L’avortement enzootique des brebis

Abstract

"Infectious causes of abortion have been associated with severe economic losses for the livestock and have zoonotic implications. A cross-sectional study is carried out to estimate prevalence of Chlamydia spp. antibodies and to investigate risk factors associated with chlamydial infection in 552 ewes between March 2011 and January 2012. A serological screening is conducted to determine prevalence of antibodies against five infectious agents in 226 ewes. ELISA, rapid slide agglutination and slow agglutination techniques are used to detect antibodies against Chlamydia spp., Coxiella burnetii, Brucella melitensis, Salmonella abortus ovis and Neospora caninum. Antibodies toward Chlamydia spp. and Coxiella burnetii were the most prevalent. Anti-Chlamydia spp. and anti-C. abortus antibodies were present in respectively 24,5 % and 7,2 % of examined sera. Of the herds, 70,4 % had at least one seropositive animal for Chlamydia spp. and 33,3 % for C. abortus. A pretested structured questionnaire was administered in order to collect information on individual animal health and herd management practices. Chi-square analysis and multivariable logistic regression model were used to identify risk factors related to Chlamydia spp. and C. abortus seropositivity. Multivariable logistic regression model identified 12-23 months age group and not using disinfectants as risk factors for Chlamydia spp. seropositivity. Occurrence of stillbirth and 5–10 % mortality rate in young lambs were significantly associated with Chlamydia spp. seropositivity. However, availability of veterinary service was identified as a protective factor. The model revealed that foreign farm visitors are a risk factor for enzootic abortion of ewes. Results of this study determined two major variables associated with seropositivity to C. abortus; delivery of weak lambs and septicemia in young lambs. Molecular characterization by PCR-RFLP of 104 fetal and placental ovine samples confirmed infection with C. abortus in 4 placentas and 26 fetal tissues. The partial nucleotide sequence similarity matrix of omp2 gene showed that the Algerian isolates have 96% similarity with C. abortus FAS strain and 84.3 % similarity with C. caviae strain while a low similarity the other species of the genus Chlamydophila was found. Histological examination of PCR positive placentas revealed a severe placentitis."