Advances in Animal and Veterinary Sciences

Research Article
Adv. Anim. Vet. Sci. 3 (6): 325 - 331
http://dx.doi.org/10.14737/journal.aavs/2015/3.6.325.331
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Shivaramu Keelara1*, Satya Veer Singh Malik2, Shivasharanappa Nayakvadi3, Samir Das2, Sukhadeo Baliram Barbuddhe4

1Department of Nutrition and Food Science, University of Maryland, College Park, MD 20742, USA; 2Division of Veterinary Public Health, Indian Veterinary Research Institute, Izatnagar, 243122, India; 3Animal Sciences Section, Central Coastal Agricultural Research Institute, Goa, 403402, India; 4National Institute of Biotic Stresses Management, Raipur, Chhattisgarh, India.

*Correspondence | Shivaramu Keelara, University of Maryland, College Park, USA; Email: shivakeelara@gmail.com

Abstract
In the present investigation, a total of 880 clinical samples comprising blood (n=215), vaginal swabs (n=220), fecal swabs (n=220), placenta (n=10) and sera (n=215) from ewes with abortion or history of abortion as well as from apparently healthy ewes of organized and migratory flocks were collected for screening listeric infection by isolation, serological and molecular diagnostic methods. 23 different isolates were recovered which comprised of 15 L. monocytogenes, 2 L. ivanovii and 6 other listeriae. Among these, four haemolytic isolates (L. ivanovii-2 and L. monocytogenes-2) were found pathogenic based on hemolysis on sheep blood agar, CAMP test, PI-PLC activity, virulence-associated genes (prfA, plcA, actA, hlyA and iap) as well as by in vivo pathogenicity tests namely, chick embryo and mice inoculation tests. Indirect plate ELISA revealed 41.96% seropositivity for antibodies against listeriolysin O in ewes with abortion or history of abortion and 26.21% in apparently healthy ewes, which after adsorption of sera with Streptolysin O (SLO) reduced to 18.75% and 9.70% in respective groups. On over all basis, out of 215 sheep sera, 74 (34.42%) sera showed positivity for ALLO, which was reduced to 31(14.42%) following adsorption with SLO, indicating the need for sera adsorption for removing the cross-reactivity. The study had significant implications in understanding the epidemiology of listeric infection in migratory flocks.

Keywords | Listeria spp, Migratory sheep, Abortion, LLO, ELISA