ABSTRACT
Introducción. El estudio de los aspectos de la biología de los mosquitos Anopheles spp.. fortalece la vigilancia entomológica. Objetivo. Determinar los aspectos de la biología y el comportamiento de las especies adultas del género Anopheles presentes en el área urbana de Puerto Carreño. Materiales y métodos. Se capturaron Anopheles spp.. silvestres que se habían posado en personas, en el intradomicilio y peridomicilio de viviendas ubicadas en el área urbana del municipio de Puerto Carreño (Vichada), entre las 18:00 y las 06:00 horas, durante dos noches consecutivas por mes y durante ocho meses. Se determinó la actividad de picadura para cada especie, la infección natural por Plasmodium falciparum y P. vivax VK247 y VK210 mediante la técnica ELISA, y se determinó la tasa de inoculación entomológica. Los individuos pertenecientes al complejo Albitarsis se determinaron mediante amplificación en cadena de la polimerasa del fragmento del gen white. Resultados. En orden de abundancia, se encontraron: An. darlingi (n=1.166), An. marajoara sensu stricto (n=152), An. braziliensis (n=59), An. albitarsis F (n=25), An. albitarsis sensu lato (n=16), An. argyritarsis (n=3) y An. oswaldoi sensu lato (n=2). Anopheles darlingi registró dos picos de actividad de picadura entre las 21:00-22:00 y las 5:00-06:00 horas en el peridomicilio y, entre las 21:00-22:00 y las 04:00-05:00 horas, en el intradomicilio. Esta especie se encontró naturalmente infectada por P. vivax VK210 y registró una tasa de inoculación entomológica de dos para el año. Anopheles marajoara s.s. se encontró naturalmente infectado por P. falciparum y registró una tasa de inoculación entomológica de 5 para el año, con un máximo de actividad de picadura entre las 18:00 y las 19:00 horas, tanto en el intradomicilio como en el peridomicilio. Conclusión. Es posible que exista transmisión de malaria en el área urbana de Puerto Carreño (Vichada) y An. darlingi y An. marajoara s.s. serían las especies incriminadas.
Introduction. The study of the biological aspects of Anopheles spp., strengthens the entomological surveillance. Objective. To determine biological aspects and behavior of adult Anopheles mosquitoes in the urban area of Puerto Carreño municipality, Vichada, Colombia. Materials and methods. Wild anophelines were collected landing on humans both indoors and outdoors between 18:00h and 06:00h for 50 min/h during two consecutive nights/month for eight months in the urban area of Puerto Carreño. The biting rate activity, the natural infection by Plasmodium falciparum and P. vivax VK247 and VK210 using ELISA, and the annual entomological inoculation rate were determined for each species. The members of the Albitarsis complex were determined by amplificacion of the white gene by polymerase chain reaction. Results. In order of abundance the species found were An. darlingi (n=1,166), An. marajoara sensu stricto (n=152), An. braziliensis (n=59), An. albitarsis F (n=25), An. albitarsis sensu lato (n=16), An. argyritarsis (n=3) and An. oswaldoi sensu lato (n=2). An. darlingi showed two activity peaks between 21:00 to 22:00 and 05:00 to 06:00 hours outdoors and between 21:00 to 22:00 and 04:00 to 05:00 indoors. Natural infection of this species was found with P. vivax VK210 and its annual entomological inoculation rate was 2. Natural infection of An marajoara sensu stricto with P. falciparum was found, with an annual entomological inoculation rate of 5 and a peak biting activity between 18:00 to 19:00 hrs both indoors and outdoors. Conclusion. Transmission of malaria in the urban area of Puerto Carreño, Vichada, can occur by An. darlingi and An. marajoara s.s.
Subject(s)
Animals , Humans , Anopheles , Insect Vectors , Malaria/transmission , ColombiaABSTRACT
In several districts of Boa Vista, state of Roraima, Brazil we found Anopheles (Nyssorhynchus) albitarsis E to be the primary vector of human malaria parasites, and during 2001-2002 it was significantly more abundant than An. darlingi (p < 0.001). Other species sampled were An. (Nys.) braziliensis, An. (Ano.) peryassui, An. (Nys.) nuneztovari, An. (Nys.) oswaldoi s.l., and An. (Nys.) triannulatus. As determined by the ELISA technique An. darlingi had a higher overall infection rate (2.1 percent) compared with An. albitarsis E (1.2 percent). However, a marginally higher proportion of An. albitarsis E was infected with Plasmodium vivax compared with An. darlingi, and the An. albitarsis E biting index was also much higher. These results suggest the importance of An. albitarsis E in malaria transmission in a savannah ecoregion of northern Amazonian Brazil, and reconfirm the importance of An. darlingi even if at lower abundance.
Subject(s)
Humans , Animals , Anopheles/parasitology , DNA, Protozoan/analysis , Insect Vectors/parasitology , Malaria/transmission , Plasmodium/isolation & purification , Anopheles/classification , Brazil , Enzyme-Linked Immunosorbent Assay , Malaria/parasitology , Plasmodium/classification , Plasmodium/genetics , SeasonsABSTRACT
Malaria risk factor studies have traditionally used microscopy readings of blood slides as the measure of malaria infection in humans, although alternatives are available. There is the need for an assessment of how the use of these alternative diagnostic approaches will influence the efficiency and significance of epidemiological studies. In an area of Sri Lanka with known risk factors for malaria, two cross-sectional surveys were done at the start and at the peak of transmission season. Microscopy was compared with enzyme-linked immunosorbent assays (ELISA) and polymerase chain reaction (PCR). The major risk factor in this area was the location of houses relative to confirmed vector breeding sites. At the peak of the transmission season, the results pointed in the same direction, irrespective of the diagnostic method used. However, the importance of distance from the breeding site was not statistically significant when microscopy was used, which can be explained by the lower prevalence of microscopy positivity in comparison to the prevalence of ELISA- and PCR-positivity. This study suggests that in low-transmission areas, such as Sri Lanka, smaller sample sizes can be used for epidemiological research studies using PCR instead of microscopy to estimate parasite prevalence. This efficiency gain has to be weighed against the higher cost and complexity of the PCR. PCR cannot replace microscopy as the standard diagnostic procedure at the field level. ELISA is not directly comparable with microscopy and PCR but it can also be a useful tool in malaria epidemiological studies. This study indicates that cross-sectional surveys are only efficient if they take place during peak transmission season. Cross sectional surveys currently implemented by the Sri Lankan government in response to local malaria outbreaks can form the basis for valid epidemiological studies and be used for the generation of malaria risk maps if samples were also analyzed using PCR.