Abstracts of Master’s thesis


Abena Kochora: Blood meal sources, human biting rhythms, and infectivity of sand-fly in Ochollo village, a cutaneous leishmaniasis hotspot in southwest Ethiopia

Ochollo village is a cutaneous leishmaniasis hotspot area in the southwest Ethiopia. This study is aimed to determine the blood meal sources human biting rhythm and infectivity of sandflies in Ochollo village. Three entomological techniques such as human landing catch (HLC), centers for disease control and prevention (CDC) light traps and stick traps (STs) were employed to collect sandflies. The village was clustered into nine sub-villages and eight houses were randomly selected from each village for CDC light trap and ST collections. Ten caves were identified and included to collect sandflies using CDC light traps and STs. HLC was done in another four houses (two close to caves, two far from caves). The blood meal origins of Phlebotomus sandflies were determined using polymerase chain reaction (PCR) and the positive specimens were sequenced to determine the host species. Freshly fed sandflies were screened for Leishmania parasite infection by kDNA rt-PCR. A total of 11488 sandflies were collected by CDC light traps and STs (4108; 36% were Phlebotomus, and 7380; 64% were Sergentomyia). Among the indoor collected sandflies, Phlebotomus accounted 33% (1413 of the 4283), while Sergentomyia accounted for 67%. Phlebotomus pedifer (89.5%; 619 of the 692) and P. gibiensis (10.5%; 73 of 692) were the two Phlebotomus species collected both indoors and outdoors. Among the 414 blood fed samples processed for blood meal origin identification, 311 (75%) samples were amplified for the Cytochrome b gene. Among the positive specimens, 73% (227 of 311) were taken blood meal from 19 different sources such as human, goat, cattle, Lizard, rock Hyrax, bush Hyrax, Fox, grass Rat, Acomys ngurui(spiny Mouse), Acomys wilsoni(spiny Mouse), Acomys persivali(spiny Mouse), Acomys spinosissimus(spiny Mouse), Grammomys millani(Mouse), Mus musculus(house Mouse), bat, chicken, buck, cat and dogs, while the blood meal origin of 84 (27% of 311) specimens could not be identified. The majority (60%; 136 of the 227) of the sandflies were feed on humans.About 4.4% (6 of 136) sandflies fed on human blood source (2 collected inside caves and 4 collected indoors), and 14% (1 of 7) sandflies fed on Acomys ngurui(spiny mouse) blood source (collected outdoors) were positive for Leishmania kDNA. Phlebotomus pediferwas the pre dominant (150; 93%) species collected by HLC catches with majority from indoors. The peak biting hours were 20:00-21:00h indoor and 23:00-24:00h outdoor. The current investigation calls for a study to assess the role of both wild and domestic animals in disease transmission. The indoor based intervention could be recommended to reduce the human-sand-fly contact and thereby disease transmission.

Key Words: Biting rhythm, Blood meal sources, LeishmaniakDNA, Ochollo village, sandflies species


Wondemeneh Mekuriaw. 2018. Effect of treatment of humans with ivermectin on mortality, fertility and fecundity of Anopheles arabiensis.

Malaria control programs relay mainly on vector control using insecticides; however, insecticide resistance is widely spreading in vector populations which might affect control programs. The existing core interventions could be supplemented by treating cattle and humans with ivermectin to induce mortality, reduce fecundity and fertility of malaria vectors. Hence, the aim of this study was to assess the effect of administering a single oral dose of ivermectin to humans on survival, fecundity and fertility of Anopheles arabiensis. Six male volunteers were recruited from the local community. Four received recommended single oral dose of 12 mg ivermectin and the remaining two volunteers were used as control. After 24 hours of ivermectin ingestion, 100 starved and 3-5 days old insectary reared An. arabiensis were allowed to feed on treated and control groups in separate cages. Fully un-engorged mosquitoes were removed from each cage using aspirator. Fed mosquitoes were provided with 10% glucose solution and followed for mortality, fecundity and fertility in each group. Following the same procedure the experiment was repeated on the same individuals after 4, 7, 10 and 13 days post-ivermectin treatment. Mortality of An. arabiensis  fed on day one post ingestion of ivermectin was significantly higher  compared to day 7, 10, and  13 (P < 0.001), but there was no significant variation between day 1 and day 4 (P = 0.73,). The mean mortality of mosquitoes fed on treatment group at day 4 was significantly higher compared day 7, day 10, day 13 and control (P-value < 0.01). But, the variation was not significant between day 10, day 13, and control group. The mean survival day of mosquitoes fed on day 1 post-treatment was 2.1, while those fed on day 4 survived 4.0 days. Moreover, those mosquitoes fed on treatment group at day 7 had produced significantly lower number of eggs than those fed on day 10 (P < 0.001), day 13 (P < 0.001) and control (P < 0.001).  However, the difference was no significant between day 10, day 13 and control. Ivermctin had significant effect on fertility of mosquito on day 7 post-ivermectin treatment. Therefore, a single oral dose of ivermectin induced mortality and reduced fecundity, and fertility of An. arabiensis. But,it is recommended to conduct study on the effect of ivermectin on insecticide resistant mosquito population before public use for malaria control.

Key words: Anopheles arabiensis, Fecundity, Fertility, Ivermectin, Mortality.

Ephrem Damene. 2018. Effect of administering ivermectin to domestic animals on mortality, fecundity and survivorship of Anopheles arabiensis

Global trends in malaria incidence and mortalityhas declined in many malaria endemic countries due to the massive scale-up of indoor based malaria control interventions. However, the impact of these interventions has been restricted due to insecticide resistance, the animal and outdoor biting behaviors of malaria vectors. Hence, approaches to target insecticide resistant and zoophilic vectors are urgent. This study was designed to evaluate the effect of treating cattle ivermectin on mortality, fecundity and survivorship of laboratory reared Anopheles arabiensis. Three calves were randomly selected to receive a subcutaneous injection of ivermectin at the therapeutic dose of 0.2 mg/kg of body weight, while the other two calves received no treatment and used as control. Five tents were constructed for the trial. The calves were introduced into the tents (one per tent) and then, 30 starved An. arabiensiswere released into each tent. Only fully engorged females were collected from each tent. Later, their mortality, survivorship and fecundity were recorded. Data analysis was done using SPSS version 16. Over all, ivermectinhad significant effect on the mortality, survivorship and fecundity of An. arabiensis. The mean mortality rate of An. arabiensis was 81.6% at day one after treatment. The survivorship of An. arabiensiswas significantly reduced after feeding on ivermectin treated compared to those fed on control calves (F = 110.7, DF = 1, P< 0.001). The effect was significantly affected by the interaction of treatment and day after injection (F = 15.13, DF = 4, P< 0.001). Those mosquitoes fed on calves treated with ivermectin produced significantlylower number of eggs compared to control groups (F = 435.3, DF = 4, P< 0.001). In conclusion, ivermectin had impact on mortality, fecundity and survivorship of laboratory reared An. arabiensis. However, further study could be recommended on the impactof treatment of cattle with ivermectin on wild vector population, and combining the use of existing indoor based interventions with mass ivermectin administration for domestic animals.

Key words: Anopheles arabiensis, Ivermectin, Fecundity, Survivorship

Tirhas Mulubirhan. 2018.  Sandflies composition and habitat preference in Ochollo village, a cutaneous Leishmaniasis hotspot in southwest Ethiopia.

Cutaneous Leishmaniasis (CL) is a neglected tropical disease, caused by Leishmania aethiopica, endemic in highlands of Ethiopia. Investigating sandflies composition and ecology is a pre-requisite for effective control of the vectors and the disease they transmitting. Thus, the present study aimed to assess the species composition and ecology of sandflies in Ochollo village, a CL hotspot in southwest Ethiopia. Sandflies were collected inside houses, in caves, in rocky and peri-domestic habitats using Center for Disease Control and Prevention (CDC) light traps and sticky traps (STs) from August 2016-February 2017. Collection of sandflies was also done in thirty houses (three types of houses: grass thatched roofs, corrugated iron roof and houses with grass thatched roofs and walls) using both entomological techniques. All collected sandflies were morphologically identified into species using morphological keys. A total of 2,378 sandflies, three Phlebotomus(P. pedifer, P. ashfordiand P. arabicus) and four Sergentomyia(S. bedfordi group, S. affinis, S. africana and S. antennatus), were collected. Phlebotomus pedifer(69.76%) and S. bedfordi(21.48 %) were the most common species. Caves were the sites where most sandflies were collected by CDC traps (84.1 %) and STs (37.1 %). By ST, predominant collection was made inside caves (37.1 %), rocky fences (26. 8 %) and peri-domestic habitats (26.6 %), while small proportion was collected inside houses (9.5 %). Among the peri-domestic habitats, more sandflies were sampled externally in house cracks (41%; n = 46), followed by animal manures (24%; n = 27). One Phlebotomus(P. pedifer) and three Sergentomyia(S. bedfordi group, S. africana andS. affinis) species were collected inside houses by CDC light traps and STs. Phlebotomus pediferwas found to be the common species inside houses. Based on the house type, majority of sandflies were caught in houses with cracks on the walls. In conclusion, P. pediferwas the only Phlebotomusspecies collected indoors, which might imply the role the species in CL transmission. This study also suggested that caves were the preferred habitat for resting which might be important for future implementation of vector control measures. Moreover, determining the blood meal sources in relation to the habitats and human biting behavior of the species could be recommended to design effective intervention.

Keyword: Phlebotomus species,Sergentomyiaspecies, cutaneous Leishmaniasis, Ochollo village


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. 


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


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 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


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


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