of farm premises, animal sheds, and abattoirs, etc.
5.  Control of animal brucellosis which will eventually eliminate human brucellosis.