Geographical repartition of Brucella abortus for domestic and wild animals between july and december 2010
Brucellosis is a contagious animal disease of bacterial origin (genus Brucella) that mainly affects ruminant animals but also humans, pigs or dogs.
The disease causes loss of animal productions and has an important economical impact. It is one of the most important serious diseases of Livestock and it must be notified to OIE.
Enzootic disease in many parts of the world including the Caribean.
The disease mainly affects ruminant animals (cattle, bison, buffaloes, goats, sheep). Swines, humans and dogs can also be affected. Isolates of Brucella have recently also been discovered in marine mammals.
Farmers, ranchers, veterinarians, and packing plant workers are infected more frequently because they come into direct contact with infected animals.
The disease is caused by a Gram negative, intracellular bacteria of the genus Brucella. Each Brucella species is associated with certain hosts.Six species occurs in animals : B. brucella, B. melitensis, B. ovis, B. suis, B. canis and B. neotomae.
B. abortus usually causes Brucellosis in cattle, buffalo and bison
B. suis mainly affects swine and reindeer but also cattle and bison
B. melitensis is the most important species found in sheep and goats. B. ovis can cause infections in sheep and rams.
B. canis affects dogs and B. neotomae affects rodents.
• Animals
Abortion (10 to 15% of cases) occurs during the second half of pregnancy in ruminants, usually between the fifth and seventh month of gestation. However, in pigs, abortion occurs at any stage of gestation.
Infected cows usually abort once (75 to 90% of cases), but a percentage will abort during additional pregnancies, and calves born from later pregnancies may be weak and unhealthy.
So, the most obvious signs are reproductive troubles. Abortions, stillbirths, infertility, orchitis, retained afterbirths with resulting uterine infections, articular and peri-articular hygromas, especially in the tropics, characterize the disease. Milk production may be reduced in cattle caused by abortions and delayed conceptions.
Even though their calves may appear healthy, infected cows continue to harbor and discharge infectious organisms and should be regarded as dangerous sources of the disease.
• Humans
The incubation period lasts from 5 days to 3 months. Most infections become apparent within 2 weeks.
Brucellosis is a multisystemic disease. It typically starts with acute febrile illness that can last 2 to 4 weeks. Most people recover but some people may develop other forms of the disease.
Three possible forms:
- Undulant form (Malta fever) intermittent fever with other persistent symptoms that wax and wane at regular intervalls
- Subacute or localized form: affecting any organ (testes, heart, lungs, joints ...)
- Chronic form: no fever, characterized by high fatigue, musculoskeletal pain, neurological signs (5% of cases)
In pregnancy, brucellosis can cause acute abortion or premature labor.
Undulant fever does not often kill its victims, but the disease is too serious to be dealt with lightly.
• animals
No treatment. Repeated attempts to develop a cure for brucellosis in animals have failed. Occasionally, animals may recover after a period of time. More commonly, however, only the signs disappear and the animals remain infected. Such animals are dangerous sources of infection for other animals with which they associate.
• humans
it is important to implement early treatment to prevent chronic infection.
Using tetracycline and rifampicin often associated with streptomycin chloramphenicol and sulfonamides (WHO recommends rifampicin 600mg / d and doxycycline 200 mg / d). The treatments are suitable if the patient is a pregnant woman or a young child. The treatment lasts about 6 weeks for brucellosis phase tank. Phase focused, treatment lasts from 2 to 4 months because the majority of bacteria are located in the cells and is then more difficult of access to drugs.
Sanitary prophylaxis
Animals
Compliance with hygiene and quarantine. detection and elimination of positive animals
Humans
Pasteurization of dairy products
Good hygiene and protective clothing to avoid contamination of the skin
Live attenuated vaccine strain of B. melitensis Rev-1. It can cause abortions and interfere with serological tests.
Two B. abortus attenuated vaccines can be used in endemic areas, the strain 19 and the strain RB51. The second one induces less abortions than the first one but it is less effective when challenged with heavy dose of the bacteria.
The B. suis strain 2 vaccine has not yet received agreement for commercialization.