Brucellosis

Brucellosis is a bacterial disease caused by various Brucella species, which mainly infect cattle, swine, goats, sheep and dogs .

Brucellosis is one of the most widespread zoonoses transmitted by animals and in endemic areas, human brucellosis has serious public health consequences .

The incubation period of brucellosis in cattle, bison, and other animals is quite variable ranging from about 2 weeks to 1 year and even longer in certain instances. When abortion is the first sign observed, the minimum incubation period is usually about 30 days .

Humans generally acquire the disease through direct contact with infected animals, by eating or drinking contaminated animal products or by inhaling airborne agents ¹³.

Most cases are caused by ingesting unpasteurized milk or cheese from infected goats or sheep .

Doctors usually confirm a diagnosis of brucellosis by testing blood or bone marrow for the brucella bacteria or by testing blood for antibodies to the bacteria .

Expansion of animal industries and urbanization, and the lack of hygienic measures in animal husbandry and in food handling, partly account for brucellosis remaining a public health hazard .

1. Probable case: A clinically compatible illness with at least one of the following :
   • Epidemiologically linked to a confirmed human or animal brucellosis case
   • Presumptive laboratory evidence, but without definitive laboratory evidence, of Brucella infection
2. Confirmed case: A clinically compatible illness with definitive laboratory evidence of Brucella infection

Eating undercooked meat or consuming unpasteurized/raw dairy products

The most common way to be infected is by eating or drinking unpasteurized/raw dairy products. When sheep, goats, cows, or camels are infected, their milk becomes contaminated with the bacteria .

If the milk from infected animals is not pasteurized, the infection will be transmitted to people who consume the milk and/or cheese products .

Breathing in the bacteria that cause brucellosis (inhalation)

Breathing in the bacteria that causes brucellosis may also lead to infection. This risk is generally greater for people in laboratories that work with the bacteria. In addition, slaughterhouse and meat-packing employees have also been known to be exposed to the bacteria and ultimately become infected .

Bacteria entering the body through skin wounds or mucous membranes

Bacteria can also enter wounds in the skin/mucous membranes through contact with infected animals.

This poses a problem for workers who have close contact with animals or animal excretions (newborn animals, fetuses, and excretions that may result from birth). Such workers may include :

• slaughterhouse workers
• meat-packing plant employees
• veterinarians

People who hunt animals may also be at risk. When they are in contact with infected animals, exposure to the bacteria may occur through :

• skin wounds
• accidentally ingesting undercooked meat
• inhaling the bacteria while dressing their game. Commonly infected animals include: bison, elk, caribou, moose and wild hogs (feral swine).

Person-to-person spread of brucellosis is extremely rare. Infected mothers who are breast-feeding may transmit the infection to their infants. Sexual transmission has been rarely reported. While uncommon, transmission may also occur via tissue transplantation or blood transfusions

Brucellosis can cause of range of signs and symptoms, some of which may present for prolonged periods of time .

Initial symptoms can include :

• fever
• sweats
• malaise
• anorexia
• headache
• pain in muscles, joint, and/or back
• fatigue

Some signs and symptoms may persist for longer periods of time. Others may never go away or reoccur .

These can include :

• Human abortion
• recurrent fevers
• arthritis
• swelling of the testicle and scrotum area
• swelling of the heart (endocarditis)e
• neurologic symptoms (in up to 5% of all cases)
• chronic fatigue
• depression
• swelling of the liver and/or spleen

Occupational Risks

People in certain occupations or settings may face increased exposure to the bacteria that cause brucellosis .

These can include :

• slaughterhouse workers
• meat-packing employees
• veterinarians
• laboratory workers

Risks from Unpasteurized Dairy Products

Raw milk and milk products are those that have not undergone a process called pasteurization that kills disease-causing germs. These types of products are common outside the United States and are increasingly being sold in mainstream supermarkets in the United States as well .

Consumption of raw milk containing Brucella can cause brucellosis. Most cases of brucellosis associated with raw milk are caused by a strain called Brucella melitensis or Brucella abortus in people who traveled to countries where these strains are common and drank contaminated cow, sheep or goat milk. In rare cases, brucellosis cases associated with other strains, including RB51 and Brucella suis, are reported .

RB51 is resistant to certain antibiotics that would normally be used to prevent or treat Brucella infections. CDC recommends that anyone exposed to RB51 receive antibiotics to prevent an infection .

Risks for Expecting Mothers

Women who are pregnant and have been exposed to brucellosis should consult with their obstetricians/ healthcare provider for evaluation. Laboratory tests and a short course of antibiotics also known as post-exposure prophylaxis (PEP) may be recommended .

Prompt diagnosis and treatment of brucellosis during pregnancy can be lifesaving for the fetus.

While rare, human-to-human transmission from lactating mothers to their breastfed infants has been reported .

Hunters Risks

Many animals can have brucellosis. If you hunt certain kinds of wild animals, you may have an increased risk of brucellosis. This is because as a hunter you may come into contact with the blood and organs of the animals you are hunting .

Animals That Can Put Hunters at Risk

Wild hogs (feral swine)

• elk
• bison
• caribou
• moose
• deer.

In addition, predators such as bears and wolves may get brucellosis after they feed on infected animals. If you hunt or trap these types of predatory animals, be aware of the risk for brucellosis and protect yourself. Dogs that are used for hunting can also be at risk for brucellosis .

You can get sick if blood, fluid, or tissue from an infected animal comes in contact with your eyes, nose, mouth, or skin. This can happen when you are involved in hunting-related activities such as :

• Eating meat that is not thoroughly cooked
• Field dressing
• Butchering
• Handling or preparing raw meat for cooking

Before treatment begins, a diagnosis of brucellosis infection must be made by a doctor .

Tests will be performed to look for bacteria in samples of blood, bone marrow, or other body fluids. In addition, a blood test can be performed to detect antibodies against the bacteria .

Once a diagnosis is made, a doctor can prescribe antibiotics .

Depending on the timing of treatment and severity of illness, recovery may take a few weeks to several months. Death from brucellosis is rare, occurring in no more than 2% of all cases.

The best way to prevent brucellosis infection is to be sure you do not consume :

• undercooked meat
• unpasteurized dairy products, including:
  • milk
  • cheese
  • ice cream

Pasteurization is when raw milk is heated to a high temperature for a short period of time . This heating process destroys harmful bacteria that may make the milk unsafe to consume.

If you are not sure that the dairy product is pasteurized, do not eat it .

People who handle animal tissues (such as hunters and animal herdsman) should protect themselves by using :

• gowns or aprons.
• rubber gloves
• goggles