Brucella Abortus: Primarily a disease of cattle; the most common clinical sign of Brucellosis is high incidence of abortion or premature calving of recently infected animals. The foetus, placenta and uterine fluid contain large quantities of Brucella abortus bacteria which can infect other cattle coming into contact with an infected animal around the time of calving. The organism continues to be excreted in the milk; in the past humans were frequently infected through drinking unpasteurised milk. Breeding bulls which are infected, can transmit the disease to cows at the time of service by infected semen.
Brucella Melitensis: The bacteria can affect most species of domestic animals but mainly causes Ovine Brucellosis (of sheep and goats). Reproductive failure with abortion is the most common clinical sign of Brucella melitensis. Infection is normally by inhalation and via abraded skin and transmission between species occurs easily. Humans usually become infected by drinking affected milk or eating milk products made with affected unpasteurised milk. The post-partum discharges (after-birth) of infected females contain large numbers of bacteria whether or not the animal has aborted. After abortion, infection may persist in the uterus for many months, and in the udder for years. The United Kingdom is recognised by the European Commission as being free from Brucella Melitensis.
The level of infection in milk and uterine discharges is probably lower in sheep than in goats. As with Brucella Abortus, viable offspring from infected females may also be infected but seronegative and may discharge infection following birth or abortion. These animals would thus be a significant risk when imported into an uninfected flock or herd and it is essential that animals be added only from flocks/herds of known free status.
Brucellosis in humans: Brucellosis is a highly contagious zoonosis caused mainly by eating and drinking unpasteurised milk or milk products or by coming into contact with the discharges of infected animals. In humans it is also referred to as Malta fever, Mediterranean fever or undulant fever. It affects people of all ages and both sexes. Symptoms often include intermittent flu-like illness and/or persistent headaches. If left untreated the disease may persist for weeks or months and can affect any organ in the body.