Brucellosis

Brucellosis

Brucellosis is a zoonosis (disease that can be transmitted from animals to humans) that occurs all over the world. In a number of countries, including the Netherlands, brucellosis has effectively been eradicated in the farm animal herd, with the result that this population has officially been brucellosis-free in the Netherlands since 1999. Brucellosis is a notifiable disease in the Netherlands in both humans and domestic animals.

The bacterium

Brucellosis is caused by a bacterium of the Brucella genus. Brucella abortus causes brucellosis in ruminants, primarily cattle, and is also called Bang's disease. B. melitensis and B. ovis cause brucellosis in sheep and goats, while B. suis and B. canis cause brucellosis in pigs and dogs respectively. B. microti and B. neotomae may occur in rodents, and B. ceti and B. pinnnipedialis in sea mammals. So-called biovars are further distinguished within the species B. abortus, B. melitensis and B. suis.

Can infect animals and humans

A number of Brucella species are able to infect several animal species, because they are not 100% species-specific. Humans are susceptible to different Brucella species as well, although there are differences in pathogenicity (capacity to cause disease) between the species and even between the biovars within a Brucella species. B. melitensis is the most pathogenic for humans, whereas B. ovis is not.

The disease in animals

The main symptom of brucellosis in animals is abortion or premature birth. The placenta shows typical sources of infection, and if the placenta is not expelled in a timely way, an infection of the uterus occurs that may be fatal to the mother. In the event of abortion, large quantities of bacteria emerge with the offspring, the amniotic fluid and the placenta, resulting in a high risk of infection in humans and animals. Apart from the secretion of bacteria via the placenta, bacteria are also secreted in the milk. Secretion in the milk may be of lengthy duration. Following infection, male animals may become infertile as a result of infection of the testicles. Brucellosis often progresses unnoticed, because there are usually few other symptoms, apart from abortion. As a result, the bacterium may be transmitted throughout a herd without being noticed.

Mandatory notification

Brucellosis in domestic animals and humans is notifiable in the Netherlands. 

Wageningen Bioveterinary Research (WBVR) is the national reference laboratory for Brucella in animals, advises the government on brucellosis and has various serologic testing methods at its disposal.