Anopheles blood meal sources and entomological indicators related to Plasmodium transmission in malaria endemic areas of Colombia.

Malaria is an important public health problem, caused by Plasmodium parasites which are transmitted by female Anopheles mosquitoes that bite humans to obtain blood. The aim of this work was to identify the blood feeding sources of Anopheles female mosquitoes and calculate their entomological indices in relation to Plasmodium transmission. Mosquitoes were collected in malaria endemic localities of the Bajo Cauca and Pacific regions of Colombia using human landing catch and barrier screens, from 18:00 to 24:00 hr, in 2018-2021. Animal censuses within a radius of ∼250 m were carried out at each sampling site. A total of 2018 Anopheles specimens were collected and the most abundant species were Anopheles (Nys.) darlingi and Anopheles (Nys.) nuneztovari. The highest human biting rate was 77.5 bites per person per night (b/p/n) for An. nuneztovari in Córdoba-Pacific and 17.5 b/p/n for An. darlingi in Villa Grande-Bajo Cauca. Both species were active mainly in indoor unwalled rooms of the houses. Only An. nuneztovari from Córdoba-Pacific was infected with Plasmodium, with an entomological inoculation rate of 91.25 infective bites per year. Detection of blood feeding sources demonstrate that humans were the most common host, however, An. nuneztovari showed a preference for feeding on dogs and An. darlingi on pigs, dogs and Galliformes, rather than humans. These results contribute to entomological surveillance information and provide valuable data that can be used to tailor effective control interventions to minimize human-vector contact in these malaria endemic regions.

Spatial fine-resolution model of malaria risk for the Colombian Pacific region.

OBJECTIVE: To categorise and map, at high resolution, the risk of malaria incidence in the Pacific region, the main malaria-endemic region of Colombia. METHODS: The relationship between the environmental variables Normalized Difference Vegetation Index Normalized Difference Water Index, Topographic Wetness Index, precipitation and temperature with the observed Annual Parasitic Index was evaluated using a generalised linear model. An incidence risk map at a resolution of 1 km2 was constructed and projected to the entire endemic region. Associations of malaria risk categories with both presence records and co-occurrence of the three main malaria vectors were determined. RESULTS: A significant correlation was found for the incidence of malaria with precipitation and Normalized Difference Vegetation Index (R2  = 0.98, P < 0.05), whereas there was no significant correlation with the remaining environmental and topographic variables. Moderate- to high-risk areas were located mainly in central Chocó Department along the San Juan and Atrato rivers and in areas west of the Cauca River and Pacific lowlands of the Andes Mountains. There was a statistically significant relationship for the presence of the two main vectors Anopheles darlingi and Anopheles nuneztovari with the high malaria risk category. Furthermore, malaria risk was directly proportional to the number of co-occurring vector species. CONCLUSIONS: The map obtained provides useful information on the risk of malaria in particular places of the Colombian Pacific region. The data can be used by public entities to optimise the allocation of economic resources for vector control interventions and surveillance.

OBJECTIF: Classifier et cartographier, à haute résolution, le risque d'incidence du paludisme dans la région du Pacifique, la principale région de Colombie où le paludisme est endémique. MÉTHODES: La relation entre les variables environnementales, l'Indice de différence de végétation normalisée, l'Indice différence hydrique normalisée, l'Indice d'humidité topographique, les précipitations et la température avec l'indice parasitique annuel observé a été évaluée à l'aide d'un modèle linéaire généralisé. Une carte des risques d'incidence à une résolution de 1 km2 a été construite et projetée sur l'ensemble de la région endémique. Les associations des catégories de risque de paludisme avec les deux, les registres de présence et la co-occurrence des trois principaux vecteurs du paludisme ont été déterminées. RÉSULTATS: Une corrélation significative a été trouvée pour l'incidence du paludisme avec les précipitations et l'indice de différence de végétation normalisée (R2  = 0,98 ; P < 0,05), alors qu'il n'y avait pas de corrélation significative avec les autres variables environnementales et topographiques. Les zones de risque modéré à élevé étaient principalement situées dans le département central du Chocó, le long des rivières San Juan et Atrato, et dans les zones à l'ouest de la rivière Cauca et des basses régions Pacifiques de la Cordillère des Andes. Il y avait une relation statistiquement significative entre la présence des deux principaux vecteurs Anopheles darlingi et Anopheles nuneztovari et la catégorie à haut risque de paludisme. De plus, le risque de paludisme était directement proportionnel au nombre d'espèces de vecteurs co-occurrents. CONCLUSIONS: La carte obtenue fournit des informations utiles sur le risque de paludisme dans des endroits particuliers de la région Pacifique de la Colombie. Les données peuvent être utilisées par les entités publiques pour optimiser l'allocation des ressources économiques pour les interventions de lutte contre les vecteurs et la surveillance.

Composition and structure of the culturable gut bacterial communities in Anopheles albimanus from Colombia.

The understanding of factors affecting the gut bacterial communities in malaria vectors is essential for the design of vector control interventions, such as those based on a paratransgenic approach. One of the requirements of this method is the availability of bacteria from the mosquito susceptible to culture. Thus, the aim of this study was to evaluate the composition and structure of the culturable gut bacterial communities in field mosquitoes Anopheles albimanus from Colombia, in addition to generate a bacterial collection to further analyze microbial functional activity. Gut bacteria were isolated from An. albimanus larvae and adult mosquitoes collected in localities of the Atlantic and Pacific Coasts. The bacterial isolates were grouped in 28 morphospecies that corresponded to three phyla, three classes, nine families and 14 genera. The larvae guts from San Antero (Atlantic Coast) and Buenaventura (Pacific Coast) shared the genera Bacillus and Lysinibacillus and in adults, Bacillus and Bacillus cereus Group were registered in both localities. Gut bacterial richness was higher in adults from the Pacific with respect to the Atlantic Coast, while larval richness was similar in samples of both coasts. The Shannon index indicated uniformity in morphospecies abundances in both localities. Finally, the characterization of morphospecies from the gut of Anopheles albimanus mosquitoes from Colombia by culture-dependent methods complemented with 16S rRNA gene sequencing allowed the definition, at a finer resolution, of the composition and structure of these microbial communities. In addition, the obtained bacterial culture collection will allow further evaluation of the microorganisms for their potential as biocontrol agents.