Brucellosis – Causes, Symptoms and Diagnosis

Brucellosis, also called undulant fever, or Malta fever, in humans is a highly contagious zoonosis (infectious disease transmitted from animals to humans) caused by bacteria of the genus Brucella. Brucella spp. are small, gram-negative, non-motile, non-spore-forming rods. Brucella spp. are facultative intracellular parasites causing chronic disease, which usually persists for life. Brucellosis is a bacterial disease of both humans and animals recognized since the 19th century.

Brucella are rod-shaped bacteria that lack a capsule around their cell membranes. Unlike most bacteria, Brucella cause infection by actually entering host cells. As the bacteria cross the host cell membrane, they are engulfed by host cell vacuoles called phagosomes. The presence of Brucella within host cell phagosomes initiates a characteristic immune response, in which infected cells begin to stick together and form aggregations called granulomas.

Brucellosis is an infectious disease caused by the bacteria of the genus Brucella. These bacteria are primarily passed among animals, and they cause disease in many different vertebrates. Various Brucella species affect sheep, goats, cattle, deer, elk, pigs, dogs, and several other animals. Humans become infected by coming in contact with animals or animal products that are contaminated with these bacteria. In humans brucellosis can cause a range of symptoms that are similar to the flu and may include fever, sweats, headaches, back pains, and physical weakness.

Causes

Brucella can infect cattle, goats, camels, dogs, and pigs. The bacteria can spread to humans if you come in contact with infected meat or the placenta of infected animals, or if you eat or drink unpasteurized milk or cheese. Brucellosis is rare in the United States (except in the western states). Approximately 100 - 200 cases occur in the U.S. each year. People working in jobs requiring frequent contact with animals or meat -- such as slaughterhouse workers, farmers, and veterinarians -- are at high risk.

Symptoms

Symptoms of brucellosis include intermittent or irregular fever of variable duration, headache, weakness, profuse sweating, chills, weight loss and generalized aching. Brucellosis can also cause long-lasting or chronic symptoms such as recurrent fevers, joint pain and fatigue.

The symptoms are like those associated with many other febrile diseases, but with emphasis on muscular pain and sweating. The duration of the disease can vary from a few weeks to many months or even years. In first stage of the disease, septicaemia occurs and leads to the classic triad of undulant fevers, sweating (often with characteristic smell, likened to wet hay) and migratory arthralgia and myalgia. In blood tests, is characteristic the leukopenia and anaemia, some elevation of AST and ALT and positivity of classic Bengal Rose and Huddleson reactions

This intermittent fever usually lasts 1 to 5 weeks, after which symptoms usually subside or disappear for two days to two weeks. Then the fever recurs. In some patients, this fever recurs only once. In others, the disease becomes chronic, and the fever recurs, subsides, and then recurs again repeatedly over months or years.

Diagnosis

Brucellosis is diagnosed in a laboratory by finding Brucella organisms in samples of blood or bone marrow. Also, blood tests can be done to detect antibodies against the bacteria. If this method is used, two blood samples should be collected 2 weeks apart.