Cattle and Control of Malaria

Massebo F, Balkew M, Gebre-Michael T, Lindtjorn B. Zoophagic behaviour of anopheline mosquitoes in southwest Ethiopia: opportunity for malaria vector control. Parasites & vectors 2015; 8(1): 645.

Background

Increased understanding of the feeding behaviours of malaria vectors is important to determine the frequency of human-vector contact and to implement effective vector control interventions. Here we assess the relative feeding preferences of Anopheles mosquitoes in relation to cattle and human host abundance in southwest Ethiopia.

Methods

We collected female Anopheles mosquitoes bi-weekly using Centers for Disease Control and prevention (CDC) light traps, pyrethrum spray catches (PSCs) and by aspirating from artificial pit shelters, and determined mosquito blood meal origins using a direct enzyme-linked immunosorbent assay (ELISA).

Results

Both Anopheles arabiensis Patton and An. marshalli (Theobald) showed preference of bovine blood meal over humans regardless of higher human population sizes. The relative feeding preference of An. arabiensis on bovine blood meal was 4.7 times higher than that of human blood. Anopheles marshalli was 6 times more likely to feed on bovine blood meal than humans. The HBI of An. arabiensis and An. marshalli significantly varied between the collection methods, whereas the bovine feeding patterns was not substantially influenced by collection methods. Even though the highest HBI of An. arabiensis and An. marshalli was from indoor CDC traps collections, a substantial number of An. arabiensis (65 %) and An. marshalli (63 %) had contact with cattle. Anopheles arabiensis (44 %) and An. marshalli (41 %) had clearly taken bovine blood meals outdoors, but they rested indoors.

Conclusion

Anopheles mosquitoes are zoophagic and mainly feed on bovine blood meals than humans. Hence, it is important to consider treatment of cattle with appropriate insecticide to control the zoophagic malaria vectors in southwest Ethiopia. Systemic insecticides like ivermectin and its member eprinomectin could be investigated to control the pyrethroid insecticides resistant vectors.

Malaria prevention trial

MalTrials-poster-Challenges in Malaria Research1Deressa W, Loha E, Balkew M, Desalegne A, Gari T, Gebremichael T, Kenea O, Jima D, Robberstad B, Overgaard H, Lindtjorn B: Combining long-lasting insecticidal nets and indoor residual spraying for malaria prevention in Ethiopia: study protocol for a cluster randomized controlled trial. Malaria Journal 2014, 13:P25.

Poster presentation

Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the two main malaria prevention strategies in Ethiopia. Although both interventions have been shown to be effective in reducing malaria transmission when applied independently, there is conflicting evidence that the two in combination is better than either one alone. The main objectives of this trial are to determine the added protection value against malaria and to evaluate the cost-effectiveness when applying IRS and LLINs together, or LLINs or IRS independently.

This trial will be conducted in Adami Tullu district of Oromia Regional State in Ethiopia from 2014 to 2016. The project will use a cluster randomized controlled trial, with four “arms”: IRS+LLINs, LLINs alone, IRS alone and control (routine practice). The sample size includes 40 clusters in each arm, each cluster with 35-45 households. Each household and each inhabitant in the household will be given a unique identification number. Households will be mapped using global positioning system. At the start of the trial, all households in the IRS+LLINs and LLINs alone “arms” of the study will be provided new LLINs free of charge. IRS with an insecticide (propoxur) will be applied in IRS+LLINs and IRS alone arms twice a year throughout the study.

Each household will be visited weekly, and blood samples will be collected from each household member with fever or history of fever. Thick and thin blood smears will be taken by finger prick and rapid diagnostic tests will be used to detect malaria at field level. Data on all self-reporting malaria patients attending health posts will be collected. The cost-effectiveness and entomological studies will be simultaneously conducted. Analysis will be based on intention to treat principle. Ethical clearance was obtained from the Ministry of Science and Technology in Ethiopia and the University of Bergen.

This trial aims to provide evidence on the combined use of IRS and LLINs for malaria prevention. We aim to answer the following research questions: Can the combined use of LLINs and IRS significantly reduce malaria incidence compared with the use of LLIN or IRS alone? And is the reduced incidence justifiably compared to the added costs? Will the combined use of LLINs and IRS reduce vector density, infection, longevity and the entomological inoculation rate? Such data is crucial in order to maximize the impact of the intervention on malaria morbidity and mortality.

MalTrials-poster-Challenges in Malaria Research

Strengthening malaria and climate research in Ethiopia

Lindtjorn-Malaria conference posterLindtjorn B, Loha E, Deressa W, Balkew M, Gebremichael T, Sorteberg A, Woyessa A, Animut A, Diriba K, Massebo F, et al: Strengthening malaria and climate research in Ethiopia. Malaria Journal 2014, 13:P56.

Poster presentation

The project “Ethiopian Malaria Prediction System” implemented from 2007 to 2012 combined new population-based malaria transmission information with climate and land use variability data to develop an early warning tool to predict malaria epidemics in Ethiopia. Scientists from Ethiopia and Norway collaborated to incorporate climate variability and forecast information for malaria epidemics.

Our study shows that the association between weather and malaria is complex. Statistical models can predict malaria for large areas. However, as malaria transmission varies and depends on local environmental conditions, we need to have good and local knowledge about each area. However, weather variability is the main driver of malaria in Ethiopia.

While the generation of precipitation depends on local ascent and cooling of the air, our research provided new data on the transport of moisture into the country that may improve weather forecasting. We developed a new classification of climate zones, have mapped drought episodes in Ethiopia during the last decades, and have improved seasonal weather forecasting. Our hydrology studies show that potential climate change differs among the Ethiopian river basins, with river flows being sensitive to variations in rainfall, and less to temperature changes.

The computer model, Open Malaria Warning, incorporates hydrological, meteorological, mosquito-breeding, land-use data, and cattle densities to find out when and where outbreaks are likely to occur. We validated the model with data for malaria transmission in the highlands and lowlands, characterizing malaria transmission over some years in both highlands and lowlands. This provided us with new knowledge on malaria transmission in Ethiopia, how intense the seasonal transmission is, and how malaria occurs in different populations and areas. Our study showed that indigenous malaria transmission during a non-epidemic year takes place above 2000 m altitude. We also showed the ideal temperature for malaria transmission is about 25°C, underlining that global warming may lead to increased risk of malaria in highland areas, and less in the lowlands with already high average temperatures. However, to validate such models, there is a need for several years of active monitoring of malaria cases and mosquito densities. Unfortunately, such data is rare in Africa, and we need to invest in long-term monitoring of malaria transmission.

Lindtjorn-Malaria conference poster

Ownership and use of long-lasting insecticidal nets for malaria prevention in Ethiopia

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.

BACKGROUND: Despite the encroaching of endemic malaria to highland-fringe areas above 2000 meters above sea level in Ethiopia, there is limited information on ownership and use of mosquito nets for malaria prevention. Thus, this study was designed to assess long-lasting insecticidal nets (LLIN) possession and use for malaria prevention in highland-fringe of south-central Ethiopia.

METHODS: A multi-stage sampling technique was employed to obtain household data from randomly selected households using household head interview in October and November 2008. Household LLIN possession and use was assessed using adjusted Odds Ratio obtained from complexsamples logistic regression analysis.

RESULTS: Only less than a quarter (23.1%) of 739 households interviewed owned LLINs with more differences between low (54.2%) high (3.5%) altitudes (Χ2 =253, P < 0.001). Higher LLIN ownership was observed in illiterate (adj.OR 35.1 [10.6-116.2]), male-headed (adj.OR 1.7 [1.051-2.89]), owning two or more beds (adj.OR 2.7 [1.6-4.6]), not doing draining/refilling of mosquito breeding sites (adj.OR 3.4 [2.1-5.5]) and absence of rivers or streams (adj.OR 6.4 [3.5-11.8]) of household variables. The presence of ≥2 LLINs hanging (adj.OR 21.0 [5.2-85.1]), owning two or more LLINs (adj.OR 4.8 [1.3-17.5]), not doing draining/refilling of mosquito breeding sites (adj.OR 4.2 [1.3-13.6]), low wealth status (adj.OR 3.55 [1.04-12.14]), and < 1 km distance from absence of rivers or streams (adj.OR 3.9 [1.2-12.1]) of households was associated with more likely use of LLIN. The LLIN ownership was low in the highlands, and most of the highland users bought the bed nets themselves.

CONCLUSIONS: This study found a low household LLIN ownership and use in the highland-fringe rural area. Therefore, improving the availability and teaching effective use of LLIN combined with removal of temporary mosquito breeding places should be prioritized in highland-fringe areas.

Screening houses prevents malaria

The results of this randomized trial show that screening doors and windows, and closing openings on walls and eves by mud reduced the overall indoor densities of An. arabiensis by 40%. Although screening intervention reduced indoor density of An. arabiensis at all abdominal stages, the reduction was substantially higher against unfed An. arabiensis. The intervention was based on locally bought materials, and was affordable.

 Massebo F, Lindtjorn B. The effect of screening doors and windows on indoor density of Anopheles arabiensis in south-west Ethiopia: a randomized trial. Malar J 2013; 12(1): 319.

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.

Two new malaria articles

Our malaria research group recently published two new articles about malaria in south Ethiopia:

Massebo F, Balkew M, Gebre-Michael T, Lindtjorn B. Entomologic Inoculation Rates of Anopheles arabiensis in Southwestern Ethiopia. Am J Trop Med Hyg 2013.

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. 

South Ethiopia Network of Universities in Public Health

The Norwegian Programme for Capacity Development in Higher Education and Research for Development (NORHED) recently told us that we have been awarded the project:  South Ethiopia Network of Universities in Public Health (SENUPH): improving women’s participation in post-graduate education. 

The vision of this project is to enhance the capacity of universities in south Ethiopia to train sufficient staff for the Region to carry out essential public health work, and do essential research to improve the health of the people living in South Ethiopia. This will be carried out by:

  • Establishing, and strengthening a network of the main universities in south Ethiopia doing teaching so the universities can increase their teaching capacity and train enough staff to meet the demands within the public health sector.
  • Substantially increasing the number of women with postgraduate education
  • Increasing the number of teachers at the universities in public health.
  • Strengthening the research capacity through PhD and Master’s programme so the research done in the region will aid in defining the future health policy.

This project has four integrated parts:

  • A PhD programme for all universities and located at Hawassa University
  • A master programme in Maternal and Reproductive health at Dilla University
  • A master programme in Nutrition at Wolaita Soddo University and
  • A master programme in medical entomology (malaria control) at Arba Minch University).

By developing a network of the main universities in south Ethiopia we will address several important areas such as staff development, and enhance the human capacity in higher education, in public health, reproductive health, and nutrition and malaria control.

The Southern Nations, Nationalities  and Peoples Region in Ethiopia has a population of about 16 million people, representing  more than 50 ethnic groups that live in a variety of geographic and socioeconomic areas. The area is typical of Ethiopia with high population densities, high fertility and child mortality rates, and high maternal death rates.