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

PhD in malaria entomology, and first and second opponents from Africa

img_1060On Friday, January 27, Fekadu Massebo  defended his PhD thesis at the University of Bergen. This was a good defence with a thorough  scientific discussion. For the first time at the University of Bergen, the first and second opponents were African. This is a testimony to the emerging strength of African scientists.

The picture shows the candidate after the defence, the  opponents, and the supervisors. From left: Professor Sven Gudmund Hinderaker (Acting Dean), Fekadu Massebo, Dr Silas Majambere (First opponent), Professor Tehmina Mustafa from UiB, Professor Bernt Lindtjørn (supervisor), Dr Tarekegn Abeku (Second opponent) and Ass Professor Meshesha Balkew (supervisor) from Addis Ababa University.

New information about malnutrition in Ethiopia

Seifu-thesis coverNew PhD: On September 16, Seifu Hagos Gebreyesus from Ethiopia, shall defend his PhD work at the University of Bergen:

Spatial variations in child undernutrition in Ethiopia: Implications for intervention strategies


Background: Ethiopia is one of the countries with the highest burden of undernutrition, with rates of stunting and underweight as high as 40% and 25%, respectively. National efforts are underway for an accelerated reduction of undernutrition by the year 2030. However, for this to occur, understanding the spatial variations in the distribution of undernutrition on a varying geographic scale, and its determinants will contribute a quite a bit to enhance planning and implementing nutrition intervention programmes.

Objectives: The aim of this thesis was to evaluate the large- and small-scale spatial variations in the distribution of undernutrition indicators, the underlying processes and the factors responsible for the observed spatial variations.

Methods: We used nationally available climate and undernutrition data to evaluate the macro-scale spatial pattern of undernutrition and its determinants. We applied a panel study design, and evaluated the effect of growing seasonal rainfall and temperature variability on the macro-scale spatial variations (Paper I). We conducted a repeated cross- sectional survey to assess the performance of the Household Food Insecurity Access Scale (HFIAS) developed internationally to measure household food insecurity. The results from this validation work were used to modify the HFIAS items for subsequent papers (Papers III and IV). We conducted a census on six randomly selected kebeles to evaluate the spatial patterns of undernutrition on a smaller scale (Paper III). For Paper IV, we conducted a cross-sectional survey on a representative sample, and employed a Bayesian geo-statistical model to help identify the risk factors for stunting, thereby accounting for the spatial structure (spatial dependency) of the data.

Results: In Paper I, we demonstrated spatial variations in the distribution of stunting across administrative zones in the country, which could be explained in part by rainfall. However, the models poorly explained the variation in stunting within an administrative zone during the study period. We indicated that a single model for all agro-ecologic zones may not be appropriate. In Paper II, we showed that the internal consistency of the HFIAS’ tools, as measured by Cronbach’s alpha, was adequate. We observed a lack of reproducibility in HFIAS score among rural households. Therefore, we modified the HFAIS tool, and used it for subsequent surveys in this thesis (Papers III and IV). In Paper III, spatial clustering on a smaller scale (within a kebele) was found for wasting and severe wasting. Spatial clustering on a higher scale (inter-kebele) was found for stunting and severe stunting. Children found within the identified cluster were 1.5 times more at risk of stunting, and nearly five times more at risk of wasting, than children residing outside this cluster. In Paper IV, we found a significant spatial heterogeneity in the distribution of stunting in the district. Using both the local Anselin Moran’s I (LISA) and the scan statistics, we identified statistically significant clusters of high value (hotspots) and a most likely significant cluster for stunting in the eastern part of the district. We found that the risk of stunting was higher among boys, children whose mother or guardian had no education and children who lived in a food-insecure household. We showed that including a spatial component (spatial structure of the data) into the Bayesian model improved the model fit compared with the model without this spatial component.

Conclusion: We demonstrated that stunting and wasting exhibited a spatial heterogeneity, both on a large and small scale, rather than being distributed randomly. We demonstrated that there is a tendency for undernourished cases (stunting and wasting) to occur near each other than to occur homogeneously. We demonstrated a micro-level spatial variation in risk and vulnerability to undernutrition in a district with a high burden of undernutrition. Identifying such areas where a population at risk lives is central in assisting a geographical targeting of intervention. We recommend further study, possibly using a trial design or implementation research approach, to help evaluate the feasibility and benefits of geographically targeting nutritional interventions.

The thesis can be downloaded here.

Important research on tuberculosis control

Mesay-thesis title

New PhD: On September 5, Mesay Hailu Dangisso from Ethiopia, shall defend his PhD work at the University of Bergen:

Tuberculosis control in Sidama in Ethiopia. Programme performance and spatial epidemiology

The Sustainable Development Goals are to end the TB epidemic by reducing the incidence of TB by 90 % and by reducing mortality by 95% by 2035 from what was in 2015. Globally, access to TB diagnostic and treatment facilities (DOTS) has improved, and millions of TB cases have been notified and treated, which has resulted in many lives being saved. In recent years in Ethiopia, TB control services have been substantially expanded and decentralized, which has improved access to TB care. Assessing trends in TB programme performance (case notification and treatment outcomes), as well as the spatial distribution and variations of the disease, could help in understanding the differentials in accessibility to TB control services, the distribution of disease burden and help in understanding the effectiveness of TB control programmes.

We assessed the distribution of- and accessibility to TB control facilities and trends in TB control programme performance in both urban and rural settings, by age category and by gender, and assessed the case notification rates of childhood TB over 10 years. We also assessed trends of the treatment outcomes of TB cases in order to identify high-risk groups for adverse treatment outcomes. Lastly, we explored spatial distribution and spatio-temporal clustering of the disease over 10 years to identify areas with the highest TB case notifications, and to identify the spatial variations in disease occurrence.

Over 10 years, the accessibility to- and coverage of TB control facilities has improved. Thus, TB control service coverage increased by 36%, and the proportion of locations within 10 km of the nearest TB diagnostic facility also increased. However, we noted variations in physical accessibility between areas in the study area. The mean distance from the nearest smear microscopy unit was 7.6 km in 2003 and declined to 3.2 km in 2012. The substantial expansion of primary health-care services, including TB control facilities and community-based intervention, has contributed to an increase in TB CNRs and treatment outcomes. From this finding, we suggest that a concerted effort be made to improve the accessibility to TB control facilities in areas with low case notification and poor accessibility.

An analysis of the trends of TB case notification and treatment outcomes in different settings based on the correct address, by age category and gender, and place of residence, could help understand the performance of TB control programmes and the epidemiology of TB within a community. We found that the CNRs for all forms of- and smear-positive TB increased steadily between 2003 and 2012. The CNR of smear-positive TB in the 45-year and above age groups rose by nearly fourfold. The disparity between men and women in CNR declined from 16 per 100,000 people in 2003 to eight per 100,000 people in 2012, with the male to female ratio also declining from 1.3:1 to 1.1:1. The increase in CNRs could be attributed to improved access to TB care and community-based interventions.

Over a decade, treatment success increased, whereas mortality and lost-to-follow-up declined. However, more deaths occurred among smear-negative TB cases, in children and among older patients. Targeted interventions are needed to address high-risk groups for adverse treatment outcomes.

The burden of childhood TB is one of the indicators used for assessing the ongoing transmission of the disease within a community. Assessing the case notification and treatment outcome of childhood TB could provide essential evidence to help understand the effectiveness of TB control programmes and the disease burden. Thus, we assessed childhood TB case notification and treatment outcomes over a decade. The mean CNRs for new cases of TB of all forms were 30 per 100,000 children, and no decline was observed in childhood TB cases over a 10-year study period. A community-based active case-finding intervention increased TB case notification in adults and in older children (10-14-year-olds); however, the case notification did not increase among younger children (less than five-years old). This could be explained by inadequate diagnostic facilities for childhood TB despite the community-based intervention, which focuses on symptomatic screening, followed by sputum-smear microscopy and the substantial expansion of TB control services. Better diagnostic facilities and interventions are required to increase case detection, and to improve treatment outcome among younger children.

The burden of TB varies between- and within countries because of differentials in health service performance and the varying distribution of risk factors that increase the transmission of- and susceptibility to the disease. An analysis of the disease burden in coarser geographic or administrative units could hide the burden of the disease at lower administrative units. Therefore, we assessed the distribution of the disease in different geographic settings in the study area, and looked for the pattern of the disease transmission over years, as well as for evidence of spatio- temporal clustering. We found spatial variations in both the disease distribution and spatial and space-time clustering of the disease in the central, northern and northwestern areas of the study area. This could be explained by sustained transmission, disproportionate distribution of risk factors, varying access to TB care and varying TB programme performance, all of which require targeted interventions.

In conclusion, in a population with a high prevalence of tuberculosis, we show that access to tuberculosis diagnostic and treatment facilities, in addition to the performance of TB control programmes, improved from 2003 to 2012. However, we identified areas with poor accessibility to diagnostic and treatment facilities. The low and constant case notification rate in childhood TB is an area of concern, and may indicate an underdiagnosis of childhood tuberculosis. Moreover, the distribution of tuberculosis has changed over time, and in different areas, thereby suggesting a high transmission or variable access to diagnosis and treatment. As a result, the variations in case notification rates, and in accessibility to tuberculosis control services represent challenges on how to improve the organization and performance of TB control.

To download the thesis please clic here.

Grammar and Glamour

Although I do some writing, I often find it difficult to write good papers. English is not my native language, and at school, grammar was not my favourite subject.

But, everyone can benefit from improved writing skills at work, at home, online, you name it.

I often use Strunk and White’s “Elements of Style.” But now another book is my favourite:  “The Glamour of Grammar,” by Roy Peter Clark, which a book review in The New York Times says “is very much a manual for the 21st century”.

I recently read this fascinating book. To be honest, this is the only grammar book I have read from beginning to end, and I will use it to improve my language. I learned that for the good writer, no decision is too small, including whether to use “a” or “the”.

I did not associate the word grammar with glamour. The author explains: “The bridge between the words glamour and grammar is magic. According to the Oxford English Dictionary, glamour evolved from grammar through an ancient association between learning and enchantment. There was a time when grammar described not just language knowledge, but all forms of learning, ..”

The book is not only about grammar: it is about improving writing. Each chapter ends with “keepsakes” (reminders), where the author summarises important points and keeps things informal enough and thus avoids sounding like a textbook.

Be careful when presenting your results

Be careful when presenting your results

Recently, the journal nature had an editorial entitled: “Mind the spin. Scientists – and their institutions – should resist the ever-temptation to hype their results”.

Nature referred to the recently concluded HIV vaccine trial in Thailand. Before publishing the results, the researchers said in a preliminary announcement in September, the trial that a vaccine combination reduced the risk of HIV infection by nearly one-third. Some even said “It’s the largest step forward that’s ever occurred in the HIV-vaccine field.”

Now the results have been published in New England Journal of Medicine. The first media announcement and the results do not match. Unfortunately, the data do not back up the early optimism.

For researchers and research students it is important to be careful when presenting the results. Please do not be tempted to hype the results. And hype means: “Promote or publicize (a product or idea) intensively, often exaggerating its importance or benefits”.

The comments in Nature provide a good learning about presenting results: Please read Nature 2009, 461: 1187: Jury still out on HIV vaccine results.

Preventing HIV among adolescents and youth in rural Ethiopia

Mitike Molla is on May 28, 2009 defending her PhD at the University of Bergen.

The title is: Preventing HIV among young people: A community based study from Butajira on traditional norms, sexual health and HIV associated deaths. 

The health needs of young adults in Ethiopia are often neglected.  HIV is one of the major health problems among young people in Ethiopia, where the transmission often starts to pick up at the age of 15-24 years.

She interviewed 3743 young adults about sexual behaviours and sexually transmitted infections. She also asked about the attitude, opinion and knowledge of health providers towards young adults reproductive health needs. She used data from the Butajira Rural Health Programme, Demographic Surveillance Site to assess mortality trends among young adults aged 10-24 years.

She found the traditional norm of keeping virginity until marriage is still followed among the youth in rural South Central Ethiopia. Only 3% of the never-married youth had premarital sex, while almost all married youth started their union as celibates. Young adults who used alcohol, chewed khat, and did not believe in the traditional norm were more likely to have premarital sex. However, the study also showed that married women are vulnerable to HIV and other sexually transmitted diseases because of risky sexual behaviours among their husbands.

4% had had a sexually transmitted disease during the year preceding the study. Most of these were married women. Half of them who had STI symptoms did not seek help, mainly because of shame of having the infection in marriage and taboos related to premarital sex. Lack of readiness of the health services for the youth, unfavourable attitude of health professionals, women’s subordinate position in the society, and lack of knowledge about STIs among youth are possible reasons for low health seeking behaviour among young people. Six out seven of the sexually active young adults never used condoms.

Among young adults, the deaths rates declined during the period 1987-2004, with only a few deaths caused by HIV.

Upholding the traditional norm of virginity, prevention programmes should encourage HIV counselling and testing (HCT) before marriage, and faithfulness in marriage. Condom use among non-users should be encouraged and strengthened among ever-users to bring about consistent use in all non-mutual monogamous relations. The health services should be reoriented towards young adults’ SRH to improve use.

Mitike Molla’s PhD publications:

Molla M, Byass, P: Berhane Y, Lindtjørn B. Mortality decreases among young adults in south-central Ethiopia. Ethiop J Hlth Dev 2008; 22: 218-225.

Molla M, Berhane Y, Lindtjørn B. Traditional values of virginity and sexual behaviour in rural Ethiopian youth: results from a cross-sectional study. BMC Public Health. 2008;8:9.

Mitike Molla, Maria Emmelin, Yemane Berhane, and Bernt Lindtjørn. Youth in rural Ethiopia hesitate to seek health services for sexually transmitted infections: A mixed method research in Butajira, Central Ethiopia. African Journal of AIDS Research 2009, 8(2): 135–146

M. Molla A. Nordrehaug Åstrøm , Y. Berhane Y: Applicability of the theory of planned behavior to intended and self reported condom use in a rural Ethiopian population. AIDS Care, 2007, 19 (3):425-431.