Brucellosis

                       

Brucellosis

Brucellosis
Classification and external resources

Brucellosis, also called Bang's disease, Crimean fever, Gibraltar fever, Malta fever, Maltese fever, Mediterranean fever,rock fever, or undulant fever,^[1][2] is a highly contagious zoonosis caused by ingestion of unpasteurized milk or undercooked meatfrom infected animals or close contact with their secretions. Transmission from human to human, through sexual contact or from mother to child, is rare but possible.^[3]

Brucella species are small, Gram-negative, nonmotile, nonspore-forming, rod-shaped (coccobacilli) bacteria. They function asfacultative intracellular parasites, causing chronic disease, which usually persists for life. Symptoms include profuse sweating and joint and muscle pain. Brucellosis has been recognized in animals, including humans, since the 20th century. 

Signs and symptoms

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 the first stage of the disease, septicaemiaoccurs and leads to the classic triad of undulant fevers, sweating (often with characteristic smell, likened to wet hay), and migratoryarthralgia and myalgia (joint and muscle pain). Blood tests characteristically reveal leukopenia and anemia, show some elevation of AST and ALT, and demonstrate positive Bengal Rose and Huddleston reactions.

This complex is, at least in Portugal, known as Malta fever. During episodes of Malta fever, melitococcemia (presence of brucellae in blood) can usually be demonstrated by means of blood culture in tryptose medium or Albini medium. If untreated, the disease can give origin to focalizations or become chronic. The focalizations of brucellosis occur usually in bones and joints and spondylodiscitis of the lumbar spine accompanied by sacroiliitis is very characteristic of this disease. Orchitisis also common in men.

Diagnosis of brucellosis relies on:

1. Demonstration of the agent: blood cultures in tryptose broth, bone marrow cultures. The growth of brucellae is extremely slow (they can take up to two months to grow) and the culture poses a risk to laboratory personnel due to high infectivity of brucellae.
2. Demonstration of antibodies against the agent either with the classic Huddleson, Wright, and/or Bengal Rose reactions, either with ELISA or the 2-mercaptoethanol assay for IgM antibodies associated with chronic disease
3. Histologic evidence of granulomatous hepatitis on hepatic biopsy
4. Radiologic alterations in infected vertebrae: the Pedro Pons sign (preferential erosion of the anterosuperior corner of lumbar vertebrae) and marked osteophytosis are suspicious of brucellic spondylitis.

The disease's sequelae are highly variable and may include granulomatous hepatitis, arthritis, spondylitis, anaemia, leukopenia, thrombocytopenia, meningitis, uveitis, optic neuritis, endocarditis, and various neurological disorders collectively known as neurobrucellosis.

Cause

Granuloma and necrosis in the liver of a guinea pig infected with Brucella suis

Brucellosis in humans is usually associated with the consumption of unpasteurized milk and soft cheeses made from the milk of infected animals, primarily goats, infected with Brucella melitensis and with occupational exposure of laboratory workers, veterinarians, and slaughterhouse workers. Some vaccines used in livestock, most notably B. abortus strain 19, also cause disease in humans if accidentally injected. Brucellosis induces inconstant fevers, miscarriage, sweating, weakness, anaemia, headaches, depression, and muscular and bodily pain. The other strains are Brucella suis and Brucella canis, which cause infection in pigs and dogs respectively.

Treatment and prevention

Antibiotics such as tetracyclines, rifampicin, and the aminoglycosides streptomycin and gentamicin are effective against Brucella bacteria. However, the use of more than one antibiotic is needed for several weeks, because the bacteria incubate within cells.

The gold standard treatment for adults is daily intramuscular injections of streptomycin 1 g for 14 days and oral doxycycline 100 mg twice daily for 45 days (concurrently). Gentamicin 5 mg/kg by intramuscular injection once daily for seven days is an acceptable substitute when streptomycin is not available or contraindicated.^[4] Another widely used regimen is doxycycline plus rifampin twice daily for at least six weeks. This regimen has the advantage of oral administration. A triple therapy of doxycycline, with rifampin and co-trimoxazole, has been used successfully to treat neurobrucellosis.^[5]

Doxycycline is able to cross the blood–brain barrier, but requires the addition of two other drugs to prevent relapse. Ciprofloxacin and co-trimoxazole therapy is associated with an unacceptably high rate of relapse. In brucellic endocarditis, surgery is required for an optimal outcome. Even with optimal antibrucellic therapy, relapses still occur in 5 to 10% of patients with Malta fever.

The main way of preventing brucellosis is by using fastidious hygiene in producing raw milk products, or by pasteurizing all milk that is to be ingested by human beings, either in its unaltered form or as a derivate, such as cheese. Co-trimoxazole and rifampin are both safe drugs to use in treatment of pregnant women who have brucellosis.^{[citation needed]}

Prognosis

With combination drug therapy, most individuals recover in two to three weeks. Even widespread infections may be cured. Untreated, however, the infection may progress and increase in severity and also affect new tissues. Although brucellosis can take a chronic form, with periods of illness alternating with periods of no symptoms, persistent illness lasting longer than two months may be due to a previously unsuspected underlying disease or a complication of the brucellosis.

About 10% of individuals may have a relapse, even after treatment is completed. In these cases, treatment should be repeated. This disease has a mortality rate lower than 2%; the most likely cause of death is endocarditis caused by Brucella melitensis.

Biological warfare

In 1954, B. suis became the first agent weaponized by the United States at its Pine Bluff Arsenal near Pine Bluff, Arkansas. Brucella species survive well in aerosols and resist drying. Brucella and all other remaining biological weapons in the U.S. arsenal were destroyed in 1971–72 when the American offensive biological warfare program was discontinued by order of President Richard Nixon.^[6]

The experimental American bacteriological warware program focused on three agents of the Brucella group:

• Porcine brucellosis (agent US)
• Bovine brucellosis (agent AB)
• Caprine brucellosis (agent AM)

Agent US was in advanced development by the end of World War II. When the U.S. Army Air Forces (USAAF) wanted a biological warfare capability, the Chemical Corps offered Agent US in the M114 bomblet, based on the four-pound bursting bomblet developed for spreading anthrax during World War II. Though the capability was developed, operational testing indicated the weapon was less than desirable, and the USAAF designed it as an interim capability until it could replaced by a more effective biological weapon.

The main drawbacks of the M114 with Agent US was that it was an incapacitating agent, whereas the administration of the USAAF wanted deadly weapons. Also, the stability under storage was too low to allow for storing at forward air bases, and the logistical requirements to neutralize a target were far higher than originally planned. This would have required an unreasonable amount of logistical support.

Agents US and AB had a median infective dose of 500 organisms/person, and for Agent AM it was 300 organisms/person. The time-of-incubation was believed to be about two weeks, with a duration of infection of several months. The lethality estimate was based on epidemiological information at 1 to 2%. Agent AM was believed to be a more virulent disease, and a fatality rate of 3% was expected.

History

Under the name "Malta fever", the disease now called brucellosis first came to the attention of British medical officers in the 1850s in Malta during the Crimean War. The causal relationship between organism and disease was first established in 1887 by David Bruce.^[7][8]

In 1897, Danish veterinarian Bernhard Bang isolated Brucella abortus as the agent; and the additional name "Bang's disease" was assigned.

Maltese doctor and archaeologist Sir Themistocles Zammit earned a knighthood for identifying unpasteurized milk as the major source of the pathogen in 1905, and it has since become known as Malta fever. In cattle, this disease, usually caused by B. abortus, is also known as "contagious abortion" and "infectious abortion".

The popular name "undulant fever" originates from the characteristic undulance (or "wave-like" nature) of the fever, which rises and falls over weeks in untreated patients. In the 20th century, this name, along with brucellosis (after Brucella, named for Bruce), gradually replaced the 19th century names Mediterranean fever and Malta fever.

In 1989, neurologists in Saudi Arabia discovered "neurobrucellosis", a neurological involvement in brucellosis.^[9][10]

The following obsolete names have previously been applied to brucellosis:

• Brucelliasis
• Bruce's septicemia
• Chumble fever
• Continued fever
• Crimean fever
• Cyprus fever
• Febris melitensis
• Febris undulans
• Fist of mercy
• Goat fever
• Melitensis septicemia
• Melitococcosis
• Milk sickness
• Mountain fever
• Neapolitan fever
• Satan's fever
• Slow fever
• Scottish delight
• Jones disease
• Contagious abortion
• Maltese fever

Eradication efforts

United States

Dairy herds in the USA are tested at least once a year^{[citation needed]} with the Brucella milk ring test (BRT).^[11] Cows confirmed to be infected are often killed. In the United States,veterinarians are required^{[citation needed]} to vaccinate all young stock, thereby further reducing the chance of zoonotic transmission. This vaccination is usually referred to as a "calfhood" vaccination. Most cattle receive a tattoo in their ear serving as proof of their vaccination status. This tattoo also includes the last digit of the year they were born.^[12]

The first state–federal cooperative efforts towards eradication of brucellosis caused by Brucella abortus in the U.S. began in 1934.

Greater Yellowstone area

Wild bison and elk in the Greater Yellowstone Area (GYA) are the last remaining reservoir of B. abortus in the US. The recent transmission of brucellosis from elk to cattle in Idaho and Wyoming illustrates how the GYA, as the last remaining reservoir in the United States, may adversely affect the livestock industry. Eliminating brucellosis from this area is a challenge, as many viewpoints exist on how to manage diseased wildlife.

Canada

The Canadian government declared its cattle population to be brucellosis-free on 19 September 1985. The brucellosis ring testing of milk and cream, as well as the testing of cattle to be slaughtered, ended on 1 April 1999. Monitoring continues through testing at auction markets, through standard disease-reporting procedures, and through the testing of cattle being qualified for export to countries other than the United States.^[13]

Europe

Disease incidence map of Brucella melitensis infections in animals in Europe during the first half of 2006.

  never reported

  not reported in this period

  confirmed clinical disease

  confirmed infection

  no information

Malta

Until the early 20th century, the disease was endemic in Malta to the point of it being referred to as "Maltese fever". The link between the illness and unpasteurised milk was established by Temi Zammit. Today, due to a strict regimen of certification of milk animals and widespread use of pasteurization, the illness has been eradicated from Malta.^[14]

Republic of Ireland

Ireland was declared free of brucellosis on 1 July 2009. The disease had troubled the country's farmers and veterinarians for several decades.^[15][16] The Irish government submitted an application to the European Commission, which verified that Ireland had been liberated.^[16] Brendan Smith, Ireland's then Minister for Agriculture, Food and the Marine, said the elimination of brucellosis was "a landmark in the history of disease eradication in Ireland".^[15][16] Ireland's Department of Agriculture, Food and the Marine intends to reduce its brucellosis eradication programme now that eradication has been confirmed.^[15][16]

Oceania

Australia

Australia is free of cattle brucelosis, although it occurred in the past. Brucellosis of sheep or goats has never been reported. Brucellosis of pigs does occur. Feral pigs are the typical source of human infections.^[17] [18]

New Zealand

Brucellosis in New Zealand is limited to sheep (B. ovis). The country is free of all other species of Brucella.^[19]

Other animals

Species infecting domestic livestock are B. melitensis (goats and sheep), B. suis (pigs), B. abortus (cattle and bison), B. ovis (sheep), and B. canis (dogs). B. abortus also infects bison and elk in North America and B. suis is endemic in caribou. Brucella species have also been isolated from several marine mammal species (pinnipeds and cetaceans).

Brucellosis in cattle

Brucella abortus is the principal cause of brucellosis in cattle. The bacteria are shed from an infected animal at or around the time of calving or abortion. Once exposed, the likelihood of an animal becoming infected is variable, depending on age, pregnancy status, and other intrinsic factors of the animal, as well as the number of bacteria to which the animal was exposed.^[20] The most common clinical signs of cattle infected with B. abortus are high incidences of abortions, arthritic joints, and retained placenta.

The two main causes for spontaneous abortion in animals are erythritol, which can promote infections in the fetus and placenta, and the lack of anti-Brucella activity in the amniotic fluid. Males can also harbor the bacteria in their reproductive tracts, namely seminal vesicles, ampullae, testicles, and epididymes.

Brucellosis in dogs

The causative agent of brucellosis in dogs, B. canis, is transmitted to other dogs through breeding and contact with aborted fetuses. Brucellosis can occur in humans who come in contact with infected aborted tissue or semen. The bacteria in dogs normally infect the genitals and lymphatic system, but can also spread to the eyes, kidneys, and intervertebral discs. Brucellosis in the intervertebral disc is one possible cause of discospondylitis. Symptoms of brucellosis in dogs include abortion in female dogs and scrotal inflammation andorchitis in males. Fever is uncommon. Infection of the eye can cause uveitis, and infection of the intervertebral disc can cause pain or weakness. Blood testing of the dogs prior to breeding can prevent the spread of this disease. It is treated with antibiotics, as with humans, but it is difficult to cure.^[21]

Brucellosis in Cetaceans

Brucellosis is caused by the bacteria Brucella ceti. First discovered in the aborted fetus of a bottle nose dolphin, the structure of Brucella ceti follows a similar structure of Brucella bacteria in land animals. Brucella ceti is commonly detected in two suborders of cetaceans, Mysticetia and Odontoceti. Mysticetia includes four families of baleen whales, filter-feeders and Odontoceti includes two families of toothed cetaceans ranging from dolphins to sperm whales. It is believed that B. Ceti is transferred from animal to animal through sexual intercourse, maternal feeding, aborted fetuses, placental issues, from mother to fetus or through fish reservoirs. B. ceti causes a disease known as brucellosis. Brucellosis is a reproductive disease and therefore has an extreme negative impact on the population dynamics of a species. This becomes even a greater issue when the already low population numbers of cetaceans are taken into consideration. Brucella ceti has been identified in four out of the fourteen cetacean families, but the antibodies have been dedicated in seven of the families. This indicates that Brucella ceti is common amongst cetacean families and populations. Only a small percentage of exposed individuals become ill or die; yet this disease affects half of cetacean families. However, particular species, it appears, are more likely to become infected by Brucella ceti. The harbor porpoise, striped dolphin, white-sided dolphin, bottlenose dolphin and the common dolphin are the species with the highest frequency of infection amongst ondontocetes. In the mysticetes family, the northern minke whale is by far the most infected species. Evidence indicates that dolphins and porpoises are more likely to be infected than cetaceans such as whales. With regard to gender and age biases, the bruceel ceti infections do not seem to be influenced by the age or gender of an individual. Although fatal to cetaceans, Brucella ceti has a low infection rate for humans.