Toxoplasma gondii infection in stranded St. Lawrence Estuary beluga Delphinapterus leucas in Quebec, Canada

Pathogen Exposure in White Whales (Delphinapterus leucas) in Svalbard, Norway

The Svalbard white whale (Delphinapterus leucas) population is one of the smallest in the world, making it particularly vulnerable to challenges such as climate change and pathogens. In this study, serum samples from live captured (2001−2016) white whales from this region were investigated for influenza A virus (IAV) antibodies (Abs) (n = 27) and RNA (n = 25); morbillivirus (MV) Abs (n = 3) and RNA (n = 25); Brucella spp. Abs; and Toxoplasma gondii Abs (n = 27). IAV Abs were found in a single adult male that was captured in Van Mijenfjorden in 2001, although no IAV RNA was detected. Brucella spp. Abs were found in 59% of the sample group (16/27). All MV and T. gondii results were negative. The results show that Svalbard white whales have been exposed to IAV and Brucella spp., although evidence of disease is lacking. However, dramatic changes in climate and marine ecosystems are taking place in the Arctic, so surveillance of health parameters, including pathogens, is critical for tracking changes in the status of this vulnerable population.

Prevalence and genotype of Toxoplasma gondii in stranded Hawaiian cetaceans

Toxoplasma gondii is a significant threat to endangered Hawaiian wildlife including birds and marine mammals. To estimate the prevalence of T. gondii in stranded cetaceans from 1997 to 2021 in Hawai'i, we tested tissues from 37 stranded spinner dolphins Stenella longirostris and 51 stranded individuals that represented 18 other cetacean species. DNA from cetacean tissue extracts were screened using a nested polymerase chain reaction (PCR) assay targeting the Toxoplasmatinae internal transcribed spacer 1 of the nuclear ribosomal DNA. A positive result was obtained in 9 tissues examined for each of 2 spinner dolphins out of 525 tissue samples analyzed by PCR. The PCR-positive spinner dolphins had disseminated acute toxoplasmosis with necrosis, inflammation, and intralesional protozoal cysts and tachyzoites in multiple organs. Discrete positive immunostaining for T. gondii was observed in all tissues tested including the adrenal gland, brain, liver, and lung. Both positive spinner dolphins were negative for cetacean morbillivirus. The T. gondii genotyping was performed by restriction fragment length polymorphism (PCR-RFLP) based on 10 genetic markers. The PCR-RFLP analysis revealed the T. gondii belonged to PCR-RFLP-ToxoDB genotype #24, previously detected in wild pig Sus scrofa in O'ahu, bobcats Lynx rufus from Mississippi, USA, and chickens Gallus gallus from Costa Rica and Brazil. These cases represent the first report of this genotype in aquatic mammals and the second and third reports of fatal disseminated T. gondii infection in stranded spinner dolphins from Hawai'i. Nearshore species, like spinner dolphins, may be at increased risk of mortality from this parasite in marine coastal waterways via sewage systems, storm water drainage, and freshwater runoff.

Toxoplasma gondii Infection in Marine Animal Species, as a Potential Source of Food Contamination: A Systematic Review and Meta-Analysis

PURPOSE

Many marine animals are infected and susceptible to toxoplasmosis, which is considered as a potential transmission source of Toxoplasma gondii to other hosts, especially humans. The current systematic review and meta-analysis aimed to determine the prevalence of T. gondii infection among sea animal species worldwide and highlight the existing gaps.

METHODS

Data collection was systematically done through searching databases, including PubMed, Science Direct, Google Scholar, Scopus, and Web of Science from 1997 to July 2020.

RESULTS

Our search strategy resulted in the retrieval of 55 eligible studies reporting the prevalence of marine T. gondii infection. The highest prevalence belonged to mustelids (sea otter) with 54.8% (95% CI 34.21-74.57) and cetaceans (whale, dolphin, and porpoise) with 30.92% (95% CI 17.85-45.76). The microscopic agglutination test (MAT) with 41 records and indirect immunofluorescence assay (IFA) with 30 records were the most applied diagnostic techniques for T. gondii detection in marine species.

CONCLUSIONS

Our results indicated the geographic distribution and spectrum of infected marine species with T. gondii in different parts of the world. The spread of T. gondii among marine animals can affect the health of humans and other animals; in addition, it is possible that marine mammals act as sentinels of environmental contamination, especially the parasites by consuming water or prey species.

EVALUATION OF IMMUNE FUNCTION IN TWO POPULATIONS OF GREEN SEA TURTLES (CHELONIA MYDAS) IN A DEGRADED VERSUS A NONDEGRADED HABITAT

There is a strong correlation between degraded marine habitats and the prevalence of diseases such as green turtle fibropapillomatosis (GTFP) in coastal populations. In GTFP, small to large tumors grow on the turtle's soft tissues and shell, while internal nodules may also occur. The disease primarily affects juvenile green sea turtles (Chelonia mydas) that reside in nearshore waters. As a link has been shown between environmental pollution and immune suppression in a variety of animals, the objective of our research was to compare innate and adaptive immune responsiveness in green sea turtles from a severely degraded and a more pristine habitat, which differ greatly in rates of GTFP. We quantified phagocytosis by flow cytometry and performed in vitro stimulation analysis to measure activity of both the innate and adaptive immune systems in wild-caught Florida green turtles. Sea turtles from the degraded environment, both with and without visible cutaneous tumors, exhibited significantly reduced phagocytosis and stimulation indices than did those from the less polluted environment. Our results suggest that environmental factors may contribute to the development of GTFP and thus can impact the health of sea turtle populations.

Toxoplasma gondii in Australian macropods (Macropodidae) and its implication to meat consumption

Toxoplasma gondii is a worldwide occurring apicomplexan parasite. Due to its high seroprevalence in livestock as well as in game animals, T. gondii is an important food-borne pathogen and can have significant health implications for humans as well as for pets. This article describes the prevalence of T. gondii in free-ranging macropods hunted for consumption. All hunted macropod species (commercial as well as non-commercial hunt) show a positive seroprevalence for T. gondii. This seroprevalence is influenced by various factors, such as sex or habitat. Furthermore, the parasite shows a high level of genetic variability in macropods. Genetically variable strains have already caused outbreaks of toxoplasmosis in the past (Canada and the US). These were attributed to undercooked game meat like venison. Despite this risk, neither Australia nor New Zealand currently have food safety checks against foodborne pathogens. These conditions scan pose a significant health risk to the population. Especially, since cases of toxoplasmosis have already been successfully traced back to insufficiently cooked kangaroo meat in the past.

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The kangaroo hunt is an important industry in Australia.

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7 species of kangaroos and wallabies are hunted for commercial purpose (for human and pet consumption).

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Food security checks against foodborne pathogens (including T. gondii) are not a requirement of the Australia New Zealand Food Standard Code.

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The databases Medline, Web of Science, SCOPUS and Informit were used.

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6 scientific publications were reviewed in this publication.

Disseminated Toxoplasmosis in a Narrow-Ridged Finless Porpoise (Neophocaena asiaeorientalis) with Transplacental Embryonal Transmission

We describe a case of systemic toxoplasmosis in a female adult narrow-ridged finless porpoise (Neophocaena asiaeorientalis) found in May 2018 inside a gillnet set in the Ariake Sound, southern Japan. The main lesions observed were lymphoplasmacytic and focally necrotizing encephalitis, necrotizing to granulomatous adrenalitis, myocarditis, and inflammation in the intestinal wall, associated with protozoal tissue cysts and tachyzoites. Additionally, the individual had a 5.6 mm (crown-rump length) early-stage embryo in the left uterine horn, which had multifocal necrotizing lesions with intralesional tissue cysts and tachyzoites in the parenchyma. Immunohistochemistry and PCR and sequencing of the internal transcribed spacer 1 region confirmed a Toxoplasma gondii infection. Further genotyping revealed an atypical type II genotype with a type I pattern for the Apico locus. Narrow-ridged finless porpoises are an endangered coastal species already facing various anthropogenic threats. Toxoplasmosis, especially with its ability to transmit to an early-stage embryo, should be considered an emerging threat to this vulnerable species.

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.

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.

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

Zoonotic parasites of seals that are harvested for food may pose a health risk when seal meat or organ tissues of infected animals are eaten raw or undercooked. In this study, 124 tissue samples from 81 seals, comprising four species, were collected from northern and eastern Canada. Tissues from 23 ringed seals (Pusa hispida), 8 hooded seals (Cystophora cristata), 21 harp seals (Pagophilus groenlandicus), and 29 grey seals (Halichoerus grypus) were tested for parasites of the Sarcocystidae family including Toxoplasma gondii, Sarcocystis spp., and Neospora spp. using nested PCR followed by Sanger sequencing. Toxoplasma gondii DNA was present in 26% of ringed seals, 63% of hooded seals, 57% of harp seals, and 31% of grey seals. Sarcocystis sp. DNA was found in 9% of ringed seals, 13% of hooded seals, 14% of harp seals, and 4% of grey seals, while N. caninum-like DNA was present in 26% of ringed seals. While it is unclear how pinnipeds may become infected with these protozoans, horizontal transmission is most likely. However, one harp seal pup (4 days old) was PCR-positive for T. gondii, suggesting vertical transmission may also occur. Phylogenetic analysis of the 18S gene region indicates that Sarcocystis sp. in these seals belongs to a unique genotype. Furthermore, this study represents a new host report for T. gondii in harp seals, a new host and geographic report for N. caninum-like parasites in ringed seals, and four new hosts and geographic reports for Sarcocystis sp. These results demonstrate that parasites of the Sarcocystidae family are prevalent in northern and eastern Canadian seals. While the zoonotic potential of Sarcocystis sp. and the N. caninum-like parasite are unclear, consumption of raw or undercooked seal meat or organ tissues pose a risk of T. gondii infection to consumers.

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Tissues from ringed, hooded, harp and grey seals in Canada were PCR-positive for Toxoplasma, Sarcocystis and Neospora.

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Raw or undercooked seal meat may pose a risk for zoonotic transmission of T. gondii to consumers.

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The risk for zoonotic transmission of Sarcocystis sp. and the Neospora caninum-like parasite is unknown.

Molecular Epizootiology of Toxoplasma gondii and Cryptosporidium parvum in the Eastern Oyster (Crassostrea virginica) from Maine (USA)

Shellfish are known as a potential source of Toxoplasma gondii (responsible for toxoplasmosis), and Cryptosporidium parvum, which is one of the major causes of gastroenteritis in the world. Here we performed a comprehensive qPCR-based monthly survey for T. gondii and C. parvum during 2016 and 2017 in oysters (Crassostrea virginica) (n = 1440) from all six sites along the coast of Maine (USA). Pooled samples (mantle, gills, and rectum) from individual oysters were used for DNA extraction and qPCR. Our study resulted in detections of qPCR positives oysters for T. gondii and C. parvum at each of the six sites sampled (in 31% and 10% of total oysters, respectively). The prevalence of T. gondii was low in 2016, and in September 2017 several sites peaked in prevalence with 100% of the samples testing positive. The prevalence of C. parvum was very low except in one estuarine location (Jack's Point) in June 2016 (58%), and in October of 2016, when both prevalence and density of C. parvum at most of the sampling sites were among the highest values detected. Statistical analysis of environmental data did not identify clear drivers of retention, but there were some notable statistically significant patterns including current direction and nitrate along with the T. gondii prevalence. The major C. parvum retention event (in October 2016) corresponded with the month of highest dissolved oxygen measurements as well as a shift in the current direction revealed by nearby instrumentation. This study may guide future research to locate any contributing parasite reservoirs and evaluate the potential risk to human consumption.

Toxoplasma gondii in cetaceans of Brazil: a histopathological and immunohistochemical survey

Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. In cetaceans, T. gondii infection is a significant cause of morbidity and mortality. Despite the worldwide range and broad cetacean host record of T. gondii infection, there is limited information on toxoplasmosis in cetaceans from the Southern hemisphere. We investigated the occurrence of T. gondii by histopathology and immunohistochemistry in tissue samples of 185 animals comprising 20 different cetacean species from Brazil. Three out of 185 (1.6%) animals presented T. gondii-associated lesions: a captive killer whale Orcinus orca, a free-ranging common bottlenose dolphin Tursiops truncatus and a free-ranging Guiana dolphin Sotalia guianensis. The main lesions observed in these animals were necrotizing hepatitis, adrenalitis and lymphadenitis associated with protozoal cysts or extracellular tachyzoites presenting immunolabeling with anti-T. gondii antibodies. This study widens the spectrum of species and the geographic range of this agent in Brazil, and provides the first reports of T. gondii infection in a captive killer whale and in a free-ranging common bottlenose dolphin in South America.

Prevalence and molecular characterization of Toxoplasma gondii DNA in retail fresh meats in Canada

Toxoplasma gondii is a protozoan parasite which infects a wide variety of mammals and birds worldwide, including humans. Human toxoplasmosis is primarily transmitted through the ingestion of tissue cysts in raw or poorly cooked meat and organs of infected animals, or through the ingestion of oocysts in food, water or soil contaminated with cat faeces. There is a distinct paucity of information on the prevalence and molecular characteristics of T. gondii in retail meats in Canada. This study reports the presence of T. gondii DNA in 4.3% (12 of 281) of packages of fresh ground beef, chicken breasts and ground pork purchased at retail in three Canadian provinces. T. gondii prevalence was very similar among all three meat types tested, and among the provinces sampled. Genotyping of positive samples by means of PCR-RFLP and DNA sequencing demonstrated the presence of both T. gondii type II (66.7%) and type III (33.3%). These findings provide baseline data on the prevalence of T. gondii DNA in fresh meats purchased at retail in Canada and will allow for more accurate and meaningful health risk assessments for the purposes of developing food safety guidelines and policies.