This study was presented during the conference “Production and Carbon Dynamics in Sustainable Agricultural and Forest Systems in Africa” held in September, 2010.

1. Chemoecological management of malaria mosquitoes
Rickard Ignell, PhD, Division of Chemical Ecology, Dpt of Plant Protection Biology, Swedish
University of Agricultural Sciences (SLU)
ABSTRACT
Globally, malaria annually affects about 300 million people and causes about one million deaths, mostly
among children in sub-Saharan Africa. In this region, the mosquito, Anopheles gambiae, is considered the
most efficient vector of malaria. Due to its socio-economical importance, several countries are implementing
vector control activities in an attempt to curtail the malaria epidemic. Vector control interventions, combining
insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS) have suppressed An. gambiae
populations in some malaria-endemic areas in sub-Saharan Africa. However, in other areas, such as the
western part of Kenya, while the impact of ITNs and IRS on An. gambiae has been dramatic, these
intervention methods have had very little impact on the populations of An. arabiensis. There is growing
evidence that the void created by the low populations of An. gambiae is being filled by An. arabiensis since
current malaria infections in these areas are caused by the latter rather than the former species. The potential
for a similar pattern of malaria infection, with An. arabiensis as the principal malaria vector, in other parts of
Africa where the two malaria vectors co-occur after intervention with ITNs and IRS is very high.
A call has recently been issued for worldwide, integrated efforts to prevent further deterioration of the
malaria situation. One such effort focuses on the exploitation of the chemical ecology of Anopheles
mosquitoes to reduce the interactions with humans. In a recently initiated study we at SLU are trying to
develop a low-input bait technology for trapping and repelling An. arabiensis.

2. Chemoecological management of malaria mosquitoes
Rickard Ignell, PhD
Division of Chemical Ecology
Department of Plant Protection Biology
Swedish University of Agricultural Sciences (SLU)
Production and Carbon Dynamics in Sustainable Agriculture and Forest Systems in Africa
Policy, Economics and Incentives Stockholm September 2010

3. Malaria is an Anopheles mosquito-borne disease caused by
four species of the parasitic protist genus Plasmodium
Anopheles gambiae Plasmodium falciparum attacking
human red blood cells

4. Global malaria distribution and endemicity
UNICEF, WHO 2005

5. Global human toll of malaria – malaria cases
Between 350 million and 500 million episodes of clinical malaria occur each year
Worldmapper project

6. Global human toll of malaria - deaths
1-1.5 million people die each year, predominantly in sub-Saharan Africa
Worldmapper project

7. In sub-Saharan Africa, malaria is one of the major causes of death of
children under the age five, accounting for nearly 1 death in 5
UNICEF, WHO 2005
Distribution of deaths among children under age five
by cause, global and sub-Saharan Africa, 2000–2003

8. Global human toll of malaria - poverty
Worldmapper project
“Malaria is both a root cause and a consequence of poverty. Malaria is most intractable for
the poorest countries and communities in the world that face a vicious cycle of poverty
and ill health”. The Earth Institute

9. Global human toll of malaria – gross domestic product
Worldmapper project
Malaria can decrease GDP by 1.3% in countries with high disease rates

10. Tabachnick, W. J. J Exp Biol 2010;213:946-954
The vector-borne disease episystem illustrating interactions between
selected environmental factors with effects on the vector--pathogen--
host epidemiologic cycle

11. In Africa, malaria is predominantly a rural disease where agriculture
forms the backbone of the economy

12. 0 20 40 60 80 100
0 1 2 3 4
Flooding rice irrigation
Non-flooding rice irrigation
Wet savannah
Sugarcane
Dry savannah
Various agro-ecosystems and crop production systems have an impact
on mosquito productivity, and malaria transmission intensity.
% of mosquitoes
Plasmodium sporozite rate (%)
Mboera et al (2010) Geospatial Health 4(2), 2010, pp. 167-178
Mvomero district, Tanzania

13. Changes in agro-ecosystems and crop production systems may affect
malaria transmission.
Kebede et al (2005) Am J Trop Med Hyg 73(4): 676–680
Bure
Malaria incidence rate/10.000 person-years
Maizecultivationintensity
0 100 200 300
High
Medium
Low

14. Indoor residual spraying (IRS)
Insecticide treated mosquito nets (ITNs)
Vector control of malaria is the primary public health intervention for
reducing malaria transmission at the community level
Other methods

15. Griffin et al (2010) Plos Medicine 7:e1000324
Interventions have resulted in major reductions in malaria transmission,
and provided an efficient control of endophilic Anopheles mosquitoes

16. 0 10 20 30 40 50
Permethrin
Deltamethrin
Lambda-cyhalothrin
Bendiocarb
DDT
Malathion
Insecticide resistance (%)
Cuamba et al (2010) Plos ONE 5: e11010
High levels of insecticide resistance in Anopheles mosquitoes has been
observed in several regions of Africa
Chokwe District, Mozambique

17. Focuses on “…exploitation of the behavior and general
ecology of the mosquitoes to reduce contact with human
hosts…”
What it all comes down to:
C = Vectorial capacity, the number of infective bites received daily by a single host; m = Density of vectors in relation to
density of hosts; a = Proportion of vectors feeding on a host divided by the length of gonotrophic cycle in days; V = Vector
competence; P = Daily survival of vectors; n = Extrinsic incubation period
ma2VPn
-logeP
C =
WHO’s call for worldwide integrated efforts to prevent further
deterioration of the malaria situation

18. Chemoecological management of malaria mosquitoes

19. Curtesy of Prof. Laurence Zwiebel
Chemical cues play a significant role for mosquito behavior

20. Oviposition attractants Larval attractants
Host attractants
Main aim: identification of novel attractants that may be used in
integrated vector management of Anopheles mosquitoes

21. Multi-pronged, comparative, approach
Odor collection
Physiological analysis
Molecular analysis
Behavioral analysis

22. What we have achieved so far
• Improved efficacy of existing ’general’ mosquito lure
• Novel identicatication of attractants for
Culex quinquefasciatus, the major vector
of human filiariasis in Africa
• Identification of the first oviposition
attractant of Anopheles mosquitoes

23. What we have achieved so far

24. SLU
Richard Hopkins
Teun Dekker
Sharon Hill
Bonaventure Aman
Marcelo Lorenzo
Majid Ghaninia
Siju Purayil
Shahid Majeed
Acknowledgement:
Carl Tryggers Stiftelse för Vetenskaplig Forskning