Evaluation of radiation sensitivity and mating performance of Glossina brevipalpis males

BACKGROUND : Area-wide integrated pest management strategies that include a sterile insect technique component have been successfully used to eradicate tsetse fly populations in the past. To ensure the success of the sterile insect technique, the released males must be adequately sterile and be able to compete with their native counterparts in the wild. METHODOLOGY/PRINCIPAL FINDINGS : In the present study the radiation sensitivity of colonised Glossina brevipalpis Newstead (Diptera; Glossinidae) males, treated either as adults or pupae, was assessed. The mating performance of the irradiated G. brevipalpis males was assessed in walk-in field cages. Glossina brevipalpis adults and pupae were highly sensitive to irradiation, and a dose of 40 Gy and 80 Gy induced 93% and 99% sterility respectively in untreated females that mated with males irradiated as adults. When 37 to 41 day old pupae were exposed to a dose of 40 Gy, more than 97% sterility was induced in untreated females that mated with males derived from irradiated pupae. Males treated as adults with a dose up to 80 Gy were able to compete successfully with untreated fertile males for untreated females in walk-in field cages. CONCLUSIONS/SIGNIFICANCE : The data emanating from this field cage study indicates that, sterile male flies derived from the colony of G. brevipalpis maintained at the Agricultural Research Council-Onderstepoort Veterinary Institute in South Africa are potential good candidates for a campaign that includes a sterile insect technique component. This would need to be confirmed by open field studies.The Research was done in collaboration with the Joint Food and Agriculture Organization/ International Atomic Energy Agency Division of Nuclear Techniques in Food and Agriculture under the coordinated research project 17753/R0.http://www.plosntds.orgam2017Veterinary Tropical Disease

Development and characterization of microsatellite markers for the tsetse species Glossina brevipalpis and preliminary population genetics analyses

Tsetse flies, the vectors of African trypanosomes are of key medical and economic importance and one of the constraints for the development of Africa. Tsetse fly control is one of the most effective and sustainable strategies used for controlling the disease. Knowledge about population structure and level of gene flow between neighbouring populations of the target vector is of high importance to develop appropriate strategies for implementing effective management programmes. Microsatellites are commonly used to identify population structure and assess dispersal of the target populations and have been developed for several tsetse species but were lacking for Glossina brevipalpis. In this study, we screened the genome of G. brevipalpis to search for suitable microsatellite markers and nine were found to be efficient enough to distinguish between different tsetse populations. The availability of these novel microsatellite loci will help to better understand the population biology of G. brevipalpis and to assess the level of gene flow between different populations. Such information will help with the development of appropriate strategies to implement the sterile insect technique (SIT) in the framework of an area-wide integrated pest management (AW-IPM) approach to manage tsetse populations and ultimately address the trypanosomoses problem in these targeted areas

A distribution model for Glossina brevipalpis and Glossina austeni in southern Mozambique, Eswatini and South Africa for enhanced area-wide integrated pest management approaches

BACKGROUND : Glossina austeni and Glossina brevipalpis (Diptera: Glossinidae) are the sole cyclical vectors of African trypanosomes in South Africa, Eswatini and southern Mozambique. These populations represent the southernmost distribution of tsetse flies on the African continent. Accurate knowledge of infested areas is a prerequisite to develop and implement efficient and cost-effective control strategies, and distribution models may reduce large-scale, extensive entomological surveys that are time consuming and expensive. The objective was to develop a MaxEnt species distribution model and habitat suitability maps for the southern tsetse belt of South Africa, Eswatini and southern Mozambique. METHODOLOGY/PRINCIPAL FINDINGS : The present study used existing entomological survey data of G. austeni and G. brevipalpis to develop a MaxEnt species distribution model and habitat suitability maps. Distribution models and a checkerboard analysis indicated an overlapping presence of the two species and the most suitable habitat for both species were protected areas and the coastal strip in KwaZulu-Natal Province, South Africa and Maputo Province, Mozambique. The predicted presence extents, to a small degree, into communal farming areas adjacent to the protected areas and coastline, especially in the Matutuíne District of Mozambique. The quality of the MaxEnt model was assessed using an independent data set and indicated good performance with high predictive power (AUC > 0.80 for both species). CONCLUSIONS/SIGNIFICANCE : The models indicated that cattle density, land surface temperature and protected areas, in relation with vegetation are the main factors contributing to the distribution of the two tsetse species in the area. Changes in the climate, agricultural practices and land-use have had a significant and rapid impact on tsetse abundance in the area. The model predicted low habitat suitability in the Gaza and Inhambane Provinces of Mozambique, i.e., the area north of the Matutuíne District. This might indicate that the southern tsetse population is isolated from the main tsetse belt in the north of Mozambique. The updated distribution models will be useful for planning tsetse and trypanosomosis interventions in the area.S1 Fig. Uncertainty grid for the habitat suitability index model for Glossina austeni and Glossina brevipalpis (https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10. 7910/DVN/PA7U7L).The Joint Food and Agriculture Organization of the United Nations (FAO)/ International Atomic Energy Agency (IAEA) Centre of Nuclear Techniques in Food and Agriculture and the IAEA’s Department of Technical Cooperation; the IAEA’s Department of Technical Cooperation; the Department of Science and Technology and the GeosAf project.http://www.plosntds.orgam2022Veterinary Tropical Disease

Développement et caractérisation de marqueurs microsatellites pour l’espèce de mouche tsé-tsé Glossina brevipalpis et analyses génétiques préliminaires des populations

DATA AVAILABILITY STATEMENT : Materials described in the paper, including all relevant raw data, are available in this link: https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10.7910/DVN/SDRST2. Unpublished sequence data from Otto Koekemoer is available upon reasonable request from the corresponding author.Tsetse flies, the vectors of African trypanosomes are of key medical and economic importance and one of the constraints for the development of Africa. Tsetse fly control is one of the most effective and sustainable strategies used for controlling the disease. Knowledge about population structure and level of gene flow between neighbouring populations of the target vector is of high importance to develop appropriate strategies for implementing effective management programmes. Microsatellites are commonly used to identify population structure and assess dispersal of the target populations and have been developed for several tsetse species but were lacking for Glossina brevipalpis. In this study, we screened the genome of G. brevipalpis to search for suitable microsatellite markers and nine were found to be efficient enough to distinguish between different tsetse populations. The availability of these novel microsatellite loci will help to better understand the population biology of G. brevipalpis and to assess the level of gene flow between different populations. Such information will help with the development of appropriate strategies to implement the sterile insect technique (SIT) in the framework of an area-wide integrated pest management (AW-IPM) approach to manage tsetse populations and ultimately address the trypanosomoses problem in these targeted areas.Les mouches tsé-tsé, vecteurs des trypanosomes africains, sont d’une importance médicale et économique majeure et l’une des contraintes pour le développement de l’Afrique. La lutte contre la mouche tsé-tsé est l’une des stratégies les plus efficaces et durables utilisées pour contrôler la maladie. La connaissance de la structure de la population et du niveau de flux de gènes entre les populations voisines du vecteur cible est d’une grande importance pour développer des stratégies appropriées pour la mise en œuvre de programmes de gestion efficaces. Les microsatellites sont couramment utilisés pour identifier la structure de la population et évaluer la dispersion des populations cibles et ont été développés pour plusieurs espèces de glossines mais manquaient pour Glossina brevipalpis. Dans cette étude, nous avons criblé le génome de G. brevipalpis pour rechercher des marqueurs microsatellites appropriés et neuf ont été trouvés suffisamment efficaces pour faire la distinction entre différentes populations de glossines. La disponibilité de ces nouveaux locus microsatellites aidera à mieux comprendre la biologie des populations de G. brevipalpis et à évaluer le niveau de flux de gènes entre différentes populations. Ces informations aideront à l’élaboration de stratégies appropriées pour mettre en œuvre la technique de l’insecte stérile dans le cadre d’une approche de lutte antiparasitaire intégrée à l’échelle de la zone pour gérer les populations de glossines et, en fin de compte, résoudre le problème des trypanosomoses dans les zones concernées.The Joint FAO/IAEA Insect Pest Control Subprogramme and the IAEA’s Department of Technical Cooperation.http://www.parasite-journal.orghj2024Veterinary Tropical DiseasesSDG-03:Good heatlh and well-bein

Prevalence of Trypanosoma and Sodalis in wild populations of tsetse flies and their impact on sterile insect technique programmes for tsetse eradication

The sterile insect technique (SIT) is an environment friendly and sustainable method to manage insect pests of economic importance through successive releases of sterile irradiated males of the targeted species to a defined area. A mating of a sterile male with a virgin wild female will result in no offspring, and ultimately lead to the suppression or eradication of the targeted population. Tsetse flies, vectors of African Trypanosoma, have a highly regulated and defined microbial fauna composed of three bacterial symbionts that may have a role to play in the establishment of Trypanosoma infections in the flies and hence, may influence the vectorial competence of the released sterile males. Sodalis bacteria seem to interact with Trypanosoma infection in tsetse flies. Field-caught tsetse flies of ten different taxa and from 15 countries were screened using PCR to detect the presence of Sodalis and Trypanosoma species and analyse their interaction. The results indicate that the prevalence of Sodalis and Trypanosoma varied with country and tsetse species. Trypanosome prevalence was higher in east, central and southern African countries than in west African countries. Tsetse fly infection rates with Trypanosoma vivax and T. brucei sspp were higher in west African countries, whereas tsetse infection with T. congolense and T. simiae, T. simiae (tsavo) and T. godfreyi were higher in east, central and south African countries. Sodalis prevalence was high in Glossina morsitans morsitans and G. pallidipes but absent in G. tachinoides. Double and triple infections with Trypanosoma taxa and coinfection of Sodalis and Trypanosoma were rarely observed but it occurs in some taxa and locations. A significant Chi square value (< 0.05) seems to suggest that Sodalis and Trypanosoma infection correlate in G. palpalis gambiensis, G. pallidipes and G. medicorum. Trypanosoma infection seemed significantly associated with an increased density of Sodalis in wild G. m. morsitans and G. pallidipes flies, however, there was no significant impact of Sodalis infection on trypanosome density.The Joint FAO/IAEA Insect Pest Control Subprogramme.https://www.nature.com/srepVeterinary Tropical Disease

Glossina brevipalpis (Diptera : Glossinidae) in South Africa : distribution, endosymbionts and assessment of irradiated male mating proficiency

MSc (Integrated Pest Management), North-West University, Potchefstroom CampusGlossina brevipalpis found in the north-eastern KwaZulu-Natal Province of South Africa represents the southernmost distributional limit of this genus in Africa. This species covers approximately 18 000 km2 where it co-occurs with its congener G. austeni. An Area Wide-Integrated Pest Management (AW-IPM) strategy that include Sterile Insect Technique (SIT) component was proposed to establish a tsetse free status in South Africa. Initially, this study was designed to only focus on G. brevipalpis however due to the crucial role played by G. austeni in the transmission of trypanosome parasites that cause nagana in South Africa it was included and any control effort needs to consist of both species. This study was aimed at investigating the current apparent density (AD) of the two populations. Subsequently, this study also assessed the male mating ability and the multi mating behavior of the G. brevipalpis. In addition, the detection and abundance of the symbionts (Sodalis and Spiroplasma) harboured by wild captured flies colonized flies as well as to determine the prevalence of trypanosome parasites from wild captured flies. The Apparent Density (AD) of the two tsetse flies were determined using entomological surveys conducted at five protected and four communal farming sites in 2008-2009 and compared to that of 2018-2019. An overall abundance of G. brevipalpis was significantly higher (p 0.01) in AD from 0.21 in 2008-2009 to 0.14 AD flies/trap/day in 2018-2019 was observed in G. austeni populations from protected areas. These results indicated that the current tsetse control program, as applied in the communal farming areas, doesn’t have a substantial long-term effect on tsetse abundance and suggest that more efficient control measures be implemented in the affected areas of north-eastern KwaZulu-Natal Province of South Africa. In preparation of the SIT, male mating ability and the female multi mating behavior of G.brevipalpis were determined. For the male mating ability, the flies were given aradiation dose of 80 Gy and allowed to first mate with the 3 days old virgin females followed by second mating with fertile non-irradiated males. Both irradiated and non-irradiated males have shown the potential to mate several times and the propensity of mating as well as the ability to transfer sperm does not decline significantly (p > 0.05) in subsequent mating events. Irradiated males were able to inseminate several females comparable to that on non-irradiated males. The spermatheca fill in females that mated with non-irradiated and irradiated males did not differ. The multi-mating potential of the male tsetse flies from the colony indicated their suitability to be used for SIT based on their mating performance. The multi mating behavior of G. brevipalpis females that first mated with irradiated and then with fertile males was determined under laboratory conditions. As expected, high numbers of pupae were produced by the females that only mated with the fertile males. Females which were only inseminated by irradiated males were going through recurring cycles of aborted eggs. The results showed that younger females appear to be more receptive to a second mating compared to older females. The detection of endosymbionts DNA with species-specific PCR primers were determined. Sodalis were abundant in colonized G. brevipalpis and relatively low in field collected flies and was not detected in both colonized and field collected G. austeni. Spiroplasma DNA was detected from 37% colonized G. brevipalpis and 30% colonized G. austeni. Trypanosome DNA was detected in 17.4% of field collected tsetse assayed with a high prevalence of Trypanosoma congolense and T. theileri. The initiative to eliminate AAT and tsetse in South Africa need to be supported by accurate information of geographic distribution of tsetse populations as well as information on which Trypanosoma species are prevalent. Such baseline information is crucial when selecting most cost-effective strategy of intervention of the priority areas. This study highlighted that effective control measures are essential in affected areas of north-eastern-KwaZulu-Natal Province. Secondly, this study demonstrated that ARC-OVR tsetse colony flies are suitable to be used in tsetse eradication campaigns in South Africa. Lastly, this study could play a vital role in the decision making on the environmentally friendly tsetse control method that can be implemented in southern Africa.Master

Gamma irradiation and male Glossina austeni mating performance

An area-wide integrated pest management (AW-IPM) strategy with a sterile insect technique (SIT) component has been proposed for the management of African animal trypanosomosis (AAT) in South Africa. In preparation for the SIT, the mating performance of colony reared Glossina austeni males under influencing factors such as radiation dose and the development stage that is exposed to radiation, was assessed under laboratory and semi-field conditions. The radiation sensitivity of G. austeni colonized 37 years ago when treated as adults and late-stage pupae was determined. Radiation doses of 80 Gy and 100 Gy induced 97–99% sterility in colony females that mated with colony males treated as adults or pupae. Males irradiated either as adults or pupae with a radiation dose of 100 Gy showed similar insemination ability and survival as untreated males. Walk-in field cage assessments indicated that a dose of up to 100 Gy did not adversely a ect the mating performance of males irradiated as adults or late stage pupae. Males irradiated as adults formed mating pairs faster than fertile males and males irradiated as pupae. The mating performance studies indicated that the colonized G. austeni males irradiated as adults or late stage pupae will still be suited for SIT.IAEAhttp://www.mdpi.com/journal/insectsam2020Veterinary Tropical Disease

Number of irradiated male (40 or 80 Gy) and untreated male (0 Gy) <i>Glossina brevipalpis</i> that mated with untreated females in a field cage.

<p>Each box shows the group median separating the 25^th and 75^th quartiles, capped bars indicate maximum and minimum values, circles indicating the outliners.</p

Effect of the developmental stage (age of pupa or adult) (β₁) at time of and dose (β₂) of irradiation on the survival of the male flies determined at 14 day intervals.

<p>Effect of the developmental stage (age of pupa or adult) (β₁) at time of and dose (β₂) of irradiation on the survival of the male flies determined at 14 day intervals.</p

Emergence rate of adult <i>Glossina brevipalpis</i> irradiated as pupae with different doses and on different days Post Larviposition (PL).

<p>Emergence rate of adult <i>Glossina brevipalpis</i> irradiated as pupae with different doses and on different days Post Larviposition (PL).</p