Occurrence of Stenurus globicephalae (Nematoda: Pseudaliidae) in the blowhole of Globicephala macrorhynchus (Cetacea: Delphinidae) in Tasmania, Australia.

Information about parasites of cetaceans in Australia is scarce and mostly opportunistic. The morphology of specimens of the metastrongyloid Stenurus globicephalae Baylis & Daubney, 1925 (Nematoda: Pseudaliidae), collected from the blowhole of a pilot whale Globicephala macrorhynchus Gray, 1846 (Cetacea: Delphinidae) off northern Tasmania, Australia, were studied. Light and scanning electron microscopical examinations enabled a detailed redescription of this nematode species, including corrections of some inaccuracies in previous species descriptions, particularly those concerning cephalic and caudal structures. The presence of numerous ventrolateral oblique muscle bands, characteristic of the males of S. globicephalae, is reported for the first time. This is the second finding of this nematode parasite, in a different host species, in Tasmania.

Determinants of lungworm specificity in five cetacean species in the western Mediterranean.

BACKGROUND: Current data about Pseudaliidae show contrasting patterns of host specificity between congeneric species. We investigated how both contact and compatibility between hosts and parasites contributed to the patterns of lungworm infection observed in a community of five species of cetaceans in the western Mediterranean. METHODS: The lungs of 119 striped dolphins Stenella coeruleoalba, 18 bottlenose dolphins Tursiops truncatus, 7 Risso's dolphins Grampus griseus, 7 long-finned pilot whales Globicephala melas, and 6 common dolphins Delphinus delphis were analysed for lungworms. Parasites were identified by morphology and analysis of ITS2 sequences using both maximum likelihood and Bayesian inference methods. Body length was used as a proxy for lungworm species fitness in different hosts and compared with Kruskal-Wallis tests. Infection parameters were compared between cetacean species using Fisher's exact tests and Kruskal-Wallis tests. Phylogenetic specificity was explored by collating the overall lungworm species prevalence values in hosts from previous surveys in various localities. To explore the relative importance of vertical and horizontal transmission, Spearman's rank correlation was used to look for an association between host size and lungworm burden. A Mantel test was used to explore the association between lungworm species similarity and prey overlap using dietary data. RESULTS: Halocercus delphini had higher infection levels in striped dolphins and common dolphins; Stenurus ovatus had higher infection levels in bottlenose dolphins; and Stenurus globicephalae had higher infection levels in long-finned pilot whales. These results are congruent with findings on a global scale. Morphometric comparison showed that the larger nematodes were found in the same host species that had the highest parasite burden. Lungworms were found in neonatal striped dolphins and a Risso's dolphin, and there was a weak but significant correlation between host size and parasite burden in striped dolphins and bottlenose dolphins. There was also a weak but significant association between prey overlap and lungworm species similarity. CONCLUSIONS: Data indicate that phylogenetic specificity has an important role in governing host-parasite associations, as indicated by the higher infection levels and larger nematode size in certain hosts. However, diet can also influence infection patterns in these preferred hosts and contribute to less severe infections in other hosts.

The lungworm, Halocercus brasiliensis (Nematoda: Pseudaliidae), from Guiana Dolphins Sotalia guianensis from Brazil with Pathological Findings.

The Guiana dolphin, Sotalia guianensis, is a small cetacean species found on the Atlantic coast of Central and South America from Honduras to Santa Catarina State, Brazil. The nematode Halocercus brasiliensis infects this cetacean, resulting in lung pathologies and death. The present study aimed to conduct a morphological and morphometric study of specimens of H. brasiliensis collected from S. guianensis from the coast of the state of Espírito Santo, Brazil. For this study, 7 dolphins were collected and examined for the presence of lung parasites. Nematodes were collected and processed for light microscopy, and lung fragments were processed for histological analysis. The nematodes were identified as H. brasiliensis according to their morphology and morphometry. The histopathological analysis revealed mineralization of the bronchiolar cartilage and inflammatory process. The parasitic infections by H. brasiliensis in S. guianensis can contribute to the debilitating status of these cetaceans, resulting in their stranding and accidental capture in fishing nets.

Recent increase of ulcerative lesions caused by Anisakis spp. in cetaceans from the north-east Atlantic.

Species of Anisakis typically infect the stomach of cetaceans worldwide, often causing ulcerative lesions that may compromise the host's health. These nematodes also cause anisakiasis or allergic reactions in humans. To assess the risks of this emerging zoonosis, data on long-term changes in Anisakis infections in cetaceans are necessary. Here, we compare the prevalence and severity of ulcerative lesions caused by Anisakis spp. in five cetacean species stranded along the north-west Spanish coast in 2017-2018 with published data from 1991-1996. Open ulcers were found in 32/43 short-beaked common dolphins, Delphinus delphis; 3/5 striped dolphins, Stenella coeruleoalba; 1/7 bottlenose dolphins, Tursiops truncatus; and 1/3 harbour porpoises, Phocoena phocoena meridionalis; a single individual of long-finned pilot whale, Globicephala melas, was found uninfected. In common dolphins, the mean abundance of open ulcers per host was 1.1 (95% confidence interval: 0.8-1.3), with a maximum diameter (mean ± standard deviation) of 25.4 ± 16.9 mm. Stomachs with scars or extensive fibrosis putatively associated with Anisakis were detected in 14 and five animals, respectively. A molecular analysis based on the mitochondrial cytochrome c oxidase II gene using 18 worms from three cetacean species revealed single or mixed infections of Anisakis simplex sensu stricto and Anisakis pegreffii. Compared with the period 1991-1996, we found a strong increase of prevalence, abundance and extension of ulcerative lesions in most cetacean species. Anisakis populations could have increased in the study area over the last decades, although we cannot rule out that a higher environmental stress has also boosted the pathological effects of these parasites.

Reproductive inequalities in the acanthocephalan Corynosoma cetaceum: looking beyond 'crowding' effects.

BACKGROUND: At present, much research effort has been devoted to investigate overall ("average") responses of parasite populations to specific factors, e.g. density-dependence in fecundity or mortality. However, studies on parasite populations usually pay little attention to individual variation ("inequality") in reproductive success. A previous study on the acanthocephalan Corynosoma cetaceum in franciscana dolphins, Pontoporia blainvillei, revealed no overall intensity-dependent, or microhabitat effects, on mass and fecundity of worms. In this study, we investigated whether the same factors could influence mass inequalities for this species of acanthocephalan. METHODS: A total of 10,138 specimens of C. cetaceum were collected from 10 franciscanas accidentally caught in Buenos Aires Province between 1988 and 1990. To investigate mass inequalities, all the specimens were sexed, and females were classified according to their developmental stage and weighed. Additionally, the relationship between biomass and fecundity (estimated as the number of acanthors) was investigated for some females. Inequalities in fecundity and biomass were assessed using standard methods, i.e. the Lorenz curve and the Gini coefficient (G). RESULTS: We found a modest, but highly significant linear relationship between mass and fecundity. The G was very low (0.314) compared with that from other helminth species. G values were significantly lower in gravid females, which presumably exhibit a slow rate of growth. Also, G values significantly increased with total intensity, but only for gravid females, and the effect was more predictable considering only the intensity of gravid females. CONCLUSIONS: Apparently, high intensity infections increase inequality of reproducing females without producing "crowding" effects. Although several processes could generate this pattern, gravid females, at higher intensities, expanded their distribution and occupied gut chambers with contrasting environmental conditions, which might result in greater variability in body size. The observed inequalities are not expected to strongly influence the population genetics of C. cetaceum, but they reveal subtle individual effects beyond an overall population impact.

Metazoan parasites from odontocetes off New Zealand: new records.

Information about the parasite fauna of spectacled porpoises and cetaceans from New Zealand waters in general is scarce. This study takes advantage of material archived in collections of the Otago Museum in Dunedin and Massey University in Auckland, sampled from cetacean species found stranded along the New Zealand coastline between 2007 and 2014. Parasites from seven species of cetaceans (spectacled porpoise, Phocoena dioptrica (n = 2 individuals examined); pygmy sperm whale (n = 1); long-finned pilot whale, Globicephala melas (n = 1); Risso's dolphin, Grampus griseus (n = 1); short-beaked common dolphin, Delphinus delphis (n = 7); striped dolphin, Stenella coeruleoalba (n = 3) and dusky dolphin, Lagenorhynchus obscurus (n = 2)) from the respiratory and gastro-intestinal tract, cranial sinus, liver, urogenital and mammary tract, fascia and blubber were investigated. Ten parasite species were identified, belonging to the Nematoda (Stenurus minor, Stenurus globicephalae, Halocercus sp. (Pseudaliidae), Anisakis sp. (Anisakidae), Crassicauda sp. (Crassicaudidae)), Cestoda (Phyllobothrium delphini and Monorygma grimaldii (Phyllobothriidae)), Trematoda (Brachicladium palliata and Brachicladium delphini (Brachicladiidae)) and Crustacea (Scutocyamus antipodensis (Cyamidae)). Some of the parasite species encountered comprises new records for their host. Although the material was not sampled within a systematic parasitological survey, the findings contain valuable new information about the parasite fauna of rare, vagile and vulnerable marine wildlife from a remote oceanic environment.

The utility of diversity profiling using Illumina 18S rRNA gene amplicon deep sequencing to detect and discriminate Toxoplasma gondii among the cyst-forming coccidia.

Next-generation sequencing (NGS) has the capacity to screen a single DNA sample and detect pathogen DNA from thousands of host DNA sequence reads, making it a versatile and informative tool for investigation of pathogens in diseased animals. The technique is effective and labor saving in the initial identification of pathogens, and will complement conventional diagnostic tests to associate the candidate pathogen with a disease process. In this report, we investigated the utility of the diversity profiling NGS approach using Illumina small subunit ribosomal RNA (18S rRNA) gene amplicon deep sequencing to detect Toxoplasma gondii in previously confirmed cases of toxoplasmosis. We then tested the diagnostic approach with species-specific PCR genotyping, histopathology and immunohistochemistry of toxoplasmosis in a Risso's dolphin (Grampus griseus) to systematically characterise the disease and associate causality. We show that the Euk7A/Euk570R primer set targeting the V1-V3 hypervariable region of the 18S rRNA gene can be used as a species-specific assay for cyst-forming coccidia and discriminate T. gondii. Overall, the approach is cost-effective and improves diagnostic decision support by narrowing the differential diagnosis list with more certainty than was previously possible. Furthermore, it supplements the limitations of cryptic protozoan morphology and surpasses the need for species-specific PCR primer combinations.

Genetic diversity and population structure of Synthesium pontoporiae (Digenea, Brachycladiidae) linked to its definitive host stocks, the endangered Franciscana dolphin, Pontoporia blainvillei (Pontoporiidae) off the coast of Brazil and Argentina.

Pontoporia blainvillei (Gervais and d'Orbigny, 1844) is an endangered small cetacean endemic to South America with four Franciscana Management Areas (FMA) recognized as different population stocks. The role of the intestinal parasite Synthesium pontoporiae (Digenea: Brachycladiidae) as a possible biological marker to differentiate P. blainvillei stocks was evaluated using nuclear and mitochondrial DNA markers. Internal transcribed sequence 1 and 2 (ITS1 and ITS2) regions of S. pontoporiae did not show intraspecific variability. The mitochondrial NADH dehydrogenase subunit 3 (ND3) and cytochrome oxidase subunit I (COI) gene sequences suggested lack of population structure in S. pontoporiae and population expansion. The apparent panmixia of S. pontoporiae may be due to the high mobility of one or more of its intermediary hosts. Alternatively, it may be due to the small sample size. This result is incongruent with the previously proposed FMA.

Lesions associated with Halocercus brasiliensis Lins de Almeida, 1933 in the lungs of dolphins stranded in the Northeast of Brazil.

The parasitic fauna of cetaceans is an important tool for ecological studies, including analyses on the causes of death. Halocercus brasiliensis is a nematode frequently found in the bronchi and bronchioles of some cetaceans, and it is commonly associated with focal inflammation of the respiratory tract leading to bacterial pneumonia and septicemia and, sometimes, to death. The objective of this study was to report infections by H. brasiliensis in the respiratory tract of Delphinidae stranded on the northern seaside of Bahia, Sergipe, and south of Alagoas, all states in the northeast region of Brazil. A total of 30 individuals, 1 Feresa attenuate (pygmy killer whale), 9 Stenella clymene (Clymene dolphin), and 20 Sotalia guianensis (Guiana dolphin) were studied. In 16 of them, the presence of H. brasiliensis was observed with a mean intensity of 3.5 ± 0.6 (range 1-9) in the hosts. Macroscopically, parasitic calcified nodules, lung congestion, edema, and emphysema were observed. Histopathological examination showed interstitial and granulomatous pneumonia with multifocal infiltrates, discrete to moderate edema, congestion, diffuse hemorrhage, and foci of calcification. We conclude that parasitic pneumonia in the sampled individuals may have directly contributed to stranding and death of the animals.

Toxoplasmosis in a Guiana dolphin (Sotalia guianensis) from Paraná, Brazil.

This study describes toxoplasmosis in a by caught Guiana dolphin (Sotalia guinensis) from Paranaguá Bay, Paraná, Brazil. Interstitial pneumonia, multisystemic arteritis, multifocal adrenalitis and hepatitis were the primary lesions observed. These tissues had moderate to severe necrosis and mononuclear cells infiltration usually surrounded by tachyzoites and tissue cysts. Moderate lymphoid depletion was evident in the spleen. Toxoplasma gondii was positive by immunohistochemical and ultrastructural evaluation. Furthermore, the animal was negative for Morbillivirus by immunohistochemistry and had low levels of persistent organochlorines. There is evidence of environmental changes in the Paranaguá Bay that could justify the occurrence of toxoplasmosis in Guiana dolphin. The sewage run-off from main urban areas and the presence of domestic and wild felids in areas surrounding the bay could be a source of T. gondii oocysts from land to sea. Based on its habitat, the authors recommend this dolphin species as sentinels for the health of bays and estuaries where they occur.

An atypical genotype of Toxoplasma gondii as a cause of mortality in Hector's dolphins (Cephalorhynchus hectori).

Hector's dolphins (Cephalorhynchus hectori) are a small endangered coastal species that are endemic to New Zealand. Anthropogenic factors, particularly accidental capture in fishing nets, are believed to be the biggest threat to survival of this species. The role of infectious disease as a cause of mortality has not previously been well investigated. This study investigates Toxoplasma gondii infection in Hector's dolphins, finding that 7 of 28 (25%) dolphins examined died due to disseminated toxoplasmosis, including 2 of 3 Maui's dolphins, a critically endangered sub-species. A further 10 dolphins had one or more tissues that were positive for the presence of T. gondii DNA using PCR. Genotyping revealed that 7 of 8 successfully amplified isolates were an atypical Type II genotype. Fatal cases had necrotising and haemorrhagic lesions in the lung (n=7), lymph nodes (n=6), liver (n=4) and adrenals (n=3). Tachyzoites and tissue cysts were present in other organs including the brain (n=5), heart (n=1), stomach (n=1) and uterus (n=1) with minimal associated inflammatory response. One dolphin had a marked suppurative metritis in the presence of numerous intra-epithelial tachyzoites. No dolphins had underlying morbillivirus infection. This study provides the first evidence that infectious agents could be important in the population decline of this species, and highlights the need for further research into the route of entry of T. gondii organisms into the marine environment worldwide.

Patterns of trunk spine growth in two congeneric species of acanthocephalan: investment in attachment may differ between sexes and species.

Acanthocephalans have evolved a hooked proboscis and some taxa have trunk spines to attach to their definitive hosts. These structures are generated before being used, thus a key question is how investment in attachment could optimally be allocated through the ontogeny. The number and arrangement of hooks and spines are never modified in the definitive host, but it is unclear whether these structures grow during adult development. A comparison of the size of trunk spines between cystacanths and adults of Corynosoma cetaceum and C. australe indicated that spines grow in both species, but only in females, which also had significantly larger spines than males. This sexual dimorphism did not result from pure allometry because the body of females was smaller, and did not grow more than that of males. However, having a longer lifespan, females would need to withstand the extreme flow conditions prevailing in marine mammals for longer, inducing different investment and development schedules for spines. Patterns of spine growth also differed between species: fore-trunk spines grew in both species, but hind-trunk spines did only in C. cetaceum. In conclusion, investment strategies on attachment may differ, not only between congeneric species of acanthocephalan, but also between sexes of the same species.

Assessing host-parasite specificity through coprological analysis: a case study with species of Corynosoma (Acanthocephala: Polymorphidae) from marine mammals.

In this paper we report an investigation of the utility of coprological analysis as an alternative technique to study parasite specificity whenever host sampling is problematic; acanthocephalans from marine mammals were used as a model. A total of 252 scats from the South American sea lion, Otaria flavescens, and rectal faeces from 43 franciscanas, Pontoporia blainvillei, from Buenos Aires Province, were examined for acanthocephalans. Specimens of two species, i.e. Corynosoma australe and C. cetaceum, were collected from both host species. In sea lions, 78 out of 145 (37.9%) females of C. australe were gravid and the sex ratio was strongly female-biased. However, none of the 168 females of C. cetaceum collected was gravid and the sex ratio was not female-biased. Conversely, in franciscanas, 14 out of 17 (82.4%) females of C. cetaceum were gravid, but none of 139 females of C. australe was, and the sex ratio of C. cetaceum, but not that of C. australe, was female-biased. In putative non-hosts, the size of worms was similar to that from specimens collected from prey. Results suggest that both acanthocephalans contact sea lions and franciscanas regularly. However, C. australe and C. cetaceum cannot apparently reproduce, nor even grow, in franciscanas and sea lions, respectively. Coprological analysis may represent a useful supplementary method to investigate parasite specificity, particularly when host carcasses are difficult to obtain.

The Synthesium Brachycladiidae Odhner, 1905 (Digenea) association with hosts based on nuclear and mitochondrial genes.

Synthesium pontoporiae, exclusive parasite of the endangered dolphin, Pontoporia blainvillei, is endemic and restricted to the South Atlantic and belongs to the Brachycladiidae family Odhner, 1905. The study of this family has been limited by the difficulty of accessing the parasites from their marine mammal hosts and as a consequence there is a paucity of genetic information available. Herein we present a genetic analysis using 18S rDNA sequences of S. pontoporiae and S. tursionis and the ND3 mtDNA sequence of S. pontoporiae. The genetic analysis of 18S rDNA sequences of brachycladiids and acanthocolpids determined two major clusters associated with their definitive hosts, marine mammals and fishes, respectively. Considering the tree topology of brachycladiids ND3 mtDNA gene, two clusters were defined, one with the Synthesium species. This work contributes with fundamental genetic information on S. pontoporiae, and suggests a Brachycladiidae genetic evolution related to their hosts.

Seroprevalence of Toxoplasma gondii in free-living Amazon River dolphins (Inia geoffrensis) from central Amazon, Brazil.

Toxoplasma gondii is an important pathogen in aquatic mammals and its presence in these animals may indicate the water contamination of aquatic environment by oocysts. Serum samples from 95 free-living Amazon River dolphins (Inia geoffrensis) from the Mamirauá Sustainable Development Reserve (RDSM), Tefé, Amazonas, Central Amazon, Brazil were tested for T. gondii antibodies using the modified agglutination test (MAT). Antibodies (MAT ≥ 25) to T. gondii were found in 82 (86.3%) dolphins with titers of 1:25 in 24, 1:50 in 56, and 1:500 in 2. Results suggest a high level contamination of the aquatic environment of the home range of these animals.

Host specificity of Oschmarinella rochebruni and Brachycladium atlanticum (Digenea: Brachycladiidae) in five cetacean species from western Mediterranean waters.

We investigated patterns of specificity of liver flukes (fam. Brachycladiidae) in a community of cetaceans from the western Mediterranean. The liver and pancreas of 103 striped dolphins, Stenella coeruleoalba, 18 Risso's dolphins, Grampus griseus, 14 bottlenose dolphins, Tursiops truncatus, 8 common dolphins, Delphinus delphis, and 5 long-finned pilot whales, Globicephala melas, were analysed for brachycladiid species. Two species were found: Oschmarinella rochebruni in striped dolphins (prevalence (P): 61.2%; mean intensity (MI) (95% CI): 34.2 (25.7-45.6)), and Brachycladium atlanticum in striped dolphins (P: 39.8%; MI: 7.1 (4.8-13.1)) and a single individual of common dolphin (P: 12.5%; intensity: 19), which represents a new host record. A molecular analysis using the internal transcribed spacer 2 (ITS2) region of the rDNA gene confirmed that specimens of B. atlanticum were conspecific regardless of host species. Available dietary data suggest that Risso's dolphins, bottlenose dolphins and long-finned pilot whales would contact rarely, if at all, the infective stages of O. rochebruni and B. atlanticum. Neither the prevalence nor the mean abundance of B. atlanticum differed significantly between striped and common dolphins, but a principal component analysis using seven morphometric variables indicated that specimens collected from the common dolphin were stunted. These worms also had fewer eggs compared with specimens typically found in striped dolphins, although the size of the eggs was similar in both host species. Dwarfism and low fecundity have typically been found in helminths infecting unusual host species, and might reflect the lower compatibility of B. atlanticum for common dolphins. In summary, both O. rochebruni and B. atlanticum appear to exhibit a narrow specificity for striped dolphins in the western Mediterranean.

Eighteen-year study of South Australian dolphins shows variation in lung nematodes by season, year, age class, and location.

Between 1990 and 2007, carcasses of opportunistically collected short-beaked common dolphins (Delphinus delphis; n=238), Indo-Pacific bottlenose dolphins (Tursiops aduncus; n=167), and common bottlenose dolphins (Tursiops truncatus; n=15) were examined for parasites and life history data. Three species of lung nematodes (Halocercus lagenorhynchi, Stenurus ovatus, Pharurus alatus) were identified in surface nodules, subsurface lesions, or airways. Nematode burdens were light to heavy and, in many cases, would have compromised the dolphins' health. The number of dolphins infected was related to species, year, season, age class, and geographic region. Nematodes were found in all three species but were more prevalent in short-beaked common dolphins (mean annual prevalence=26%) than in bottlenose dolphins (12%). There was a significant increase in prevalence of nematodes in short-beaked common dolphins in 2005-06 (63%) compared to 1990-2004 (14%), with a peak in April-June. More young short-beaked common dolphins were infected than subadults and adults and, during the unusual infection event, there were more dependent calves (<130 cm) than juveniles. There were also more infections in dependent bottlenose dolphin (Tursiops spp.) calves but no increase in overall prevalence was detected during 2005-06. Because neonates of both short-beaked common dolphins and bottlenose dolphins were infected, mother-to-calf transmission is suspected for these species in South Australia. Numbers of infections in short-beaked common dolphins were higher in Gulf St Vincent than elsewhere in South Australia, particularly in 2005-06. The cause of the unusual infection event in short-beaked common dolphins is unknown. We discuss the influence of dolphin diet, life history, and external factors.

Helminths of Sotalia guianensis (Cetacea: Delphinidae) from the south and southeastern coasts of Brazil.

From May 1997 to October 2000, 49 Sotalia guianensis (tucuxi dolphin) incidentally caught in fishing nets or stranded in São Paulo (SP) and Paraná (PR) states in Brazil were necropsied. In total, 17 lungs, 35 stomachs, and 30 intestines were analyzed. Contents were washed through a sieve (mesh, 150 mm) and examined under a stereoscopic microscope for parasites. Histopathologic analyses were performed in the lungs of five infected dolphins. The nematode Halocercus brasiliensis was found in 88% of all lungs examined, inducing moderate-to-severe pneumonia. Braunina cordiformis, Anisakis sp., and acanthocephalans were found in the stomachs. The trematode Synthesium tursionis was the only parasite found in the intestines, and it was identified in 73% of the animals necropsied. No macroscopic lesions were seen due to parasites in the stomachs and intestines analyzed.