Abstracts of Master’s thesis

2017


Tekle Olbamo Worako. Impact of smoking local medicinal plants on indoor density and feeding activities of malaria vectors: evidence from field and tent experiments in Kolla Shara in Arba Minch area, southwest Ethiopia. 

Malaria has declined in many malaria endemic countries due to the massive scale-up of indoor based vector control interventions. However, the early biting malaria vectors may threaten the gains by maintaining the residual malaria transmission. Hence, supplementary malaria vector control tools are needed to reduce residual malaria transmission. This study aimed to evaluate the impact of smoking Juniperus procera, Eucalyptus globulus and Olea europea on indoor density and feeding activity of malaria vectors in Kolla Shara village, south west Ethiopia. Five grass thatched traditional huts were selected for the field trial. A Latin square design was employed to minimize the bias due to the variation in mosquito catching skills and different sampling nights. Anopheles mosquito larvae and pupae were collected from natural breeding habitats in the village and reared into adults for the tent experiment. Twenty adult An. gambiae complex were released into each tent to evaluate the effect of smoking the plants on knockdown and their feeding activities. An. gambiae s.l., An. demeilloni, An. funestus-group, An. pretoriensis and An. pharoensis were documented in the field collection. J. procera, E. globulus and O. europea significantly reduced indoor density of An. gambiae complex with mean percentage reduction of 80%, 73% and 70%, respectively compared to the control. In the tent trial, smoking plants had significant effect on feeding activity of An. gambiae complex and has induced knockdown effects. The plants significantly inhibited An. gambiae complex attempted to feed on cattle kept inside the tents (F = 383.5, df =3, P < 0.01). Smoking O. europaea (18.9±0.24) induced inhibition of feeding on cattle followed by E. globulus (17.9±37) and J. procera (17.2±0.34), while only 3.9 (±0.42) were unfed in control tents. In conclusion, smoking J. procera E. globulus and O. europea had significant effect on indoor density of host seeking malaria vectors and have inhibited feeding on cattle in the tent trials. Therefore, plant-based mosquito control may play role in reducing mosquito biting at early hours and thereby reduce malaria transmission during the early hours of the night. However, further study is recommended for isolation and identification of bio-active molecules of these test plants and their mode of action to prepare products that could be commercialized and used as potent supplementary control options.

Key words/phrases: Feeding activity, medicinal plants, smoking, indoor density, Kolla Shara


Melkam Abiye Zeru. Host-seeking behavior and hourly biting activity of malaria vectors in Chano mille in Arba Minch area district, Gamo Gofa zone, southwest Ethiopia

The change in early and outdoor biting behavior of malaria vectors in response to indoor based interventions remain a key challenge for malaria control. Hence, understanding the host-seeking behavior and the peak biting time of malaria vectors is important in malaria vector control programs. This study assessed the host-seeking behavior and hourly biting activity of malaria mosquitoes in Chano Mille village in Arba Minch area district, southwest Ethiopia. The first trial was done by keeping cattle inside the tents while the other was by keeping cattle at 1 m far from the tents. The collection of mosquito was done inside the tents in both trials. The collection of mosquito was done by human landing catches in cattle baited tents and tents with human alone. Four human volunteers’ were recruited and trained to collected mosquitoes in the four tents from 18:00-24:00 for three months. Two tents were selected randomly for human alone and two for cattle baited collections in the first night and then rotated to minimize the variation due to location of tents and human collectors. The tent trial was done close to the shore of the Lake Abaya where no other animals are available and hence minimize interference of other animals. The peak biting hour of malaria vectors was also assessed within the village from 18:00-6:00. Anopheles mosquitoes were identified morphologically using a key. The sporozoite infectivity status of Anopheles pharoensis was examined using enzyme-linked immunosorbent assay technique. The data was analyzed using a Generalized Estimating Equations with a negative binomial distribution to see the impact of keeping cattle inside tent and outside the tent in 1 m distance on human to mosquito bites. An. pharoensis, An. gambiae complex and An. tenebrosus were documented. The presence of cattle with human inside the tent increased the number of An. pharoensis by 42% (P < 0.001) compared to human alone. Also, keeping cattle outside in 1 m distance from the tent also increased the number of An. pharoensis inside the tent by 46% (P = 0.002) than human tent with no cattle outside. The presence of cattle with human inside the tent and outside in 1 m distance has no significant effect on the host seeking activities of An. gambiae complex and An. tenebrosus. An. pharoensis and An. gambiae complex showed early night biting activity with peak biting from 19-20:00 which was significant for An. pharoensis (P = 0.015) and An. gambiae complex (P < 0.001). An. gambiae complex was mainly seeking hosts outdoors throughout the night in a village practicing indoor based interventions. Finally, keeping cattle close to human could increase the exposure to bites of malaria vectors particularly to the zoophilic malaria vector An. pharoensis. The outdoor biting behavior of the An. gambiae complex could be a threat for success of current indoor based interventions. Hence, there is a need to develop and implement tools to control the outdoor biting malaria vectors. Moreover, the deployment of cattle far from human residence was recommended to reduce the human exposure to malaria vectors.

Keyword: Cattle baited collection, host-seeking behavior, hourly biting rhythm, malaria vector


Endashaw Esayas. 2017. A small scale variation in human exposure to malaria infection in Kolla Shara Village, southwestern Ethiopia: an implication for targeted malaria control. 

Abstract

Background: Due to the decline of malaria in many countries, there is an interestto eliminate malaria. Hence, it is important to understand the transmission pattern of malaria to deal with the malaria foci which could be the source of infection for the other community members. This study was aimed to investigate the transmission patterns of malaria to identify the clusters with higher risk of malaria infection towards the targeted malaria control interventions in Kolla Shara village, southwestern Ethiopia.

Methods: Both parasitological and entomological studies were carried out from July to December, 2016 inthe five clusters of the village. A total of 591 (in 90 households) study participants were followed biweekly by house to house visit (active malaria case surveillance) for febrile cases. Blood films were collected fromfebrile cases for parasite detection using rapid diagnostic test and later confirmed by microscope. Anopheles mosquito collectionwas done biweeklyin 25 randomly selected houses (five houses in each cluster).The Plasmodium circum-sporozoite proteins (CSPs) rate of An. arabiensis and An. pharoensis were tested by using EnzymeLinked Immuno-Sorbent Assay (ELISA) technique.

Results: A total of 131 febrile cases were screened for malariaduring the six months of follow-up period. Of these, 46 (35.1%) were microscopically confirmed malaria episodes. Plasmodium falciparum accounted for 58.7% (27/46) and 41.3% (19/46) was P. vivax malaria. The incidence of P. falciparum malaria varied significantly among the five study clusters. There were 27 microscopically confirmed P. falciparum cases, yielding an overall incidence of 0.10 episodes per person-year. Of the 27 P. falciparum malaria episodes, 16 (59.3%) were in Abullo, 10 (37.0%) in Erze and only 1 (3.7%) episode was from Enmba cluster. Moreover, only 30% (27/90) households (in Abullo and Erze clusters) experienced 80.4% (37/46) of the total malaria episodes. P. falciparum was the predominant malaria parasite in Abullo (72.7%; 16/22) and in Erze clusters (66.7%; 10/15), whereas more P. vivax (83.3%; 5/6) was observed in Enmba cluster. Although malaria episodes occurred in all age groups, the incidence was higher in children age 5-14 years with IRR: 4.1 (95% CI: 0.7-9.1); p = 0.003. Seven species of Anopheles mosquitoes were documented, of which Anopheles arabiensis was the dominant species (70.5%), followed by An. pharoensis (10%). The highest number of Anopheles was collected from Abullo (47%; 511/1086) and Erze (32%; 348/1086) clusters. Of 733 Anopheles mosquitoes tested for CSPs, eight An. arabiensis were positive for P. falciparum CSP with the overall sporozoite rate of 1.1% (8/733). The overall estimated EIR of An. arabiensis was 5.7 infectious bites/person/6 months. Abullo cluster had SR of 1.7% (5/299) and EIR of 17.0ib/p/6 months, and in Erze cluster, the SR was 1.4% (3/220) and its EIR was 10.6ib/p/6 months.

Conclusion: Malaria transmission is heterogeneous and varied between the five clusters in a small village. Higher malaria incidence, sporozoite rate and EIR were observed in Abullo and Erze clusters. Hence, the malaria control programme could target those populations living in high malaria risk clusters. Moreover, intensifying the existing control interventions in these two malaria foci may make the greatest use of resources for effective malaria control.

Keywords: Anopheles arabiensis, Entomological inoculation rate, Heterogeneity of malaria, Kolla Shara village, Malaria incidence


Temesgen Ashine. 2017. The effect of house screening intervention on indoor malaria transmission, and its durability and community acceptance in Arba Minch Town, southwestern Ethiopia: a randomized trial

Abstract 

Background: Malaria is one of the public health problems worldwide that resulted in millions of illness and hundreds of thousands of deaths in the year 2015. About 60% of total populations are at risk for malaria in Ethiopia. However, there is a reduction in the burden of malaria globally due to extensive application of bed nets, indoor residual spraying, effective drugs and diagnostic tools. To sustain the gain and accelerate the current reduction, there is a need for locally adapted effective, sustainable and community accepted supplementary intervention. Hence, this study was assessed the effect of house screening intervention on indoor malaria transmission, and its durability, and community acceptance in Arba Minch town, southwestern Ethiopia.

Methods: A two-armed, household based, randomized control trial with ancillary qualitative phenomenological study was conducted in Arba Minch town, southwestern Ethiopia. The town is located at elevation of 1218 meters with two rain seasons: September-November and April-June. Kulifo River cross Dilfana and Kulifo Kebeles and considered as the main malaria vector breeding site. Both epidemiological and entomological data was used to evaluate the impact of screening doors and windows on malaria incidence and indoor density of vectors. The frequency of damage to different structure of screening was measured in two rounds with pre-prepared checklist. In-depth interviews with semi-structured questions were conducted with purposely selected household heads from intervention group. STATA version 13, SPSS version 20 and OpenCode version 3.6.2.0 were used for analysis.

Results: A total of 477 participants, 50.1% (n = 239) inhabitants of screened houses and 49.9% (n = 238) inhabitants of unscreened houses, were followed for six months. Of 45 microscopically confirmed clinical malaria cases, 80% (n = 36) were Plasmodium falciparum and the rest 20 % (n = 9) were P. vivax. The incidence of P. falciparum malaria was low [Incidence Rate Ratio (IRR) 0.39, 95% Confidence Interval (CI): 0.19-0.80, p = 0.01] among inhabitants of houses with screened doors and windows compared to those living in unscreened homes. The Protective Efficacy (PE) of screening doors and windows from P. falciparum was 61% (95% CI: 18-83, p = 0.007). The indoor density of mosquitoes was 0.79 (95% Walad CI: 0.49, 1.25, p = 0.02) per CDC light trap per night in screened houses, while it was 0 .35 (95% Walad CI: 0.22, 0.57) in unscreened houses. The screened houses had 56% fewer anopheline compared to control houses. Among screened houses 97.9 % of screened windows and 63.8 % of screened doors were intact after eleven months of installation. Almost all participants of in-depth interviews were willing to continue using the screening of doors and windows.

Conclusions: Screening of doors and windows are effective, durable and well-accepted intervention to control indoor malaria transmission. The existing malaria control interventions can be supplemented with screening doors and windows with wire-mesh for further reduction and ultimately to eliminate malaria.

Key Words: House screening, malaria incidence, mosquitoes indoor density

 


Tigist Ashagrie Alebachew. 2017. Prevalence of cattle ticks and acaricide efficacy test in Arba Minch areas in southwest Ethiopia

Abstract

Ticks are responsible for blood loss, tick worry, damage to hides, skins and the injection of toxins and transmit a number of pathogenic organisms of animals than any other arthropod vector group. The relevant information on tick species composition and prevalence, and acaricide efficacy are essential to assess tick infestation and to identify the appropriate measure of tick control. Hence, the objective of this study was to assess the prevalence of cattle tick, species composition and evaluate the efficacy of diazinon and amitraz against cattle ticks in Arba Minch areas, southwest Ethiopia. A cross-sectional study was conducted to assess the prevalence and species composition of cattle ticks in Chano village from May to June 2016, whereas the field acaricide efficacy trial was conducted in Shelle Millae village in September 2016. We randomly sampled 404 cattle above one-year-old from Chano village, and then ticks were collected and identified into species. A randomized trial was conducted to evaluate the efficacy of diazinon and amitraz acaricides. The sampled cattle were healthy, with higher tick infestations and no previous history of ecto-parasites treatment. The susceptibility status of ticks to diazinon and amitraz was tested in the laboratory. A total of 120 cattle were included for the trial and the baseline tick count was done to randomize into control and intervention groups. Thirty cattle were sprayed by diazinon and thirty by amitraz and remaining sixty were used as control (30 for each acaricide). Tick count was done at day-1, day-2, day-3, day-7, day-14 and day-21 (after trial initiation day). Of the 404 cattle examined, 343 were infested at least by one tick and hence, the prevalence was 84.9%. We identified four genera and nine species of ticks: Amblyomma variegatum, A. cohaerens, A. lepidum, Hyalomma marginatum rufipes, Boophilus decoloratus, Rhipicephalus pravus, R. praetexatus, R. pulchelus and R. evertsi-evertsi. A. variegatum was the most prevalent species (71.4%; 245/343), followed by Amblyomma cohaerens (6.7%; 23/343). Amitraz and diazinon resulted significant reduction in mean tick count in the field compared to the control.  The reduction in tick number due the amitraz was significant up to day-21 post treatment, while it was up to 14-day for diazinon. The acaricidal efficacy of amitraz was superior over diazinon as it showed the maximum percentage reduction and had long residual efficacy. Ticks were susceptible to amitraz and diazinon and hence use of the two acaricides is still promising, but may require repeated application.

Key words:  Acaricide, Amitraz, Cattle ticks, Diazinon, Tick infestation


Zerihun Desalegn. 2017. Impact of wall surface types and spray application quality on efficacy of propoxur against malaria vectors in Shellie Mella, southwest Ethiopia: a randomized trial

Abstract

Background: The residual lifespan of indoor residual spray (IRS) insecticide is a key importance for effectiveness of malaria vector control. Residual efficacy of IRS varied with different spray quality and wall surfaces types. This study assessed the impact of different spray quality and wall surface types on efficacy of propoxur against malaria vectors in Shellie Mella village in Arba Minch area, southwest Ethiopia.

Methods: A randomized experimental trial was conducted in Shellie Mella, southwest Ethiopia from August – December/2016. There were two groups: one with routine spray by district health office as usual and other with standard spray by following WHO guideline. Thirty houses with three different wall types (ten smooth, ten rough and ten painted mud wall) were selected and randomly allocated into routine and standard spray. Three control houses (painted, smooth and rough) were selected from unsprayed nearby urban area for correction of mortality. Wild population of Anopheles gambiae complex was used for wall bioassay tests. Data were analyzed by SPSS version 20 by using two way mixed model Analysis of Variance. The mean variation between wall and spray type were compared by post-hoc analysis.

Result: The knockdown and mortality rate were varied significantly on different wall and spray types.On standard spray, knockdown rate was 95.3% on painted, 82% on smooth and 72.5% on rough surface. On routine spray, it was 82.7% on painted, 48.7% on smooth and 60% on rough surface at week 17. On standard spray, mortality rate of wild Anopheles gambiae complex was 99.3% on painted surface; it was 90% on smooth and 80% on rough surface. On routine spray, it was 89.3% on painted, 61.3% on smooth and 65% on rough surface at week 17 post-spray. The painted wall type showed highest knockdown and mortality rate during 17 weeks post spraying irrespective of spray types. The lower mortality rate and residual effect was seen on routine smooth and rough wall types. The residual efficacy of propoxur (mortality rate > 80%) was more than 17 weeks on standard spray regardless of wall types and it was less than 17 weeks on routine spray except painted wall surface.

Conclusion: The types of wall surface sprayed and spray quality affects the residual efficacy of propoxur. The painted wall surface and standard spray showed better residual efficacy. Therefore, it is recommended to consider wall surface available in the community to estimate the residual lifespan of the insecticide, and to strictly follow spray guideline for correct and consistent spraying.

Key terms: Carbamate insecticide, mortality rate, routine spray, Shelle Mella, standard spray, wall type