Abattoir survey on caseous lymphadenitis in sheep and goats in Tanta, Egypt

This study was carried out to determine some epidemiological and histopathological aspects associated with caseous lymphadenitis (CLA) on 962 slaughtered animals (692 sheep and 270 goats) at Tanta abattoir, Egypt. The prevalence of CLA among slaughtered animals was 26.92% and 25.05% on the basis of gross and bacteriological examination, respectively. On the basis of gross examination, the prevalence was 33.23% and 10.74% among slaughtered sheep and goats, respectively. Whereas on the basis of bacteriological examination, the prevalence was 32.65% and 5.55% in sheep and goats, respectively. The prevalence of CLA was significantly higher in slaughtered females than slaughtered males (p < 0.0001; OR: 22.93; CI 95%: 15.71–33.46). Statistically, the prevalence of CLA differed among different age groups; the higher prevalence was recorded in animals of the age group over 2 years (51.35%) than those from 1 to 2 years (8.84%) (p < 0.0001; OR: 10.98; CI 95%: 7.611–15.58) and under 1 year (7.5%) (p < 0.0001; OR: 13.2; CI 95%: 3.944–43.00). Superficial lymph nodes of the anterior half of the body showed higher infection rate than posterior half lymph nodes. Cross section of the affected lymph nodes revealed thick caseated greenish pus surrounded by thick fibrous tissue. Histopathological examination of the affected lymph nodes showed pyogranulomas surrounded by massive infiltration of macrophages and fragmented neutrophils. The experimental injection of CLA pyogenic materials was resulted in death of guinea pigs within 7–9 days with typical gross and histological lesions of CLA. Moreover, Corynebacterium pseudotuberculosis could be isolated from the died guinea pigs. In conclusion, CLA is more prevalent in slaughtered sheep than slaughtered goats and in females than males. Also, it was observed the increase of CLA prevalence with the progress of animal age. Therefore, beside early detection and culling of infected animals, strict hygienic care during shearing process is highly recommended.