Development of an urban molecular xenomonitoring system for lymphatic filariasis in the Recife Metropolitan Region, Brazil.

INTRODUCTION: Molecular xenomonitoring (MX)-pathogen detection in the mosquito rather than human-is a promising tool for lymphatic filariasis (LF) surveillance. In the Recife Metropolitan Region (RMR), the last LF focus in Brazil, Culex quinquefasciatus mosquitoes have been implicated in transmitting Wuchereria bancrofti parasites. This paper presents findings on the ideal mosquito collection method, mosquito dispersion, W. bancrofti infection in mosquitoes and W. bancrofti antigen in humans to aid MX development. METHODS: Experiments occurred within two densely populated urban areas of Olinda, RMR, in July and August 2015. U.S. Centers for Disease Control and Prevention (CDC) light traps were compared to battery-powered aspirators as collection methods, and mosquito dispersion was measured by mosquito mark release recapture (MMRR). Female Cx. quinquefasciatus were tested by PCR for W. bancrofti infection, and study area residents were screened by rapid tests for W. bancrofti antigen. RESULTS: Aspirators caught 2.6 times more total Cx. quinquefasciatus, including 38 times more blood-fed and 5 times more gravid stages, than CDC light traps. They also collected 123 times more Aedes aegypti. Of the 9,644 marked mosquitoes released, only ten (0.01%) were recaptured, nine of which were < 50m (34.8m median, 85.4m maximum) from the release point. Of 9,169 unmarked mosquitoes captured in the MMR, 38.3% were unfed, 48.8% blood-fed, 5.5% semi-gravid, and 7.3% gravid. PCR on 182 pools (1,556 mosquitoes) found no evidence of W. bancrofti infection in Cx. quinquefasciatus. Rapid tests on 110 of 111 eligible residents were all negative for W. bancrofti antigen. CONCLUSIONS: Aspirators were more effective than CDC light traps at capturing Ae. aegypti and all but unfed stages of Cx. quinquefasciatus. Female Cx. quinquefasciatus traveled short (< 86m) distances in this urban area. Lack of evidence for W. bancrofti infection in mosquitoes and antigen in humans in these fine-scale studies does not indicate that LF transmission has ceased in the RMR. A MX surveillance system should consider vector-specific collection methods, mosquito dispersion, and spatial scale but also local context, environmental factors such as sanitation, and host factors such as infection prevalence and treatment history.

Sustained reduction of the dengue vector population resulting from an integrated control strategy applied in two Brazilian cities.

Aedes aegypti has developed evolution-driven adaptations for surviving in the domestic human habitat. Several trap models have been designed considering these strategies and tested for monitoring this efficient vector of Dengue. Here, we report a real-scale evaluation of a system for monitoring and controlling mosquito populations based on egg sampling coupled with geographic information systems technology. The SMCP-Aedes, a system based on open technology and open data standards, was set up from March/2008 to October/2011 as a pilot trial in two sites of Pernambuco -Brazil: Ipojuca (10,000 residents) and Santa Cruz (83,000), in a joint effort of health authorities and staff, and a network of scientists providing scientific support. A widespread infestation by Aedes was found in both sites in 2008-2009, with 96.8%-100% trap positivity. Egg densities were markedly higher in SCC than in Ipojuca. A 90% decrease in egg density was recorded in SCC after two years of sustained control pressure imposed by suppression of >7,500,000 eggs and >3,200 adults, plus larval control by adding fishes to cisterns. In Ipojuca, 1.1 million mosquito eggs were suppressed and a 77% reduction in egg density was achieved. This study aimed at assessing the applicability of a system using GIS and spatial statistic analysis tools for quantitative assessment of mosquito populations. It also provided useful information on the requirements for reducing well-established mosquito populations. Results from two cities led us to conclude that the success in markedly reducing an Aedes population required the appropriate choice of control measures for sustained mass elimination guided by a user-friendly mosquito surveillance system. The system was able to support interventional decisions and to assess the program's success. Additionally, it created a stimulating environment for health staff and residents, which had a positive impact on their commitment to the dengue control program.

Expression of defensin, cecropin, and transferrin in Aedes aegypti (Diptera: Culicidae) infected with Wuchereria bancrofti (Spirurida: Onchocercidae), and the abnormal development of nematodes in the mosquito.

The temporal expression of defensin, cecropin and transferrin was assessed in Aedes aegypti naturally refractory to Wuchereria bancrofti upon infection with this worm, in parallel to analysis of filarial development in the insect. Compared to controls, transcription of defensin and cecropin was higher in infected mosquitoes as soon as 2h post infection and peaked before 48h. Transferrin transcription was higher in infected mosquitoes at 24h, and at 48h was almost leveled to controls. At 72h and 7 days post infection, levels of all transcripts in infected insects decreased gradually and were similar to controls in most cases. Worm development in A. aegypti was visually abnormal from the beginning of infection. Here, we report, for the first time, the up-regulation of endogenous immune molecules in A. aegypti infected with W. bancrofti and provide a description of the worm development inside the insect. The specificities of A. aegypti-W. bancrofti model compared to other mosquito-filaria systems are discussed.

Inheritance and mechanism of resistance to Bacillus sphaericus in Culex quinquefasciatus (Diptera: Culicidae) from China and Brazil.

Investigations on the inheritance and mechanism of resistance to Bacillus sphaericus Neide in Culex quinquefasciatus Say colonies, selected with strains C3-41 (RLCq1/C3-41) and 2362 (CqRL1/2362), were performed in China and Brazil, respectively. The progeny of reciprocal F1 crosses (susceptible female x resistant male and vice versa) from both resistant colonies responded alike in bioassays, indicating recessive inheritance. Data on larvae susceptibility from the backcross offspring between F1 and their respective susceptible and resistant parental colonies are consistent with a monofactorial and autosomal mode of inheritance. In vitro binding assays between 125I binary (Bin2) toxin and the brush border membrane fractions (BBMF) from CqRL1/2362 and RLCq1/C3-41 larvae showed that resistance, in both colonies, is caused by a failure in the binding step of the B. sphaericus Bin2 toxin to its specific midgut receptor. The specific and saturable binding of Bin2 toxin to BBMF from F1 larvae (CqRL1/2362 X susceptible counterpart) confirms the recessive inheritance of the resistance gene. Further studies are needed to advance understanding of B. sphaericus resistance.

Integrated control measures against Culex quinquefasciatus, the vector of filariasis in Recife

Integrated control measures against Culex quinquefasciastus have been implemented in a pilot urban area in Recife, Brazil. About 3,000 breeding sites found within the operational area were responsible for very high mosquito densities recorded during the pretrial period. Physical control measures have been applied to cess pits before starting a series of 37 treatments of the other sites with Bacillus sphaericus strain 2362, over 27 months. In spite of the difficulties due to environmental conditions, very significant reductions in preimaginal population of C. quinquefasciatus were achieved and, as a consequence, low adult mosquito densities were maintained for a relatively long period of time. Entomological and environmental data gathered in this pilot project can contribute to design an integrated mosquito control program in Recife city.