Population dynamics, pathogen detection and insecticide resistance of mosquito and sand fly in refugee camps, Greece

Abstract

Background: As of 2015 thousands of refugees are being hosted in temporary refugee camps in Greece. Displaced populations, travelling and living under poor conditions with limited access to healthcare are at a high risk of exposure to vector borne disease (VBD). This study sought to evaluate the risk for VBD transmission within refugee camps in Greece by analyzing the mosquito and sand fly populations present, in light of designing effective and efficient context specific vector and disease control programs.

Methods: A vector/pathogen surveillance network targeting mosquitoes and sand flies was deployed in four temporary refugee camps in Greece. Sample collections were conducted bi-weekly during June-September 2017 with the use of Centers for Disease Control (CDC) light traps and oviposition traps. Using conventional and molecular diagnostic tools we investigated the mosquito/sand fly species composition, population dynamics, pathogen infection rates, and insecticide resistance status in the major vector species.

Results: Important disease vectors including Anopheles sacharovi, Culex pipiens, Aedes albopictus and the Leishmania vectors Phlebotomus neglectus, P. perfiliewi and P. tobbi were recorded in the study refugee camps. No mosquito pathogens (Plasmodium parasites, flaviviruses) were detected in the analysed samples yet high sand fly Leishmania infection rates are reported. Culex pipiens mosquitoes displayed relatively high knock down resistance (kdr) mutation allelic frequencies (ranging from 41.0 to 63.3%) while kdr mutations were also detected in Ae. albopictus populations, but not in Anopheles and sand fly specimens. No diflubenzuron (DFB) mutations were detected in any of the mosquito species analysed.

Conclusions: Important disease vectors and pathogens in vectors (Leishmania spp.) were recorded in the refugee camps indicating a situational risk factor for disease transmission. The Cx. pipiens and Ae. albopictus kdr mutation frequencies recorded pose a potential threat against the effectiveness of pyrethroid insecticides in these settings. In contrast, pyrethroids appear suitable for the control of Anopheles mosquitoes and sand flies and DFB for Cx. pipiens and Ae. albopictus larvicide applications. Targeted actions ensuring adequate living conditions and the establishment of integrated vector-borne disease surveillance programs in refugee settlements are essential for protecting refugee populations against VBDs.

Keywords: Insecticide resistance; Mosquito; Refugee camp; Sand fly.

Fig. 1

Vector composition and vector borne pathogen detection in Refugee camps, Greece In each refugee camp site - 2 chart pies are depicted. From left to right (in each site); Sand fly species composition chart pie, followed by Mosquito species composition chart pie. Sand fly species data displayed corresponds to male and female⁽*⁾ adult collections, mosquito species data corresponds to adult female collections (under representation of Aedes albopictus specimens/egg collections not included). Mosquito and sand fly species recorded are depicted with different colours. The size of each chart pie correlates to the number of sand flies (♂/♀) and mosquitoes (♀) collected in each site. Absence/presence of mosquito and sand fly pathogens⁽**⁾ is depicted with different symbols. Coloured symbols denote infection presence/detection, white colour denotes absence, in the analysed samples. Camp descriptors including shelter type, access status and number of occupants are displayed for the year 2017 [22]. ⁽*⁾The female sand fly specimens identification and ⁽**⁾Leishmania detection was conducted in [21]

Fig. 2

Mosquito and sand fly (genus level) population dynamics in Refugee camps, Greece. Sand fly species data displayed corresponds to male and female adult collections, mosquito species data corresponds to adult female collections. The mosquito and sand fly genera recorded are depicted with different colours. ⁽*⁾ one sample collection was conducted in September (Week 1–2) (vs) two sample collections (Week 1–2, Week 3–4) in June, July, August