Assessing Entomological and Epidemiological Efficacy of Pyriproxyfen-Treated Ovitraps in the Reduction of Aedes Species: A Quasi-Experiment on Dengue Infection Using Saliva Samples

Abstract

Our study assessed the impact of using ovitraps with pyriproxyfen on mosquito populations and the feasibility of using human saliva samples to test for seroconversion to dengue virus (DENV). We used a quasi-experimental research design by forming the intervention (n = 220) and the control (n = 223) groups in neighboring Taguig City, Philippines, over 4 months. Socio-demographic data, entomological indices, and IgG antibodies against DENV were measured. Associations between the implementation of ovitraps dosed with pyriproxyfen and mosquito densities (percentage positive ovitraps and container indices) and DENV seroconversion were calculated post-intervention in Months 2, 3, and 4. Among the participants recruited at baseline, 17 and 13 were seropositive for dengue (DENV) in the intervention and control groups, respectively. Both entomological indices were lower in the treated area than the control site at post-intervention Months 2, 3, and 4, but not earlier. Dengue seroconversions rates decreased in the treated population, but not significantly so. In conclusion, the use of PPF-treated ovitraps may have impacted the mosquito population, but not seroconversion rates. Compliance in providing saliva samples and the ability to detect IgG antibodies within these samples was encouraging and suggests that further studies on larger populations for longer durations are warranted.

Efficacy Assessment of Autodissemination using Pyriproxyfen-Treated Ovitraps in the Reduction of Dengue Incidence in Two Barangays in Parañaque City, Philippines: A Spatial Analysis

“…In the Philippines, previous research tackled the use of AD-PPF in a small urban community in Metro Manila using a small sample size in which results showed that dengue seroconversion rates decreased in the treated population but not significantly so. The authors hypothesized that the use of PPF-treated ovitraps may have impacted the mosquito population but not the seroconversion rates [25]. Our study, which examined the pattern of the spatial distribution of DENV infection in two research sites in Parañaque City, may rectify the limitations seen from the previous AD-PPF research.…”

“…Individuals recruited for seroconversion were those within 200 meters of the household of the index dengue case and within 10 meters of the autodissemination and ovitrap stations. At the time of recruitment, AD-PPF devices (Ovitraps filled with 250 mL of water with one sachet of Sumilarv™ 0.5 G Sumitomo Chemical as previously described elsewhere [25]. were placed in the chosen households in the intervention study site houses.…”

“…aegypti to disseminate insecticide to natural larval habitats following exposure to a contaminated surface [22], a technique known as auto-dissemination (AD). This approach has been shown to be effective in reducing mosquito densities in several field trials [18,[23][24][25] through the use of pyriproxyfen (PPF), a synthetic analog of a juvenile growth hormone that has high potency at very low concentrations [18]. However, whilst the entomological efficacy of PPF has been demonstrated, measures of actual epidemiological impact (infection reduction) are generally inconclusive [26,27].…”

Efficacy Assessment of Autodissemination Using Pyriproxyfen-Treated Ovitraps in the Reduction of Dengue Incidence in Parañaque City, Philippines: A Spatial Analysis

“…Individuals recruited for seroconversion were those within 200 m of the household of the index dengue case and within 10 m of the autodissemination and ovitrap stations. At the time of recruitment, AD-PPF devices (Ovitraps filled with 250 mL of water with one sachet of Sumilarv™ 0.5 G Sumitomo Chemical as previously described elsewhere [ 28 ]) were placed in the chosen households in the intervention study site houses. In addition, traps without the PPF mixture were similarly deployed in the control site.…”

“…This concept was later adapted to control the mosquitoes that transmit DENV [ 25 ]. This approach has been shown to be effective in reducing mosquito densities in several field trials [ 26 , 27 , 28 ] through the use of pyriproxyfen (PPF), a synthetic analog of a juvenile growth hormone that has high potency at very low concentrations [ 29 ]. Most of these studies showed that AD occurred and successfully reduced the Aedes spp.…”