Metazoan parasites of California sea lions (Zalophus californianus): A new data and review

First record of Orthohalarachneattenuata in Arctocephalusaustralis in mainland Argentina (Parasitiformes, Mesostigmata, Dermanyssoidea, Halarachnidae) with observations on its ambulacral morphology

Pinniped respiratory mites of the species Orthohalarachneattenuata have been recorded from various locations around the world but not from continental Argentina. In the present work, we document for the first time the presence of O.attenuata on Arctocephalusaustralis on the Argentine mainland. A total of 23 adult and 381 immature mites were collected from the nose and nasopharyngeal cavity during a necropsy. The mite ambulacrum is described in adults and larvae. This structure consists of a pretarsus, an extensible pulvillum, a pair of claws and paradactyli (pretarsus opercula). The ambulacral structures also have some peculiarities, such as the presence of longitudinal furrows in the claws, straight claws in legs II and III (as opposed to curved in legs I and IV), and the fin-shaped paradactyli. The morphology of the ambulacrum of this mite is interpreted as an adaptation for anchoring to different surfaces of the host, and the protective structures present in the larvae as an adaptation for the dispersal phase in the external environment.

Non-invasive detection of Orthohalarachne attenuata (Banks, 1910) and Orthohalarachne diminuata (Doetschman, 1944) (Acari: Halarachnidae) in free-ranging synanthropic South American sea lions Otaria flavescens (Shaw, 1800)

Respiratory mites of the genera Orthohalarachne and Halarachne (Acari: Halarachnidae) are causative agents of nasopharyngeal/nasopulmonary acariasis in pinnipeds and sea otters. Until now, these endoparasitic mites were mainly diagnosed via necropsies and invasive procedures. So far, non-invasive diagnostic techniques have neither been developed nor applied in free-ranging pinnipeds. In the current study, we aimed to evaluate the halarachnid mite infestation status of free-ranging "urban" South American sea lions Otaria flavescens in the city of Valdivia, Chile. Therefore, non-invasive sampling methods were used in the current study, e. g. by observation-based sampling of freshly expectorated nasal mucus in the animal environment. Further, collection devices were developed for target-oriented sampling of sneezed nasal mucus, including sterile petri dishes and stretched clingfilms mounted on telescopic rods. Applying these techniques, 26 individual sputum samples were collected. 11.5% of sputum samples proved positive for halarachnid larvae (in total, n = 7), which were morphologically identified as Orthohalarachne attenuata (n = 2) or Orthohalarachne diminuata (n = 5). In one of the individual sea lion mucus samples, both Orthohalarachne species were detected, thereby confirming a patent co-infestation in vivo. 16S rDNA-based molecular identification of individual Orthohalarachne spp. larvae confirmed morphological findings. For the first time, we here molecularly characterized Orthohalarachne spp. on the basis of three gene regions [18S, 28S and the internal transcribed spacer 1 (ITS1)]. Overall, current data include the successful application of non-invasive techniques to sample halarachnid mites from free-ranging synanthropic pinnipeds and contribute to the current knowledge on respiratory mites infesting South American sea lions by combining morphological and molecular methods to overcome challenges in species identification. This study should further serve as baseline study and calls for more research on occurrence, biology and health implications of orthohalarachnosis in free-living as well as captive pinnipeds.

Revision of Corynosoma australe Johnston, 1937 (Acanthocephala: Polymorphidae) from a North American population using novel SEM images, Energy Dispersive X-ray Analysis, and molecular analysis

We describe a population of the acanthocephalan Corynosoma australe Johnston, 1937 (Polymorphidae) from a California sea lion Zalophus californianus (Lesson, 1828) in California using novel scanning electron microscopy (SEM) images, Energy Dispersive x-ray analysis (EDXA), and molecular analysis for the first time. The taxonomic history of C. australe is replete with accounts using only line drawings some of which proved erroneous. The distribution of ventral spines on the female trunk has been the primary distinction between C. australe and Corynosoma obtuscens Lincicome, 1943, its junior synonym; being continuous in the latter but discontinuous posteriorly in the former species. The distribution of ventral spines is invariably discontinuous in males. Our redescription and SEM images help to resolve this issue further validating the synonymy. Morphological variability has been documented between our California population and others from various host species in California, South Australia, South Shetlands, and the Argentinian coast. Our SEM images document features not previously detectable in line drawings, erroneously reported or missed in previous accounts. The EDXA spectra show high levels of calcium and phosphorous and low levels of sulfur characteristic of C. australe. EDXA for other species of Corynosoma Lühe, 1904 provide support for the diagnostic distinction of C. australe. EDXA spectra were shown to be species specific and have diagnostic value in the taxonomy of the Acanthocephala. Our molecular analysis used amplification of 18S of ribosomal DNA and cytochrome c oxidase 1 (Cox1) gene. Phylogenetic analyses for Cox1 gene revealed a close relationship between Corynosoma hannae Zdzitowiecki, 1984 and C. australe. The phylogenetic trees confirmed that the isolates belonged to C. australe. The haplotype network inferred by Cox1 with C. australe sequences revealed that haplotypes clearly separated from each other and formed clusters related to samples from the Northern Hemisphere (the USA and Mexico), and the second from the Southern Hemisphere (Argentina, Brazil and Peru).

First report of a severe nasopulmonary acariasis caused by Orthohalarachne diminuata Doetschmann, 1944 (Acari: Halarachnidae) in a captive South American sea lion (Otaria flavescens Shaw, 1800)

Obligatory endoparasitic mites of the genera Halarachne Allman, 1847 and Orthohalarachne Newell, 1947 (Acari: Halarachnidae) parasitize different segments of the respiratory tract of marine mammals, including pinnipeds and sea otters, and infestations can cause asymptomatic to serious respiratory diseases. However, knowledge on biology, pathogenic potential and occurrence of halarachnid mites infesting pinnipeds, especially in captivity, is scarce. A two-year-old South American sea lion (Otaria flavescens Shaw, 1800) male, born and held at the Vienna Zoo, was anesthesized for routine pre-transport examinations, including computed tomography, bronchoalveolar lavage, and blood sampling. During the final phase of general anesthesia, the individual abruptly became apneic and died despite all attempts at resuscitation. At necropsy, 45 highly motile whitish millimeter-sized structures were macroscopically detected in the trachea, bifurcatio tracheae and main bronchi and were identified as adult stages of Orthohalarachne diminuata Doetschman, 1944 following morphological descriptions. After trepanation of the nasal cavity and sinus paranasalis, a total of 407 larval and 3 nymphal specimens distributed in clusters were detected. Macroscopically, sinus mucosa showed hyperemia and multiple petechial hemorrhages. Histopathological analyses of paranasal sinuses revealed mite cross-sections surrounded by sanioserous exudate and epithelial exfoliation. For the first time, O. diminuata was molecularly characterized and phylogenetically analyzed based on its 16S rDNA. Our study constitutes the first record of a severe O. diminuata infestation in captive O. flavescens and one of the few host-parasite records in general. We present clinical data and pathological results, the first scanning electron microscopic images of a O. diminuata larval stage and discuss the etiology of this autochthonous infestation, possible transmission pathways and detrimental effects. Further studies on biology and pathogenic effects of halarachnid mites, as well as on the development of non-invasive sampling techniques are essentially required for a better understanding of (ortho-)halarachnosis in pinnipeds held in zoological gardens.

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First record of Orthohalarachne diminuata in a captive South American sea lion.

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One of the few host-parasite records.

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Autochthonous infestation, since infested animal was born in captivity.

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First scanning electron microscopic images of a O. diminuata larva.

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First molecular characterization and phylogenetic analysis of O. diminuata.

OPTIMIZATION OF FECAL FLOTATIONS IN MARINE PARASITOLOGY AND DETERMINATION OF THE SPECIFIC GRAVITY OF HELMINTH EGGS IN PINNIPEDS

Recent studies have sought to optimize the fecal flotation procedure to improve the detection of helminth eggs in terrestrial domestic species. It is unclear, however, whether these efforts in optimization are applicable to parasite species of marine environments, and verification of veterinary diagnostic procedures is clinically important. It was hypothesized that the eggs belonging to the parasites of pinnipeds would have different specific gravities (SpG) than those belonging to terrestrial hosts. Fecal samples were collected from each of 25 stranded pinnipeds representing three species (Zalophus californianus, Phoca vitulina, Mirounga angustirostris), and modified double centrifugal flotations were performed on 1-g samples. Among the 22 California sea lions sampled, trematode, ascarid, and cestode eggs were detected in 17/22 (77%), 10/22 (45%), and 4/22 (18%) individuals, respectively. Sugar-gradient modified centrifugation flotations were then conducted on a subset of 10 samples from California sea lions to evaluate the distribution of eggs in fractions representing varying SpG. Higher numbers of ascarid eggs were found in fractions representing a lower SpG (1.00-1.15), whereas trematode eggs belonging to the genus Zalophotrema were found in significantly higher numbers in the fraction representing 1.25 (P < 0.05). In conclusion, the SpG of trematode, ascarid, and cestode eggs from pinnipeds appears to be similar to those from terrestrial hosts, but numerous factors may affect their ability to be detected using traditional diagnostic approaches. Further exploration into the nature of the variability noted may lead to improved diagnostics in marine parasitology.

GEOGRAPHICAL VARIATION OF ENTEROPARASITISM IN THE SOUTHERN SEA LION OTARIA FLAVESCENS (SHAW, 1800) OFF THE COAST OF CHILE AS EVIDENCED WITH COPROLOGICAL TESTS: IMPLICATONS FOR ZOONOTIC RISKS

The scarce information on the helminth fauna in otariids from the Southeastern Pacific comes mainly from stranded individuals or killed for that purpose. In this study, we compared the abundance and composition of enteroparasitic assemblages of Otaria flavescens using coprological techniques. Three sampling localities from north to south spanning 2,200 km off the Chilean coast were considered (Iquique, Viña del Mar, and Talcahuano). In all, 60 fecal samples were collected, and eggs belonging to 5 taxa were found in 91.6% of the samples. They were the anisakid nematodes Contracaecum and Pseudoterranova, the cestode Adenocephalus (syn. Diphyllobothrium), the trematode Ogmogaster, and the acanthocephalan Corynosoma. Samples from southern Chile (Talcahuano) showed the highest prevalence. Adenocephalus eggs had the highest prevalence and abundance in Iquique and Talcahuano, whereas Ogmogaster was the less prevalent and abundant in all sampling localities. Corynosoma eggs had similar prevalence and abundance among sampling localities, and Pseudoterranova eggs were absent in Iquique and with median prevalence values in Viña del Mar and Talcahuano. Thus, the composition of parasite egg assemblages was different between sampling localities. These differences between sampling localities may help to explain differential records of some zoonotic parasitoses such as pseudoterranovosis and diphyllobothriosis in Peru and Chile, where consumption of raw or marinated fish (ceviche) is common. For example, the lower diversity of parasite egg assemblages in the northern Chilean coast may be due to the absence or lower abundance of first intermediate/paratenic hosts of Pseudoterranova.

Diphyllobothrium sprakeri n. sp. (Cestoda: Diphyllobothriidae): a hidden broad tapeworm from sea lions off North and South America

BACKGROUND

The systematic of several marine diphyllobothriid tapeworms of pinnipeds has been revised in recent years. However, 20 species of Diphyllobothrium from phocids and otariids are still recognized as incertae sedis. We describe a new species of Diphyllobothrium from the intestine of California sea lions Zalophus californianus (Lesson) (type-host) and South American sea lions Otaria flavescens (Shaw).

METHODS

Zalophus californianus from the Pacific coast of the USA and O. flavescens from Peru and Argentina were screened for parasites. Partial fragments of the large ribosomal subunit gene (lsrDNA) and the cytochrome c oxidase subunit 1 (cox1) mitochondrial gene were amplified for 22 isolates. Properly fixed material from California sea lions was examined using light and scanning electron microscopy.

RESULTS

A total of four lsrDNA and 21 cox1 sequences were generated and aligned with published sequences of other diphyllobothriid taxa. Based on cox1 sequences, four diphyllobothriid tapeworms from O. flavescens in Peru were found to be conspecific with Adenocephalus pacificus Nybelin, 1931. The other newly generated sequences fall into a well-supported clade with sequences of a putative new species previously identified as Diphyllobothrium sp. 1. from Z. californianus and O. flavescens. A new species, Diphyllobothrium sprakeri n. sp., is proposed for tapeworms of this clade.

CONCLUSIONS

Diphyllobothrium sprakeri n. sp. is the first diphyllobothriid species described from Z. californianus from the Pacific coast of North America, but O. flavescens from Argentina, Chile and Peru was confirmed as an additional host. The present study molecularly confirmed the first coinfection of two diphyllobothriid species in sea lions from the Southern Hemisphere.

Genetic diversity and phylogeography of Corynosoma australe Johnston, 1937 (Acanthocephala: Polymorphidae), an endoparasite of otariids from the Americas in the northern and southern hemispheres

Adult specimens of Corynosoma australe Johnston, 1937 were recorded from the intestines of California sea lions, Zalophus californianus (Lesson), from Baja California Peninsula, Mexico, whereas larval forms were collected from two fish species on the Argentinian coast. Adult specimens of C. australe were morphologically characterized by having a cylindrical proboscis with 18-20 rows of 12-14 hooks per row and a cylindrical trunk expanded anteriorly into a disk with tiny, triangular spines spreading almost to three quarters of the hind-trunk in males and to the posterior body end in females. The aim of this study was to explore the genetic diversity and systematic position of C. australe distributed in the Americas. Newly generated sequences of the mitochondrial cytochrome c oxidase subunit 1 (cox 1) gene were compared with sequences available from GenBank. Phylogenetic analyses performed with the cox 1 dataset using maximum likelihood and Bayesian inference showed that the 11 new sequences of C. australe recovered from the California sea lion in northern Mexico plus the six sequences from Argentinian seashores formed a clade with other sequences of specimens previously identified as C. australe. The intraspecific genetic divergence among the isolates was very low, ranging from 1 to 1.7%, and in combination with the phylogenetic trees confirmed that the isolates belonged to the same species. The cox 1 haplotype network inferred with 27 sequences revealed 18 haplotypes divided into two clusters clearly separated from each other by 5 substitutions. The first cluster corresponded to specimens from the Northern Hemisphere (United States of America and Mexico), and the second corresponded to specimens from the Southern Hemisphere (Argentina and Brazil). The current evidence suggests that C. australe has an amphitemperate distribution and is associated mainly with otariids with secondary and independent colonization events to other mammals and the Magellanic penguin in the Southern Hemisphere.

A novel quantitative real-time PCR diagnostic assay for fecal and nasal swab detection of an otariid lungworm, Parafilaroides decorus

Parafilaroides decorus, also known as sea lion lungworm, is a metastrongyloid nematode that infects otariid hosts, such as the charismatic California sea lion, Zalophus californianus. P. decorus causes bronchointerstitial pneumonia, respiratory distress, reduced ability to swim, dive and hunt and as a result, increased mortality particularly in young animals. Respiratory disease is a leading cause of stranding and admission to rehabilitation centers on the Pacific coast. Low-coverage genomic sequencing of four P. decorus individuals analyzed through Galaxy's RepeatExplorer identified a novel repeat DNA family we employed to design a sensitive quantitative PCR (qPCR) assay for diagnosing infections from fecal or sputum samples. The assay detects as little as 10 fg of P. decorus DNA and a linear regression model developed using a standard curve can be used to estimate the concentration of P. decorus DNA in a sample, ± 0.015 ng. This knowledge can be leveraged to estimate the level of parasite burden, which can be used to design improved treatments for animals in rehabilitation. Improved treatment of infections will aid in more animals being successfully released back into the wild.

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Developed qPCR assay for P. decorus.

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Sensitive to 10 fg.

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Applicable for feces or sputum.

Broad tapeworms (Diphyllobothriidae), parasites of wildlife and humans: Recent progress and future challenges

Tapeworms of the family Diphyllobothriidae, commonly known as broad tapeworms, are predominantly large-bodied parasites of wildlife capable of infecting humans as their natural or accidental host. Diphyllobothriosis caused by adults of the genera Dibothriocephalus, Adenocephalus and Diphyllobothrium is usually not a life-threatening disease. Sparganosis, in contrast, is caused by larvae (plerocercoids) of species of Spirometra and can have serious health consequences, exceptionally leading to host's death in the case of generalised sparganosis caused by 'Sparganum proliferum'. While most of the definitive wildlife hosts of broad tapeworms are recruited from marine and terrestrial mammal taxa (mainly carnivores and cetaceans), only a few diphyllobothriideans mature in fish-eating birds. In this review, we provide an overview the recent progress in our understanding of the diversity, phylogenetic relationships and distribution of broad tapeworms achieved over the last decade and outline the prospects of future research. The multigene family-wide phylogeny of the order published in 2017 allowed to propose an updated classification of the group, including new generic assignment of the most important causative agents of human diphyllobothriosis, i.e., Dibothriocephalus latus and D. nihonkaiensis. Genomic data of selected representatives have also begun to accumulate, promising future developments in understanding the biology of this particular group of parasites. The list of nominal species of taxonomically most complicated genus Spirometra as well as host-parasite list of 37 species of broad tapeworms parasitising marine mammals (pinnipeds and cetaceans) are also provided.