Abstract :
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.
