Phylogeography of Simulium Subgenus Wilhelmia (Diptera: Simuliidae)-Insights From Balkan Populations

First report of filarial nematodes in the genus Onchocerca infecting black flies (Diptera: Simuliidae) in Iran

Black flies are blood-sucking insects of public health importance, and they are effective vectors of pathogens and parasites, such as filarial nematodes of the genus Onchocerca. Our previous surveys have shown that individuals of Simulium turgaicum are annoying pests of humans and livestock in the Aras River Basin of Iran. In the present study, adult black flies of S. turgaicum were trapped from different ecotopes of five villages in Khoda-Afarin County, Iran. By using a sensitive nested PCR assay and targeting the nuclear 18S rDNA-ITS1 marker, filarial infections were found in 38 (1.89%) of 2005 black flies. Homology exploration of 360 bp of the sequences indicated that the filarial worms are members of the family Onchocercidae, with maximum alignment scores of 93-95%. Phylogenetic analysis showed that two Iranian Onchocerca isolates were clustered in the O. fasciata-O. volvulus lineage and were well separated from other filarial nematodes. Both the entomological evidence (empty abdomen of the specimens) and climatologic data (adequate accumulated degree days for development) suggest that the filarial DNA was probably that of infective larvae of vertebrates. This is the first report of an infection by Onchocerca species in S. turgaicum and the first record of onchocercids in black flies in Iran; however, more research is required to demonstrate transmission of these filarial worms by black flies in nature.

The Palearctic blackfly Simulium equinum (Diptera: Simuliidae) as a biting pest of captive nyala antelopes (Tragelaphus angasii)

Blackflies (Diptera: Simuliidae) are cosmopolitan nuisance pests of great economic importance as well as vectors of many pathogens. After reports of massive blackfly biting of captive nyala antelopes in the Vienna Zoo, Austria, this study aimed to identify the species causing multiple skin lesions on the antelope hosts. The Palearctic species Simulium equinum, belonging to the medically and veterinary important Wilhelmia subgenus, was identified as the most likely causative agent. Barcoding and maximum likelihood analysis supported morphological species identification and highlighted the complex phylogeny of the subgenus Wilhelmia. Our study gives first evidence of the multi-host feeding blackfly S. equinum in the Vienna Zoo, thereby raising the question whether other hosts could also be bitten on a regular basis. The preliminary results urge for further analysis of blackfly breeding sites as well as the clarification of the host spectrum to assess the medical and veterinary importance of blackflies in the Zoo.

Molecular detection of Dirofilaria spp. and host blood-meal identification in the Simulium turgaicum complex (Diptera: Simuliidae) in the Aras River Basin, northwestern Iran

Background

Blackflies (Diptera: Simuliidae) are known as effective vectors of human and animal pathogens, worldwide. We have already indicated that some individuals in the Simulium turgaicum complex are annoying pests of humans and livestock in the Aras River Basin, Iran. However, there is no evidence of host preference and their possible vectorial role in the region. This study was conducted to capture the S. turgaicum (s.l.), to identify their host blood-meals, and to examine their potential involvement in the circulation of zoonotic microfilariae in the study areas.

Methods

Adult blackflies of the S. turgaicum complex were bimonthly trapped with insect net in four ecotopes (humans/animals outdoors, irrigation canals, lands along the river, as well as rice and alfalfa farms) of ten villages (Gholibaiglou, Gungormaz, Hamrahlou, Hasanlou, Khetay, Khomarlou, Larijan, Mohammad Salehlou, Parvizkhanlou and Qarloujeh) of the Aras River Basin. A highly sensitive and specific nested PCR assay was used for detection of filarial nematodes in S. turgaicum (s.l.), using nuclear 18S rDNA-ITS1 markers. The sources of blood meals of engorged specimens were determined using multiplex and conventional cytb PCR assays.

Results

A total of 2754 females of S. turgaicum (s.l.) were collected. The DNA of filarial parasites was detected in 6 (0.62%) of 960 randomly examined individuals. Sequence analysis of 420 base pairs of 18S rDNA-ITS1 genes identified Dirofilaria spp. including 5 D. immitis and 1 D. repens. Importantly, all filarial positive specimens have been captured from humans and animals outdoors. Cytb-PCR assays showed that in all ecotypes studied, members of the S. turgaicum complex had preferably fed on humans, dogs, bovids, and birds, respectively.

Conclusions

To the best of our knowledge, this is the first report of D. immitis/D. repens detection in blackflies. Results showed that S. turgaicum (s.l.) was the most abundant (97%) and anthropophilic (45%) blackfly in all studied ecotypes/villages and that DNA of Dirofilaria spp. was detected in the flies taken from six villages. Dirofilariasis is a common zoonosis between humans and carnivores, with mosquitoes (Culicidae) as the principal vectors. Further investigations are needed to demonstrate that blackflies are actual vectors of Dirofilaria in the studied region.

Black flies (Diptera: Simuliidae) of the Aras River Basin: Species composition and floral visitation

Black flies are insects of medical, veterinary, and environmental significance. Historically, they have attacked humans and caused simuliotoxicosis in livestock in the Aras River Basin in northwest Iran. However, information on the species and their bionomics is limited in the region. Adult flies were collected from diverse ecotopes of the Aras River Basin. After morphological identification, representative specimens of each morphological group were subjected to mtDNA COI gene sequence analysis for species diagnosis and to infer relationships. Flies also were examined for pollinia. A total of 1880 specimens representing 12 morphotaxa in two genera (Simulium and Metacnephia) were identified: Simulium turgaicum (n=1834), S. kiritshenkoi (n=12), S. bezzii (n=7), S. brevitarse (n=7), S. pseudequinum (n=5), S. aureum species group (n=4), S. vernum species group (n=3), S. transcaspicum (n=1), three unidentified species of the subgenus Simulium (n=5), and Metacnephia possibly persica (n=2). Fifty two haplotypes were detected for the 65 COI sequences analyzed. Intraspecific genetic divergence was 0.19-8.83%, whereas the mean interspecific genetic distances among the morphotaxa were 1.41-19.58%. Molecular analyses recovered three well-supported lineages within S. turgaicum. One lineage included black flies collected from agricultural fields, a second lineage involved black flies captured from animals, and a third lineage included specimens that had visited flowers, as evidenced by presence of pollinia. The relative abundance (97%) and observations of the S. turgaicum complex biting humans are important epidemiological factors. Future studies are needed to define the potential epidemiological risk of simulids in Khoda-Afarin County of Iran.

Simulium reptans (Linnaeus, 1758) and Simulium reptantoides Carlsson, 1962 from the Balkan Peninsula

Simulium reptans (Linnaeus, 1758) and Simulium reptantoides Carlsson, 1962 are two species of the Simulium reptans group whose distribution is unclear because of their confusing taxonomy and systematics. Their genetic variability is well known for populations in northern and central Europe and shows that both species have two forms; however, the genetic variability of these species in southern and eastern Europe is unknown. To identify the status of these two species in southeast Europe, mtDNA was extracted from 19 individuals from 12 localities across the Balkan Peninsula. Phylogenetic analysis confirmed the existence of two species with 7.38-7.94% divergence. Each species was comprised of two clades, with 2.31% and 1.43% interclade divergence for S. reptans and S. reptantoides, respectively. This study revealed the presence of both species across the Balkans and that S. reptans occurs in this area in only one form (S. reptans B), while S. reptantoides is found in two genetic forms (A and B).