Trichinella spp. in Slaughtered Pigs of India: From Neglected Disease to an Emerging Food Safety Threat for Public Health

Abstract

Background. In India, Trichinella nematode worm remains highly neglected due to the paucity of research. Recent trichinellosis outbreaks in humans associated with pork meal in north India have highlighted an emerging food safety concern due to this neglected parasite. Aim. This study aimed to ascertain the existence of Trichinella species and to identify them in slaughtered pigs intended for human consumption in the Punjab and Uttaranchal regions of North India. Materials and Methods. A total of 1,194 slaughter pig tongue samples were screened in 239 pools using the double separatory funnel method for recovery of Trichinella larvae. The species of recovered larvae were confirmed by multiplex PCR assay and sequencing. A phylogenetic tree was constructed to ascertain the closest lineage. Results. This study reported 3.77% and 1.26% Trichinella positivity in pooled and individual pig samples, respectively. Pigs slaughtered in Punjab reported higher positivity (1.73%) than pigs in Uttaranchal (0.81%). Among all places, Jalandhar recorded highest positivity of 5.66%, followed by 2.22% in Nainital and 0.8% in Patiala, whereas none of the pig samples from Chandigarh, Ludhiana, Bathinda, Tehri Garhwal, Pauri Garhwal, Kashipur, Haridwar was positive. Molecular confirmation by PCR and sequencing confirmed the recovered Trichinella larvae as T. britovi and T. nelsoni. Conclusion. Trichinella parasite remained highly neglected in India; however, the detection of sylvatic Trichinella species in pigs intended for human consumption indicated the emergence of zoonotic foodborne risk at wild animal-domestic pig and human interfaces. To the best of our knowledge, this is the first study reporting T. britovi and T. nelsoni in pigs of North India. Trichinella positivity in slaughtered pigs is an early alarm for the emergence of foodborne risk from this neglected parasitic worm. Considering the importance of pigs as a source of meat and their role as a reservoir for Trichinella raised the food safety concern that warrants strict meat inspection and extensive studies on neglected parasites in India.

Traditional and Novel Foods as Vectors for Human Parasitic Diseases

“…Recent human outbreaks of trichinellosis linked to pig meal in northern India have highlighted the increasing threat to food safety posed by this overlooked parasite. A recent investigation found that 3.77% of pooled pig samples and 1.26% of individual pig samples tested positive for Trichinella [68]. The detection of Trichinella in slaughtered pigs signals the potential onset of foodborne illness from this neglected parasite.…”

“…The detection of Trichinella in slaughtered pigs signals the potential onset of foodborne illness from this neglected parasite. Given the importance of pigs as a meat source and their role as a reservoir for Trichinella, there is a pressing need for thorough meat inspection and comprehensive research on neglected parasites in India [68]. Toxoplasmosis, caused by the protozoan parasite T. gondii, infects both humans and livestock.…”

Predilection Site for the Meat Lover Trichinella spp Larvae and its Pathogenesis and Potency in Human Host

“…are distinctive because it has a direct life cycle [16]; which means that all three life cycle stages of the parasite, namely infective muscle larvae, adult, and new born larvae; Intestine-dwelling adults of Trichinella produce newborn larvae that enter the bloodstream and colonize skeletal muscle [17]. Infection is acquired by consumption of infected raw or undercooked meat or meat based comestibles [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

“…Asymptomatic infection could remain silent in human if it is only involving a minimum amount of larvae; Gastrointestinal symptoms manifested as a specific syndrome consist of nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort [27], starts very early to develop in case of unintentionally ingestion of hundreds of larvae, perhaps manifest itself clinically within the first 48 hours after consuming contaminated meat. The condition that followed by development of a series of condition which are serious, but scarcely fatal illness [5]. Clinical signs of the disease usually last 4-6 months, rarely longer (up to 2 years).…”

“…Even though its natural host varied, but infection among popular live stocks such as pigs [5][6][7][8] and other animals, e.g., horses [9], wild game meat (meat from an animal that is typically found in the wild and not raised domestically on a farm for mass consumption; usually free-roaming foragers and hunted for their meat) [10], rats [11], wild birds [12], wild and farmed reptiles [13] etc., which are raising public health concern [14], even though its global burden is much lower than that of other foodborne parasitic diseases (a mean estimated 76 healthy life years lost per billion people per year for human trichinellosis, globally [15].…”