Plasmodium vivax infection in South Ethiopia

Nissen A, Cook J, Loha E, Lindtjørn B: Proximity to vector breeding site and risk of Plasmodium vivax infection: a prospective cohort study in rural Ethiopia. Malaria Journal 2017, 16.

Abstract

Background  Despite falling incidence and mortality since the turn of the century, malaria remains an important global health challenge. In the future fight against malaria, greater emphasis will have to be placed on understanding and addressing malaria caused by the Plasmodium vivax parasite. Unfortunately, due to years of neglect and underfunding, there are currently many gaps in knowledge of P. vivax malaria. The aims of the present study were to explore the association between distance to vector breeding site and P. vivax infection in rural Ethiopia, and, secondarily, to test whether this association varies with age.

Methods  A prospective, cohort study of all residents in the Chano Mille Kebele in southern Ethiopia from April 2009 to March 2011 (n = 8121). Weekly household follow up visits included screening for febrile cases (active surveillance). Participants were also asked to contact the local health centre if they experienced subjective fever between visits (passive surveillance). Plasmodium vivax infection was confirmed using microscopy by two independent readers. Information was collected on demographics and household characteristics including GPS-determined distance to vector breeding site. Data was analysed using Cox regression modelling.

Results  Overall the P. vivax infection rate was 12.3/1000 person-years (95% CI 10.5–14.5). Mean household distance to breeding site was 2449 m (range 1646–3717 m). Fully adjusted results showed very strong evidence of an association between proximity to breeding site and P. vivax infection: rate ratio = 3.47 (95% CI 2.15–5.60; P < 0.001) comparing the group closest to the breeding site (distance < 2100 m; n = 1383) to the group furthest away (distance > 2700 m; n = 2460). There was no evidence that age was an effect modifier in the association.

Conclusion  Results showed strong evidence that household proximity to vector breeding site is positively associated with P. vivax infection in rural Ethiopia, and that this association is constant across age groups. The findings might influence how net-distribution and indoor residual spraying campaigns are planned, help guide strategies on water resource development by highlighting potential health effects of man-made dams near human habitats, and add to current educational information given to people living close to breeding sites.

Tuberculosis control in Arsi, Ethiopia

Shallo Daba Hamusseshallo-phd-title-page

 

 

 

 

 

 

Hamusse SD. Tuberculosis Control in Arsi in Ethiopia: Programme Performance and Disease Burden.  PhD. University of Bergen, 2017. Bergen

Tuberculosis (TB) remains a high-priority communicable disease that causes an enormous burden of morbidity and mortality, and infects one-third of the world’s population. It is the second leading cause of death among infectious diseases worldwide, with more than one-fourth of all preventable adult deaths in developing countries due to TB. The disease disproportionately affects people in resource-poor settings, particularly those in Asia and Africa. In addition, more than 80% of TB cases and 78% of deaths occur in developing countries.

The primary causes of the TB epidemic in developing countries are poor socio-economic conditions, an increase in human immuno-deficiency virus and an increase in anti-TB drug resistance, especially the MDR-TB strain. The weak and ineffective national TB control programmes, the poor implementation of infection prevention measures, the poor quality and accessibility to anti-TB drugs, the irrational use of anti-TB treatment regimens and the poor patient adherence are the underlying causes for the emergence of drug- resistant strain including MDR-TB.    The emergence of this strain therefore poses another challenge to TB control efforts.

TB control aims at detecting infectious TB cases as early as possible, and puts them on standardized anti-TB treatment in order to successfully treat and break the chain of transmission and to avert the emergency of multi-drug resistance. The effectiveness of the TB control strategy mainly depends on the timely diagnosis and treatment of smear-positive pulmonary tuberculosis. The cure of smear-positive pulmonary TB patients is considered to be an important intervention mechanism for the primary prevention and emergency of MDR-TB. As a result, a rapid identification of smear-positive pulmonary TB cases and their effective treatment using combined anti-TB drugs is the cornerstone of the global TB control programme.

In 1993, the World Health Organization (WHO) confirmed TB as a global public health emergency and recommended the Directly Observed Treatment, Short Course (DOTS) as a standard strategy to control the disease. In 1994, the World Health Organization designed a Framework for Effective Tuberculosis Control, which clearly designated the core elements of the DOTS strategy. DOTS aims at detecting 70% of infectious TB cases and successfully treating 85% of them to interrupt the transmission, reduce mortality and prevent the emergence of drug resistance.

Ethiopia is among the 22 high-TB-burden countries and the 27 high-MDR-TB-burden worldwide. TB is the leading cause of hospital admission and second leading cause of death in the country. The WHO recommended the DOTS strategy, which was piloted in 1992 and nationally launched in 1995, in a few health facilities with a subsequent expansion to all public health institutions. As a result, in 2015 all public and 14% of private health institutions were covered. The overall aim of this thesis is to assess the trends in TB control performance, and to estimate the burden of the disease at the community level to help achieve a better understanding of the gap in improving the TB control programme in Ethiopia.

The thesis investigates TB control performance, and estimates the disease burden at the community level. The studies focus on assessing trends in TB case notification and treatment outcomes. In addition, we estimate the prevalence, incidence of bacteriologically confirmed TB cases, as well as the burden of primary and secondary drug resistance TB at the community level. The findings of the studies could also be used to explore area-specific strategies help to improve TB control programmes in Ethiopia.

The studies were conducted in Arsi in central Ethiopia, and used cross-sectional and prospective cohort study designs. The studies were conducted in predominantly rural communities and at public health institutions. Most of the papers focus on smear-positive TB, the most infectious form of TB.

The study findings show that the trend in PTB+ case notification increased in parallel with the expansion of DOTS population coverage from 18% to 70% over 15 years. The PTB+ case notification increased from 7 to 63 per 100,000 population in 15 years, with an overall increase of 89%. The TB case detection rate (CDR), estimated by the proportion of PTB+ cases notified from the total annual expected PTB+ incidence of the zone, went up from 6.4% to 58.7% over the study period. The overall 15-year average PTB+ case CDR of the zone was 37.7%, which was far below the 70% global target. Moreover, the PTB+ case notification varied across the 25 districts of the zone. The rural residence and population ratio to DOTS sites and age of the patients were associated with a low TB case notification.

Between 1997 and 2011, the treatment success rates for smear-positive TB rose from 61% to 91%, with a corresponding decline in treatment failure and default rates. The 15-year average cure rate was 67%, which was lower than the global target of an 85% of cure rate. However, treatment outcomes varied across the 25 districts of the zone. The treatment success rate was also found to be associated with the age of the patient, the patient category and TB/HIV co-infection.

Trends in case notification and treatment outcomes are used as proxy indicators to evaluate the TB programme performance. However, to obtain a better understanding of the impact of the TB control programme, we need both baseline and follow-up data on the disease prevalence, incidence and drug resistance burden at the community level. Considering the shortage of resources, we used a less expensive method to estimate the prevalence and incidence of PTB+ and primary and secondary drug resistance, using symptom inquiry followed by sputum microscopy for AFB, culture and a drug-susceptibility test.

The results show that there is a high incidence of PTB+ cases. For every case PTB+ on anti-TB treatment, there was an almost equal number (0.96) of undiagnosed BCTB cases in the community. Furthermore, we identified more men undergoing treatment before the survey, whereas more women were detected during the active TB case finding. The history of TB contact was found to increase the risk of developing active TB, thus suggesting the targeting of contact-tracing among household members diagnosed with PTB+ to help capture the undetected infectious TB cases in the community. The estimation of TB prevalence and incidence based on symptom inquiry and sputum microscopy is a less expensive and simple technique. This method might help to generate information on the magnitude of TB in resource-constrained settings.

We also found that there is a high prevalence of primary and secondary resistance to any one or more first-line anti-TB drugs and primary and secondary MDR-TB in the study area. The highest prevalence of secondary drug resistance was identified among previously treated TB cases compared to primary resistance among new TB cases. This is primarily due to the poor treatment outcomes among previously treated cases caused by lost follow-up and irregularity of drug intake.

The overall 15-year average PTB+ case CDR was 38%, while the cure rate was 67%. So, after 15 years of the DOTS programme, the high proportion of undetected infectious TB cases in the community, combined with increasing primary and secondary drug resistance TB, we conclude that there has been a sub-optimal DOTS performance. Hence, this thesis underscores the need to improve DOTS performance through devising alternative strategies in TB control programmes in Ethiopia.

The thesis can be downloaded here

Malaria transmission at high altitudes in Ethiopia

Daygena TY, Massebo F, Lindtjorn B. Variation in species composition and infection rates of Anopheles mosquitoes at different altitudinal transects, and the risk of malaria in the highland of Dirashe Woreda, south Ethiopia. Parasites & vectors. 2017;10(1):343.

Background  The transmission of malaria is heterogeneous, and varies due to altitude. The information on whether the transmission of malaria is indigenous or imported to highland areas is scarce. Therefore, this study aimed to assess the species composition and infection rates of Anopheles at different altitudinal transects, and the risk of malaria if any in the highland of Dirashe Woreda, South Ethiopia.

Methods  This study was conducted in Gato (low altitude; average elevation of 1273 m), Onota (mid-altitude; average elevation of 1707 m) and Layignaw-Arguba (high altitude; average elevation of 2337 m) from August 2015 to April 2016. Anopheles mosquitoes were sampled using Centers for Disease Control and Prevention (CDC) light traps from thirty houses (ten houses from each village). The circum-sporozoite proteins (CSPs) rate and entomological inoculation rate (EIR) of Anopheles mosquitoes were estimated. For the epidemiological survey, malaria cases were collected from laboratory registration books of selected health facilities from (August 2015-April 2016). A cross-sectional survey was done to collect data on malaria vector control activities in each village (August-September 2015).

Results  One thousand two hundred sixty-eight Anopheles mosquitoes comprising Anopheles arabiensis, An. demeilloni, An. cinereus, An. pharoensis, An. funestus-group, An. pretoriensis, An. christyi, An. ardensis and An. tenebrosus were identified in the study area. Anopheles arabiensis was the dominant species in Gato, whereas An. demeilloni was the dominant species in Layignaw-Arguba. Five mosquitoes, three An. arabiensis from Gato and two An. demeilloni from Layignaw-Arguba, were positive for Plasmodium falciparum CSPs. Plasmodium falciparum CSP rate was 0.4% (95% CI: 0.08–1.15) for An. arabiensis in Gato, and it was 0.64% (95% CI: 0.08–2.3) for An. demeilloni from Layignaw-Arguba. The P. falciparum EIR of An. arabiensis was 8.6 (95% CI: 2.4–33.4) infectious bites/person/nine-months in Gato. Plasmodium falciparum was dominant in Gato (88%) and Onota (57.5%), whereas in Layignaw-Arguba P. vivax (59.4%) occurred most frequently. Increased malaria cases were observed in children age 5–14 years in Gato (P < 0.05), whereas in Onota and Layignaw-Arguba there was no statistically significant difference in malaria cases among the age groups. Households owning at least one long lasting insecticidal net were 92.7% in the study area, and 77.6% slept under the net during the preceding night of the survey. About 64.4% of the households in Gato were protected by the indoor residual spray. However, the spraying was done when the density of local malaria vectors was low.

Conclusion  Incrimination of Plasmodium CSP positive Anopheles species and the presence of malaria in children under five years in high altitude Layignaw-Arguba may justify the existence of indigenous malaria transmission and the need for effective malaria control. Further investigation and confirmation using more sensitive molecular techniques are however needed to consider An. demeilloni as a proven vector of malaria in Ethiopia.

Residual malaria transmission

Abraham M, Massebo F, Lindtjørn B: High entomological inoculation rate of malaria vectors in area of high coverage of interventions in southwest Ethiopia: Implication for residual malaria transmission. Parasite Epidemiology and Control 2017, 2:61-69.

Abstract
In Ethiopia, vector control is the principal strategy to reduce the burden of malaria. The entomological indicators of malaria transmission such as density, sporozoite rate and entomological inoculation rate (EIR) are parameters used to assess the impact of the interventions and the intensity of malaria transmission. The susceptibility of malaria vectors also determines the effectiveness of insecticide based vector control tools. Hence, the aim of the study was to assess the species composition, sporozoite rate and EIR, and insecticide susceptibility status of malaria vectors.

33 houses (18 for Centre for Disease Control and Prevention (CDC) light traps and 15 for exit traps) were randomly selected to sample Anopheles mosquitoes from October 2015 to May 2016. Plasmodium circum-sporozoite proteins (CSPs) of An. arabiensis and An. pharoensis were determined using Enzyme-Linked Immuno-Sorbent Assay (ELISA).

Five Anopheles species were identified from CDC Light traps and exit traps. An. arabiensis (80.2%) was the predominant species, followed by An. pharoensis (18.5%). An. pretoriensis, An. tenebrosus and An. rhodesiensis were documented in small numbers. 1056 Anopheles mosquitoes were tested for CSPs. Of which nine (eight An. arabiensis and one An. pharoensis) were positive for CSPs with an overall CSP rate of 0.85% (95% CI: 0.3–1.4). Five Anopheles mosquitoes were positive for P. falciparumand four were positive for P.vivax_210. P. falciparum CSP rate of An. arabiensis was 0.46% (95% CI: 0.13–1.2) and it was 0.54% (95% CI: 0.01–2.9) for An. pharoensis. The overall EIR of An. arabiensis was 5.3 infectious bites per/person (ib/p)/eight months. An. arabiensis was resistant to dieldrin (mortality rate of 57%) and deltamethrin with mortality rates of 71% but was fully susceptible to propoxur and bendiocarb. Based on the EIR of An. arabiensis, indoor malaria transmission was high regardless of high coverage of indoor-based interventions.

Finally, there was an indoor residual malaria transmission in a village of high coverage of bed nets and where the principal malaria vector is susceptibility to propoxur and bendiocarb; insecticides currently in use for indoor residual spraying. The continuing indoor transmission of malaria in such village implies the need for new tools to supplement the existing interventions and to reduce indoor malaria transmission.

The epidemiology of highland malaria in Ethiopia: a study from Butajira area

On May 30th, 2013, Adugna Woyessa defended his PhD thesis at Addis Ababa University. The PhD thesis The epidemiology of highland malaria in Ethiopia: a study from Butajira area aims to  describe human malaria transmission  in rural south central Ethiopian highlands.

Abstract

Background:In Ethiopia, malaria is a major public health problem with seasonal and unstable distribution. Because of the country’s diverse topography and climate, transmission of malaria varies with space and time; while the variability is more pronounced in highlands with low transmission. This calls for better understanding of malaria. However, there is paucity of information on magnitudeof malaria, risk factors, effective use of vector control measures such as insecticide-treated nets in relationship with malaria infection and performance of multi-species detecting malaria rapid diagnostic tests (RDTs) where Plasmodium falciparum and Plasmodium vivax co-exist at highlands of low-endemicity.

Objectives:To describe the epidemiology of highland malaria with emphasis to the magnitude and associated factors as well as interventions in various altitudesof Butajira area, south-central Ethiopia.

METHODS: Community-based repeated cross-sectional studies were conducted in six rural kebeles of Meskan and Mareko Districts from October 2008 to June 2010in Butajira area, Ethiopia. The kebeles (Hobe, Bati Lejano, Dirama, Shershera Bido, Yeteker and Wurib) were selected in such a way that two were from one altitudinal stratum thus making a total of three strata: low (1,800-1,899 meters above sea level), mid-level (1,900-1,999 meters above sea level), and high (2,000-2,300 meters above sea level) altitudes. These kebeles are part of Demographic Surveillance System Site of the Butajira Rural Health Program). A multi-stage sampling method was used to recruit study participants. The various stages were kebeles as first-stage, villages as second-stage, and households as third-stage units.   A total of 3,393 individuals were recruited from randomly sampled 750 households in 16 villages. Probability proportion to size sampling method was applied to allocate the number of households to be sampled from each kebeleand village. The study obtained data from household interview, survey and recruiting all self-reported febrile cases.  Household interview was undertaken by trained data collectors using pre-tested structured questionnaire. Household altitude reading and geo-reference was recorded from geographical positioning system location. Seasonal blood surveys were made on quarterly basis between Oct. 2008 and Jun. 2010. From the sampled households, all family members who consented to participate were requested for blood films. Besides, self-reported febrile cases were simultaneously checked for malaria infection using RDTs. CareStartTMMalaria Plasmodium falciparum/ Plasmodium vivax combo test result was compared with microscopy. Analytical tools including descriptive statistics, multilevel analysis, principal component analysis, and complex sample analysis were employed.

Main findings: The unadjusted prevalence of malaria was found to be 0.93 % [95% CI 0.79-1.07]; of 19, 207 people, 178 were positive; adjusted prevalence of malaria was estimated at 0.78 (95% CI: 0.48-1.29); of 19, 199 people, 178 were positive. Plasmodium vivax was dominant (86.5%, n=154) and the rest of the cases were due to Plasmodium falciparum (12.4%, n=22, seven with gametocyte) and mixed infections (1.1%, n=2).The prevalence varied among villages with the highest prevalence of 2.8% in Dadesso and Horosso villages (both <1,850 masl), and the lowest prevalence of 0.0% in Sunke Wenz and Akababi village (2,100-2,180 masl). Malaria prevalence decreased with altitude: 1.91% [95% CI (1.55-2.27)] in low, 1.37% [95% CI (0.87-1.87)] in mid-level and 0.36% [95% CI (0.25-0.47)] in high altitude zones; the highest prevalence was found at low altitude between October and November 2009. Moreover, malaria varied among age groups and the variation was different at different at altitudes. It reached its peak in children aged one to four yearsYonkers at mid-level and one to nine years at low altitudes. However, its prevalence at higher altitude was low and was similar across all age groups. Plasmodium falciparum malaria occurred rarely throughout the survey periods, with relatively more cases in October-November 2009 in the low altitude zone. Plasmodium vivax was found in all survey periods. However, its prevalence differed with respect to survey period and altitude. Variables like age (children aged below five and 5-9 years), altitude (low and mid-level altitude), and in houses with holes as individual-level factors; and village-level variables explained most of the variation (ICC= 94%) in individual malaria infection. The estimates of village-level variances showed well marked differences in malaria infection.

Only 28.5% [95%CI 25.8-31.4] of the 739 households surveyed owned at least an ITN.  Household ITN ownership was associated with household heads with no formal education, male-headed households, more beds in the house, absence of mosquito source reduction, and nonexistence of main water body. Male-headed households were also more associated with increased ITN ownership than female-headed ones. Households with ITN observed hanging, two and more number of ITN owned, not doing source reduction and less than a kilometredistance from main water body showed high association with use of ITN while the presence of more ITN observed hanging was a good predictor. Higher prevalence was found among people surveyed from ITN-owning than non-ITN-owning households (2.1% versus 0.5%). Malaria infection was more often observed in households owning at least an ITN than in their counterparts (unadjusted OR 4.1 [95% C.I. 2.2-7.6]; F (1, 22) =25.2, P<0.001).

Data obtained from a total of 2,394 self-reported febrile cases: 66.8% (n=1,598) from health facilities and the rest 33.2% (n=796) from surveys. Higher proportionof Plasmodium positives and both Plasmodium falciparum and Plasmodium vivaxwere detected at health facilities compared to what was seen in the survey. However, more mixed infections were observed in the latter. Low sensitivity of the test was observed in all Plasmodium species (90.8%, 95% CI: 82.9-95.3), and Plasmodium falciparum (87.5%, 52.9-97.8) in survey; and Plasmodium vivax (92.8%, 95% CI: 89.3-95.2) at health facilities. Low specificity of Plasmodium vivax (87.5%, 95% CI: 52.9-97.8) was found at the survey and all Plasmodium species (82.7%, 95% CI: 80.5-84.8) at health facilities. Very low PPV was detected in all Plasmodium species (76.7%, 95% CI: 67.7-83.8), and Plasmodium falciparum (87.5%, 95% CI: 52.9-97.8) at the survey and all Plasmodium species (64.3%, 95% CI: 60.5-68.1) and Plasmodium falciparum (77.2%, 95% CI: 67.6-84.5) at health facilities.  Low NPV was observed in Plasmodium vivax both in the survey (87.5%, 95% CI: 52.9-97.8) and health facilities (77.2: 67.6-84.5).The measure of agreement or kappa score was almost perfect agreement in all categories, except in all Plasmodium species with substantial agreement.

Conclusions and recommendations: This thesis demonstrates that low prevalence of malaria with age and altitude dependent distribution was found in highlands with low transmission in south-central Ethiopia. Plasmodium vivax was the dominant species more prevalent throughout the survey. There was very low ITN use that might have also hardly protected children in ITN-owning households. Performance of malaria RDT detecting Plasmodium falciparum and Plasmodium vivax vary between health facility-based and survey setting for both species. A malaria intervention that prioritises children below 10 years appears to be practically feasible to reduce malaria transmission. Strengthening surveillance to help in evidence-informed decision of vector control is recommendable. Furthermore, future studies should target designing more frequent survey and application of PCR for evaluation of RDT performance.

Publications:

Woyessa A, Deressa W, Ali A, Lindtjorn B. Ownership and use of long-lasting insecticidal nets for malaria prevention in Butajira area, south-central Ethiopia: complex samples data analysis. BMC public health 2014; 14: 99.

Woyessa A, Deressa W, Ali A, Lindtjørn B. Evaluation of CareStartTM malaria Pf/Pv combo test for Plasmodium falciparum and Plasmodium vivax malaria diagnosis in Butajira area, south-central Ethiopia. Malaria Journal 2013, 12:218 doi:10.1186/1475-2875-12-218

Woyessa A, Deressa W, Ali A, Lindtjørn B. Malaria risk factors in Butajira area, south-central Ethiopia: a multilevel analysis. Malaria Journal 2013, 12:273. 

Woyessa A, Deressa W, Ali A, Lindtjørn B. Prevalence of malaria infection in Butajira area, south-central Ethiopia. Malaria Journal 2012, 11:84

The full-text thesis can be downloaded here. 

Many patients remain untreated for tuberculosis

Hamusse S, Demissie M, Teshome D, Hassen MS, Lindtjorn B: Prevalence and Incidence of Smear-Positive Pulmonary Tuberculosis in the Hetosa District of Arsi Zone, Oromia Regional State of Central Ethiopia. BMC Infect Dis 2017, 17:214.

Background  The real burden of smear-positive (PTB+) and bacteriologically confirmed tuberculosis (BCTB) in Ethiopia is not known. Thus, the aim of this community-based study was to measure the prevalence and incidence of tuberculosis in the Hetosa District of Oromia Region, Ethiopia.

Methods  First, a population-based cross-sectional survey was conducted on a total of 33,073 individuals aged ≥ 15 years to determine the prevalence of PTB+ and BCTB cases. Then, in order to determine the incidence, a prospective follow-up was carried out on 32,800 individuals found to be either free from symptoms suggestive of TB (SSTB) during the baseline survey or had symptoms suggestive of TB but yielded negative bacteriological examination results. We identified 1,041 presumptive TB cases at the baseline survey, and 1,468 in the follow-up study. Each participants with cough of more than two weeks were provided spot and morning sputum samples for acid-fast bacilli sputum microscopy and culture.

Results  At the baseline survey, 43 BCTB cases were identified. Thirty six of these were both smear- and culture-positive while seven were only culture-positive. In the follow-up study, however, 76 BCTB cases were diagnosed and 70 of these were found to be both smear- and culture-positive while six were culture-positive only. The adjusted prevalence of PTB+ and BCTB in the study area was 109 and 132/100,000 persons, respectively. Moreover, the incidences of PTB+ and BCTB were 214 and 232/100,000 persons per year (py), respectively. The ratio of the passive to active case finding was 1:0.96 (45/43). For every TB case identified through the existing passive case diagnosis, there was an almost equal number (0.96) of undiagnosed infectious TB cases in the community. A family history of TB contact was independently associated with a high risk of TB (TB prevalence, AOR, 13; 95% CI: 6.55–15.33) and (TB incidence, aIRR 4.11, 95% CI: 2.18–7.77).

Conclusions and recommendations  The prevalence and incidence of smear-positive and bacteriologically confirmed TB cases were high in the study area. For every case of smear-positive TB receiving treatment, there was an almost equal (0.96) number of undetected infectious bacteriologically confirmed TB case in the community. The high proportion of undetected infectious TB cases in the community could possibly be due to the sub-optimal performance of Directly Observed Treatment Short-course (DOTS) in detecting 70% of infectious TB cases, as well as attaining a cure rate of 85% in the study area. Family history of TB contact has substantaially increased the risk of developing the disease, and there is a need to improve ways of identifying TB cases and intensify mechanisms of tracing contacts among household members of PTB+ cases.

Anaemia, drought and malaria in Ethiopia

Gari T, Loha E, Deressa W, Solomon T, Atsbeha H, Assegid M, Hailu A, Lindtjørn B. (2017) Anaemia among children in a drought affected community in south-central Ethiopia. PLoS ONE 12(3): e0170898. doi:10.1371/journal.pone.0170898

Introduction  As part of a field trial (PACTR201411000882128) to provide evidence on the combined use of long-lasting insecticidal nets and indoor residual spray for malaria prevention, we measured haemoglobin values among children aged 6 to 59 months. The aim of this study was to estimate the prevalence of anaemia, and to determine the risk factors of anaemia and change in haemoglobin value in Adami Tullu district in south-central Ethiopia.

Methods  Repeated cross-sectional surveys among 2984 children in 2014 and 3128 children in 2015; and a cohort study (malaria as exposure and anaemia as outcome variable) were conducted. The study area faced severe drought and food shortages in 2015. Anaemia was diagnosed using HemoCue Hb 301, and children with haemoglobin <11 g/dl were classified as anaemic. Multilevel and Cox regression models were applied to assess predictors of anaemia.

Results  The prevalence of anaemia was 28.2% [95% Confidence Interval (CI), 26.6–29.8] in 2014 and increased to 36.8% (95% CI, 35.1–38.5) in 2015 (P<0.001). The incidence of anaemia was 30; (95% CI, 28–32) cases per 100 children years of observation. The risk of anaemia was high (adjusted Hazard Ratio = 10) among children with malaria. Children from poor families [Adjusted Odds Ratio (AOR); 1.3; 95% CI, 1.1–1.6)], stunted children (AOR 1.5; 95% CI; 1.2–1.8), and children aged less than 36 months (AOR; 2.0; 95% CI, 1.6–2.4) were at risk of anaemia compared to their counterparts. There was no significant difference in risk of anaemia among the trial arms.

Conclusions  Young age, stunting, malaria and poverty were the main predictors of anaemia. An increase in the prevalence of anaemia was observed over a year, despite malaria prevention effort, which could be related to the drought and food shortage. Therefore, conducting trials in settings prone to drought and famine may bring unexpected challenges.

Entomological evaluation of vector control

oljira-phd-thesis-cover

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