Toxoplasmosis: Understanding the Swine and Human Transmission Cycle
摘要
Toxoplasmosis is an infectious zoonotic parasitic disease caused by a protozoan parasite Toxoplasma gondii, infecting a wide range of mammals, birds, and humans (Scofano et al., 2023). It is considered as one of the major health concerns and ranks third worldwide for zoonosis (Hotea & Darabus, 2023). An estimated one-third of the global population has encountered this parasite (Rouba et al., 2019). Among foodborne illnesses in the USA, it is the second leading cause of death (Gao et al., 2016). Within the European Union, T. gondii stands as one of the most prevalent zoonotic agents in humans, with estimates suggesting it surpasses other parasitic infections such as salmonellosis and campylobacteriosis (Djurkovic-Djakovic et al., 2019). Traditionally, Toxoplasmosis has been attributed to cats, the only definitive host of the parasite have ability to release oocysts; however, 50% of cases in humans are foodborne (Herrero et al., 2016). Humans acquire infections mostly via ingestion of contaminated food and water containing sporulated oocysts, consuming raw or improperly cooked meat from infected or wild pigs with tissue cysts or by congenital route (Almeria & Dubey, 2021). Toxoplasmosis is more frequently reported among pigs and small ruminants within the livestock community, often manifesting as subclinical infections in pigs. This prevalence is notably observed in various settings, including free-ranging farms, outdoor or backyard small pig farms, as well as among farmed or hunted wild boars. Globally, the average seroprevalence of T. gondii in pigs stands at 13% in Europe, 21% in Africa, 25% in North America, 21% in Asia, and 23% in South America. Serological surveys have revealed that T. gondii exposure rates among domestic pigs globally can reach up to 30% (Foroutan et al., 2019; Rostami et al., 2017), with viable T. gondii isolated from pork tissues obtained during slaughter (Dubey, 2010). In humans, the diagnosis is performed using various methods like tissue culture isolation, molecular methods (PCR), serology, and histopathology. Traditionally, the gold standard for diagnosing Toxoplasma infection in food animals involved bioassays in mice or cats. However, epidemiological surveys commonly rely on serological methods including the modified agglutination test (MAT), enzyme-linked immunosorbent assay, indirect fluorescent assay (IFA), Latex agglutination tests (LAT), Sabin-Feldman dye test (SFDT), or a combination of methods (Elsalem, 2024). This chapter provides an overview of toxoplasmosis focusing mainly on etiology, transmission route, life cycle, potential risk factors supporting the T. gondii infections in human and animals and their prevention and control strategies. The chapter will also highlight the significance of one health approach in integrated swine and health perspectives.