brucellosis(redirected from undulating fever)
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An infectious, zoonotic disease of various animals and humans caused by Brucella species. Each species tends to preferentially infect a particular animal, but several types can infect humans. Brucella melitensis (preferentially infects goats and sheep), B. suis (infects pigs), and B. abortus (infects cattle) are the most common causes of human brucellosis. Brucella melitensis is the most virulent for humans, followed by B. suis and B. abortus. Brucella canis and B. ovis, which infect dogs and sheep respectively, rarely infect humans. Although brucellosis is found all over the world, in many countries the disease has been eradicated. The brucellae are small, gram-negative coccobacilli which are defined as facultative intracellular parasites since they are able to replicate within specialized cells of the host.
In animals the brucellae often localize in the reproductive tract, mammary gland, and lymph node. They have a particular affinity for the pregnant uterus, leading to abortion and reduced milk production with resultant economic loss to the farmer. Wildlife, including elk, feral pigs, bison, and reindeer, can become infected and can spread the disease to domestic livestock.
Brucellosis in humans is characterized by undulant fever, cold sweats, chills, muscular pain, and severe weakness. Some individuals may have recurrent bouts of the disease in which a variety of organs may be affected, sometimes resulting in death. The disease can be contracted by consuming unpasteurized milk or cheese, or via the introduction of organisms through small skin lesions or as an aerosol through the conjunctiva and the respiratory system. Treatment with tetracycline and other antibiotics is most successful if started early after symptoms occur. Development of the disease can be prevented if treatment is initiated immediately after contact with potentially infected material.
At present there are no effective vaccines for humans. The disease can be eliminated only by eradicating it in animals. A major source of brucellosis in humans is the consumption of B. melitensis–infected milk and cheese from goats. Incidence can be reduced by pasteurizing milk. Animals can be vaccinated to increase their immunity against brucellosis and therefore reduce abortions and disease transmission. See Epidemiology, Medical bacteriology
or Malta fever, or Bang’s disease, a generalized acute or chronic infectious-allergic disease of man and animals. It is characterized by multiformity of clinical manifestations; a prolonged course; and affection of the nervous system, bones, and joints. The causative agents of brucellosis are Brucella microorganisms of three species: B. melitensis, found in goats and sheep; B. abortus, found in cattle; and B. suis, found in swine.
All species of animals and humans may become infected from diseased goats, sheep, cattle, and swine. The principal source of infection is diseased animals, from which Brucella organisms are shed during abortion with the fetus and uterine secretions and with the afterbirth, milk, urine, and feces.
Humans become infected when using Brucella-infected milk, milk products (including insufficiently ripened brynza), and meat (that was not cooked sufficiently) from animals ill with brucellosis and also when caring for sick animals, cleaning the premises of infected cattle, or giving help to an animal whose fetus has been aborted. (The fetus and amniotic fluid are very infectious.) The causative agents of brucellosis may also penetrate the human body through a wound in the skin or the mucous membranes (abrasions, scratches, and so on) or through the respiratory tract. Upon entering the body, the Brucella organisms stay for a short time in the lymph nodes, then enter the bloodstream, and are carried with the blood to various tissues and organs, where they evoke defensive reactions in response. Along with this, there occurs an immunologic reorganization of the body, and the body acquires an increased sensitivity to Brucella organisms and to their metabolic products (the body is sensitized); an allergy develops. All organs and tissues may be affected by brucellosis. There are known to be brucellotic endocarditides, aortitides, thrombophlebitides, pleurisies, and bronchoadenitides. In men the testes may be affected (orchitides, epididymitides); in women, the fallopian tubes (salpingitides), ovaries (oophoritides), and uterus (metritides). Abortions often occur; moreover, pregnancy aggravates the course of brucellosis. Most often the support-motor apparatus is affected—joints, tendons, and ligaments. In typical cases the disease manifests itself after two or three weeks (incubation period). The temperature increases to 39°-40° C, and intense sweats occur. Subsequently, the fever is intermittent: after a two-week to three-week fever period, there is a fever-free period. There may be up to six or seven such waves. Soreness is observed in the lumbar region and in the neck muscles; there is enlargement of the liver and spleen. In patients who do not receive treatment the lymph nodes may become enlarged. From the end of the first month to the beginning of the second month of illness, one or another large joint is affected; pain appears upon movement or while the person is at rest, soft tissues surrounding the joint swell, and the contours of the joint are leveled out. The course of the illness is long (about three months and sometimes as long as two or more years), and there are recurrences. As a result of affection of the joints, movement in them may be sharply curtailed (contractures), which leads to invalidism. Brucellosis is diagnosed on the basis of symptoms of the disease, ascertaining the causes and conditions of infection (epidemiologic data), and also through laboratory tests (Wright-Huddleston reaction, allergic skin test of Burnet).
Treatment in the acute period and during recurrences consists of antibiotics; for a chronic course with recurrences, of vaccino-therapy and antibiotics. For residual symptoms health-spa treatment is recommended. Prophylaxis consists in observing measures for preventing infection when there is contact with sick animals or use of their milk products or meat. Vaccination is another preventive measure.
REFERENCESRudnev, G. P. Zoonozy, 2nd ed. Moscow, 1959.
Bunin, K. V. Diagnostika infektsionnykh boleznei. Moscow, 1965.
K. V. BUNIN
In animals, the causative agent most often enters through the digestive tract along with food and water; it can also enter through the mucous membranes and the skin. Pigs and sheep most often become infected via the sexual organs during mating. Brucellosis infection may occur from using pastures and watering facilities previously used by sick animals. The infection can also be spread by persons tending the animals.
Upon entering an animal’s organism, the Brucella organisms establish themselves and multiply, chiefly in the pregnant uterus, the udder, spleen, lymph nodes, bone marrow, and seminal glands. Abortion is the chief symptom. During the first years that brucellosis appears on a farm, many animals (20 to 50 percent and more) abort; later, only isolated cases of abortion occur. Other symptoms observed in sick animals include retention of the afterbirth; inflammation of the uterus, udder, and joints; inflammation of the testes in males; and purulent swellings on the back of the neck and around the withers in horses. The disease often develops without clinical symptoms, which is why brucellosis is diagnosed by special methods, such as bacteriological methods (isolating the pathogen), serological methods (studying the animals’ blood serum), and the use of allergic reactions (introducing preparations made with Brucella organisms into the skin).
Brucellosis occurs in almost all countries of the world and causes great economic losses, since it reduces the number of offspring and the productivity of animals. Considerable sums are spent on measures to prevent brucellosis. Treatment for sick animals has not been developed. Vaccines developed from live weakened Brucella organisms, with which calves and lambs could be inoculated, have been suggested as prophylaxis. Individual and organizational measures are being implemented to protect those farms still free of brucellosis and to rid affected farms of the disease. The greatest attention is being focused on detecting and slaughtering sick animals, raising healthy young stock in isolation, and destroying the brucellosis pathogen in the environment. In the USSR systematic antibrucellosis measures are being carried out to liquidate and prevent brucellosis in animals.
REFERENCESIuskovets, M. K. Brutsellez sel’skokhoziastvennykh zhivotnykh. Moscow, 1960.
Orlov, E. S. “Brutsellez.” In Veterinarnaia entsiklopediia, vol. 1. Moscow, 1968.