Validity of genus Perostrongylus Schlegel, 1934 with new data on Perostrongylus falciformis (Schlegel, 1933) in European badgers, Meles meles (Linnaeus, 1758): distribution, life-cycle and pathology

Comparative biology of parasitic nematodes in the genus Angiostrongylus and related genera

The rise to prominence of some Angiostrongylus species through associated emerging disease in humans and dogs has stimulated calls for a renewed focus on the biology of this genus and three related genera. Although significant research efforts have been made in recent years these have tended to focus on individual species and specific aspects such as diagnosis and treatment of disease or new records of occurrence and hosts. This comprehensive review takes a comparative approach, seeking commonalities and differences among species and asking such questions as: Which species belong to this and to closely related genera and how are they related? Why do only some species appear to be spreading geographically and what factors might underlie range expansion? Which animal species are involved in the life cycles as definitive, intermediate, paratenic and accidental hosts? How do parasite larvae find, infect and develop within these hosts? What are the consequences of infection for host health? How will climate change affect future spread and global health? Appreciating how species resemble and differ from each other shines a spotlight on knowledge gaps and provides provisional guidance on key species characteristics warranting detailed study. Similarities exist among species, including the basic life cycle and transmission processes, but important details such as host range, climatic requirements, migration patterns within hosts and disease mechanisms differ, with much more information available for A. cantonensis and A. vasorum than for other species. Nonetheless, comparison across Angiostrongylus reveals some common patterns. Historically narrow definitive host ranges are expanding with new knowledge, combining with very broad ranges of intermediate gastropod hosts and vertebrate and invertebrate paratenic and accidental hosts to provide the backdrop to complex interactions among climate, ecology and transmission that remain only partly understood, even for the species of dominant concern. Key outstanding questions concern larval dynamics and the potential for transmission outside trophic relations, relations between infection and disease severity in different hosts, and how global change is altering transmission beyond immediate impacts on development rate in gastropods. The concept of encounter and compatibility filters could help to explain differences in the relative importance of different gastropod species as intermediate hosts and determine the importance of host community composition and related environmental factors to transmission and range. Across the group, it remains unclear what, physiologically, immunologically or taxonomically, delimits definitive, accidental and paratenic hosts. Impacts of infection on definitive host fitness and consequences for population dynamics and transmission remain mostly unexplored across the genus. Continual updating and cross-referencing across species of Angiostrongylus and related genera is important to synthesise rapid advances in understanding of key traits and behaviours, especially in important Angiostrongylus species that are emerging causative agents of disease in humans and other animals.

Molecular phylogeny of the Pseudaliidae (Nematoda) and the origin of associations between lungworms and marine mammals

Metastrongyloid lungworms from the family Pseudaliidae infect the lungs and cranial sinuses of cetaceans worldwide, except Stenuroides herpestis, which exhibits a striking terrestrial association with the Egyptian mongoose, Herpestes ichneumon. Previous phylogenies of the Metastrongyloidea that included some (2-7) marine species of the Pseudaliidae confirmed that these species are closely related, but also grouped species of Parafilaroides (family Filaroididae) between the members of the Pseudaliidae. In this study we extracted DNA from representatives of all six genera of the Pseudaliidae and amplified the second internal transcribed spacer (ITS2) and cytochrome c oxidase subunit I (cox1) genes in order to investigate the concept of the Pseudaliidae as a monophyletic unit. Three species of Parafilaroides were also included in the analysis. Maximum Likelihood and Bayesian Inference analyses of the concatenated genes resulted in a well-supported clade including the marine pseudaliids, S. herpestis and Parafilaroides spp. These findings validate the status of S. herpestis as a pseudaliid species and support the inclusion of Parafilaroides in the Pseudaliidae. Although males of Parafilaroides spp. lack a copulatory bursa, this trait itself is highly variable in the Pseudaliidae, which include abursate species. Furthermore, life cycles seem to be closely similar between both taxa. When all the available phylogenetic data on the Metastrongyloidea were mapped of onto a phylogeny of the Laurasiatheria, there was a strong suggestion that the Pseudaliidae may have descended from ancestors infecting terrestrial carnivores, with odontocetes being colonized in the marine realm as a result of a host-switching event from pinnipeds through shared fish prey. The origin of the association between S. herpestis and mongooses remains uncertain.

Habitat Characteristics as Potential Drivers of the Angiostrongylus daskalovi Infection in European Badger (Meles meles) Populations

From 2016 to 2020, an investigation was carried out to identify the rate of Angiostrongylus spp. infections in European badgers in Hungary. During the study, the hearts and lungs of 50 animals were dissected in order to collect adult worms, the morphometrical characteristics of which were used for species identification. PCR amplification and an 18S rDNA-sequencing analysis were also carried out. Global and local spatial autocorrelation methods were used to detect high-rated and low-rated infected animal clusters. We conducted a binary logistic regression analysis along with hierarchical agglomerative clustering to determine the relation between selected biotic and abiotic variables, and the prevalence of an A. daskalovi infection. We found a high prevalence (72%) and moderate mean intensity (14.1) of Angiostrongylus sp. infection. Morphology and sequencing revealed that all animals were infected by A. daskalovi. The results of both spatial autocorrelations suggested that the spatial distribution of infected badgers was more spatially clustered than random. The results of an analysis of the correlation between habitat characteristics and infection showed that the infected animals could be associated with dry and open landscape habitats without extended and connected canopy. It is suggested that the territorial behaviour of badgers and the landscape-directed aggregation of potential intermediate hosts might be the drivers of an A. daskalovi infection.

DNA Footprints: Using Parasites to Detect Elusive Animals, Proof of Principle in Hedgehogs

Simple Summary

Nocturnal and elusive animals are notoriously difficult to count—hedgehogs being a prime example. Therefore, any reliable way to demonstrate the presence of a particular animal, within a given area, would be a valuable addition to many ecologists’ tool kits. The proposed method is based upon the idea that you can find a parasite, specific to a vertebrate animal of interest that has a life stage within an invertebrate host. Molecular detection of these parasites is then carried out in the more abundant and easily collected invertebrate intermediate host. The key to this proposed method is the specificity of the parasite to the vertebrate animal and its detection in the invertebrate intermediate hosts. Crenosoma striatum is specific to hedgehogs and was chosen as the parasite to develop the molecular survey tool for hedgehogs, an elusive nocturnal species of considerable interest at present. Results revealed the presence of the nematode only at a site known to be inhabited by hedgehogs confirming the potential of this method to improve the accuracy of recording hedgehog populations.

Abstract

The Western European Hedgehog (Erinaceous europaeus) is a nocturnal animal that is in decline in much of Europe, but the monitoring of this species is subjective, prone to error, and an inadequate basis for estimating population trends. Here, we report the use of Crenosoma striatum, a parasitic nematode specific to hedgehogs as definitive hosts, to detect hedgehog presence in the natural environment. This is achieved through collecting and sampling the parasites within their intermediate hosts, gastropoda, a group much simpler to locate and sample in both urban and rural habitats. C. striatum and Crenosoma vulpis were collected post-mortem from the lungs of hedgehogs and foxes, respectively. Slugs were collected in two sessions, during spring and autumn, from Skomer Island (n = 21), which is known to be free of hedgehogs (and foxes); and Pennard, Swansea (n = 42), known to have a healthy hedgehog population. The second internal transcribed spacer of parasite ribosomal DNA was used to develop a highly specific, novel, PCR based multiplex assay. Crenosoma striatum was found only at the site known to be inhabited by hedgehogs, at an average prevalence in gastropods of 10% in spring and autumn. The molecular test was highly specific: One mollusc was positive for both C. striatum and C. vulpis, and differentiation between the two nematode species was clear. This study demonstrates proof of principle for using detection of specific parasite DNA in easily sampled intermediate hosts to confirm the presence of an elusive nocturnal definitive host species. The approach has great potential as an adaptable, objective tool to supplement and support existing ecological survey methods.

Identification and epidemiological analysis of Perostrongylus falciformis infestation in Irish badgers

Background

The lungworm, Perostrongylus falciformis (fomerly known as Aelurostrongylus falciformis) has been identified in badgers (Meles meles) in Britain, the Russian Federation, Italy, Norway, Poland, Ukraine, Bosnia Herzegovina and Romania, while Aelurostrongylus pridhami has been reported from badgers in Spain.

Results

Pulmonary tissue from 1580 Irish badgers was examined and an estimated prevalence of 32.09% (95% CI: 29.79–34.45%) of this parasite was detected. Confirmation of its occurrence was made by PCR analysis on a subset of the population.

Conclusion

Infestation was widely distributed throughout the Republic of Ireland, with a trend towards higher infestation risk in western versus eastern counties. In addition males were at a higher risk of infestation than females and juveniles were at a significantly higher risk than adult badgers.