Filariasis of parti-colored bats: phylogenetic analysis, infection prevalence, and possible vector mite identification

Abstract

Introduction: The epidemiology of filarial infections is a neglected area of bat research, with little information on filarial species diversity, life cycles, host ranges, infection prevalence and intensity, parasite pathogenicity, or competent vectors. Furthermore, molecular data for filarial worms are largely lacking.

Methods: Here, we examined 27 cadavers of parti-colored bat (Vespertilio murinus) from Czech rescue centers for filarial infection using gross necropsy. We also used nested polymerase chain reactions targeting partial mitochondrial cytochrome c oxidase subunit I (COI) partial gene to detect and genotype filarial parasites within organs, and ectoparasites of V. murinus from Russian and Slovak summer bat colonies. Samples with mixed filarial infections were cloned to extract separate sequences. The COI gene sequences were then subjected to phylogenetic analysis and a phylogenetic tree constructed. Adult filarial worms were also screened for the bacterial symbiont Wolbachia, using a standard PCR targeting the partial 16S rRNA gene.

Results: Two filarial nematode species were identified in single and mixed V. murinus infections, Litomosa sp. and a species of Onchocercidae. Adult Litomosa sp. nematodes were only recorded during necropsy of the abdominal, thoracic, and gravid uterine cavities of four bats. Molecular screening of organs for filarial DNA revealed prevalences of 81.5, 51.9 and 48.1% in Litomosa sp., Onchocercid sp. and co-infected bats, respectively. Adult Litomosa sp. worms proved negative for Wolbachia. The macronyssid mite Steatonyssus spinosus, collected in western Siberia (Russia), tested positive for Onchocercid sp. and mixed microfilarial infection.

Discussion: Our results revealed high prevalence, extensive geographic distribution and a potential vector of filarial infection in V. murinus. Our data represent an important contribution to the field of bat parasitology and indicate the need for a taxonomic revision of bat-infecting filarial nematodes based on both morphological and molecular methods.

Keywords: Litomosa; Steatonyssus spinosus mite; Vespertilio murinus; Wolbachia; onchocercid filarial nematode; vector-borne parasites.

Figure 1

Schematic representation of a maximum likelihood phylogenetic tree based on the cytochrome oxidase c subunit I (COI) gene sequences of genera closely related to Litomosa and Litomosoides spp. (A) with detailed phylogeny of part of Litomosa spp., Litomosoides spp. and related clade containing Onchocercidae sp. (B). The final length of the alignment was 638 bp and contained 182 sequences (27 originating from this study). The tree was constructed using the evolution model TIM3 + F + I + G4. Three sequences of Breinlia robertsi used as an outgroup are not shown. Sequences from this study are marked in bold and clones originating from the same sample are shown in matching colors (red or green). The scale bar indicates the number of nucleotide substitutions per site. Sequences are labeled with accession number, species, host and country of origin (where available). Bootstrap values (SH-aLRT/UFB) above the 80/95 threshold are also displayed.