zoonoses and communicable diseases common to ... - PAHO/WHO

60 BACTERIOSESin various countries in Europe and the Americas. Some human populations may beprotected by mandatory milk pasteurization. In many goat- and sheep-herdingregions, pasteurization of milk is an unattainable goal for the time being. Preventionof the infection in occupational groups (cattlemen, abattoir workers, veterinarians,and others who come into contact with animals or their carcasses) is more difficultand should be based on health education, the use of protective clothing wheneverpossible, and medical supervision.Protecting refrigerator plant and slaughterhouse workers against brucellosis isparticularly important because they constitute the occupational group at highest risk.Protection is achieved by separating the slaughter area from other sections and controllingair circulation. In countries with eradication programs, slaughter of reactiveanimals is limited to one or more designated slaughterhouses (cold storage plants)with official veterinary inspection in each region. These animals are butchered at theend of the workday with special precautions and proper supervision to protect theworkers. Employees should be instructed in personal hygiene and provided with disinfectantsand protective clothing. A 5% solution of chloramine or an 8% to 10%solution of caustic soda should be used to disinfect installations after slaughter(Elberg, 1981). Instruments should be sterilized in an autoclave or boiled for 30minutes in a 2% solution of caustic soda. Clothes may be disinfected with a 2%solution of chloramine or a 3% solution of carbolic acid soap followed by washing.Hands should be soaked for five minutes in a solution of 1% chloramine or 0.5%caustic soda, and then washed with soap and water.The immunization of high-risk occupational groups is practiced in the formerSoviet Union and China. In the former Soviet Union, good results have apparentlybeen obtained with the use of a vaccine prepared from strain 19-BA of B. abortus(derived from strain 19 used for bovine brucellosis), applied by skin scarification.Annual revaccination is carried out for those individuals not reacting to serologic orallergenic tests. To avoid the discomfort caused by the vaccine in man, a vaccine wasrecently developed that consists of chemically defined fractions of the lipid-polysaccharide(LPS) component of the strain 19-BA (Drannovskaia, 1991). In China,an attenuated live vaccine made from B. abortus strain 104M is applied percutaneously.These vaccines are not used in other countries because of possible sideeffects. Promising trials have also been conducted in France with antigenic fractionsof Brucella.Vaccination is recommended for control of bovine brucellosis in enzootic areaswith high prevalence rates. The vaccine of choice is B. abortus strain 19, confirmedby its worldwide use, the protection it gives for the useful lifetime of the animal, andits low cost. To avoid interference with diagnosis, it is recommended that vaccinationbe limited (by legislation) to young animals (calves of 3 to 8 months), as theseanimals rapidly lose the antibodies produced in response to the vaccine. It is estimatedthat 65% to 80% of vaccinated animals remain protected against the infection.The antiabortive effect of the vaccine is pronounced, thus reducing one of theprincipal sources of infection, the fetuses. In a systematic vaccination program, thebest results are obtained with 70% to 90% annual coverage in calves of the properage for vaccination. Male calves and females over 8 months of age should not bevaccinated. Where possible, the upper limit should be 6 months. Revaccination isnot recommended. The main objective of systematic and mandatory vaccination ofcalves in a given area or country is to reduce the infection rate and obtain herds