Brucellosis: What you need to know
Brucellosis is a debilitating zoonotic disease. Since it affects both humans and animals, it is a disease of immense public heath significance and happens to be prevalent in many countries, including Kenya. It is among the most important zoonotic diseases.
Which animals are affected?
Grazing animals (herbivores) are more likely to contract the disease since the bacterial spores responsible for transmission are found in the soil, where they can stay for decades. Brucellosis affects cattle, pigs, sheep, goats, dogs and wildlife. The Brucella bacteria cause it. Different animals are infected by specific species of the bacteria.
Humans almost invariably contract the natural disease directly or indirectly from animals or animal products from infected animals. Some social-cultural practices such as consumption of raw milk fuels infections.
How is it transmitted?
According to the World Organisation for Animal Health (OIE), brucellosis is spread when an animal aborts or gives birth. The bacteria localise in the reproductive organ of the infected animal. High levels of bacteria are found in the birth fluids of the animal. During birth, this fluid contaminates the environment.
The bacteria shed can survive outside the animal in the environment for several months, particularly in cool moist conditions. They remain infectious to other animals, which become infected by ingesting them. The bacteria also colonise the udder and contaminate milk. Animals ingest bacterial spores from the soil as they graze. Infected bulls can shed the bacteria in their semen and can infect females. Cuts in the skin, or through mucous membranes can also serve as ports of entry for the bacteria. Humans can get infected through contact with infected animals and animal products. Inhalation of spores from infected products also causes infection in humans;
What are the clinical signs?
Affected animals may appear healthly. However, in some cases, mild signs such as swollen testes in males, arthritis and hyperaemic membranes are seen. Abortion is the main sign in females. Stillbirths, infertility, retention of placenta or birth of weak offspring are other indications of brucellosis. Generally, the disease in animals, reduces their reproductive efficiency and causes great losses, especially in cattle and sheep rearing.
What should I do in suspected cases?
Handle aborting animals and the abortus with caution and use personal protective equipment (PPE). Inform your animal health professional of any cases of abortion on your farm. Brucellosis is a notifiable disease and suspected cases must be reported to the authorities.
How do I treat or prevent it?
Preventative measures are emphasised because there is no practicable treatment for animals. Diagnosis is based on clinical signs. Samples are then sent to the laboratory for confirmation. Animals confirmed to have the diseases are culled. The long-term goal is to have and maintain a brucellosis- free herd. Vaccination is encouraged where applicable. Human brucellosis is best prevented by controlling the infection in animals, which emphasises one health approach encompassing humans, animals and the environment in the management of the disease.
Dr Nderitu Nyaga S, BVM, MSc,
Department of Veterinary Anatomy and Physiology.