PHYLOGENETIC ANALYSIS OF THE LUNGWORMS (NEMATODA: METASTRONGYLOIDEA) INFERRED USING NUCLEAR RIBOSOMAL AND MITOCHONDRIAL DNA SEQUENCES

Phylogenetic relationships among the mammal-parasitic lungworms (Metastrongyloidea) were inferred using small- and large-subunit ribosomal DNA sequences together with 12S ribosomal mtDNA sequences. Maximum parsimony and Bayesian inference methods were used from optimal alignments and those filtered for alignment ambiguity. Analysis of 30 ingroup sequences using ribosomal DNA sequences yielded a single most parsimonious tree. Monophyly of the Metastrongyloidea was supported, but there was no support for monophyly of any of the 7 families as they have been traditionally defined. Parafilaroides decorus, an abursate lungworm of pinnipeds currently classified in the Filaroididae, was nested within a clade containing members of the Pseudaliidae, parasites of cetaceans. The tree also shows clades somewhat resembling the traditional familial divisions of the Metastrongyloidea, but in all groups, paraphyletic relationships were recovered. In a combined analysis of nuclear rDNA and 12S mtDNA, maximum parsimony and Bayesian analyses showed similar patterns to those observed with only nuclear rDNA sequences. Based on the phylogeny, the respiratory tract was inferred to be the ancestral predilection site for Metastrongyloidea, with multiple evolutionary invasions of extrapulmonary sites such as sinuses, circulatory system, and meninges. Similarly, the ancestral host was inferred to be a carnivore with subsequent colonization events into marsupial, rodent, artiodactyl, pinniped, and cetacean hosts.

HELMINTH FAUNA OF ICE SEALS IN THE ALASKAN BERING AND CHUKCHI SEAS, 2006-15

Climate warming may affect the distribution of helminth parasites, allowing endemic species to increase in prevalence and new species to appear. We analyzed tissues from 141 ice-associated seals collected in the Alaskan (US) Bering and Chukchi seas during 2006-15 for internal helminth parasites and compared results with past studies. Specimens were collected from: ringed seals (Pusa hispida), bearded seals (Erignathus barbatus), spotted seals (Phoca largha), and ribbon seals (Histriophoca fasciata). Helminths were present in 94% (133/141) of the seals sampled. Nematodes were most prevalent in bearded (97%, 72/74) and spotted seals (93%, 13/14). Cestodes were most prevalent in bearded seals (82%, 61/74) and absent in ribbon seals, trematodes were only found in bearded (64%, 47/74) and ringed (5%, 2/44) seals, and acanthocephalans were mostly found in ringed (61%, 27/44) and spotted (64%, 9/14) seals. Although no helminths were new to the Bering-Chukchi Seas region, this study found a previously unreported host record for the lungworm Parafilaroides (Filaroides) gymnurus in a ribbon seal. We also found the lungworm Otostrongylus circumlitus in a ribbon seal and P. (F.) gymnurus in bearded seals, representing location records previously unreported from the Bering-Chukchi Seas region (although they have been reported from the Sea of Okhotsk). We found the cestode genus Pyramicocephalus in bearded seals (3%, 2/74) at a lower prevalence than was reported previously for Pyramicocephalus phocarum (44-100%) in the Bering-Chukchi Seas region. We found no species of the acanthocephalan genus Bolbosoma, although the genus was previously identified in ringed, spotted, and ribbon seals. This study yielded no new helminths and no increases in the prevalence of endemic parasites in these seal species.

Lungworm infections in harbour porpoises (Phocoena phocoena) in the German Wadden Sea between 2006 and 2018, and serodiagnostic tests

Pseudaliid lungworm (Metastrongyloidea) infections and associated secondary bacterial infections may severely affect the health status of harbour porpoises (Phocoena phocoena) in German waters. The presented retrospective analysis including data from 259 harbour porpoises stranded between 2006 and 2018 on the German federal state of Schleswig-Holstein's North Sea coast showed that 118 (46%) of these stranded individuals harboured a lungworm infection. During this 13-year period, a significant difference in annual lungworm prevalence was only observed between the years 2006 and 2016. Lungworm coinfections of bronchi and pulmonary blood vessels were observed in 85.6% of positive cases. Mild infection levels were detected in 22.9% of infected animals and were most common in the age class of immature individuals (74.1%). Moderate and severe infections were present in 38.1% and 39.0% of the lungworm positive animals, respectively. Their distribution in immatures (51.1% and 54.3%) and adults (48.9% and 43.4%) did not show significant differences. In stranded animals, lungworm diagnosis can be easily obtained via necropsy, while reliable lungworm diagnosis in living porpoises requires invasive bronchoscopy or faecal examination, which is difficult to obtain in cetaceans. To overcome this issue, an enzyme-linked immunosorbent assay (ELISA) and immunoblot based on recombinant major sperm protein (MSP) of the cattle lungworm were evaluated as potential diagnostic tools in harbour porpoises. However, in contrast to hitherto other investigated host species, no reliable antibody response pattern was detectable in harbour porpoise serum/plasma or whole blood samples. Thus, MSP-based serological tests are considered unsuitable for lungworm diagnosis in harbour porpoises.

Intestinal parasites in Galapagos sea lions (Zalophus wollebaeki) Sivertsen, 1953 on San Cristóbal Island, Galápagos, Ecuador

Knowledge regarding endoparasites of Galapagos sea lions, Zalophus wollebaeki Sivertsen, 1953, is limited to 1 report. Herein, we examined feces extracted from the lower gastro-intestinal tract of 15 Galapagos sea lions (GSL) plus 14 fecal mounds nearby GSL at 4 locations on San Cristobal Island, Galapagos beginning in May continuing through June 2016. Using standard fecal flotation and sedimentation techniques, lungworm larvae, suggestive of Parafilaroides and Otostrongylus sp., eggs of pseudophyllidea cestodes and anisakid nematodes, and coccidian oocysts were collected from study samples. This is the first report of potential lungworm larvae, anisakids, pseudophyllidea cestodes and coccidian parasites in GSL.

Parasite Dispersal From the Ornamental Goldfish Trade

Goldfish, Carassius auratus Linnaeus, 1758, are immensely popular ornamental cyprinid fish, traded in more than 100 countries. For more than 500 years, human translocation has facilitated the spread of goldfish globally, which has enabled numerous and repeated introductions of parasite taxa that infect them. The parasite fauna assemblage of goldfish is generally well documented, but few studies provide evidence of parasite coinvasion following the release of goldfish. This review provides a comprehensive synopsis of parasites that infect goldfish in farmed, aquarium-held, native, and invasive populations globally and summarises evidence for the cointroduction and coinvasion of goldfish parasites. More than 113 species infect goldfish in their native range, of which 26 species have probably coinvaded with the international trade of goldfish. Of these, Schyzocotyle acheilognathi (Cestoda: Bothriocephalidae), Ichthyophthirius multifiliis (Ciliophora: Ichthyophthiriidae), Argulus japonicus (Crustacea: Argulidae), Lernaea cyprinacea (Crustacea: Ergasilidae), Dactylogyrus anchoratus, Dactylogyrus vastator and Dactylogyrus formosus (Monogenea: Dactylogyridae) are common to invasive goldfish populations in more than four countries and are considered a high risk of continued spread. Coinvasive parasites include species with direct and complex life cycles, which have successfully colonised new environments through utilisation of either new native hosts or suitable invasive hosts. Specifically, I. multifiliis, A. japonicus and L. cyprinacea can cause harm to farmed freshwater fish species and are important parasites to consider for biosecurity. These species may threaten other aquatic animal industries given their low host specificity and adaptable life histories. Future attention to biosecurity, management and border detection methods could limit the continued spread of exotic parasites from the ornamental trade of goldfish.

First record of Halocercus sp. (Pseudaliidae) lungworm infections in two stranded neonatal orcas (Orcinus orca)

Orca (Orcinus orca) strandings are rare and post-mortem examinations on fresh individuals are scarce. Thus, little is known about their parasitological fauna, prevalence of infections, associated pathology and the impact on their health. During post-mortem examinations of two male neonatal orcas stranded in Germany and Norway, lungworm infections were found within the bronchi of both individuals. The nematodes were identified as Halocercus sp. (Pseudaliidae), which have been described in the respiratory tract of multiple odontocete species, but not yet in orcas. The life cycle and transmission pathways of some pseudaliid nematodes are incompletely understood. Lungworm infections in neonatal cetaceans are an unusual finding and thus seem to be an indicator for direct mother-to-calf transmission (transplacental or transmammary) of Halocercus sp. nematodes in orcas.

Lungworm seroprevalence in free-ranging harbour seals and molecular characterisation of marine mammal MSP

Harbour seals (Phoca vitulina) are frequently infected with the lungworms Otostrongylus circumlitus and Parafilaroides gymnurus. The infection is often accompanied by secondary bacterial infections and can cause severe bronchopneumonia and even death in affected animals. Hitherto, the detection of lungworm infections was based on post mortem investigations from animals collected within stranding networks and a valid detection method for live free-ranging harbour seals was not available. Recently, an ELISA was developed for detecting lungworm antibodies in harbour seal serum, using major sperm protein (MSP) of the bovine lungworm, Dictyocaulus viviparus as recombinant diagnostic antigen. To determine lungworm seroprevalence in free-ranging harbour seals, serum was taken from four different seal age groups (n = 313) resulting in an overall prevalence of 17.9% (18.9% of males, 16.7% of females). 0.7% of harbour seals up to six weeks of age were seropositive, as were 89% of seals between six weeks and six months, 53.6% between six and 18 months and 24.2% of seals over 18 months of age. In the 18 months and over age group, seropositive animals showed statistically significant reductions in body weight (P = 0.003) and length (P < 0.001). Sera from lungworm infected harbour seals in rehabilitation (n = 6) revealed that duration of antibody persistence may be similar to that of lungworm infected cattle, but further studies are needed to confirm this. Phylogenetic analyses of MSP sequences of different marine and terrestrial mammal parasitic nematodes revealed that lungworm MSP of the genus Dictyocaulus (superfamily Trichostrongyloidea) is more closely related to metastrongylid marine mammal lungworms than to trichostrongylid nematodes of terrestrial hosts.

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First study on lungworm seroprevalence in live free-ranging harbour seals.

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Total seroprevalence was 17.9%, but age-dependent differences were observed.

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Six weeks to six months old seals showed highest prevalences (89% positives).

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Seropositive adult seals showed significantly reduced body weight and length.

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Phylogenetic tree construction using MSP of marine and terrestrial mammal parasites.

A recombinant antigen-based enzyme-linked immunosorbent assay (ELISA) for lungworm detection in seals

BACKGROUND

Pinnipeds are frequently infected by the lungworms Otostrongylus circumlitus and Parafilaroides gymnurus (Metastrongyloidea). Infections are frequently associated with secondary bacterial bronchopneumonia and are often lethal. To date, a reliable lungworm diagnosis in individual seals is only possible during necropsy as examination of faeces collected from resting places does not allow assignment to individuals. Therefore, a diagnostic tool for lungworm detection in living seals is desirable for monitoring health of seals in the wild and in captivity. Previously, an ELISA based on recombinant bovine lungworm major sperm protein (MSP) as diagnostic antigen was developed for lungworm diagnosis in cattle. In the present study, this test was adapted for detection of antibodies against lungworms in harbour (Phoca vitulina) and grey seals (Halichoerus grypus). Furthermore, sera of northern elephant seals (Mirounga angustirostris) were tested to evaluate whether the harbour/grey seal ELISA is suitable for this seal species as well.

METHODS

For ELISA evaluation, lungworm-positive and -negative sera of harbour and grey seals were analysed using horseradish peroxidase (HRP)-conjugated Protein A as secondary antibody. Optical density was measured and a receiver operating characteristic (ROC) analysis was performed to determine a cut-off value. Potential cross-reactions were examined by testing serum of seals positive for gastrointestinal and heart nematodes, but negative for lungworm infections. In addition, sera of northern elephant seals were analysed.

RESULTS

Harbour and grey seal serum samples showed significant differences in optical density (OD) between serum of infected and uninfected animals resulting in a cut-off value of 0.422 OD with a specificity of 100% (95% CI: 87.23-100%) and a sensitivity of 97.83% (95% CI: 88.47-99.94%). Cross-reactions with heart or gastrointestinal nematodes were not observed. Analysis of northern elephant seal samples resulted in detection of antibodies in animals positive for lungworm larvae at faecal examination.

CONCLUSIONS

The ELISA presented is a valuable method for detection of lungworm infections in live harbour and grey seals, providing a monitoring tool to reveal epidemiological dynamics of lungworm infections during health surveillance in free-ranging seals. Furthermore, ELISA results may aid institutions with harbour and grey seals under human care on decisions regarding anthelminthic treatment of individual animals.

Transmission of lungworms of harbour porpoises and harbour seals: molecular tools determine potential vertebrate intermediate hosts

Harbour porpoises (Phocoena phocoena) and harbour seals (Phoca vitulina) from German waters are infected by six species of lungworms (Metastrongyloidea). These nematodes parasitise the respiratory tract, are pathogenic and often cause secondary bacterial infections. In spite of their clinical and epidemiological significance, the life cycle and biology of lungworms in the marine environment is still largely unknown. Regions of ribosomal DNA (ITS-2) of all lungworms parasitising harbour porpoises and harbour seals in German waters were sequenced to characterise and compare the different species. The phylogenetic relationship among the lungworm species was analysed by means of their ITS-2 nucleotide sequences and the species-specific traits of the ITS-2 were used to screen wild fish as possible intermediate hosts for larval lungworms. Molecular markers were developed to identify larval nematodes via in-situ hybridisation of tissues of harbour porpoise and harbour seal prey fish. Potential wild intermediate fish hosts from the North Sea were dissected and found to harbour larval nematodes. Histological examination and in-situ hybridisation of tissue samples from these fish showed lungworm larvae within the intestinal wall. Based on larval ITS-2 nucleotide sequences, larval nematodes were identified as Pseudalius inflexus and Parafilaroides gymnurus. Turbot (Psetta maxima) bred and raised in captivity were experimentally infected with live L1s of Otostrongylus circumlitus and ensheathed larvae were recovered from the gastrointestinal tract of turbot and identified using molecular tools. Our results show that fish intermediate hosts play a role in the transmission of metastrongyloid nematodes of harbour porpoises and harbour seals.

Lungworm (Pharurus pallasii: Metastrongyloidea: Pseudaliidae) infection in the endangered St. Lawrence beluga whale (Delphinapterus leucas)

Eighty-eight percent of adult beluga whales, Delphinapterus leucas (age [Formula: see text]7 years; n = 32), and 72% of juveniles (1 year [Formula: see text] age < 7 years; n = 11) were infected with the cranial sinus nematode Pharurus pallasii. No fetuses or young of the year (age [Formula: see text]1 year; n = 9) were infected. The mean intensity of infection was 419 (range 2–2042) in adults and 179 (range 1–500) in juveniles. There was no difference in mean intensity of infection between the sexes or between juvenile and adult beluga. The absence of P. pallasii in young of the year suggests that transmission is not transplacental or transmammary and that infections are acquired as young beluga begin to feed on infected prey. Pharurus pallasii were 3 times more numerous in the peribullar sinuses than in the frontal sinuses, but were equally distributed laterally. Male and female P. pallasii in heavily infected sinuses were significantly longer than those in lightly infected sinuses. No intensity-dependent effect on fecundity of gravid females was observed. No macroscopic lesions were observed in association with P. pallasii in fresh or frozen carcasses. Low numbers of adult P. pallasii in the lungs suggest that the cranial sinuses are the preferred site of infection. No relationship was found between intensity of infection and body condition of beluga.

Experimental transmission of Pharurus pallasii (Nematoda: Metastrongyloidea), a lungworm of the cranial sinuses of the beluga whale (Delphinapterus leucas), to fish

Transmission of lungworms (Metastrongyloidea: Pseudaliidae) in the marine environment has been poorly studied. This experimental study is the first conducted on a pseudaliid, Pharurus pallasii, a lungworm of the cranial sinuses of the beluga whale (Delphinapterus leucas). First-stage larvae removed from uteri of gravid female P. pallasii from a freshly dead beluga were experimentally exposed to various marine organisms (fish, crustaceans, molluscs). First-stage larvae failed to develop in experimentally exposed invertebrates. The first moult occurred in the intestinal wall of American plaice (Hippoglossoides platessoides) and Arctic sculpins (Myoxocephalus scorpioides) 45 and 78 days post exposure, respectively. The third larval stage, which is infectious to the final host, was not observed in fish during the 14 months of the experiment. No cellular inflammatory reaction to or encapsulation of larvae was observed in histological sections of the intestinal wall of American plaice 268 days post exposure. Survival and development of P. pallasii larvae to the second stage in fish suggest that fish are likely suitable intermediate hosts in the life cycle of P. pallasii. Invertebrates may still play a role as transport (paratenic) hosts. The morphology of the first and second larval stages of P. pallasii is described for the first time.

Efficacy of ivermectin and moxidectin against Otostrongylus circumlitus and Parafilaroides gymnurus in harbour seals (Phoca vitulina)

Verminous bronchopneumonia caused by infection with Otostrongylus circumlitus and Parafilaroides gymnurus is an important cause of death during the rehabilitation of harbour seals (Phoca vitulina). During the winter of 2000/01, 35 juvenile harbour seals with severe clinical signs of verminous bronchopneumonia were treated with either 0.2 mg/kg ivermectin orally or 0.2 mg/kg moxidectin subcutaneously, and monitored for 30 days. The efficacy of the anthelmintics was determined by the pattern of larval excretion (Baermannisation) and the progress of the clinical signs. Both anthelmintics had reduced larval excretion by at least 99 per cent after 10 days, but the seals' rapid breathing rate and and dyspnoea returned to normal more quickly in the animals treated with moxidectin. The pharmacokinetics of the anthelmintics were determined by solid-phase extraction, and high-performance liquid chromatography with fluorescence detection. Moxidectin had a mean (sd) residence time of 9.04 (2.12) days compared with 4.83 (1.14) days for ivermectin.

Characterization of Otostrongylus circumlitus from Pacific harbor and northern elephant seals

Otostrongylus circumlitus (Railliet, 1899) from Pacific harbor seals (Phoca vitulina richardsi) and northern elephant seals (Mirounga angustirostris) were examined using morphological and molecular methods to determine whether northern elephant seals along the central California coast are infected by the same species of Otostrongylus as are Pacific harbor seals in the same area. Fixed nematodes were examined and measured using light microscopy. The polymerase chain reaction (PCR) was used to amplify and sequence the second internal transcribed spacer (ITS-2) and D3 expansion (26S) regions of ribosomal DNA of O. circumlitus from Pacific harbor and northern elephant seals. The ITS-2 region was also amplified from Parafilaroides sp. from the Pacific harbor seal, northern elephant seal, and California sea lion (Zalophus californianus) and used for restriction fragment length polymorphism (RFLP) analysis. Morphologically, it was not possible to distinguish O. circumlitus from Pacific harbor and northern elephant seals, and over a consensus length of 443 base pairs (bp) for ITS-2 and 321 bp for D3 the sequences of O. circumlitus from both hosts were identical. With the PCR-RFLP assay, it was possible to distinguish O. circumlitus from Parafilaroides sp. The results suggest that O. circumlitus is the same species in Pacific harbor and northern elephant seals, and molecular methods make it possible to distinguish this nematode from related nematodes.