Carrier status of pathogenic leptospires among swine slaughtered for human consumption in Sri Lanka

Abstract

Leptospirosis is a zoonotic disease caused by pathogenic species of Genes Leptospira that affects humans and a wide range of domestic and wild animals. In livestock industry, infected animals possess a zoonotic threat to the workers. The aim of this study was to identify the carrier status of pathogenic leptosprires among pigs slaughtered for human consumption in Sri Lanka. Parts of kidneys from 105 pigs slaughtered for human consumption were initially collected from 4 provinces of Sri Lanka. Another 13 swine kidney portions including their blood (13) and urine (12) were collected from locations where Leptospirosis-positive results were detected from the initial screening. Extracted DNA were initially subjected to flaB nested-PCR to detect the presence of pathogenic leptospiral DNA. All positive kidney DNA samples were checked again using secY PCR. The flaB and secY PCR positive amplicons were sequenced, and phylogenetic tree was constructed. Serum samples of PCR positive pigs were subjected to Microscopic Agglutination Test (MAT) to determine the infective serogroup. DNA extracted from urine and serum of PCR positive pigs were subjected to Loop-mediated isothermal amplification (LAMP) to detect the presence of pathogenic leptospires DNA. All pigs were clinically normal at the ante-mortem examination Out of 105 kidney samples, 7 were flaB positive. All of the positive samples originated from a single farm. From the follow up collection, 11 out of 13 kidney samples were again flaB positive. All 18 samples were positive for secY PCR too. The phylogenetic analysis confirmed that the organism is Leptospira interrogans. MAT results of the sera showed that the serogroups of infected leptospires were Cannicola, Icterohaemorrhagiae and Autumnalis. LAMP results of sera and urine showed three positives and seven positives respectively. The current study revealed that the pigs slaughtered for human consumption could be chronically infected with pathogenic leptospires. However, infection is not widely spread, and is localised to a single farm from which it can spread via transportation of animals and handling of raw meat. Therefore such contaminated farms can possess a great threat to both humans and other animals.