Relieving the burden of brucellosis?
First identified in the second half of the 19th century, as a result of research
into why sailors on board ship in the Mediterranean were falling sick,
brucellosis has been with us for perhaps thousands of years. One of its
characteristics, in both people and animals, is that its many symptoms
make clinical diagnosis difficult. It was the Maltese physician, Zammit,
who first discovered the zoonotic relationship of brucellosis in goats
with humans and, once goats milk was banned from the military garrison
in 1906, the problem was effectively over - at least for the military.
But the disease remains and is considered by FAO, WHO and OIE as the most
widespread zoonosis in the world.
In many developed countries, brucellosis has been brought under control but, in developing countries, it takes a heavy toll. The most seriously affected areas are around the Mediterranean basin, the Middle East, western Asia, parts of Africa and Latin America. In livestock - cattle, sheep, goats, pigs, camels, buffaloes and wild ruminants are susceptible - the disease causes stillbirths, abortions, drop in milk yield and sterility. It affects trade and hinders livestock development. In people, symptoms may include fever, drenching night sweats, aching joints, headache, fatigue and mental depression, lasting perhaps for several months, and this obviously has a serious impact on productivity as well as human suffering.
There are six known species of the Brucella bacteria of which Brucella melitensis is the most significant. Transmitted through contaminated and untreated milk and milk products, and by direct contact with infected animals, its reach is both widespread and increasing. Farm workers, vets, laboratory and slaughterhouse workers are at most risk through handling infected animals, especially when assisting in lambing, kidding or calving but, where milk is not routinely pasteurized, all consumers of untreated dairy products are at risk. Of particular concern is its emergence in intensive dairy farms. Studies in Tanzania by CTVM are trying to establish whether people are being infected by their own cattle, or through pooled milk. By tracing back to identify the risk factors, it should be possible to identify those groups who are most vulnerable, and target control efforts more effectively.
Prevention and control
Vaccination programmes that target cattle against B abortus have proved effective but trying to control B.melitensis in sheep and goats is much more difficult, not least because of the difficulty in identifying, vaccinating and monitoring infected flocks and in controlling their movements. All milk and other dairy products should be heat-treated to kill the bacteria but it has to be accepted that there will be many for whom this is impractical or culturally unacceptable. Antibiotics are used for treating people who contract the disease but there are concerns that because those drugs most commonly used are also used to treat tuberculosis, the already grave problem of drug resistance may be accelerated.
In common with other zoonoses, information on the number of people affected by brucellosis and its economic impact is poor, especially in developing countries. BruNet a joint FAO and WHO initiative, has been set up to support exchange of information, research and understanding of the geographical spread, economic impact and ongoing brucellosis control efforts worldwide. It provides a forum for experts to discuss such issues as taxonomy, vaccine development, surveillance methods and diagnosis. The disease may not cause a spectacular number of human deaths but it is a serious and under reported public health matter that causes heavy economic losses in livestock production. It can be controlled, as the Malta based garrison at the beginning of the 20th century discovered. Now, at the beginning of the 21st century, is it not time to increase and widen efforts to control the disease?
