Isolation of Toxoplasma gondii from bottlenose dolphins (Tursiops truncatus)

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 Genetic Diversity in Mediterranean Dolphins

Toxoplasma gondii constitutes a major zoonotic agent but also has been frequently identified as an important cause of clinical disease (e.g., abortion, pneumonia, encephalitis) in wildlife; specifically, T. gondii has been associated with neurological disease in cetaceans. This study investigated the genetic diversity of T. gondii strains involved in infections in dolphins found stranded in the Mediterranean coastlines of Italy. Tissue samples from 16 dolphins (Stenella coeruleoalba and Tursiops truncatus species) positive for T. gondii-DNA presence by PCR were examined by histology and subjected to further genetic characterization of strains detected by PCR-RFLP and multilocus PCR-sequencing assays. According to fully genotyped samples, the genotypes ToxoDB#3 (67%) and #2 (22%) were detected, the latter being reported for the first time in cetaceans, along with a mixed infection (11%). Subtyping by PCR-seq procedures provided evidence of common point mutations in strains from southwestern Europe. Despite evidence of T. gondii as a cause of neurological disease in dolphins, sources of infections are difficult to identify since they are long-living animals and some species have vast migration areas with multiple chances of infection. Finally, the genetic diversity of T. gondii found in the dolphins studied in the Mediterranean coastlines of Italy reflects the main genotypes circulating inland in the European continent.

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.

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.

Evidence for Unknown Sarcocystis-Like Infection in Stranded Striped Dolphins (Stenella coeruleoalba) from the Ligurian Sea, Italy

Simple Summary

Two stranded striped dolphins presented meningoenchepalitic lesions associated with the presence of unknown protozoan tissue cysts. The present study aimed at fully characterizing these previously undescribed parasites. Light microscopy re-examination of affected CNS areas showed high numbers of tissue cysts with morphological features resembling those of Sarcocystis species. Tissue cyst bradyzoites positively stained when labeled with polyclonal antisera but cross-reactivity could not be precluded. Sarcocystis sp. sequences with high homology to species infecting livestock were amplified by means of PCR from myocardial and muscle tissues. This is the first report of Sarcocystis-like tissue cysts in the cerebral tissue of stranded cetaceans with muscular sarcocystosis in Mediterranean dolphins. The obtained results may suggest a land-to-sea cycling of Apicomplexan parasites in this region and the need for further investigations in order to foster marine mammal conservation.

Abstract

Two striped dolphins (SD1, SD2), stranded along the Ligurian coast of Italy, were diagnosed with a nonsuppurative meningoencephalitis associated with previously undescribed protozoan tissue cysts. As tissue cysts were morphologically different from those of Toxoplasma gondii, additional histopathological, immunohistochemical, ultrastructural, and biomolecular investigations were performed, aiming to fully characterize the organism. Histopathology revealed the presence of large Sarcocystis-like tissue cysts, associated with limited inflammatory lesions in all CNS areas studied. IHC was inconclusive, as positive staining with polyclonal antisera did not preclude cross-reaction with other Sarcocystidae coccidia. Applied to each animal, 11 different PCR protocols precluded a neural infection by Sarcocystis neurona, Sarcocystis falcatula, Hammondia hammondi, and Neospora caninum. T. gondii coinfection was confirmed only in dolphin SD2. Sarcocystis sp. sequences, showing the highest homology to species infecting the Bovidae family, were amplified from SD1 myocardium and SD2 skeletal muscle. The present study represents the first report of Sarcocystis-like tissue cysts in the brain of stranded cetaceans along with the first description of Sarcocystis sp. infection in muscle tissue of dolphins from the Mediterranean basin.

Dolphins Stranded along the Tuscan Coastline (Central Italy) of the "Pelagos Sanctuary": A Parasitological Investigation

Parasite monitoring is considered a necessary step for cetacean management and conservation. Between February 2013 and July 2015, 26 dolphins (15 Stenella coeruleoalba, 10 Tursiops truncatus, and one Grampus griseus) stranded along the Tuscan coastline of the protected marine area "Pelagos Sanctuary", were examined. Organs, tissues, and faecal and blood samples taken from all animals were analysed by parasitological, immunological, and molecular techniques. Twenty-one out of 26 dolphins (80.77%) tested positive for at least one parasite species, and 13/15 (86.7%) S. coeruleoalba, 7/10 (70%) T. truncatus, and the single G. griseus were found positive. Identified parasites included the nematodes Skrjabinalius guevarai (7.69%, 2/26), Halocercus lagenorhynchi (3.85%, 1/26), Halocercus delphini (7.69%, 2/26), Stenurus ovatus (7.69%, 2/26), Crassicauda spp. (7.69%, 2/26); the trematodes Pholeter gastrophilus (26.92%, 7/26), Campula palliata (3.85%, 1/26); the cestodes Phyllobothrium delphini (42.31%, 11/26), Monorygma grimaldii (23.08%, 6/26), Tetrabothrium forsteri (7.69%, 2/26), Strobilocephalus triangularis (7.69%, 2/26), and the acanthocephalan Bolbosoma vasculosum (7.69%, 2/26). Moreover, 6/26 (23%) animals scored positive to Toxoplasma gondii at serology, but PCR confirmed the infection (T. gondii Type II genotype) in a single animal. In examined dolphins, obtained results showed a high prevalence of endoparasites, which included species considered as a cause of severe debilitation or death.

Leptospira spp. and Toxoplasma gondii in stranded representatives of wild cetaceans in the Philippines

Background

The stranding events of cetaceans in the Philippines provide opportunities for gathering biological information and specimens, especially from the pelagic forms. As part of an effort to monitor the health of wild cetaceans, this study detected Leptospira spp. and Toxoplasma gondii, causative agents of the emerging zoonotic diseases leptospirosis and toxoplasmosis respectively, in their stranded representatives. From October 2016–August 2018, 40 cetaceans (representing 14 species) that stranded nationwide were sampled for brain, cardiac muscle, skeletal muscle, kidney, and blood tissues, urine, and sera. These were subjected to molecular, serological, culture, and histopathological analyses to detect the target pathogens.

Results

T. gondii was detected in 20 (71%) of the 28 cetaceans with biological samples subjected to either molecular detection through RE gene amplification or IgG antibodies detection through agglutination-based serological assay. On the other hand, Leptospira was detected in 18 (64%) of 28 cetaceans with biological samples subjected to bacterial culture, molecular detection through 16S rDNA amplification, or IgM antibodies detection through ELISA-based serological assay.

Conclusions

There is the plausibility of toxoplasmosis and leptospirosis in cetacean populations found in the Philippines, however, acute or chronic phases of infections in sampled stranded individuals cannot be confirmed in the absence of supporting pathological observations and corroborating detection tests. Further studies should look for more evidences of pathogenicity, and explore the specific mechanisms by which pelagic cetacean species become infected by Leptospira spp. and T. gondii. As there is growing evidence on the role of cetaceans as sentinels of land-sea movement of emerging pathogens and the diseases they cause, any opportunity, such as their stranding events, should be maximized to investigate the health of their populations. Moreover, the role of leptospirosis or toxoplasmosis in these stranding events must be considered.

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.

Pinniped- and Cetacean-Derived ETosis Contributes to Combating Emerging Apicomplexan Parasites (Toxoplasma gondii, Neospora caninum) Circulating in Marine Environments

Leukocytes play a major role in combating infections either by phagocytosis, release of antimicrobial granules, or extracellular trap (ET) formation. ET formation is preceded by a certain leukocyte cell death form, known as ETosis, an evolutionarily conserved mechanism of the innate immune system also observed in marine mammals. Besides several biomolecules and microbial stimuli, marine mammal ETosis is also trigged by various terrestrial protozoa and metazoa, considered nowadays as neozoan parasites, which are circulating in oceans worldwide and causing critical emerging marine diseases. Recent studies demonstrated that pinniped- and cetacean-derived polymorphonuclear neutrophils (PMNs) and monocytes are able to form different phenotypes of ET structures composed of nuclear DNA, histones, and cytoplasmic peptides/proteases against terrestrial apicomplexan parasites, e.g., Toxoplasma gondii and Neospora caninum. Detailed molecular analyses and functional studies proved that marine mammal PMNs and monocytes cast ETs in a similar way as terrestrial mammals, entrapping and immobilizing T. gondii and N. caninum tachyzoites. Pinniped- and cetacean leukocytes induce vital and suicidal ETosis, with highly reliant actions of nicotinamide adenine dinucleotide phosphate oxidase (NOX), generation of reactive oxygen species (ROS), and combined mechanisms of myeloperoxidase (MPO), neutrophil elastase (NE), and DNA citrullination via peptidylarginine deiminase IV (PAD4).This scoping review intends to summarize the knowledge on emerging protozoans in the marine environment and secondly to review limited data about ETosis mechanisms in marine mammalian species.

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

The St. Lawrence Estuary (SLE) beluga Delphinapterus leucas in Quebec, Canada, is endangered due to intensive hunting in the 19th and 20th centuries and subsequent anthropogenic contamination and human activities in the region. Infectious disease is a primary cause of death in this population. The protozoan parasite Toxoplasma gondii is reported in numerous marine mammal species, including beluga. In the present study, 55 tissue samples (heart and brain) collected from 34 stranded SLE beluga were analysed by PCR followed by DNA sequencing and restriction fragment length polymorphism analysis (RFLP) to determine the PCR prevalence and genotypes of T. gondii in these beluga. Of 34 beluga tested, 44% were positive for T. gondii by PCR, with males having a higher prevalence of infection than females and with more infected neonates and juveniles than adults. Molecular analyses indicated that all T. gondii infecting stranded SLE beluga grouped into genotype II, which predominates in humans. While our results indicate that a high prevalence of stranded beluga are PCR-positive for T. gondii infection, very few deaths are attributed to toxoplasmosis based on published necropsy results. Toxoplasma gondii can cause a range of diseases, including neurological deficits, and more data are needed to investigate this parasite's effect on population recovery.

Th2 cytokine bias induced by silver nanoparticles in peripheral blood mononuclear cells of common bottlenose dolphins (Tursiops truncatus)

BACKGROUND

Silver nanoparticles (AgNPs) have been widely used in many commercial products due to their excellent antibacterial ability. The AgNPs are released into the environment, gradually accumulate in the ocean, and may affect animals at high trophic levels, such as cetaceans and humans, via the food chain. Hence, the negative health impacts caused by AgNPs in cetaceans are of concern. Cytokines play a major role in the modulation of immune system and can be classified into two types: Th1 and Th2. Th1/Th2 balance can be evaluated by the ratios of their polarizing cytokines (i.e., interferon [IFN]-γ/Interleukin [IL]-4), and animals with imbalanced Th1/Th2 response may become more susceptible to certain kinds of infection. Therefore, the present study evaluated the in vitro cytokine responses of cetacean peripheral blood mononuclear cells (cPBMCs) to 20 nm citrate-AgNPs (C-AgNP20) by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR).

METHODS

Blood samples were collected from six captive common bottlenose dolphins (Tursiops truncatus). The cPBMCs were isolated and utilized for evaluating the in vitro cytokine responses. The cytokines evaluated included IL-2, IL-4, IL-10, IL-12, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α. The geometric means of two housekeeping genes (HKGs), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and β2-microglobulin (B2M), of each sample were determined and used to normalize the mRNA expression levels of target genes.

RESULTS

The ratio of late apoptotic/necrotic cells of cPBMCs significantly increased with or without concanavalin A (ConA) stimulation after 24 h of 10 µg/ml C-AgNP20 treatment. At 4 h of culture, the mRNA expression level of IL-10 was significantly decreased with 1 µg/ml C-AgNP20 treatment. At 24 h of culture with 1 µg/ml C-AgNP20, the mRNA expression levels of all cytokines were significantly decreased, with the exceptions of IL-4 and IL-10. The IFN-γ/IL-4 ratio was significantly decreased at 24 h of culture with 1 µg/ml C-AgNP20 treatment, and the IL-12/IL-4 ratio was significantly decreased at 4 or 24 h of culture with 0.1 or 1 µg/ml C-AgNP20 treatment, respectively. Furthermore, the mRNA expression level of TNF-α was significantly decreased by 1 µg/ml C-AgNP20 after 24 h of culture.

DISCUSSION

The present study demonstrated that the sublethal dose of C-AgNP20 (≤1 µg/ml) had an inhibitory effect on the cytokine mRNA expression levels of cPBMCs with the evidence of Th2 cytokine bias and significantly decreased the mRNA expression level of TNF-α. Th2 cytokine bias is associated with enhanced immunity against parasites but decreased immunity to intracellular microorganisms. TNF-α is a contributing factor for the inflammatory response against the infection of intracellular pathogens. In summary, our data indicate that C-AgNP20 suppresses the cellular immune response and thereby increases the susceptibility of cetaceans to infection by intracellular microorganisms.

NEUROPATHOLOGIC FINDINGS IN CETACEANS STRANDED IN ITALY (2002-14)

We summarized the neuropathologic findings in 60 cetaceans stranded along the Italian coastline from 2002 to 2014. The following neuropathologic changes were detected in 45% (27/60) of animals: nonsuppurative meningo-encephalitides (30%, 18/60), nonspecific lesions (12%, 7/60), suppurative encephalitis (2%, 1/60), and neoplasm (2%, 1/60). No histologic lesions were found in 47% (28/60) of the specimens. Five (8%, 5/60) samples were unsuitable for analysis. Analysis with PCR detected Brucella spp., morbillivirus, and Toxoplasma gondii infection in one, six, and seven individuals, respectively. Immunohistochemical analysis confirmed positivity for morbillivirus and for T. gondii infection in three cases each. No evidence of the scrapie-associated prion protein PrPSc was detected. Our findings underscore the importance of an adequate surveillance system for monitoring aquatic mammal pathologies and for protecting both animal and human health.

Bottlenose dolphins (Tursiops truncatus) do also cast neutrophil extracellular traps against the apicomplexan parasite Neospora caninum

Neutrophil extracellular traps (NETs) are web-like structures composed of nuclear DNA decorated with histones and cytoplasmic peptides which antiparasitic properties have not previously been investigated in cetaceans. Polymorphonuclear neutrophils (PMN) were isolated from healthy bottlenose dolphins (Tursiops truncatus), and stimulated with Neospora caninum tachyzoites and the NETs-agonist zymosan. In vitro interactions of PMN with the tachyzoites resulted in rapid extrusion of NETs. For the demonstration and quantification of cetacean NETs, extracellular DNA was stained by using either Sytox Orange® or Pico Green®. Scanning electron microscopy (SEM) and fluorescence analyses demonstrated PMN-derived release of NETs upon exposure to tachyzoites of N. caninum. Co-localization studies of N. caninum induced cetacean NETs proved the presence of DNA adorned with histones (H1, H2A/H2B, H3, H4), neutrophil elastase (NE), myeloperoxidase (MPO) and pentraxin (PTX) confirming the molecular properties of mammalian NETosis. Dolphin-derived N. caninum-NETosis were efficiently suppressed by DNase I and diphenyleneiodonium (DPI) treatments. Our results indicate that cetacean-derived NETs represent an ancient, conserved and relevant defense effector mechanism of the host innate immune system against N. caninum and probably other related neozoan parasites circulating in the marine environment.

Disseminated toxoplasmosis Toxoplasma gondii in a wild Florida manatee Trichechus manatus latirostris and seroprevalence in two wild populations

Marine mammals are important indicators for ecosystem health and serve as sentinel species for infectious agents including zoonoses. Histological examination of tissues from a stranded Florida manatee Trichechus manatus latirostris revealed protozoal cysts in the cerebrum and intrahistiocytic tachyzoites in the liver and caudal mesenteric lymph node. Disseminated Toxoplasma gondii infection was confirmed by immunohistochemistry and sequencing of the nuclear ribosomal internal transcribed spacer region of formalin-fixed tissues. The lack of baseline information on Florida manatees' exposure to this pathogen prompted a study into the seroprevalence of T. gondii in 2 separate geographic habitats in Florida, USA, during the winters from 2011-2014. Serum was collected during routine health assessments of 44 apparently healthy manatees from Crystal River (n = 26) on the west central coast of Florida and Brevard County (n = 18) on the east coast of Florida. Serum was screened for detection of T. gondii immunoglobulin G (IgG) antibodies via the modified agglutination test. Two animals from Crystal River from 2011 and 2012 (7.7%) and one animal from Brevard County from 2011 (5.6%) tested positive for T. gondii antibodies. Overall seroprevalence for T. gondii was low in the 2 sampled populations and may reflect a low seroprevalence or animal susceptibility. However, continued monitoring of this pathogen in aquatic ecosystems is warranted due to both possible anthropogenic sources and zoonotic potential.

Endoparasite survey of free-swimming baleen whales (Balaenoptera musculus, B. physalus, B. borealis) and sperm whales (Physeter macrocephalus) using non/minimally invasive methods

A number of parasitic diseases have gained importance as neozoan opportunistic infections in the marine environment. Here, we report on the gastrointestinal endoparasite fauna of three baleen whale species and one toothed whale: blue (Balaenoptera musculus), fin (Balaenoptera physalus), and sei whales (Balaenoptera borealis) and sperm whales (Physeter macrocephalus) from the Azores Islands, Portugal. In total, 17 individual whale fecal samples [n = 10 (B. physalus); n = 4 (P. macrocephalus); n = 2 (B. musculus); n = 1 (B. borealis)] were collected from free-swimming animals as part of ongoing studies on behavioral ecology. Furthermore, skin biopsies were collected from sperm whales (n = 5) using minimally invasive biopsy darting and tested for the presence of Toxoplasma gondii, Neospora caninum, and Besnoitia besnoiti DNA via PCR. Overall, more than ten taxa were detected in whale fecal samples. Within protozoan parasites, Entamoeba spp. occurred most frequently (64.7%), followed by Giardia spp. (17.6%) and Balantidium spp. (5.9%). The most prevalent metazoan parasites were Ascaridida indet. spp. (41.2%), followed by trematodes (17.7%), acanthocephalan spp., strongyles (11.8%), Diphyllobotrium spp. (5.9%), and spirurids (5.9%). Helminths were mainly found in sperm whales, while enteric protozoan parasites were exclusively detected in baleen whales, which might be related to dietary differences. No T. gondii, N. caninum, or B. besnoiti DNA was detected in any skin sample. This is the first record on Giardia and Balantidium infections in large baleen whales.

Endo- and ectoparasites of large whales (Cetartiodactyla: Balaenopteridae, Physeteridae): Overcoming difficulties in obtaining appropriate samples by non- and minimally-invasive methods

Baleen and sperm whales, belonging to the Order Cetartiodactyla, are the largest and heaviest existent mammals in the world, collectively known as large whales. Large whales have been subjected to a variety of conservation means, which could be better monitored and managed if physiological and pathophysiological information, such as pathogen infections, could already be gathered from free-swimming animals instead of carcasses. Parasitic diseases are increasingly recognized for their profound influences on individual, population, and even ecosystem health. Furthermore, a number of parasite species have gained importance as opportunistic neozoan infections in the marine environment. Nonetheless, traditional approaches to study parasitic diseases have been impractical for large whales, since there is no current routine method for the capture and handling of these large animals and there is presently no practical method to obtain blood samples remotely from free-ranging whales. Therefore, we here not only intend to review the endo- and ectoparasite fauna of large whales but also to provide new insights in current available methods for gathering parasitological data by using non- or minimally invasive sampling techniques. We focus on methods, which will allow detailed parasitological studies to gain a broader knowledge on parasitoses affecting wild, free-swimming large whale populations.

Harbour seal (Phoca vitulina) PMN and monocytes release extracellular traps to capture the apicomplexan parasite Toxoplasma gondii

Extracellular traps (ETs) are composed of nuclear DNA as backbone adorned with histones, cytoplasmic antimicrobial peptides/proteins which are released from a range of vertebrate and invertebrate host immune cells in response to several invading pathogens. Until now this ancient novel innate defence mechanism has not been demonstrated in any marine mammal. Interactions of harbour seal (Phoca vitulina)-PMN and -monocytes with viable tachyzoites of Toxoplasma gondii were investigated in this respect in vitro. For the demonstration and quantification of harbour seal PMN- and monocyte-derived ETs, extracellular DNA was stained with Sytox Orange. Fluorescence assays as well as scanning electron microscopy (SEM) analyses demonstrated PMN- and monocyte-promoted ET formation rapidly being induced upon contact with T. gondii-tachyzoites. The co-localisation of extracellular DNA decorated with histones (H3), neutrophil elastase (NE) and myeloperoxidase (MPO) in parasite entrapping structures confirmed the classical characteristics of PMN- and monocyte-promoted ETs. Exposure of harbour seal PMN and monocytes to viable tachyzoites resulted in a significant induction of ETs when compared to negative controls. Harbour seal-ETs were efficiently abolished by DNase I treatment and were reduced after PMN and monocytes pre-incubation with the NADPH oxidase inhibitor diphenilane iodondium. Tachyzoites of T. gondii were firmly entrapped and immobilised within harbour seal-ET structures. To our best knowledge, we here report for the first time on T. gondii-induced ET formation in harbour seal-PMN and -monocytes. Our results strongly indicate that PMN- and monocyte-triggered ETs represent a relevant and ancient conserved effector mechanism of the pinniped innate immune system as reaction against the pathogenic protozoon T. gondii and probably against other foreign pathogens occurring in the ocean environment.

Geographical patterns of Toxoplasma gondii genetic diversity revealed by multilocus PCR-RFLP genotyping

In recent years, an extensive collection of Toxoplasma gondii samples have been typed using a set of 10 PCR-RFLP genetic markers. Here we summarize the data reported until the end of 2012. A total of 1457 samples were typed into 189 genotypes. Overall, only a few genotypes dominate in the northern hemisphere, which is in stark contrast to the southern hemisphere where hundreds of genotypes coexist with none being notably dominant. PCR-RFLP genotype #1 (Type II clonal), #2 (Type III), #3 (Type II variant) and #10 (Type I) are identified globally. Genotypes #2 and #3 dominate in Africa, genotypes #9 (Chinese 1) and #10 are prevalent in Asia, genotypes #1, #2 and #3 are prevalent in Europe, genotypes #1, #2, #3, #4 and #5 dominate in North America (#4 and #5 are collectively known as Type 12). In Central and South America, there is no clear dominance of any genotype even though a few have relatively higher frequencies. Statistical analysis indicates significant differences among populations in Africa, Asia, Europe, North America, and Central and South America, with only Europe and North America exhibiting similar diversity. Collectively, the results revealed distinct population structures and geographical patterns of diversity in T. gondii.

Population genetics of Toxoplasma gondii: new perspectives from parasite genotypes in wildlife

Toxoplasma gondii, a zoonotic protozoal parasite, is well-known for its global distribution and its ability to infect virtually all warm-blooded vertebrates. Nonetheless, attempts to describe the population structure of T. gondii have been primarily limited to samples isolated from humans and domesticated animals. More recent studies, however, have made efforts to characterize T. gondii isolates from a wider range of host species and geographic locales. These findings have dramatically changed our perception of the extent of genetic diversity in T. gondii and the relative roles of sexual recombination and clonal propagation in the parasite's lifecycle. In particular, identification of novel, disease-causing T. gondii strains in wildlife has raised concerns from both a conservation and public health perspective as to whether distinct domestic and sylvatic parasite gene pools exist. If so, overlap of these cycles may represent regions of high probability of disease emergence. Here, we attempt to answer these key questions by reviewing recent studies of T. gondii infections in wildlife, highlighting those which have advanced our understanding of the genetic diversity and population biology of this important zoonotic pathogen.

Genetic characterisation of Toxoplasma gondii in wildlife from North America revealed widespread and high prevalence of the fourth clonal type

Little is known of the genetic diversity of Toxoplasma gondii circulating in wildlife. In the present study wild animals, from the USA were examined for T. gondii infection. Tissues of naturally exposed animals were bioassayed in mice for isolation of viable parasites. Viable T. gondii was isolated from 31 animals including, to our knowledge for the first time, from a bald eagle (Haliaeetus leucocephalus), five gray wolves (Canis lupus), a woodrat (Neotoma micropus), and five Arctic foxes (Alopex lagopus). Additionally, 66 T. gondii isolates obtained previously, but not genetically characterised, were revived in mice. Toxoplasma gondii DNA isolated from these 97 samples (31+66) was characterised using 11 PCR-restriction fragment length polymorphism (RFLP) markers (SAG1, 5'- and 3'-SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico). A total of 95 isolates were successfully genotyped. In addition to clonal Types II, and III, 12 different genotypes were found. These genotype data were combined with 74 T. gondii isolates previously characterised from wildlife from North America and a composite data set of 169 isolates comprised 22 genotypes, including clonal Types II, III and 20 atypical genotypes. Phylogenetic network analysis showed limited diversity with dominance of a recently designated fourth clonal type (Type 12) in North America, followed by the Type II and III lineages. These three major lineages together accounted for 85% of strains in North America. The Type 12 lineage includes previously identified Type A and X strains from sea otters. This study revealed that the Type 12 lineage accounts for 46.7% (79/169) of isolates and is dominant in wildlife of North America. No clonal Type I strain was identified among these wildlife isolates. These results suggest that T. gondii strains in wildlife from North America have limited diversity, with the occurrence of only a few major clonal types.

Genotyping of Toxoplasma gondii isolates in meningo-encephalitis affected striped dolphins (Stenella coeruleoalba) from Italy

This study reports the occurrence of Toxoplasma gondii in the brain of three striped dolphins (Stenella ceoruleoalba) found stranded on the Ligurian Sea coast of Italy between 2007 and 2008. These animals showed a severe, subacute to chronic, non-purulent, multifocal meningo-encephalitis, with the cerebral parenchyma of two dolphins harbouring protozoan cysts and zoites immunohistochemically linked to T. gondii. Molecular, phylogenetic and mutation scanning analyses showed the occurrence of Type II and of an atypical Type II T. gondii isolates in one and two dolphins, respectively. In spite of the different molecular patterns characterizing the above T. gondii genotypes, the brain lesions observed in the three animals showed common microscopic features, with no remarkable differences among them. The role of T. gondii in causing the meningo-encephalitis is herein discussed.

Polyparasitism is associated with increased disease severity in Toxoplasma gondii-infected marine sentinel species

In 1995, one of the largest outbreaks of human toxoplasmosis occurred in the Pacific Northwest region of North America. Genetic typing identified a novel Toxoplasma gondii strain linked to the outbreak, in which a wide spectrum of human disease was observed. For this globally-distributed, water-borne zoonosis, strain type is one variable influencing disease, but the inability of strain type to consistently explain variations in disease severity suggests that parasite genotype alone does not determine the outcome of infection. We investigated polyparasitism (infection with multiple parasite species) as a modulator of disease severity by examining the association of concomitant infection of T. gondii and the related parasite Sarcocystis neurona with protozoal disease in wild marine mammals from the Pacific Northwest. These hosts ostensibly serve as sentinels for the detection of terrestrial parasites implicated in water-borne epidemics of humans and wildlife in this endemic region. Marine mammals (151 stranded and 10 healthy individuals) sampled over 6 years were assessed for protozoal infection using multi-locus PCR-DNA sequencing directly from host tissues. Genetic analyses uncovered a high prevalence and diversity of protozoa, with 147/161 (91%) of our sampled population infected. From 2004 to 2009, the relative frequency of S. neurona infections increased dramatically, surpassing that of T. gondii. The majority of T. gondii infections were by genotypes bearing Type I lineage alleles, though strain genotype was not associated with disease severity. Significantly, polyparasitism with S. neurona and T. gondii was common (42%) and was associated with higher mortality and more severe protozoal encephalitis. Our finding of widespread polyparasitism among marine mammals indicates pervasive contamination of waterways by zoonotic agents. Furthermore, the significant association of concomitant infection with mortality and protozoal encephalitis identifies polyparasitism as an important factor contributing to disease severity in marine mammals.

Severity of toxoplasmosis, a water-borne zoonosis, varies widely from chronic and benign to acutely fatal. Here, we investigate polyparasitism (infection with multiple parasite species) as one factor governing the spectrum of disease in Toxoplasma gondii infections. This study utilized wild marine mammals as sentinels to detect contamination of waterways by T. gondii and a similar protozoan, Sarcocystis neurona, which have been linked to water-borne outbreaks in humans and wildlife along North America's Pacific Coast. Using genetic tools, we found high rates of protozoal infection, predominantly concomitant infections, in animals inhabiting major waterways of the Pacific Northwest. These dual infections of T. gondii and S. neurona were more frequently associated with mortality and protozoal encephalitis than single infections, indicating a role for polyparasitism in disease severity. Finally, rare T. gondii genotypes linked to a major human outbreak in the Pacific Northwest were abundant in marine mammals of the region, emphasizing wildlife as relevant sentinels for evaluation of human health risks. Our data implicate polyparasitism as a critical factor associated with the severity of protozoal disease. We also identify the need for vigilant surveillance of public waterways to prevent fecal contamination recurrently threatening human and wildlife health along the Pacific coast.

Cerebral toxoplasmosis in striped dolphins (Stenella coeruleoalba) stranded along the Ligurian Sea coast of Italy

This article reports the results of necropsy, parasitologic, microbiologic, histopathologic, immunohistochemical, indirect immunofluorescence, biomolecular, and serologic investigations on 8 striped dolphins (Stenella coeruleoalba) found stranded from August to December 2007 on the Ligurian Sea coast of Italy. Severe, nonsuppurative meningoencephalitis was found in 4 animals, as characterized by prominent perivascular mononuclear cell cuffing and macrophage accumulations in neuropil. These lesions were associated with mild lymphocytic-plasmacytic infiltration of choroid plexuses in 1 dolphin. Toxoplasma gondii cysts and zoites, confirmed by immunohistochemical labeling, were scattered throughout the brain parenchyma of 2 of the 4 dolphins. No viral inclusions were seen in the brain of any animal. Other findings included severe bronchointerstitial pneumonia and pulmonary atelectasis, consolidation, and emphysema. Parasites were identified in a variety of organs, including lung (Halocerchus lagenorhynchi). Microbiologic and serologic examinations for Brucella spp were negative on all 8 dolphins. The 4 animals with meningoencephalitis had serum antibodies against T gondii (titers ranging from 1:80 to 1:320) but not against morbillivirus. In contrast, the other 4 dolphins were seropositive for morbillivirus (with titers ranging from 1:10 to 1:40) but seronegative for T gondii. No morbillivirus antigen or nucleic acid was detected in the tissues of any dolphin. It is concluded that the severe lung and brain lesions were the cause of death and that T gondii was the likely etiologic agent of the cerebral lesions. Morbillivirus infection was not considered to have contributed to death of these animals.

Tracking transmission of the zoonosis Toxoplasma gondii

Toxoplasma gondii is a highly successful parasite that infects many host species and has colonised a wide range of habitats. Review of the parasite's life cycle demonstrates that it has become adapted to exploit multiple routes of transmission through a sexual cycle in the definitive host and asexually, through carnivory, and by vertical transmission. These alternative routes may operate synergistically to enhance transmission, but they might also provide a vehicle for selection leading to partitioning of strains in the environment. Genetic analysis has shown that parasite population structure varies globally. In South America, there is high strain diversity while in North America, Europe and Africa three clonal strain types predominate. This may imply a shift from sexual to asexual transmission. Mapping of the parasite genome has provided a wealth of markers for strain characterisation. Close genotyping of isolates gives evidence of multiple infection and recombination in natural populations and reveals differences in both the distribution and the phenotype of strains. More intensive epidemiological studies are now required to unravel the networks of transmission operating within defined habitats.

Toxoplasmosis in captive dolphins (Tursiops truncatus) and walrus (Odobenus rosmarus)

Toxoplasma gondii infection in marine mammals is intriguing and indicative of contamination of the ocean environment and coastal waters with oocysts. Toxoplasma gondii infection was detected in captive marine mammals at a sea aquarium in Canada. Antibodies to T. gondii were found in all 7 bottlenose dolphins (Tursiops truncatus) tested. Two of these dolphins, as well as a walrus (Odobenus rosmarus) at the facility, died. Encephalitis and T. gondii tissue cysts were identified in histological sections of the brain of 1 dolphin (dolphin no. 1). Another dolphin (dolphin no. 2) had mild focal encephalitis without visible organisms, but viable T. gondii was isolated by bioassay in mice and cats from its brain and skeletal muscle; this strain was designated TgDoCA1. The PCR-RFLP typing using 11 markers (B1, SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) identified a Type II strain. The DNA sequencing of B1 and SAG1 alleles amplified from TgDoCA1 and directly from the brains of dolphin no. 1 and the walrus showed archetypal alleles consistent with infection by a Type II strain. No unique polymorphisms were detected. This is apparently the first report of isolation of T. gondii from a marine mammal in Canada.