Comparative study of distribution of anopheline vectors (Diptera: Culicidae) in areas with and without malaria transmission in the highlands of an extra-Amazonian region in Brazil.

This study compares the distribution of anopheline mosquitoes in a malaria-endemic municipality (MAL) and a malaria-free municipality (FREE) in an area of the Atlantic Forest in Brazil. Simultaneous quarterly nightly captures were made in three locations in each municipality. One Shannon light trap (Shannon light traps were home made according to specifications published in Am. J. Trop. Med. 1939; 19: 131-140) (SLT) and five CDC light traps (a kind of automatic trap fed by batteries of 12 V and 7 amp/h, with dry ice as a source of CO2; John W. Hock Company, Gainesville, FL) (CLT) (two in the canopy and three at ground level) were operated from 6:00 p.m. to 6:00 a.m. More specimens were captured in MAL (362 in SLTs and 126 in CLTs) than in FREE (66 in SLTs and 59 in CLTs). For the SLTs, Simpson's dominance index was similar in MAL and FREE (D = 0.15 versus D = 0.203, P > 0.7), but Shannon's diversity index was higher for MAL = 1.969 versus H = 1.641, P < 0.01). For the CLTs, Simpson's dominance index was higher in MAL (D = 0.416 versus 0.2688, P < 0.001), and the Shannon diversity index was higher in FREE (H = 1.5222 versus H = 1.115, P < 0.01). In SLTs, Anopheles (Kerteszia) cruzii s.l. frequencies were higher in MAL (chi2 = 23.39; P = 0.000001). In CLTs, An. cruzii s.l. was present in all strata in MAL but only in the canopy inside the forest in FREE (17 specimens). An. cruzii s.l. represented a higher proportion of anophelines in MAL (chi2 = 31; P < 0.000001). The factors that differed in these two areas were anopheline species density and An. cruzii s.l. abundance and distribution.

Entomological characterization and natural infection of anophelines in an area of the Atlantic Forest with autochthonous malaria cases in mountainous region of Espírito Santo State, Brazil.

Autochthonous malaria cases in the state of Espírito Santo, Brazil, are distributed in mountainous regions surrounded by the Atlantic Forest. While some aspects of this disease are unclear, detection of possible vector species can help to elucidate epidemiological uncertainties. Entomological and natural infection studies were carried out using anophelines (Diptera: Culicidae) captured in the municipality of Santa Tereza, ES. Monthly captures were made from March 2004 to February 2006. CDC-CO2 traps were used from dusk (6:00 P.M.) to dawn (6:00 A.M.) to capture anophelines in the following habitats: near the houses, in open areas (at ground level) and inside, and at the margins of the forest (canopy and ground level). Shannon light traps were also used at the same locations of the CDC-CO2 traps. A total of 2,290 anophelines within 10 species were captured. The relative frequency of Anopheles (Kerteszia) cruzii Dyar & Knab / A.(K.) homunculus Komp was the highest, with the majority captured in CDC-CO2 traps installed in the forest canopy. The main species captured in Shannon traps was A.(Nyssorhynchus) strodei Root. The largest number of anophelines was captured from July to September and from 6:00 P.M. to 10:00 P.M. Anopheles (K.) cruzii is the probable vector for malaria transmission inside or near the Atlantic Forest fragments, but the role of other species cannot be ignored, as 53% of the sampled anophelines belonged to the subgenus Nyssorhynchus. The natural infection of A. cruzii, A. parvus (Chagas) and A. galvaoi Causey, Deane & Deane by Plasmodium vivax detected by PCR from DNA extracted from their thoraxes supports this view.

Entomological characterization and natural infection of anophelines in an area of the Atlantic Forest with autochthonous malaria cases in mountainous region of Espírito Santo State, Brazil / Caracterização entomológica e infecção natural de anofelinos em área de Mata Atlântica, com casos autóctones de malária, em regiões montanhosas do Espírito Santo

Autochthonous malaria cases in the state of Espírito Santo, Brazil, are distributed in mountainous regions surrounded by the Atlantic Forest. While some aspects of this disease are unclear, detection of possible vector species can help to elucidate epidemiological uncertainties. Entomological and natural infection studies were carried out using anophelines (Diptera: Culicidae) captured in the municipality of Santa Tereza, ES. Monthly captures were made from March 2004 to February 2006. CDC-CO2 traps were used from dusk (6:00 P.M.) to dawn (6:00 A.M.) to capture anophelines in the following habitats: near the houses, in open areas (at ground level) and inside, and at the margins of the forest (canopy and ground level). Shannon light traps were also used at the same locations of the CDC-CO2 traps. A total of 2,290 anophelines within 10 species were captured. The relative frequency of Anopheles (Kerteszia) cruzii Dyar & Knab / A. (K.) homunculus Komp was the highest, with the majority captured in CDC-CO2 traps installed in the forest canopy. The main species captured in Shannon traps was A. (Nyssorhynchus) strodei Root. The largest number of anophelines was captured from July to September and from 6:00 P.M. to 10:00 P.M. Anopheles (K.) cruzii is the probable vector for malaria transmission inside or near the Atlantic Forest fragments, but the role of other species cannot be ignored, as 53 percent of the sampled anophelines belonged to the subgenus Nyssorhynchus. The natural infection of A. cruzii, A. parvus (Chagas) and A. galvaoi Causey, Deane & Deane by Plasmodium vivax detected by PCR from DNA extracted from their thoraxes supports this view.

No Espírito Santo, os casos de malária autóctone estão distribuídos na região serrana próximo aos fragmentos de Mata Atlântica. Uma vez que alguns aspectos da doença são obscuros, a detecção das possíveis espécies de vetores pode auxiliar na elucidação de incertezas epidemiológicas. Estudos entomológicos e de infecção natural foram realizados com anofelinos (Diptera: Culicidae) capturados no município de Santa Tereza, ES. Capturas mensais foram realizadas de março de 2004 a fevereiro de 2006. Armadilhas CDC-CO2 foram utilizadas do crepúsculo (18:00h) ao amanhecer (6:00h), para capturar anofelinos nos seguintes habitats: próximo ao domicílio e área aberta (solo), margem e interior da mata (solo e copa). Armadilhas Shannon também foram utilizadas nos mesmos locais que as de CDC-CO2. Capturou-se o total de 2.290 anofelinos distribuídos em 10 espécies. A maior frequência relativa foi de Anopheles (Kerteszia) cruzii Dyar & Knab / A. (K.) homunculus Komp, sendo a maioria capturada em CDC-CO2 instalada na copa da mata. A principal espécie capturada em armadilha Shannon foi A.(Nyssorhynchus) strodei Root. O maior número de anofelinos foi capturado entre julho e setembro das 18:00h às 22:00h. Provavelmente A. (K.) cruzii é responsável pela transmissão da malária dentro ou próximo aos fragmentos de Mata Atlântica. Entretanto, a participação de outras espécies não pode ser ignorada, visto que 53 por cento da amostragem foi constituída pelo subgênero Nyssorhynchus. A detecção de Plasmodium vivax no tórax de A. cruzii, A. parvus (Chagas) e A. galvaoi Causey, Deane & Deane por meio de PCR reforça esse argumento.

Epidemiologic aspects of the malaria transmission cycle in an area of very low incidence in Brazil.

BACKGROUND: Extra-Amazonian autochthonous Plasmodium vivax infections have been reported in mountainous regions surrounded by the Atlantic Forest in Espírito Santo state, Brazil. METHODS: Sixty-five patients and 1,777 residents were surveyed between April 2001 and March 2004. Laboratory methods included thin and thick smears, multiplex-PCR, immunofluorescent assay (IFA) against P. vivax and Plasmodium malariae crude blood-stage antigens and enzyme-linked immunosorbent assay (ELISA) for antibodies against the P. vivax-complex (P. vivax and variants) and P. malariae/Plasmodium brasilianum circumsporozoite-protein (CSP) antigens. RESULTS: Average patient age was 35.1 years. Most (78.5%) were males; 64.6% lived in rural areas; 35.4% were farmers; and 12.3% students. There was no relevant history of travel. Ninety-five per cent of the patients were experiencing their first episode of malaria. Laboratory data from 51 patients were consistent with P. vivax infection, which was determined by thin smear. Of these samples, 48 were assayed by multiplex-PCR. Forty-five were positive for P. vivax, confirming the parasitological results, while P. malariae was detected in one sample and two gave negative results. Fifty percent of the 50 patients tested had IgG antibodies against the P. vivax-complex or P. malariae CSP as determined by ELISA. The percentages of residents with IgM and IgG antibodies detected by IFA for P. malariae, P. vivax and Plasmodium falciparum who did not complain of malaria symptoms at the time blood was collected were 30.1% and 56.5%, 6.2% and 37.7%, and 13.5% and 13%, respectively. The same sera that reacted to P. vivax also reacted to P. malariae. The following numbers of samples were positive in multiplex-PCR: 23 for P. vivax; 15 for P. malariae; 9 for P. falciparum and only one for P. falciparum and P. malariae. All thin and thick smears were negative. ELISA against CSP antigens was positive in 25.4%, 6.3%, 10.7% and 15.1% of the samples tested for "classical" P. vivax (VK210), VK247, P. vivax-like and P. malariae, respectively. Anopheline captures in the transmission area revealed only zoophilic and exophilic species. CONCLUSION: The low incidence of malaria cases, the finding of asymptomatic inhabitants and the geographic separation of patients allied to serological and molecular results raise the possibility of the existence of a simian reservoir in these areas.