Xenomonitoring of trypanosome infectivity in Tse tse flies from Kagarko Local Government Area, Kaduna State Nigeria

Trypanosomiasis is a re-emerging neglected tropical disease, afflicting domestic, wild animals and humans. In this study, the tsetse fly infectivity and species composition of Trypanosoma species were determined in Kagarko Local Government Area, Kaduna State Nigeria using entomological protocol. The tsetse flies were sampled using standard biconical traps and the flies collected were dissected for trypanosome using microscopy as well as expression of tsetse antigen 5 (TAg 5) using molecular tools. Forty seven (47) tsetse flies were collected over a period of four months, of which 13 (34.21%) were infected with Trypanosoma spp. The species of trypanosome identified include T. vivax 7(53.85%), T. congolense 5(38.46%) and T. brucei 1(7.69%), while expression of TAg 5 was observed in four of the examined flies. The presence of the flies with trypanosome of veterinary and medical importance demonstrate the risk of transmission of trypanosomiasis in the study area.

An update on the distribution of Glossina (tsetse flies) at the wildlife-human-livestock interface of Akagera National Park, Rwanda

Background Glossina (tsetse flies) biologically transmit trypanosomes that infect both humans and animals. Knowledge of their distribution patterns is a key element to better understand the transmission dynamics of trypanosomosis. Tsetse distribution in Rwanda has not been well enough documented, and little is known on their current distribution. This study determined the current spatial distribution, abundance, diversity, and seasonal variations of tsetse flies in and around the Akagera National Park. Methods A longitudinal stratified sampling following the seasons was used. Biconical traps were deployed in 55 sites for 6 consecutive days of each study month from May 2018 to June 2019 and emptied every 48 h. Flies were identified using FAO keys, and the number of flies per trap day (FTD) was used to determine the apparent density. Pearson chi-square (χ2) and parametrical tests (t-test and ANOVA) were used to determine the variations between the variables. The significance (p < 0.05) at 95% confidence interval was considered. Logistic regression was used to determine the association between tsetse occurrence and the associated predictors. Results A total of 39,516 tsetse flies were collected, of which 73.4 and 26.6% were from inside Akagera NP and the interface area, respectively. Female flies accounted for 61.3 while 38.7% were males. Two species were identified, i.e. G. pallidipes [n = 29,121, 7.4 flies/trap/day (FTD)] and G. morsitans centralis (n = 10,395; 2.6 FTD). The statistical difference in numbers was significant between the two species (p = 0.000). The flies were more abundant during the wet season (15.8 FTD) than the dry season (4.2 FTD). Large numbers of flies were trapped around the swamp areas (69.1 FTD) inside the park and in Nyagatare District (11.2 FTD) at the interface. Glossina morsitans was 0.218 times less likely to occur outside the park. The chance of co-existing between the two species reduced outside the protected area (0.021 times). Conclusions The occurrence of Glossina seems to be limited to the protected Akagera NP and a narrow band of its surrounding areas. This finding will be crucial to design appropriate control strategies. Glossina pallidipes was found in higher numbers and therefore is conceivably the most important vector of trypanosomosis. Regional coordinated control and regular monitoring of Glossina distribution are recommended. Graphic Abstract

Sodalis Glossinidius and Wolbachia Infections in Wild Population of Glossina Morsitans Submorsitans Caught in the Area of Lake Iro in the South of Chad

Background: To improve vector control of tsetse transmitted trypanosomiases through a better understanging of the vectorial competence of tsetse flies, investigations have been undertaken on the bacterial fauna of different tsetse species. It is in this light that Wolbachia and Sodalis glossinidius were detected in wild populations of Glossina morsistans submorsistans caught in the area of lake Iro in the south of Chad with the aim of generating data that may help to understand the influence of these symbiotic microorganisms on the vectorial competence of G. m. submorsistans. Methods: Tsetse flies were captured using biconical traps. DNA was extracted from tsetse body using the resin chelex. Sodalis glossinidius and Wolbachia were investigated by PCR using specific primers for pSG 2 and wsp genes. Comparisons between S. glossinidius and Wolbachia infections were performed according to sex and sampling periods and association studies between trypanosome infections and S. glossinidius or Wolbachia were performed. Results: From 345 G. m. submorsitans analyzed, 9.0% and 14.5% were respectively infected with S. glossinidius and Wolbachia. Only 2.31% of all tsetse flies hosted the 2 bacteria. Of all trypanosome-infected flies, 7.1% and 9.8% hosted respectively S. glossinidius and Wolbachia. No association was observed between Wolbachia and trypanosomes while significant association (r = 4.992; P = 0.025) was found between S. glossinidius and trypanosome infections. Although significant association (r = 3.147; P = 0.043) was observed between S. glossinidius and T. simiae, none was found with T. congolense or T. godfreyi. Conclusion: This study revealed S. glossinidius and Wolbachia in wild population of G. m. submorsitans of lake Iro. It showed that few tsetse flies are co-infected by Wolbachia and S. glossinidius. The presence of S. glossinidius seems to favor trypanosome infections while Wolbachia has probably no effect. Decrypting the tripartite association requires to investigate the relationship between haplotypes or genotypes of Wolbachia and/or S. glossiniduis and trypanosome infections.

An update on the distribution of Glossina (tsetse flies) at the wildlife-human-livestock interface of Akagera National Park, Rwanda

BackgroundGlossina (Tsetse flies) biologically transmit trypanosomes that infect both humans and animals. Knowledge of their distribution patterns is a key element to better understand the transmission dynamics of trypanosomosis. Tsetse distribution in Rwanda has not been well enough documented and little is known of their current distribution. This study determined the current spatial distribution, abundance, diversity, and seasonal variations of tsetse flies in and around the Akagera National Park.MethodsA longitudinal stratified sampling, following the seasons was used. Biconical traps were deployed in 55 sites for six consecutive days of each study month from May 2018 to June 2019, and emptied every 48hours. Flies were identified using FAO keys and the number of flies per trap day (FTD) was used to determine the apparent density. Pearson chi-square (χ2) and parametrical tests (t-test and ANOVA) were used to determine the variations between the variables. The significance (p< 0.05) at 95% confidence interval was considered. Logistic regression was used to determine the association between tsetse occurrence and the associated predictors. Results39,516 tsetse flies were collected, of which 73.4% and 26.6% were from inside Akagera NP and the interface area respectively. Female flies accounted for 61.3% while 38.7% were males. Two species were identified, i.e. G. pallidipes [n=29,121, 7.4 flies/trap/day (FTD)] and G. morsitans centralis (n=10,395; 2.6 FTD). The statistical difference in numbers was significant between the two species (p=0.000). The flies were more abundant during the wet season (15.8 FTD) than the dry season (4.2 FTD). Large numbers of flies were trapped around the swamp areas (69.1 FTD) inside the park and in Nyagatare District (11.2 FTD) at the interface. Glossina morsitans was 0.218 times less likely to occur outside the park. The chance of co-existing between the two species reduced outside the protected area (0.021 times).ConclusionsThe occurrence of Glossina seems to be limited to the protected Akagera NP and a narrow band in its surroundings. This finding will be crucial to design appropriate control strategies. Glossina pallidipes was found in higher numbers and therefore conceivably the most important vector of trypanosomosis. Regional coordinated control and regular monitoring of Glossina distribution are recommended.

Comparative performance of traps in catching tsetse flies (Diptera: Glossinidae) in Tanzania

This study was conducted to determine the efficiency of different tsetse traps in 28 sites across Tanzania. The traps used were biconical, H, NGU, NZI, pyramidal, S3, mobile, and sticky panels. Stationary traps were deployed at a distance of 200 m apart and examined 72 h after deployment. The results showed that 117 (52.2%) out of the 224 traps deployed captured at least one Glossina species. A total of five Glossina species were captured, namely Glossina brevipalpis, Glossina pallidipes, Glossina swynnertoni, Glossina morsitans, and Glossina fuscipes martinii. Biconical traps caught tsetse flies in 27 sites, pyramidal in 26, sticky panel in 20, mobile in 19, S3 in 15, NGU in 7, H in 2 and NZI in 1. A total of 21 107 tsetse flies were trapped, with the most abundant species being G. swynnertoni (55.9%), followed by G. pallidipes (31.1%), G. fuscipes martinii (6.9%) and G. morsitans (6.0%). The least caught was G. brevipalpis (0.2%). The highest number of flies were caught by NGU traps (32.5%), followed by sticky panel (16%), mobile (15.4%), pyramidal (13.0%), biconical (11.3%) and S3 (10.2%). NZI traps managed to catch 0.9% of the total flies and H traps 0.7%. From this study, it can be concluded that the most efficient trap was NGU, followed by sticky panel and mobile, in that order. Therefore, for tsetse fly control programmes, NGU traps could be the better choice. Conversely, of the stationary traps, pyramidal and biconical traps captured tsetse flies in the majority of sites, covering all three ecosystems better than any other traps; therefore, they would be suitable for scouting for tsetse infestation in any given area, thus sparing the costs of making traps for each specific Glossina species.Keywords: tseste; traps; densties; Glossina; mobile; stationary; Tanzania

Feeding Patterns and Xenomonitoring of Trypanosomes among Tsetse Flies around the Gashaka-Gumti National Park in Nigeria

In order to understand the epidemiology of trypanosomoses in Gashaka-Gumti National Park, Nigeria, we determined the density, infection rates, and feeding patterns of tsetse flies using biconical traps, ITS, and mitochondrial cytochrome b PCRs. A total of 631 tsetse flies were captured, of which 531 (84.2%) and 100 (15.8%) were analyzed for trypanosomes and blood meals, respectively. Tsetse distribution varied significantly (p<0.05) across study sites with average trap and daily catches of 4.39 and 26.34, respectively. Overall tsetse infection rate was 5.08% and ranged between 3.03% and 6.84% across study sites. We identified 10T. brucei, 3T. congolense savannah,2T. congolense forest, and 2 mixed infections among the 13 pools made from the 27 flies positive for trypanosomes with light microscopy. The distribution of vertebrate blood meals in tsetse flies varied significantly (p<0.05) and ranged between 6.0% and 45% across hosts. We also observed dual feeding patterns involving at least 2 hosts in 24% and multiple feeding involving at least 3 hosts in 17% of the flies. We observed predominance ofG. palpaliswhich also recorded higher infection rate.T. bruceiwas more prevalent among tsetse flies. Tsetse flies fed predominantly on cattle and less frequently on humans and also showed mixed feeding habits.

Development of odour-baited traps for Glossina swynnertoni (Diptera: Glossinidae)

Three new prototype traps, (S1–S3), were developed during studies of the behavioural ecology of Glossina swynnertoni Austen in Kenya and Tanzania. The traps were compared in latin square experiments relative to the regular biconical trap as a standard and a selection of other conventional tsetse traps. Observations were also made on fly behaviour in the vicinity of traps using electric nets and sticky materials. When baited with acetone and 1-octen-3-ol, the S1 trap was 3.5 times as effective in catching G. swynnertoni in Kenya as the biconical trap. In Tanzania, the relative performance of the S1 and biconical traps differed; also, both traps were found to be inferior to an all-black, sticky 1-m2target. A second prototype (S2) performed slightly better than the biconical trap, but was still inferior to the black target. The final prototype (S3) was 2.9 times as effective as the biconical trap and performed as well as the black target. The potential for further improvement of traps for capturing G. swynnertoni and flies of the G. morsitans Westwood group is discussed.

Responses of Glossina fuscipes fuscipes (Diptera: Glossinidae) and other Diptera to carbon dioxide in linear and dense forests

The responses of Glossina fuscipes fuscipes Newstead and other Diptera to carbon dioxide were studied in linear and dense forests along the shores of Lake Victoria, Kenya. Flies were caught in biconical traps and were intercepted with electric nets while in flight near traps. Carbon dioxide dispensed at a high rate (5 l min–1) in linear forest failed to increase the numbers of tsetse attracted to or caught in traps. In contrast, catches of non-biting Muscidae, Stomoxyinae and Tabanidae were improved by up to 11 times. Inside dense forest, carbon dioxide released at half this rate increased both the numbers of female tsetse attracted to a trap and the catches in a trap by about 2–3 times. Catches of male tsetse were, however, not affected. Striking improvements for other Diptera were also realized (up to 102 times). Under a variety of conditions, unbaited biconical traps attracted many Diptera to the vicinity of a trap, but caught few flies due to low capture efficiencies (typically less than 10%). In contrast, efficiency estimates for G. f. fuscipes were good, varying from 37 to 82% in different habitats and seasons. These results are discussed in relation to the search for practical odour attractants for riverine tsetse.

Olfactory responses of Glossina fuscipes fuscipes (Diptera: Glossinidae) to the monitor lizard Varanus niloticus niloticus

Visual and olfactory responses of Glossina fuscipes fuscipes Newstead to the monitor lizard, Varanus niloticus niloticus Laurenti were studied using various catching devices near Lake Victoria, Kenya. Electric nets baited with visible lizards caught more males (×2.1) and significantly more females (×2.0) than unbaited nets. Lizards concealed in electrified black PVC pipe models, simulating the shape and size of a monitor lizard, increased significantly the catches of tsetse by 2.1 times. Fresh lizard urine dispensed at an evaporation rate of 500 to 1000 mg/h also increased significantly the catches of flies at biconical traps, electrified models and electric nets. Identification of chemical constituents of the odour could improve monitoring and control strategies for G. f. fuscipes, and possibly for other palpalis tsetse species.