The significance of the work lies in what mangroves represent for public health. Although mangrove forests cover only about 700 square kilometres of French Guiana, less than one percent of the territory, they occupy more than 80 percent of its coastline. That same coastal strip is home to 90 percent of the human population of this French overseas department, including the capital city of Cayenne. Wherever people and mosquitoes overlap, questions about nuisance biting and disease transmission follow, and until now, data on the mosquitoes of these intertidal forests were remarkably sparse.

French Guiana is, in many ways, the right place to look. The territory is recognised as having one of the highest mosquito species richness in the world relative to its surface area, with 250 recorded species. Earlier georeferenced databases, compiled by entomologists in the 1960s and 1970s and updated in 2015, catalogue valuable biodiversity records, but their structure does not allow researchers to analyse how species assemblages and relative abundances vary across space and time. The new dataset was designed precisely to fill that gap, using standardised sampling events so that future comparisons among habitats and seasons become possible.

The fieldwork stretched from October 2023 to July 2025 and covered 14 locations. Most sat on the Island of Cayenne and its surroundings, a stretch of roughly 50 kilometres of coast and 25 kilometres inland that includes six municipalities. A second cluster of sites lay about 100 kilometres southeast, along the lower Oyapock River on the border with Brazil, in a 30-kilometre upstream and downstream transect between the villages of Trois-Palétuviers and Ouanary. The sites spanned young pioneer mangroves barely a year old, mature homogeneous stands dominated by a single tree species, and structurally complex mixed forests, some within sight of Cayenne’s urban centre and others more than 10 kilometres from any human infrastructure.

Sampling relied primarily on two complementary trap types. BG-Pro traps baited with BG-Sweetscent lures, sometimes paired with ultraviolet light, are known to be effective at capturing mosquito species that prefer to feed on humans. CDC light traps, suspended about 1.5 metres above the ground along transects of 30 to 60 metres, sample a broad diversity of nocturnal species. Traps typically ran for 8 to 9 hours during daytime deployments or around 16 hours overnight, with occasional continuous 24-hour sessions when logistics prevented immediate retrieval. Two larval dipping events added 64 immature specimens to the tally, a tiny fraction of the total but a deliberate inclusion, since locating larvae is one of the few ways to identify which parts of the mangrove actually serve as breeding habitat.

Identifying tropical mosquitoes is notoriously difficult, and the researchers went to unusual lengths to get the names right. No single identification key covers all the mosquito species recorded in French Guiana, so the team combined multiple taxonomic keys, one for each genus, following nomenclature updated through the Mosquito Taxonomic Inventory. Most species of the genus Culex simply cannot be identified reliably from external adult features, so the team examined the internal structures of male genitalia for 1,762 male Culex specimens, 98 percent of all Culex males in the dataset. The abdominal segments were cleared in potassium hydroxide, stained with acid fuchsin, and in 100 difficult cases fully dissected and mounted on slides for microscopic examination at up to 1000-times magnification.

Molecular tools provided a further layer of confidence. For uncertain identifications, the researchers removed three legs from selected specimens and stored them for DNA barcoding of the standard 658-base-pair region of the mitochondrial cytochrome c oxidase subunit I gene, the COI barcode widely used in animal taxonomy. A total of 400 female mosquitoes and 50 male Culex were confirmed this way, with sequences compared against an existing DNA reference library dedicated to the mosquitoes of French Guiana. All barcode sequences will be deposited in the Barcode of Life Data System under the ongoing Mosquitoes of French Guiana project, and voucher specimens are preserved in ethanol or mounted in the entomological collection of the Institut Pasteur de la Guyane.

The results reveal a mosquito fauna strongly dominated by a handful of taxa. Unidentified Culex of the subgenus Melanoconion topped the list with 8,580 specimens, or 39.4 percent of the total, followed by Coquillettidia venezuelensis with 4,471 specimens at 20.5 percent, the crab-hole mosquito Deinocerites magnus with 3,354 specimens at 15.4 percent, and Culex portesi with 1,496 specimens at 6.9 percent. Together, these four taxa accounted for 82.2 percent of everything collected and occurred at most of the sampling sites. That a few species so thoroughly dominate the catch, while dozens of others appear only rarely, is itself ecologically informative, hinting at how tightly many tropical mosquito species are adapted to particular microhabitats within the mangrove mosaic.

The authors are candid about the dataset’s limits. Because it combines a standardised repeated survey, a structured but less replicated river transect, and a set of exploratory and opportunistic collections, sampling effort was not homogeneous across all sites. Roughly two-thirds of all collection events came from the standardised design, providing a robust core for comparison, but the team advises that any comparative analysis be restricted to subsets collected under comparable protocols. Trap biases are also acknowledged: light traps and scent-baited traps each miss part of the fauna, and some taxa will inevitably remain underrepresented no matter how diverse the toolkit. Environmental conditions, from tidal flooding and freshwater flushing to stand age and salinity, vary across mangrove habitats and shape which salt-tolerant species thrive where.

Why should the wider public care about an insect inventory in South American swamps? Mangroves worldwide are recognised both as nurseries for pest and arbovirus-carrying mosquitoes and, paradoxically, as sometimes poor larval habitats, since frequent tidal flushing can wash out eggs and larvae before they complete development. Understanding which side of that balance a given mangrove occupies, and which species dominate it, directly informs assessments of public health risk and the design of management strategies for coastal zones under pressure from urbanisation and climate change. By releasing the dataset as fully documented sampling events, complete with georeferenced coordinates, trap metadata, specimen identifiers, DNA barcodes and dissected voucher material, the researchers have transformed a regional entomological campaign into an open, reusable scientific resource. For a territory where 250 mosquito species share a coastline with nearly the entire human population, that kind of traceable baseline is not a luxury. It is the foundation on which every future question about mosquitoes, mangroves and disease in the Guianas will be built.

Subject of Research: Ecology and diversity of Neotropical mosquito assemblages in mangrove habitats of French Guiana

Article Title: A mangrove-based dataset to study the ecology of Neotropical mosquitoes ( Diptera , Culicidae ) in French Guiana

Article References: Collet, M., Proisy, C., Talaga, S., Guidez, A., Vlandis, I., Keovongsack, A., Carinci, R., Gaborit, P., Davy, D., & Duchemin, J.-B. (2026). A mangrove-based dataset to study the ecology of Neotropical mosquitoes (Diptera, Culicidae) in French Guiana. ZooKeys, 1290, 227-239. https://doi.org/10.3897/zookeys.1290.189084

Image Credits: AI Generated

DOI: 10.3897/zookeys.1290.189084

Keywords: mosquitoes, Culicidae, mangroves, French Guiana, biodiversity dataset, DNA barcoding, Culex, vector ecology, Neotropical, entomology, sampling-event data, arboviruses

Blackflies, the family Simuliidae, are among the most consequential blood-feeding arthropods in the temperate world. Female blackflies feed on the blood of mammals and birds, and their bites can trigger severe reactions in people and animals alike. In tropical Africa, South America and Yemen, certain species transmit the parasitic worm that causes human onchocerciasis, better known as river blindness. Europe has so far been spared major human parasites carried by blackflies, but the continent’s species are confirmed vectors of avian haemosporidian parasites and are considered potential carriers of Bartonella bacteria and zoonotic filarial nematodes. Their most notorious impact, however, remains agricultural: historical accounts document cattle mortality during mass outbreaks, with daily biting rates on cattle commonly ranging from ten to more than a thousand bites per animal.

The historical heavyweight of European biting flies was Simulium colombaschense, which once bred in staggering numbers in the middle reaches of the Danube, particularly in the Iron Gates gorge. Its populations collapsed after the Iron Gates Dams were built in the 1970s, and the species has not been detected in that stretch of the river in recent decades. Yet seasonal biting outbreaks persist across Europe, and annual biting rates of 15,000 to 50,000 bites per year were documented on horses in earlier studies. Beyond their nuisance value, blackfly larvae filter organic particles from flowing water and form a significant link in aquatic food webs, especially in boreal streams, a role the authors argue is underestimated even within hydrobiological research.

The new inventory was built through a two-stage workflow that treated every published record as a claim to be tested rather than a fact to be copied. The researchers first compiled a raw data pool of 268 species-level taxa reported from Europe, drawing primarily on three key comprehensive sources: the annually revised world inventory of blackflies, the Fauna Europaea dataset, and the Catalogue of Palaearctic Diptera. Where these secondary compilations conflicted or left ambiguities, the team went back to primary faunistic and taxonomic studies, digitising printed sources and disaggregating them into individual species records tied to defined geographic units.

Filtering then removed everything that could not stand on formal nomenclatural ground. Two morphoforms and five cytoforms, including one hypothetical species, were excluded because they carry only informal designations and lack the formal names required by the International Code of Zoological Nomenclature. Two nomina nuda, names published without adequate description, were also struck out. One of them, Simulium anomalum, described by Eversmann in 1834, was accompanied by no description at all. The other, Simulium laticornis, exists only as an attributed personal communication that was never formally published by its supposed author. Both fail the Code’s requirements and cannot legitimately appear on any species list.

Two species were simultaneously brought back from synonymy. Simulium annulipes and Simulium beckeri, both originally described in the early twentieth century from the Mediterranean and Macaronesian region, had recently been treated as synonyms of the widespread Simulium ruficorne. Chromosomal evidence published in 2018 showed that the European cytoforms of the ruficorne complex form distinct clades from their Afrotropical relatives, supporting their recognition as separate species. The authors acknowledge that the latest evidence recommends caution, but argue that keeping the two named species distinct is pragmatically easier than trying to untangle distributional data later if synonymy is eventually confirmed. In a separate reassessment, the form previously treated as Simulium aff. tuberosum was merged into Simulium janzeni, consistent with earlier morphological work, though the European members of the tuberosum group still await a full revision.

From the resulting core set of 261 species, the audit applied two decisive criteria: nomenclatural validity under the ICZN, and reliably confirmed occurrence in Europe. Species meeting both tests entered the List of accepted species, which now stands at 233 taxa. Sixteen of these are recognised as species complexes, meaning the true number of European species is likely higher than the count suggests. The accepted list is sensitive to where Europe’s eastern boundary is drawn: if the Manych Depression is taken as the limit and the northern Caucasus excluded, the total drops by 14 species, three of them Caucasian endemics whose ranges do not extend further into Europe.

The remaining 28 species form the List of questionable species, and their stories illustrate how taxonomic doubt accumulates. Several rest entirely on a single Romanian record from 1966 whose descriptions were copied from an older Russian monograph rather than based on the author’s own specimens, with pupal characters that either vary too widely among related species or contradict the original descriptions outright. Others hinge on records more than half a century old from the Balkans or northern Russia that have never been reconfirmed. In one striking case, a species described from the semi-desert rivers of Mongolia was reported from both large lowland rivers and small spring streams in Ukraine, an ecological implausibility compounded by morphological discrepancies, leading the authors to exclude it despite its traditional presence in recent national checklists.

The audit also challenges the growing reliance on short mitochondrial DNA barcodes alone. Records of Simulium turgaicum from Slovenia, Bosnia and Herzegovina and Czechia rest solely on partial COI sequences, yet three closely related species in the same group show very similar barcodes, and published phylogenetic trees built from this gene fail to recover the species as distinct lineages. The authors argue that a single mitochondrial gene fragment cannot be accepted as reliable evidence of a species’ presence, particularly given the likelihood of incomplete lineage sorting or hybridisation among closely related blackflies. Molecular evidence, they contend, must be weighed alongside morphology and cytogenetics rather than replacing them.

The broader picture that emerges is one of a predominantly Palaearctic fauna with deep biogeographic roots. Of the 2,415 blackfly species recognised worldwide, Europe hosts less than ten percent. Some 133 accepted species, 57.1 percent, are shared with other continents, while 100 species, 42.9 percent, are endemic to Europe, ranging from widespread continental species to narrow island endemics such as a species confined to Corsica and another known only from Sardinia. Iceland harbours just two species, both shared with Asia. Twenty-five species, 10.7 percent, are shared with North America as remnants of a Holarctic distribution, and 39 species link Europe with Palaearctic Africa. By publishing both the accepted and the questionable lists with explicit criteria and case-by-case rationales, the revision gives ecologists, public health researchers and conservation planners a transparent baseline, while clearly marking where future fieldwork and museum detective work are most needed.

Subject of Research: Taxonomic inventory and revision of European blackfly species (Diptera: Simuliidae)

Article Title: European blackflies: accepted and questionable species ( Diptera , Simuliidae )

Article References: Jedlička, L., Kúdela, M., & Kúdelová, T. (2026). European blackflies: accepted and questionable species (Diptera, Simuliidae). ZooKeys, 1291, 251-281. https://doi.org/10.3897/zookeys.1291.196803

Image Credits: AI Generated

DOI: 10.3897/zookeys.1291.196803

Keywords: blackflies, Simuliidae, taxonomy, species checklist, Europe, biodiversity, ZooKeys, nomina nuda, cytoforms, vector ecology, faunistics, ICZN

The research team, led by Joseph Gichuhi and Jeremy Keith Herren at the International Centre of Insect Physiology and Ecology in Nairobi, set out to answer a deceptively simple question: at what spatial scale does Microsporidia MB prevalence vary? Previous work had shown that prevalence differs across regions of Kenya more than 100 kilometers apart, ranging from 1 to 9 percent in An. arabiensis. But if the microbe’s prevalence swung wildly from village to village, or even from house to house, a symbiont-based control strategy could falter before it ever reached scale. The team needed to know whether local ecological differences could undermine the microbe’s stability.

To find out, the researchers conducted simultaneous longitudinal sampling in two contrasting agroecosystems just 8 kilometers apart: Ahero, an irrigated rice scheme, and Miwani, a non-irrigated sugarcane-growing zone. Both areas are known malaria hotspots, but they differ dramatically in hydrology, vegetation, and microclimate. The team selected 10 sentinel houses per area and collected indoor-resting mosquitoes early in the morning using CDC backpack aspirators over 15 sampling rounds between May 2023 and February 2024, capturing the Long Rains, Short Rains, and Dry Season. Larval surveys from temporary rain-fed pools ran in parallel. Every mosquito was screened by PCR for both Microsporidia MB and Plasmodium, and the team correlated abundance and infection rates with remotely sensed environmental variables including vegetation greenness, rainfall, humidity, temperature, and wind speed.

The first striking finding was ecological. Both areas harbored similar Anopheles species pools dominated by An. arabiensis, An. gambiae sensu stricto, and An. funestus, the three principal malaria vectors of East Africa. Larval surveys mirrored this composition, though An. funestus was absent from the sampled pools. But abundance told a very different story. The irrigated rice scheme supported a seven-fold greater Anopheles population than the sugarcane zone, with 2,525 mosquitoes collected in Ahero compared to just 349 in Miwani. This strong spatial heterogeneity in vector density, driven purely by location and irrigation, is exactly the kind of landscape variation that could theoretically disrupt a symbiont’s transmission dynamics.

Yet Microsporidia MB refused to follow that pattern. The symbiont was detected across both areas in all three major vector species and in other uncharacterized Anopheles species, with prevalence ranging from 2 to 15.6 percent. Statistical analysis confirmed there was no significant difference in prevalence between the two sites, with a chi-square test yielding p = 0.1902. Nor was there significant variation across sentinel houses within either area, with Kruskal-Wallis tests returning p = 0.35 in Ahero and p = 0.45 in Miwani. Even between larvae collected in the two zones, prevalence was statistically indistinguishable, with p = 0.8990. In other words, despite a seven-fold difference in host population density, the microbe maintained remarkably consistent prevalence across both landscapes.

The team did observe significant temporal variation in prevalence across collection rounds within each site. In Ahero, prevalence peaked at 38.8 percent in one round and dropped to 0.6 percent in another, with these fluctuations positively associated with mosquito host abundance and seasonal changes in relative humidity. In Miwani, peaks reached 47.6 percent, linked to host abundance and the Normalized Difference Vegetation Index, a satellite-derived measure of vegetation greenness. But these were seasonal surges rather than systematic spatial differences. Both landscapes maintained sufficient host populations to support stable endosymbiont persistence, suggesting that while abundance drives transmission peaks, baseline prevalence is resilient to local ecological shifts.

Beyond prevalence, the researchers also measured infection intensity, essentially the density of Microsporidia MB within infected mosquitoes. Here again, the results were consistent. Infection densities did not vary significantly between the two locations or between sentinel houses within each location, indicating that once established, the symbiont maintains relatively stable within-host densities across geographic space. Densities did vary between mosquito species, with An. arabiensis carrying the highest loads and An. funestus the lowest, hinting at species-specific physiological compatibility. But the overall picture was one of a symbiont whose dynamics are largely decoupled from the agroecological context of its host.

The environmental drivers that did emerge were intriguing. Using Bayesian hierarchical models, the team found that a one standard deviation increase in NDVI around a sentinel house was linked to a 30 percent increase in infection odds, while a comparable increase in wind speed reduced infection odds by 24 percent. The researchers suggest that vegetation promotes conditions suitable for resting, foraging, swarming, and mating, thereby enhancing symbiont transmission, while stronger winds could interfere with these behaviors or disperse infected mosquitoes from nearby aquatic habitats. These findings add to a growing understanding of factors shaping Microsporidia MB dynamics, including diet, mating characteristics, breeding site chemistry, and climatic factors.

Plasmodium detection, by contrast, followed the ecological gradient precisely. The rice scheme, with its higher vector-producing capacity, also showed greater spatio-temporal detection of the malaria parasite, with 15 of 17 total infections recorded in Ahero. Several sentinel houses in Ahero showed recurrent Plasmodium detections across multiple rounds, suggesting persistent transmission foci likely tied to irrigation. Notably, only a single co-infection of Microsporidia MB and Plasmodium was observed across both areas. In An. arabiensis, the Plasmodium infection rate was lower in symbiont-infected females, at 0.49 percent, than in uninfected individuals, at 0.84 percent. While the low frequency of natural infections precludes definitive statistical correlation, this pattern is consistent with the antagonistic interference phenotypes reported in laboratory settings and suggests the symbiont’s blocking potential is maintained across varying field conditions.

The implications for malaria control are significant. The consistency of Microsporidia MB prevalence across contrasting agroecosystems, despite dramatic differences in host density, provides the first field evidence that symbiont dynamics can be decoupled from agricultural land use. This addresses a key concern for symbiont-based control strategies, namely whether deployment efficacy could be hindered by fine-scale ecological variation. The researchers caution that their findings are specific to this study’s spatial scale of roughly 8 kilometers, and that prevalence estimates for the less abundant species may be limited by small sample sizes. But as a proof of concept, the message is clear: a microbe that can stop malaria transmission inside its mosquito host appears robust enough to persist across the very landscapes where it would need to work. Future large-scale longitudinal studies with increased sampling intensity will be essential to formally quantify the strength of the symbiont’s antagonism against Plasmodium under field conditions, but this study offers a promising baseline for wider-scale assessments of one of the most biologically elegant malaria control ideas yet proposed.

Subject of Research: Different agroecosystems have similar Anopheles–Microsporidia MB infection dynamics in the Ahero region of Western Kenya: implications for symbiont control strategies

Article Title: Different agroecosystems have similar Anopheles–Microsporidia MB infection dynamics in the Ahero region of Western Kenya: implications for symbiont control strategies

Article References: Gichuhi, J., Bukhari, T., Onchuru, T. O., Mbare, O., Odoyo, E., & Herren, J. K. (2026). Different agroecosystems have similar Anopheles–Microsporidia MB infection dynamics in the Ahero region of Western Kenya: implications for symbiont control strategies. Frontiers in Malaria, 4, Article 1794884. https://doi.org/10.3389/fmala.2026.1794884

Image Credits: AI Generated

DOI: 10.3389/fmala.2026.1794884

Keywords: Microsporidia MB, malaria, Anopheles, symbiont control, Kenya, Plasmodium falciparum, vector ecology, agroecosystems, Different, similar, Microsporidia, infection

Between September 2020 and August 2021, researchers deployed six miniature CDC light traps each month across urban, peri-urban and rural ecotopes of Kousseri County, running the traps from dusk to dawn over 30 trapping nights per month. The effort yielded 4,214 sandfly specimens, of which 51.02 percent were females, the sex responsible for transmitting Leishmania parasites to humans and animals. Rural sites accounted for the largest share of captures at 43.43 percent, followed by peri-urban areas at 33.38 percent, while the urban environment produced just 22.69 percent of the total.

Seasonality proved striking. January, in the middle of the region’s prolonged eight-month dry season, recorded the highest abundance with 679 specimens, and March followed closely with 597. The lowest numbers appeared in September and October, at the tail end of the rainy season, when flooding of the semi-arid Sahelian landscape likely suppressed adult activity. Unlike mosquitoes, sandflies have a fully terrestrial life cycle that does not require standing water, but their larvae need sufficiently moist soil, and excessive flooding appears to push populations down rather than up.

Morphological identification of the 2,150 dissected females revealed eleven species: ten belonging to the genus Sergentomyia and a single Phlebotomus species, Phlebotomus duboscqi. That latter species is significant because it is the only proven vector of leishmaniasis in the region, responsible for cutaneous disease caused by Leishmania major and suspected of playing a role in visceral transmission. Yet Ph. duboscqi represented a mere 1.07 percent of the total catch, was absent in January and July, and peaked in September at an average of just 1.67 sandflies per trap per night.

The dominant Sergentomyia species each followed distinct monthly patterns. Sergentomyia antennata, the most prevalent species overall, showed a unimodal peak in January, averaging 16.67 sandflies per trap per night. Sergentomyia squamipleuris also peaked once, in February, at 7.38 per trap per night. Sergentomyia distincta followed a bimodal trend with peaks in January and May, while Sergentomyia schwetzi, the second most abundant species, displayed a trimodal pattern with major peaks in September, March and August. Four species, including Se. antennata, Se. distincta, Se. squamipleuris and Se. schwetzi, were present in every month of the year, underscoring the year-round transmission potential in the focus.

Ecological preferences differed sharply between species and habitats. Se. distincta was most abundant in urban settings, suggesting a preference for densely populated areas where human blood meals are readily available. Se. schwetzi dominated peri-urban ecotopes, where animal shelters sit close to human dwellings amid irregular waste collection and scattered vegetation. The remaining Sergentomyia species, including Se. antennata, Se. clydei, Se. adleri, Se. africana and Se. squamipleuris, declined from rural to urban areas, pointing to an adaptation to rural environments characterised by rice paddies, agricultural fields and livestock.

The rural advantage for sandflies appears to stem from concrete housing and land-use features. Dwellings in rural and peri-urban Kousseri are typically built from unplastered mud walls whose cracks and fissures provide ideal resting, breeding and mating sites for adult sandflies. Nearby rice paddies and animal compounds offer sugar sources for energy and blood meals for egg development, bringing flies, livestock and people into close contact. By contrast, the urban sites surveyed were predominantly residential with plastered walls and modern infrastructure, conditions that previous work suggests can substantially reduce sandfly populations.

Diversity analysis reinforced the complexity of the community. Shannon-Wiener indices exceeded 1 in all ecotopes and months, indicating high evenness, and Simpson diversity values ranged from 0.56 to 0.83 across the year. Species richness varied from six to nine species per month, with the lowest recorded in October. Non-metric multidimensional scaling based on Bray-Curtis dissimilarities revealed distinct seasonal clustering, with September, December and March grouping together, October and November forming a separate pattern, and the peak rainy-season months of April, May, June and August sharing similar species abundance profiles.

Notably, the dry-season peak in Kousseri contradicts earlier findings from the Mokolo cutaneous leishmaniasis focus in Cameroon, where sandfly numbers rose during the rainy season. The pattern instead aligns with observations from arid and semi-arid regions of Iran and parts of Kenya, where optimal microclimatic conditions during dry months favour sandfly activity. Kousseri’s temperatures, which swing from 11 degrees Celsius in December to 45 degrees Celsius in the shade by April and May, fall within the 25 to 28 degree range that sandflies favour for much of the year, helping explain their continuous presence.

The findings carry direct implications for public health. Because sandflies remain active throughout the year but surge in January and March, surveillance and interventions such as insecticide application and insecticide-treated bed nets should be prioritised in those months, particularly in rural settings where abundance is highest. Plastering the cracked mud walls of homes and animal shelters could further reduce breeding and resting sites. The researchers also stress that the true vector of visceral leishmaniasis in Kousseri remains unidentified, and that Sergentomyia species, traditionally associated with reptile parasites, have been implicated elsewhere in transmitting Leishmania infantum to dogs and potentially pathogenic species to humans. Determining blood-meal sources, feeding behaviour and natural Leishmania infection rates, alongside multi-year monitoring of climatic drivers, will be essential to building an evidence-based control strategy for a region where the disease remains neglected and untreated.

Subject of Research: Monthly occurrence and ecology of phlebotomine sandfly species in a visceral leishmaniasis endemic focus of northern Cameroon

Article Title: Occurrence and monthly dynamics of female Phlebotomine sandfly species from Kousseri Visceral Leishmaniasis endemic focus in northern Cameroon

Article References: Tebo-Nzesseu, T. R., Ngouateu Tateng, A., Bebe Ngouateu, O., Foyet, J. V., Ngnindji-Youdje, Y., Payne, V. K., & Dondji, B. (2025). Occurrence and monthly dynamics of female Phlebotomine sandfly species from Kousseri Visceral Leishmaniasis endemic focus in northern Cameroon. African Invertebrates, 66(2), 229-249. https://doi.org/10.3897/afrinvertebr.66.160860

Image Credits: AI Generated

DOI: 10.3897/AfrInvertebr.66.160860

Keywords: leishmaniasis, sandflies, Phlebotomus duboscqi, Sergentomyia, Cameroon, vector ecology, public health, neglected tropical diseases, Occurrence, monthly, dynamics, female

The scale of the field effort was considerable. Between August 2018 and September 2019, the research team deployed three complementary trap types—Biogents Sentinel traps, CDC Gravid traps, and CDC Light Traps—at 19 study locations across the Ouest Department. Over the thirteen-month sampling window, they captured a total of 22,504 mosquitoes. Two species dominated the catch: Culex quinquefasciatus, which accounted for 53.4 percent of all specimens, and Aedes aegypti, which made up 16.9 percent. These are not incidental species. Cx. quinquefasciatus is the principal vector of lymphatic filariasis in Haiti, while Ae. aegypti transmits the arboviruses responsible for dengue, Zika, chikungunya, and yellow fever. Their numerical dominance underscores how heavily the region’s disease burden is concentrated in a small number of highly adapted urban vectors.

Alongside the two dominant species, the collections included Anopheles albimanus, the country’s key malaria vector, and a broader cast of secondary species, including Psorophora columbiae. All mosquitoes were identified morphologically, and the team then quantified biodiversity using a standard ecological toolkit: species richness measures of alpha diversity, Shannon’s index, and Simpson’s index. Each of these metrics captures a slightly different aspect of community structure—raw species counts, the balance between richness and evenness, and the probability that two randomly drawn individuals belong to the same species, respectively. Applying all three allowed the researchers to distinguish sites that merely hosted many species from those that supported genuinely balanced, multi-species communities.

A crucial methodological finding emerged from this diversity assessment: the metrics varied significantly both by trap type and by month. No single trapping method painted a complete picture of the mosquito community. Biogents Sentinel traps, which target host-seeking container-breeding Aedes, CDC Gravid traps, which attract egg-laying females enriched for Culex, and CDC Light Traps, which sample nocturnal flying insects broadly, each bias collections toward particular behaviors and species. The implication for surveillance programs is direct—reliance on a single trap design risks systematically undercounting the very species that matter most for a given disease system, and the authors emphasize the need for diversified trapping methods in future monitoring efforts.

To move beyond description and identify the environmental forces structuring these communities, the team turned to boosted regression trees, a machine-learning technique increasingly favored in disease ecology for its ability to model nonlinear relationships and interactions among many predictors simultaneously. The models incorporated both static and temporally varying covariates, including temperature, precipitation, vegetation indices measured through the normalized difference vegetation index (NDVI), and human population density. By relating the diversity indices computed for each collection event to these environmental layers, the BRTs could rank the relative influence of each factor and reveal the shapes of their effects—something classical linear models often obscure.

The results were striking in their consistency. Human population density, temperature, and vegetation indices emerged as the key predictors of mosquito diversity across the study area. This triad tells an ecologically coherent story. Dense human settlement creates the artificial containers, storm drains, and water-holding debris that container-breeding Aedes require, while also supplying the blood meals that sustain high vector populations. Temperature governs mosquito development rates, viral replication within vectors, and seasonal activity windows. Vegetation, as indexed by NDVI, shapes the availability of shaded resting sites, organic-rich larval habitats, and the microclimates that favor some species over others. In a highly urbanized tropical setting, these three forces interact to determine which mosquito species coexist at any given site and in any given month.

Perhaps the most novel component of the study was its use of species co-occurrence networks to describe the relationships among mosquito species. The researchers constructed two types of networks—one based on a cross-product approach and one on a probabilistic framework—to test whether pairs of species occurred together more or less often than expected by chance. The networks revealed significant positive associations between Aedes species and Cx. quinquefasciatus, suggesting that the vectors of arboviruses and lymphatic filariasis frequently share the same habitats and may respond similarly to urban environmental conditions. For control programs, this is a double-edged finding: interventions targeting shared breeding habitats could suppress multiple disease vectors simultaneously, but conditions that favor one dominant species may also be quietly building populations of the others.

Not all relationships in the networks were positive. Psorophora columbiae exhibited negative associations with multiple other species, standing out as the community’s apparent contrarian. Negative co-occurrence patterns can arise from several mechanisms, including competition for larval resources, differing habitat preferences, or predation, although the study’s observational design means the underlying cause cannot be pinned down with certainty. What the pattern does establish is that inter-species dynamics are a real and measurable feature of Haiti’s mosquito communities, not a statistical artifact, and that single-species control strategies may produce ecological ripple effects that are currently poorly understood.

The public health stakes of this work are substantial. Haiti continues to confront endemic malaria transmitted by An. albimanus, recurring dengue outbreaks driven by Ae. aegypti, and lymphatic filariasis sustained by Cx. quinquefasciatus. Ae. albopictus, the Asian tiger mosquito, is also present as an arbovirus vector. By identifying the environmental conditions under which these vectors co-occur, the study provides a foundation for multi-species control measures—interventions designed not against one target insect but against the ecological communities that collectively transmit the country’s major vector-borne diseases. The finding that human population density is a central driver also highlights how urbanization itself functions as a disease ecology variable, concentrating vectors and humans in the same environmental envelope.

The authors are careful to frame their conclusions as a beginning rather than an endpoint. They call for further research on inter-species dynamics to build a more unified understanding of vector ecology in Haiti, and their study design—combining year-round field surveillance, multiple trap types, rigorous biodiversity metrics, machine-learning environmental modeling, and network analysis—offers a template that other resource-limited settings could adapt. The work was funded by the Armed Forces Health Surveillance Branch’s Global Emerging Infections Surveillance section and through a Battelle Memorial Institute contract supporting Navy force health protection efforts, reflecting the strategic importance placed on vector surveillance in the Caribbean region. As climate change alters temperature regimes and urbanization accelerates across the tropics, the environmental levers identified in this study—population density, heat, and vegetation—will only grow in importance for predicting where mosquito biodiversity, and the diseases it carries, will flourish next.

Subject of Research: Environmental and demographic drivers of mosquito biodiversity and species co-occurrence in urban Haiti

Article Title: Vegetation, temperature, and human population density influence mosquito biodiversity in Haiti

Article References: Pshea-Smith, I. A., Okech, B. A., Boncy, J., Existe, A., So, J., Hamilton, T., Blanton, J., Matulis, G. A., Metrailer, M. C., Cleary, N. G., Dunford, J. C., Koehler, J. W., Blackburn, J. K., & von Fricken, M. E. (2026). Vegetation, temperature, and human population density influence mosquito biodiversity in Haiti. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07724-3

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07724-3

Keywords: mosquito biodiversity, Haiti, Aedes aegypti, Culex quinquefasciatus, boosted regression trees, species co-occurrence networks, vector ecology, NDVI, urban ecology, dengue, malaria, lymphatic filariasis

Avian haemosporidians are a group of apicomplexan parasites belonging chiefly to three genera: Plasmodium, Haemoproteus, and Leucocytozoon. In birds, these organisms can behave much like the malaria parasites that afflict humans, invading blood cells and internal organs, sapping host condition, and in severe cases reducing survival and reproductive success. Their effects ripple outward into population dynamics, migration behavior, and even the structure of whole bird communities. For decades, ecologists have worked to map which insect vectors carry which parasite lineages, because transmission is the hinge on which the entire host-parasite system turns. Mosquitoes, Culicoides biting midges, louse flies, and black flies are the recognized vectors, each genus of parasite showing affinities for particular insect groups and particular bird hosts.

Leptoconops is a genus of haematophagous biting midges in the family Ceratopogonidae, closely related to the better-known Culicoides midges that are established vectors of avian Haemoproteus. Despite this kinship, Leptoconops midges have never been systematically implicated in avian malaria transmission, and no previous study had molecularly screened them for haemosporidian infections. That gap is precisely what motivated the research team, led by Javier Carbonero and Martina Ferraguti of the Estación Biológica de Doñana, a research institute of the Spanish National Research Council (CSIC) in Seville, together with colleagues affiliated with the Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública.

The scale of the fieldwork reflects the difficulty of the question. During 2024, the researchers collected a total of 5,417 female Leptoconops midges across sites in Andalusia, taking advantage of the fact that only female midges take blood meals and can therefore plausibly acquire and transmit blood parasites. Each specimen was morphologically identified to species, a labor-intensive step that matters because vector competence and host preferences can differ sharply even between close relatives. The midges were then grouped into 203 pools for molecular analysis, a pooling strategy that balances laboratory workload against the sensitivity needed to detect low-level infections in wild-caught insects.

The molecular heart of the study is a nested polymerase chain reaction (PCR) protocol targeting the cytochrome b gene, the standard DNA barcode region for avian haemosporidians. Nested PCR uses two successive rounds of amplification with two pairs of primers, dramatically increasing sensitivity and allowing researchers to detect the minute quantities of parasite DNA that may persist in an insect after a blood meal has been digested. Positive amplicons were then sequenced, and the resulting DNA barcodes were compared against reference databases to assign each parasite to a genus and, where possible, to a known lineage with a documented host range. This lineage-level resolution is what gives the study its ecological punch: many haemosporidian lineages have been catalogued from specific bird species, so finding a lineage inside a midge hints at which birds the midge may have bitten.

Eight of the 203 pools tested positive for haemosporidian DNA. The positive pools corresponded to two of the Leptoconops species examined, Leptoconops communis and Leptoconops nigrithorax, indicating that more than one member of the genus encounters these parasites in the wild. The identified parasites spanned all three target genera. Among the Haemoproteus detections were Haemoproteus noctuae, corresponding to the lineage CIRCUM01, and an unidentified Haemoproteus species of the lineage COLPAL01. The Plasmodium findings included Plasmodium matutinum, the well-characterized lineage LINN1, while Leucocytozoon was represented by the lineages COLIV04 and AEMO02. In addition to these known barcodes, the team uncovered two lineages that had never been recorded before, which they designated Plasmodium P_LEPTO01 and Haemoproteus H_LEPTO01, expanding the global catalogue of avian haemosporidian genetic diversity.

The known host associations of the detected lineages are where the story becomes genuinely suggestive. Haemoproteus noctuae, for example, is a parasite associated with owls and other birds, and lineages such as LINN1 and COLIV04 have been documented from particular avian hosts in previous surveys. By matching the lineages found in the midges to their known bird hosts, the researchers can infer, indirectly, which avian species Leptoconops midges may have fed upon. This approach, sometimes framed within the broader use of insect-derived DNA as a sampling tool, effectively turns each infected midge into a tiny record of both a bird-parasite interaction and a midge feeding choice. It is an indirect inference rather than a direct blood-meal identification, but it provides testable hypotheses about the feeding ecology of a genus whose biting habits remain poorly documented in many regions.

The authors are careful, and appropriately so, about what the results do and do not demonstrate. Detecting parasite DNA in an insect does not establish vector competence, the ability of a vector to support the parasite’s full developmental cycle and transmit it to a new host. Haemosporidian parasites undergo a complex development within a competent vector, including sexual reproduction, invasion of the insect’s gut wall, production of infective sporozoites, and migration to the salivary glands. Parasite DNA could, in principle, simply reflect the digestion of an infected blood meal without any subsequent parasite development. The researchers explicitly state that vector competence has not been demonstrated and that the potential role of Leptoconops in transmission is unknown and merits further investigation. Disentangling genuine biological transmission from mere mechanical carriage of DNA will require experimental infection studies, dissection of midge tissues, and detection of parasite developmental stages rather than DNA alone.

Even with those caveats, the study carries weight for several reasons. First, it establishes a previously unrecorded interaction between a widespread genus of biting midges and avian haemosporidian parasites, adding Leptoconops to the short list of insect groups in which these parasites have been molecularly detected. Second, the diversity of parasites found, spanning Plasmodium, Haemoproteus, and Leucocytozoon, suggests that the encounters are not a rare accident of a single parasite species but a broader pattern involving multiple parasite lineages and at least two midge species. Third, the discovery of two novel lineages underscores how much undocumented parasite diversity circulates in wild bird communities and their vectors, and how vector-focused sampling can surface it. Fourth, the work has practical implications: if Leptoconops midges prove to be competent vectors, current models of avian malaria transmission, which lean heavily on mosquitoes and Culicoides, would need revision, with consequences for understanding disease dynamics in bird populations, the risks faced by vulnerable species, and even the epidemiology of zoonotic or wildlife pathogens in shared landscapes.

The research was conducted by a team based at the Estación Biológica de Doñana in Seville, with funding from projects including ARBOPREVENT, supported by Fundación La Caixa, a national research project financed by Spain’s Ministry of Science and European regional funds, and the Severo Ochoa excellence program. The work formed part of a broader research effort on vector ecology in southern Spain, where wetland habitats concentrate both bird diversity and biting insects. As the authors conclude, the findings suggest real interactions between Leptoconops midges and infected avian hosts, and they call for further studies to determine whether these midges are incidental carriers or genuine players in the transmission of avian malaria. For now, a genus of tiny midges, long noted mainly for the irritating bites of its females, has earned a place on the watch list of avian disease ecology, and the search for its true role in the parasite’s life cycle is only beginning.

Subject of Research: Molecular detection of avian haemosporidian parasites in Leptoconops biting midges

Article Title: First molecular detection of avian haemosporidian parasites in Leptoconops (Diptera: Ceratopogonidae) biting midges

Article References: Carbonero, J., González, M. A., Magallanes, S., Paun-Tanase, D. I., Martínez-de la Puente, J., Figuerola, J., & Ferraguti, M. (2026). First molecular detection of avian haemosporidian parasites in Leptoconops (Diptera: Ceratopogonidae) biting midges. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07713-6

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07713-6

Keywords: avian malaria, haemosporidian parasites, Leptoconops, biting midges, Ceratopogonidae, Plasmodium, Haemoproteus, Leucocytozoon, vector ecology, cytochrome b, nested PCR, Andalusia

The scale of the underlying field effort is remarkable. Between 2013 and 2025, members of the Hokkaido University Tick Hunting Team, joined by collaborators across the country, systematically dragged cloth flags through vegetation at 1,018 sites spanning 38 of Japan’s 47 prefectures. This flagging method, the standard technique for sampling host-seeking ticks, involves pulling a white cloth square across low vegetation so that questing ticks latch onto it. The surveys yielded a total of 22,416 individual ticks, representing the sixteen species that formed the basis of the modeling work. Because tick distribution data have historically been restricted to localized studies, this dataset provides an unusually broad and consistent foundation for predicting where each species can persist across the entire Japanese archipelago.

To transform field observations into predictive maps, the team employed the maximum entropy method, widely known as Maxent, a machine-learning approach that estimates the probability of species presence from occurrence records and environmental variables. The models incorporated three categories of predictors: climatic variables such as temperature and precipitation, topographic features such as elevation, and landscape variables describing land cover and habitat type. The resulting predictions were generated at a resolution of one square kilometer, fine enough to distinguish habitat suitability between neighboring valleys or forest patches. Model performance was robust across the sixteen species, giving the researchers confidence that the maps capture genuine ecological patterns rather than statistical noise.

Among all the environmental variables tested, one emerged with unexpected prominence: snow depth. For six of the sixteen tick species, snow depth contributed the largest share of explanatory power in the models. This finding carries real ecological weight. Deep, persistent snow insulates the ground layer where ticks overwinter, moderating the extreme cold that would otherwise kill them, but it also shapes the length of the active season and the structure of the vegetation communities ticks depend on. In a country that stretches from subtropical Okinawa to the frigid northern island of Hokkaido, snow depth turns out to be a fundamental determinant of where ticks can establish populations, and by extension, where the pathogens they carry can circulate.

The predicted suitable habitats showed striking interspecific variation, following both latitudinal and elevational gradients. Some species are confined to the cool, snowy north, while others thrive in the warmer south; some occupy lowland forests, others climb into mountain terrain. This diversity of distribution patterns matters because each tick species is a competent vector for a different set of pathogens. A map that lumps all ticks together would obscure precisely the spatial structure that determines which diseases threaten which communities. The new species-by-species approach reveals that patchwork in detail for the first time.

The most consequential step of the analysis went beyond mapping habitats and asked whether the predicted distributions actually explain where human cases of tick-borne disease occur. The researchers converted their one-kilometer probability maps into prefecture-level statistics, calculating for each of Japan’s prefectures the proportion of grid cells predicted to be occupied by each tick species. They then used regression analyses to test whether these occupancy proportions could account for the reported numbers of five notifiable tick-borne diseases: severe fever with thrombocytopenia syndrome, tick-borne encephalitis, Japanese spotted fever, Lyme disease, and relapsing fever. The answer was a clear yes, with significant correlations between the predicted area occupied by suspected vector species and the reported case counts for each disease.

The species-disease alignments were biologically coherent in ways that strengthen confidence in the results. For diseases with a predominantly northern distribution, such as Lyme disease, the predicted distributions of Ixodes pavlovskyi and Ixodes persulcatus aligned closely with reported case occurrence, and both species are known vectors of the Borrelia bacteria that cause the illness. At the opposite end of the map, Haemaphysalis flava emerged as the primary contributor to model performance for Japanese spotted fever and the secondary contributor for severe fever with thrombocytopenia syndrome, two diseases concentrated in southern and western Japan. Again, the correlated species are recognized vectors of the corresponding pathogens. In other words, the models did not merely find statistical associations; they recovered the known vector ecology of each disease from environmental data alone.

This external validation against disease surveillance data is what elevates the study from a biogeographic exercise to a practical public health tool. Species distribution models are often evaluated solely on their ability to reproduce the occurrence records used to build them, which risks circularity. By demonstrating that independently collected human disease reports track the predicted tick distributions, the researchers provided evidence that the maps capture something real about transmission risk on the ground. For public health authorities, this means the maps can serve as an early-warning layer, highlighting prefectures where environmental conditions favor vector species even before cases accumulate.

The implications extend beyond Japan’s borders. Climate change is expected to shift temperature and snowfall patterns across temperate Asia, and because snow depth proved to be such a powerful predictor, changes in snow cover could redraw the boundaries of tick habitat in the coming decades. Species currently confined to Hokkaido’s snowy forests might expand southward or upslope, carrying tick-borne encephalitis and other northern diseases into new territories. Conversely, warming could compress the suitable habitat of cold-adapted species. The modeling framework established in this study, with its one-kilometer resolution and multi-species coverage, provides a baseline against which such shifts can be measured and anticipated.

The study also demonstrates the value of sustained, collaborative fieldwork. Twelve years of surveys, involving dozens of students and researchers in the Hokkaido University Tick Hunting Team and partner laboratories from Kitasato University, the University of Tokyo, the University of Osaka, and beyond, produced the occurrence data that no amount of modeling ingenuity could substitute for. The authors note that the resulting maps, offering a nationwide overview of tick distributions, serve as basic information for anticipating the occurrence of tick-borne diseases in the region. For clinicians, the maps offer context for differential diagnosis when patients present with fever after outdoor exposure; for epidemiologists, they provide a spatial framework for surveillance prioritization; and for the public, they offer a clearer picture of the invisible landscape of risk that accompanies a walk through Japan’s forests and grasslands.

Subject of Research: Species distribution modeling of tick vectors and tick-borne disease occurrence in Japan

Article Title: Predicting the distribution of 16 tick species in Japan and its association with the occurrence of tick-borne diseases

Article References: Ito, M., Ohari, Y., Ohsugi, Y., Taya, Y., Hayashi, N., Ogata, S., Kusakisako, K., Qiu, Y., Nonaka, N., Mizuma, K., Torii, S., Kajihara, M., Hokkaido University Tick Hunting Team (HUT-HuT), Mimura, Y., Regilme, M. A. F., Thu, M. J., Kovba, A., Kwak, M., Teo, E., … Nakao, R. (2026). Predicting the distribution of 16 tick species in Japan and its association with the occurrence of tick-borne diseases. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07717-2

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07717-2

Keywords: ticks, species distribution modeling, Maxent, Japan, Lyme disease, severe fever with thrombocytopenia syndrome, Japanese spotted fever, tick-borne encephalitis, snow depth, vector ecology, public health, Ixodes