Abstract :
Corynebacterium pseudotuberculosis is the etiologic agent of caseous lymphadenitis, which
is a serious, economically important problem for sheep production. We examined the seroprevalence
of infection by C. pseudotuberculosis and possible risk factors associated with
caseous lymphadenitis in sheep herds of the state of Minas Gerais, Brazil. Samples were
collected from 642 sheep from 97 farms. Sera of all of the sheep were tested with ELISA
for antibodies against C. pseudotuberculosis. A questionnaire was applied to gather data on
the farm, the sheep herd, the farmer, and individual animal data (breed, sex and age). This
is the first sero-epidemiological survey for caseous lymphadenitis in sheep herds in Minas
Gerais.Wefound a high real prevalence, much higher than that suggested from information
obtained with the questionnaire, which points to the scarcity of vaccination against caseous
lymphadenitis in the sample evaluated. Only a small proportion of the farmers declared that
cases of this disease were present in their flocks. The frequency of seropositive sheep varied
significantly with breed ( 2 test, P = 0.021). Age group also significantly affected the
percentage of seropositivity ( 2 test, P = 0.049), the highest frequency being found in adult
animals (more than 12 months old), when compared to the 5–12 months old group ( 2
test, P = 0.021). The prevalence of infection with C. pseudotuberculosis in sheep in the state
of Minas Gerais was estimated to be 70.9% (95% confidence interval (CI): 64.7–77.0%) and
the prevalence of infected flocks being 95.9% (95% CI: 89.8–98.9%). We concluded that C.
pseudotuberculosis infection is widely disseminated in sheep flocks in Minas Gerais and that
caseous lymphadenitis control and eradication programs are necessary in this state.
