Abstract
BackgroundLack of clear risk factor identification is the main reason for the persistence of brucellosis infection in the Chinese population, and there has been little assessment of the factors contributing to Brucella contamination of raw whole milk. The purpose of this study was to identify risk factors affecting Brucella contamination of raw milk, and to evaluate effective measures for disease reduction in order to determine preventive strategies.Methods and FindingsA nationwide survey was conducted and samples were obtained from 5211 cows corresponding to 25 sampling locations throughout 15 provinces in China. The prevalence of Brucella in the raw milk samples averaged 1.07% over the 15 Chinese provinces, while the prevalence of positive areas within these regions ranged from 0.23–3.84% among the nine provinces with positive samples. The survey examined factors that supposedly influence Brucella contamination of raw whole milk, such as management style, herd size, abortion rate, hygiene and disease control practices. A binary logistic regression analysis was carried out to determine the association between risk factors for Brucella and contamination of milk samples. Furthermore, a relative effect decomposition study was conducted to determine effective strategies for reducing the risk of Brucella contamination of raw whole milk. Our data indicate that disease prevention and control measures, abortion rate, and animal polyculture are the most important risk factors. Meanwhile, culling after quarantine was identified as an effective protective measure in the current Chinese dairy situation.ConclusionsThese results indicate that, although there is a low risk of contamination of milk with Brucella nationwide in China, there are individual regions where contamination is a significant problem. Controlling three factors–culling after quarantine, maintaining a low abortion rate, and avoiding mixing groups of cattle and small ruminants–could effectively reduce the risk of Brucella contamination of raw whole milk.
Highlights
Brucellosis is a zoonotic bacterial infection that is a serious public health problem in many countries of the world [1]
No Polymerase Chain Reaction (PCR)-positive samples were obtained from six of the tested provinces, of the remaining nine tested provinces the percentage of positive cattle ranged from 0.23%–3.84%
Retrospective analyses of the factors that supposedly affect exposure to Brucella found eight factors that significantly differed among interclass levels; these were feeding pattern, herd size, abortion rate, animal polyculture, introduction of new animals, disease prevention and control measures, hygiene, and infection history (Table 2)
Summary
Brucellosis is a zoonotic bacterial infection that is a serious public health problem in many countries of the world [1]. Several Brucella vaccines have been used in China for prevention and control of brucellosis in the past decades [11]; some drawbacks of the vaccine, including low quality and interference of vaccine-related antibodies with diagnostic testing, have long plagued researchers and policymakers. These problems have been well resolved with the Strain RB51 vaccine, which has the advantage of producing protection apparently comparable to Strain 19 without inducing the titers that cause diagnostic confusion, administration of the currently available vaccine alone is not sufficient for the eradication of brucellosis in any country [24]. The purpose of this study was to identify risk factors affecting Brucella contamination of raw milk, and to evaluate effective measures for disease reduction in order to determine preventive strategies
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