Circulation of Dirofilaria repens and Dirofilaria immitis in Moldova
Tatiana Șuleșco1, Heidrun von Thien2, Lidia Toderaș1
1Institute of Zoology, Academy of Sciences of Moldova, Chisinau, Moldova.
Background:
Over the last two decades, a significant spread of dirofilariasis has been observed in eastern and central Europe. However, data on the circulation of Dirofilaria spp. in Moldova were absent although direct neighbor states reported high incidence rates of human dirofilariasis.
Methods:
Daily mean temperature data were used to calculate Dirofilaria spp. development units, which were used to estimate the potential for complete extrinsic development in the mosquitoes (= sum of potential Dirofilaria spp. transmission days). In addition, 4,481 adult female mosquitoes were collected from 25 trapping sites. From 2010 to 2015, sampling was conducted with Centers for Disease Control miniature light traps, indoor resting mosquito collections as well as human landing catches in urban, rural and natural areas. Mosquitoes were analyzed for the presence of D. repens and D. immitis DNA using a duplex real-time PCR assay targeting nucleotide differences within the cytochrome c oxidase subunit 1 (D. repens) and 16S rRNA gene fragment (D. immitis).
Results:
The average of the yearly sum of potential Dirofilaria spp. transmission days between 2010 and 2015 ranged from 90 to 140 days with an increasing gradient from the North to the South of Moldova. Positive mosquito pools for D. repens were found countrywide at 13 of the 25 trapping sites and in 17 of the 22 screened mosquito taxa (26.51% of all 347 tested pools), while D. immitis was detected only at 4 of the trapping sites (Center and South) in 4 different mosquito species (8.65% of all 347 tested pools). Highest infection rates (EIR) per 100 specimens for both Dirofilaria species were found in An. maculipennis (s.l.) (D. repens: EIR = 4.91; D. immitis: EIR = 2.01), whereas the most frequent mosquito taxon Cx. pipiens (s.l.)/torrentium had significantly lower infections rates (D. repens: EIR = 0.88; D. immitis: EIR = 0.47).
Conclusions:
The temperature conditions in Moldova are suitable for transmission of Dirofilaria spp. within the entire country, which is supported by a wide distribution of Dirofilaria spp.-positive mosquitoes with high infection rates. The low number of reported human cases most likely does not reflect the current epidemiological situation of dirofilariasis in Moldova.
Insights
Dirofilaria parasites are circulating widely in Moldova
Area of Science:
- Veterinary parasitology
- Medical entomology
- Epidemiology
Background:
- Dirofilariasis is spreading in Eastern and Central Europe.
- No previous data on Dirofilaria spp. circulation in Moldova existed.
- Neighboring countries report high human dirofilariasis incidence.
Purpose of the Study:
- Assess Dirofilaria spp. circulation in Moldova.
- Determine the potential for Dirofilaria spp. transmission.
- Identify mosquito vectors and their infection rates.
Main Methods:
- Calculated Dirofilaria spp. development units using daily mean temperatures.
- Collected 4,481 adult female mosquitoes from 25 sites (2010-2015).
- Used duplex real-time PCR to detect D. repens and D. immitis DNA in mosquitoes.
Main Results:
- Potential transmission days ranged from 90-140 annually, increasing Southward.
- D. repens found countrywide in 13/25 sites and 17/22 mosquito taxa.
- D. immitis detected in 4 sites (Center/South) and 4 mosquito species.
- An. maculipennis (s.l.) showed highest infection rates for both species.
Conclusions:
- Moldova's climate supports Dirofilaria spp. transmission nationwide.
- Widespread infected mosquitoes indicate a significant transmission potential.
- Reported human cases likely underestimate the true dirofilariasis prevalence.
