Blood feeding patterns of the Culex pipiens complex in equestrian land uses and their implications for arboviral encephalitis risk in temperate Argentina

Abstract

Blood feeding patterns of mosquitoes are a key component in the dynamics of arboviral encephalitides transmission. In temperate Argentina, the members of the Culex pipiens complex include Cx. pipiens molestus, Cx. quinquefasciatus and their hybrids. To characterize their blood feeding patterns, adult resting mosquitoes were collected monthly during the warm season in urban and rural equestrian fields. The availability of birds and domestic mammals per site was characterized. The blood source and the complex member were successfully identified for 89 specimens using PCR. Blood of 19 vertebrate species was isolated including four mammals (most common feeds from dog, Canus lupus 19% of the blood meals; and horse, Equus caballus 18%) and 15 birds (picazuro pigeon, Patagioenas picazuro 11%; eared dove, Zenaida auriculata 10%; chicken, Gallus gallus 9%). The Forage Ratio (FR), calculated as the proportion of feeds taken from a given host species with respect to that host availability in the environment, suggested preference for dog by all members of the complex (FR ≥4.5).On the contrary, FR values suggested avoidance for horse by Cx. quinquefasciatus and the hybrid (FR ≤0.8), and a use proportional to its abundance by Cx. pipiens molestus (FR = 1.1-1.2 in urban and rural sites, respectively). FR values suggesting preference were obtained for avian species of the orders Passeriformes (7 species in total) and Columbiformes ( 5) by all members of the complex (FR ≥ 3.3), whereas values for monk parakeet (Myiopsitta monachus, Psiitaciformes) suggested avoidance by Cx. quinquefasciatus in urban sites (FR = 0.4) and by Cx. pipiens molestus in rural sites (FR = 0.3) but not in urban sites (FR = 1.4). A mammal-bird index (MBI, from −1 all avian to +1 all mammalian blood meals) was calculated for each member of the complex and urbanization category. Values were negative for Cx. quinquefasciatus (MBI urban = −0.60, MBI rural = −0.33) and positive for Cx. pipiens molestus (MBI urban = 0.20, MBI rural = 0.60), indicating a higher proportion of feeds taken on birds and mammals, respectively, regardless of the urbanization category. In temperate Argentina, the members of the Cx. pipiens complex fed both on horses and on birds, thus representing a real risk of transmission of arboviral encephalitides from avian enzootic cycles to horse epizootics.

Host–mosquito interactions in rural and urban equestrian facilities from temperate Argentina

“…quinquefasciatus ) that successfully exploit urban settings. At the host level, rural facilities also exhibited a greater richness of avian species than urban locations (44 vs 32, Cardo et al, 2023). Based on mosquitoes’ identity, in urban and rural networks, the combination of host‐seeking behaviour and variable host availability determines the nature of host‐biting interactions.…”

“…DNA was isolated from each abdominal content following a HotSHOT protocol (Truett et al, 2000) and used as template in a Polymerase chain reaction (PCR) to identify vertebrate hosts. Bloodmeal analysis was performed with primers Mod_RepCOI_F (5’‐TNTTYTCMACYAACCACAAAGA‐3′) and VertCOI_7216_R (5’‐CARAAGCTYATGTTRTTYATDCG‐3′) (Reeves et al, 2018), premix concentrations and cycling conditions, as previously described (Cardo et al, 2023). Two negative controls were included in each PCR reaction, in which sterile distilled water or the product of a HotSHOT extraction on the abdomen of an unfed female replaced the template.…”

“…The availability of birds and domestic mammals as well as the blood-feeding patterns of the members of the Cx. pipiens complex in six of the seven equestrian facilities sampled herein have been recently described (Cardo et al, 2023).…”

“…(5'-CARAAGC- et al, 2018), premix concentrations and cycling conditions, as previously described (Cardo et al, 2023). Two negative controls were included in each PCR reaction, in which sterile distilled water or the product of a HotSHOT extraction on the abdomen of an unfed female replaced the template.…”

“…In equestrian facilities from temperate Argentina, blood‐feeding patterns of the members of the Cx. pipiens complex have been recently described (Cardo et al, 2023). The objective of the present work is to complement our previous findings through the characterisation of the blood feeds of the entire mosquito community in equestrian facilities and to analyse their interactions with vertebrate hosts in urban and rural environments.…”