Diversity of filariae circulating in South Caucasian bats and their ectoparasites

Abstract

Recent research on chiropteran parasites suggests a high prevalence and diversity, and extensive spatial distribution of filarial species; however, ecological and phylogenetic studies are still in their infancy. We sampled blood from 78 bat specimens, collected 1181 ectoparasites at summer colonies in Armenia and Georgia, and used nested-PCR targeting the cytochrome c oxidase subunit 1 (cox1) gene to detect and genotype filarial parasites. The overall prevalence of filarial DNA was 17.9% in blood samples from Myotis blythii, Myotis emarginatus, Miniopterus schreibersii, and Rhinolophus ferrumequinum, and 8.5% in ectoparasites, including two mite species (Eyndhovenia euryalis and Spinturnix myoti) and two bat flies (Nycteribia kolenatii and Penicillidia dufouri). The prevalence of microfilarial infection was significantly higher in mite samples (13.8%) than in bat fly samples (4.1%). Bats with ectoparasites positive for filarial DNA had a significantly higher total number of ectoparasites. Phylogenetic analysis placed the 18 sequences obtained into different closely related clades of onchocercid nematodes, with four different species recorded: two belonging to the genus Litomosa and two to a newly observed genus of the family Onchocercidae. Additionally, two new species of these parasites, one Litomosa sp. and one Onchocercid sp., were genetically recognised. As predicted, the diversity of filarial parasites reflects the diversity of bat hosts in the Caucasus. Extending the sampling effort to more Caucasian bat species will likely reveal previously unknown filarial species. Non-lethal and non-invasive sampling of blood and ectoparasites for molecular screening proved effective for gaining insights into parasite diversity and phylogenetic relationships of bat-infecting filarial nematodes.

Keywords: Bat blood parasites; Bat flies; Bat mites; Filarioidea; Nematodes; Onchocercidae; Vector-borne parasites; cox1.

Graphical abstract

Fig. 1

Schematic representation of a maximum likelihood phylogenetic tree based on the cox1 gene sequences of genera closely related to Litomosa spp. (A) and detailed phylogeny of Litomosa spp., Litomosoides spp., and closely related Onchocercidae spp. (B). The final length of the alignment was 1653 bp and contained 138 sequences, 18 of which were generated in this study. The tree was constructed using the evolution model TN+F+I+G4. Two sequences of Acanthocheilonema viteae were used as the outgroup. Sequences from this study are marked in bold and blue. The scale-bar indicates the number of nucleotide substitutions per site. Bootstrap values (SH-aLRT/UFB) above the 80/95 threshold are displayed. Sequences are labelled by accession number, species, host, and country of origin, if available.

Fig. 2

Bipartite bat-ectoparasite quantitative network. The size of the black bars on the left is proportional to the number of ectoparasite species found on a given bat species. The value of “n” on the left indicates the number of bats of that species examined. The size of the grey bars on the right is proportional to the abundance (number of individuals) of ectoparasites per species observed. The value of “n” on the right represents the number of ectoparasites/number of pooled samples. The width of the coloured lines/bars indicates the abundance of ectoparasites found on a given bat species.

Fig. 3

Bipartite ectoparasite-filariae quantitative network. The size of the grey bars on the left is proportional to the number of filarial species found in a given ectoparasite species. The number “n” on the left is the number of positive pooled ectoparasite samples for a given ectoparasite species. The size of the black bars on the right is proportional to the number of ectoparasite samples positive for filariae of that species. The value of “n” on the right indicates the number of pooled ectoparasite samples testing positive for a given filarial species. The width of the coloured bars indicates the abundance of filariae found for a given ectoparasite species.