In an arms race between host and parasite, a lungworm's ability to infect a toad is determined by host susceptibility not parasite preference.

Evolutionary arms races can alter both parasite infectivity and host resistance, and it is difficult to separate the effects of these twin determinants of infection outcomes. We used a co-introduced, invasive host-parasite system (the lungworm Rhabdias pseudosphaerocephala and cane toads Rhinella marina), where rapid adaptation and dispersal have led to population differences in infection resistance. We quantified behavioural responses of parasite larvae to skin-chemical cues of toads from different invasive populations, and rates at which juvenile hosts became infected following standardized exposure to lungworms. Chemical cues from toad skin altered host-seeking behaviour by parasites, similarly among populations. The number of infection attempts (parasite larvae entering the host's body) also did not differ between populations, but rates of successful infection (establishment of adult worm in host lungs) were higher for range-edge toads than for range-core conspecifics. Thus, lower resistance to parasite infection in range-edge juvenile toads appears to be due to less effective immune defences of the host rather than differential behavioural responses of the parasite. In this ongoing host-parasite arms race, changing outcomes appear to be driven by shifts in host immunocompetence.

Wildfires modify the parasite loads of invasive cane toads.

The frequency and severity of wildfires are increasing due to anthropogenic modifications to habitats and to climate. Post-fire landscapes may advantage invasive species via multiple mechanisms, including changes to host-parasite interactions. We surveyed the incidence of endoparasitic lungworms (Rhabdias pseudosphaerocephala) in invasive cane toads (Rhinella marina) in near-coastal sites of eastern Australia, a year after extensive fires in this region. Both the prevalence of infection and number of worms in infected toads increased with toad body size in unburned areas. By contrast, parasite load decreased with toad body size in burned areas. By killing moisture-dependent free-living lungworm larvae, the intense fires may have liberated adult cane toads from a parasite that can substantially reduce the viability of its host. Smaller toads, which are restricted to moist environments, did not receive this benefit from fires.

Description, biology and molecular characterisation of Serpentirhabdias moi n. sp. (Nematoda: Rhabdiasidae) from Chironius exoletus (Serpentes: Colubridae) in Brazil.

A new species of the genus Serpentirhabdias Tkach, Kuzmin et Snyder, 2014, S. moi n. sp., is described from a colubroid snake Chironius exoletus from Caxiuanã National Forest, State of Pará, Brazil. The species is characterised by having a triangular oral opening, absence of the buccal capsule, presence of six minute onchia in the oesophastome, and excretory glands of approximately the same length as the oesophagus. These qualitative morphological characters, as well as some measurements, differentiate the new species from other Neotropical and Nearctic Serpentirhabdias spp. The morphological description of parasitic adults of S. moi n. sp. is complemented by the description of free-living stages including males, females, and infective larvae. Comparative analysis of partial sequences of cox1 and 12S mitochondrial genes strongly supported the status of S. moi n. sp. as a new species. Molecular phylogeny based on sequences of the nuclear DNA region spanning the 3' end of the 18S nuclear rRNA gene, ITS region (ITS1 + 5.8S + ITS2) and 5' end of the 28S gene supported monophyly of all rhabdiasid genera included in the analysis and placed the new species into the Serpentirhabdias clade as sister taxon to S. fuscovenosa.

Isolation and molecular characterisation of Halicephalobus gingivalis in the brain of a horse in Piedmont, Italy.

BACKGROUND: A fatal case of meningoencephalitis was reported in a 13-year-old Koninklijk Warmbloed Paard Nederland stallion, suspected of West Nile virus (WNV) infection, in the Piedmont region of Italy. Clinical signs included right head tilt and circling, depression alternated with excitability, fever and lateral strabismus. Combined treatment consisting of dimethylsulfoxide, dexamethasone, sulphonamides and sedative was administered, but because of the poor conditions the horse was euthanatized and submitted for necropsy. RESULTS: At post-mortem examination no skin lesions were observed, all organs appeared normal on gross evaluation and only head and blood samples were further investigated. Neuropathological findings consisted of granulomatous meningoencephalitis and larvae and adult females of Halicephalobus gingivalis were isolated and identified from the digested brain. Frozen brain was submitted to PCR amplification and 220 bp multiple sequence alignment was analysed by Bayesian phylogenetic analysis. CONCLUSIONS: Phylogenetic inference revealed that the isolate belongs to H. gingivalis Lineage 3. WN surveillance can help to deepen our knowledge of horse neurological disorders investigating their causes and incidence. Moreover, it can help to understand the geographic distribution of the H. gingivalis, to unravel epidemiological information, and to estimate risk for humans.

Ecological factors responsible for the geographic distribution of Rhabdias joaquinensis: where do lungworms infect anurans in nature?

The lungworm Rhabdias joaquinensis (Nematoda: Rhabdiasidae) is a common parasite of anurans in eastern Nebraska, yet absent from the same hosts in western Nebraska. This study investigated the ecology of the lungworm's free-living stages that reside in host feces and surrounding soils to establish the worm's free-living niche in eastern Nebraska. Using a comparative method, this study also investigated the absence of lungworms in western Nebraska's Sandhills. Soil composition, moisture, and temperature were experimentally varied in the laboratory to assess their effects on juvenile development and survival. Field mesocosm and host defecation experiments were used to determine where in nature lungworms survive and eventually infect frogs and toads and to discover if vegetation facilitates lungworm transmission to hosts. The results found loam soils were amenable to lungworm development, whereas soils with high clay or sand content produced few infective lungworms. Soil moisture <50 % did not support lungworm development. Infective juveniles successfully developed between 5 and 35 °C, albeit at different rates, whereas only a limited number of non-infective worms developed at 40 °C. Field studies found that shoreline environments supported lungworm development, and the majority of lungworm infections appear to occur within a zone of infection adjacent to shorelines in eastern Nebraska. The prevalence in vegetation mesocosms was 100 %, and a significantly higher mean abundance was found in toads from containers with vegetation than without. Overall, these experiments suggest that the spatial distribution of R. joaquinensis in Nebraska is constrained by the worm's ability to survive and reproduce in a soil matrix.

First report of fatal systemic Halicephalobus gingivalis infection in two Lipizzaner horses from Romania: clinical, pathological, and molecular characterization.

Halicephalobus gingivalis (H. gingivalis) causes a rare and fatal infection in horses and humans. Despite the zoonotic potential and severity of the disease, the epidemiology and pathogenesis of halicephalobiasis are still poorly understood. Several European cases of equine halicephalobiasis have been documented; however, in South-Eastern European countries, including Romania, equine neurohelminthiasis caused by H. gingivalis has not been previously described. Two Lipizzaner horses with a clinical history of progressive neurological signs were referred to the Pathology Department of the Cluj-Napoca (Romania) for necropsy. Both horses died with severe neurological signs. Gross examination and cytological, histological, and molecular analyses were performed. The stallions came from two different breeding farms. No history of traveling outside Romania was recorded. At necropsy, granulomatous and necrotizing lesions were observed in the kidneys, lymph nodes, brain, retroperitoneal adipose tissue, and lungs, indicating a systemic infection. Parasitological and histopathological analyses evidenced larval and adult forms of rhabditiform nematodes consistent with Halicephalobus species. Parasites were observed in both lymph and blood vessels of different organs and were also identified in urine samples. A subunit of the large-subunit ribosomal RNA gene (LSU rDNA) of H. gingivalis (673 bp) was amplified from lesions in both horses.To the authors' knowledge, this is the first report of equine systemic H. gingivalis infection in Romania and in South-Eastern Europe. Our findings provide new insights into the geographic distribution of specific genetic lineages of H. gingivalis, while also raising public health awareness, as the parasite is zoonotic.

The Effects of a Nematode Lungworm (Rhabdias hylae) on its Natural and Invasive Anuran Hosts.

Biological invasions can bring both the invader and native taxa into contact with novel parasites. As cane toads ( Rhinella marina ) have spread through Australia, they have encountered lungworms (Rhabdias hylae) that occur in native frogs. Field surveys suggest that these lungworms have not host-switched to toads. In our laboratory studies, R. hylae infected cane toads as readily as it infected native frogs, but failed to reach the lungs of the novel host (i.e., were killed by the toads' immune response). Plausibly, then, R. hylae might reduce the viability both of their native hosts (frogs, that can exhibit high parasite burdens) and cane toads (that must deal with infective larvae traveling through the host body). Our laboratory trials suggest, however, that the impacts of the parasite on infected anuran hosts (both frogs and toads) were minimal, with no significant decrements to host survival, activity, growth, or locomotor performance. Ironically, the lack of impact of the parasite on its native hosts appears to be an outcome of co-evolution (frogs tolerate the lungworm), whereas the lack of impact on the novel host is due to a lack of co-evolution (toads can recognize and eliminate the lungworm).

Quantifying anuran microhabitat use to infer the potential for parasite transmission between invasive cane toads and two species of Australian native frogs.

Parasites that are carried by invasive species can infect native taxa, with devastating consequences. In Australia, invading cane toads (Rhinella marina) carry lungworm parasites (Rhabdias pseudosphaerocephala) that (based on previous laboratory studies) can infect native treefrogs (Litoria caerulea and L. splendida). To assess the potential of parasite transmission from the invader to the native species (and from one infected native frog to another), we used surveys and radiotelemetry to quantify anuran microhabitat use, and proximity to other anurans, in two sites in tropical Australia. Unsurprisingly, treefrogs spent much of their time off the ground (especially by day, and in undisturbed forests) but terrestrial activity was common at night (especially in anthropogenically modified habitats). Microhabitat overlap between cane toads and frogs was generally low, except at night in disturbed areas, whereas overlap between the two frog species was high. The situations of highest overlap, and hence with the greatest danger of parasite transmission, involve aggregations of frogs within crevices by day, and use of open ground by all three anuran species at night. Overall, microhabitat divergence between toads and frogs should reduce, but not eliminate, the transmission of lungworms from invasive toads to vulnerable native frogs.

Helminth parasites of Pseudacris hypochondriaca (Anura: Hylidae) from Baja California, Mexico, with the description of two new species of nematodes.

The helminth parasite fauna of the hylid frog Pseudacris hypochondriaca in several localities along the Baja California Peninsula in northwestern Mexico is presented. The helminth fauna consists of 4 species of nematodes (Oswaldocruzia pipiens, a larval form of an Ascaridid, 2 new species belonging to the genera Rhabdias and Cosmocercoides), and 1 species of digenean ( Gorgoderina sp.). The new species of Rhabdias represents the 88th species assigned to the genus and the third species described from Mexican anurans. Also, the species of Cosmocercoides represents the 20th species assigned to the genus and the first representative of this genus described from Mexico.

Transmission, host specificity, and seasonal occurrence of Cyrtosomum penneri (Nematoda: Atractidae) in lizards from Florida.

Experimental infections and field-collected lizards were used to investigate issues of transmission, host specificity, and seasonal occurrence in the nematode Cyrtosomum penneri (Cosmocercoidea: Atractidae). Anolis sagrei (87 males, 42 females) were captured from the Florida Southern College campus, Polk County, Florida, from October 2010 to September 2011, and 8,803 C. penneri were collected from their intestines. During the breeding season all sexually mature (SVL ≥ 34 mm) A. sagrei were infected, whereas juvenile lizards (SVL <34 mm) were never infected. Experimental infections, using A. sagrei , found that worms were transferred to new hosts venereally, but not during oral exposures. Mating trials confirmed that worms were consistently transferred between hosts during copulation under natural conditions. Experimental exposures found that land snails and crickets do not serve as transport or intermediate hosts, which supports the idea that C. penneri is transferred only during host copulation. Experimental infections to test host specificity in C. penneri successfully infected A. sagrei , Hemidactylus turcicus , and Sceloporus undulatus , but not Anolis carolinensis or Plestiodon inexpectatus. Overall, this is the first study to fully elucidate the life cycle of any atractid nematode, and we suggest a venereal route of transmission for all atractid worms that infect reptilian hosts. Our findings also have implications for the host's reproductive and behavioral biology, e.g., support for covert or satellite males in the A. sagrei mating system.

Host specificity of North American Rhabdias spp. (Nematoda: Rhabdiasidae): combining field data and experimental infections with a molecular phylogeny.

Lungworms of the cosmopolitan genus Rhabdias are among the most common parasites of amphibians and squamate reptiles. The present study used experimental infections, field studies, and a molecular phylogeny to determine the host specificity of 6 Rhabdias spp. that infect snakes and anurans from North America. The molecular phylogeny suggests Rhabdias ranae from Nebraska and Mississippi may represent separate, cryptic species. In addition, the phylogeny strongly supports separate clades for anuran and snake lungworms. Field studies and experimental infections indicate that snake lungworms are generalist snake parasites; however, laboratory experiments also suggest that lizards can be infected under some environmental conditions. Lungworms from anurans were found not to infect salamanders or reptiles, in nature or in the laboratory; anuran lungworm species ranged from strict host specificity, e.g., R. ranae from Nebraska, to relative generalist, e.g., Rhabdias joaquinensis from Nebraska. Overall, host specificity for species of Rhabdias does not provide support for the evolution of progressive specialization over time. For most species of lungworms, host specificity in nature appears to be limited by both ecological and physiological factors, which vary between species and their hosts. Furthermore, some lungworms, e.g., Rhabdias bakeri from Missouri, appear to be tracking host resources instead of host phylogenies, an example of ecological fitting.

Two new species of Rhabdias (Nematoda: Rhabditida: Rhabdiasidae) in anuran hosts from Dehradun (Uttarakhand), India.

Rhabdias himalayanus n. sp. from the lungs of Duttaphrynus himalayanus and Rhabdias dehradunensis n. sp. from the lungs of Nanorana minica from Dehradun, India are described and figured. Of the 3 previously described Indian species, Rhabdias himalayanus n. sp. is most similar to Rhabdias shortii in having a cylindrical corpus, inflated cuticle, and conical tail; it differs from R. shortii in having greater body measurements, longer esophagus, larger eggs, and a different pattern of cuticle inflation at the vulva and tail region. Rhabdias dehradunensis n. sp. is most similar to Rhabdias bulbicauda in that both possess a swollen posterior end; it differs from R. bulbicauda by having a subterminal anus, a prominent tail, and a postequatorial vulva.

Pulmonary infection in two sympatric lizards, Mabuya arajara (Scincidae) and Anolis brasiliensis (Polychrotidae) from a cloud forest in Chapada do Araripe, Ceará, Northeastern Brazil / Infecção pulmonar em dois lagartos simpátricos, Mabuya arajara (Scincidae) e Anolis brasiliensis na mata-úmida da Chapada do Araripe, Ceará, Nordeste do Brasil

The parameters of infection by lung parasites from two sympatric lizards, Mabuya arajara and Anolis brasiliensis, from the Atlantic Rainforest of the lower slope of Chapada do Araripe in Northeastern Brazil were analyzed between September, 2009 and July, 2010. A total of 202 lizards were collected. 125 specimens were from Mabuya arajara and 77 from Anolis brasiliensis. M. arajara was infected by the pentastomid Raillietiella mottae while A. brasiliensis was infected by the nematode Rhabdias sp., with an overall prevalence of 1.6% and 28.6%, respectively. The mean intensity of infection by Rhabdias sp. was 3.63 ± 2.58 (range 1-15). The body size and sex of lizards did not influence the intensity of infection by Rhabdias sp. The overall prevalence was also not different between males and females hosts in A. brasiliensis. Both Anolis brasiliensis and Mabuya arajara represent a new host to Rhabdias sp. and Raillietiella mottae, respectively.

Os parâmetros de infecção por parasitas pulmonares em dois lagartos simpátricos, Mabuya arajara e Anolis brasiliensis, da floresta úmida da encosta da Chapada do Araripe, Nordeste do Brasil, foram analisados entre setembro de 2009 e julho de 2010. Um total de 202 lagartos foi coletado, sendo 125 espécimes de Mabuya arajara e 77 de Anolis brasiliensis. M. arajara estava infectado pelo pentastomídeo Raillietiella mottae, enquanto A. brasiliensis apresentava infecção pelo nematódeo Rhabdias sp., com prevalência total de 1,6% e 28,6%, respectivamente. A intensidade média de infecção por Rhabdias sp. foi 3,63 ± 2,58 (amplitude 1-15). O tamanho e o gênero dos lagartos não influenciaram a intensidade de infecção por Rhabdias sp. A prevalência também não apresentou diferença entre machos e fêmeas em A.brasiliensis. Ambos, Anolis brasiliensis e Mabuya arajara, representam novos hospedeiros para Rhabdias sp. e Raillietiella mottae, respectivamente.

Pulmonary infection in two sympatric lizards, Mabuya arajara (Scincidae) and Anolis brasiliensis (Polychrotidae) from a cloud forest in Chapada do Araripe, Ceará, Northeastern Brazil.

The parameters of infection by lung parasites from two sympatric lizards, Mabuya arajara and Anolis brasiliensis, from the Atlantic Rainforest of the lower slope of Chapada do Araripe in Northeastern Brazil were analyzed between September, 2009 and July, 2010. A total of 202 lizards were collected. 125 specimens were from Mabuya arajara and 77 from Anolis brasiliensis. M. arajara was infected by the pentastomid Raillietiella mottae while A. brasiliensis was infected by the nematode Rhabdias sp., with an overall prevalence of 1.6% and 28.6%, respectively. The mean intensity of infection by Rhabdias sp. was 3.63 ± 2.58 (range 1-15). The body size and sex of lizards did not influence the intensity of infection by Rhabdias sp. The overall prevalence was also not different between males and females hosts in A. brasiliensis. Both Anolis brasiliensis and Mabuya arajara represent a new host to Rhabdias sp. and Raillietiella mottae, respectively.

Description of a new species of Kurilonema (Nematoda: Rhabdiasidae) from lungs of the skink Sphenomorphus abdictus aquilonius (Reptilia: Squamata: Scincidae) in the Philippines.

Kurilonema browni n. sp. is described on the basis of specimens found in the lungs of the scincid lizard Sphenomorphus abdictus aquilonius from Aurora Province, Luzon Island, Philippines. The new species differs from Kurilonema markovi, the only previously known species in the genus, by the presence of 2 prominent lateral pseudolabia, larger body size, shorter tail length relative to total body length, and more numerous eggs in the uteri, containing fully developed larvae. The inner surface of the buccal capsule in the new species is densely covered with rounded scales that have not been observed in K. markovi or any other rhabdiasid species. This is the first record of the genus from the Philippines.

European earwig (Forficula auricularia) as a novel host for the entomopathogenic nematode Steinernema carpocapsae.

The natural history of many entomopathogenic nematode species remains unknown, despite their wide commercial availability as biological control agents. The ambushing entomopathogenic nematode, Steinernema carpocapsae, and the introduced European earwig, Forficula auricularia, forage on the soil surface. Since they likely encounter one another in nature, we hypothesized that earwigs are susceptible to nematode infection. In the laboratory, the LC(50) for F. auricularia was 226 S. carpocapsae/earwig and the reproductive potential was 123.5 infective juvenile nematodes/mg tissue. This susceptibility depended on host body size with significantly higher mortality rates seen in larger earwigs. In a study of host recognition behavior, S. carpocapsae infective juveniles responded to earwig cuticle as strongly as they did to Galleria mellonella cuticle. We also found that earwigs exposed to S. carpocapsae cleaned and scratched their front, middle and back legs significantly more than controls. Coupled with previous field data, these findings lead us to suggest that F. auricularia may be a potential host for S. carpocapsae.

Infection dynamics of the lungworm Rhabdias pseudosphaerocephala in its natural host, the cane toad (Bufo marinus), and in novel hosts (native Australian frogs).

Host-parasite systems have often evolved over time, such that infection dynamics may become greatly modified from the time of initial contact of the host with the parasite. Biological invasions may be useful to clarify processes in the initial contact of hosts with parasites, and allow us to compare parasite uptake between the ancestral (coevolved) host and novel (noncoevolved) hosts. Cane toads (Bufo marinus) are spreading rapidly through tropical Australia, carrying with them a nematode lungworm (Rhabdias pseudosphaerocephala) congeneric with those found in Australian frogs. We investigated the dynamics of infections of the toad parasite by conducting histologic examinations of cane toads and three native Australian frogs (Litoria dahlii, Litoria nasuta, and Opisthodon ornatus) at 2, 6, and 10 days after experimental exposure to the toad lungworm. More worms were found in toads than in frogs, especially at longer periods postexposure. In toads, the infective larvae entered the skin and muscles within 2 days postexposure, passed into the coelom in 6 days, and reached the lungs at 10 days. In frogs, larvae were found in many organs rather than migrating to consistent target tissues; a few larvae reached the lungs of L. dahlii. Migratory larvae caused increasing inflammation (primarily granulomatous admixed with granulocytes then lymphocytes) through time, especially in frogs. Evolution has resulted in an enhanced ability of the lungworm to locate the target organ (the lungs) of the toad, and an increase in rates of parasite survival within this host.

Patterns of infection by lungworms, Rhabdias ranae and Haematoloechus spp., in northern leopard frogs: a relationship between sex and parasitism.

We examined a population of northern leopard frogs to determine whether sex biases in investment in immunity, previously reported for this host species under controlled exposures to lung nematodes, is predictive of patterns of parasitism in nature. We examined Rhabdias ranae and Haematoloechus spp. infections in 74 breeding adult, 28 non-breeding adult, and 53 juvenile frogs. Contrary to our predictions, R. ranae prevalence and mean abundance were higher in breeding female frogs (prevalence: 39.4%, abundance: 3.05 +/- 0.85) than on breeding males (prevalence: 26.0%, abundance: 1.17 +/- 0.52), although no sex bias was observed among non-breeding adults or juvenile frogs. Female frogs also carried larger R. ranae worms, on average, than did males (females: 6407.38 microm +/- 153.80; males: 5198 microm +/- 131.09), regardless of age or breeding condition. We observed no sex-linked patterns of parasitism by Haematoloechus spp. worms in either adult or juvenile frogs. Alternative hypotheses, such as differences among sexes in the selection of thermal clines for hibernation, may explain the observed female bias in parasitism by nematode lungworms in nature and, thus, need to be considered.

Diversity and distribution of entomopathogenic nematodes (Nematoda: Steinernematidae, Heterorhabditidae) and their bacterial symbionts (gamma-Proteobacteria: Enterobacteriaceae) in Jordan.

Until now, only a few systematic surveys of entomopathogenic nematodes (EPN) have been conducted in Middle Eastern countries. Many of the recovered EPN species in this region have shown to own distinctive qualities that enable their survival in unique environments, such as high temperatures and low moisture levels tolerance. These new species and strains, with unique environmental tolerances, are more suitable for their consideration in pest management programs in xerophytic regions. With this background in mind, we recently conducted a survey of EPN in Jordan. This study records for the first time the diversity and distribution of these nematodes and their bacterial symbionts in this country. Jordan's three geographic regions: (1) the highlands, (2) Jordan valley and (3) the desert region were sampled. Within each region, natural habitats and agricultural regions characteristic to each region were considered for sampling purposes. Four EPN species including three Steinernema and one Heterorhabditis were recovered. Nematodes were identified using a combination of molecular markers and classic morphological diagnostic tools. Bacterial symbionts were identified by analysis of 16S rRNA sequences. Abiotic characteristics such as soil type, soil pH, and elevation were also recorded. We herein report the diversity of EPN species in Jordan and discuss their potential in Biocontrol and IPM programs for this country.