Inventory, Biology and Ecology of Culicidae (Diptera) of Setif region and control tests using plant extracts

Abstract

The members of the family Culicidae, commonly known as mosquitoes, are Diptera insects widely studied. Researchers in various fields have considered mosquitoes as a focal biological material to study because they carry and spread disease to both humans and animals. Mosquito vectors are species of the family Culicidae often involved in the transmission of many deadly and dangerous diseases like malaria, dengue, chikungunya, yellow fever, West Nile virus, Zika…etc. In the last decades, Algeria has experienced outbreaks related to mosquitoes; additionally, it is exposed at the present to the installation of the invasive species Aedes albopictus (Skuse 1894). However, the mosquito biodiversity in Algeria is poorly studied, likewise, information about density and distribution patterns of mosquito populations is missed and the inventories were depended only on morphological identification. In this context, we performed a mosquito inventory in the Setif region (Algerian high plains) from 2016 to 2019, in order to provide the list of mosquito species in the study area and analyze their biodiversity, density and species distribution across two climate zones (Mediterranean Csa and steppe BSk Zones) using different statistical tests. The identification of species was done using a combination of morphological (diagnostic keys) and molecular (PCR-RFLP analysis of Cytochrome c Oxidase subunit 1 gene) approaches. The sampling yielded the identification of nine mosquito species including the malaria vectors Anopheles labranchiae (Falleroni 1926) (4.4%) and An cinereus hispaniola (Theobald 1901) (0.5%). The COI sequences of six species are provided (Accession numbers MK047302- MK047315). From the total sampled mosquitoes, Culex pipiens s.l (Linnaeus 1758) was the predominant (46.9 %) and the most frequent species (ƒ=61%) while Culiseta longiareolata (Macquart 1838) showed the highest density (51.2±63.7). Further, we have revealed a high and positive correlation between Cx. theileri (Theobald 1903) and An labranchiae (rs=0.89, p>0.001), which poses the possibility of using Cx. theileri as species indicator of An labranchiae. Moreover, the pairwise comparison and Ordination Corresponding Analyses ascertained the presence of a significant association between species distribution/density and climate zones in the study area (K-W U=51, p>0.01), and confirm the effect of the climate changes on the mosquito population. Furthermore, the members of Cx. pipiens s.l population showed a variation in their morphology, we demonstrated the unusual keys to facilitate the morphological identification in future inventories and to discriminate local species of Cx. pipiens complex. Finally, mosquito control is indispensable and the use of essential oils inVI mosquito control is considered as a potential alternative of synthetic insecticides; therefore, we aimed to assess the larvicidal activity of the essential oils extracted from five medicinal plants collected from northeastern Algeria against Cs longiareolata larvae, a vector of Plasmodium species in birds and one of the most abundant mosquito species at the studied region. The essential oils extracted from: Thymus vulgaris, Artemisia herba-alba, Juniperus phoenicea, Rosmarinus officinalis and Eucalyptus globulus, were tested against the 3rd and 4th instar Culiseta longiareolata larvae; the larvae were exposed to a series of concentrations of the tested essential oils for 24h. The concentrations that caused between 10% and 90% mortality was replicated four times, the entire test was repeated three times. The collected data was used to determine the LC50 and LC90 values. The tested oils revealed an efficient larvicidal activity, T. vulgaris showed 100% mortality at 80ppm final concentration, while the other tested oils showed 100% mortality at 200ppm. Furthermore, the lethal concentrations that caused 50% and 90% mortality (LC50 and LC90) were varying, T. vulgaris was the most efficient essential oil (LC50=25.64ppm, LC90=50.53ppm), followed by J. Phoenicea (LC50=59.83ppm, LC90=137.68ppm), R. officinalis (LC50= 64.18ppm, LC90= 96.55ppm), A. herba-alba (86.67ppm LC50 and LC90=139.55ppm), then E. globulus (LC50=95.83ppm, LC90= 168.25ppm). Thus, The use of essential oils or their principal active components as α-pinene, 1,8-cineole and Camphor may serve as an eco-friendly method to control mosquito larvae. Consequently, the study provides a comprehensive program to control the mosquit population in the Setif region