Factors associated with the seroprevalence of caseous lymphadenitis in sheep from Northeastern Brazil.

Caseous lymphadenitis (CL) is one of the main infectious diseases in sheep, responsible for great economic losses, mainly in Northeast region of Brazil, which has the largest sheep flock in the country. Thus, the aim of this survey was to determine the factors associated with the seroprevalence of this disease in sheep from Northeastern Brazil using a planned sample of flocks and animals. Samples were collected from 2312 adult and young sheep of both sex from 196 farms, located in 51 municipalities in five Northeastern Brazilian states (Ceará, Paraíba, Piauí, Rio Grande do Norte, and Sergipe). Serological diagnosis was performed using the indirect ELISA technique. Factors associated with seropositivity were identified by variables extracted from epidemiological questionnaires administered to breeders, using univariable and multivariable analyses. Factors associated with prevalence were purebred sheep (Prevalence ratio - PR = 1.189; P = 0.017), ram acquisition from animal expositions (PR = 1.192; P = 0.020), offspring is separated from ewes (PR = 1.132; P = 0.048), water supplied to sheep from ponds (PR = 1.365; P = 0.002), and delayed disposal of infected animals (PR = 1.263; P = 0.027). Flock-level and animal-level prevalences were 93.88 % (95 % CI = 89.60-96.46%) and 37.46 % (95 % CI = 35.51-39.45%), respectively. In view of the high prevalence found here and based on the associated factors, the implementation of an efficient CL control programme in Northeastern Brazil is recommended.

Seroepidemiological study of Caseous lymphadenitis in sheep from the Northeast region of Brazil using an indirect ELISA.

The objective of this study was to determine the frequency of seropositivity Corynebacterium pseudotuberculosis in sheep in five states of northeastern Brazil, using an indirect enzyme-linked immunosorbent assay (i-ELISA). Young and adult sheep of both sexes were used. Blood samples were collected from 2638 sheep from 223 herds across all states. For the i-ELISA, antigens produced from the strain of C. pseudotuberculosis BRM 029971, a bacterial isolate from the Northeast region of Brazil, were used. Sensitivity and specificity indexes were calculated for the validation of the test, using as reference 49 and 134 serum samples from sheep known to be positive and negative, respectively. The i-ELISA presented four false-negative and four false-positive results, showing a specificity of 97.01%, a sensitivity of 91.84%, and an accuracy of 95.63%. These results were calculated based on an optical density (OD) cutoff point = 0.138. Of the 2638 sheep tested, 996 (37.76%, 95% CI = 35.93-39.62%) were seropositive, and of the 223 evaluated herds, 210 (94.17%, 95% CI = 90.28-96.56%) seropositive. The i-ELISA showed adequate sensitivity and specificity, proving to be a useful tool in the diagnosis of caseous lymphadenitis (CLA) in sheep. Infection by C. pseudotuberculosis, determined by serology, is disseminated in the sheep herds in the states of Northeast Brazil. Thus, there is a need to implement effective control measures that prevent the spread of infectious agents.