During its Annual General Meeting held on 18 November 2020, the icipe Governing Council, which consists of globally renowned scientists, honoured six outstanding postgraduate scholars, currently undertaking their research at the Centre.

Best published science paper by an icipe scholar

Emily Kajuju Kimathi (MSc Scholar)
icipe Mentors – Drs. Henri E. Z. Tonnang & Elfatih M. Abdel-Rahman

Paper: Kimathi E., Tonnang H.E.Z., Subramanian S., Cressman K., Abdel-Rahman E.M., Tesfayohannes M., Niassy S., Torto B., Dubois T., Tanga C.M., Kassie M., Ekesi S., Mwangi D. and Kelemu S. (2020) Prediction of breeding regions for the desert locust Schistocerca gregaria in East Africa. Scientific Reports 10, 11937. https://doi.org/11910.11038/s41598-11020-68895-11932. IF 3.998

Contribution to Science: Extensive unprecedented invasion of desert locust continues to be experienced in the horn of Africa, with many parts of the affected countries undergoing huge economic losses and food insecurity. This research work aimed at understanding the habitat niches of the desert locust breeding sites in the affected countries. The paper entails applying an ecological niche modelling approach towards predicting the breeding sites of desert locust in East Africa. The model outputs indicate the spatial distribution of the various suitability levels of the breeding grounds hence highlighting the hotspot areas that require intervention. The modelling work utilizes a large historical dataset of desert locust hoppers and bands collected in the Sahel region and the middle East countries to project similar breeding conditions in Kenya, Uganda, South Sudan, and Sudan. This timely paper was the first study to model and predict the desert locust breeding grounds when the recent 2020 desert locust surge was at its peak in East Africa. The study utilized secondary data (n = 5,406 records) to conduct the modelling exercise following the open science concept on re-use of data for further discovery. This was also in line with the limitation incurred due to the current COVID-19 pandemic which restricted field work to collect up-to-date data on desert locust. The modelling criteria was also quite unique and innovative whereby predictive models for three countries (Morocco, Mauritania and Saudi Arabia) in the recession region were developed and later projected to the invaded countries (Kenya, Uganda, South Sudan and Sudan) using an advanced machine-learning ecological niche modelling algorithm. Furthermore, the models underwent a three-step validation and evaluation protocol, making the results more robust, reliable, and up-scalable.

The research work provides information that could be utilized by governments, NGO’s, NARS (national agricultural research systems) and stakeholders to identify areas that are highly suitable for desert locust breeding. This provides site-specific, targeted, and cost-effective surveillance and advisory tool to combat the pest. By adapting the model outputs developed in this paper, a timely and effective management of crawling hopper bands before they emerge into gregarious immature adults will be possible, thus a future desert locust outbreak risk will be minimized. This paper was published on 20^th July 2020, and so far, (15^th December 2020) it is accessed 3851 times.

Funding: We acknowledge the financial support for this research by the following organizations and agencies: the UK’s Foreign, Commonwealth & Development Office (FCDO), the Swedish International Development Cooperation Agency (SIDA), the Swiss Agency for Development and Cooperation (SDC), and the governments of Kenya and Ethiopia. We also wish to thank FAO, DLCO-EA and the Ministry of Agriculture, Kenya for sharing valuable field data that enabled further modelling activity. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

University: The scholar is registered at University of Nairobi, Kenya

Juliet Akoth Ochola (MSc Scholar)
icipe Mentor – Dr. Baldwyn Torto

Paper:  Ochola J., Cortada L., Ng’ang’a M., Hassanali A., Coyne D. and Torto B. (2020) Mediation of potato–potato cyst nematode, Globodera rostochiensis interaction by specific root exudate compounds. Frontiers in Plant Science 11, 649. [https://doi:610.3389/fpls.2020.00649]https://doi:610.3389/fpls.2020.00649 IF 4.407

Contribution to science:  Potato is the second most important food crop in Kenya, mainly grown by small-holder farmers as a food crop and a source of income. In the recent years, there has been a major reduction in potato production in the country despite the increase in the area cultivated. Several factors may account for this including the invasive species, potato cyst nematode, G. rostochiensis (PCN). PCN can cause yield losses of between 80% to total crop failure under high infestation. Management of PCN is a great challenge due to encystment of the nematode eggs in a protective casing that enables it to survive for prolonged periods in the absence of a host. Most of the available PCN management strategies have limited applicability in Africa where the agricultural sector is dominated by small-holder farmers that lack adequate land, extension services, support and appropriate national phytosanitary policies to combat PCN infestation.

Therefore, there is a pressing need to develop innovative solutions for PCN management that can be easily adopted. PCN is a host-specific nematode that relies on host root exudates for hatching, thus, use of synthetic compounds in the field setting to trigger suicidal hatching in the absence of a host plant offers great potential for its management. This study investigated the role of host plant-derived compounds in PCN hatching and evaluated their potential use to induce ‘suicidal hatching’. Of the several classes of compounds identified in the potato root exudates, only the steroidal glycoalkaloids, α-solanine and α-chaconine (known hatching principles) and steroidal alkaloids, solanidine, solasodine and tomatidine stimulated PCN hatching in a dose-dependent manner. The latter three compounds are reported for the first time as PCN hatching factors. Additionally, the study also found that most of the juveniles that hatched in response to these hatching factors failed to emerge from the cyst. These findings offer an environmentally-friendly approach that utilizes naturally occurring plant-derived compounds to manage PCN. It also opens avenues for exploitation of other economically valuable plants producing these compounds for their incorporation into a crop rotation system or their parts for use as organic amendments to reduce nematode densities to non-damaging levels.

Funding: We gratefully acknowledge the financial support for this research by North Carolina State University; Root Tubers and Bananas Cluster of the CGIAR and Bill and Melinda Gates foundation. We also acknowledge the financial support by icipe’s core donors, the UK’s Foreign, Commonwealth & Development Office (FCDO), the Swedish International Development Cooperation Agency (SIDA), the Swiss Agency for Development and Cooperation (SDC), and the governments of Kenya and Ethiopia.  The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

University: The scholar is registered at Kenyatta University, Kenya

Akbar Ganatra (PhD Scholar)
icipe Mentor - Dr. Ulrike Fillinger

Paper: Becker J.M., Ganatra A.A., Kandie F., Mühlbauer L., Ahlheim J., Brack W., Torto B., Agola E.L., McOdimba F., Hollert H., Fillinger U. and Liess M. (2020) Pesticide pollution in freshwater paves the way for schistosomiasis transmission. Scientific Reports 10, 3650. https://doi.org/3610.1038/s41598-41020-60654-41597.  IF 3.998

Contribution to science:  Schistosomiasis, also called bilharzia, is among the tropical diseases with the highest impact on socio-economic development, only exceeded by malaria.  It is a severely neglected tropical disease caused by trematodes and transmitted by freshwater snails. Snails are known to be highly tolerant to agricultural pesticides. However, little attention has been paid to the ecological consequences of pesticide pollution in areas endemic for schistosomiasis, where people live in close contact with non-sanitized freshwaters. In complementary laboratory and field studies on Kenyan inland areas along Lake Victoria, we show that pesticide pollution is a major driver in increasing the occurrence of host snails and thus the risk of schistosomiasis transmission.

Experiments in Europe first discovered that the sensitivity of freshwater macroinvertebrates to pollution could be used as a scale for pollution and noticed that some of the least sensitive taxa to pesticide pollution belong to the Schistosoma-hosting family of Planorbidae snails. We conducted similar experiments verifying the scale for African macroinvertebrates, which similarly showed that the Schistosoma-host snails of the region, Biomphalaria pfeifferi and Bulinus africanus were the most tolerant of two commonly found pesticides, a neo-nicotinoid Imidacloprid, and an organophosphate Diazinon. We also conducted a field study across the western Kenyan region, known for its high rate of schistosomiasis, looking for snail habitats across maize, rice, tea and sugarcane farms. We found that the snail hosts were only present in waters that were at least moderately polluted (TU > -3). By analyzing the community composition at differently polluted sites, we found that the proportion of grazers to predators does not change much due to pollution, however, the more polluted sites begin to get dominated by snail taxa, especially those of the host taxa of Planorbidae. Thus, were able to determine that the snails, being more tolerant to pesticides than their competitors (as shown by LC50s), dominate waters as pollution increases thus increasing a risk of disease by increasing the range of the snail host.

The study shows for the first time that in the field, pesticide concentrations considered “safe” in environmental risk assessment have indirect effects on human health. The study adds to the evidence of pesticide pollution exacerbating the prevalence of schistosomiasis by demonstrating the potential of an increased number of hosts for the parasite by affecting their competitors. It also adds to the list of negative effects of pesticides that were previously uncharacterized and therefore not considered. The study added several taxa’s data to the available toxicity information available for various macroinvertebrates, of which there were previously none for African taxa. Thus, we conclude there is a need for rethinking the environmental risk of low pesticide concentrations and of integrating agricultural mitigation measures in the control of schistosomiasis.

Funding: Akbar Ganatra work was supported by the DFG (Deutsche Forschungsgemeinschaft), grant number LI 1708/4-1, BR 2931/3-1, HO 3330/12-1 and the German Helmholtz long-range strategic research funding. We also gratefully acknowledge the financial support for this research by icipe’s core donors, Financial support for this research was also provided by the UK’s Foreign, Commonwealth & Development Office (FCDO), the Swedish International Development Cooperation Agency (SIDA), the Swiss Agency for Development and Cooperation (SDC), and the governments of Kenya and Ethiopia. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

University: The scholar is registered at Egerton University, Kenya.

Best science poster by an icipe scholar

Mary Wanjiku Chege (MSc. Scholar)

Poster:  Gut symbionts reduce immune response activation and protect the honeybee, Apis mellifera, against opportunistic pathogens

Supervisors: 

Dr. Juan C. Paredes, International Centre of Insect Physiology and Ecology (icipe)

Dr. Johnson Kinyua, Jomo Kenyatta University of Agriculture and Technology

Brief Summary: The honeybee, Apis mellifera, is the most important managed agricultural pollinator and their important colony losses are of global concern hence, bee health is recognized as a priority. The honeybee harbor beneficial gut microbiota that plays a vital role in the bee immunity, nutrition, and protection against pathogens. Recent studies have been exploiting the use of gut beneficial bacteria as probiotics to improve bee health. In this study, we explored the survival rates and immune activation of honeybee workers mono-inoculated with a single gut symbiotic bacterium, Lactobacillus kunkeei. We also, monitored L. kunkeei protection against opportunistic pathogen, Serratia marcescens with the aim of finding the potential beneficial capability of L. kunkeei on protecting the bee against its natural pathogens.

Our findings show that L. kunkeei can effetely colonize the gut of newly emerged germ-free bees and that mono-inoculated bees with L. kunkeei show a slightly shorter life span and stronger basal immune response compared to germ free and bees harboring their normal gut microbiota. However, when bees are exposed to opportunistic pathogens, mono-inoculated bees showed a reduced or similar immune response than germ free bees although, better survival rates and reduced pathogen infection. Our results show that L. kunkeei protects the bee against opportunistic pathogens with very minor side effects on bee physiology. These results set up the bases for the use of bee gut microbiota, especially L. kunkeei, as potential probiotics to increase bee health and reduce colony losses. The data generated here also, contribute to the understanding of how opportunistic pathogens affect the host immune system, and how they can negatively contribute to bee health.

Funding: This work was supported by the Newton Fund, the UK’s Foreign, Commonwealth & Development Office (FCDO), the Swedish International Development Cooperation Agency (SIDA), the Swiss Agency for Development and Cooperation (SDC), and the governments of Kenya and Ethiopia. The views expressed herein do not necessarily reflect the official opinion of the donors.

University: The scholar is registered at Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya.

Francis Sengendo (MSc. Scholar)

Poster title: Improving efficiency and profitability of light trap for harvesting edible grasshoppers Ruspolia differens in Uganda.

Supervisors: Dr. Sevgan Subramanian,¹Dr. Moses Chemurot,²Dr. Michael Kidoido¹, Dr. Chrysantus Tanga¹ and Dr. James P. Egonyu.¹

¹International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya

²Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, Makerere University, P.O. Box 7062, Kampala, Uganda

Brief Summary: In Uganda, Ruspolia differens is a delicacy and it is commercially trapped using light traps which consist of mercury bulbs and open-ended metallic drums. The mercury bulbs are energy intensive and pollute the environment when poorly disposed. The collection drums are inefficient in retaining the catch, and collect many non-target insects, especially the notorious Nairobi fly (Paederus sp). To prevent escape of the harvest, commercial trappers apply substances like waste cooking oil on the walls of drums, which contaminate the harvest. In this study, the collection drum was modified by fitting a funnel to retain R. differens and partitioning it into three compartments with wire meshes of variable sizes to filter non-target insects. Mercury bulbs were replaced with light emitting diode (LED) bulbs, of 100, 200 and 400 wattage which are energy efficient and do not release mercury to the environment. Efficiency and profitability of the improved light trap were compared with the commonly used trap in Masaka, Uganda in 2019. Modified drums capture the same quantity of R. differens as the current drums, but with significantly reduced contamination with non-target insects. Catches of R. differens using 400W LED lamps and 400W mercury bulbs are comparably, but the LED lamps consume twice lower energy than the mercury lamps. The improved trap was more profitable than the current trap. 

Funding: This research was funded by the following organizations and agencies: The Federal Ministry for Economic Cooperation and Development (BMZ) (ENTONUTRI–81194993) and BioInnovate Africa Programme Phase II through Sida (INSBIZ -Contribution ID No. 51050076); UK’s Foreign, Commonwealth & Development Office (FCDO); the Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC); the Federal Democratic Republic of Ethiopia; and the Government of the Republic of Kenya.  . The views expressed herein do not necessarily reflect the official opinion of the donors.

University: The scholar is registered at Makerere University Kampala Uganda.

Kevin Kidambasi Ogola (MSc. Scholar)

Poster Title: Xenodiagnosis potential and the vectorial competence of camel biting keds (Hippobosca camelina) in disease transmission

Supervisors: Dr. Daniel K. Masiga¹, Dr. Merid N. Getahun¹, Dr. Jandouwe Villinger¹, Prof. Mark Carrington³, Dr. Joel L. Bargul^1,2

¹International Centre of Insect Physiology and Ecology (icipe) Kenya, ²Jomo Kenyatta University of Agriculture and Technology (JKUAT), Kenya, ³University of Cambridge, UK

Brief Summary: Anaplasmosis is a livestock disease caused by a group of gram-negative bacteria belonging to the genus Anaplasma. Transmission of these pathogens can occur via infected ticks during blood feeding¹ or mechanically by haematophagous biting flies^2,3. We detected pathogens such as Anaplasma, Bartonella, Ehrlichia, and Trypanosoma spp. in camels and their blood-sucking keds (Hippobosca camelina) suggesting the potential application of these flies in xenodiagnosis of blood-borne pathogens that they may also transmit⁴. We also studied the vectorial competence of camel keds in transmission of “Candidatus Anaplasma camelii” from naturally-infected camels to laboratory mice and rabbits. We demonstrate for the first time the vector competence of camel biting keds, Hippobosca camelina, to transmit camel anaplasmosis.

1. Kocan KM. Targeting ticks for control of selected hemoparasitic diseases of cattle. Vet Parasitol. 1995  
2. Scoles GA, Broce AB, Lysyk TJ, Palmer GH. Relative Efficiency of Biological Transmission of Anaplasma marginale (Rickettsiales: Anaplasmataceae) by Dermacentor andersoni (Acari: Ixodidae) Compared with Mechanical Transmission by Stomoxys calcitrans (Diptera: Muscidae). J Med Entomol. 2006 
3. Scoles GA, Miller JA, Foil LD. Comparison of the efficiency of biological transmission of Anaplasma marginale (Rickettsiales: Anaplasmataceae) by Dermacentor andersoni stiles (Acari: Ixodidae) with mechanical transmission by the horse fly, Tabanus fuscicostatus hine (Diptera: Muscidae). J Med Entomol. 2008 
4. Kidambasi KO, Masiga DK, Villinger J, Carrington M, Bargul JL. Detection of blood pathogens in camels and their associated ectoparasitic camel biting keds, Hippobosca camelina: the potential application of keds in xenodiagnosis of camel haemopathogens. AAS Open Res. 2020

Funding: We gratefully acknowledge the financial and technical support of our core donors: Swiss Agency for Development and Cooperation (SDC), Switzerland; Swedish International Development Cooperation Agency (Sida), Sweden, UK’s Foreign, Commonwealth & Development Office (FCDO), Ministry of Higher Education, Science and Technology, Kenya; and Government of the Federal Democratic Republic of Ethiopia. Project donors: DELTAS Africa Initiative grant # DEL-15-011 to THRiVE-2, IFS grant # B/5925-1 and Cambridge-Africa Alborada Fund 2017/18.  The views expressed herein do not necessarily reflect the official opinion of the donors.

University: The scholar is registered at Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology (JKUAT), Nairobi, Kenya.