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.