Various species of Anopheles (Nyssorhynchus) were studied in the Amazon with the objective of determining their importance as malaria vectors. Of the 33 known Anopheles species occurring in the Amazon, only 9 were found to be infected with Plasmodium. The different species of this subgenus varied both in diversity and density in the collection areas. The populations showed a tendency towards lower density and diversity in virgin forest than in areas modified by human intervention. The principal vector, An. darlingi, is anthropophilic with a continuous activity cycle lasting the entire night but peaking at sunset and sunrise. These species (Nyssorhynchus) are peridomiciliary, entering houses to feed on blood and immediately leaving to settle on nearby vegetation. Anopheles nuneztovari proved to be zoophilic, crepuscular and peridomiciliary. These habits may change depending on a series of external factors, especially those related to human activity. There is a possibility that sibling species exist in the study area and they are being studied with reference to An. darlingi, An. albitarsis and An. nuneztovari. The present results do not suggest the existence of subpopulations of An. darlingi in the Brazilian Amazon.

/pdf/malaria-vectors-in-the-brazilian-amazon-anopheles-of-the-2mwuwlqfwx.pdf

Malaria vectors in the Brazilian Amazon: Anopheles of the subgenus Nyssorhynchus

The quantitative relationship between the emission rate of host attractants (whether olfactory or visual) and the host-seeking rate of insect vectors of disease will determine the relationship between host group size and the prevalence of vector-borne diseases within each group. A comparative study was carried out to test whether interspecific differences in social behaviour significantly influence the malaria infection rates of different Amazonian primate species. The aetiological agent of monkey malaria in Amazonia is Plasmodium brasilianum Gonder & BerenbergGossler, 1908, and blood smear examinations of 3599 Amazonian primates over three decades have demonstrated an average infection rate with P. brasilianum of 10 4%. P. brasilianum has been detected in only 17/33 species examined, and the infection rate of those 17 species ranged from 2 1 to 5000%. Logistic and standard linear regressions, at three different taxonomic levels, demonstrate that a significant proportion of the interspecific variation in infection rate can be explained by variation in average body weight (W) and average sleeping group size (G). Infection rate could increase with W and G due to enhanced odour production attracting a greater number of anopheline mosquito vectors of monkey malaria per host. Given that parasites reduce host fitness, the results suggest that, contrary to conventional wisdom, mosquito-borne diseases are a significant cost associated with larger group size. Key-words: Body weight, host-seeking behaviour, monkey malaria, mosquito, Plasmodium brasilianum, sleeping group size

Malaria Infection Rate of Amazonian Primates Increases with Body Weight and Group Size

Data on the prevalence and distribution of species of Anopheles in Ariquemes (State of Rondonia) show, that the diversity is greater at the periphery of the town and that Anopheles darlingi is recorded at nearly all of the sampling points. The entomological survey revealed different levels of penetration by A. darlingi in to the urban area: Sectors 1 and 3 are free of malaria transmission, Sectors 2 and 4 show risks at the periphery, and the Industrial Sector, Sector of Special Areas, BNH housing estate, Sector 5 and the Old Town are areas of high risk for malaria. These areas had the highest indices of mosquitoes per man-hour, with variations of this index during the sampling period and depending on locality. Measures of population density showed seasonal variation, with the lowest indices during the rainy season. Malaria transmission is discussed in relation to 1) the physical structure of the town at the time it was jounded ; 2) the streams that border the urban area and their relation to the life cycle of the anophelines; 3) biting activity of the species colected in natural environments and areas altered by man; and 4) the importance of environmental management for malaria control by reducing the vector population density. To reduce the penetration of urban areas by mosquitoes from the surrounding countryside, a protective belt around the town is proposed. This belt should be of sparse forest and include alternative hosts to encourage the zoophilic tendencies of the anophelines. Infection rates among anophelines in areas authocthonous for malaria incriminate A. darlingi as a vector. The possibility of transmission by other species is discussed.

https://www.scielo.br/pdf/rimtsp/v30n3/17.pdf

[Biology of Amazonian Anopheles. XII. Occurrence of Anopheles species, transmission dynamics and malaria control in the urban area of Ariquemes (Rondônia)].

En los ultimos anos, el numero de casos de malaria urbana en Buenaventura, Colombia, ha aumentado de 576 en 1987 a 3 296 en 1991 y 2 017 en 1992, por lo que se desarrollo un estudio epidemiologico para identificar patrones de transmision de la malaria en este municipio del litoral pacifico colombiano. Se describen los hallazgos entomologicos en relacion con los vectores, los criaderos y el comportamiento de las especies de Anopheles durante el periodo comprendido entre junio de 1993 y mayo de 1994. De los 469 posibles criaderos del area urbana, 28 fueron positivos a anofelinos. En la zona rural vecina de Buenaventura 20 de 80 posibles criaderos fueron positivos a las formas inmaduras del mosquito. Los sitios donde se encontro con mas frecuencia Anopheles albimanus fueron las excavaciones de mineria, los lagos y los estanques para piscicultura. Los criaderos de Anopheles nuneztovari fueron los pozos de lluvia y estanques de peces. Anopheles neivai se recolecto en bromelias. De las capturas intra y peridomiciliarias de mosquitos adultos, 90% correspondieron a Anopheles albimanus. De las hembras, 54,8% habian realizado al menos una ovipostura. Esta especie tuvo una actividad peridomiciliaria maxima entre las 18.00 y 22.00 horas. La mayor tasa de picadura peridomiciliaria fue de 7,1 y correspondio a marzo de 1994. Se espera que esta informacion entomologica permita poner en marcha un importante proceso de participacion comunitaria e implementar medidas de control que esten orientadas por nuestros resultados.

/pdf/transmision-de-la-malaria-urbana-en-buenaventura-colombia-qqebyyzv09.pdf

Transmisión de la malaria urbana en Buenaventura, Colombia: aspectos entomológicos

Woody plants growing in cerrado and forest communities of south-east Brasil were found to have low levels of nitrate reductase activity in their leaves suggesting that nitrate ions are not an important nitrogen source in these communities. Only in the leaves of species growing in areas of disturbance, such as gaps and forest margins, were high levels of nitrate reductase present. When pot-grown plants were supplied with nitrate, leaves and roots of almost all species responded by inducing increased levels of nitrate reductase. Pioneer or colonizing species exhibited highest levels of nitrate reductase and high shoot: root nitrate reductase activities. Glutamine synthetase, glutamate synthase and glutamate dehydrogenase were present in leaves and roots of the species examined.15N-labelled nitrate and ammonium were used to compare the assimilatory characteristics of two species:Enterolobium contortisiliquum, with a high capacity to reduce nitrate, andCalophyllum brasiliense, of low capacity. The rate of nitrate assimilation in the former was five times that of the latter. Both species had similar rates of ammonium assimilation. Results for eight species of contrasting habitats showed that leaf nitrogen content increased in parallel with xylem sap nitrogen concentrations, suggesting that the ability of the root system to acquire, assimilate or export nitrate determines shoot nitrogen status. These results emphasise the importance of nitrogen transport and metabolism in roots as determinants of whole plant nitrogen status.

Partitioning of inorganic nitrogen assimilation between the roots and shoots of cerrado and forest trees of contrasting plant communities of South East Brasil.

Observations on the biting activity of the Anopheles nuneztovari collected between 18:00 and 22:00 in different places along BR-174 Highway (Manaus/Boa Vista) which presented the exophilic habit are here related. Variations at the beginning and at the end of the biting activity were noted, but it is concentrated approximately between 18:30 and 19:10.

/pdf/biologia-de-anofelinos-amazonicos-iv-observacoes-sobre-a-436ai1oh58.pdf

José Marinho Correia

Papers

Biologia de anofelinos amazônicos. IV. Observações sobre a atividade de picar de Anopheles nuneztovari Gabaldon (Diptera, Culicidae)