A new pathogen transmission mechanism in the ocean: the case of sea otter exposure to the land-parasite Toxoplasma gondii

Detection of Toxoplasma gondii in wild bivalves from the Kerguelen and Galapagos archipelagos: influence of proximity to cat populations, exposure to marine currents and kelp density

Oocysts of the protozoan Toxoplasma gondii are found in felid feces and can be washed into coastal waters, where they persist for months, attaching to algae and accumulating in invertebrates. We used wild bivalves to assess contamination of coastal waters of the Kerguelen and Galapagos archipelagos by this zoonotic parasite. Additionally, we leveraged the contrasting situations of these archipelagos to identify some potential drivers of contamination. In the Galapagos, with a cat density reaching 142 per km2, 15.38% of the sampled oysters (Saccostrea palmula) tested positive for T. gondii by quantitative real-time PCR (qPCR) (n = 260), and positive samples were found in all eight sampling sites. In Kerguelen, with 1-3 cats per km2, 40.83% of 120 tested mussels (Mytilus edulis platensis) were positive, and positive samples were found in four out of the five sampling sites. These findings provide evidence of T. gondii contamination in the coastal waters of these archipelagos. Furthermore, T. gondii-positive bivalves were found on islands located 20 km away (Galapagos) and 5 km away (Kerguelen) from the nearest cat population, indicating that T. gondii oocysts can disperse through waterborne mechanisms over several kilometers from their initial deposition site. In the Galapagos, where runoff is infrequent and all sites are exposed to currents, the prevalence of qPCR-positive bivalves did not show significant variations between sites (p = 0.107). In Kerguelen where runoff is frequent and site exposure variable, the prevalence varied significantly (p < 0.001). The detection of T. gondii in Kerguelen mussels was significantly correlated with the site exposure to currents (odds ratio (OR) 60.2, p < 0.001) and the on-site density of giant kelp forests (OR 2.624, p < 0.001). This suggests that bivalves can be contaminated not only by oocysts transported by currents but also by consuming marine aggregates containing oocysts that tend to form in kelp forests.

Anti-Toxoplasma gondii IgG seroprevalence in the general population in Iran: A systematic review and meta-analysis, 2000-2023

Toxoplasmosis ranks among the most prevalent parasitic diseases globally. It seems that chronic toxoplasmosis is associated with several neuropsychiatric and other harmful effects in infected people, therefore, there is a need to investigate the prevalence of toxoplasmosis across various world regions. In this study, we conducted a meticulous meta-analysis to estimate the seroprevalence of anti-Toxoplasma gondii IgG antibodies within the general population in Iran (GPI). International and national scientific databases for studies published between January 1, 2000, and September 30, 2023, were searched. Observational studies reporting anti-T. gondii IgG seroprevalence in the GPI was selected/included. The data were synthesized using a random-effects model to calculate with a 95% confidence interval (95% CI) the national and regional anti-T. gondii IgG seroprevalence rates in Iran. Additionally, subgroup analyses were conducted to investigate the frequency of exposition to T. gondii in different socio-demographic, climatic, and geographical scenarios. From 18661 identified studies, 327 were included in the present meta-analysis, encompassing 122,882 individuals across the 31 Iranian provinces. The pooled nationwide anti-T. gondii IgG seroprevalence among the GPI was determined to be 32.9% (95% CI: 30.9-35.1%). The highest anti-T. gondii IgG seroprevalence was observed in Mazandaran province (North of Iran) (61%), whereas the lowest was in Semnan province (12.5%).Anti-T. gondii IgG seroprevalence demonstrated a higher occurrence in provinces characterized by moderate temperatures of 16-21°C, high relative humidity, and annual precipitation. Additionally, a higher anti-T. gondii IgG seroprevalence was identified among individuals with a habit of consumption of undercooked meat, raw fruits or vegetables, and untreated water. Moreover, those reporting direct contact with cats, possessing a lower level of education, residing in rural areas, being engaged in farming occupations, or playing the role of housewives exhibited higher anti-T. gondii IgG seroprevalence figures.The anti-T. gondii IgG seroprevalence within GPI closely aligns with the estimated worldwide average exposition rates. This underscores the imperative for public health policymakers to prioritize educational efforts regarding toxoplasmosis transmission pathways and its link to harmful effects.

Late Embryogenesis Abundant Proteins Contribute to the Resistance of Toxoplasma gondii Oocysts against Environmental Stresses

Toxoplasma gondii oocysts, which are shed in large quantities in the feces from infected felines, are very stable in the environment, resistant to most inactivation procedures, and highly infectious. The oocyst wall provides an important physical barrier for sporozoites contained inside oocysts, protecting them from many chemical and physical stressors, including most inactivation procedures. Furthermore, sporozoites can withstand large temperature changes, even freeze-thawing, as well as desiccation, high salinity, and other environmental insults; however, the genetic basis for this environmental resistance is unknown. Here, we show that a cluster of four genes encoding Late Embryogenesis Abundant (LEA)-related proteins are required to provide Toxoplasma sporozoites resistance to environmental stresses. Toxoplasma LEA-like genes (TgLEAs) exhibit the characteristic features of intrinsically disordered proteins, explaining some of their properties. Our in vitro biochemical experiments using recombinant TgLEA proteins show that they have cryoprotective effects on the oocyst-resident lactate dehydrogenase enzyme and that induced expression in E. coli of two of them leads to better survival after cold stress. Oocysts from a strain in which the four LEA genes were knocked out en bloc were significantly more susceptible to high salinity, freezing, and desiccation compared to wild-type oocysts. We discuss the evolutionary acquisition of LEA-like genes in Toxoplasma and other oocyst-producing apicomplexan parasites of the Sarcocystidae family and discuss how this has likely contributed to the ability of sporozoites within oocysts to survive outside the host for extended periods. Collectively, our data provide a first molecular detailed view on a mechanism that contributes to the remarkable resilience of oocysts against environmental stresses. IMPORTANCE Toxoplasma gondii oocysts are highly infectious and may survive in the environment for years. Their resistance against disinfectants and irradiation has been attributed to the oocyst and sporocyst walls by acting as physical and permeability barriers. However, the genetic basis for their resistance against stressors like changes in temperature, salinity, or humidity, is unknown. We show that a cluster of four genes encoding Toxoplasma Late Embryogenesis Abundant (TgLEA)-related proteins are important for this resistance to environmental stresses. TgLEAs have features of intrinsically disordered proteins, explaining some of their properties. Recombinant TgLEA proteins show cryoprotective effects on the parasite's lactate dehydrogenase, an abundant enzyme in oocysts, and expression in E. coli of two TgLEAs has a beneficial effect on growth after cold stress. Moreover, oocysts from a strain lacking all four TgLEA genes were more susceptible to high salinity, freezing, and desiccation compared to wild-type oocysts, highlighting the importance of the four TgLEAs for oocyst resilience.

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.

Research on demographic, clinical and paraclinical aspects in pregnant women infected with Toxoplasma gondii

Toxoplasmosis is a zoonotic disease caused by the Toxoplasma gondii protozoan parasite. The aim of this study was to determine the frequency of acute toxoplasmosis or its presence in the medical history of 240 pregnant women, depending on age and geographical background. The second purpose was to analyze several medical aspects (clinical and paraclinical) in pregnant women with acute toxoplasmosis. The study identified several serological changes including positive toxoplasma IgM, IgG, and IgA antibodies. The chemiluminescence immunoassay (CLIA) method was used to detect T. gondii-specific IgM and IgG antibodies and the enzyme immunoassay (EIA) method to detect T. gondii-specific IgA antibodies. Of the 96 pregnant women (40%) infected with T. gondii, approximately 1/3 had acquired acute infection and 2/3 had a history of prior acute infection (P<0.0001). No statistically significant differences according to age groups (P=0.9384) were found in terms of serological profile. The number of patients with negative serology was significantly higher in urban areas than in rural areas (P<0.0001). The highest incidence among the pregnant women with acute toxoplasmosis with a single chain of ganglia affected was represented by those with the involvement of cervical lymph nodes (75%), the difference compared to the involvement of other chains of ganglia being statistically significant (P=0.0087). All 35 pregnant women with acute toxoplasmosis tested positive for T. gondii-specific IgM antibodies. Most pregnant women with acute T. gondii infection (57.1%) tested negative for T. gondii-specific IgM antibody serum titres within 3-6 months of presentation. The difference compared to other intervals from the moment pregnant women sought care was statistically significant (P=00002). Only 80% of all pregnant women with acute toxoplasmosis tested positive for T. gondii-specific IgA antibodies. Pregnant women with acute toxoplasmosis have a 3.3 times higher risk of pregnancy loss.

Seroprevalence of Toxoplasma gondii infection from water buffaloes (Bubalus bubalis) in northeastern and southern Thailand

Toxoplasmosis is a parasitic disease resulting from infection with the apicomplexan Toxoplasma gondii (Nicolle et Manceaux, 1908), one of the world's most common parasites in warm-blooded animals, including humans. Sources of infection can be exposed to infected cat faeces, mother-to-child transmission during pregnancy, and notably, the consumption of undercooked contaminated meat of intermediate hosts. In Thailand, water buffaloes are highly valued for rice cultivation, traditional culture and meat production. Like several other mammalian species, these animals play a role as reservoirs of T. gondii, thus representing a threat to human health. The seroprevalence of T. gondii infection in swamp buffaloes was examined in southern and northeastern Thailand. In total, serum samples of 721 water buffaloes were collected from seven provinces (Ubon Ratchathani, Roi Et, Si Sa Ket, Surin, Buri Ram, Sakon Nakhon, and Songkhla) and examined for the presence of T. gondii infection using commercial latex agglutination test kits (TOXOCHECK-MT, Eiken Chemical Co., Tokyo, Japan). Of the 721 animals analysed, 49 (6.8%) were positive for T. gondii. Songkhla province had the highest seroprevalence (14.7%) among the seven provinces covered in this survey. There was a potential risk to local citizens of T. gondii infection identified by the present study, notably in northeastern Thailand, where despite lower seroprevalence consuming raw buffalo meat salad should be restricted to avoid the risk of zoonotic infections.

Exposure of pelagic seabirds to Toxoplasma gondii in the Western Indian Ocean points to an open sea dispersal of this terrestrial parasite

Toxoplasma gondii is a protozoan parasite that uses felids as definitive hosts and warm-blooded animals as intermediate hosts. While the dispersal of T. gondii infectious oocysts from land to coastal waters has been well documented, transmission routes to pelagic species remain puzzling. We used the modified agglutination test (MAT titre ≥ 10) to detect antibodies against T. gondii in sera collected from 1014 pelagic seabirds belonging to 10 species. Sampling was carried out on eight islands of the Western Indian Ocean: Reunion and Juan de Nova (colonized by cats), Cousin, Cousine, Aride, Bird, Europa and Tromelin islands (cat-free). Antibodies against T. gondii were found in all islands and all species but the great frigatebird. The overall seroprevalence was 16.8% [95% CI: 14.5%-19.1%] but significantly varied according to species, islands and age-classes. The low antibody levels (MAT titres = 10 or 25) detected in one shearwater and three red-footed booby chicks most likely resulted from maternal antibody transfer. In adults, exposure to soils contaminated by locally deposited oocysts may explain the detection of antibodies in both wedge-tailed shearwaters on Reunion Island and sooty terns on Juan de Nova. However, 144 adults breeding on cat-free islands also tested positive. In the Seychelles, there was a significant decrease in T. gondii prevalence associated with greater distances to cat populations for species that sometimes rest on the shore, i.e. terns and noddies. This suggests that oocysts carried by marine currents could be deposited on shore tens of kilometres from their initial deposition point and that the number of deposited oocysts decreases with distance from the nearest cat population. The consumption of fishes from the families Mullidae, Carangidae, Clupeidae and Engraulidae, previously described as T. gondii oocyst-carriers (i.e. paratenic hosts), could also explain the exposure of terns, noddies, boobies and tropicbirds to T. gondii. Our detection of antibodies against T. gondii in seabirds that fish in the high sea, have no contact with locally contaminated soils but frequent the shores and/or consume paratenic hosts supports the hypothesis of an open-sea dispersal of T. gondii oocysts by oceanic currents and/or fish.

Competency of common northern sea otter (Enhydra lutris kenyoni) prey items to harbor Streptococcus lutetiensis and S. phocae

Streptococcus lutetiensis and S. phocae have been associated with significant morbidity and mortality in northern sea otters Enhydra lutris kenyoni in Alaska, USA, but the route and mechanism(s) of transmission remain unknown. The goal of this study was to determine the competence of common northern sea otter prey to harbor 2 species of pathogenic Streptococcus bacteria. Prey items (bay mussels Mytilus trossulus, butter clams Saxidomus giganteus, Dungeness crab Metacarcinus magister and black turban snails Tegula funebralis) were exposed to known concentrations of exponential phase cultures of S. lutetiensis and S. phocae in seawater for 24 h. A quantitative PCR assay was developed targeting the sodA gene of both S. lutetiensis and S. phocae to quantify DNA in the prey samples. Results (mean ± SD) revealed that butter clams had the highest concentration of bacteria (4.32 × 107 ± 8.20 × 106 CFU ml-1 of S. lutetiensis, 1.20 × 108 ± 2.08 × 107 CFU ml-1 of S. phocae), followed by mussels (4.26 × 107 ± 1.66 × 107 CFU ml-1, 1.16 × 108 ± 5.39 × 107 CFU ml-1), snails (1.90 × 107 ± 5.26 × 106 CFU ml-1, 5.97 × 107 ± 2.07 × 107 CFU ml-1) and crab (1.46 × 107 ± 0 CFU ml-1, 1.64 × 107 ± 0 CFU ml-1). All prey species harbored higher concentrations of S. phocae than S. lutetiensis.

Bioaccumulation of Pathogen Exposure in Top Predators

Predator-prey interactions present heightened opportunities for pathogen spillover, as predators are at risk of exposure to infectious agents harbored by prey. Epizootics with high morbidity and mortality have been recorded following prey-to-predator spillover events, which have had significant conservation implications for sensitive species. Using felids as a detailed case study, we have documented both virulent and clinically silent infections in apex predators following transfer of microbes from prey. We draw on these examples and others to examine the mechanisms that determine frequency and outcome of predator exposure to prey-based pathogens. We propose that predator-prey dynamics should be more thoroughly considered in empirical research and disease dynamic modeling approaches in order to reveal answers to outstanding questions relating to pathogen bioaccumulation.

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.

Parasite Load and STRs Genotyping of Toxoplasma gondii Isolates From Mediterranean Mussels (Mytilus galloprovincialis) in Southern Italy

Toxoplasmosis is a zoonotic food-borne disease caused by Toxoplasma gondii, a land-derived protozoan parasite that infects a broad range of terrestrial and aquatic hosts. T. gondii may reach coastal waters via contaminated freshwater runoff and its oocysts may enter into the marine food web. Marine invertebrates as mussels being filter feeders are exposed and may concentrate T. gondii oocysts representing a potential source of infection for animals and humans. The present works investigated the prevalence, parasite burden and genotypes of T. gondii in the Mediterranean mussels (Mytilus galloprovincialis) from southern Italy. We sampled a total of 382 individual Mediterranean mussels from May to August 2018 from seven production sites in the Gulf of Naples (Campania region). An additional sample including 27 farmed Mediterranean mussels was obtained in February 2018 from a mollusk depuration plant in Corigliano Calabro (Calabria region). T. gondii DNA was detected in 43 out of 409 (10.5%) Mediterranean mussels from seven out of eight sampling sites. The number of T. gondii copies/g in the digestive gland ranged from 0.14 to 1.18. Fragment analysis of Short Tandem Repeats (STRs) at 5 microsatellite loci was performed from 10 T. gondii PCR positive samples revealing the presence of five distinct genotypes including one corresponding to type I and four atypical genotypes. These findings suggest potential implications of epidemiological importance for human and animal health because both type I and atypical genotypes could be highly pathogenic.

Spatial epidemiological patterns suggest mechanisms of land-sea transmission for Sarcocystis neurona in a coastal marine mammal

Sarcocystis neurona was recognised as an important cause of mortality in southern sea otters (Enhydra lutris nereis) after an outbreak in April 2004 and has since been detected in many marine mammal species in the Northeast Pacific Ocean. Risk of S. neurona exposure in sea otters is associated with consumption of clams and soft-sediment prey and is temporally associated with runoff events. We examined the spatial distribution of S. neurona exposure risk based on serum antibody testing and assessed risk factors for exposure in animals from California, Washington, British Columbia and Alaska. Significant spatial clustering of seropositive animals was observed in California and Washington, compared with British Columbia and Alaska. Adult males were at greatest risk for exposure to S. neurona, and there were strong associations with terrestrial features (wetlands, cropland, high human housing-unit density). In California, habitats containing soft sediment exhibited greater risk than hard substrate or kelp beds. Consuming a diet rich in clams was also associated with increased exposure risk. These findings suggest a transmission pathway analogous to that described for Toxoplasma gondii, with infectious stages traveling in freshwater runoff and being concentrated in particular locations by marine habitat features, ocean physical processes, and invertebrate bioconcentration.

Structure, composition, and roles of the Toxoplasma gondii oocyst and sporocyst walls

Toxoplasma gondii is a coccidian parasite with the cat as its definitive host but any warm-blooded animal, including humans, may act as intermediate hosts. It has a worldwide distribution where it may cause acute and chronic toxoplasmosis. Infection can result from ingestion either of tissue cysts in infected meat of intermediate hosts or oocysts found in cat faeces via contaminated water or food. In this review, we highlight how the oocyst and sporocyst walls sustain the persistence and transmission of infective T. gondii parasites from terrestrial and aquatic environments to the host. We further discuss why targeting the oocyst wall structure and molecules may reduce the burden of foodborne and waterborne T. gondii infections.

Anti-Toxoplasma activity of Sorghum bicolor-derived lipophilic fractions

Objective

Toxoplasma gondii, an intracellular zoonotic parasite, infects approximately a third of the world population. Current drugs for treatment of T. gondii infection have been challenged with ineffectiveness and adverse side effects. This necessitates development of new anti-Toxoplasma drugs. Sorghum bicolor [Moench] leaf extract has been used in African traditional medicine for the management of anemia and treatment of infectious diseases. We tested the in vitro anti-Toxoplasma inhibitory activity of S. bicolor’s oil-like crude extracts and fractions against T. gondii and determined their cytotoxic effects on human host cells.

Results

Significant inhibitory activities against the growth of T. gondii tachyzoites were observed for the crude extract (IC₅₀ = 3.65 µg/mL), the hexane-methanol fraction (IC₅₀ = 2.74 µg/mL), and the hexane fraction (IC50 = 3.55 µg/mL) after 48 h of culture. The minimum cytotoxicity concentrations against HFF were 34.41, 16.92 and 7.23 µg/mL for crude extract, hexane-methanol and hexane fractions, respectively. The crude extract and fractions showed high antiparasitic effects with low cytotoxic effects. Further studies to determine synergistic activities and modes of action would provide impetus for the development of new toxoplasmosis drugs or nutraceuticals.

Toxoplasma gondii in edible fishes captured in the Mediterranean basin

The issue of whether market fish can be involved in the transmission of Toxoplasma gondii in the marine environment is highly debated since toxoplasmosis has been diagnosed frequently in cetaceans stranded along the Mediterranean coastlines in recent times. To support the hypothesis that fishes can harbour and effectively transmit the parasite to top-of-the-food-chain marine organisms and to human consumers of fishery products, a total of 1,293 fishes from 17 species obtained from wholesale and local fish markets were examined for T. gondii DNA. Real-time PCR was performed in samples obtained by separately pooling intestines, gills and skin/muscles collected from each fish species. Thirty-two out of 147 pooled samples from 12 different fish species were found contaminated with T. gondii DNA that was detected in 16 samples of skin/muscle and in 11 samples of both intestine and gills. Quantitative analysis of amplified DNA performed by both real-time PCR and digital PCR (dPCR) confirmed that positive fish samples were contaminated with Toxoplasma genomic DNA to an extent of 6.10 × 10^-2 to 2.77 × 10⁴  copies/ml (quantitative PCR) and of 1 to 5.7 × 10⁴  copies/ml (dPCR). Fishes are not considered competent biological hosts for T. gondii; nonetheless, they can be contaminated with T. gondii oocysts flowing via freshwater run-offs (untreated sewage discharges, soil flooding) into the marine environment, thus acting as mechanical carriers. Although the detection of viable and infective T. gondii oocysts was not the objective of this investigation, the results here reported suggest that fish species sold for human consumption can be accidentally involved in the transmission route of the parasite in the marine environment and that the risk of foodborne transmission of toxoplasmosis to fish consumers should be further investigated.

Investigating seagrass in Toxoplasma gondii transmission in Florida (Trichechus manatus latirostris) and Antillean (T. m. manatus) manatees

Toxoplasma gondii is a feline protozoan reported to cause morbidity and mortality in manatees and other marine mammals. Given the herbivorous nature of manatees, ingestion of oocysts from contaminated water or seagrass is presumed to be their primary mode of infection. The objectives of this study were to investigate oocyst contamination of seagrass beds in Puerto Rico and determine the seroprevalence of T. gondii in Antillean (Trichechus manatus manatus) and Florida (T. m. latirostris) manatees. Sera or plasma from Antillean (n = 5) and Florida (n = 351) manatees were tested for T. gondii antibodies using the modified agglutination test. No T. gondii DNA was detected via PCR in seagrass samples (n = 33) collected from Puerto Rico. Seroprevalence was 0%, suggesting a lower prevalence of T. gondii in these manatee populations than previously reported. This was the first study to investigate the potential oocyst contamination of the manatee diet, and similar studies are important for understanding the epidemiology of T. gondii in herbivorous marine mammals.

A novel dense granule protein, GRA41, regulates timing of egress and calcium sensitivity in Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular apicomplexan parasite with high seroprevalence in humans. Repeated lytic cycles of invasion, replication, and egress drive both the propagation and the virulence of this parasite. Key steps in this cycle, including invasion and egress, depend on tightly regulated calcium fluxes and, although many of the calcium-dependent effectors have been identified, the factors that detect and regulate the calcium fluxes are mostly unknown. To address this knowledge gap, we used a forward genetic approach to isolate mutants resistant to extracellular exposure to the calcium ionophore A23187. Through whole genome sequencing and complementation, we have determined that a nonsense mutation in a previously uncharacterised protein is responsible for the ionophore resistance of one of the mutants. The complete loss of this protein recapitulates the resistance phenotype and importantly shows defects in calcium regulation and in the timing of egress. The affected protein, GRA41, localises to the dense granules and is secreted into the parasitophorous vacuole where it associates with the tubulovesicular network. Our findings support a connection between the tubulovesicular network and ion homeostasis within the parasite, and thus a novel role for the vacuole of this important pathogen.

Novel urease-negative Helicobacter sp. 'H. enhydrae sp. nov.' isolated from inflamed gastric tissue of southern sea otters

A total of 31 sea otters Enhydra lutris nereis found dead or moribund (and then euthanized) were necropsied in California, USA. Stomach biopsies were collected and transected with equal portions frozen or placed in formalin and analyzed histologically and screened for Helicobacter spp. in gastric tissue. Helicobacter spp. were isolated from 9 sea otters (29%); 58% (18 of 31) animals were positive for helicobacter by PCR. The Helicobacter sp. was catalase- and oxidase-positive and urease-negative. By electron microscopy, the Helicobacter sp. had lateral and polar sheathed flagella and had a slightly curved rod morphology. 16S and 23S rRNA sequence analyses of all 'H. enhydrae' isolates had similar sequences, which clustered as a novel Helicobacter sp. closely related to H. mustelae (96-97%). The genome sequence of isolate MIT 01-6242 was assembled into a single ~1.6 Mb long contig with a 40.8% G+C content. The annotated genome contained 1699 protein-coding sequences and 43 RNAs, including 65 genes homologous to known Helicobacter spp. and Campylobacter spp. virulence factors. Histological changes in the gastric tissues extended from mild cystic degeneration of gastric glands to severe mucosal erosions and ulcers. Silver stains of infected tissues demonstrated slightly curved bacterial rods at the periphery of the gastric ulcers and on the epithelial surface of glands. The underlying mucosa and submucosa were infiltrated by low numbers of neutrophils, macrophages, and lymphocytes, with occasional lymphoid aggregates and well-defined lymphoid follicles. This is the second novel Helicobacter sp., which we have named 'H. enhydrae', isolated from inflamed stomachs of mustelids, the first being H. mustelae from a ferret.

Role of vertical transmission of Toxoplasma gondii in prevalence of infection

The parasite, Toxoplasma gondii, is a highly successful pathogen that infects around 30% of the global human population. Additionally, it is able to infect all warm blooded animals with high prevalence. This is surprising as it is a parasite of the cat and can only complete its full sexual cycle in that host. This review examines the important key routes of transmission: infective oocysts from the cat, ingestion of raw infected tissue and vertical transmission. The latter route of transmission has traditionally been thought to be rare. In this review, this assumption is examined and discussed in the light of the current literature. The available evidence points to the possibility that vertical transmission occurs frequently in natural populations of mice however the evidence in sheep is currently ambivalent and controversial. In humans, the situation appears as though vertical transmission may be rare although there is still much that is unexplained.

Concentration and retention of Toxoplasma gondii surrogates from seawater by red abalone (Haliotis rufescens)

Small marine snails and abalone have been identified as high- and low-risk prey items, respectively, for exposure of threatened southern sea otters to Toxoplasma gondii, a zoonotic parasite that can cause fatal encephalitis in animals and humans. While recent work has characterized snails as paratenic hosts for T. gondii, the ability of abalone to vector the parasite has not been evaluated. To further elucidate why abalone predation may be protective against T. gondii exposure, this study aimed to determine whether: (1) abalone are physiologically capable of acquiring T. gondii; and (2) abalone and snails differ in their ability to concentrate and retain the parasite. Abalone were exposed to T. gondii surrogate microspheres for 24 h, and fecal samples were examined for 2 weeks following exposure. Concentration of surrogates was 2-3 orders of magnitude greater in abalone feces than in the spiked seawater, and excretion of surrogates continued for 14 days post-exposure. These results indicate that, physiologically, abalone and snails can equally vector T. gondii as paratenic hosts. Reduced risk of T. gondii infection in abalone-specializing otters may therefore result from abalone's high nutritional value, which implies otters must consume fewer animals to meet their caloric needs.

Sentinel Animals in a One Health Approach to Harmful Cyanobacterial and Algal Blooms

People, domestic animals, and wildlife are all exposed to numerous environmental threats, including harmful algal blooms (HABs). However, because animals exhibit wide variations in diet, land use and biology, they are often more frequently or heavily exposed to HAB toxins than are people occupying the same habitat, making them sentinels for human exposures. Historically, we have taken advantage of unique physiological characteristics of animals, such as the sensitivity of canaries to carbon monoxide, to more quickly recognize threats and help protect human health. As HAB events become more severe and widespread worldwide, exposure and health outcome data for animals can be extremely helpful to predict, prevent, and evaluate human exposures and health outcomes. Applying a One Health approach to investigation of HABs means that lessons learned from animal sentinels can be applied to protect people, animals and our shared environment.

Impact of environmental factors on the emergence, transmission and distribution of Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular protozoan that poses a great threat to human health and economic well-being worldwide. The effects of environmental factors such as changing climate and human activities on the ecology of this protozoan are being discovered. Accumulated evidence shows that changes of these environmental factors can exert influence on the occurrence, transmission and distribution of T. gondii. This article reviews studies from different geographical regions with varying climates, social cultures and animal welfare standards. It aims to illustrate how these environmental factors work, highlighting their importance in influencing the ecology of T. gondii, as well as providing clues which may contribute to preventing transmission of this important zoonotic pathogen.

Aquatic polymers can drive pathogen transmission in coastal ecosystems

Gelatinous polymers including extracellular polymeric substances (EPSs) are fundamental to biophysical processes in aquatic habitats, including mediating aggregation processes and functioning as the matrix of biofilms. Yet insight into the impact of these sticky molecules on the environmental transmission of pathogens in the ocean is limited. We used the zoonotic parasite Toxoplasma gondii as a model to evaluate polymer-mediated mechanisms that promote transmission of terrestrially derived pathogens to marine fauna and humans. We show that transparent exopolymer particles, a particulate form of EPS, enhance T. gondii association with marine aggregates, material consumed by organisms otherwise unable to access micrometre-sized particles. Adhesion to EPS biofilms on macroalgae also captures T. gondii from the water, enabling uptake of pathogens by invertebrates that feed on kelp surfaces. We demonstrate the acquisition, concentration and retention of T. gondii by kelp-grazing snails, which can transmit T. gondii to threatened California sea otters. Results highlight novel mechanisms whereby aquatic polymers facilitate incorporation of pathogens into food webs via association with particle aggregates and biofilms. Identifying the critical role of invisible polymers in transmission of pathogens in the ocean represents a fundamental advance in understanding and mitigating the health impacts of coastal habitat pollution with contaminated runoff.

Using molecular epidemiology to track Toxoplasma gondii from terrestrial carnivores to marine hosts: implications for public health and conservation

BACKGROUND

Environmental transmission of the zoonotic parasite Toxoplasma gondii, which is shed only by felids, poses risks to human and animal health in temperate and tropical ecosystems. Atypical T. gondii genotypes have been linked to severe disease in people and the threatened population of California sea otters. To investigate land-to-sea parasite transmission, we screened 373 carnivores (feral domestic cats, mountain lions, bobcats, foxes, and coyotes) for T. gondii infection and examined the distribution of genotypes in 85 infected animals sampled near the sea otter range.

METHODOLOGY/PRINCIPAL FINDINGS

Nested PCR-RFLP analyses and direct DNA sequencing at six independent polymorphic genetic loci (B1, SAG1, SAG3, GRA6, L358, and Apico) were used to characterize T. gondii strains in infected animals. Strains consistent with Type X, a novel genotype previously identified in over 70% of infected sea otters and four terrestrial wild carnivores along the California coast, were detected in all sampled species, including domestic cats. However, odds of Type X infection were 14 times higher (95% CI: 1.3-148.6) for wild felids than feral domestic cats. Type X infection was also linked to undeveloped lands (OR = 22, 95% CI: 2.3-250.7). A spatial cluster of terrestrial Type II infection (P = 0.04) was identified in developed lands bordering an area of increased risk for sea otter Type II infection. Two spatial clusters of animals infected with strains consistent with Type X (P ≤ 0.01) were detected in less developed landscapes.

CONCLUSIONS

Differences in T. gondii genotype prevalence among domestic and wild felids, as well as the spatial distribution of genotypes, suggest co-existing domestic and wild T. gondii transmission cycles that likely overlap at the interface of developed and undeveloped lands. Anthropogenic development driving contact between these cycles may increase atypical T. gondii genotypes in domestic cats and facilitate transmission of potentially more pathogenic genotypes to humans, domestic animals, and wildlife.