Toxoplasma gondii: How an Amazonian parasite became an Inuit health issue

Abstract

Toxoplasma gondii is a protozoan parasite that originated in the Amazon. Felids (mammals in the cat family) are the only definitive hosts. These animals shed large numbers of infectious oocysts into the environment, which can subsequently infect many intermediate hosts, including birds, mammals and, possibly, fish. Human T. gondii seroprevalence is high in some parts of the Canadian Arctic and is associated with adverse health consequences among Inuit population. Since the range of felids does not extend to the Arctic, it is not immediately obvious how this parasite got from the Amazon to the Arctic. The objectives of this overview are to summarize the health impacts of T. gondii infection in Inuit in Canada's North and to consider how this infection could have reach them. This article reviews the prevalence of T. gondii infection in terrestrial and marine animals in the Canadian Arctic and discusses their potential role in the foodborne transmission of this parasite to humans. Two distribution factors seem plausible. First, felids in more southern habitats may release infectious oocysts into waterways. As these oocysts remain viable for months, they can be transported northward via rivers and ocean currents and could infect Arctic fish and eventually the marine mammals that prey on the fish. Second, migratory terrestrial and marine intermediate hosts may be responsible for carrying T. gondii tissue cysts to the Arctic, where they may then pass on the infection to carnivores. The most likely source of T. gondii in Inuit is from the consumption of traditionally-prepared country foods including meat and organs from intermediate hosts, which may be consumed raw. With climate change, northward migration of felids may increase the prevalence of T. gondii in Arctic wildlife.

Implications of Zoonoses From Hunting and Use of Wildlife in North American Arctic and Boreal Biomes: Pandemic Potential, Monitoring, and Mitigation

“…Migratory terrestrial and marine intermediate hosts have been implicated in the introduction of other zoonoses to northern regions. For example, human seroprevalence for the protozoan parasite Toxoplasma gondii is high in some parts of the Canadian Arctic, with infection associated with consumption of under-cooked country foods ( 306 ). The parasite, thought originally to be of South American origin, but now ubiquitous around the globe, has felids as the only known definitive host.…”

“…The parasite, thought originally to be of South American origin, but now ubiquitous around the globe, has felids as the only known definitive host. However, seropositive wildlife species have been detected in the Arctic, where wild felids do not occur, and hypotheses for arrival in the region include spread via migratory waterfowl or marine mammal intermediate hosts ( 306 , 307 ). As environmental conditions change, bacterial infections routinely reported from direct contact with, or ingestion of, fish in more southern regions may also become a greater concern for northern communities who depend on fish for subsistence and as part of their food sovereignty ( 126 ).…”

Asymmetric eye size in an infant

“…Canadian data are sparse, though some northern communities have reported seroprevalence rates of 60%, believed in part to be related to contaminated water sources and undercooked meat ingestion (4). In the United States, approximately 15% of women of childbearing age are infected (5). Meanwhile, rates of congenital toxoplasmosis in developed nations are variable, including the United States at <1, but France at >3/10,000 (2,6).…”

“…Universal prenatal maternal screening is currently not adopted in many countries (including Canada) due to low incidence, testing inadequacies, and a lack of proven prevention strategies to justify the cost. It is only recommended for high-risk females (immunosuppressed) or when fetal abnormalities are detected on ultrasound (5). As such, in Canada, emphasis has been placed on preventive strategies to reduce the risk of infection.…”

Clams and potential foodborne Toxoplasma gondii in Nunavut, Canada

“…Investigation of potential sources of T. gondii exposure in Iqaluit is particularly important since T. gondii seropositivity is prevalent in Northern Indigenous populations (Messier et al., 2008; Reiling & Dixon, 2019). The seroprevalence of T. gondii among Nunavik Inuit in Quebec is 59.8% (Messier et al., 2008), and seroprevalence across Nunavut in people ≥40 years old is approximately 20% (Egeland, 2010).…”