Entomological evaluation of vector control


Kena, O. 2017. Entomological impact of combined and separate use of indoor residual spraying and long-lasting insecticidal nets for malaria prevention in Adami Tullu district, South-Central Ethiopia. PhD thesis. Addis Ababa University.

Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) are the key frontline malaria prevention interventions in Ethiopia. Both target Anopheles arabiensis, the sole primary malaria vector. Universal coverage of both interventions has been promoted and there is a growing demand in combination of interventions for malaria control and elimination. However, available evidence is contradictory wether the combined intervention is better than either IRS or LLINs alone. To investigate whether IRS and LLINs combination provides added protective impact on An. arabiensis compared to either IRS or LLINs alone, a cluster randomized controlled trial was carried out in Adami Tullu district, south-central Ethiopia. Villages were randomly allocated to four study arms: IRS+LLINs, IRS, LLINs, and control. All households in the IRS+LLINs and LLINs arms were provided with LLINs (PermaNet 2.0) free of charge. Households in the IRS+LLINs and IRS arms were applied with propoxur before the main malaria transmission season in 2014 and 2015. Adult mosquitoes were collected in randomly selected villages in each arm using CDC light trap catch (LTC) set close to a sleeping person, pyrethrum spray catch (PSC), and artificial pit shelter (PIT), for measuring host-seeking density (HSD), indoor resting density (IRD), and outdoor resting density (ORD) of the anophelines. Human landing catch (HLC) was performed in selected villages to monitor the impact of the interventions on local mosquito biting behaviours (biting location, time and host preference).

Collected anophelines were identified to species by use of standard morphological keys and additional use of molecular methods to separate sibling species of the An. gambiae complex. Enzyme-linked immunosorbent assay (ELISA) was used to detect malaria infections in mosquitoes and the sources of mosquito blood meals. Mean densities were compared using incidence rate ratio (IRR) calculated by negative binomial regression. Parity rate (percentage of parous females) was also determined by ovarial dissection. Human blood index (HBI) was expressed as the proportion of mosquitoes with human blood divided by the total number of blood-fed mosquitoes tested.

A total of 1786 female anophelines of four species (An. arabiensis, An. pharoensis, An. ziemanni and An. funestus s.l.) were collected over two transmission seasons during the intervention period (2014-2015). Anopheles numbers were highest in the control arm (41.3% of total) followed by LLINs (25.4%), IRS (18.0%), and IRS+LLINs (15.8%). In most of the vector parameters estimated, the impact of IRS and LLINs combined and separate interventions were significantly higher in communities that recieved the interventions (in experimental groups) compared with untreated communities (control group). The mean HSD of An. arabiensis in the IRS+LLINs arm was similar to the IRS arm (0.03 vs. 0.03/ house/LTC/night) but lower than the LLINs arm (0.03 vs. 0.10/house/LTC/night, p=0.07) and so was the difference in IRD and ORD between the IRS+LLINs compared to the IRS arm. However, both IRD and ORD of An. arabiensis were higher in LLINs compared to IRS+LLINs (p < 0.001 for indoors). Parity rate of An. arabiensis were similar among the intervention arms. None of the 1786 samples of four species tested by ELISA was positive for P.  falciparum and P. vivax CSP infection in all of the study arms. Anopheles arabiensis preferred mainly bovine and human hosts for blood meal sources with high HBI in the LLIN alone. Indoor resting habit of An. arabiensis was less impacted by LLINs alone intervention compared to IRS + LLINs or IRS alone.

In conclusion, the IRS+LLINs and the IRS alone each was similarly most effective against An. arabiensis as compared to the LLINs alone. The IRS+LLINs provided added impact on An. arabiensis compared to LLINs alone. The LLINs alone had poor impact on densities and human biting rates of An. arabiensis in this study setting.

You can download the thesis here: Oljira-Kenea-thesis

Smallpox and eliminating other diseases

 Dr. Donald A. Henderson, who led the World Health Organization’s war on smallpox, administering a smallpox vaccination in Ethiopia, around 1972. The last known case was in 1977. (Photo WHO)



Dr. Donald A. Henderson was an American physician who coordinated the World Health Organisation’s efforts to eradicate smallpox. After smallpox had been declared eradicated in 1980, he returned to the US, and became the Dean of what is now the Johns Hopkins Bloomberg School of Public Health. Dr. Donald A. Henderson died this month and will be remembered as a great scientist and public health physician.

As a child in late 1950s I remember a smallpox epidemic in Dilla in Ethiopia. I was so fortunate to have met this remarkable man, and listen to a talk he had at WHO in Geneva. Because of the success in eradicating smallpox, many believe that it also should be possible to eliminate other diseases such as poliomyelitis, Guinea worm, measles, or even malaria. I find it interesting to read that Dr Henderson was rather skeptical about these new eradication initiatives. Both the characteristics of the diseases, as well as the efforts put into getting rid of the diseases differed from what was the strategy to eradicate smallpox.

Yalio Yaya defends his PhD thesis

Yaliso-front-pageThe overall objective of the PhD thesis is to measure and compare maternal and neonatal mortality and obstetric services through community- and facility-based methods in southern Ethiopia. Yaliso Yaya used four different methods to measure maternal mortality:

  1. A prospective community-based birth registry managed by health extension workers in 75 rural villages in three districts in south Ethiopia (population 421 639)
  2. A household survey conducted in 6 572 households in 15 randomly selected rural villages in the district of Bonke, with questions about pregnancy and birth outcomes in the last five years
  3. A household survey among 8 503 adult siblings using the sisterhood method
  4. A facility-based review of records in all 63 health centres and three hospitals in Gamo Gofa zone.

Neonatal mortality was measured with the second method, and emergency obstetric services were assessed through the facility-based review.

The thesis is based on a thorough and systematic registration of adverse events during several years, using multiple methods. This allows validation of estimates, and it presents detailed and precise information about maternal mortality rates from rural south Ethiopia.

A special focus of the work is on the finding that community based health workers (Health Extension Workers) can be used to generate maternal mortality data, thus alleviating the chronic problem of unavailability of valid and timely mortality data.

The PhD thesis can be downloaded here.

Assessing food shortage

Gebreyesus S, Lunde T, Mariam D, Woldehanna T, Lindtjorn B. Is the adapted Household Food Insecurity Access Scale (HFIAS) developed internationally to measure food insecurity valid in urban and rural households of Ethiopia? BMC Nutrition 2015; 1(1): 2.

The concept of food insecurity encompasses three dimensions. One of these dimensions, the access component of household food insecurity is measured through the use of the Household Food Insecurity Access Scale (HFIAS). Despite its application in Ethiopia and other similar developing countries, its performance is still poorly explored. Our study aims to evaluate the validity of the HFIAS in Ethiopia.

We conducted repeated cross-sectional studies in urban and rural villages of the Butajera District in southern Ethiopia. The validation was conducted on a pooled sample of 1,516 households, which were selected using a simple random sampling method. The HFIAS was translated into the local Amharic language and tested for face validity. We also evaluated the tool’s internal consistency using Cronbach’s alpha and factor analysis. We tested for parallelism on HFIAS item response curves across wealth status and further evaluated the presence of a dose-response relationship between the food insecurity level and the consumption of food items, as well as between household wealth status and food insecurity. Additionally, we evaluated the reproducibility of the tool through the first and second round of HFIAS scores.

The HFIAS exhibited a good internal consistency (Cronbach’s alpha for the values of rounds 1 and 2 were 0.76 and 0.73, respectively). A factor analysis (varimax rotation) resulted in two main factors: the first factor described a level of mild to moderate food insecurity, while the second factor described severe food insecurity. HFIAS item response curves were parallel across wealth status in the sample households, with a dose-response trend between food insecurity levels and the likelihood of previous day food consumption being observed. The overall HFIAS score did not change over the two rounds of data collection.

The HFIAS is a simple and valid tool to measure the access component of household food insecurity. However, we recommend the adaptation of questions and wordings and adding examples before application, as we found a discrepancy in understanding of some of the nine HFIAS questions.

Finding patients with tuberculosis

Woldesemayat EM, Datiko DG, Lindtjørn B. Follow-Up of Chronic Coughers Improves Tuberculosis Case Finding: Results from a Community-Based Cohort Study in Southern Ethiopia. PLoS ONE 2015; 10(2): e0116324.


Untreated smear-positive tuberculosis (TB) patients are the primary source of infection; however, a large number of TB cases have not been identified and are untreated in many sub-Saharan African countries, including Ethiopia. This study determined whether or not a community-based follow-up of chronic coughers improves detection of TB cases and the risk factors for death among such cases.

We conducted a census in six rural communities in Sidama, southern Ethiopia. Based on interview and sputum investigation, we identified 724 TB smear-negative chronic coughers, and did a cohort study of these chronic coughers and 1448 neighbourhood controls. For both chronic coughers and neighbourhood controls, we conducted a TB screening interview and performed sputum microscopy, as required, at 4, 7 and 10 months. Between September 2011 and June 2012, we followed chronic coughers and neighbourhood controls for 588 and 1,204 person-years of observation, respectively.

Of the chronic coughers, 23 developed smear-positive TB (incidence rate = 3912/105 person-years) compared to three neighbourhood controls who developed smear-positive TB (incidence rate = 249/105 person-years). The male-to-female ratio of smear-positive TB was 1:1. We demonstrated that chronic coughers (adjusted hazards ratio [aHR], 13.5; 95% CI, 4.0–45.7) and the poor (aHR, 2.6; 95% CI, 1.1–5.8) were at high-risk for smear-positive TB. Among the study cohort, 15 chronic coughers and two neighbourhood controls died (aHR, 14.0; 95% CI, 3.2–62.4).

A community-based follow-up of chronic coughers is helpful in improving smear-positive TB case detection, it benefits socioeconomically disadvantaged people in particular; in rural settings, chronic coughers had a higher risk of death.

Tuberculosis in South Ethiopia

Mesay-Paper 1Dangisso MH, Datiko DG, Lindtjørn B (2014) Trends of Tuberculosis Case Notification and Treatment Outcomes in the Sidama Zone, Southern Ethiopia: Ten-Year Retrospective Trend Analysis in Urban-Rural Settings. PLoS ONE 9(12): e114225. doi:10.1371/journal.pone.0114225

Background: Ethiopia is one of the high tuberculosis (TB) burden countries. An analysis of trends and differentials in case notifications and treatment outcomes of TB may help improve our understanding of the performance of TB control services. Methods: A retrospective trend analysis of TB cases was conducted in the Sidama Zone in southern Ethiopia. We registered all TB cases diagnosed and treated during 2003–2012 from all health facilities in the Sidama Zone, and analysed trends of TB case notification rates and treatment outcomes.

Results: The smear positive (PTB+) case notification rate (CNR) increased from 55 (95% CI 52.5–58.4) to 111 (95% CI 107.4–114.4) per 105 people. The CNRs of PTB+ in people older than 45 years increased by fourfold, while the mortality of cases during treatment declined from 11% to 3% for smear negative (PTB-) (X2 , trend P,0.001) and from 5% to 2% for PTB+ (X2trend, P,0.001). The treatment success was higher in rural areas (AOR 1.11; CI 95%: 1.03–1.2), less for PTB- (AOR 0.86; CI 95%: 0.80–0.92) and higher for extra-pulmonary TB (AOR 1.10; CI 95%: 1.02– 1.19) compared to PTB+. A higher lost-to-follow up was observed in men (AOR 1.15; CI 95%: 1.06–1.24) and among PTB- cases (AOR 1.14; CI 95%: 1.03–1.25). More deaths occurred in PTB-cases (AOR 1.65; 95% CI: 1.44–1.90) and among cases older than 65 years (AOR 3.86; CI 95%: 2.94–5.10). Lastly, retreatment cases had a higher mortality than new cases (6% vs 3%).

Conclusion: Over the past decade TB CNRs and treatment outcomes improved, whereas the disparities of disease burden by gender and place of residence reduced and mortality declined. Strategies should be devised to address higher risk groups for poor treatment outcomes.

Tuberculosis in the Arsi Zone in Ethiopia

Shallo D. Hamusse, Meaza Demissie, Dejene Teshome, Bernt Lindtjørn. Fifteen-year trend in treatment outcomes among patients with pulmonary smear-positive tuberculosis and its determinants in Arsi Zone, Central Ethiopia.  Glob Health Action 2014, 7: 25382

Background: Directly Observed Treatment Short course (DOTS) strategy is aimed at diagnosing 70% of infectious tuberculosis (TB) and curing 85% of it. Arsi Zone of Ethiopia piloted DOTS strategy in 1992. Since then, the trend in treatment outcomes in general and at district-level in particular has not been assessed. The aim of this study was to analyse the trend in TB treatment outcomes and audit district-level treatment outcomes in the 25 districts of Arsi Zone.

Design: A retrospective cohort study design was employed to audit pulmonary smear-positive (PTB +) patients registered between 1997 and 2011. Demographic and related data were collected from the TB unit registers between January and March 2013. The 15-year trend in treatment outcomes among PTB+ patients and district-level treatment outcomes was computed.

Results: From 14,221 evaluated PTB+ cases, 11,888 (83.6%) were successfully treated. The treatment success rate (TSR) varied from 69.3 to 92.5%, defaulter rate from 2.5 to 21.6%, death rate from 1.6 to 11.1%, and failure rate from 0 to 3.6% across the 25 districts of the zone. The trend in TSR increased from 61 to 91% with the increase of population DOTS coverage from 18 to 70%. There was a declining trend in defaulter rate from 29.9 to 2.1% and death rate from 8.8 to 5.4% over 15 years. Patients aged 25–49 years (Adjusted Odd Ratio (AOR), 0.23; 95% CI: 0.21–0.26) and ≥50 years (AOR, 0.43; 95% CI: 0.32–0.59), re-treatment cases (AOR, 0.61; 0.41, 0.67), and TB/HIV co-infection cases (AOR, 0.45; 95% CI: 0.31–0.53) were associated with unsuccessful treatment outcomes.

Conclusions: DOTS expansion and improving population DOTS coverage in Arsi has led to a significant increase in treatment success and decrease in death and defaulter rates. However, there is a major variation in treatment outcomes across the 25 districts of the zone, so district-specific intervention strategy needs to be considered. The low TSR among re-treatment cases might be due to the high rate of MDR-TB among this group, and the issue needs to be further investigated to identify the extent of the problem.


Biomass fuel in households and risk of tuberculosis

Woldesemayat EM, Datiko DG, Lindtjorn B. Use of biomass fuel in households is not a risk factor for pulmonary tuberculosis in South Ethiopia. The international journal of tuberculosis and lung disease.  2014;18(1):67-72.

SETTING: Rural settings of Sidama Zone in southern Ethiopia.

OBJECTIVE: To investigate the association between exposure to biomass fuel smoke and tuberculosis (TB).

DESIGN: A matched case control study in which cases were adult smear-positive pulmonary tuberculosis (PTB) patients on DOTS-based treatment at rural health insti- tutions. Age-matched controls were recruited from the community.

R E S U LT S : Of 355 cases, 350 (98.6%) use biomass fuel for cooking, compared to 801/804 (99.6%) controls. PTB was not associated with exposure to the biomass fuel smoke. None of the factors such as heating the house, type of stove, presence of kitchen, presence ofadequate cooking room ventilation, light source and number of rooms in the house was associated with the presence of TB. However, TB determinants such as sex, household contact with TB, history of TB treatment, smoking and presence of a smoker in the household have previously shown an association with TB.

CONCLUSION: We found no evidence of an association between the use of biomass fuel and TB. Low statistical power due to the selection of neighbourhood controls might have contributed to this negative finding. We would advise that future protocols should not use neigh- bourhood controls and that they should include measure- ments of indoor air pollution and of exposure duration.

Eskindir Loha defended his PhD thesis

On Tuesday September 3, 2013, Eskindir Loha defended his PhD thesis.

The title of the work is: “Variation in malaria transmission in southern Ethiopia: The impact of prevention strategies and a need for targeted intervention”.

Summary of Thesis

In Ethiopia, 60 per cent of the population is at risk of malaria. The transmission of the disease is unstable, and hence, the possibility of epidemics demanded continuous vigilance and preparedness of the health system. Meanwhile, the complexity of the transmission of the disease has become an impediment to retain the effectiveness of prevention and control strategies. Understanding factors that play role in disease transmission at different locations, the pattern of disease transmission, the impact of prevention and control strategies and challenges in control efforts were deemed crucial for the way forward.

This thesis analysed the local variations in the link between potential determinants of transmission – meteorological factors and malaria incidence. For this, we used datasets from 35 locations found in the Southern Nations and Nationalities People’s Region and registered within the period 1998 to 2007. The findings implied that the variability in the models to be principally attributed to regional differences, and a single model that fits all locations was not found. Although there is a biological link between meteorological factors and malaria transmission, the link is affected by local conditions and non-meteorological factors.

With the understanding of a need to incorporate non-meteorological factors, in an attempt to predict disease incidence, a detailed investigation was carried out in Chano Mille Kebele – one of the malarious Kebeles of Arba Minch Zuria district, Gamo Gofa zone, south Ethiopia. A prospective cohort study was conducted for two years with a weekly visit to each of 1,388 households. The findings showed that rainfall increased and indoor residual spraying with Deltamethrin reduced falciparum malaria incidence. Higher disease incidence was observed among males, children 5–14 years old, insecticide-treated net non-users, the poor, and people who lived closer to vector breeding site. Meanwhile, we identified spatio-temporal clusters of high disease rates within a 2.4 sq.km area of the Kebele.

Mass distribution of insecticide-treated nets neither showed community-wide benefit nor influenced the spatio-temporal clustering of malaria, though proved to be protective at the individual level. Further analysis on insecticide-treated nets showed that the proportion of insecticide-treated net use reached a maximum of 69 per cent despite a near universal coverage (98.4 per cent) was achieved. Sleeping under the insecticide-treated nets was influenced by gender, age and proximity to the vector breeding site. Factor compromising the usable life of insecticide-treated nets and a lack of convenient space to hang more than one net were reported.

The local variations in meteorology-malaria link, the heterogeneous risk carried by different population segments and the observed effect of prevention strategies may help to revisit the approaches towards malaria – for which I forwarded specific recommendations.

Use of bed nets to prevent malaria

The objective of this study was to characterize the pattern related to ITN use in one village in south Ethiopia. A huge discrepancy was reported between ownership versus utilization of insecticide-treated bed nets (ITNs). To acquire the benefits of ITNs, households need to use and not merely own them.

Eskindir Loha, Kebede Tefera and Bernt Lindtjørn. Freely distributed bed-net use among Chano Mille residents, south Ethiopia: a longitudinal study. Malaria Journal 2013, 12:23 doi:10.1186/1475-2875-12-23

Background:  A huge discrepancy was reported between ownership versus utilization of insecticide-treated bed nets (ITNs). To acquire the benefits of ITNs, households need to use and not merely own them. The objective of this study was to characterize the pattern of, and assess factors related to ITN use in one village in south Ethiopia.

Methods:  A prospective cohort study involving 8,121 residents (in 1,388 households) was carried out from April 2009 to April 2011 (101 weeks). Every week, individuals were asked whether they slept under an ITN the night before the interview. Descriptive statistics was used to report the availability and use of ITN. A negative, binomial, probability, distribution model was fitted to find out significant predictors of ITN use. Reasons for not using ITN were summarized.

Results:  The total number of ITNs available at the beginning of the study was 1,631 (1.68 ITNs per household). On week 48, 3,099 new ITNs (PermaNet2.0) were distributed freely (2.3 ITNs per household). The number of households who received at least one new ITN was 1,309 (98.4%). The percentage of children <5 years and pregnant women not using ITNs exceeded that of other adults. The mean (range; SD) ITN use fraction before and after mass distribution was 0.20 (0.15-0.27; 0.03) and 0.62 (0.47-0.69; 0.04), respectively. Before mass ITN distribution, the most frequent reason for not using ITN was having worn out bed nets (most complained the bed nets were torn by rats); and after mass ITN distribution, it was lack of convenient space to hang more than one ITN. Males, younger age groups (mainly 15–24 years) and those living away from the vector-breeding site were less likely to use ITN.

Conclusions:  The ITN use fraction reached to a maximum of 69% despite near universal coverage (98.4%) was achieved. Gender, age differences and distance from vector breeding site were associated with ITN use. Strategies may need to be designed addressing disproportions in ITN use, lack of convenient space to hang more than one ITN (for those receiving more than one), and measures to prolong usable life of ITNs.