Review of climate, landscape, and viral genetics as drivers of the Japanese encephalitis virus ecology.

The Japanese encephalitis virus (JEV), an arthropod-born Flavivirus, is the major cause of viral encephalitis, responsible for 10,000-15,000 deaths each year, yet is a neglected tropical disease. Since the JEV distribution area has been large and continuously extending toward new Asian and Australasian regions, it is considered an emerging and reemerging pathogen. Despite large effective immunization campaigns, Japanese encephalitis remains a disease of global health concern.

Elevated Japanese encephalitis virus activity monitored by domestic sentinel piglets in Thailand.

Twenty-nine domestic piglets from pig farms located in three provinces of Thailand between 2003 and 2004 were used as sentinel animals for Japanese encephalitis virus (JEV) circulation. Piglets were used as sentinel to underline, on one hand, the role of domestic pigs as JEV amplifying host and, on another hand, to point out the interest of using sentinel animals for Japanese encephalitis surveillance. JEV activity was demonstrated through i/ antibody detection using a specific ELISA test for the identification of Immunoglobulins of class M and G, ii/ virus isolation on cell culture, after experimental mosquito inoculation for virus amplification.

Modelling the effect of temperature on transmission of dengue.

The main entomological parameters involved in the rate of dengue virus transmission include the longevity of female mosquitoes, the time interval between bites and the extrinsic incubation period of the virus. Field and laboratory data provide estimates for these parameters, but their interactions with other factors (e.g.

Reducing costs and operational constraints of dengue vector control by targeting productive breeding places: a multi-country non-inferiority cluster randomized trial.

Objectives: To test the non-inferiority hypothesis that a vector control approach targeting only the most productive water container types gives the same or greater reduction of the vector population as a non-targeted approach in different ecological settings and to analyse whether the targeted intervention is less costly.

Methods: Cluster randomized trial in eight study sites (Venezuela, Mexico, Peru, Kenya, Thailand, Myanmar, Vietnam, Philippines), with each study area divided into 18-20 clusters (sectors or neighbourhoods) of approximately 50-100 households each. Using a baseline pupal-demographic survey, the most productive container types were identified which produced >or=55% of all Ae.

Change in Japanese encephalitis virus distribution, Thailand.

Japanese encephalitis virus (JEV) genotypes in Thailand were studied in pigs and mosquitoes collected near houses of confirmed human JEV cases in 2003-2005. Twelve JEV strains isolated belonged to genotype I, which shows a switch from genotype III incidence that started during the 1980s.

Detection of host virus-reactive antibodies in blood meals of naturally engorged mosquitoes.

Although serosurvey in human or animals is a useful and straightforward strategy routinely used for public health, it often faces different types of impediments: ethics, beliefs, limitation by animal owners, hazard of access to wild animals. To survey virus circulation, we applied the enzyme-linked immunosorbent assay (ELISA) technique to detect Dengue and Japanese encephalitis (JE) virus-reactive antibodies in blood meals collected from mosquitoes without regard to the potential of mosquito species to be a virus vector. ELISA was performed on mosquito colonies and wild specimens collected from farms and urban areas.

The value of the freshwater snail dip scoop sampling method in macroinvertebrates bioassessment of sugar mill wastewater pollution in Mbandjock, Cameroon.

Macroinvertebrates identification and enumeration may be used as a simple and affordable alternative to chemical analysis in water pollution monitoring. However, the ecological responses of various taxa to pollution are poorly known in resources-limited tropical countries. While freshwater macroinvertebrates have been used in the assessment of water quality in Europe and the Americas, investigations in Africa have mainly focused on snail hosts of human parasites.

Assessment of a new strategy, based on Aedes aegypti (L.) pupal productivity, for the surveillance and control of dengue transmission in Thailand.

In the countries where the disease is endemic, control of dengue is mainly based on the elimination or treatment of the water-filled containers where the main vector, Aedes aegypti, breeds, in interventions usually reliant on community participation. Although such control activities must be continuous, since vector eradication appears impossible, it should be possible to reduce the incidence of dengue significantly, in a cost-effective manner, by targeting only those types of containers in which large numbers of Ae. aegypti are produced.

Detection of H5N1 avian influenza virus from mosquitoes collected in an infected poultry farm in Thailand.

Blood-engorged mosquitoes were collected at poultry farms during an outbreak of highly pathogenic avian influenza in Central Thailand during October 2005. These mosquitoes tested positive for H5N1 virus by reverse transcription-polymerase chain reaction (RT-PCR). Results were confirmed by limited sequencing of the H5 and N1 segments.

Synthesis and characterization of new trimeric rhenium(I) complexes. The influence of steric factors on the size of pyrazolonaterhenium(I) metallomacrocycles.

The reaction of [ReX(CO)5] with thiosemicarbazones H2L(R) derived from beta-keto esters (X = Cl, Br; R = Me, Ph) allowed the isolation of cyclic trimeric complexes [Re3(pyz(R))3(CO)9], where pyz(R) is the pyrazolonate corresponding to the thiosemicarbazone. Electron spray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) monitoring of the reactions of H2L(Ph) in toluene confirmed that the trimer was formed in the reaction mixture and no higher oligomer was detected. These studies, together with the X-ray structures of the trimeric complexes, afford new insight into the factors influencing the self-assembly of pyrazolonaterhenium(I) complexes.

Sample sizes for identifying the key types of container occupied by dengue-vector pupae: the use of entropy in analyses of compositional data.

A method has been developed for estimating the sample sizes needed to identify categories that comprise a large proportion of a compositional data-set. The method is to be used in the design of surveys of mosquito pupae, for identifying the key container types from which the majority of adult dengue vectors emerge. Although a finite-population correction was devised for estimating the mean of a negative binomial distribution, other complications of parametric approaches make them unlikely to yield methods simple enough to be practically applicable.

First isolation of Japanese encephalitis from Culex quinquefasciatus in Thailand.

Isolation of Japanese encephalitis (JE) virus using C6/36 cell and immunofluorescence virus antigen detection techniques was attempted from female mosquitoes collected with CDC gravid traps in Samut Songkhram Province in the central region and in Phuket Province in southern Thailand, in 2003. One thousand and eighty female mosquitoes including 6 species of the Culicidae family (Culex quinquefasciatus, Cx. gelidus, Cx.

Seroepidemiological survey among schoolchildren during the 2000-2001 dengue outbreak of Ratchaburi Province, Thailand.

From August 2000 to 2001, a dengue outbreak occurred in Mueang district, Ratchaburi Province, Thailand. About 800 cases of dengue infection were reported, and among them, 49.5% were clinically diagnosed as dengue hemorrhagic fever according to the WHO criteria.

Geographic dynamics of viral encephalitis in Thailand.

Viral encephalitis (VE) continues to be a major disease in Asia, causing serious illness which may result in death or have neurological sequelae. This study involves an ecological analysis of the climatic, geographic and seasonal patterns of clinically reported VE in Thailand from 1993 to 1998 to investigate regional and seasonal differences in disease incidence. Three thousand eight hundred and twenty nine cases of VE were clinically diagnosed nationwide during the study period by the Thai Ministry of Public Health.

Hantaan virus antibody prevalence in rodent populations of several provinces of northeastern Thailand.

We conducted a serological survey of 632 rodents from the northeast region of Thailand in order to assess the presence of Hantaan-like viruses that may be a risk to the human population. Rodents were collected from rice fields, houses and domestic gardens in five northeastern provinces and tested for IgG reacting sera to Hantaan antigen using enzyme-linked immunoassays. The overall prevalence of Hantavirus infection in rodents was 2.

Dengue hemorrhagic fever epidemiology in Thailand: description and forecasting of epidemics.

Despite the use of a variety of control strategies, dengue hemorrhagic fever (DHF) control is a major and permanent challenge for public health services in Thailand and in Southeast Asia. In order to improve the efficiency of DHF control in Thailand, these activities have to concentrate on areas and populations at higher risk, which implies early identification of higher incidence periods. A retrospective study of spatial and temporal variations of DHF incidence in all 73 provinces of Thailand (1983-1995) allowed discrimination between seasonal (endemic) transmission dependent on climatic variations and vector density and non-seasonal (epidemic) transmission, mainly due to the occurrence of a new virus serotype in a population with low immunity.

[An experimental model to analyse the characteristics of a strain of Culex pipiens and its sensitivity to insecticides].

This study, based on phenotype of green larvae colour, has enabled the selection of a genetically distinct line of Culex pipiens pipiens. The four loci under study were found to be homozygous to the 42nd generation. These loci were associated with an increased sensitivity to organochlorides in the progeny when compared to the parent strain.

[Geographic determinants of onchocerciasis transmission in a forest-savannah transition zone: an example of 2 villages of the Mbam focus (central region, Cameroon)].

Mbam, a focus of onchocerciasis outbreaks, is located in the forest/savannah transition zone of Cameroon. Transmission of the disease in this area is similar to that sometimes observed in West Africa. Geographical factors affecting transmission must be identified to determine the areas for priority action.

[Geographical determinants of onchocerciasis transmission in a forest/savannah transition zone : two villages of the mbam focus].

Mbam, a focus of onchocerciasis outbreaks, is located in the forest/savannah transition zone of Cameroon. Transmission of the disease in this area is similar to that sometimes observed in West Africa. Geographical factors affecting transmission must be identified to determine the areas for priority action.

[Entomologic study on the transmission of onchocerciasis in a forest-savanna transition area of Cameroon].

An entomological study was conducted in the basin area of middle Sanaga (Cameroon) in order to document the pattern of onchocerciasis transmission in a region where a high prevalence of infection had been recorded in villages located 30 km from the main rivers. The main vector of O. volvulus was found to be S.

Impact of treatments with Bacillus sphaericus on Anopheles populations and the transmission of malaria in Maroua, a large city in a savannah region of Cameroon.

Simultaneously with a control of breeding sites primarily for Culex quinquefasciatus and secondarily for anophelines with Bacillus sphaericus in the town of Maroua (120,000 inhabitants) in North Cameroon, a survey of anopheline populations and of transmission rates of malaria was performed. Monthly night catches in 8 districts of the town emphasized the relation between the biting rate by Anopheles in the districts and two main factors. One factor was the distance of a district from the breeding sites, i.

Control of Culex quinquefasciatus (Diptera: Culicidae) with Bacillus sphaericus in Maroua, Cameroon.

Two strategies were tested to control Culex quinquefasciatus with Bacillus sphaericus in Maroua (population 130,000), Cameroon. The treatment of all potential breeding sites (27,000) with B. sphaericus during the dry season caused up to a 90% reduction in the adult biting rate.