Risk Assessment and Molecular Epidemiology of Salmonella in Pig Slaughterhouses in Upper-northern Part of Thailand

Abstract

Salmonella spp. is an important pathogens which can cause gastroenteritis in human. Pig and pork products are considered as the main source of salmonellosis. The idea that “Salmonella spp. positive carcasses result from Salmonella infected pigs” has been mentioned in several studies. In general, the objectives of this study were to determine the prevalence, contamination levels and characteristic of Salmonella spp. recovered in slaughtering levels as well as to define an association of those Salmonella strains with the strains recovered from farm level to identify appropriate preventive and control measures of salmonellosis in the region.

In total of 1,875 samples acquiring from 3 major slaughterhouses in Chiang Mai and Lamphun provinces, including pig carcasses, feces, mesenteric lympnodes, slaughtering-equipments as well as the environment were obtained. Salmonella positive samples were detected in 353 samples or 18.83%. The highest prevalence was found in mesenteric lymphnode samples (61.33%; 1.45 log MPN/g), followed by fecal samples (56.00%; 1.46 log MPN/g). Considering in pig carcasses samples, which recognized as the samples influenced the contamination in pig production chain, directly. The prevalence and contamination levels mean was detected at 11.85% and 0.13 log MPN/cm2, respectively.

In this study, there was no statistically significant in Salmonella spp. contamination detected with different patterns at the slaughterhouses (between the slaughterhouses received finishing pigs from co-operative farms vs integrated farms). Factors found to reduce Salmonella spp. loads on carcasses such as regular changing of water in the scalding tank after each batch and the use of chlorine in the washing step were identified.

In view of the comparison of DNA fingerprint pattern about Salmonella strains recovered from slaughtering level versus farm level, the results provied an association on strains recovered from environment, pig and workers (both of farms and slaughterhouses). An evidence of the persistent strains in some areas as well as the farm-slaughterhouse contamination route were also detected.

Most of the strains contaminated in pig production chain including farms and slaughterhouses were recognized as the multidrug resistance strains. It has become the major public health concern, which can reduce the cure efficacy and limitation in choice of treatment, both in human cases and farm animals.

In addition, Salmonella’s control and preventive programs should include timely monitoring in the populations of farm animals as well as the recommendations to insure appropriate practices in slathering processes for the stakeholders to enhancing the good hygienic in food consumption in the region.