Biology subjects

Warusawithana, A. L.

Publications and source records attributed to Warusawithana, A. L..

3 recordsLinked to original sources

bioRxiv2026

Efficacy of 60 personal mosquito repellents and perfumes against Aedes aegypti mosquitoes

Personal insect repellents can offer an effective means of preventing mosquito bites. Despite a wide variety of products that claim to repel mosquitoes, relatively few studies have systematically compared their performance through standardized tests. In Australia, chemical-based repellents must be registered with the Australian Pesticides and Veterinary Medicines Authority (APVMA); however, many unregistered products with unverified effectiveness remain commercially available. Here, we tested 55 insect repellents and 5 non-repellent perfumes and deodorants sold in Australia for their protection against Aedes aegypti mosquito landings (as a proxy for bites) using arm-in-cage assays across eight human subjects. We tested 43 topical repellents (containing 18 different primary active ingredients), four wristbands, three clothing stickers, three ultrasonic devices, one garment, one repellent applied to fabric, two perfumes, two deodorants and one antiperspirant. Thirteen repellents, including all wristbands, stickers and ultrasonic devices did not provide complete protection against mosquito landings for any human subject, while a further sixteen provided complete protection for 1 hr or less on average. Repellents containing DEET, oil of lemon eucalyptus, picaridin and IR3535 as the primary active ingredient were the only products that provided more than 2 hours of complete protection, but with significant variation among products with the same active ingredient. Only 7/30 essential oil-based topical repellents and perfumes provided complete protection for greater than 1 hr. Nearly half (25/52) of the repellents subject to registration with the APVMA were unregistered despite being advertised or labelled as mosquito repellents, and these tended to be less effective than registered products. Only 5/28 repellents met or exceeded their claimed protection time. This study highlights the prevalence of unregistered and ineffective mosquito repellents on the Australian market while providing evidence for products and active ingredients that do protect against mosquito bites under laboratory conditions.

zoology↗

bioRxiv2026

Mosquito fertility is (mostly) resilient to sublethal heat shocks

Insects can experience a loss of fertility under acute heat stress, but impacts vary among species and depend on life stage and sex. We examined the effects of sublethal heat shocks on the fertility of three mosquito species (Aedes aegypti, Aedes notoscriptus and Culex quinquefasciatus) when males or females were exposed at the pupal and adult stages. Reproductive performance was assessed through egg-laying success, fecundity, egg hatchability and viable offspring production. Female heat shock had limited effects on fertility in all three species, though exposure of adult females to 41 {degrees}C for 1 hr reduced viable offspring production in Ae. notoscriptus. Male heat shock reduced egg hatchability in Cx. quinquefasciatus and viable offspring production in Ae. aegypti depending on the life stage exposed. We investigated several other aspects of heat shock exposure on Ae. aegypti fertility. In this species, male fertility partially recovered within 24-48 hours following heat shock exposure, while effects of heat shocks on female fertility occurred regardless of whether heat exposure occurred pre- or post-mating. In addition, maternal heat shock exposure enhanced offspring fecundity and viable offspring production under subsequent sublethal heat stress. Overall, our findings demonstrate that mosquito fertility is largely robust to short-term heat shocks, but there are also complex trait, sex, stage, temporal and species-specific effects, with implications for predicting mosquito population persistence and species persistence under future climate extremes.

zoology↗

bioRxiv2025

Heat hardening enhances mosquito heat tolerance in a species-specific and trait-specific manner

Models predict that the distribution of ectotherms including mosquitoes will shift with climate change, but few incorporate adaptive capacity. Acclimation is one mechanism by which mosquitoes could adapt, allowing mosquitoes that have experienced sub-lethal stress previously to tolerate subsequent stressful environments. In this study we evaluated the heat tolerance of three vector mosquito species, Aedes aegypti, Ae. notoscriptus and Culex quinquefasciatus, after being previously exposed to heat hardening. Adult males and females were heat-hardened by exposure to 41{degrees}C for one hour and subsequently tested for heat survival and knockdown following one-hour heat shocks across a range of temperatures up to the lethal limit, ramping CTmax assays and static temperature knockdown time assays. The three species differed markedly in their heat tolerance across all assays, with Ae. aegypti being the most heat tolerant and Cx. quinquefasciatus being the least. Females from all three species were more heat tolerant than males in the one-hour heat shock assays, but effects of sex were absent or inconsistent for CTmax and heat knockdown time assays. A beneficial impact of heat hardening on subsequent heat shock knockdown was evident in both sexes of all three species. However, hardening effects differed substantially for survival 24 hr later, ranging from no effect of hardening in Cx. quinquefasciatus to a [~]1{degrees}C increase in LT50 in Ae. notoscriptus. In contrast, no effects of heat hardening were detected for CTmax or static knockdown time assays. An additional experiment in Ae. aegypti detected no benefits of heat shock exposure in female patents on the thermal tolerance of offspring. Our findings emphasize the need to consider effects of acclimation including heat hardening in models to predict the response of mosquitoes to climate warming. They also have implications for measuring thermal tolerance in mosquitoes more generally, given that both sex and hardening effects depend on the type of assay used and trait measured.

ecology↗