The Romanomermis iyengari parasite for Anopheles pseudopunctipennis suppression in natural habitats in Oaxaca State, Mexico

Abstract

In September and November 1996 Romanomermis iyengari Welch, a parasite of larval mosquitoes, was released in 44 natural larval habitat sites of Anopheles pseudopunctipennis Theobald in an attempt to reduce the larval populations of this important malaria vector. The selected treatment sites ranged in size from 5 to 500 m2. The study was carried out in Pochutla District of Oaxaca State, on the Pacific coast of Mexico. Chemical pesticides to reduce vector populations have been the principal tool in malaria suppression campaigns. However, the excessive use of these chemicals has created pesticide resistance and other serious collateral problems. Therefore, a biological control project using agents that are pathogens of Anopheles larvae was initiated in 1996. The principal objective was to establish mass rearing capacities for R. iyengari. Detailed methodology for rearing and introducing these nematodes into mosquito larval habitats was established at the National Polytechnic Institute of Oaxaca State. Before application of the parasites to larval habitats, site characteristics were determined, including size, depth, aquatic vegetation, salinity, pH, conductivity, temperature, and pretreatment larval density. With a compressed air sprayer, infective mermithid parasites were released at rates of either 2,000 or 3,000/m2, and the parasites produced high levels of infection. Anopheles populations were sampled 72 h posttreatment, and the larvae obtained were taken to the laboratory and examined through microscopic dissection to determine infection levels and mean parasitism. Nematode parasitism ranged from 85 to 100% at all the treatment sites, even though no previous information concerning field parasitism of An. pseudopunctipennis by R. iyengari has been reported. In addition, a significant reduction of mosquito larval density at the treatment sites was found five days after the nematode application. Levels of parasitism were indicative of the number of mosquito larvae killed by the treatment since infected larvae never progressed to the pupal stage. Results from sampling nine of the sites 2 months after the initial application of nematodes indicated that a high number of mosquito larvae were infected by parasites that had emerged from eggs previously deposited in the stratum. This work suggests the potential of this mermithid to reduce An. pseudopunctipennis populations in Oaxaca State.

DNA barcodes and evidence of cryptic diversity of anthropophagous mosquitoes in Quintana Roo, Mexico

“…vestitipennis and An. albimanus, are considered the main malaria vector in Mexico (Hiwat & Bretas, 2011;Loyola, Arrendondo, Rodríguez, Browns, & Vasa Marin, 1991;Mijares, Pérez Pacheco, Tomás Martínez, Cantón, & Ambrosio, 1999). By another hand, Aedes aegypti is the main vector of Dengue, Chikungunya, and Zika virus in Quintana Roo (Sánchez-Rodríguez et al, 2014;Torres-Avendaño et al, 2015).…”

Ecology of Anopheles darlingi Root with respect to vector importance: a review

“…albimanus (coastline and marshland). Anopheles vestitipennis is considered a secondary vector [19]. Anopheles darlingi plays a minor role in the south-eastern region of the country [20,21], especially in the state of Oaxaca.…”

Microorganismes entomopathogènes, prédateurs et parasites des moustiques: Perspectives pour la lutte raisonnée contre les vecteurs du paludisme en Afrique sub-saharienne

“…Au Cuba, un pays à climat tropical, des essais en milieu naturel ont démontré que R. iyengari décime les populations de différentes espèces de moustiques (Santamarina et al, 1993 ;Santamarina et Mijares, 1995 ;Santamarina et al, 1996). Au Mexique et au Brésil également, il a été démontré que R. iyengari parasite et tue les moustiques vecteurs de maladies y compris diverses espèces d'anophèles (Santamarina et al, 1999 ;Santamarina et Bellini, 2000). On connait aujourd'hui plus de 30 espèces de moustiques susceptibles à l'infection de R. iyengari (Platzer, 2007).…”

“…Au Mexique, une dose de 2000 à 3000 vers pré-parasitiques de R. iyengari par mètre carré de surface a permis d'obtenir un taux d'infection de l'ordre de 85-100% chez les larves d'An. pseudopunctipennis (Santamarina et al, 1999). Des résultats similaires ont été également obtenus au Brésil où, 12 sites naturels de gîte d'Anopheles ont été traités avec 2.000 nématodes infectieux par mètre carré de surface.…”