Evidence of Dengue Virus Transmission and Factors Associated with the Presence of Anti-Dengue Virus Antibodies in Humans in Three Major Towns in Cameroon

Abstract

BackgroundDengue is not well documented in Africa. In Cameroon, data are scarce, but dengue infection has been confirmed in humans. We conducted a study to document risk factors associated with anti-dengue virus Immunoglobulin G seropositivity in humans in three major towns in Cameroon.Methodology/Principal FindingsA cross sectional survey was conducted in Douala, Garoua and Yaounde, using a random cluster sampling design. Participants underwent a standardized interview and were blood sampled. Environmental and housing characteristics were recorded. Randomized houses were prospected to record all water containers, and immature stages of Aedes mosquitoes were collected. Sera were screened for anti-dengue virus IgG and IgM antibodies. Risk factors of seropositivity were tested using logistic regression methods with random effects.Anti-dengue IgG were found from 61.4% of sera in Douala (n = 699), 24.2% in Garoua (n = 728) and 9.8% in Yaounde (n = 603). IgM were found from 0.3% of Douala samples, 0.1% of Garoua samples and 0.0% of Yaounde samples. Seroneutralization on randomly selected IgG positive sera showed that 72% (n = 100) in Douala, 80% (n = 94) in Garoua and 77% (n = 66) in Yaounde had antibodies specific for dengue virus serotype 2 (DENV-2).Age, temporary house walls materials, having water-storage containers, old tires or toilets in the yard, having no TV, having no air conditioning and having travelled at least once outside the city were independently associated with anti-dengue IgG positivity in Douala. Age, having uncovered water containers, having no TV, not being born in Garoua and not breeding pigs were significant risk factors in Garoua. Recent history of malaria, having banana trees and stagnant water in the yard were independent risk factors in Yaounde.Conclusion/SignificanceIn this survey, most identified risk factors of dengue were related to housing conditions. Poverty and underdevelopment are central to the dengue epidemiology in Cameroon.

Investigation of an Outbreak of Dengue Virus Serotype 1 in a Rural Area of Kribi, South Cameroon: A Cross-Sectional Study

“…Our results confirm, however, that DENVs circulates in Cameroon as previously described [9], and that dengue 1 is re-emerging in Kribi as the first confirmed case was described in this city in 2000 [18]. The frequency of 3.3% anti-dengue IgM observed is significantly higher than that obtained in other cities in Cameroon during serosurveys; 0.3% IgM in Douala and 0.1% in Garoua by Demanou et al [8] in 2006/2007. This result shows that the Londji health area could have characteristics favorable of the spread of DENV 1, as well as the presence of Aedes mosquito, immunocompromised human groups, continuous introduction and/or circulation of one or more serotypes, some environmental parameters (temperature and precipitation affect the demography and behavior of Aedes vectors), international travel, poverty, and lack of sustained programs at various levels.…”

“…We found 14.3% acute dengue infection with 10.9% detected by real-time RT-PCR and 3.3% by MAC ELISA. These findings extend those of Demanou et al [8] who reported a seroprevalence of 0.3% in Douala and 0.1% in Garoua for dengue in 2011, confirming that DENV is circulating in Cameroon. The frequency of dengue detection obtained in this work is similar to the one obtained by Beckett et al [15] working on the early detection of dengue using 785 cluster volunteers around index cases, who found that 11 and 2 DENV cases by RT-PCR, respectively, in febrile and asymptomatic participants showing the first documentation of asymptomatic viremia in naturally acquired human dengue infections.…”

“…The frequency of dengue detection obtained in this work is similar to the one obtained by Beckett et al [15] working on the early detection of dengue using 785 cluster volunteers around index cases, who found that 11 and 2 DENV cases by RT-PCR, respectively, in febrile and asymptomatic participants showing the first documentation of asymptomatic viremia in naturally acquired human dengue infections. However, other studies have found a low prevalence of dengue serotype 1, 2, 3, and 4 in other regions of Cameroon but not during a period of outbreak [7, 8]. The low positivity rate may be due to the fact that the peak of the epidemic had already passed or that the samples were collected during a short period (21–25 June, 2017) in contrast with previous studies in which the data were collected during a period of 3 years [16].…”

“…Plasma was separated from whole blood by centrifugation and tested for IgM antibodies against DENV using an “in-house” adapted technique, IgM antibody capture enzyme-linked immunosorbent assay (MAC-ELISA), as described elsewhere [8]. DENV RNA was detected using the CDC real-time Trioplex RT-PCR kit.…”

“…Another serosurvey on 2,030 participants carried out in 2006/2007 in three major cities of Cameroon (Douala, Yaoundé, and Garoua) showed an anti-dengue antibody IgG prevalence of 61.4% in Douala; 24.2% in Garoua, and 9.8% in Yaoundé. Seroneutralization tests showed that only DENV serotypes 1 and 2 were present, DENV-2 being predominant with a 72–80% prevalence depending on the city [8]. Another study conducted several years later in the South-West region of Cameroon reported a seroprevalence of 5.1% for DENV-2 antibody IgG and 2.5% for anti-DENV-1 IgG antibody in 102 sera [9].…”