Toxoplasma gondii, Sarcocystis sp. and Neospora caninum-like parasites in seals from northern and eastern Canada: potential risk to consumers

Environmental stressors and zoonoses in the Arctic: Learning from the past to prepare for the future

The risk of zoonotic disease transmission from animals to humans is elevated for people in close contact with domestic and wild animals. About three-quarters of all known human infectious diseases are zoonotic, and potential health impacts of these diseases are higher where infectious disease surveillance and access to health care and public health services are limited. This is especially the case for remote circumarctic regions, where drivers for endemic, emerging, and re-emerging zoonotic diseases include anthropogenic influences, such as pollution by long-range transport of industrial chemicals, climate change, loss of biodiversity and ecosystem alterations. In addition to these, indirect effects including natural changes in food web dynamics, appearance of invasive species and thawing permafrost also affect the risk of zoonotic disease spill-over. In other words, the Arctic represents a changing world where pollution, loss of biodiversity and habitat, and maritime activity are likely driving forward occurrence of infectious diseases. As a broad international consortium with a wide range of expertise, we here describe a selection of case studies highlighting the importance of a One Health approach to zoonoses in the circumarctic, encompassing human health, animal health, and environmental health aspects. The cases highlight critical gaps in monitoring and current knowledge, focusing on environmental stressors and lifestyle factors, and they are examples of current occurrences in the Arctic that inform on critically needed actions to prepare us for the future. Through these presentations, we recommend measures to enhance awareness and management of existing and emerging zoonoses with epidemic and pandemic potential while also focusing on the impacts of various environmental stressors and lifestyle factors on zoonoses in the Arctic.

Toxoplasma gondii DNA in Tissues of Anadromous Arctic Charr, Salvelinus alpinus, Collected From Nunavik, Québec, Canada

BACKGROUND

Toxoplasma gondii is a very common zoonotic parasite in humans and animals worldwide. Human seroprevalence is high in some regions of Canada's North and is thought to be associated with the consumption of traditionally prepared country foods, such as caribou, walrus, ringed seal and beluga. While numerous studies have reported on the prevalence of T. gondii in these animals, in the general absence of felid definitive hosts in the North there has been considerable debate regarding the source of infection, particularly in marine mammals. It has been proposed that fish could be involved in this transmission.

AIMS

The objectives of the present study were to perform a targeted survey to determine the prevalence of T. gondii DNA in various tissues of anadromous Arctic charr sampled in Nunavik, Québec, and to investigate the possible role of this commonly consumed fish in the transmission of infection to humans and marine mammals in Canada's North.

METHODS AND RESULTS

A total of 126 individual Arctic charr were sampled from several sites in Nunavik, and various tissues were tested for the presence of T. gondii DNA using PCR. Overall, 12 out of 126 (9.5%) Arctic charr tested in the present study were PCR-positive, as confirmed by DNA sequencing. Brain tissue was most commonly found to be positive, followed by heart tissue, while none of the dorsal muscle samples tested were positive.

CONCLUSIONS

Although the presence of T. gondii DNA in brain and heart tissues of Arctic charr is very intriguing, infection in these fish, and their possible role in the transmission of this parasite to humans and marine mammals, will need to be confirmed using mouse bioassays. Arctic charr are likely exposed to T. gondii through the ingestion of oocysts transported by surface water and ocean currents from more southerly regions where the definitive felid hosts are more abundant. If infection in Arctic charr can be confirmed, it is possible that these fish could play an important role in the transmission of toxoplasmosis to Inuit, either directly through the consumption of raw fish or indirectly through the infection of fish-eating marine mammals harvested as country foods.

The geographic distribution, and the biotic and abiotic predictors of select zoonotic pathogen detections in Canadian polar bears

Increasing Arctic temperatures are facilitating the northward expansion of more southerly hosts, vectors, and pathogens, exposing naïve populations to pathogens not typical at northern latitudes. To understand such rapidly changing host-pathogen dynamics, we need sensitive and robust surveillance tools. Here, we use a novel multiplexed magnetic-capture and droplet digital PCR (ddPCR) tool to assess a sentinel Arctic species, the polar bear (Ursus maritimus; n = 68), for the presence of five zoonotic pathogens (Erysipelothrix rhusiopathiae, Francisella tularensis, Mycobacterium tuberculosis complex, Toxoplasma gondii and Trichinella spp.), and observe associations between pathogen presence and biotic and abiotic predictors. We made two novel detections: the first detection of a Mycobacterium tuberculosis complex member in Arctic wildlife and the first of E. rhusiopathiae in a polar bear. We found a prevalence of 37% for E. rhusiopathiae, 16% for F. tularensis, 29% for Mycobacterium tuberculosis complex, 18% for T. gondii, and 75% for Trichinella spp. We also identify associations with bear age (Trichinella spp.), harvest season (F. tularensis and MTBC), and human settlements (E. rhusiopathiae, F. tularensis, MTBC, and Trichinella spp.). We demonstrate that monitoring a sentinel species, the polar bear, could be a powerful tool in disease surveillance and highlight the need to better characterize pathogen distributions and diversity in the Arctic.

Detection of Toxoplasma gondii and Sarcocystis sp. in the meat of common minke whale (Balaenoptera acutorostrata): A case of suspected food poisoning in Japan

A case of suspected food poisoning related to the consumption of raw meat from a common minke whale (Balaenoptera acutorostrata) was reported in Tokyo, Japan, in June 2020. Microscopic analysis revealed tissue cysts of Toxoplasma gondii and sarcocysts of Sarcocystis sp. in whale meat. The SAG2 and ITS1 region sequences of T. gondii were detected in the DNA extracted from the meat. Genotyping of the multilocus nested PCR-RFLP using the genetic markers SAG1, SAG2 (5'- SAG2, 3'-SAG2, and alt. SAG2), SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico revealed that the genotype of T. gondii was type II, with a type I pattern for the L358 locus. In the phylogenetic analyses of the six loci (GRA6, GRA7, SAG1, HP2, UPRT1, and UPRT7), these sequences clustered into haplogroup 2. Moreover, the sequences of the virulence-related genes ROP5 and ROP18 of T. gondii isolated from whale meat were similar to those of the type II ME49 reference strain. Sequence analyses of the mtDNA cox1 gene, 18S rRNA gene, and ITS1 region indicated the highest similarity of sarcocyst isolated from whale meat to Sarcocystis species that infect birds or carnivores as intermediate hosts; however, the species could not be identified. To our knowledge, this is the first report of T. gondii and Sarcocystis spp. being detected in same whale meat ingested by patients involved in a suspected food poisoning case in Japan.

A Review of Circumpolar Arctic Marine Mammal Health-A Call to Action in a Time of Rapid Environmental Change

The impacts of climate change on the health of marine mammals are increasingly being recognised. Given the rapid rate of environmental change in the Arctic, the potential ramifications on the health of marine mammals in this region are a particular concern. There are eleven endemic Arctic marine mammal species (AMMs) comprising three cetaceans, seven pinnipeds, and the polar bear (Ursus maritimus). All of these species are dependent on sea ice for survival, particularly those requiring ice for breeding. As air and water temperatures increase, additional species previously non-resident in Arctic waters are extending their ranges northward, leading to greater species overlaps and a concomitant increased risk of disease transmission. In this study, we review the literature documenting disease presence in Arctic marine mammals to understand the current causes of morbidity and mortality in these species and forecast future disease issues. Our review highlights potential pathogen occurrence in a changing Arctic environment, discussing surveillance methods for 35 specific pathogens, identifying risk factors associated with these diseases, as well as making recommendations for future monitoring for emerging pathogens. Several of the pathogens discussed have the potential to cause unusual mortality events in AMMs. Brucella, morbillivirus, influenza A virus, and Toxoplasma gondii are all of concern, particularly with the relative naivety of the immune systems of endemic Arctic species. There is a clear need for increased surveillance to understand baseline disease levels and address the gravity of the predicted impacts of climate change on marine mammal species.

Foodborne protozoan parasites in fresh mussels and oysters purchased at retail in Canada

Studies worldwide have reported the presence of protozoan parasites in a variety of commercial bivalve shellfish. The uptake of these parasites by shellfish occurs during filter feeding in faecally-contaminated waters. The objective of the present study was to determine the prevalence of Giardia, Cryptosporidium and Toxoplasma in fresh, live shellfish purchased in three Canadian provinces as part of the retail surveillance activities led by FoodNet Canada (Public Health Agency of Canada). Packages containing mussels (n = 253) or oysters (n = 130) were purchased at grocery stores in FoodNet Canada sentinel sites on a biweekly basis throughout 2018 and 2019, and shipped in coolers to Health Canada for testing. A small number of packages were not tested due to insufficient quantity or poor quality. Following DNA extraction from homogenized, pooled tissues, nested PCR and DNA sequencing were used to detect parasite-specific sequences. Epifluorescence microscopy was used to confirm the presence of intact cysts and oocysts in sequence-confirmed PCR-positive samples. Giardia duodenalis DNA was present in 2.4 % of 247 packages of mussels and 4.0 % of 125 packages of oysters, while Cryptosporidium parvum DNA was present in 5.3 % of 247 packages of mussels and 7.2 % of 125 packages of oysters. Toxoplasma gondii DNA was only found in mussels in 2018 (1.6 % of 249 packages). Parasite DNA was detected in shellfish purchased in all three Canadian provinces sampled, and there was no apparent seasonal variation in prevalence. While the present study did not test for viability, parasites are known to survive for long periods in the marine environment, and these findings suggest that there is a risk of infection, especially when shellfish are consumed raw.

Histomorphological stratification of blubber of three dolphin species from sub-tropical waters

Blubber is a highly specialised and dynamic tissue unique to marine mammals and presents a reflection of the individuals' nutrition, environment, and life history traits. Few studies have investigated the histomorphology of cetacean blubber in sub-tropical environments. The aim of this study was to investigate the blubber histomorphology of three different dolphin species off the sub-tropical KwaZulu-Natal coast, South Africa, using adipocyte cell size, number and density. Blubber tissue samples from the saddle area of 43 incidentally bycaught animals (4 Sousa plumbea, 36 Tursiops aduncus and 3 Delphinus delphis) were used to compare cell parameters between blubber layers. Samples were divided into upper third (corresponding to the superficial layer closest to the epidermis), middle third, and lower third (corresponding to the deep layer). For T. aduncus, factors potentially affecting blubber histomorphology, such as sex, age class and season, were also assessed. Our results showed that no stratification was present in S. plumbea, which could be ascribed to the species' warmer inshore habitat, large body size and apparent lower mobility. For T. aduncus and D. capensis, however, blubber stratification was determined, characterised by a gradual transition of cell size, number and density between layers rather than clearly defined layers. Significant differences in adipocyte cell number and density were found for different sexes and age classes of T. aduncus. However, there were no significant differences between seasons, which was attributed to the small temperature differences between seasons. This study represents the first investigation on odontocete blubber histomorphology in subtropical waters. It is recommended that future studies investigate blubber lipid content, while also taking into consideration the reproductive status of the females and the temperature range of their study area. It is hoped that our results, in conjunction with histopathology and other health indicators, could assist in assessing health and body condition. This article is protected by copyright. All rights reserved.

A systematic review, meta-analysis and meta-regression of the global prevalence of Toxoplasma gondii infection in wild marine mammals and associations with epidemiological variables

Toxoplasma gondii infection in wild marine mammals is a growing problem and is associated with adverse impacts on marine animal health and public health. This systematic review, meta-analysis and meta-regression estimates the global prevalence of T. gondii infection in wild marine mammals and analyzes the association between T. gondii infection and epidemiological variables. PubMed, Web of Science, Science Direct, China National Knowledge Infrastructure, and Wanfang Data databases were searched until 30 May 2021. Eighty-four studies (n = 14,931 wild marine mammals from 15 families) were identified from literature. The overall pooled prevalence of T. gondii infection was 22.44% (3,848/14,931; 95% confidence interval (CI): 17.29% - 8.04%). The prevalence in adult animals 21.88% (798/3119; 95% CI: 13.40 -31.59) was higher than in the younger age groups. North America had a higher prevalence 29.92% (2756/9243; 95% CI: 21.77 - 38.77) compared with other continents. At the country level, the highest prevalence was found in Spain 44.26% (19/88; 95%CI: 5.21 - 88.54). Regarding climatic variables, the highest prevalence was found in areas with a mean annual temperature >20°C 36.28% (171/562; 95% CI: 6.36 - 73.61) and areas with an annual precipitation >800 mm 26.92% (1341/5042; 95% CI: 18.20 - 36.59). The subgroup and meta-regression analyses showed that study-level covariates, including age, country, continent, and mean temperature, partly explained the between-study heterogeneity. Further studies are needed to investigate the source of terrestrial to aquatic dissemination of T. gondii oocysts, the fate of this parasite in marine habitat and its effects on wild marine mammals. This article is protected by copyright. All rights reserved.

Raw meat based diet (RMBD) for household pets as potential door opener to parasitic load of domestic and urban environment. Revival of understated zoonotic hazards? A review

RMBD (acronym of Raw Meat Based Diet) and BARF diets (acronym for Biologically Appropriate Raw Food or Bones and Raw Food) account dietary regimens based on raw ingredients (including raw meat), popular in pet feeding. Animal tissues and organs as well as other uncooked ingredients are more and more popularly used by pet owners to feed household pets. However, the increased risk of exposure to microbiological and parasitic agents poses the question as to whether such diets may be recommendable to be handled and offered to domestic cats and dogs co-living in domestic and urban environment. Above all, the threat of human and animal infections by parasites from raw meat fed to pets is not sufficiently explored and tracked, meanwhile deserving particular surveillance, instead. At this regard, raw meat feeding to pets may represent a route of exposure to the increased risk of environmental load. In fact, some parasites typically found in rural environment can be given the chance to complete their life-cycle, for the closeness between definitive and intermediate hosts. This is of particular concern, as potentially infected pets serving as definitive hosts can become a continuous source of environmental diffusion of parasites, both at domestic and urban level. The handling of raw meat requires adequate knowledge and awareness of the hygienic principles to prevent the onset of disorders related to both manipulation by pet owners and uncooked food consumption by the pet. This review aimed to shed a comprehensive overview of the hygienic aspects related to raw pet feeding, as to handling of raw meat in domestic environment, with special emphasis on parasitic agents and related zoonotic hazards.

Seroprevalence of Toxoplasma gondii in Pinnipeds under Human Care and in Wild Pinnipeds

Toxoplasma gondii infection has been reported in numerous species of marine mammals, some of them with fatal consequences. A serosurvey for T. gondii infection was conducted in pinnipeds from an oceanographic park in Portugal (n = 60); stranded pinnipeds on the Portuguese coast (n = 10); and pinnipeds captured in Lorenzensplate, Germany (n = 99). Sera from 169 pinnipeds were tested for the presence of antibodies to T. gondii by the modified agglutination test with a cut-off titre of 25. An overall seroprevalence of 8.9% (95% confidence interval: 5.1–14.2) was observed. Antibody titres of 25, 50, 100, 1600 and ≥3200 were found in five (33.3%), two (13.3%), five (33.3%), one (6.7%) and two (13.3%) animals, respectively. Pinnipeds under human care had a seroprevalence of 20.0% (12/60), in contrast to 2.8% (3/109) in wild pinnipeds (p < 0.001). General results suggest a low exposure of wild pinnipeds to T. gondii, while the seroprevalence found in pinnipeds under human care highlights the importance of carrying out further studies. This is the first serological survey of T. gondii in pinnipeds in Portugal and the first infection report in South African fur seal (Arctocephalus pusillus pusillus).

Long-term increases in pathogen seroprevalence in polar bears (Ursus maritimus) influenced by climate change

The influence of climate change on wildlife disease dynamics is a burgeoning conservation and human health issue, but few long-term studies empirically link climate to pathogen prevalence. Polar bears (Ursus maritimus) are vulnerable to the negative impacts of sea ice loss as a result of accelerated Arctic warming. While studies have associated changes in polar bear body condition, reproductive output, survival, and abundance to reductions in sea ice, no long-term studies have documented the impact of climate change on pathogen exposure. We examined 425 serum samples from 381 adult polar bears, collected in western Hudson Bay (WH), Canada, for antibodies to selected pathogens across three time periods: 1986-1989 (n = 157), 1995-1998 (n = 159) and 2015-2017 (n = 109). We ran serological assays for antibodies to seven pathogens: Toxoplasma gondii, Neospora caninum, Trichinella spp., Francisella tularensis, Bordetella bronchiseptica, canine morbillivirus (CDV) and canine parvovirus (CPV). Seroprevalence of zoonotic parasites (T. gondii, Trichinella spp.) and bacterial pathogens (F. tularensis, B. bronchiseptica) increased significantly between 1986-1989 and 1995-1998, ranging from +6.2% to +20.8%, with T. gondii continuing to increase into 2015-2017 (+25.8% overall). Seroprevalence of viral pathogens (CDV, CPV) and N. caninum did not change with time. Toxoplasma gondii seroprevalence was higher following wetter summers, while seroprevalences of Trichinella spp. and B. bronchiseptica were positively correlated with hotter summers. Seroprevalence of antibodies to F. tularensis increased following years polar bears spent more days on land, and polar bears previously captured in human settlements were more likely to be seropositive for Trichinella spp. As the Arctic has warmed due to climate change, zoonotic pathogen exposure in WH polar bears has increased, driven by numerous altered ecosystem pathways.

Epidemiology associated with the exposure to Toxoplasma gondii in Nunavik's Inuit population using the 2017 Qanuilirpitaa cross-sectional health survey

Foci of high seroprevalence against Toxoplasma gondii are observed in Nunavik, the Inuit land of Northern Quebec (Canada). Considering the rare occurrence of felids in the region, exposure is suspected to be driven by water- and food-borne transmission routes. Hypotheses were that drinking untreated water from natural sources and eating country food mostly raw increased the risk of exposure to the parasite. Data from 1,300 Inuit participants of the 2017 Nunavik Health Survey were included in three weighted robust Poisson regression models. The effect of three types of exposure variables: (1) water treatment (yes/no) and if country food was mostly eaten raw (yes/no); (2) main source of drinking water (bottled/municipal/natural) and frequency of country food consumption (continuous) and (3) drinking water risk (low/intermediate/high) and frequency of a raw country food consumption (continuous), on the presence of Toxoplasma antibodies were estimated. Models were adjusted for age, sex and ecological region, with multiple sensitivity analyses being performed. Toxoplasma gondii seroprevalences were consistently correlated with age quadratically, sex (prevalence ratio = PR_woman/man ranged from 1.18 to 1.22), ecological region (PR_{HudsonBay/HudsonStrait} ranged from 2.18 to 2.41; PR_{HudsonBay/UngavaBay} ranged from 1.52 to 1.59) and consuming bivalve mollusc/urchin (PR varied from 1.02 to 1.21) across all three models. Each increase of two consumptions per month of beluga (PR ranged from 1.01 to 1.03), seal liver (PR ranged from 1.01 to 1.02) and goose (PR ranged from 1.01 to 1.02) were also associated with seropositivity, albeit more clearly in models 2 and 3, while drinking water mainly from natural (PR of 1.47) or municipal (PR = 1.42) sources compared to bottled water, was correlated with seroprevalence, although results were compatible with the null. Our results suggest that both the oocyst- (mollusc/urchin, drinking water) and cyst-borne (walrus, seal liver and goose) transmission pathways could be present in Nunavik.

Toxoplasma gondii in mollusks and cold-blooded animals: a systematic review

Toxoplasma gondii (T. gondii) is known for its ability to infect warm-blooded vertebrates. Although T. gondii does not appear to parasitize cold-blooded animals, the occurrence of T. gondii infection in marine mammals raises concerns that cold-blooded animals (frogs, toad, turtles, crocodiles, snakes, and fish) and shellfish are potential sources of T. gondii. Therefore, this systematic review aimed to determine the prevalence of T. gondii in mollusks and cold-blooded animals worldwide. We searched PubMed, ScienceDirect, ProQuest, Scopus, and Web of Science from inception to 1 August 2020 for eligible papers in the English language and identified 26 articles that reported the prevalence of T. gondii in mollusks and cold-blooded animals. These articles were subsequently reviewed and data extracted using a standard form. In total, 26 studies [involving 9 cross-sectional studies including 2988 samples of cold-blooded animals (129 positive cases for T. gondii) and 18 cross-sectional studies entailing 13 447 samples of shellfish (692 positive cases for T. gondii)] were included in this study. Although this study showed that shellfish and cold-blooded animals could be potential sources of T. gondii for humans and other hosts that feed on them, further investigations are recommended to determine the prevalence of T. gondii in shellfish and cold-blooded animals.

Atypical Toxoplasmosis in a Mediterranean Monk Seal (Monachus monachus) Pup

The Mediterranean monk seal (Monachus monachus) is the rarest species of pinniped in the world. Necropsy of a Mediterranean monk seal pup that stranded alive on the southern Adriatic Italian coast and died a few hours later revealed co-infection by cetacean morbillivirus (CeMV) and Toxoplasma gondii. Pathological lesions included a multifocal, moderate to severe, necrotizing myocarditis and a diffuse, chronic, moderate interstitial pneumonia with bronchial and bronchiolar epithelial hyperplasia. Lesions of atypical necrotizing arteritis were seen in the aorta and major pulmonary arteries in association with the presence T. gondii organisms. Severe haemorrhagic foci and lesions of non-suppurative meningoencephalitis, together with the presence of protozoal cysts, were seen in the brain. Co-infection of CeMV and T. gondii has not been previously reported in monk seals. The vascular lesions found in this animal can be considered atypical because they have not been reported in other terrestrial or marine mammal species. The disseminated toxoplasmosis associated with the unusual vascular and haemorrhagic brain lesions could be related to the immunosuppressive effects of CeMV infection.

Clams and potential foodborne Toxoplasma gondii in Nunavut, Canada

The prevalence of Toxoplasma gondii exposure in Inuit living in Nunavut (20%) is twice that of the US (11%); however, routes of exposure for Inuit communities in North America are unclear. Exposure to T. gondii in humans has been linked with consumption of raw or undercooked shellfish that can accumulate environmentally resistant oocysts. Bivalve shellfish, such as clams, are an important, nutritious, affordable and accessible source of food in many Northern Communities. To date, presence of T. gondii in clams in Northern Canada has not been reported. In this study, we tested for T. gondii presence in clams (Mya truncata) that were harvested in Iqaluit, Nunavut over a 1-week period in September 2016. Of 390 clams, eight (2.1%) were confirmed to contain T. gondii DNA (≥99.7% identity), as determined using polymerase chain reaction (PCR) and sequence confirmation. Additionally, three clams (0.8%) were confirmed to contain Neospora caninum-like DNA (≥99.2% identity). While N. caninum is not known to be a zoonotic pathogen, its presence in shellfish indicates contamination of the nearshore with canid faeces, and the potential for marine mammal exposure through marine food webs. Notably, the PCR assay employed in this study does not discriminate between viable and non-viable parasites. These findings suggest a possible route for parasite exposure through shellfish in Iqaluit, Nunavut. Future research employing viability testing will further inform public health messaging on the infectious potential of T. gondii in shellfish.

Exposure of the Gulf of St. Lawrence grey seal Halichoerus grypus population to potentially zoonotic infectious agents

The population of grey seals Halichoerus grypus in Canadian waters is currently used as a commercial source of meat for human consumption. As with domestic livestock, it is important to understand the occurrence in these seals of infectious agents that may be of public health significance and thus ensure appropriate measures are in place to avoid zoonotic transmission. This study examined the prevalence of antibodies against Brucella spp., Erysipelothrix rhusiopathiae, 6 serovars of Leptospira interrogans, and Toxoplasma gondii in 59 grey seals and determined by polymerase chain reaction (PCR) the presence of these potentially zoonotic agents in specific organs and tissues of seropositive animals. The presence of encysted Trichinella spp. larvae was also investigated by digestion of tongue, diaphragm and other muscle samples, but none were detected. Seroprevalence against Brucella spp. and E. rhusiopathiae was low (5 and 3%, respectively). All 59 seals tested had antibodies against L. interrogans, but no carrier of this bacterium was detected by PCR. Seroprevalence against T. gondii was 53%, and DNA of this protozoan was detected by PCR in 11/30 (37%) seropositive animals. Standard sanitary measures mandatory for commercialization of meat products for human consumption should greatly reduce the potential for exposure to these infectious agents. However, special consideration should be given to freezing seal meat for at least 3 d to ensure destruction of tissue cysts of T. gondii.

Recent epidemiologic and clinical importance of Toxoplasma gondii infections in marine mammals: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. T. gondii causes mortality in several species of marine mammals, including threatened Southern sea otters (Enhydra lutris) and endangered Hawaiian monk seals (Monachus schauinslandi). Marine mammals are now considered sentinels for environmental exposure to protozoan agents contaminating marine waters, including T. gondii oocysts. Marine mammals also serve as food for humans and can result in foodborne T. gondii infections in humans. The present review summarizes worldwide information on the prevalence of clinical and subclinical infections, epidemiology, and genetic diversity of T. gondii infecting marine mammals in the past decade. The role of genetic types of T. gondii and clinical disease is discussed.