Prevalence and risk factors of Linguatula spp. in slaughter animals in Tabriz, Iran, and methods for nymphal stage inactivation

Abstract

Linguatula is a food born zoonotic parasite in which carnivores and herbivores serve as final and intermediate hosts, respectively. Human infection with Linguatula spp. occurs following consumption of raw or undercooked infected internal organs of the intermediate host and/or consumption of water and/or vegetables contaminated with eggs released from final hosts. The aim of this study was to determine prevalence and risk factors of Linguatula spp. in sheep, cattle, buffalo, goats and camels slaughtered at the Tabriz abattoir, Iran. In addition, effect of temperature and sodium chloride (NaCl) on survival time of Linguatula spp. nymphs was assessed. For this purpose, 25,520 mesenteric lymph nodes from 2552 animals and the livers and lungs from 656 animals were collected randomly and examined. To evaluate the effect of temperature and NaCl on the survival of Linguatula spp. nymphs in infected livers and lungs, 30 g of each liver and lung with dimensions of 2 × 3 × 4 cm, were exposed to temperatures of −20, 10, 50, 60 and 72 °C and NaCl concentrations of 5 %, 10 %, 15 % and 20 % for 3, 6, 12, 24, 48 and 72 h, in triplicate. Based on the mesenteric lymph nodes, 25.7 % (656 of 2552 animals) were infected with Linguatula spp. Of the 656 liver and lungs assessed, 141 (21.5 %) and 62 (9.5 %) were infected with Linguatula spp., respectively. The rate of infection of mesenteric lymph nodes in all animals was significant with age (P < 0.05), with more older animals infected. In regards to sex, except for camels, more female animals were infected than male animals (P < 0.05). There was a significant difference in survival of nymphs based on temperature and/or NaCl and time (P < 0.0001). At 72 h, all temperatures assessed except 10 °C, resulted in all nymphs being inactivated. Sodium chloride was more effective against Linguatula spp. nymphs in livers than in lungs with 100 % efficacy only achieved against nymphs in livers at 20 % concentration after 48 h and at 10 and 15 % concentration after 72 h. Based on these results, heating and application of common salt as a food preservative in meat products reduces the survival time of Linguatula spp. nymphs and their use could decrease the risk of food-born microorganisms.