Natural transovarial transmission of dengue virus 4 in Aedes aegypti from Cuiabá, State of Mato Grosso, Brazil.

INTRODUCTION: Dengue is the most prevalent arboviral disease in tropical areas. In Mato Grosso, outbreaks are reported every year, but studies on dengue in this state are scarce. METHODS: Natural transovarial infection of Aedes aegypti by a flavivirus was investigated in the Jardim Industriário neighborhood of Cuiabá, Mato Grosso. Eggs were collected with ovitraps during the dry, intermediate, and rainy seasons of 2012. After the eggs hatched and the larvae developed to adulthood, mosquitoes (n = 758) were identified and allocated to pools of 1-10 specimens according to the collection location, sex, and climatic period. After RNA extraction, multiplex semi-nested RT-PCR was performed to detect the four dengue virus (DENV) serotypes, yellow fever virus, West Nile virus and Saint Louis encephalitis virus. RESULTS: DENV-4 was the only flavivirus detected, and it was found in 8/50 pools (16.0%). Three of the positive pools contained females, and five contained males. Their nucleotide sequences presented 96-100% similarity with DENV-4 genotype II strains from Manaus, Amazonas. The minimum infection rate was 10.5 per 1000 specimens, and the maximum likelihood estimator of the infection rate was 11.6 (95% confidence interval: 4.8; 23.3). CONCLUSIONS: This study provides the first evidence of natural transovarial infection by DENV-4 in Ae. Aegypti in Mato Grosso, suggesting that this type of infection might serve as a mechanism of virus maintenance during interepidemic periods in Cuiabá, a city where dengue epidemics are reported every year. These results emphasize the need for efficient vector population control measures to prevent arbovirus outbreaks in the state.

Natural transovarial transmission of dengue virus 4 in Aedes aegypti from Cuiabá, State of Mato Grosso, Brazil

INTRODUCTION: Dengue is the most prevalent arboviral disease in tropical areas. In Mato Grosso, outbreaks are reported every year, but studies on dengue in this state are scarce. METHODS: Natural transovarial infection of Aedes aegypti by a flavivirus was investigated in the Jardim Industriário neighborhood of Cuiabá, Mato Grosso. Eggs were collected with ovitraps during the dry, intermediate, and rainy seasons of 2012. After the eggs hatched and the larvae developed to adulthood, mosquitoes (n = 758) were identified and allocated to pools of 1-10 specimens according to the collection location, sex, and climatic period. After RNA extraction, multiplex semi-nested RT-PCR was performed to detect the four dengue virus (DENV) serotypes, yellow fever virus, West Nile virus and Saint Louis encephalitis virus. RESULTS: DENV-4 was the only flavivirus detected, and it was found in 8/50 pools (16.0%). Three of the positive pools contained females, and five contained males. Their nucleotide sequences presented 96-100% similarity with DENV-4 genotype II strains from Manaus, Amazonas. The minimum infection rate was 10.5 per 1000 specimens, and the maximum likelihood estimator of the infection rate was 11.6 (95% confidence interval: 4.8; 23.3). CONCLUSIONS: This study provides the first evidence of natural transovarial infection by DENV-4 in Ae. Aegypti in Mato Grosso, suggesting that this type of infection might serve as a mechanism of virus maintenance during interepidemic periods in Cuiabá, a city where dengue epidemics are reported every year. These results emphasize the need for efficient vector population control measures to prevent arbovirus outbreaks in the state. .

Effective surveillance of vector dynamics of Aedes aegypti in a hospital setting in Cuiabá, Mato Grosso, Brazil.

INTRODUCTION: Hospitals are important for vector control of endemic diseases. METHODOLOGY: To investigate the presence of dengue vectors, 30 locations at a university hospital in Cuiabá, Mato Grosso, Brazil, were monitored from January to December 2009 for mosquito eggs using ovitraps placed in high-traffic internal and external areas. RESULTS: A total of 2,302 eggs were obtained. Positivity rate at different sites ranged from 50.0% to 0.0%, with the highest indices in external areas. The presence of eggs correlated with increasing humidity (r = 9.81; p = 0.0013). DISCUSSION: The study aimed to detect and verify the infestation level of the dengue vector and the influence of abiotic factors. CONCLUSIONS: The results indicate that this hospital may be considered an environment for the spread of dengue and hence strategic actions, including control measures and programs aimed at preventing the transmission of this vector, must be implemented.

Temporal distribution of Aedes aegypti Linnaeus (Diptera, Culicidae), in a Hospital in Cuiabá, State of Mato Grosso, Brazil / Distribuição Temporal de Aedes aegypti Linnaeus (Diptera, Culicidae), em um Hospital de Cuiabá, Mato Grosso, Brasil

This study aimed at registering and monitoring the presence of Aedes aegypti in the University Hospital Júlio Muller, Cuiabá-MT, as well as investigating the influence of temperature and rainfall on its temporal distribution and egg densities in ovitraps. The study was performed from April/2007 to March/2008, utilizing ovitraps with 10 percent of hay infusion and a wood paddle as an oviposition substrate. For surveillance, one ovitrap was placed in each of the 12 points distributed throughout the hospital. Ovitraps were collected monthly at the end of a 5-day installation period. After egg counting, wood paddles were immersed in water to allow larval eclosion for species identification through optical microscopy. Egg Density Index (EDI), Positive Ovitraps Index (POI), and Mean Number of Eggs (MNE) were used for data analysis. The presence of A. aegypti in the hospital was registered throughout the study period, except in July. The MNE was proportionally higher in the internal area (n= 8.47 eggs/paddle) when compared to the external area (n= 5.46 eggs/paddle), and was higher in September/October 2007 and January/February 2008. A significant increase in EDI, POI and MNE was registered in periods where the average temperature was higher, and the increase in POI was also concomitant with an increase in rainfall. The continuous presence of A. aegypti in the hospital throughout the study period, points out the need of including this mosquito in the arthropod control list in this environment. This is particularly important, considering that A. aegypti is an important vector of several arboviroses.

Esse estudo objetivou registrar e monitorar a presença de Aedes aegypti no Hospital Universitário Júlio Muller, Cuiabá - MT, bem como investigar a influência da temperatura e pluviosidade sobre sua distribuição temporal e densidade de ovos em ovitrampas. O estudo foi realizado de abril/2007 a março/2008, usando ovitrampas com 10 por cento de infusão de gramínea e uma palheta de madeira como substrato para oviposição. Para o monitoramento, uma ovitrampa foi colocada em cada um dos doze pontos distribuídos nas dependências do hospital. Mensalmente, as armadilhas eram recolhidas ao final do quinto dia de instalação. Após a contagem dos ovos, as palhetas foram imersas em água para eclosão das larvas e identificação da espécie alvo em microscopia óptica. Índice de Densidade de Ovos (IDO), Índice de Positividade de Ovitrampas (IPO) e Número Médio de Ovos (NMO) foram usados para análise dos dados. A presença do mosquito no hospital foi registrada ao longo de todo experimento, exceto em julho. A densidade média de ovos foi proporcionalmente maior na área interna (n= 8,47 ovos/palheta) comparada à externa (n= 5,46 ovos/palheta). O NMO foi mais elevado nos meses de setembro e outubro de 2007, janeiro e fevereiro de 2008. Aumentos significativos do NMO, IPO e IDO, foram registrados com a elevação da temperatura, e no IPO com aumento da pluviosidade. A constante presença do mosquito A. aegypti no hospital, indica a necessidade de incluir esse mosquito na lista de controle de artrópodes nesse ambiente. Isso é particularmente importante, considerando que o A. aegypti é importante vetor de várias arboviroses.