The present investigation delineates the role of listeric infection in aborted ewes or those with history of abortion from organized farms of Kashmir region. A total of 141 clinical samples was analyzed for the isolation and identification of Listeria species. On analysis four isolates were identified as Listeria monocytogenes, while 24 were non-pathogenic Listeria species. Of the four L. monocytogenes isolates, two were isolated from brain tissue of aborted fetus (BrS10 and BrG36) while one each was isolated from vaginal swab (Vd13) and rectal swab (RS11) of the ewe. An overall isolation rate of 2.83 % was observed for L. monocytogenes and 17.02 % for non-pathogenic Listeria species. Further to reveal the pathogenic potential, the recovered L. monocytogenes isolates were subjected to the battery of in vitro pathogenicity test such as hemolytic activity on Sheep Blood Agar, Phosphatidyl Inositol-Phospholipase C activity on Agar Listeria according to Ottaviani and Agosti medium, multiplex PCR targeting virulence markers genes viz., prfA, plcA, actA, hly, inlC and in vivo chick embryo inoculation test. All the L. monocytogenes isolates recovered in the present study were potentially pathogenic and on comparison, a good correlation was observed among in vitro and in vivo pathogenicity test including multiplex PCR targeting virulence associated genes.

Listeriolysin O (LLO) is a dominant antigen target of anti-listerial immunity. The present study described the development of an indirect ELISA employing immunodominant non-cross-reactive synthetic peptides of LLO (LLO-1 and LLO-2) and its comparison with that of purified LLO based indirect ELISA using serum samples collected from 59 ewes which either had abortion or had a history of abortion. Initially isolation of Listeria was attempted from the samples collected from the ewes. A high seropositivity (54.2%) was observed against purified LLO; however, after adsorption of positive sera with streptolysin O (SLO), the seropositivity was 23.7%. Overall seropositivity with LLO-1 and LLO-2 peptides revealed comparatively less cross-reactivity in comparison to that of purified LLO. Three of the four animals culturally positive for Listeria monocytogenes were also positive serologically for ALLO by both the ELISAs even after adsorption of test sera with SLO. Antibodies against purified LLO and synthetic LLO-1 peptide based ELISAs detected antibodies even in samples from which non-pathogenic Listeria spp. were isolated; however, LLO-2 peptide did not reveal any ALLO antibodies from those samples which were culturally positive for non-pathogenic Listeria. In conclusion, LLO-2 peptide can serve as an ideal virulent marker for serodiagnosis of ovine listeriosis. Further evaluation of LLO-2 peptide based indirect ELISA with more number of samples is needed.