The research team collected Aedes aegypti mosquitoes from two contrasting environments: the densely urbanized metropolitan area of Kingston and the parish of St Andrew, referred to in the study as KSA, and the rural community of Lances Bay in the parish of Hanover. They also collected Aedes albopictus, the Asian tiger mosquito, from the urban KSA area to assess whether a second potential vector species shared the same vulnerability profile. Field-derived mosquitoes were then subjected to Centers for Disease Control and Prevention bottle bioassays, a standardized technique in which mosquitoes are exposed to a diagnostic dose of insecticide inside coated glass bottles and mortality is recorded over time. The CDC threshold for declaring a population susceptible requires mortality at or above 98 percent at the diagnostic time point, and by that measure every population tested failed, often spectacularly.

The numbers reveal the depth of the problem. At the 30-minute diagnostic time point, urban Aedes aegypti from KSA showed zero percent mortality to permethrin, meaning not a single mosquito was killed by the pyrethroid. Mortality to deltamethrin, another pyrethroid, stood at just 22.0 percent with a standard deviation of 2.7 percent, while malathion, an organophosphate, fared somewhat better at 70.5 percent with a standard deviation of 9.8 percent, still far below the susceptibility threshold. The rural Hanover population was, if anything, in worse condition: zero percent mortality to both permethrin and malathion, and only 8.1 percent mortality to deltamethrin. Aedes albopictus from KSA also demonstrated resistance to deltamethrin, with mortality below the CDC threshold, confirming that resistance is not confined to a single species.

What makes these results particularly concerning for public health officials is the multi-class nature of the resistance. Pyrethroids and organophosphates act through fundamentally different mechanisms: pyrethroids target voltage-gated sodium channels in insect neurons, while malathion inhibits acetylcholinesterase, an enzyme essential for nerve impulse termination. When a mosquito population simultaneously withstands compounds from both classes, control programs lose their two most important chemical tools at once. In Jamaica, where dengue outbreaks recur and ultra-low-volume spraying with pyrethroids is a mainstay of emergency response, the practical implications are immediate. Spraying campaigns that would have knocked down susceptible populations may now leave the majority of vector mosquitoes unharmed, while giving communities a false sense of protection.

To understand the molecular machinery behind this resistance, the researchers turned to transcriptomics, the study of gene expression patterns across the entire genome. They exposed Aedes aegypti collected from KSA to two compounds: malathion, the organophosphate already in use, and pyriproxyfen, an insect growth regulator belonging to a class of chemicals used to disrupt mosquito development. Using RNA sequencing, the team compared gene expression in exposed mosquitoes against untreated field mosquitoes and against the Rockefeller strain, a long-established insecticide-susceptible laboratory reference line. Principal component analysis and hierarchical clustering of the sequencing samples confirmed that the biological replicates grouped consistently by treatment, lending statistical confidence to the downstream comparisons.

The malathion results were striking. Exposure to the organophosphate triggered strong overexpression of genes associated with detoxification and with cuticle structure. Detoxification genes in mosquitoes typically include the three great enzyme families of insecticide metabolism: cytochrome P450 monooxygenases, glutathione S-transferases, and carboxylesterases, all of which can chemically modify or sequester toxic compounds before they reach their molecular targets. Cuticle-associated genes matter because the insect exoskeleton is the first barrier an insecticide must cross; a thicker or chemically altered cuticle can slow penetration and give internal detoxification systems time to neutralize the incoming dose. The coordinated upregulation of both gene categories suggests that Jamaican mosquitoes are mounting a layered defense, combining reduced uptake with enhanced metabolic breakdown.

Pyriproxyfen produced a different and more nuanced transcriptional signature. Rather than a concentrated detoxification response, the insect growth regulator elicited a moderate but broad response spanning metabolic and endocrine pathways. This pattern is biologically coherent: pyriproxyfen mimics juvenile hormone, a master regulator of insect metamorphosis, so exposure would be expected to perturb the expression of genes involved in hormone signaling and development alongside general metabolic machinery. The authors interpret these findings as evidence that transcriptional responses to insecticide exposure occur across multiple gene families rather than within a single pathway, a realization with important consequences for how resistance is monitored and predicted.

The transcriptomic dataset also included a comparison between the Rockefeller susceptible strain and untreated field-derived mosquitoes, capturing the baseline genetic differences that distinguish resistant Jamaican populations from their susceptible counterparts even before any laboratory exposure. Supplementary tables accompanying the paper document the significantly differentially expressed genes in each comparison, complete with log2 fold-change values, adjusted P-values, and normalized expression levels, providing a public resource for other researchers studying Caribbean vector populations. The study was supported by a Research and Publication Grant from the University of the West Indies, and the team included entomologists from the CDC’s Entomology Branch within the Division of Parasitic Diseases and Malaria, underscoring the international collaboration behind the work.

For the Caribbean region, the study arrives at a critical moment. Aedes aegypti is the principal urban vector of dengue virus, which causes periodic explosive outbreaks across the islands, as well as chikungunya and Zika, both of which swept through the Americas in the last decade. Resistance in Aedes aegypti has previously been documented in Jamaican urban and rural settings, but the susceptibility of other potential vector species and the transcriptional responses to insecticide exposure had remained poorly characterized. By showing that Aedes albopictus shares deltamethrin resistance with its more famous cousin, and by mapping the gene families involved, the study fills two significant gaps in regional surveillance knowledge. It also demonstrates that resistance profiles can differ dramatically between locations separated by only a few hundred kilometers, with the rural Hanover population showing even lower mortality than the urban KSA population for two of the three insecticides tested.

The authors conclude that insecticide resistance in Jamaican Aedes populations is widespread, heterogeneous, and dynamic, and they argue that these findings support locally informed resistance surveillance and integrated vector management strategies that go beyond reliance on pyrethroids. Integrated vector management, endorsed by the World Health Organization, combines chemical, biological, and environmental approaches, including source reduction through the elimination of standing water, larval control with agents less prone to resistance, and community engagement, reserving insecticides for targeted use where susceptibility still exists. The alternative, continuing to spray compounds to which local mosquitoes no longer respond, wastes scarce public health resources and accelerates the selection of even hardier mosquito populations. As dengue risk grows across a warming Caribbean, the Jamaican data serve as a warning that the chemical arsenal against Aedes mosquitoes is eroding, and that molecular surveillance of the kind performed in this study will be essential to staying ahead of the next outbreak.

Subject of Research: Insecticide resistance and resistance-associated gene expression in Jamaican Aedes mosquito populations

Article Title: Phenotypic insecticide resistance in Jamaican Aedes spp. and resistance-associated transcripts in Aedes aegypti

Article References: Tai, D., Irvine, W., Francis, F., Mackenzie-Impoinvil, L., Buchanan, L., Reimer, L., Lenhart, A., Roye, M., & Francis, S. (2026). Phenotypic insecticide resistance in Jamaican Aedes spp. and resistance-associated transcripts in Aedes aegypti. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07666-w

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07666-w

Keywords: Aedes aegypti, Aedes albopictus, insecticide resistance, Jamaica, pyrethroids, malathion, pyriproxyfen, transcriptomics, CDC bottle bioassay, dengue, vector control, Caribbean

Lymphatic filariasis, one of the world’s leading causes of permanent disability, results from infection with microscopic thread-like nematodes that lodge in the lymphatic system. In its chronic form the disease produces elephantiasis, the dramatic swelling of limbs and genitals that has made it one of the most feared and stigmatized of the neglected tropical diseases. The parasite is transmitted when mosquitoes ingest microfilariae—immature worms circulating in the bloodstream of an infected person—during a blood meal. Inside the mosquito, the parasites develop over roughly one to two weeks into third-stage larvae, the infective form that can migrate to the insect’s mouthparts and be deposited on human skin during the next bite. Nigeria carries a substantial share of the global burden of this disease, and mass drug administration campaigns have been rolled out across many endemic states. Yet as the Bodinga study makes clear, drug-based treatment alone cannot interrupt transmission if the entomological and behavioral environments remain unfavorable.

To assess community readiness for elimination, the researchers administered a semi-structured questionnaire to 258 participants across three wards of Bodinga, probing knowledge, attitudes, and practices related to lymphatic filariasis and mosquito control. The results were sobering. Only 41.9 percent of respondents had ever heard of lymphatic filariasis, and even fewer could correctly describe how it is transmitted or recognize its early symptoms. This knowledge gap matters for a practical reason: mass drug administration programs depend on high compliance rates, and communities that do not understand a disease—or the reason for taking preventive chemotherapy—are far less likely to participate fully in annual treatment rounds. Previous studies from other Nigerian states, including Kano, and from endemic regions of Brazil, Indonesia, and Guinea have documented similar deficits, suggesting that the Bodinga findings reflect a broader and persistent challenge in filariasis-endemic settings rather than a local anomaly.

The entomological half of the study focused on two mosquito genera with established roles in filariasis transmission: Anopheles, the same genus responsible for malaria, and Culex, particularly the ubiquitous Culex quinquefasciatus. Larvae were collected from breeding sites across the study area, reared to adulthood in the laboratory, and subjected to susceptibility testing with the Centers for Disease Control and Prevention bottle bioassay against three widely used pyrethroid insecticides: deltamethrin, permethrin, and alphacypermethrin. The outcome was unequivocal. Both Anopheles and Culex populations proved resistant to all three compounds, with mortality rates ranging from a mere 6 percent to 44 percent—far below the 98 percent threshold the World Health Organization uses to declare a population susceptible. For a region that relies heavily on insecticide-treated nets and indoor residual spraying, this level of resistance means that the primary chemical defenses against night-biting mosquitoes may offer little practical protection.

Digging into the mechanism of that resistance produced one of the study’s most operationally significant findings. When the researchers pre-exposed the mosquitoes to piperonyl butoxide, a chemical that inhibits the detoxification enzymes known as cytochrome P450 monooxygenases, susceptibility to alphacypermethrin was almost completely restored, with mortality rebounding to 98 to 99 percent. This synergist experiment demonstrates that metabolic detoxification—the mosquito equivalent of a chemical shield built from overactive detoxifying enzymes—underlies much of the observed resistance, rather than mutations in the insecticide’s target site on the nerve membrane. The practical implication is that intervention tools engineered around PBO synergism, such as the new generation of PBO-treated bed nets, could regain much of their lost efficacy in Bodinga and similar settings. The authors also quantified expression of two detoxification genes, CYP6M2 and CYP9M10, in infected versus uninfected mosquitoes, finding both significantly downregulated in parasite-carrying insects, at 0.26-fold and 0.77-fold respectively—an intriguing hint that filarial infection itself may alter the mosquito’s metabolic capacity, echoing transcriptomic changes previously reported in Anopheles infected with malaria parasites.

The third pillar of the study was molecular xenomonitoring, a surveillance technique that searches for parasite genetic material inside mosquitoes rather than in human blood. Because it requires no invasive testing of individuals and can detect transmission even when human infection rates have fallen below the threshold of blood-smear detection, xenomonitoring is increasingly viewed as the gold standard for determining whether elimination has truly been achieved. Using a Prokopack aspirator, the team collected blood-fed resting mosquitoes from indoor surfaces and screened a total of 1,510 specimens. Microscopic dissection detected microfilariae in five mosquitoes, a pool-level infection rate of 0.33 percent. Polymerase chain reaction then confirmed Wuchereria bancrofti DNA in three of these, or 0.20 percent of the total catch. Critically, quantitative reverse transcription PCR detected the parasite’s L3 larvae—the infective stage—in confirmed mosquitoes, indicating not merely passive carriage of parasite DNA but the presence of insects capable of transmitting the disease onward. Real-time PCR testing of microscopy-negative mosquito pools returned no additional infections, suggesting the infection rate is genuinely low but not zero.

That distinction between infection and infectivity carries real weight for program managers. A mosquito carrying only early-stage larvae may reflect residual parasites in a population that is already shrinking toward elimination, whereas the detection of L3-stage larvae signals active, onward transmission. In the WHO’s transmission assessment survey framework, districts are typically eligible to stop mass drug administration after several consecutive years when antibody prevalence in children falls low enough and there is no evidence of ongoing spread. The Bodinga results suggest that, despite low parasite rates, transmission has not yet been fully interrupted in this district, and that stopping interventions prematurely could allow the parasite to resurge. The authors argue that molecular xenomonitoring should be integrated routinely into Nigeria’s filariasis surveillance architecture precisely because it can capture this residual, near-invisible transmission in a way that conventional human-based surveys cannot.

The study’s One Health framing is what elevates it beyond a conventional parasitological survey. By simultaneously measuring human knowledge and behavior, vector susceptibility and resistance mechanisms, and parasite presence in the mosquito population, the researchers captured the interlocking vulnerabilities of the entire transmission system. Each component alone would have told an incomplete story. Low awareness without resistance data might have prompted a straightforward health education campaign; resistance findings without xenomonitoring might have overstated the risk; low infection rates without behavioral data might have encouraged premature relaxation of control efforts. Together, the data indicate that Bodinga requires a coordinated response: sustained community engagement to close the knowledge gap and boost drug compliance, a transition toward PBO-based vector control tools that bypass metabolic resistance, and continued molecular surveillance to track the parasite until transmission is demonstrably halted.

The researchers, funded through the Africa Centre of Excellence for Neglected Tropical Diseases and Forensic Biotechnology with clearance from the Sokoto State Ministry of Health, recommend targeted awareness campaigns as the immediate priority, alongside expanded studies of resistance mechanisms to determine whether other pathways, such as target-site mutations or cuticular changes, also contribute alongside the confirmed metabolic component. They also note that the downregulation of CYP6M2 and CYP9M10 in infected mosquitoes raises questions about how filarial parasites interact with their vector’s detoxification machinery, an area that may deserve deeper investigation given its potential to influence both insecticide susceptibility and parasite development simultaneously.

For the global elimination campaign, which has already achieved remarkable success in countries across Asia, the Pacific, and parts of Africa, the Bodinga study offers both a warning and a template. The warning is that elimination progress can stall in districts where resistant vectors and unaware populations coexist, leaving a stubborn reservoir of transmission beneath the surface. The template is the integrated, One Health study design itself: a relatively low-cost combination of questionnaire surveys, standardized bioassays with synergist testing, and PCR-based xenomonitoring that can be deployed by national programs to identify precisely where and why transmission persists. As Nigeria pushes toward the 2030 global elimination target, studies of this kind may prove indispensable for distinguishing communities that are ready to stop treatment from those where the fight must continue.

Subject of Research: Community knowledge, pyrethroid resistance, and molecular xenomonitoring of Wuchereria bancrofti in lymphatic filariasis-endemic communities of Sokoto State, Nigeria

Article Title: Integrating Community Practices, Vector Resistance, and Molecular Xenomonitoring of Wuchereria Bancrofti: A One Health Implementation Study in Lymphatic Filariasis–Endemic Communities

Article References: Yalwa, M. A., Aliyu, M., Musa, A. I., Malami, I., Abubakar, M. B., Ndams, I. S., & Muhammad, A. (2026). Integrating Community Practices, Vector Resistance, and Molecular Xenomonitoring of Wuchereria Bancrofti: A One Health Implementation Study in Lymphatic Filariasis–Endemic Communities. Acta Parasitologica, 71(5), Article 218. https://doi.org/10.1007/s11686-026-01401-2

Image Credits: AI Generated

DOI: 10.1007/s11686-026-01401-2

Keywords: lymphatic filariasis, Wuchereria bancrofti, molecular xenomonitoring, insecticide resistance, pyrethroids, piperonyl butoxide, cytochrome P450, Anopheles, Culex quinquefasciatus, neglected tropical diseases, One Health, Nigeria