STORIES

Expert view to prevent a Dengue outbreak in Cameroon – Dr. Basile Kamgang

Dengue is the main Aedes-borne viral diseases with nearly 390 million annual dengue infections and 96 million (67–136 million) clinical cases [1]. This disease is caused by the dengue virus (DENV1, DENV2, DENV3, and DENV4) belonging to the Flavivirus genus. The dengue virus is transmitted to humans by a bite of an infected Aedes mosquito notably Ae. aegypti and Ae. albopictus.  Dengue was previously considered as scarce in Africa in general probably due to the under-diagnosis and the similar symptoms with malaria which is endemic in the region.

Symptoms

It will be interesting to highlight that the common symptoms of dengue are  fever, severe headaches, pain behind the eyes, severe joint and muscle pain, fatigue, nausea, and vomiting.

Outbreaks and Occurrences

However, during the two last decades there has been a rise in dengue cases reported in Cameroon [2-7] suggesting the modification of epidemiology of this disease. Coincidentally, the emergence of this virus in urban areas in Cameroon matches the introduction of Ae. albopictus in the country. Aedes albopictus is an invasive species which originates from south East Asia and was reported for the first time in Cameroon circa 2000 [8] while Ae. aegypti is indigenous in Africa and documented in Cameroon since 1950. You should know, there is no efficient vaccine and specific treatment against dengue, vector control remains the cornerstone to prevent and control outbreaks.

Our works at the Centre for Research in Infectious Diseases (CRID) about dengue virus is to characterise dengue vectors and establish the entomological risks of outbreak occurrence. Drawing from our work, we demonstrate that Ae. aegypti is present across Cameroon while Ae. albopictus has a distribution limited in the southern part of the country [9] suggesting a climate limitation of invasion of this species in the North.

Our research also demonstrates that both species breed mainly in discarded tanks and used tyres in Cameroon as in other Central African countries [10, 11]. Having assessed the ability of Ae. aegypti and Ae. albopictus collected in different ecological settings in Cameroon, our analysis showed that Ae. aegypti can easily transmit dengue in areas where both species are found. However, in the North notably in Maroua and Benoue, Ae. aegypti populations were found resistant to dengue transmission [12]. Our data revealed the variable level of susceptibility according to the population origin and insecticides tested except to organophosphates (temephos and fenithrotion) which were fully susceptible [13]. These data are relevant to plan arbovirus vector control programmes in Cameroon which is currently lacking and help in facilitating further works.

 It is important to draw the attention of the Ministry of Public Health to the fact that the entomological risk of outbreak occurrence is real and it has become urgent to set up a programme to fight against abovirus vectors in Cameroon.  

And to the population, while waiting for an arbovirus vector control programme to be put in place, it is important to take action by elimiating every container that is no longer in use as well as get rid of used tires. This will greatly help reduce the ovipositing sites of Aedes and therefore reduce the density of adult mosquitoes.

1.       Bhatt S, Gething PW, Brady OJ, Messina JP, Farlow AW, Moyes CL, Drake JM, Brownstein JS, Hoen AG, Sankoh O et al: The global distribution and burden of dengue. Nature 2013, 496(7446):504-507.

2.      Ndip LM, Bouyer DH, Travassos Da Rosa AP, Titanji VP, Tesh RB, Walker DH: Acute spotted fever rickettsiosis among febrile patients, Cameroon. Emerging infectious diseases 2004, 10(3):432-437.

3.      Kuniholm MH, Wolfe ND, Huang CY, Mpoudi-Ngole E, Tamoufe U, LeBreton M, Burke DS, Gubler DJ: Seroprevalence and distribution of Flaviviridae, Togaviridae, and Bunyaviridae arboviral infections in rural Cameroonian adults. The American journal of tropical medicine and hygiene 2006, 74(6):1078-1083.

4.      Yousseu FBS, Nemg FBS, Ngouanet SA, Mekanda FMO, Demanou M: Detection and serotyping of dengue viruses in febrile patients consulting at the New-Bell District Hospital in Douala, Cameroon. PloS one 2018, 13(10):e0204143.

5.       Nemg Simo FB, Sado Yousseu FB, Evouna Mbarga A, Bigna JJ, Melong A, Ntoude A, Kamgang B, Bouyne R, Moundipa Fewou P, Demanou M: Investigation of an Outbreak of Dengue Virus Serotype 1 in a Rural Area of Kribi, South Cameroon: A Cross-Sectional Study. Intervirology 2018, 61(6):265-271.

6.      Monamele GC, Demanou M: First documented evidence of dengue and malaria co-infection in children attending two health centers in Yaounde, Cameroon. The Pan African medical journal 2018, 29:227.

7.       Demanou M, Pouillot R, Grandadam M, Boisier P, Kamgang B, Herve JP, Rogier C, Rousset D, Paupy C: Evidence of dengue virus transmission and factors associated with the presence of anti-dengue virus antibodies in humans in three major towns in Cameroon. PLoS neglected tropical diseases 2014, 8(7):e2950.

8.      Fontenille D, Toto JC: Aedes (Stegomyia) albopictus (Skuse), a potential new Dengue vector in southern Cameroon. Emerging infectious diseases 2001, 7(6):1066-1067.

9.      Tedjou AN, Kamgang B, Yougang AP, Njiokou F, Wondji CS: Update on the geographical distribution and prevalence of Aedes aegypti and Aedes albopictus (Diptera: Culicidae), two major arbovirus vectors in Cameroon. PLoS neglected tropical diseases 2019, 13(3):e0007137.

10.     Tedjou AN, Kamgang B, Yougang AP, Wilson-Bahun TA, Njiokou F, Wondji CS: Patterns of Ecological Adaptation of Aedes aegypti and Aedes albopictus and Stegomyia Indices Highlight the Potential Risk of Arbovirus Transmission in Yaoundé, the Capital City of Cameroon. Pathogens 2020, 9(6):491.

11.     Kamgang B, Ngoagouni C, Manirakiza A, Nakoune E, Paupy C, Kazanji M: Temporal patterns of abundance of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) and mitochondrial DNA analysis of Ae. albopictus in the Central African Republic. PLoS neglected tropical diseases 2013, 7(12):e2590.

12.     Kamgang B, Vazeille M, Tedjou AN, Wilson-Bahun TA, Yougang AP, Mousson L, Wondji C, Failloux A-B: Risk of dengue in Central Africa: Vector competence studies with Aedes aegypti and Aedes albopictus (Diptera: Culicidae) populations and dengue 2 virus. PLoS neglected tropical diseases 2019, 13(12):e0007985.

13.     Yougang AP, Kamgang B, Tedjou AN, Wilson-Bahun TA, Njiokou F, Wondji CS: Nationwide profiling of insecticide resistance in Aedes albopictus (Diptera: Culicidae) in Cameroon. PloS one 2020, 15(6):e0234572.

STORIES

Fighting Malaria in Africa, a CRID perspective

Mosquittoes in Africa: expert research and recommendations to National Malaria Control Programmes – Dr. NDO Cyrille, Vector Biologist, Head of Parasitology and Microbiology Department at CRID

Mosquittoes in Africa: expert research and recommendations to National Malaria Control Programmes – Dr. NDO Cyrille, Vector Biologist, Head of Parasitology and Microbiology Department at CRID

Africa has over 10 indigenous Anopheles species with ability to transmit Plasmodium parasites that cause malaria [2, 3]. Therefore, control of these vector species is the pillar of prevention strategies. Vector control relies extensively on the use of pyrethroid-based insecticide-treated bed nets or indoor residual spraying. Mosquitoes have however developed resistance against the insecticides actually in use. More so, in some settings, it has been noticed that instead of biting indoor (as people are protected by bed net), some mosquito populations have developed a new tendency of biting outdoor in the early hours of the day when people are not protected by the bed net. This high insecticide resistance profile (and associated change in biting behaviour) is a major challenge to the efforts of National Malaria Control Programmes in fighting the killer disease [4, 5].

The Centre for Research in Infectious Diseases (CRID) has over the years sort to understand the challenges in the fight against malaria vectors, and to find ways to improve the efficacy of current vector control tools. Drawing from studies conducted in Central, West and  East Africa, cases of high resistance levels to insecticides in major malaria vectors leading to loss of efficacy of Long Lasting Insecticidal Nets (LLINs) have been reported [6-13].

 In order to improve malaria control and a possible disease elimination which is backed in the agenda [14], there is an urgent need to first preserve the optimal efficacy of existing vector control tools. We advise National Malaria Control Programmes to conduct routine entomological surveillance for determination of insecticide resistance profile and mechanisms in vector populations, using standard WHO bioassays protocols, but also molecular techniques that can allow early detection of target site [15, 16] and metabolic-mediated resistance [6, 11, 17]. Availability of these data will help to better design resistance management strategies, and to implement evidence-based and integrated vector control.

Meanwhile researchers at the CRID are working, in collaboration with the broad malaria research community,  in  indentifying new insecticides with different mode of action and/or in developing alternative vector control tools such as the sterile insect technique [18, 19].

References

1.   WHO: World Malaria Report 2019. WHO Global Malaria Programme. World Health Organiszation https://wwwwhoint/publications-detail/world-malaria-report-2019.

2.   Fontenille D, Cohuet A, Awono-Ambene PH, Antonio-Nkondjio C, Wondji C, Kengne P, Dia I, Boccolini D, Duchemin JB, Rajaonarivelo V et al: [Systematics and biology of Anopheles vectors of Plasmodium in Africa, recent data]. Med Trop (Mars) 2003, 63(3):247-253.

3.   Antonio-Nkondjio C, Kerah CH, Simard F, Awono-Ambene P, Chouaibou M, Tchuinkam T, Fontenille D: Complexity of the malaria vectorial system in Cameroon: contribution of secondary vectors to malaria transmission. J Med Entomol 2006, 43(6):1215-1221.

4.   Benelli G, Beier JC: Current vector control challenges in the fight against malaria. Acta Trop 2017, 174:91-96.

5.   Sougoufara S, Doucoure S, Backe Sembene PM, Harry M, Sokhna C: Challenges for malaria vector control in sub-Saharan Africa: Resistance and behavioral adaptations in Anopheles populations. J Vector Borne Dis 2017, 54(1):4-15.

6.   Weedall GD, Mugenzi LMJ, Menze BD, Tchouakui M, Ibrahim SS, Amvongo-Adjia N, Irving H, Wondji MJ, Tchoupo M, Djouaka R et al: A cytochrome P450 allele confers pyrethroid resistance on a major African malaria vector, reducing insecticide-treated bednet efficacy. Sci Transl Med 2019, 11(484).

7.   Tchigossou G, Djouaka R, Akoton R, Riveron JM, Irving H, Atoyebi S, Moutairou K, Yessoufou A, Wondji CS: Molecular basis of permethrin and DDT resistance in an Anopheles funestus population from Benin. Parasit Vectors 2018, 11(1):602.

8.  Kamgang B, Tchapga W, Ngoagouni C, Sangbakembi-Ngounou C, Wondji M, Riveron JM, Wondji CS: Exploring insecticide resistance mechanisms in three major malaria vectors from Bangui in Central African Republic. Pathog Glob Health 2018, 112(7):349-359.

9.   Riveron JM, Watsenga F, Irving H, Irish SR, Wondji CS: High Plasmodium Infection Rate and Reduced Bed Net Efficacy in Multiple Insecticide-Resistant Malaria Vectors in Kinshasa, Democratic Republic of Congo. J Infect Dis 2018, 217(2):320-328.

10. Ibrahim SS, Fadel AN, Tchouakui M, Terence E, Wondji MJ, Tchoupo M, Kerah-Hinzoumbe C, Wanji S, Wondji CS: High insecticide resistance in the major malaria vector Anopheles coluzzii in Chad Republic. Infect Dis Poverty 2019, 8(1):100.

11. Mugenzi LMJ, Menze BD, Tchouakui M, Wondji MJ, Irving H, Tchoupo M, Hearn J, Weedall GD, Riveron JM, Wondji CS: Cis-regulatory CYP6P9b P450 variants associated with loss of insecticide-treated bed net efficacy against Anopheles funestus. Nat Commun 2019, 10(1):4652.

12. Ibrahim SS, Mukhtar MM, Irving H, Labbo R, Kusimo MO, Mahamadou I, Wondji CS: High Plasmodium infection and multiple insecticide resistance in a major malaria vector Anopheles coluzzii from Sahel of Niger Republic. Malar J 2019, 18(1):181.

13. Riveron JM, Huijben S, Tchapga W, Tchouakui M, Wondji MJ, Tchoupo M, Irving H, Cuamba N, Maquina M, Paaijmans K et al: Escalation of Pyrethroid Resistance in the Malaria Vector Anopheles funestus Induces a Loss of Efficacy of Piperonyl Butoxide-Based Insecticide-Treated Nets in Mozambique. J Infect Dis 2019, 220(3):467-475.

14. Rabinovich RN, Drakeley C, Djimde AA, Hall BF, Hay SI, Hemingway J, Kaslow DC, Noor A, Okumu F, Steketee R et al: malERA: An updated research agenda for malaria elimination and eradication. PLoS Med 2017, 14(11):e1002456.

15. Nwane P, Etang J, Chouasmall yi UM, Toto JC, Mimpfoundi R, Simard F: Kdr-based insecticide resistance in Anopheles gambiae s.s populations in. BMC Res Notes 2011, 4:463.

16. Djogbenou L, Weill M, Hougard JM, Raymond M, Akogbeto M, Chandre F: Characterization of insensitive acetylcholinesterase (ace-1R) in Anopheles gambiae (Diptera: Culicidae): resistance levels and dominance. J Med Entomol 2007, 44(5):805-810.

17. Riveron JM, Yunta C, Ibrahim SS, Djouaka R, Irving H, Menze BD, Ismail HM, Hemingway J, Ranson H, Albert A et al: A single mutation in the GSTe2 gene allows tracking of metabolically based insecticide resistance in a major malaria vector. Genome Biol 2014, 15(2):R27.

18. Lobo NF, Achee NL, Greico J, Collins FH: Modern Vector Control. Cold Spring Harb Perspect Med 2018, 8(1).

19. Ndo C, Poumachu Y, Metitsi D, Awono-Ambene HP, Tchuinkam T, Gilles JLR, Bourtzis K: Isolation and characterization of a temperature-sensitive lethal strain of Anopheles arabiensis for SIT-based application. Parasit Vectors 2018, 11(Suppl 2):659.

STORIES

Prof Charles Wondji in conversation with MESA Alliance

The Executive Director of CRID and Professor of Genetics at the Liverpool School of Tropical Medicine Prof Charles Wondji, on May 26, was in conversation with the MESA Alliance, a living database which captures research projects and institutions’ portfolios in malaria elimination and eradication.

The conversation with Professor Charles Wondji focused on Genetic and genomic tools to fight vector-borne diseases where he reveals in depth the importance of genetic epidemiology research in malaria surveillance and control, how genetic epidemiology can facilitate the management of insecticide resistance in Africa, how it can improve the operational decisions made by National Malaria Control Programmes, challenges researchers are faced with and the necessary steps that the malaria community could take in order to advance towards malaria elimination.

Find and read complete interview here http://www.mesamalaria.org/updates/genetic-and-genomic-tools-fight-vector-borne-diseases-conversation-prof-charles-wondji