Spatio-temporal patterns of stomoxyine flies (Diptera: Muscidae) in a forested area of Thailand.

Understanding the distribution patterns of vector populations is crucial for comprehending the dynamics of vector-borne diseases. However, data on vector composition and abundance in areas of forest and wildlife-human interface in Thailand remain limited. This research aimed to investigate the spatio-temporal distribution and species diversity of stomoxyine flies (Diptera: Muscidae) in Salakpra Wildlife Sanctuary, Thailand's first wildlife sanctuary. A longitudinal entomological survey was conducted monthly from May 2022 to April 2023 in four habitats: core forest, grassland forest, a wildlife breeding center, and a local cattle farm. A total of 11,256 stomoxyine flies from four genera were captured. Based on morphological keys, nine species of stomoxyine flies were identified: Stomoxys pullus (29.63%), Stomoxys calcitrans (19.65%), Stomoxys indicus (16.09%), Haematostoma austeni (14.23%), Haematobia irritans exigua (8.22%), Haematobosca sanguinolenta (7.96%), Stomoxys uruma (1.98%), Stomoxys sitiens (1.75%), and Stomoxys bengalensis (0.49%). Heterogeneous variations in abundance across months and habitats were observed, in which abundance increased in the rainy season (June-October), exhibiting bimodal peaks at seasonal transitions. Human-disturbed areas, such as the cattle farm, exhibited the highest density and species diversity of stomoxyine flies. In contrast, areas with minimal human disturbance, like core forest, had low diversity and density but supported unique species, like the abundant Haematostoma austeni, which had minor populations in other types of habitats. The results of this study can be integrated into epidemiological models and lay the groundwork for more comprehensive research on vector-borne diseases at the wildlife-livestock interface to mitigate transmission risks and preserve biodiversity.

Title: Schémas spatio-temporels des stomoxes (Diptera : Muscidae) dans une zone forestière de Thaïlande. Abstract: Comprendre les schémas de distribution des populations de vecteurs est essentiel pour comprendre la dynamique des maladies à transmission vectorielle. Cependant, les données sur la composition et l'abondance des vecteurs dans les zones de forêt et d'interface faune-humain en Thaïlande restent limitées. Cette recherche visait à étudier la distribution spatio-temporelle et la diversité des espèces de stomoxes (Diptera : Muscidae) dans le sanctuaire faunique de Salakpra, le premier sanctuaire faunique de Thaïlande. Une enquête entomologique longitudinale a été menée mensuellement de mai 2022 à avril 2023 dans quatre habitats : forêt centrale, forêt de prairie, un centre d'élevage d'animaux sauvages et une ferme d'élevage locale. Au total, 11 256 stomoxes de quatre genres ont été capturés. Sur la base des clés morphologiques, neuf espèces de stomoxes ont été identifiées : Stomoxys pullus (29,63 %), Stomoxys calcitrans (19,65 %), Stomoxys indicus (16,09 %), Haematostoma austeni (14,23 %), Haematobia irritans exigua (8,22 %), Haematobosca sanguinolenta (7,96 %), Stomoxys uruma (1,98 %), Stomoxys sitiens (1,75 %) et Stomoxys bengalensis (0,49 %). Des variations hétérogènes de l'abondance selon les mois et les habitats ont été observées, l'abondance augmentant pendant la saison des pluies (juin à octobre), présentant des pics bimodaux aux transitions saisonnières. Les zones perturbées par l'homme, comme la ferme d'élevage, présentaient la plus forte densité et la plus grande diversité d'espèces de stomoxes. En revanche, les zones peu perturbées par l'homme, comme la forêt centrale, présentaient une faible diversité et une faible densité, mais abritaient des espèces uniques, comme l'abondant Haematostoma austeni, dont les populations étaient mineures dans d'autres types d'habitats. Les résultats de cette étude peuvent être intégrés dans des modèles épidémiologiques et posent les bases d'une recherche plus complète sur les maladies à transmission vectorielle à l'interface faune-bétail afin d'atténuer les risques de transmission et de préserver la biodiversité.

Why aphid virus retention needs more attention: Modelling aphid behaviour and virus manipulation in non-persistent plant virus transmission.

Plant viruses threaten food security and are often transmitted by insect vectors. Non-persistently transmitted (NPT) plant viruses are transmitted almost exclusively by aphids. Because virions attach to the aphid's stylet (mouthparts) and are acquired and inoculated via brief epidermal probes, the aphid-virus interaction is highly transient, with a very short aphid virus retention time. Many NPT viruses manipulate their host plant's phenotype to change aphid behaviour to optimise virus transmission. Epidemiological models of this have overlooked a key feature of aphid NPT virus retention: probing or feeding on a plant causes aphids to lose the virus. Furthermore, experimental studies suggest aphids could possibly inoculate multiple healthy plants within one infective period if they do not feed. Consequences of this for virus manipulation of host plant phenotype have not been explored. Our new compartmental epidemiological model includes both behaviour-based aphid dispersal and infectivity loss rates, and the ability of infective aphids to probe multiple plants before virus loss. We use our model to explore how NPT virus-induced host phenotypes affect epidemic outcomes, comparing these results to representative previous models. We find that previous models behave fundamentally differently and underestimate the benefit of an 'attract-and-deter' phenotype, where the virus induces increased aphid attraction to infected plants but deters them from prolonged feeding. Our results also highlight the importance of characterising NPT virus retention upon the aphid during probing. Allowing for multiple infective probes increases disease incidence and the effectiveness of virus manipulation, with implications for epidemic prediction and control.

[Distribution and seasonal fluctuation of visceral leishmaniasis vectors sandflies in Henan Province in 2023].

OBJECTIVE: To investigate the geographical distribution and seasonal fluctuations of visceral leishmaniasis vectors sandflies in Henan Province in 2023, so as to provide insights into the prevention and control of visceral leishmaniasis vectors. METHODS: A total of 23 counties (districts) were sampled from 18 cities of Henan Province from May to September, 2023 as sandfly surveillance sites, and sandflies were captured using human capture and light trapping methods. Following morphological identification, the changes in the sandfly density were calculated at different months and in different breeding habitats. RESULTS: A total of 406 light traps were set at sandfly surveillance sites in Henan Province from May to September, 2023, and a total of 3 137 female sandlies were captured, with an average density of 7.73 sandlies/(light·night). A total of 1 494 Phlebotomus chinensis sandflies were captured, including 1 222 female sandflies, with an average density of 3.01 sandflies/(light·night), and the highest density of P. chinensis was found in Gongyi City [17.00 sandflies/(light·night)]. A total of 5 544 sandflies were captured using the human capture method, including 230 P. chinensis, and the density of P. chinensis appeared a unimodal distribution, with a peak in early July [5.81 sandflies/(light·night)]. Among different breeding habitats, the highest P. chinensis density was detected in pigpens [4.50 sandflies/(light·night)]. CONCLUSIONS: P. chinensis was predominantly distributed in hilly areas of northern and central-western Henan Province in 2023, and the sandfly density appeared a unimodal distribution. Intensified monitoring of visceral leishmaniasis vectors is recommended.

[Distribution and seasonal fluctuation of visceral leishmaniasis vectors sandflie in Lüliang City of Shanxi Province in 2023].

OBJECTIVE: To investigate the distribution and seasonal fluctuations of visceral leishmaniasis vectors sandflies in Lüliang City, Shanxi Province, so as to provide insights into assessment of the visceral leishmaniasis transmission risk and formulation of visceral leishmaniasis control measures. METHODS: A total of 12 natural villages were sampled from Shilou County, Lishi District, Lanxian County, Linxian County and Wenshui County in Lüliang City, Shanxi Province from June to September, 2023, and sandflies were captured using light traps from 7 breeding habitats, including farmers' houses, sheep pens, cattle pens, chicken coops, pig pens, mule and horse pens, and loess-cave dwellings. Following morphological identification of the sandfly species, the distribution of sandflies and the seasonal fluctuations of the sandfly density were analyzed. In addition, the Leishmania was detected in sandflies using a real-time fluorescence quantitative PCR assay. RESULTS: A total of 2 831 sandflies were captured with 156 light traps in Lüliang City from June to September, 2023, including 2 638 female sandflies (93.18%) and 193 male sandflies (6.82%), and the average density was 16.91 sandflies/(light-night). The seasonal fluctuations of the sandfly density all appeared a unimodal distribution in all survey sites, and the sandfly density peaked in July and then declined rapidly. Among all types of breeding habitats, the greatest sandfly density was found in sheep pens [39.04 sandflies/(light-night)]. In addition, 4.08% (2/49) of the sandfly samples were tested positive for Leishmania nucleic acid as revealed by the real-time fluorescence quantitative PCR assay. CONCLUSIONS: Sandflies were widely distributed in Lüliang City, Shanxi Province in 2023, and the peak of the sandfly density was observed in July, which had a visceral leishmaniasis transmission risk. Intensified surveillance of visceral leishmaniasis and sandfly vectors is required and targeted vector control is recommended.

Sand flies and Toscana virus: Intra-vector infection dynamics and impact on Phlebotomus perniciosus life-history traits.

Toscana virus (TOSV) is a leading cause of summer viral meningitis in Southern Europe (Central Italy, south of France, Spain and Portugal) and can cause severe neurological cases. Within the Mediterranean basin, it is transmitted by hematophagous sand flies belonging to the Phlebotomus genus. Despite the identification of the primary TOSV vectors, the viral developmental cycle in vector species remains largely unknown. Limited research has been conducted on transmission dynamics and the vector competence and vectorial capacity of the principal TOSV vector, Phlebotomus perniciosus. In this context, we investigated the intra-vector TOSV infection dynamics in Ph. perniciosus, as well as its impact on the vector life history traits. Female sand flies were experimentally infected with TOSV through an artificial blood meal. Systemic dissemination of the virus was observed approximately three days post-infection, potentially resulting in a short extrinsic incubation period. Moreover, the study revealed a longer hatching time for eggs laid by infected females. This research brought additional experimental insights regarding the vector competence of Ph. perniciosus but also provided the first insight into TOSV developmental cycle and its impact on the vector. These findings prompt further exploration of TOSV transmission dynamics, raise new hypotheses on the virus transmission and highlight the importance of follow-up studies.

A study on the diversity of phlebotomine sand flies (Diptera, Psychodidae) in karstic limestone areas in Vientiane Province, Laos, with a description of two new species of Sergentomyia França and & Parrot.

BACKGROUND: Southeast Asia is well known as a hotspot of biodiversity. However, very little is known about cave-dwelling hematophagous insects that are medically important. Taxonomic knowledge and ecology of phlebotomine sand flies are very poorly studied in Laos, as well as in other countries in the region. Herein, we report species diversity data and some notes on the ecology of the detected species from these karstic limestone areas of Laos. METHODS: Phlebotomine sand flies were collected using Centers for Disease Control and Prevention (CDC) light traps from limestone cave locations in three districts of Vientiane Province, Laos. Both morphological and molecular techniques were used for sand fly identification. Species diversity and abundance were analyzed according to sites, locations, collection seasons, and trapping positions. RESULTS: A total of 6564 sand flies, of which 5038 were females and 1526 were males, were morphologically identified into 20 species belonging to five genera (Chinius, Idiophlebotomus, Phlebotomus, Sergentomyia, and Grassomyia). The most abundant species were Chinius eunicegalatiae, Phlebotomus stantoni, Sergentomyia hivernus, Se. siamensis, and Idiophlebotomus longiforceps. Cytochrome b analysis results supported the morphological identification and revealed that Se. siamensis was separated from other members of the Se. barraudi group. Two new species, Se. dvoraki n. sp. and Se. marolii n. sp., were described. Sand fly density was generally high except in a cave in Vangvieng, with species richness ranging from 14 to 18 across different caves. Outside caves had higher species richness (R = 20) and diversity (H = 2.50) than cave entrances (R = 18, H = 2.41) and interiors (R = 16, H = 2.13). Seasonal variations showed high sand fly density in Feung and Hinheup during both dry and rainy seasons, while Vangvieng had a notable decrease in density during the dry season (D = 6.29). CONCLUSIONS: This study revealed that the diversity of phlebotomine sand fly fauna in Laos, particularly in karstic limestone areas, is greater than previously known. However, the taxonomic status of many species in Laos, as well as Southeast Asia, still needs more in-depth study using both morphological characters and molecular methods. Many species could be found from inside, at the entrance, and outside of caves, indicating a wide range of host-seeking behavior or possible natural breeding in the karstic cave areas.

You are what you eat: a systematic review exploring the interaction between Brazilian sand flies and their vertebrate food sources.

Sand flies play a crucial role as vectors of bacteria, viruses, and protists, with Leishmania being the most notable among them, transmitted to vertebrate hosts during blood feeding. Understanding the feeding behaviours of sand flies is imperative for gaining insights into their eco-epidemiological roles in the transmission of these infectious agents. This systematic review aimed to answer the question 'What are the blood-feeding sources identified in Brazilian sand flies?' to provide an analysis of their blood-feeding habits. The diverse range of at least 16 vertebrate orders identified as blood sources for 54 sand fly species across different geographic regions was summarised, and the factors potentially associated with the risk of bias in the included studies were analysed. The findings broaden the discussion concerning methods used to identify blood meal sources and shed light on the implications of sand fly feeding behaviours for the transmission dynamics of Leishmania.

Irrigation, migration and infestation: a case study of Chagas disease vectors and bed bugs in El Pedregal, Peru.

BACKGROUND: The city of El Pedregal grew out of a desert, following an agricultural irrigation project in southern Peru. OBJECTIVES: To describe infestation patterns by triatomines and bed bugs and their relationship to migration and urbanization. METHODS: We conducted door-to-door entomological surveys for triatomines and bed bugs. We assessed spatial clustering of infestations and compared the year of construction of infested to un-infested households. To gain a better understanding of the context surrounding triatomine infestations, we conducted in-depth interviews with residents to explore their migration histories, including previous experiences with infestation. FINDINGS: We inspected 5,164 households for Triatoma infestans (known locally as the Chirimacha); 21 (0.41%) were infested. These were extremely spatially clustered (Ripley's K p-value < 0.001 at various spatial scales). Infested houses were older than controls (Wilcoxon rank-sum: W = 33; p = 0.02). We conducted bed bug specific inspections in 34 households; 23 of these were infested. These were spatially dispersed across El Pedregal, and no difference was observed in construction age between bed bug infested houses and control houses (W = 6.5, p = 0.07). MAIN CONCLUSIONS: The establishment of agribusiness companies in a desert area demanded a permanent work force, leading to the emergence of a new city. Migrant farmers, seeking work opportunities or escaping from adverse climatic events, arrived with few resources, and constructed their houses with precarious materials. T. infestans, a Chagas disease vector, was introduced to the city and colonized houses, but its dispersal was constrained by presence of vacant houses. We discuss how changes in the socioeconomic and agricultural landscape can increase vulnerability to vector-borne illnesses.

Modelling the Influence of Climate and Vector Control Interventions on Arbovirus Transmission.

Most mathematical models that assess the vectorial capacity of disease-transmitting insects typically focus on the influence of climatic factors to predict variations across different times and locations, or examine the impact of vector control interventions to forecast their potential effectiveness. We combine features of existing models to develop a novel model for vectorial capacity that considers both climate and vector control. This model considers how vector control tools affect vectors at each stage of their feeding cycle, and incorporates host availability and preference. Applying this model to arboviruses of veterinary importance in Europe, we show that African horse sickness virus (AHSV) has a higher peak predicted vectorial capacity than bluetongue virus (BTV), Schmallenberg virus (SBV), and epizootic haemorrhagic disease virus (EHDV). However, AHSV has a shorter average infectious period due to high mortality; therefore, the overall basic reproduction number of AHSV is similar to BTV. A comparable relationship exists between SBV and EHDV, with both viruses showing similar basic reproduction numbers. Focusing on AHSV transmission in the UK, insecticide-treated stable netting is shown to significantly reduce vectorial capacity of Culicoides, even at low coverage levels. However, untreated stable netting is likely to have limited impact. Overall, this model can be used to consider both climate and vector control interventions either currently utilised or for potential use in an outbreak, and could help guide policy makers seeking to mitigate the impact of climate change on disease control.

Relative contribution of biotic and abiotic factors to population fluctuations of Auchenorrhyncha community that could play a role in the Cape Saint Paul Wilt Disease (CSPWD) (lethal yellowing) pathosystem in Ghana.

As a major setback to the global coconut industry, lethal yellowing disease (LYD), caused by phytoplasmas, continues to threaten coconut palms in the Americas, the Caribbean, Africa, and Oceania. Despite its economic impacts, limited information exists on LYD vectors, which impedes the prevention and management of the disease. Using double-sided yellow sticky traps, we investigate the factors that influence the seasonal abundance and population dynamics of three sap-sucking insects of LYD, i.e., Diostrombus (Hemiptera: Derbidae) sp. and Patara sp. (Hemiptera: Derbidae), and Nedoptepa curta Dmitriev (Hemiptera: Cicadellidae), on five coconut genotypes (Sri Lanka Green Dwarf (SGD), Vanuatu Tall (VTT), SGD × VTT, Malayan Yellow Dwarf (MYD) × VTT, and West African Tall (WAT)) in the Western Region, and one (SGD) in the Central Region of Ghana from April 2019 to May 2021. The results showed that N. curta and Patara sp. were the most abundant species in the Western and Central Regions, respectively. There was a significant difference between the coconut cultivars and sap-sucking insects. The peak population development of the sap-sucking insects was recorded during the dry season on all the coconut genotypes at all sampling locations. A significant positive correlation was detected between temperature and the population of N. curta and Patara sp. In the Agona Nkwanta, VTT had the highest population of N. curta, whereas WAT had the highest population of Patara sp. and Diostrombus sp. These findings provide useful information for assessing the role of factors that could affect the Cape Saint Paul Wilt disease pathosystem.

Unveiling the overlooked: Current and future distribution dynamics of kissing bugs and palm species linked to oral Chagas disease transmission.

Chagas disease, a neglected global health concern primarily transmitted through the bite and feces of kissing bugs, has garnered increasing attention due to recent outbreaks in northern Brazil, highlighting the role of oral transmission facilitated by the kissing bugs species Rhodnius robustus and Rhodnius pictipes. These vectors are associated with palm trees with large crowns, such as the maripa palm (Attalea maripa) and moriche palm (Mauritia flexuosa). In this study, we employ maximum entropy (MaxEnt) ecological niche models to analyze the spatial distribution of these vectors and palm species, predicting current and future climate suitability. Our models indicate broader potential habitats than documented occurrences, with high suitability in northern South America, southern Central America, central Africa, and southeast Asia. Projections suggest increased climate suitability by 2040, followed by a reduction by 2080. This study identifies present and future areas suitable for kissing bugs and palm tree species due to climate change, aiding in the design of prevention and management strategies.

Updated checklist of the Culicoides Latreille biting midges (Diptera: Ceratopogonidae) of Galicia (NW Spain): Diversity, distribution and medical-veterinary relevance.

INTRODUCTION: Culicoides Latreille biting midges are vectors of high concern as they can transmit serious veterinary diseases such as bluetongue virus or epizootic haemorrhagic disease virus, among others. Little is known about these vectors in Galicia, so a comprehensive literature review and an intensive monitoring were carried out in the region. MATERIAL AND METHODS: The Autonomous Community of Galicia was sampled through three different vector surveillance projects between 2004 and 2023. A total of 239 sampling points were deployed alongside the Galician territory. In addition, a literature review of Culicoides in Galicia related content was made by consulting several digital repositories. RESULTS: A total of 33 species of Culicoides belonging to 8 subgenera were identified. Among them, 15 are considered or suspected to be potential vectors of several pathogens of medical and/or veterinary interest. In addition, 20 of them are reported for the first time in the region. Updated distribution maps of the Culicoides biting midges of Galicia were provided, including several notes regarding their ecology and relevance for both public health and animal welfare. CONCLUSIONS: The present work is one of the most complete works made at regional level in Spain to date. As Galicia's economy relies heavily on livestock farming, this work will provide a solid baseline in order to develop new research lines in the future regarding prevention to vector-borne diseases.

The complexities of blood-feeding patterns in mosquitoes and sandflies and the burden of disease: A minireview.

Mosquitoes and sandflies exhibit a wide range of blood feeding patterns, targeting a wide range of vertebrate species, including birds, mammals, reptiles, and amphibians, for proteins vital for egg development. This broad host range increases the opportunity for them to acquire pathogens of numerous debilitating-and-fatal diseases from various animal reservoirs, playing a significant role in disease crossover between animals and humans, also known as zoonotic transmission. This review focuses on the intricate blood-feeding habits of these dipteran vectors, their sensory systems and the complex dance between host and pathogen during disease transmission. We delve into the influence of blood sources on pathogen spread by examining the insect immune response and its intricate interplay with pathogens. The remarkable sense of smell guiding them towards food sources and hosts is explored, highlighting the interplay of multiple sensory cues in their navigation. Finally, we examine the challenges in mosquito control strategies and explore innovations in this field, emphasizing the need for sustainable solutions to combat this global health threat. By understanding the biology and behaviour of these insects, we can develop more effective strategies to protect ourselves and mitigate the burden of vector-borne diseases.

Range size positively correlates with temperature and precipitation niche breadths but not with dietary niche breadth in triatomine insects, vectors of Chagas disease.

Ecological theory predicts that species that can utilise a greater diversity of resources and, therefore, have wider niche breadths should also occupy larger geographic areas (the 'niche breadth-range size hypothesis'). Here, we tested this hypothesis for a blood-sucking group of insects of medical significance: the Triatominae (aka 'kissing bugs') (Hemiptera: Reduviidae). Given that niches can be viewed from different perspectives, we tested this hypothesis based on both dietary and climatic niches. We assembled the most complete dataset of triatomine feeding patterns to date by reviewing 143 studies from the literature up to 2021 and tested whether the niche breadth-range size hypothesis held for this group for both dietary and climatic components of the niche. Temperature and precipitation niche breadths were estimated from macro-environmental variables, while diet breadth was calculated based on literature data that used PCR and/or ELISA to identify different types of hosts as blood sources per triatomine species. Our results showed that temperature and precipitation niche breadths, but not dietary breadth, were positively correlated with range sizes, independent of evolutionary history among species. These findings support the predictions from the range size-niche breadth hypothesis concerning climate but not diet, in Triatominae. It also shows that support for the niche breadth-range size hypothesis is dependent upon the niche axis under consideration, which can explain the mixed support for this hypothesis in the ecological literature.

Reproductive consequences of the interaction Trypanosoma cruzi - Triatoma infestans and its trade-off with survival.

Relative little is known about fitness effects and life history trade-off of Trypanosoma cruzi in Triatoma infestans, the main vector of Chagas disease in Argentina. Previous studies revealed some costs related to development, excretion, and toxicology or their possible trade-offs, but none address effects on reproduction. To study the effect of T. cruzi infection on reproductive efficiency and survival of T. infestans we set up four treatments: both genders uninfected, both genders infected, female infected - males uninfected and female uninfected - males infected. The infection was induced during the third, fourth, and fifth nymphal instars. Reproductive efficiency and longevity variables were recorded. Our results showed that the infection by T. cruzi increased reproductive efficiency and reduced survival of T. infestans. Pairs where one or both individuals were infected presented a greater percentage copulation, of egg-laying females, the onset of copulation and oviposition occurred earlier, and age-specific fecundity was notably higher. Regarding fertility, infected females displayed higher rates irrespective of the infective status of the male counterpart. A reduction in longevity was observed in infected males and females. These findings highlighted that the infection significantly alters the trade-off reproductive efficiency-survival of T. infestans, with the impact differing according to the infection status of each gender, suggesting a complex interplay rather than a simple additive effect. This response corresponds to the reproductive compensation hypothesis.

A baited trap for kissing bugs (Hemiptera: Reduviidae: Triatominae).

Chagas disease is a key vector-borne disease. This illness is caused by Trypanosoma cruzi Chagas, which is transmitted by triatomine bugs. Largely, the control of this disease relies on reducing such contact. We optimized the performance of a box trap in laboratory conditions to capture four triatomine species: Triatoma pallidipennis (Stål), Triatoma infestans Klug, Triatoma phyllosoma (Burmeister), and Rhodnius prolixus Stål. We varied four components for a box trap: material, color, height, and bait attractants. All species were captured more in corrugated cardboard traps than in other trap material. Moreover, T. infestans and R. prolixus were also captured in plywood traps. T. pallidipennis preferred traps of 15 × 15 × 4 cm and 20 × 20 × 4 cm, while T. phyllosoma and T. infestans were more captured in traps of 10 × 10 × 4 cm, and 15 × 15 × 4 cm. Rhodnius prolixus was more captured to 10 × 10 × 4 cm traps. T. pallidipennis was trapped with traps of any color tested, T. phyllosoma and T. infestans were captured more in red and yellow traps, and R. prolixus was mostly captured in blue, violet, and yellow traps. Triatoma pallidipennis was captured at any height above the ground, while T. phyllosoma, T. infestans, and R. prolixus were mostly captured 50, 100, and 150 cm above the ground. Regarding the lure, T. pallidipennis was trapped with four aldehydes + lactic acid + ammonia; T. infestans and R. prolixus were trapped with a blend of four aldehydes + lactic acid, a blend of the four aldehydes + ammonia, and a blend of four aldehydes + lactic acid + ammonia. Triatoma phyllosoma was trapped with any lure tested. These results showed that the trap boxes offer an alternative method for controlling Chagas disease.

Slow recovery rates and spatial aggregation of Triatoma infestans populations in an area with high pyrethroid resistance in the Argentine Chaco.

BACKGROUND: The emergence of pyrethroid resistance has threatened the elimination of Triatoma infestans from the Gran Chaco ecoregion. We investigated the status and spatial distribution of house infestation with T. infestans and its main determinants in Castelli, a municipality of the Argentine Chaco with record levels of triatomine pyrethroid resistance, persistent infestation over 2005-2014, and limited or no control actions over 2015-2020. METHODS: We conducted a 2-year longitudinal survey to assess triatomine infestation by timed manual searches in a well-defined rural section of Castelli including 14 villages and 234 inhabited houses in 2018 (baseline) and 2020, collected housing and sociodemographic data by on-site inspection and a tailored questionnaire, and synthetized these data into three indices generated by multiple correspondence analysis. RESULTS: The overall prevalence of house infestation in 2018 (33.8%) and 2020 (31.6%) virtually matched the historical estimates for the period 2005-2014 (33.7%) under recurrent pyrethroid sprays. While mean peridomestic infestation remained the same (26.4-26.7%) between 2018 and 2020, domestic infestation slightly decreased from 12.2 to 8.3%. Key triatomine habitats were storerooms, domiciles, kitchens, and structures occupied by chickens. Local spatial analysis showed significant aggregation of infestation and bug abundance in five villages, four of which had very high pyrethroid resistance approximately over 2010-2013, suggesting persistent infestations over space-time. House bug abundance within the hotspots consistently exceeded the estimates recorded in other villages. Multiple regression analysis revealed that the presence and relative abundance of T. infestans in domiciles were strongly and negatively associated with indices for household preventive practices (pesticide use) and housing quality. Questionnaire-derived information showed extensive use of pyrethroids associated with livestock raising and concomitant spillover treatment of dogs and (peri) domestic premises. CONCLUSIONS: Triatoma infestans populations in an area with high pyrethroid resistance showed slow recovery and propagation rates despite limited or marginal control actions over a 5-year period. Consistent with these patterns, independent experiments confirmed the lower fitness of pyrethroid-resistant triatomines in Castelli compared with susceptible conspecifics. Targeting hotspots and pyrethroid-resistant foci with appropriate house modification measures and judicious application of alternative insecticides with adequate toxicity profiles are needed to suppress resistant triatomine populations and prevent their eventual regional spread.

Life history data of four populations of Triatoma mexicana (Hemiptera: Reduviidae) from Central Mexico.

Triatomine bugs are vectors for the Trypanosoma cruzi Chagas parasites, the etiological agent for Chagas disease. This study evaluated 6 epidemiologically significant behaviors (development time, number of blood meals required for molting to the next instar, mortality rate, aggressiveness, feeding duration, and defecation delay) across 4 populations of Triatoma mexicana Herrich-Schaeffer (Heteroptera: Reduviidae), a major T. cruzi vector in Central Mexico. We collected triatomines from areas characterized by high (HP), medium (MP), medium-high (MHP), and low (LP) prevalence of human T. cruzi infection. The MHP population had the shortest development time, <290 days. Both the HP and MP populations required the most blood meals to molt to the next instar, with a median of 13. Mortality rates varied across all populations, ranging from 44% to 52%. All of the tested populations showed aggressive behavior during feeding. All populations shared similar feeding durations, with most exceeding 13 min and increasing with each instar. Quick defecation, during feeding, immediately after or less than 1 min after feeding, was observed in most nymphs (78%-90%) from the MP and MHP populations and adults (74%-92%) from HP, MP, and MHP populations. Though most parameters suggest a low potential for T. mexicana to transmit T. cruzi, unique feeding and defecation behaviors in 3 populations (excluding the LP group) could elevate their epidemiological importance. These population-specific differences may contribute to the varying prevalence rates of T. cruzi infection in areas where T. mexicana is found.

Mechanisms controlling haemolymph circulation under resting conditions in the Chagas disease vector Rhodnius prolixus.

Chagas disease vectors can ingest several times their own volume in blood with each meal. This ad libitum feeding causes an intense process of diuresis, inducing the insect to eliminate a large quantity of urine and faeces. To ensure diuresis, the speed of circulation of the haemolymph is increased. The Triatominae circulatory system is quite simple, including the dorsal vessel, which pumps haemolymph in an anterograde direction. The return is caused by peristaltic contractions of the anterior midgut. Triatominae insects can spend several weeks without feeding, meaning that most of the time, the insect is in a resting condition. Although the mechanisms controlling the circulation of the haemolymph during post-prandial diuresis have been largely analysed, the mechanisms controlling it during resting conditions are poorly understood. In this study, we analysed several canonical pathways (i.e. L-type VGCC, GPCR, RyR, IP3R) and a novel system represented by the recently characterized Piezo proteins. Our results show that during the resting condition, haemolymph circulation depends on a cross-talk between myogenic activity, inhibitory and stimulatory cellular messengers, and Piezo proteins. This report also unveils for the first time the existence of a putative Piezo protein in Hemiptera.

Seasonal life cycle of Pintomyia longiflocosa (Diptera: Psychodidae) under semi-controlled conditions in the Huila state, Colombia.

BACKGROUND: Pintomyia longiflocosa is considered a vector of etiological agents of cutaneous leishmaniasis. The objective of this research was to establish the parameters of the life cycle of Pi. longiflocosa in semi-controlled conditions in a rural area of the Campoalegre municipality, Huila, Colombia. METHODOLOGY/PRINCIPAL FINDINGS: The life cycle of individuals of Pi. longiflocosa, obtained from two cohorts of collected, fed, and individualized females, was monitored during two different times of the year (between February and August 2020 and between July 2020 and January 2021, respectively). Determining parameters associated with the fertility and fecundity, time and attributes of development and survival, and its association with abiotic variables. The average duration of Cycle 1 (C1) and Cycle 2 (C2) was 134.9 and 148.78 days, respectively. The gonotrophic cycle of parental females presented significant differences (p-value <0.05) between C1 and C2 (8.47 and 11.42 days) as well as between fecundity and fertility parameters. The number of days it takes the development of the immature stages between the two cycles studied, also showed significant differences in the larvae II (15.21 and 22.23), larvae III (11.93 and 17.56), and pupae (24.48 and 22.9) stages. During C1, the survival rate was higher and consistent with the productivity of adult individuals (F1), compared to C2. Fecundity and fertility values were significantly higher in C2. Finally, a significant correlation between the number of individuals and temperature was evidenced in C1 while, for C2, there was a negative correlation with precipitation. CONCLUSIONS/SIGNIFICANCE: Significant differences were found in several biological and reproductive parameters between the two cycles monitored. The parameters of the life cycle of Pi. longiflocosa in its natural habitat would be influenced by environmental factors related to the annual seasonality in the sub-Andean rural area, conditioning the temporal distribution of this species and, consequently, the possible transmission of causative agents of cutaneous leishmaniasis.