Baylisascaris potosis n. sp., a new ascarid nematode isolated from captive kinkajou, Potos flavus, from the Cooperative Republic of Guyana

Morphology and ASAP analysis of the important zoonotic nematode parasite Baylisascaris procyonis (Stefahski and Zarnowski, 1951), with molecular phylogenetic relationships of Baylisascaris species (Nematoda: Ascaridida)

Species of Baylisascaris (Nematoda: Ascarididae) are of great veterinary and zoonotic significance, owing to cause Baylisascariosis or Baylisascariasis in wildlife, captive animals and humans. However, the phylogenetic relationships of the current 10 Baylisascaris species remain unclear. Moreover, our current knowledge of the detailed morphology and morphometrics of the important zoonotic species B. procyonis is still insufficient. The taxonomical status of B. procyonis and B. columnaris remains under debate. In the present study, the detailed morphology of B. procyonis was studied using light and scanning electron microscopy based on newly collected specimens from the raccoon Procyon lotor (Linnaeus) in China. The results of the ASAP analysis and Bayesian inference (BI) using the 28S, ITS, cox1 and cox2 genetic markers did not support that B. procyonis and B. columnaris represent two distinct species. Integrative morphological and molecular assessment challenged the validity of B. procyonis, and suggested that B. procyonis seems to represent a synonym of B. columnaris. Molecular phylogenetic results indicated that the species of Baylisascaris were grouped into 4 clades according to their host specificity. The present study provided new insights into the taxonomic status of B. procyonis and preliminarily clarified the phylogenetic relationships of Baylisascaris species.

PHYLOGEOGRAPHY OF BAYLISASCARIS PROCYONIS (RACCOON ROUNDWORM) IN NORTH AMERICA

Sequences of the mitochondrial cytochrome c oxidase 1 (COI) gene of 115 Baylisascaris procyonis individuals from 13 U.S. states and 1 Canadian province were obtained from 44 raccoon hosts to assess genetic variation and geographic structure. The maximum genetic distance between individuals was low (1.6%), consistent with a single species. Moderate COI haplotype (h = 0.60) and nucleotide (π = 0.0053) diversity were found overall. Low haplotype diversity was found among samples east of the Mississippi River (h = 0.036), suggesting that historical growth and expansion of raccoon populations in this region could be responsible for high parasite gene flow or a selective sweep of B. procyonis mtDNA. There was low genetic structure (average Φst = 0.07) for samples east of the continental divide, but samples from Colorado showed higher diversity and differentiation from midwestern and eastern samples. There was marked genetic structure between samples from east and west of the continental divide, with no haplotypes shared between these regions. There was no significant isolation by distance among any of these geographic samples. The phylogeographic patterns for B. procyonis are similar to genetic results reported for their raccoon definitive hosts. The phylogeographic divergence of B. procyonis from east and west of the continental divide may involve vicariance resulting from Pleistocene glaciation and associated climate variation.

Experimental Infection with Baylisascaris Potosis in Chickens

The larvae of the genus Baylisascaris can cause larva migrans in mammals and birds. This study investigated the larval migration of Baylisascaris potosis, the roundworm of kinkajou (Potos flavus), in chickens and the associated clinical manifestations of the host. Thirty-six 3-week-old chickens divided into 6 groups were orally inoculated with 3,000 B. potosis eggs/chick. Each group of chicken was necropsied at days 1, 2, 3, 7, 30 and 90 PI (post inoculation), and the number of larvae in various organs were counted until day 90 PI. No clinical signs were observed in chickens during the study. Larvae were detected from the liver, lungs or breast-muscles of 13/36 (36.1%) chickens. The mean total number of larvae in the liver, lungs and breast-muscles at days 1, 2, 3, 7, 30 and 90 PI were 0.34, 0.17, 1.66, 1.01, 0.17 and 0, respectively. No larvae were found in the brain, eyes, hid-limb muscles, heart, kidneys and spleen. Although infectivity of larvae in egg-inoculated chickens was low, the present study demonstrated that B. potosis larvae can migrate in chickens tissues up to day 30 PI. The result suggests that chickens can serve as a paratenic host for B. potosis and may underline a public health importance of B. potosis infection as a potential foodborne disease in humans.

Baylisascaris Potosis Larvae in Mice of Different Strains and Infectivity of Tissue Larvae

Migration of Baylisascaris potosis larvae in different mouse strains were compared, and infectivity of the persisting larvae in mice tissues were investigated. Five strains of mice, BALB/c, C57BL/6, AKR, B10.BR, and ICR were inoculated with 1,000 B. potosis eggs/mouse, and necropsied at week 13 post inoculation (PI). The other uninfected ICR mice (secondary host) were inoculated with 43 larvae/ mouse recovered from mice at week 13 PI with eggs, and necropsied at day 21 PI. Larvae in organs or tissues were counted at necropsy. One AKR mouse showed torticollis and circling at day 56 PI. At necropsy at week 13 PI, larvae were recovered from all mice. A mean total larvae recovered were 124.1 (n=40). Majority of larvae were found in the carcass (mean 113.9) and some in the viscera (mean 9.9). Zero to 1 larva were found in the brain or eyes of some mice. There were no differences among the mouse strains in the number of larvae, except in the viscera; more larvae were seen in BALB/c or ICR than in B10.BR mice. No larvae were found in the secondary host mice. Present study demonstrated that B. potosis larvae migrate well in the carcass of any strains of mice, however, the tissue larvae did not infect the secondary host. Results of our present study suggest that B. potosis larvae is less aggressive for the nervous tissue migration than that of B. procyonis larvae which is commonly known to migrate in central nervous system of mammals and birds.

Experimental comparison of Baylisascaris procyonis definitive host competence between domestic dogs and raccoons (Procyon lotor)

Domestic dogs can function as either paratenic or definitive hosts for the zoonotic raccoon roundworm Baylisascaris procyonis. However, factors leading to development of patent infections in dogs are under-studied. Here we compared infection dynamics of B. procyonis in dogs vs the natural raccoon host. Dogs and raccoons were inoculated 5000 or 500 B. procyonis eggs (n = 3 per dose) or were fed B. procyonis-infected laboratory mice (n = 3 per dose; mice inoculated with 1000 or 250 eggs). Fecal samples were analysed via flotation and a commercial coproantigen ELISA designed for detection of Toxocara spp. Two of 12 dogs (both received low dose larvae) developed patent infections; all 12 raccoons became infected with 10 developing patent infections. Compared with dogs, prepatent periods were shorter in raccoons and maximum egg outputs were much greater. Baylisascaris procyonis coproantigens were detectable via ELISA in all raccoons and the patently infected dogs. Finally, dogs spontaneously lost infections while all patently infected raccoons shed eggs until conclusion of the study. Our results demonstrate that dogs are clearly suboptimal hosts showing limited parasite establishment and fecundity vs raccoons. Despite the low competence, patently infected dogs still pose a risk for human exposure, emphasizing the importance of control measures.

Molecular phylogenetics and species-level systematics of Baylisascaris

Nucleotide sequences representing nine genes and five presumptive genetic loci were used to infer phylogenetic relationships among seven Baylisascaris species, including one species with no previously available molecular data. These genes were used to test the species status of B. procyonis and B. columnaris using a coalescent approach. Phylogenetic analysis based on combined analysis of sequence data strongly supported monophyly of the genus and separated the species into two main clades. Clade 1 included B. procyonis, B. columnaris, and B. devosi, species hosted by musteloid carnivores. Clade 2 included B. transfuga and B. schroederi from ursids, B. ailuri, a species from the red panda (a musteloid), and B. tasmaniensis from a marsupial. Within clade 2, geographic isolates of B. transfuga, B. schroederi (from giant panda), and B. ailuri formed a strongly supported clade. In certain analyses (e.g., some single genes), B. tasmaniensis was sister to all other Baylisascaris species rather than sister to the species from ursids and red panda. Using one combination of priors corresponding to moderate population size and shallow genetic divergence, the multispecies coalescent analysis of B. procyonis and B. columnaris yielded moderate support (posterior probability 0.91) for these taxa as separate species. However, other prior combinations yielded weak or no support for delimiting these taxa as separate species. Similarly, tree topologies constrained to represent reciprocal monophyly of B. columnaris and B. procyonis individuals (topologies consistent with separate species) were significantly worse in some cases, but not others, depending on the dataset analyzed. An expanded analysis of SNPs and other genetic markers that were previously suggested to distinguish between individuals of B. procyonis and B. columnaris was made by characterization of additional individual nematodes. The results suggest that many of these SNPs do not represent fixed differences between nematodes derived from raccoon and skunk hosts.

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A phylogenetic hypothesis for Baylisascaris species was produced using nine genes.

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Genetic data was generated for two new species- B. devosi and B. tasmaniensis.

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Baylisascaris devosi and B. tasmaniensis were part of a monophyletic Baylisascaris.

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B. procyonis (raccoon) and B. columnaris (skunk) could not be reliably distinguished.

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Established SNPs may not be diagnostic for Baylisascaris from raccoons and skunks.

Larva Migrans of Baylisascaris potosis In Experimental Animals

Occurrence of clinical signs by infection with Baylisascaris potosis, the roundworm of kinkajous ( Potos flavus), in mice, rats, and rabbit were studied, and the migration behavior of larvae in mice were compared with that of Baylisascaris transfuga, the roundworm of bears ( Ursus spp.). Three groups of 8 mice, 3 groups of 6 rats, and 3 groups of 2 rabbits were inoculated with either 10, 100, or 1,000 B. potosis eggs. The other 8 mice were inoculated with 1,000 B. transfuga eggs. Animals were monitored for the occurrence of clinical signs until 60 days postinoculation (DPI). The carcass, viscera, brain, and eyes of each of 6 mice inoculated with 1,000 eggs of B. potosis or B. transfuga at 60 DPI were removed individually, and the number of larvae was counted. One mouse inoculated with 100 B. potosis eggs showed rolling at 27 DPI, and 1 larva was found in the medulla oblongata of this mouse. No clinical signs were observed in the other mice or in the rats and rabbits. A mean of 387.2 larvae was recovered from mice inoculated with 1,000 B. potosis eggs, and a mean of 422.0 larvae from mice inoculated with 1,000 B. transfuga eggs. The highest number of larvae was recovered from the carcasses for both B. potosis and B. transfuga. In the viscera, higher numbers of B. transfuga larvae (mean 131.8) were seen than B. potosis larvae (mean 33.1). In the brain, only 1 larva was detected in 1/6 mice inoculated with 1,000 B. potosis eggs, whereas a mean of 21 larvae was detected in mice inoculated with 1,000 B. transfuga eggs. A few larvae (range 0-1) were detected in the eyes of both mice inoculated with B. potosis or B. transfuga eggs. The result indicated that B. potosis larvae do not show a higher tendency to migrate into the brain of mice than B. transfuga larvae. However, 1 mouse inoculated with 100 eggs had 1 larva in the central nervous system and showed a serious neurological sign. This result may underline a potential risk of B. potosis to cause neural larva migrans in humans.

Parasites of the Giant Panda: A Risk Factor in the Conservation of a Species

The giant panda, with an estimated population size of 2239 in the world (in 2015), is a global symbol of wildlife conservation that is threatened by habitat loss, poor reproduction and limited resistance to some infectious diseases. Of these factors, some diseases caused by parasites are considered as the foremost threat to its conservation. However, there is surprisingly little published information on the parasites of the giant panda, most of which has been disseminated in the Chinese literature. Herein, we review all peer-reviewed publications (in English or Chinese language) and governmental documents for information on parasites of the giant pandas, with an emphasis on the intestinal nematode Baylisascaris schroederi (McIntosh, 1939) as it dominates published literature. The purpose of this chapter is to: (i) review the parasites recorded in the giant panda and describe what is known about their biology; (ii) discuss key aspects of the pathogenesis, diagnosis, treatment and control of key parasites that are reported to cause clinical problems and (iii) conclude by making some suggestions for future research. This chapter shows that we are only just 'scratching the surface' when it comes to parasites and parasitological research of the giant panda. Clearly, there needs to be a concerted research effort to support the conservation of this iconic species.

Procyonidae, Viverridae, Hyenidae, Herpestidae, Eupleridae, and Prionodontidae

This chapter covers the diseases and pathology of multiple taxonomic groups within the order Carnivora including Procyonidae several of the Feliformia carnivores. The overwhelming majority of knowledge about disease pathogenesis for these species is biased toward raccoons and concern for disease spread to humans and companion animals. Procyonids and feliform carnivores are ubiquitous in their environments and share habitat and environmental resources with other nondomestic and domestic carnivores and humans. As reservoirs for a number of important multispecies or zoonotic pathogens, surveys for pathogens that may be harbored or vectored by several of the species in this chapter, for example, raccoons (e.g., canine distemper virus, rabies, and leptospirosis) and civets (e.g., SARS coronavirus), have been active areas of investigation. Unfortunately, less research has focused on the potential effects of these pathogens on their hosts.

Beyond the raccoon roundworm: The natural history of non-raccoon Baylisascaris species in the New World

A total of 10 species of Baylisascaris, a genus of ascaridoid nematodes, occur worldwide and 6 of them occur in the New World. Most of the Baylisascaris species have a similar life cycle with carnivorous mammals or marsupials serving as definitive hosts and a smaller prey host serving as paratenic (or intermediate) hosts. However, one species in rodents is unique in that it only has one host. Considerable research has been conducted on B. procyonis, the raccoon roundworm, as it is a well-known cause of severe to fatal neurologic disease in humans and many wildlife species. However, other Baylisascaris species could cause larva migrans but research on them is limited in comparison. In addition to concerns related to the potential impacts of larva migrans on potential paratenic hosts, there are many questions about the geographic ranges, definitive and paratenic host diversity, and general ecology of these non-raccoon Baylisascaris species. Here, we provide a comprehensive review of the current knowledge of New World Baylisascaris species, including B. columnaris of skunks, B. transfuga and B. venezuelensis of bears, B. laevis of sciurids, B. devosi of gulonids, B. melis of badgers, and B. potosis of kinkajou. Discussed are what is known regarding the morphology, host range, geographic distribution, ecoepidemiology, infection dynamics in definitive and paratenic hosts, treatment, and control of these under-studied species. Also, we discuss the currently used molecular tools used to investigate this group of parasites. Because of morphologic similarities among larval stages of sympatric Baylisascaris species, these molecular tools should provide critical insight into these poorly-understood areas, especially paratenic and definitive host diversity and the possible risk these parasites pose to the health to the former group. This, paired with traditional experimental infections, morphological analysis, and field surveys will lead to a greater understanding of this interesting and important nematode genus.

Molecular characterization of Baylisascaris devosi Sprent, 1952 (Ascaridoidea, Nematoda) from Kamchatka sables

The nematodes of the genus Baylisascaris are common intestinal parasites of sables (Martes (M.) zibellina kamtschadalica Birula, 1916) on the entire territory of Kamchatka peninsula. Partial sequences of Cox I mitochondrial gene were used for molecular characterization of these nematodes, which confirmed the identification based on morphological data as B. devosi Sprent, 1952. Phylogenetic relationships of this Baylisascaris species were also inferred from the ITS rDNA and LSU rDNA sequences. SEM images were provided for taxonomically important morphological features.

Update on Baylisascariasis, a Highly Pathogenic Zoonotic Infection

Baylisascaris procyonis, the raccoon roundworm, infects a wide range of vertebrate animals, including humans, in which it causes a particularly severe type of larva migrans. It is an important cause of severe neurologic disease (neural larva migrans [NLM]) but also causes ocular disease (OLM; diffuse unilateral subacute neuroretinitis [DUSN]), visceral larva migrans (VLM), and covert/asymptomatic infections. B. procyonis is common and widespread in raccoons, and there is increasing recognition of human disease, making a clinical consideration of baylisascariasis important. This review provides an update for this disease, especially its clinical relevance and diagnosis, and summarizes the clinical cases of human NLM and VLM known to date. Most diagnosed patients have been young children less than 2 years of age, although the number of older patients diagnosed in recent years has been increasing. The recent development of recombinant antigen-based serodiagnostic assays has aided greatly in the early diagnosis of this infection. Patients recovering with fewer severe sequelae have been reported in recent years, reinforcing the current recommendation that early treatment with albendazole and corticosteroids should be initiated at the earliest suspicion of baylisascariasis. Considering the seriousness of this zoonotic infection, greater public and medical awareness is critical for the prevention and early treatment of human cases.

Prevalence of Baylisascaris Roundworm in Captive Kinkajous in Japan

Baylisascaris potosis causes larva migrans in animals. The present study evaluated the prevalence of B. potosis in captive kinkajous ( Potos flavus ) and the ability of milbemycin to treat natural infections of B. potosis in 2 female wild-caught kinkajous. In 2012, fecal samples were collected from 16 kinkajous in 6 zoological gardens and 29 imported captive kinkajous from 4 pet traders in Japan. Although all samples from zoological gardens were negative, 8 kinkajous from traders were positive for Baylisascaris eggs, at least 4 of which were wild caught in the Republic of Guyana. No associated human illness was reported from any of the facilities. The 2 infected kinkajous received a single oral administration of Milbemycin® A Tablets, which delivers 0.69-0.89 mg/kg milbemycin oxime. Fecal examinations on days 14 and 30 were negative for Baylisascaris eggs. These results demonstrated that milbemycin oxime has possible anthelmintic efficacy against Baylisascaris roundworms in captive kinkajous. We conclude that Baylisascaris infections are highly prevalent in wild-caught kinkajous in Japan and that most of the infected kinkajous were imported from the Republic of Guyana.

Larva migrans in squirrel monkeys experimentally infected with Baylisascaris potosis

Roundworms of the genus Baylisascaris are natural parasites primarily of wild carnivores, and they can occasionally cause infection in humans and animals. Infection results in visceral larva migrans and/or neural larva migrans, which can be severe or fatal in some animals. Recently, Baylisascaris nematodes isolated from kinkajous (Potos flavus) and previously referred to as Baylisascaris procyonis were renamed as Baylisascaris potosis; however, data regarding the pathogenicity of B. potosis towards animals and humans are lacking. In the present study, we experimentally infected squirrel monkeys (Saimiri sciureus) with B. potosis to determine the suitability of the monkey as a primate model. We used embryonated eggs of B. potosis at two different doses (10,000 eggs and 100,000 eggs) and examined the animals at 30 days post-infection. Histopathological examination showed the presence of B. potosis larvae and infiltration of inflammatory cells around a central B. potosis larvae in the brain, intestines, and liver. Nevertheless, the monkeys showed no clinical signs associated with infection. Parasitological examination revealed the presence of B. potosis larvae in the intestines, liver, lung, muscles, brain, kidney, and diaphragm. Our findings extend the range of species that are susceptible to B. potosis and provide evidence for the zoonotic potential of larva migrans in high dose infections.

Experimental infection of Mongolian gerbils with Baylisascaris potosis

The present study evaluated the pathogenicity of Baylisascaris potosis, a newly described ascarid nematode, in Mongolian gerbils. Gerbils were infected with varying doses of either B. potosis or Baylisascaris transfuga embryonated eggs (100, 1,000, and 4,000) for 30 days postinfection (pi). Baylisascaris potosis-infected gerbils showed no clinical signs of disease; however, gerbils exposed to 1,000 and 4,000 B. transfuga eggs showed severe neurologic signs at 22-29 days and 14-15 days pi, respectively. Histopathologic examination revealed larvae and lesions in the intestine, lung, liver, and muscles of B. potosis-infected gerbils, but not in the brain, whereas B. transfuga larvae were found only in the brain and muscle. These results indicate that B. potosis larvae migrate through numerous organs and are associated with visceral larva migrans in gerbils, but less frequently migrate to the nervous system in gerbils than does B. transfuga .