Brucellosis is a contagious, costly disease of ruminant animals which also affects humans. Although brucellosis can attack other animals, its main threat is to swine, cattle, and bison. This disease is also known as contagious abortion or Bang%26rsquo;s disease. In humans, it's known as undulant fever because of the severe intermittent fever it causes. This fever is accompanying human infection, also known as Malta fever because it was first recognized as a human disease on the island of Malta.Should we be afraid of brucellosis?
Considering the damage done by the infections in animals, this must be considered as one of the most serious livestock diseases. In animals, brucellosis can cause a decreased milk production, weight loss, loss of young, infertility, and lameness. This disease can spread very rapidly, and is transmissible to humans. These facts make it all the more serious.
What can cause brucellosis?
Brucellosis is caused by a group of bacteria known scientifically as the genus Brucella. There are three species of Brucella that cause the most concern. Those are B. abortus, principally affecting cattle and bison, B. suis, principally affecting swine and reindeer but also cattle and bison, and B. melitensis, principally affecting goats. In cattle and bison, the disease currently localizes in the reproductive organs. Bacteria are shed in milk or via the aborted fetus, afterbirth, or other reproductive tract discharges of the affected animal.
Signs and symptoms of brucellosis
There is no effective way to detect infected animals by symptoms of brucellosis. The most obvious signs in pregnant animals are abortion or birth of weak calves. Milk production may be reduced from changes in the normal lactation period. This is caused by abortions and delayed conceptions. It is not true that all infected cows abort.
However, those that do abort, usually abort between the fifth and seventh month of pregnancy.
Infected cows usually abort once, but a percentage will abort during additional pregnancies too. Calves born from later pregnancies may be weak and unhealthy due to brucellosis. Even though their calves may appear healthy, infected cows continue to harbor and discharge infectious organisms. Those animals should be regarded as dangerous sources of the disease. Other symptoms of brucellosis include an apparent lowering of fertility with poor conception rates. It is retained after births with consequential uterine infections and occasionally enlarged, arthritic joints.
How does brucellosis spread?
Brucellosis is commonly transmitted onto susceptible animals by direct contact with infected animals. It can also transmit through an environment that has been contaminated with discharges from infected animals. Aborted fetuses, placental membranes or fluids, and other vaginal discharges present after an infected animal has aborted or calved are all highly contaminating as well. These discharges and fluids have a lot of Brucella organisms. Cows commonly lick those materials or the genital area of other cows. Cows could also ingest the disease-causing organisms with contaminated food or water. Despite occasional exceptions, the general rule is that brucellosis is carried from one herd to another by an infected animal. This mode of transmission occurs when a herd owner buys replacement cattle or bison that are infected. It could also happen when the owner%26rsquo;s animals were exposed to infection prior to purchase. The disease may also be spread when wild animals or animals from an affected herd mingle with brucellosis-free animals.
How to fight brucellosis?
In the past, brucellosis control was limited mainly to individual herds. These days there is a Cooperative State Federal Brucellosis Eradication Program working to eliminate the disease from the entire country. Like other animal disease-eradication efforts, the success of the program depends on the support and participation of each livestock producer. States are designated brucellosis-free when none of their cattle or bison is found to be infected for 12 consecutive months. The question is, how do epidemiologists help fight brucellosis? Epidemiologists are specially trained veterinarians who investigate disease sources and the means of eliminating infection in affected herds and areas. They are concerned with diseases in a group or population of animals, and evaluate circumstances connected with the occurrence of brucellosis. These veterinarians help eliminate brucellosis by identifying factors essential to its control and prevention in their region.
How does the brucellosis ring test surveillance work?
The BRT procedure, or brucellosis ring test procedure, makes it possible to perform surveillance on whole dairy herds quickly and economically. Milk or cream from each cow in the herd is pooled, and a sample is taken for testing for brucellosis. Then a suspension of stained, destroyed Brucella organisms is added to a small quantity of milk. If the milk from one or more infected animals is present in the sample, a bluish ring forms at the cream line as the cream rises, which is good sign the animals could have brucellosis. With certain exceptions, herd tests must include all cattle and bison over 6 months of age.
What is the incubation period of brucellosis?
An incubation period is the interval of time between exposure to an infectious dose of organism and the first appearance of disease signs for that animal. The incubation period of brucellosis in cattle, bison, and other animals is quite variable, ranging from about 2 weeks to a full year, and even longer in certain instances. When abortion is the first sign observed, the minimum incubation period is about 30 days in most animals. Some animals abort before developing a positive reaction to the brucellosis diagnostic test. Other infected animals may never abort. There are also infected animals that do not abort but develop a positive reaction to the diagnostic test within 30 to 60 days after infection. Some animals may not develop a positive reaction for several months to over a year after exposed to brucellosis.
Can brucellosis in animals be cured?
Put simply %26ndash; no, brucellosis cannot be cured. Repeated attempts to develop a cure for brucellosis in animals have failed. Occasionally, animals may recover after a period of time but it is more common that only the signs disappear and the animals remain diseased. Such animals are dangerous sources of infection for other animals with which they associate.
Can brucellosis be prevented?
The disease may be avoided by employing good sanitation and management practices for each animal. In fact, for cattle and bison in heavily infected areas or replacement animals added to such herds, officials recommend vaccinating heifers with an approved Brucella vaccine as the best prevention. The vaccine is a live product and must be administered only by an accredited veterinarian. It is important is that tattoo identifies the year in which vaccination took place. Brucella abortus vaccine produces a bodily response that increases the animal%26rsquo;s resistance to this disease. However, vaccination is not 100% effective in preventing brucellosis. The vaccine typically protects about 65% of the vaccinated cattle from becoming infected by an average exposure to Brucella.
How does brucellosis affect humans?
People infected with the brucellosis organism usually develop symptoms similar to a severe influenza. However, this disease (called undulant fever) persists for several weeks or months and may get progressively worse. Farmers, ranchers, veterinarians, and packing plant workers are infected most frequently, because they come into direct contact with infected animals. The initial symptoms of brucellosis are fatigue and headaches, followed by high fever, chills, drenching sweats, joint pains, backache, and loss of weight and appetite. Undulant fever usually does not kill its victims, but the disease is too serious to be dealt with lightly.
What are the main sources of human infection?
In years past, prior to pasteurization, raw milk was considered the prime source of brucellosis in humans, but today most humans contract the disease by coming in direct contact with infected material. Those are aborted fetuses, afterbirth, and uterine discharges of diseased animals, or infected carcasses at slaughter.
Can people get brucellosis by eating meat?
There is no danger from eating cooked meat products, because the disease-causing bacteria are not normally found in muscle tissue. Besides, these bacteria are killed by normal cooking temperatures. The disease could only be transmitted to humans while slaughtering infected animals or processing contaminated organs from freshly killed animals.
How to protect against brucellosis?
Ranchers, farmers, or animal managers should clean and disinfect calving areas and other places likely to become contaminated. Each individual should wear sturdy rubber or plastic gloves when assisting calving or aborting animals. They should also scrub hands well with soap and water afterward. Precautions against drinking raw milk or eating un-pasteurized milk products are also important. Ultimately, the best prevention for brucellosis is to eliminate brucellosis from all animals in the area.
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