Investigation of Brucellosis among Livestock and Humans, Songkhla Province, Thailand, 2011

Abstract

Background: Brucellosis impacts both human health and farm economics. Veterinary laboratory surveillance 2009 to 2011 detected six outbreaks of bovine brucellosis in Songkhla province. Veterinary and public health authorities investigated to determine scope of the outbreak and conducted active case finding for recommending preventive measures.
Methods: A descriptive study was conducted at farm X and a nearby public grazing range. By simple random sampling, serum was collected from 271 cattle, 780 goats, 79 sheep and 39 farm workers at farm X and 64 nearby cattle. Cases were defined by positive Rose Bengal Test among livestock and by both IgG and IgM brucellosis titers > 1:30 and > 1:20 by ELISA among humans. We interviewed farm workers about occupational risk and farm management.
Results: Herd prevalence of brucellosis among cattle was 12% at farm X and 25% at nearby farms. Sheep (1.3%) and goats (0%) prevalence was low. Cattle was older than 3 years old had a higher risk to be detected seropositive than in younger cattle (PR 2.96, 95%CI 0.94-9.38). The possible risk factors were hypothesized including a transmission of brucellosis between nearby herds through sharing some pastures during rotational grazing, an inappropriate management in paturient animals and using natural mating. No human cases were found. 76% of farm workers had a good practice by using personnel protective equipment.
Conclusions: Cattle in farm X and nearby farms had high prevalence of brucellosis, but we found little evidence of interspecies transmission. We recommended monthly screening, culling affected animals, appropriate parturition management and fence repair. Post–intervention, bovine brucellosis has decreased at farm X to 1%.