Terrestrial Pathogens Research Articles

Urban estuary serves as a critical nexus for the land-sea transfer of the terrestrial pathogen Toxoplasma gondii

Terrestrial runoff is a key pathway for the transmission of the terrestrial pathogen Toxoplasma gondii from land to sea, posing a significant threat to marine ecosystems. Understanding the mechanisms by which T. gondii is transported from terrestrial to marine environment is crucial for developing effective prevention and control strategies for toxoplasmosis in marine organisms. This study investigates the transport of T. gondii through terrestrial runoff in the Sow River, a representative watershed in Weihai, China. Surface water, bottom water, and sediment samples were collected and analyzed for T. gondii DNA using PCR methods. Out of 1776 samples, the prevalence of T. gondii was found to be 8.61 % in surface water, 9.80 % in bottom water, and 16.61 % in sediment, with sediment identified as a significant reservoir. Additionally, estuarine zones showed a higher prevalence of T. gondii (16.80 %) compared to riverine areas (9.00 %). The study further revealed that seasonal climate variations, such as temperature and precipitation, had no significant impact on the distribution of T. gondii. However, there was significant spatial variability, with estuarine conditions facilitating increased pathogen transmission. These findings highlight the importance of estuaries and sediments as key conduits for T. gondii entry in marine food webs. The results provide a theoretical basis for designing infection prevention and control strategies aimed at protecting marine ecosystems.

Evolutionary and immune-activating character analyses of NLR genes in algae suggest the ancient origin of plant intracellular immune receptors.

Nucleotide-binding leucine-rich repeat (NLR) proteins are crucial intracellular immune receptors in plants, responsible for detecting invading pathogens and initiating defense responses. While previous studies on the evolution and function of NLR genes were mainly limited to land plants, the evolutionary trajectory and immune-activating character of NLR genes in algae remain less explored. In this study, genome-wide NLR gene analysis was conducted on 44 chlorophyte species across seven classes and seven charophyte species across five classes. A few but variable number of NLR genes, ranging from one to 20, were identified in five chlorophytes and three charophytes, whereas no NLR gene was identified from the remaining algal genomes. Compared with land plants, algal genomes possess fewer or usually no NLR genes, implying that the expansion of NLR genes in land plants can be attributed to their adaptation to the more complex terrestrial pathogen environments. Through phylogenetic analysis, domain composition analysis, and conserved motifs profiling of the NBS domain, we detected shared and lineage-specific features between NLR genes in algae and land plants, supporting the common origin and continuous evolution of green plant NLR genes. Immune-activation assays revealed that both TNL and RNL proteins from green algae can elicit hypersensitive responses in Nicotiana benthamiana, indicating the molecular basis for immune activation has emerged in the early evolutionary stage of different types of NLR proteins. In summary, the results from this study suggest that NLR proteins may have taken a role as intracellular immune receptors in the common ancestor of green plants.

Toxicities of Legacy and Current-Use PFAS in an Anuran: Do Larval Exposures Influence Responses to a Terrestrial Pathogen Challenge?

Legacy polyfluoroalkyl substances (PFAS) [perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA)] are being replaced by various other fluorinated compounds, such as hexafluoropropylene oxide dimer acid (GenX). These alternatives are thought to be less bioaccumulative and, therefore, less toxic than legacy PFAS. Contaminant exposures occur concurrently with exposure to natural stressors, including the fungal pathogen Batrachocytrium dendrobatidis (Bd). Despite evidence that other pollutants can increase the adverse effects of Bd on anurans, no studies have examined the interactive effects of Bd and PFAS. This study tested the growth and developmental effects of PFOS, PFOA, and GenX on gray treefrog (Hyla versicolor) tadpoles, followed by a Bd challenge after metamorphosis. Despite PFAS exposure only occurring during the larval stage, carry-over effects on growth were observed post metamorphosis. Further, PFAS interacted with Bd exposure to influence growth; Bd-exposed animals had significantly shorter SVL [snout-vent length (mm)] with significantly increased body condition, among other time-dependent effects. Our data suggest that larval exposure to PFAS can continue to impact growth in the juvenile stage after exposure has ended. Contrary to predictions, GenX affected terrestrial performance more consistently than its legacy congener, PFOA. Given the role of Bd in amphibian declines, further investigation of interactions of PFAS with Bd and other environmentally relevant pathogens is warranted.

Diversity of Nigrospora (Xylariales, Apiosporaceae) Species Identified in Korean Macroalgae Including Five Unrecorded Species

Nigrospora (Xylariales, Apiosporaceae) consists of species of terrestrial plant endophytes and pathogens. Nigrospora has also been reported in marine environments such as mangroves, sea fans, and macroalgae. However, limited research has been conducted on Nigrospora associated with macroalgae. Here, we isolated Nigrospora species from three types of algae (brown, green, and red algae) from Korean islands (Chuja, Jeju, and Ulleung) based on phylogenetic analyses of multigenetic markers: the internal transcribed spacers (ITS), beta-tubulin (BenA), and translation elongation factor 1 (TEF1-α). A total of 17 Nigrospora strains were isolated from macroalgae and identified as nine distinct species. The majority of Nigrospora species (seven) were found on brown algae, followed by red algae (three), and then green algae (two). To our understanding, this study represents the first account of N. cooperae, N. covidalis, N. guilinensis, N. lacticolonia, N. osmanthi, N. pyriformis, and N. rubi occurring in marine environments. Additionally, this study provides the first report of the occurrence of N. cooperae, N. covidalis, N. guilinensis, N. lacticolonia, and N. osmanthi in South Korea. This study will provide valuable insights for future research exploring the functions of fungi in macroalgal communities.

Current trends and advances of Quorum sensing inhibitors and their biotechnological applications

Serious setbacks were witnessed in shrimp farming, the food industry, and the ship industry during the past three decades primarily due to bacterial pathogens that coordinate by quorum sensing (QS). The influence of bacterial pathogens utilizing QS. The impact of QS cell communication on public health is extremely disastrous in terms of spread, spectrum, apart from their economic impact. The overuse of antibiotics has increased drastically to battle bacterial infections, including tons of antibiotics are distributed in the biosphere. Due to the indiscriminate use of antibiotics, multiple antibiotic-resistant strains have emerged, as the antibiotic resistance genes are being transferred to bacteria of terrestrial animals, humans, and pathogens. The increased public awareness of the negative drawbacks caused by over-exposure to antibiotics, also the emergence of multiple antibiotic resistant pathogenic stains led to the search for alternatives and unique solutions. One such unconventional, promising method is the interruption of bacterial cell to cell communication, which is currently termed QS inhibition. Now-a-days, QS inhibition is the potential objective for antimicrobial chemotherapy. This review summarizes the regulatory factors that attenuate the QS activities of deadly pathogens and discusses their distinctive characteristics. Improving awareness of the natural roles of regulatory elements might be useful in unveiling inhibitor applications to understand how QS is inhibited in pathogenic bacteria by different QS inhibitors.

Dolphins and sea turtles may host zoonotic parasites and pathogenic bacteria as indicators of anthropic pressure in the Gulf of Taranto (Northern Ionian Sea, Central-Eastern Mediterranean Sea)

The occurrence of protozoan parasites Giardia duodenalis and Cryptosporidium spp. such as the pathogenic bacteria Salmonella spp. and Escherichia coli was molecularly investigated in the following free ranging species of striped dolphins (Stenella coeruleoalba), Risso’s dolphins (Grampus griseus) as well as loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtles living in the Gulf of Taranto (Mediterranean Sea). Out of forty-one investigated individuals belonging to the 4 species, 13 (31.7%) were positive to one or more pathogens and zoonotic G. duodenalis assemblage A, Cryptosporidium parvum and S. enterica were identified in striped dolphins, loggerhead and green sea turtles. In this work, the presence of these opportunistic pathogens has been investigated in fecal samples of free ranging dolphin and sea turtle species for the first time. Moreover, this is the first record of C. parvum in loggerhead sea turtles. These results may provide baseline data for the potential role of cetaceans and sea turtles as potential sentinel species for zoonotic and terrestrial pathogens in the marine environment.

Sarcocystis neurona Transmission from Opossums to Marine Mammals in the Pacific Northwest

Increasing reports of marine mammal deaths have been attributed to the parasite Sarcocystis neurona. Infected opossums, the only known definitive hosts, shed S. neurona sporocysts in their feces. Sporocysts can contaminate the marine environment via overland runoff, and subsequent ingestion by marine mammals can lead to fatal encephalitis. Our aim was to determine the prevalence of S. neurona in opossums from coastal areas of Washington State (USA) and to compare genetic markers between S. neurona in opossums and marine mammals. Thirty-two road-kill opossums and tissue samples from 30 stranded marine mammals meeting inclusion criteria were included in analyses. Three opossums (9.4%) and twelve marine mammals (40%) were confirmed positive for S. neurona via DNA amplification at the ITS1 locus. Genetic identity at microsatellites (sn3, sn7, sn9) and the snSAG3 gene of S. neurona was demonstrated among one harbor porpoise and two opossums. Watershed mapping further demonstrated plausible sporocyst transport pathways from one of these opossums to the location where an infected harbor porpoise carcass was recovered. Our results provide the first reported link between S. neurona genotypes on land and sea in the Pacific Northwest, and further demonstrate how terrestrial pathogen pollution can impact the health of marine wildlife.

Prevalence, genotypes and risk factors for Toxoplasma gondii contamination in marine bivalve shellfish in offshore waters in eastern China

We conducted a large-scale epidemiological investigation to detect the prevalence of Toxoplasma gondii in four marine bivalve shellfish species collected from six representative coastal regions of Weihai, eastern China. Between January 2018 and December 2018, 14,535 marine bivalve shellfish pooled into 2907 samples were randomly collected and examined for T. gondii DNA by a nested PCR assay targeting B1 gene. The results showed that 2.8% (82) of the 2907 pooled samples were tested positive for T. gondii DNA. Two T. gondii genotype (ToxoDB Genotype #9 and ToxoDB Genotype #1) were identified PCR-restriction fragment length polymorphism analysis. Factors that were found significantly associated with the presence of T. gondii DNA in marine bivalve shellfish included the source of samples (being wild) (odds ratio [OR], 3.34; 95% confidence interval [CI], 2.00–5.84; p < 0.01), surface runoff near the sampling site (OR, 2.64; 95% CI, 1.47–4.72; p < 0.01), and presence of cats near the sampling site (OR, 1.77; 95% CI, 1.02–3.07; p = 0.04). Moreover, the prevalence of T. gondii DNA in marine bivalve shellfish correlated with temperature (Pearson’s correlation: R = 0.75, p = 0.0049) and precipitation (R = 0.87, p = 0.00021). These findings provide new insights into the presence of T. gondii DNA in marine bivalve shellfish and highlight the impact of human activity on marine pollution by such an important terrestrial pathogen pollutant.

Molecular prevalence, risk factors and genotypes of Toxoplasma gondii DNA in wild marine snails collected from offshore waters in eastern China

Increasing evidence exisits for the role that shellfish play in the epidemiology of Toxoplasma gondii in marine environment. However, limited information is available on the level of T. gondii infection in wild marine snails, which can play a role in the transmission of T. gondii to other marine organisms and humans. In this study, the prevalence of T. gondii DNA in wild marine snails collected from three coastal cities in China was determined. Between January 2018 and November 2019, 1,206 wild marine snails were randomly collected and examined for the presence of T. gondii DNA using a nested polymerase chain reaction (PCR) targeting T. gondii B1 gene. The amplified products were genotyped using multilocus PCR-restriction fragment length polymorphism analysis. We also examined whether species of snail, sampling region, sampling season, surface runoff near samplic site, residential water discharge near samplic site, and proximity to livestock farms are associated with the occurrence of T. gondii DNA in marine snails. Our results showed that 23 (1.91%) snails were positive for T. gondii B1 gene. The genotype of two of the 23 T. gondii amplicons was consistent with ToxoDB Genotype #9. Multiple logistic regression revealed that surface runoff near the sampling site (P = 0.039, odds ratio [OR] = 3.413, 95% confidence interval [CI]: 1.07-10.94) and residential water discharge near the sampling site (P = 0.021, OR = 3.990, 95%CI: 1.24-12.87) are more likely to be associated with the presence of T. gondii DNA in marine snails. The detection of T. gondii DNA in marine snails in China highlights the potential impact of the anthropogenic activities on marine organisms and the potential foodborne risk posed to humans with such an important terrestrial pathogen.

Serum antibodies against Toxoplasma gondii and Neospora caninum in southeast Queensland dugongs

AbstractThe dugong (Dugong dugon) is an herbivorous marine mammal that inhabits tropical inshore waters and thus may be vulnerable to pollutants and terrestrial pathogens as a result of coastal runoff. In this study, serum samples collected from live, wild dugongs (n = 114) in an embayment located on the urbanized southeast Queensland coast of Australia during 2008–2014, were measured for IgG antibody levels specific to Toxoplasma gondii and Neospora caninum. An ELISA used to measure T. gondii tachyzoite antibodies indicated a non‐Gaussian distribution of antibody level, with five dugongs identified as high outliers. Mean levels of antibodies specific for T. gondii in dugongs sampled in 2014 were significantly higher than in 2010 (p = .006) and 2011 (p = .009) with an elevation in mean antibody levels after a major 2011 flood event relative to antibody levels prior to the flood (p &lt; .0001). A competitive ELISA to detect N. caninum antibody indicated a normal distribution of antibody with no high outliers. Mean antibody level for N. caninum was highest in 2012 and declined significantly in 2014 (p = .004). This is the first survey of antibodies directed against T. gondii and N. caninum in dugongs and suggests future health monitoring of this species.

First report of Salmonella 1,4,[5],12:i:- in free-ranging striped dolphins (Stenella coeruleoalba), Italy

Between 2015 and the beginning of 2018 (January-March), 30 cetaceans were found stranded along the Ligurian Sea coast of Italy. Necropsies were performed in 22 cases and infectious diseases resulted the most common cause of death. Three striped dolphins, showed a severe coinfection involving the monophasic variant of Salmonella Typhimurium (Salmonella 1,4,[5],12:i:-). The isolates were characterized based on antimicrobial resistance, Multiple-Locus Variable-number tandem-repeat Analysis (MLVA) and whole-genome sequencing (WGS). All isolates demonstrated the same multidrug resistant genotype (ASSuT isolates), showed three different MLVA profiles, two of which closely related, and were identified as Sequence Type 34. Moreover, Single nucleotide polymorphisms (SNP) analysis confirmed strong correlations between two out of the three isolates. To our knowledge, S. 1,4,[5],12:i:-, one of the most common serovars in cases of human infection and food sources worldwide, has not previously been described in marine mammals, and reports of Salmonella-associated disease in free-ranging cetaceans are rare. These results highlight the role of cetaceans as sentinel species for zoonotic and terrestrial pathogens in the marine environment, suggest a potential risk for cetaceans and public health along the North Western Italian coastline and indicate cetaceans as a novel potential reservoir for one of the most widespread Salmonella serovars.

U32 collagenase from Pseudoalteromonas agarivorans NW4327: Activity, structure, substrate interactions and molecular dynamics simulations

A protease of the primary pathogen (Pseudoalteromonas agarivorans NW4327) of the disease affecting the Great Barrier Reef sponge Rhopaloeides odorabile was purified. Zymography demonstrated calcium-dependent collagenase and gelatinase activity of the purified protein. This metalloprotease was identified by matrix assisted laser desorption ionization time-of-flight mass spectrophotometry as a 52,509 Da U32 collagenase. Predicted tertiary structure of U32 collagenase (by Phyre2 fold recognition server) demonstrated 13% identity with known hydrolases establishing novelty of the enzyme. Molecular docking conceived two interacting loops of the collagenase that bound with collagen triple helices and two calcium ions remained centered between the loops. According to ConSurf multiple sequence alignment, the residues of loop1 of the collagenase were mostly conserved while variations among residues of loop2 were comparatively higher than loop1. Asp262, Glu263 of loop1 and Thr363, Lys364, Gln365 of loop2 participated in the interaction with Ca2+ and collagen. Root mean square deviation and root mean square fluctuation values signified higher stability of the collagen-Ca2+-collagenase complex and greater structural stability of the residues of the loops in the complex compared to apocollagenase. Observed properties of NW4327 U32 collagenase and its interaction with collagen were different from similar enzymes of thermophilic bacteria and terrestrial pathogens.

The biology of fog: results from coastal Maine and Namib Desert reveal common drivers of fog microbial composition

Fog supplies water and nutrients to systems ranging from coastal forests to inland deserts. Fog droplets can also contain bacterial and fungal aerosols, but our understanding of fog biology is limited. Using metagenomic tools and culturing, we provide a unique look at fungal and bacterial communities in fog at two fog-dominated sites: coastal Maine (USA) and the Namib Desert (Namibia). Microbial communities in the fog at both sites were diverse, distinct from clear aerosols, and influenced by both soil and marine sources. Fog from both sites contained Actinobacteria and Firmicutes, commonly soil- and air-associated phyla, but also contained bacterial taxa associated with marine environments including Cyanobacteria, Oceanospirillales, Novosphingobium, Pseudoalteromonas, and Bradyrhizobiaceae. Marine influence on fog communities was greatest near the coast, but still evident in Namib fogs 50 km inland. In both systems, differences between pre- and post-fog aerosol communities suggest that fog events can significantly alter microbial aerosol diversity and composition. Fog is likely to enhance viability of transported microbes and facilitate their deposition, making fog biology ecologically important in fog-dominated environments. Fog may introduce novel species to terrestrial ecosystems, including human and plant pathogens, warranting further work on the drivers of this important and underrecognized aerobiological transfer between marine and terrestrial systems.

Mudskippers and Their Genetic Adaptations to an Amphibious Lifestyle.

Simple SummaryMudskippers are an interesting group of goggle-eyed amphibious fish that can live both in water and on land. They are a useful model for obtaining insights into the genetic mechanisms underlying the terrestrial adaptations of amphibious fish. This review summarizes the morphological and physiological modifications of representative mudskippers, and focuses on the recent advancement of genomic studies on their genetic adaptations to the amphibious lifestyle.Mudskippers are the largest group of amphibious teleost fish that are uniquely adapted to live on mudflats. During their successful transition from aqueous life to terrestrial living, these fish have evolved morphological and physiological modifications of aerial vision and olfaction, higher ammonia tolerance, aerial respiration, improved immunological defense against terrestrial pathogens, and terrestrial locomotion using protruded pectoral fins. Comparative genomic and transcriptomic data have been accumulated and analyzed for understanding molecular mechanisms of the terrestrial adaptations. Our current review provides a general introduction to mudskippers and recent research advances of their genetic adaptations to the amphibious lifestyle, which will be helpful for understanding the evolutionary transition of vertebrates from water to land. Our insights into the genomes and transcriptomes will also support molecular breeding, functional identification, and natural compound screening.

Antimicrobial Drug Resistance in Fish Pathogens.

Major concerns surround the use of antimicrobial agents in farm-raised fish, including the potential impacts these uses may have on the development of antimicrobial-resistant pathogens in fish and the aquatic environment. Currently, some antimicrobial agents commonly used in aquaculture are only partially effective against select fish pathogens due to the emergence of resistant bacteria. Although reports of ineffectiveness in aquaculture due to resistant pathogens are scarce in the literature, some have reported mass mortalities in Penaeus monodon larvae caused by Vibrio harveyi resistant to trimethoprim-sulfamethoxazole, chloramphenicol, erythromycin, and streptomycin. Genetic determinants of antimicrobial resistance have been described in aquaculture environments and are commonly found on mobile genetic elements which are recognized as the primary source of antimicrobial resistance for important fish pathogens. Indeed, resistance genes have been found on transferable plasmids and integrons in pathogenic bacterial species in the genera Aeromonas, Yersinia, Photobacterium, Edwardsiella, and Vibrio. Class 1 integrons and IncA/C plasmids have been widely identified in important fish pathogens (Aeromonas spp., Yersinia spp., Photobacterium spp., Edwardsiella spp., and Vibrio spp.) and are thought to play a major role in the transmission of antimicrobial resistance determinants in the aquatic environment. The identification of plasmids in terrestrial pathogens (Salmonella enterica serotypes, Escherichia coli, and others) which have considerable homology to plasmid backbone DNA from aquatic pathogens suggests that the plasmid profiles of fish pathogens are extremely plastic and mobile and constitute a considerable reservoir for antimicrobial resistance genes for pathogens in diverse environments.

Surveillance of laboratory exposures to human pathogens and toxins: Canada 2016.

Canada recently enacted legislation to authorize the collection of data on laboratory incidents involving a biological agent. This is done by the Public Health Agency of Canada (PHAC) as part of a comprehensive national program that protects Canadians from the health and safety risks posed by human and terrestrial animal pathogens and toxins. To describe the first year of data on laboratory exposure incidents and/or laboratory-acquired infections in Canada since the Human Pathogens and Toxins Regulations came into effect. Incidents that occurred between January 1 and December 31, 2016 were self-reported by federally-regulated parties across Canada using a standardized form from the Laboratory Incident Notification Canada (LINC) surveillance system. Exposure incidents were described by sector, frequency of occurrence, timeliness of reporting, number of affected persons, human pathogens and toxins involved, causes and corrective actions taken. Microsoft Excel 2010 was used for basic descriptive analyses. In 2016, 46 exposure incidents were reported by holders of 835 active licences in Canada representing 1,352 physical areas approved for work involving a biological agent, for an overall incidence of 3.4%. The number of incidents was highest in the academic (n=16; 34.8%) and hospital (n=12; 26.1%) sectors, while the number of reported incidents was relatively low in the private industry sector. An average of four to five incidents occurred each month; the month of September presented as an outlier with 10 incidents.​: A total of 100 people were exposed, with no reports of secondary exposure. Four incidents led to suspected (n=3) or confirmed (n=1) cases of laboratory-acquired infection. Most incidents involved pathogens classified at a risk group 2 level that were manipulated in a containment level 2 laboratory (91.3%). Over 22 different species of human pathogens and toxins were implicated, with bacteria the most frequent (34.8%), followed by viruses (26.1%). Eleven (23.9%) incidents involved a security sensitive biologic agent. Procedure breaches (n=15) and sharps-related incidents (n=14) were the most common antecedents to an exposure. In 10 (21.7%) cases, inadvertent possession (i.e., isolation of an unexpected biological agent during routine work) played a role. Possible improvements to standard operating procedures were cited in 71.7% of incidents. Improvements were also indicated for communication (26.1%) and management (23.9%). The Laboratory Incident Notification Canada is one of the first surveillance systems in the world to gather comprehensive data on laboratory incidents involving human pathogens and toxins. Exposure incidents reported in the first year were relatively rare, occurring in less than 4% of containment zones within laboratory settings.

Diversity of bacteria in ships ballast water as revealed by next generation DNA sequencing

The bacterial diversity in ballast water from five general cargo ships calling at the Port of Houston was determined with ion semiconductor DNA sequencing (Ion Torrent PGM) of PCR amplified 16S rRNA genes. Phylogenetic analysis revealed that the composition of bacteria in ballast water did not resemble that of typical marine habitats or even open ocean waters where BWEs occur. The predominant group of bacteria in ships conducting BWEs was the Roseobacter clade within the Alphaproteobacteria. In contrast, Gammaproteobacteria were predominant in the ship that did not conduct a BWE. All the ships contained human, fish, and terrestrial plant pathogens as well as bacteria indicative of fecal or activated sludge contamination. Most of the 60 pathogens had not been detected in ballast water previously. Among these were the human pathogens Corynebacterium diptheriae and several Legionella species and the fish pathogens Francisella piscicida and Piscirickettsia salmonis.

Structural characterisation of Toll-like receptor 1 (TLR1) and Toll-like receptor 6 (TLR6) in elephant and harbor seals

Pinnipeds are a diverse clade of semi-aquatic mammals, which act as key indicators of ecosystem health. Their transition from land to marine environments provides a complex microbial milieu, making them vulnerable to both aquatic and terrestrial pathogens, thereby contributing to pinniped population decline. Indeed, viral pathogens such as influenza A virus and phocine distemper virus (PDV) have been identified as the cause of several of these mass mortality events. Furthermore, bacterial infection with mammalian Brucella sp. and methicillin-resistant Staphylococcus aureus strains have also been observed in marine mammals, posing further risk to both co-habiting endangered species and public health. During these disease outbreaks, mortality rates have varied amongst different pinniped species. Analyses of innate immune receptors at the host–pathogen interface have previously identified variants which may drive these species-specific responses. Through a combination of both sequence- and structure-based methods, this study characterises members of the Toll-like receptor (TLR) 1 superfamily from both harbour and elephant seals, identifying variations which will help us to understand these species-specific innate immune responses, potentially aiding the development of specific vaccine-adjuvants for these species.

Concentration and retention of Toxoplasma gondii oocysts by marine snails demonstrate a novel mechanism for transmission of terrestrial zoonotic pathogens in coastal ecosystems.

The parasite Toxoplasma gondii is an environmentally persistent pathogen that can cause fatal disease in humans, terrestrial warm-blooded animals and aquatic mammals. Although an association between T. gondii exposure and prey specialization on marine snails was identified in threatened California sea otters, the ability of kelp-dwelling snails to transmit terrestrially derived pathogens has not been previously investigated. The objective of this study was to measure concentration and retention of T. gondii by marine snails in laboratory aquaria, and to test for natural T. gondii contamination in field-collected snails. Following exposure to T. gondii-containing seawater, oocysts were detected by microscopy in snail faeces and tissues for 10 and 3 days respectively. Nested polymerase chain reaction was also applied as a method for confirming putative T. gondii oocysts detected in snail faeces and tissues by microscopy. Toxoplasma gondii was not detected in field-collected snails. Results suggest that turban snails are competent transport hosts for T. gondii. By concentrating oocysts in faecal pellets, snails may facilitate entry of T. gondii into the nearshore marine food web. This novel mechanism also represents a general pathway by which marine transmission of terrestrially derived microorganisms can be mediated via pathogen concentration and retention by benthic invertebrates.

Les infections par Toxoplasma Gondii chez les mammifères marins échoués sur les côtes françaises et roumaines

Toxoplasma gondii infections in stranded marine mammals in France and Romania. Marine mammals are major sentinel species for the research concerning contamination of marine environment by terrestrial pathogens and are early warnings for the emergence or resurgence of infectious diseases. Protozoal parasites such as Toxoplasma gondii and Sarcocystis spp. and the helminth parasites Trichinella spp. can infect many species of marine mammals worldwide. T. gondii and Trichinella spp. zoonotic infections are a matter of concern for human health, because consumption of marine mammal meat is frequent in some regions of the world. Extensive seroprevalence investigations have been made in some parts of the world, showing a high presence of T. gondii infections in marine animals, yet little is known about it in France and Romania. This study indicates the exposure of cetaceans and pinnipeds from France and Romania to T. gondii and should be pursued by large-scale studies. This is the first report on the detection of T. gondii antibodies in cetaceans and seals in France and Romania and the first identification of T. gondii in a sperm whale.