Search

Vector abundance maps are a necessary step in mapping the risks associated with vector-borne diseases to help target surveillance and control actions. Risk mapping requires sampling vector species at different scales, which is made difficult by heterogeneity in vector spatial distribution and dynamics. In Morocco, Culicoides were responsible for African horse sickness (AHS) outbreaks in the 1960s and late 1980s. Since 2004, Morocco is facing an endemic situation of bluetongue virus (BTV) transmission. Our study aimed to produce first abundance maps for the most abundant Culicoides species, and risk maps for BTV and AHSV, across the country. We conducted a national cross-sectional survey using a stratified sampling strategy based on eco-agronomic zoning, for which we hypothesized the homogeneity of Culicoides diversity and dynamics. Historical collection time series were used to determine maximum abundance periods based on climate zonation. This strategy allowed to plan a national sampling of Culicoides abundance during a single collection season. Collections were conducted twice a year with 144 farms trapped. Culicoides were sampled for consecutive 48h using a suction light trap. We obtained a total of 262 samples under identification process. The results so far have shown that C. imicola was the most common species (present in at least 70% of the sites), followed by C. circumscriptus (absent at mild altitudes) and C. kingi (mostly present in the south). Culicoides obsoletus/C. scoticus have been collected frequently in the country, including in the south. This highlighted the wide and unexpected spatial distribution of these species from Scandinavia to North Africa reinforcing the existence of sibling species. Other species have also been identified, such as C. puncticollis, C. newsteadi, C. catanei/C. gegjelensis (rather present in the north on the coast), C. punctatus (rare in the south), C. pulicaris/C. lupicaris and C. kurensis. Interestingly, although C. paolae is mentioned in the literature as being associated with prickly pears in the Mediterranean basin, this species was absent in many areas heavily vegetated by this fig tree. This original dataset will be used to determine the ecological factors of the abundance and distribution of Culicoides of veterinary interest in order to provide accurate mapping of vector-related risks across Morocco.

For vector-borne diseases, producing abundance maps is a necessary step for risk mapping, which is an important tool to help focusing surveillance actions. Such as mapping requires sampling vector insects at a national/regional scale, which is quite difficult due to important heterogeneity in spatial distribution and in temporal dynamics. In Morocco, Culicoides biting midges were responsible for African horse sickness (AHS) outbreaks in the 1960s and the most recently in the late 1980s. They are also involved in the enzootic transmission of bluetongue (BT) virus since 2004. We aimed to produce first abundance maps for most abundant Culicoides species, and then risk maps for BTV and AHSV, across Morocco. In 2016, we compared species diversity in ruminant farms and in horse holding to determine if abundance maps derived from sampling in ruminant farms could be used to generate risk maps for both AHS and BT viruses. In 2017, we carried out a cross-sectional survey at the national scale. We used a stratified sampling strategy using eco-agronomic zones, with which we hypothesized homogeneity of Culicoides diversity and dynamics. We used historical collection time series to determine periods of abundance peak according to climatic zonation. This strategy allowed us to plan a national sampling of Culicoides abundance. In 2016, we found the same species in cattle and horse holdings. In addition, Culicoides paolae – reported in the literature as associated with Barbary fig trees, and Culicoides scoticus were recorded for the first time in Morocco. These records were confirmed by molecular assay. In 2017, collection campaign was conducted twice a year (from late April to June and from September to October): 144 farms were trapped during this period. At each visit, Culicoides populations were sampled for 48 consecutive hours using a light trap. A total we obtained 262 samples. Samples were currently under identification process. The next step will be to determine ecological drivers of abundance and distribution to provide accurate Culicoides mapping across Morocco.

International audience