BRUCELLOSIS

Brucellosis is also known as Bang’s Disease. Brucellosis is known as a contagious abortion disease in animals. In humans, the disease is known as Malta fever, Mediterranean fever, and undulant fever. The disease is named after Sir David Bruce, an English army surgeon who identified the cause of the disease in Sir David Bruce found the causative agent to be Bacillus melitensis. He found the bacteria in the spleens of British soldiers who died of undulant fever on the Mediterranean island of Malta. Several years later the infection in these British soldiers was traced to the soldier’s drinking contaminated goat’s milk.

In 1897, Brucella abortus was isolated and identified from an aborted bovine fetus by Danish veterinarian, Dr. Fredrick Bang. The infection in cattle became known as Bang’s disease and was eventually proven to be ubiquitous in many animals. Brucellosis is one of the most serious diseases of livestock because of the damage it causes: decreased milk production weight loss loss of young infertility lameness

Note: Brucella spp. Was the first microbe that the United States chose to develop as a biological weapon The reasons it was chosen, include its ease of manufacture, susceptibility to sunlight and its ability to be spread by aerosol dispersion or by contaminated food or milk. It has the advantage of being debilitating to people without being fatal. Its development as a biological weapon was stopped in 1967, and later President Nixon banned development of all biological weapons on November 25, 1969.

Causative Agent (Pathogen) A contagious bacterial disease: Br. abortuscattle and bison Br. suisswine Br. canisdogs Br. melitensissheep and goats

Brucellosis only occasionally affects horses and cats are relatively resistant to the infections. Depending upon how an animal contracts brucellosis, a different species of Brucella may be causing the infection. For example: pigs, sheep and goats that are in contact with infected cattle can be infected with Br. abortus. Dogs that ingest placentas from farm animals may be infected with Br. abortus, Br. susis, and Br. melitensis.

Brucella spp. Are a gram negative coccobacilli ( rods that are so short that they resemble cocci ) The bacteria infect the placenta, uterus and fetus, causing abortion in females. It also infects the testes and accessory sex glands causing orchitis and accessory sex gland infection in males. It can cause infertility in both sexes. Br. Abortus and Br. Canis cause mild disease in humans, whereas Br. Suis and Br. Melitensis can be fatal.

Brucellosis has a worldwide distribution and can affect a variety of animals. In the United States and Europe brucellosis is uncommon as a result of its elimination from cattle herds. Br. melitensis * in sheep and goats represents the most important source of brucellosis in humans * it is not enzootic in the United States, Canada, northern Europe, Australia, or Souteast Asia * prevalent in Latin American, Mediterranean area, Central Asia and the countries around the Arabian Gulf. * Humans are infected by the handling of animals during the birthing process and the consumption of raw milk products (especially fresh soft cheeses)

Br. suis * affects both sexes of swine * causes infertility, abortion, orchitis, bone/joint lesions * prevalence is generally low * occurs in areas in which pigs are kept, including southeastern United States and Australia where populations of feral swine are heavily infected. * Human infections occur in people handling pigs on farms and during slaughtering and processing feral and domestic swine.

Br. abortus * has been eradicated from Canada, Japan, northern Europe and Australia * Cases in humans are sporadic and are acquired by: drinking unpasteurized milk working with infected cattle at a slaughter facility by attending infected parturient cattle accidental inoculation with live vaccine

Br. Canis * infection in humans tends to occur in dog handlers In the United States, the frequency of brucellosis is related to the number of infected animals. Infected animals are rare in the United States and pasteurization of milk has eliminated that mode of transmission Occupational exposure (cattle-workers, veterinarians, slaughterhouse workers) is the main transmission route in the United states. The incidence is approximately 200 cases per year. People with Brucellosis in the United States are primarily found in Texas, California, Virginia and Florida

Pathogenesis Once in the body, Brucella spp. are engulfed by neutrophils and are carried In the lymphatic fluid to the lymph nodes draining the infected area. The infected neutrophils release bacteria into the blood and bacteria localize in certain organs. liver spleen bone marrow kidney The gross lesions seen in an animal are subtle and rarely diagnostic.

In cows, placental lesions include: edema necrosis brownish odorless discharge In aborted bovine fetuses: edema bronchopneumonia In bulls: scrotum becomes enlarged and thickened

In swine: formation of white nodules on the uterus of females formation of white nodules on the testes of males lesions in both sexes of the spleen, liver, kidney, lymph nodes and bone In sheep: edema and inflammation of the epididymis in rams necrosis of the placenta in ewes inflammatory changes in the lung, liver, lymph nodes spleen and kidneys of lambs

In dogs: uterine and placental lesions in females orchitis in males bronchopneumonia in pups The incubation period of brucellosis is variable ranging from 2 weeks to 1 year or longer. Note: the typical length is 30 to 60 days.

Diagnosis in Animals Tissues infected with Brucella spp. do not provide distinctive findings. Diagnosis in animals consists of bacteriologic or serologic identification. Treatment in Animals Treatment of infected animals is not attempted because animals may recover from the disease signs but do not clear the infection. Management and Control in Animals Measures for prevention and control of brucellosis include vaccination of calves, periodic testing of bulk milk from farms, blood testing of adults and slaughtering of infected animals.

In the United States a federal program for brucellosis eradication called the Cooperative State Federal Brucellosis Eradication Program has existed since States are deemed brucellosis free when none of their cattle or bison is found to be infected for 12 consecutive month under an active surveillance program. Clinical Signs in Humans Brucella spp. are able to establish an infection by surviving phagocytosis and are passed from the lymph to blood and then to organs throughout the body. The organs mainly affected are the liver, spleen, and bone marrow. In humans the incubation period is typically 5 to 60 days (or longer)

The most prominent symptoms are; weakness loss of appetite chills headache back pain intermittent (undulating) fever It persists for weeks to months if left untreated. Chronic infection can damage joints and the spinal cord.

Diagnosis in Humans Diagnosis is primarily dependent on: clinical suspicion adequate history of possible exposure (including travel) isolation of the organism Brucellosis in humans is very hard to diagnose. An undeniable diagnosis requires isolation of the organism using blood culture as the method of choice. Culture from bone marrow, blood and affected organs may be successful.

Treatment in Humans Humans are treated with antibiotic combinations for 4 to 6 weeks. No widely accepted vaccines for humans have been developed. All material taken directly from Understanding Zoonotic Diseases by Janet Amundson Romich published by Thomson/Delmar Learning.