In the present world a significant threat to human health is posed by zoonotic diseases. Helminth parasites of ruminants are one of the most common zoonotic organisms on the planet. Among them, trichostrongylid nematodes of ruminants, found worldwide, parasitize humans in different parts of the world with varying rates of incidence, particularly among rural and tribal communities with poor hygiene, pastoral livelihood and poor access to health services. In the Trichostrongyloidea superfamily, Haemonchus contortus, Teladorsagia circumcincta, Marshallagia marshalli, Nematodirus abnormalis and Trichostrongylus spp. are zoonotic in nature. Species of the genus Trichostrongylus are the most prevalent gastrointestinal nematode parasites of ruminants that transmit to humans. This parasite is prevalent in pastoral communities around the world and causes gastrointestinal complications with hypereosinophilia which is typically treated with anthelmintic therapy. The scientific literature from 1938 to 2022 revealed the occasional incidence of trichostrongylosis throughout the world with abdominal complications and hypereosinophilia as the predominant manifestation in humans. The primary means of transmission of Trichostrongylus to humans was found to be close contact with small ruminants and food contaminated by their faeces. Studies revealed that conventional stool examination methods such as formalin-ethyl acetate concentration or Willi's technique combined with polymerase chain reaction-based approaches are important for the accurate diagnosis of human trichostrongylosis. This review further found that interleukin 33, immunoglobulin E, immunoglobulin G1, immunoglobulin G2, immunoglobulin M, histamine, leukotriene C4, 6-keto prostaglandin F1α, and thromboxane B2 are vital in the fight against Trichostrongylus infection with mast cells playing a key role. This review focuses on the prevalence, pathogenicity and immunological aspects of Trichostrongylus spp. in humans.

The levels of nematode egg production in goats and the availability of infective larvae (L3) on pasture were investigated on a dairy unit in New South Wales, Australia. The output of eggs by adult goats was always above 300 epg. The profile of the graph of larval availability in herbage paralleled those for temperature and rainfall, suggesting that larval peaks occurred when the temperature and availability of moisture were optimal. The dominant genus was Trichostrongylus, followed by Haemonchus, then Ostertagia. A larger proportion of Haemonchus larvae in the cultures of faeces were collected during the summer months.

Five experimental grass paddocks were sequentially contaminated with fresh bovine faeces containing known numbers of eggs of predominantly Haemonchus and Cooperia spp. during the 1984/85 dry season (November to March). Faecal, herbage and soil samples were examined at regular intervals between November and June in order to determine the rate of development and mortality of infective larvae (L3) in faeces, the pattern of herbage infestation with L3 and the role of faeces and soil as reservoirs of L3 during the dry season and early rains. L3 first appeared in faeces approximately 4 days post contamination (PC) and peak counts were obtained 28, 14, 7 and 14 days PC in the paddocks contaminated in December, January, February and March, respectively. The counts initially declined linearly at the rate of approximately 7535 L3/week and 10 947 L3/week in P2 and P4 respectively, due primarily to mortality but later there was an accelerated fall in the counts as the surviving L3 moved out of the faecal pads onto herbage. The overall trend of faecal larval populations in each paddock was therefore distinctly curvilinear. Although large numbers of L3 were present inside dry faecal pads in most paddocks throughout the dry season, none migrated on to herbage at that time of the year. Translation of L3 to herbage was very rapid and occurred simultaneously in all the paddocks 24 hours following the first heavy rainfall in late March. Consequently peak herbage infestations in all paddocks were coincident and occurred a few days after commencement of larval migration. The closer to the end of the dry season the contaminations were carried out, the larger were the subsequent early rains rise and the peak herbage infestation and the longer this infestation survived on herbage. No L3 were recovered from soil throughout the study, which suggests that faecal pads were the sole reservoir of L3 during the dry season and hence the source of the early rains herbage infestation.

Members of the genus Trichostrongylus, such as T. vitrinus, being endemic in Northern Europe, are among the principal causative nematodes which contribute to parasitic gastro-enteritis in sheep world-wide, inhabiting the proximal small intestine and causing damage to the mucosa. This results in impaired nutrient absorption as well as a pronounced inflammatory response with cellular infiltration of the mucosa, including a pronounced mast cell response. These mast cells release serine proteinases that enhance the passage of effector cells and macromolecules across epithelial boundaries and into direct contact with the invading parasite. The adult and larval stages of T. vitrinus release a number of serine proteinases in vitro that may contribute to tissue invasion and nutrient acquisition in vivo. This study describes the molecular cloning and characterization of a serine proteinase inhibitor (serpin)Sequence reported here is available with GenBank Accession number Y12233. that is present in extracts of all the parasitic stages, becoming more abundant as the life-cycle progresses. The serpin is present in the in vitro excretory/secretory products (ES) of 4th-stage larval and adult parasites, being more abundant in the former. The serpin was expressed in E. coli and the recombinant protein was a potent inhibitor of several host serine proteinases including mast cell proteinases. The serpin may regulate the activity of the parasite serine proteinases or it may modulate the host immune response to the parasite by inhibiting the activity of serine proteinases released from host inflammatory cells.