Epidemiology of Human Toxocariasis: An Update.

Article Citation: Al-Awadhi, M. A. (2020, October 17). Epidemiology of human toxocariasis: An update. Kuwaiti Journal of Medical Parasitology. https://q8jmp.com/epidemiology-human-toxocariasis/

Toxocariasis is a zoonotic parasitic infection (parasite is transmitted from animals to humans). Toxocara canis and Toxocara cati infect dogs and cats, respectively, and produce eggs in the animal intestines which are then shed through defecation into the environment. Humans contract the infection upon accidental ingestion of Toxocara spp. eggs from the environment (e.g. contaminated soil, especially children in playgrounds) or contaminated food such as unwashed vegetables, or by direct contact with contaminated pet cat and dog fur. Human infection by Toxocara spp. larvae usually remains asymptomatic or manifests as mild symptoms. However, less commonly, the infection can progress to cause ocular toxocariasis (damage to retina or other eye tissue leading to blindness, usually in one eye) or visceral toxocariasis (damage to organs such as the liver or brain). Globally, nearly 1 in 5 people are infected with Toxocara spp. (Rostami et al., 2019).

Due to the ubiquitous nature of Toxocara spp., a PubMed search was performed for updated studies published in the year 2020 related to the epidemiology of human toxocariasis. We found a total of 19 studies which reported the seroprevalence rates of toxocariasis in humans. The average seroprevalence rate of human toxocariasis from 19 published studies was 27.9% and ranged from 1.4% to 92.4%. The highest rates were recorded among pregnant women in Nigeria (92.4%), followed by schoolchildren in Honduras (88.6%) and the general population in Ghana (62.0%). In Iran, 6 studies were reported from which the highest rate (28.6%) was found among multiple sclerosis patients. The seroprevalence of Toxocara spp. infection among patients with eosinophilia was reported in Ecuador (38.0%) and South Korea (22.2%). Among children, seroprevalence rates were reported in 4 studies from Honduras (88.6%), Thailand (58.2%), Mexico (13.8%) and the USA (3.6%).

It is clear from recent studies that African and Southeast Asian countries had the highest prevalence of human toxocariasis, whereas industrialized countries including the USA and European countries showed the lowest seroprevalence rates. It is important to mention that in the USA and most European countries, stray cats and dogs are usually removed from the streets by the authorities and are sheltered until adopted or put down. Such measures probably reduce the parasitic load from soil environments and consequent exposure of humans to Toxocara spp. eggs during outdoor activities. Furthermore, it is a common practice in these countries that pet owners remove and properly dispose of pet feces from the playground and park soil after defecation, which further decreases the prevalence of Toxocara spp. eggs in the environment.

Human toxocariasis epidemiology studies published in 2020 (PubMed).

Study GroupCountry / Region Seroprevalence RateReference
Pregnant womenNigeria92.4%Ikotun et al., 2020
SchoolchildrenHonduras88.6%Hernández et al., 2020
General populationGhana62.0%Boyko et al., 2020
PatientsVietnam59.0%De et al., 2020
SchoolchildrenThailand58.2%Phasuk et al., 2020
Patients with eosinophiliaEcuador38.0%Morales-Yánez et al., 2020
Patients with multiple sclerosisIran28.6%Khalili et al., 2020
Patients with eosinophiliaSouth Korea22.2%Song et al., 2020
Pregnant womenIran21.2%Raissi et al., 2020
General populationRussia16.0%Akhmadishina et al., 2020
General populationIran14.5%Asadi et al., 2020
ChildrenMexico13.8%Ponce-Macotela et al., 2020
General populationIran11.0%Abbaszadeh Afshar et al., 2020
General populationIran6.5%Shafiei et al., 2020
Recent immigrantsUSA6.4%Herrick et al., 2020
General populationEurope6.2%Strube et al., 2020
AdultsMexico4.7%Ponce-Macotela et al., 2020
General populationSlovakia3.7%Fecková et al., 2020
SchoolchildrenUSA3.6%Bradbury et al., 2020
NomadsIran1.4%Arefkhah et al., 2020


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