Entomological study on vectorial density, temporal variation of tsetse fly and other biting flies in intervention and non-intervention areas of South Omo Zone, Ethiopia.

A repeated cross-sectional entomological survey was conducted to estimate Glossina (tsetse) and other biting flies density, their seasonal variation and associated risk factors in intervention and non- intervention areas of South Omo Zone, Southwest Ethiopia from January 2019-November 2019. In both dry and wet seasons, a total of 96 NGU traps (64 traps in tsetse intervention districts and 32 traps in tsetse non- intervention districts) were deployed at an interval of about 100-200 m in purposively selected and suspected tsetse habitats. Thus, Glossina pallidipes was found to be the only cyclical vector along with mechanical vectors of Tabanus, Stomoxys and Haematopota. In tsetse intervention areas, G. pallidipes apparent density of 2.64 F/T/D and 0.42 F/T/D was recorded in dry and wet season respectively. Mechanical vectors (dry; wet) of Tabanus (205; 155), Stomoxys (34; 54) and Haematopota (50; 33) were also recorded in tsetse intervened areas. Whereas, in non- intervention areas, apparent density of G. pallidipes was 2.03 F/T/D and 0.56 F/T/D, respectively in dry and wet season. Similarly, Tabanus (22; 56), Stomoxys (10; 8) and Haematopota (5; 7) respectively in dry and wet (dry; wet) season were recorded in tsetse non- intervention areas. According to Negative Binomial Regression (NBR), season was the only variable significantly affecting (P < 0.05) the Glossina count in the current study area. Accordingly, the incidence G. pallidipes during wet season was decreased by the factor of 0.21 (CI; 0.097-0.47) when compared to its incidence in dry season by holding other variables constant. In conclusion, cyclical vectors were playing vital role in transmission of trypanosomosis in South Omo Zone along with numerous mechanical vectors even though there have been vector intervention activities in the areas. Therefore, strong, sustainable, environmentally friend and community participating vector control strategies should be followed to tackle the vector distribution in the area.

An evaluation of repellency and feeding inhibition of ethno-medicinal plants against major malaria vectors in southern Ethiopia.

BACKGROUND: Plant-based mosquito control methods may use as a supplementary malaria vector control strategy. This study aimed to evaluate the effect of smoking ethno-medicinal plants on indoor density and feeding activity of malaria vectors at early hours of the night and its residual effect after midnight in southern Ethiopia. METHODS: Both field and tent trials were conducted to evaluate the impact of smoking Juniperus procera leaves, Eucalyptus globulus seeds and Olea europaea leaves in Kolla Shara Village from July 2016 to February 2017. For the field trial, five grass-thatched traditional huts (three for ethno-medicinal plants and two as control [only charcoal smoking and non-charcoal smoking]) were used. Indoor host-seeking mosquitoes were collected by CDC light traps. A Latin square design was employed to minimize the bias due to the variation in house location and different sampling nights. For the tent experiment, 25 3-5-day-old starved wild female Anopheles mosquitoes reared from the larvae were released into the tents where a calf was tethered at the mid-point of each tent. RESULTS: A total of 614 Anopheles mosquitoes belonging to 5 species were collected from 5 huts, of which 93.4% was An. arabiensis; O. europaea, E. globulus and J. procera reduced the indoor density of An. arabiensis, with the mean percentage drop of 80%, 73% and 70%, respectively. In the tent trial, smoking of these plants had significant knockdown effects and inhibited feeding on the calves (F = 383.5, DF = 3, P < 0.01). The mean knockdown effect due to O. europaea was relatively high (17.7 ± 0.54; 95% CI 16.8-18.6), while it was only 0.9 ± 0.1 (95% CI 0.29-1.52) in the control tents. All the test plants used in the tent trial caused significantly inhibited feeding activity of An. arabiensis on the host (F = 383.5, DF = 3, P < 0.01). About 94.5%, 89.5% and 86% of mosquitoes were unfed because of the smoking effect of O. europaea, E. globulus and J. procera, respectively, whereas only 19.5% were unfed in the control tent. CONCLUSIONS: Smoking ethno-medicinal plant materials reduced indoor density of malaria vectors and inhibited feeding on calves inside the tents. Thus, plant-based mosquito control methods may play a vital role in reducing mosquito bites in the early hours of the night and thereby reduce residual malaria transmission.