Spatial analysis of G.f.fuscipes abundance in Uganda using Poisson and Zero-Inflated Poisson regression models

Background Tsetse flies are the major vectors of human trypanosomiasis of the form Trypanosoma brucei rhodesiense and T.b.gambiense. They are widely spread across the sub-Saharan Africa and rendering a lot of challenges to both human and animal health. This stresses effective agricultural production and productivity in Africa. Delimiting the extent and magnitude of tsetse coverage has been a challenge over decades due to limited resources and unsatisfactory technology. In a bid to overcome these limitations, this study attempted to explore modelling skills that can be applied to spatially estimate tsetse abundance in the country using limited tsetse data and a set of remote-sensed environmental variables. Methodology Entomological data for the period 2008–2018 as used in the model were obtained from various sources and systematically assembled using a structured protocol. Data harmonisation for the purposes of responsiveness and matching was carried out. The key tool for tsetse trapping was itemized as pyramidal trap in many instances and biconical trap in others. Based on the spatially explicit assembled data, we ran two regression models; standard Poisson and Zero-Inflated Poisson (ZIP), to explore the associations between tsetse abundance in Uganda and several environmental and climatic covariates. The covariate data were constituted largely by satellite sensor data in form of meteorological and vegetation surrogates in association with elevation and land cover data. We finally used the Zero-Inflated Poisson (ZIP) regression model to predict tsetse abundance due to its superiority over the standard Poisson after model fitting and testing using the Vuong Non-Nested statistic. Results A total of 1,187 tsetse sampling points were identified and considered as representative for the country. The model results indicated the significance and level of responsiveness of each covariate in influencing tsetse abundance across the study area. Woodland vegetation, elevation, temperature, rainfall, and dry season normalised difference vegetation index (NDVI) were important in determining tsetse abundance and spatial distribution at varied scales. The resultant prediction map shows scaled tsetse abundance with estimated fitted numbers ranging from 0 to 59 flies per trap per day (FTD). Tsetse abundance was found to be largest at low elevations, in areas of high vegetative activity, in game parks, forests and shrubs during the dry season. There was very limited responsiveness of selected predictors to tsetse abundance during the wet season, matching the known fact that tsetse disperse most significantly during wet season. Conclusions A methodology was advanced to enable compilation of entomological data for 10 years, which supported the generation of tsetse abundance maps for Uganda through modelling. Our findings indicate the spatial distribution of the G. f. fuscipes as; low 0–5 FTD (48%), medium 5.1–35 FTD (18%) and high 35.1–60 FTD (34%) grounded on seasonality. This approach, amidst entomological data shortages due to limited resources and absence of expertise, can be adopted to enable mapping of the vector to provide better decision support towards designing and implementing targeted tsetse and tsetse-transmitted African trypanosomiasis control strategies.

An Atlas to Support the Progressive Control of Tsetse-transmitted Animal Trypanosomosis in Burkina Faso

Background African animal trypanosomosis (AAT), transmitted by tsetse flies, is arguably the main disease constraint to integrated crop-livestock agriculture in sub-Saharan Africa, and African Heads of State and Government have adopted a resolution to rid the continent of this scourge. In order to sustainably reduce or eliminate the burden of AAT, a progressive and evidence-based approach is need, which must hinge on harmonized, spatially-explicit information on the occurrence of AAT and its vectors.MethodsA digital repository containing tsetse and AAT data collected in Burkina Faso between 1990 and 2019 was assembled. Data were collected either in the framework of control activities or for research purposes. Data were systematically verified, harmonized, georeferenced and integrated into a database (PostgreSQL). Entomological data on tsetse were mapped at the level of individual monitoring trap. When this was not possible, mapping done was at the level of site or location. Epidemiological data on AAT were mapped at the level of location/village.ResultsEntomological data showed that presence of four tsetse species in Burkina Faso. Glossina tachinoides was the most widespread and abundant species (56.35% of the catches), present from the eastern to the western part of the country. Glossina palpalis gambiensis was the second most abundant species (35.56%), and it was mainly found in the West. Glossina morsitans submorsitans was found at lower densities (6.11%), with a patchy distribution in the southern parts of the country. One only cluster of G. medicorum was detected (less than 0.1%), located in the Southwest. For the AAT component, data for 54,948 animal blood samples were assembled from 218 geographic locations. The samples were tested with a variety of diagnostic methods. AAT was found in all surveyed departments, including the tsetse-free areas in the North. Trypanosoma vivax and T. congolense infections were the dominant species 6.11±21.56% and 5.19±18.97% respectively), and to a lesser extend T. brucei infections (0.00±0.10%).Conclusions The atlas provides a synoptic view of the available information on tsetse and AAT distribution in Burkina Faso. Data are very scanty for most of the tsetse-free areas in the northern part of the country. Despite this limitation, this study generated a robust tool to aid the targeting of future surveillance and control activities. The development of the atlas also strengthened the collaboration between the different institutions involved in tsetse and AAT research and control in Burkina Faso, which will be crucial for future updates and the sustainability of the initiative.

Indeks Entomologi Vektor Nyamuk Aedes spp di Daerah Endemis Demam Berdarah Dengue (DBD) di Kecamatan Tanjungpinang Timur Kota Tanjungpinang Provinsi Kepulauan Riau

Dengue hemorrhagic fever (DHF) is still a health problem in Indonesia. This study aims to determine the vector entomology index of Aedes spp mosquitoes in dengue endemic areas in the East Tanjungpinang District, Tanjungpinang City. The study was conducted in January-March 2020 with a cross sectional method. The research locations in DHF endemic areas are Batu 9 and Bulang villages. Entomological data were analyzed descriptively. The results showed that the value of the House index for Batu 9 was 45% and Kampung Bulang was 38.8%. The Containteir index value is 12.6% in Batu 9 and Kampung Bulang. The Breteau index value in Kelurahan Batu 9 was 76% and Kampung Bulang was 68%, while the Larva free rate in Batu 9 was 55% and 61% in Kampung Bulang Village. Density of dengue vector larvae based on HI, CI and BI in both DHF endemic villages is on a scale of 4-7 and is included in the medium and high risk categories. This explains that the entomological index in East Tanjungpinang District is still low, so it is necessary to control Aedes spp larvae by draining the bath, closing water storage, conducting mosquito nest eradication, and burying used goods so that they do not become a breeding place for DHF vectors.

La Crosse virus spread within the mosquito population in Knox County, TN

In Appalachia, La Crosse virus (LACV) is a leading pediatric arbovirus and public health concern for children under 16 years. LACV is transmitted via the bite of an infected Aedes mosquito. Thus, it is imperative to understand the dynamics of the local vector population in order to assess risk and transmission. Using entomological data collected from Knox County, Tennessee in 2013, we formulate an environmentally-driven system of ordinary differential equations to model mosquito population dynamics over a single season. Further, we include infected compartments to represent LACV transmission within the mosquito population. Findings suggest that the model, with dependence on degree days and accumulated precipitation, can closely describe field data. This model confirms the need to include these environmental variables when planning control strategies.

Geographic Information System enabled dengue surveillance system in south zone, Bangalore city: A pilot study

Introduction: The Public Health Information and Epidemiological Cell (PHIEC) of Bruhat Bengaluru Mahanagara Palike (BBMP) utilizes the Geographic Information System (GIS) enabled integrated surveillance for collection, integration, analysis and reporting of geo-referenced epidemiological diseases in Bangalore city. Dengue fever is an emerging disease and there are minimum studies conducted in India about the GIS enabled dengue surveillance system. Objective: To assess the relationship between dengue cases and vector indices as depicted in the GIS map. Methodology: Data regarding dengue confirmed cases was obtained from PHIEC and entomological surveillance data from Urban Primary Health Centres (UPHC) for May to July 2017 in south zone of Bangalore city and active data collection was done for August and September 2017. Results: There was significant association between the number of dengue cases and the Breteau index in the month of September. However, there was no association between vector indices and the number of cases during the month of October. In some wards, contrary findings were noted between dengue vector indices and number of cases reported. Conclusion: There was a relationship between reported dengue cases and vector indices and there is a need for incorporation of entomological data into GIS system along with epidemiological and intervention data. Involvement of more private and government health care providers may help answer the gap between entomological data and number of dengue cases.

Relative Roles of Blow Flies (Diptera: Calliphoridae) and Invasive Fire Ants (Hymenoptera: Formicidae: Solenopsis spp.) in Carrion Decomposition

Fire ants (Solenopsis spp.) have increasingly been reported from carrion in the southeastern United States and are now a part of the normal succession community. There have been previous observations of these ants altering carrion and preying on other carrion-attendant fauna; however, the overall effects of these activities on carrion decomposition rates, community composition, and blow fly larval development are poorly understood. Alteration of these ecological processes by fire ants could affect the forensic interpretation of entomological data. We conducted a study in Mississippi and Florida whereby portions of the succession fauna were excluded from access to pig carrion to study the relative effects of fire ants and blow flies on carrion decomposition and succession: a control with all fauna having access, a second treatment where fire ants and other geophilic taxa were excluded, and a third treatment in which blow flies and other large organisms were excluded. Fire ants inflicted lesions in the carrion, buried portions that touched the ground, and preyed on some members of the succession fauna. Their exclusion did not affect carrion decomposition rates that were measured but slightly affected the overall carrion community, and strongly affected the oviposition and development of blow flies. Despite the presence of fire ants early in the control, blow flies were eventually able to overcome predation of eggs and larvae, continue colonization, and complete development; however, the delay in the colonization of blow flies on carrion could affect the determination of postmortem intervals when development rates of blow flies are considered in the calculation.

Malaria vectors diversity, insecticide resistance and transmission during the rainy season in peri-urban villages of south-western Burkina Faso

Background This study reports an updated description on malaria vector diversity, behaviour, insecticide resistance and malaria transmission in the Diébougou and Dano peri-urban areas, Burkina Faso. Methods Mosquitoes were caught monthly using CDC light traps and pyrethrum spray catches. Mosquitoes were identified using morphological taxonomic keys. PCR techniques were used to identify the species of the Anopheles gambiae complex and insecticide resistance mechanisms in a subset of Anopheles vectors. The Plasmodium sporozoite infection status and origins of blood meals of female mosquitoes were determined by ELISA methods. Larvae were collected, breed in the insectary and tested for phenotypic resistance against four insecticides using WHO bioassays. Results This study contributed to update the entomological data in two peri-urban areas of Southwest Burkina Faso. Anopheles populations were mostly anthropophilic and endophilic in both areas and exhibit high susceptibility to an organophosphate insecticide. This offers an alternative for the control of these pyrethroid-resistant populations. These data might help the National Malaria Control Programme for decision-making about vector control planning and resistance management. Conclusions This study contributed to update the entomological data in two peri-urban areas of Southwest Burkina Faso. Anopheles populations were mostly anthropophilic and endophilic in both areas and exhibit high susceptibility to an organophosphate insecticide. This offers an alternative for the control of these pyrethroid-resistant populations. These data might help the National Malaria Control Programme for decision-making about vector control planning and resistance management.

Heterogeneity, Stochasticity and Complexity in the Dynamics and Control of Mosquito-Borne Pathogens

A theory for the transmission dynamics and control of malaria was developed around a set of concepts, quantities, and mathematical models introduced by Ronald Ross. Decades later, Macdonald linked Ross's models to epidemiological and entomological data, developed the concept of the basic reproductive number, R0, and proposed a rudimentary theory of control based on sensitivity to parameters. Here, we review development of the Ross–Macdonald model, present one simple version, and provide an eclectic critique of the theory based on studies conducted more recently. While mosquito populations are logically necessary for mosquito-borne pathogen transmission, the study of transmission since then shows it is noisy, heterogeneous, and complex. Heterogeneity, stochasticity, and complexity represent important challenges for applying theory in context.

Sebaran Nyamuk Pradewasa Berdasarkan Tipe Ekosistem dan Habitat Spesifik di Kabupaten Pandeglang Provinsi Banten

The vector-borne disease remains a health problem in Pandeglang District. Entomological data isimportant in the strategy of controlling the vector-borne disease. This study aimed to determine thedistribution of mosquito larvae based on specific habitat and ecosystem typea. This research is a secondarydata analysis of Rikhus Vektora 2016 in Pandeglang, Banten Province. This type of observational researchwith cross-sectional study design. The purposive sampling technique is used based on geographical andecosystem stratification. We found 12 types of environments of the six types of ecosystems (HDP, HJP, NHDP,NHJP, PDP, and PJP) that had larvae: forest (secondary, homogeneous, and coastal); lagoon; brackish waterswamp; bamboo clumps; rice fields; plantations; and residential areas. The most ecosystem types werelarvae in HJP (160 larvae) and the least larvae in NHDP (9 larvae). Species of larvae are 16 types: rice fields(Cx. vishui, Cx. tritaeniorhynchus, An. barbirostris); small hole in the ground (Anopheles sp., Culex sp.);coconut shell (Ae. albopictus, Ar. malayi, Ar. kuchingensis, Malaya sp, Culex sp.); armpit taro leaves andbanana leaves (Ae. albopictus, Malaya genurostris); freshwater swamp (Cx. vishnui, Cx. gelidus) andbrackish water (Anopheles sp.); riverside (Anopheles sp., Cx. quinquefasciatus); ditch (Culex sp.); pool (Cx.quinquefasciatus); lagoon (Anopheles sp., Culex sp.); bamboo stumps (Ae. albopictus); Limnocharis flavagarden (Culex sp.); and used bottles (Ae. albopictus). The characteristics of larvae habitat: temperature (25-33oC); pH 8-9 (67.3%); light intensity (115-32,000 lux); vegetation (12.7%); algae (3.6%); water istemporary (61.6%), inundated (78.2%) and clear (50,9%).Keywords: Habitat, Ecosystem, Larvae Vector, Pandeglang

LAMA HIDUP DAN POTENSI Culex quinquefasciatus SEBAGAI VEKTOR FILARIASIS LIMFATIK BERDASARKAN KETINGGIAN PASCA TRANSMISSION ASSESMENT SURVEY (TAS) DI KABUPATEN SUBANG, JAWA BARAT

The study on the bioecology of Lymphatic Filariasis (LF) vector is necessary to be used as a support to eliminate LF due to the lack of entomological data for LF vector in Subang, especially after the Provision of Mass Drug Administration for Filariasis Prevention. This study aims to identify mosquito species, density, behavior, longevity, presence of the filaria worm in mosquitoes, and to identify the distribution of mosquitoes in the highlands and lowlands in selected villages in Subang district. This study is part of Lymphatic filariasis (multicenter) evaluation study in Indonesia. The data was collected by using human landing collection method and vector habitat survey data. The entomological data analyzed from the calculation of Man hour density (MHD), Man biting rate (MBR), and longevity, while the relationship between variables and mosquito abundance using Pearson's correlation. The results indicated that the density of mosquitoes caught in Rancahilir was higher than Curug rendeng villages, these results are similar to the LF vector suspect mosquito (Cx. quinquefasciatus). These mosquitoes are found outdoor with peak densities at 22.00-23.00 West Indonesia Time. Altitude has an association with the density of mosquitoes (p-value 0.039). The longevity of Cx. quinquefasciatus population is 10-13 days. At that longevity, vectors are at risk for infective filarial worms. The result shows that Cx. quinquefasciatus collected in this study was negative for filarial worms. Based on the results of this study, we conclude that in Subang, filariasis transmission chain prevention has been successful. However, periodic evaluations is still need to be carried out in order to prevent re-infection of the disease. Abstrak Kajian tentang bioekologi nyamuk vektor Lymphatic Filariasis (LF) di Kabupatem Subang perlu dilakukan. Kajian ini sebagai pendukung untuk menuju eliminasi LF mengingat belum optimalnya data entomologi nyamuk vektor di Subang, terutama pasca Pemberian Obat Masal Pencegahan (POMP) filariasis. Penelitian ini bertujuan mengidentifikasi spesies, kepadatan, perilaku, umur panjang (longevity) populasi nyamuk, identifikasi keberadaan cacing filaria pada nyamuk vektor LF serta menganalisis perbedaan distribusi nyamuk pada dataran tinggi dan rendah di desa terpilih di Kabupaten Subang. Penelitian ini merupakan analisis lanjut dari penelitian “Studi evaluasi filariasis (multicenter) di Indonesia” yang dilaksanakan di beberapa kabupaten di Indonesia. Data yang diambil, yaitu data survei vektor yang menggunakan metode Human Landing Collection (HLC) dan survei habitat vektor. Analisa data entomologi menggunakan perhitungan Man hour density (MHD), Man-biting rate (MBR) dan nilai umur panjang nyamuk (longevity), sedangkan hubungan antar variabel dengan kepadatan menggunakan korelasi pearson. Hasil penelitian menunjukkan bahwa kepadatan nyamuk yang tertangkap di Desa Rancahilir (dataran rendah) lebih banyak dibandingkan di Desa Curug rendeng (dataran tinggi), termasuk kepadatan nyamuk Cx. quinquefasciatus yang juga dominan di wilayah ini. Nyamuk ini banyak ditemukan di luar rumah dengan puncak kepadatan pada jam 22.00-23.00 WIB. Ketinggian mempunyai hubungan dengan kepadatan nyamuk tertangkap (p value 0,039). Umur populasi nyamuk Cx. quinquefasciatus 10-13 hari. Umur ini menunjukkan umur populasi yang berisiko untuk infektif cacing filaria. Hasil pemeriksaan nyamuk Cx. quinquefasciatus negatif terhadap cacing filarial. Hasil ini menunjukkan bahwa di Kabupaten Subang telah berhasil memutuskan rantai penularan filaria. Namun, masih perlu dilaksanakan evaluasi berkala agar tidak terjadi penularan kembali di wilayah ini.