Large-scale study of herd-level risk factors for bovine brucellosis in Brazil.
Bovine brucellosis is an important zoonosis caused by Brucella abortus that negatively impacts livestock productivity. In 2001, Brazil launched a new national program aimed at eradicating animal brucellosis that included large-scale studies of the prevalence and risk factors to support strategic decision-making. These studies were implemented by the animal health authorities and were underpinned by the scientific coordination of the University of São Paulo and the University of Brasília. The state-level results were published and revealed important differences in herd prevalence among regions. The risk factors varied across states and did not clearly explain the observed spatial disease spread. This study used a consolidated herd-level database of 14 states and 17,100 herds, from the prevalence surveys' data, to gain insights into herd profiles and cattle production practices that might be associated with the risk of brucellosis. At the time of data collection, the study area comprised just over 56 million bovine females aged over 24 months and approximately 1.8 million herds. After an exploratory univariable analysis, all factors with p≤0.20 were included in a multiple logistic regression model, using the design-based method in order to take herd sampling weights into account. The number of females in the herd markedly increased the risk of infection; compared with smaller herds (less than 30 females), the odds ratio was 3.42 [CI 95% 2.98-3.91] for herds with 31 to 100 females, 5.68 [4.92-6.55] for herds with 101 to 400 females, and 13.14 [10.94-15.78] for herds with more than 400 females. The risk was higher for extensive cattle production farms (OR=1.23 [1.07-1.42]) and for farms that purchased replacement stock from cattle traders (OR=1.27 [1.08-1.47]) or directly from other farms (OR=1.19 [1.07-1.32]). The exclusive use of artificial insemination (OR=0.57 [0.4-0.81]) and regular veterinary support (OR=0.68 [0.6-0.77]) appeared to be protective factors. These findings are consistent with the regional prevalence trends observed in the study and provide key guidance for the planning of the national effort to control and eradicate brucellosis. High vaccination coverage of heifers is recommended, especially when targeted to areas where large-scale extensive cattle production predominates. The smaller, more intensive herds, are good candidates for disease accreditation schemes.
Universidade de Brasília, Laboratório de Epidemiologia Veterinária, Faculdade de Agronomia e Medicina Veterinária, Campus Darcy Ribeiro, ICC Sul - CP 4508, Brasília, DF, 70910-970, Brazil.
Ana Lourdes Arrais
ALA
de Alencar Mota
Universidade de São Paulo, Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Av. Prof. Dr. Orlando Marques de Paiva, 87, São Paulo, SP, 05508-270, Brazil.
Fernando
F
Ferreira
Universidade de São Paulo, Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Av. Prof. Dr. Orlando Marques de Paiva, 87, São Paulo, SP, 05508-270, Brazil.
José Soares
JS
Ferreira Neto
Universidade de São Paulo, Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Av. Prof. Dr. Orlando Marques de Paiva, 87, São Paulo, SP, 05508-270, Brazil.
Ricardo Augusto
RA
Dias
Universidade de São Paulo, Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Av. Prof. Dr. Orlando Marques de Paiva, 87, São Paulo, SP, 05508-270, Brazil.
Marcos
M
Amaku
Universidade de São Paulo, Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Av. Prof. Dr. Orlando Marques de Paiva, 87, São Paulo, SP, 05508-270, Brazil.
José Henrique
JH
Hildebrand Grisi-Filho
Universidade de São Paulo, Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Av. Prof. Dr. Orlando Marques de Paiva, 87, São Paulo, SP, 05508-270, Brazil.
Evelise Oliveira
EO
Telles
Universidade de Brasília, Laboratório de Epidemiologia Veterinária, Faculdade de Agronomia e Medicina Veterinária, Campus Darcy Ribeiro, ICC Sul - CP 4508, Brasília, DF, 70910-970, Brazil. Electronic address: vitorspg@unb.br.
Vítor Salvador
VS
Picão Gonçalves
D000822:Animal Husbandry / Q000592:standards; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001938:Brazil / Q000453:epidemiology; D002003:Brucella abortus / Q000302:isolation & purification; D002007:Brucellosis, Bovine / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control* / Q000635:transmission; D002417:Cattle; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D016017:Odds Ratio; D011156:Population Density; D015995:Prevalence; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D014730:Veterinary Medicine / Q000706:statistics & numerical data*
D000907:Antibodies, Bacterial
Brazil; Brucella abortus; Cattle; Risk factors