Brucella is a small, gram-negative microbe that is non-motile and has non-spore forming rods. It functions as a facultative intercellular parasite that causes chronic disease and will usually persists for life. Human symptoms are recognized by profuse sweating and muscle and joint pain. Brucellosis has been recognized in animals and humans since the 19th century.
Brucellosis, when first discovered, went by the name of Malta fever. It first came to the attention of British medical officers in Malta during the Crimean war in the mid 1850’s. The relationship between organisms and the disease was first established in 1887 by Dr David Bruce. In 1897, Danish veterinarian Bernhard Bang isolated Brucella abortus as the agent “Bangs disease”. Maltese doctor and archeologist Sir Themistocles Zammit earned his knighthood for recognizing unpasteurized milk as the major source of the pathogen in 1905.
The species of the Brucella, Brucella abortus, is the main cause of brucellosis in cattle and bison. The bacteria are shed from an animal around the time of calving or pregnancy. Once exposed, the likelihood the animal becoming infected is variable depending on age, pregnancy status, and the amount of bacteria the animal was exposed to. The most common signs in animals are incidences of abortion, arthritic joints, and retained afterbirth. There are primarily two main causes of abortion in animals. One is due to the build up of erythritol which promotes infections in the fetus and the placenta. The second is due to lack of anti-brucella activity in the amniotic fluid during pregnancy. Males can harbor the bacteria in reproductive tracts like the testicles, epididymides, and seminal vesicles.
Dairy herds in the US are tested at least once a year with a Brucella milk ring test (BRT). Cows that are found to be infected are often killed and disposed of. US veterinarians are required to vaccinate calves, thereby reducing the chance of zoonotic transmission. This is referred to as a “calfhood” vaccination. Most cattle will receive a tattoo in the ear after receiving the vaccination.
Canada declared their entire cattle herd brucellosis free on September 19th, 1985. Ring tested ended shortly after in April of 1999 but monitoring still continues in auction markets. The first US state-federal cooperative efforts toward eradication of brucellosis were put into effect in 1934.
Brucellosis has infected Ireland for decades. Farmers and veterinarians were bothered by the disease from the interaction with the livestock. Ireland was declared free of the disease on July 1, 2009. Brendan Smith, Minister of Irelands agriculture, fisheries and food, quoted that the elimination of the disease from the country was “a landmark in the history of disease eradication in Ireland”
Outbreaks of Brucella abortus and BSE in cattle, Cork RVL, 1990-2003.
Along with livestock, dogs can also be infected by the genus Brucella. The species that affects dogs is Brucella canis. The disease is transmitted to other dogs though breeding and contact with aborted fetuses. The bacteria can harbor in the dogs genitals and lymphatic system and may also spread to the eyes, kidneys, and intervertebral discs. Systems in dogs consist of abortions in females and males show signs of scrotal inflammation and orchitis (inflammation of the testicles.
One of the last remaining controversial hot spots for brucellosis is Yellowstone National Park in Montana and Wyoming. The bison and elk that roam free in and around Yellowstone are said to be the last remaining reservoirs for...