Brucellosis

Cattle Diseases

Brucellosis in Cattle

Brucellosis is one of the most common zoonotic diseases worldwide, potentially causing chronic illness in people, particularly in developing countries. The link between brucellosis in wildlife and livestock is also a concern. Brucellosis can affect all farm livestock but in cattle the disease is caused by the facultative intracellular bacterium Brucella abortus, and as the name suggests this causes late stage abortions in cattle, placentitis, which produces weak new-born calves and infertility in cows and bulls (Neta et al., 2010). After the first episode of Brucella-induced abortion, the cow often has normal subsequent births, although other abortions may occur (Nicoletti, 1984).

Aborted fetuses, fetal membranes and uterine secretions are the most important sources of infection (Samartino and Enright, 1993). The disease can also be transmitted in utero, and via infected milk. Calves that acquire infection in-utero, or via infected milk, may show signs of disease or remain asymptomatic. However heifers with  latent asymptomatic infection may abort, or give birth to infected calves, which are central in maintaining a disease within a herd (Nicoletti, 1984).

Infected bulls may develop signs of infection fever, anorexia, and depression although disease is often not obvious. However affected bulls can develop permanent infertility (Campero et al., 1990).

Brucellosis control efforts for cattle in the United States began in 1934 and formally became an eradication program in 1954 (Godfroid et al., 2014). Currently, regulatory efforts rely on serological surveillance and removal of seropositive animals, and vaccination of prepubescent females deemed to be at risk of infection. In other countries, such as the UK, Brucellosis is a notifiable disease and it has been officially free of brucellosis since 1991, although sporadic cases have been reported, most recently in Cornwall in 2004 and in Scotland in 2003 (Blissit et al., 2005).

The link between brucellosis in wildlife and livestock is a concern in some countries and regions.  In the United States, responsibility for wildlife diseases is complex and can encompass both state and federal agencies. However, in general, transport of wildlife across state boundaries requires compliance with regulations for disease control programs for domestic livestock. There is a long-standing conflict between wildlife conservationists and animal health authorities and livestock farmers concerning the different strategies implemented to control diseases shared by livestock and wildlife. In the US, a primary concern regarding persistence of B.abortus in a wildlife reservoir are the bison herds in Yellowstone Conservation Area and Grand Teton National Park and the very large elk population in the states of Wyoming, Montana and Idaho (Godfroid et al., 2014).

The disease often presents as an outbreak of abortion, so notification of unexpected abortions forms an important part of surveillance. In many situations, disease outbreaks associated with imported cattle, for example from the Republic of Ireland (Blissit et al., 2005) and Northern Ireland to mainland Britain, have been considered to constitute a significant risk to disease introduction (Jones et al., 2004). Brucellosis is also found in other European countries, particularly in southern European countries where the disease is found in small ruminants and has a variable wildlife reservoir (Godfroid and Käsbohrer, 2002). Therefore testing of animals after importation is an important control measure.

Brucellosis is reportable to the USDA as Bovine Brucellosis (Brucella abortus), or as Brucellosis in cattle caused by Brucella melitensis or Brucella suis. Visit the US Department of Agriculture Brucellosis Disease Information pages for more information, and in particular the Facts About Brucellosis document.

For more information regarding brucellosis in humans please visit the Center for Disease Control’s (CDC) website.

Control and Prevention of Brucellosis

In the UK, current brucellosis surveillance includes:

• Routine bulk tank milk testing for Brucella antibodies.
• The reporting of bovine abortions to a veterinary surgeon or the local AHVLA office
• Monitoring of selected bovine abortions, including collection of blood, milk and aborted material samples
• Surveillance testing of imported cattle.

Treating Brucellosis

There is no specific treatment in confirmed infected animals.

Brucellosis and Welfare

Any animal aborting should be isolated to prevent disease spread until diagnostic sampling results have been confirmed. During this time symptomatic treatment should be administered.

Good Practice Based on Current Knowledge

The reporting of ALL bovine abortions to a veterinary surgeon and to the relevant authorities.