Spatial and Temporal Patterns of Dengue Transmission along a Red Sea Coastline: A Longitudinal Entomological and Serological Survey in Port Sudan City

Abstract

BackgroundDengue is an emerging health problem in several coastlines along the Red Sea. The objective of the present work is to elucidate spatial and temporal patterns of dengue transmission in Port Sudan.Methods/FindingsA longitudinal study with three cross-sectional surveys was carried out in upper, middle and lower class neighborhoods, from November 2008 to October 2009. Monthly, entomological surveys were followed by serological surveys in dengue vector-positive houses. Meteorological records were obtained from two weather stations in the city during the same time. Overall, 2825 houses were inspected. Aedes aegypti represented 65% (35,714/54,944) and 68% (2526/3715) of the collected larvae and pupae, respectively. Out of 4640 drinking water containers, 2297 were positive for Ae. aegypti. Clay-pots “Zeirr” followed by plastic barrels were key productive containers for pupae of dengue vector, 63% (n = 3959) and 26% (n = 1651), respectively. A total of 791 blood samples were tested using PanBio Capture/Indirect IgM ELISA. Overall, the sero-prevalence rate of dengue ranged between 3%–8% (41/791), compared to an incidence of 29–40 new cases per 10,000 (193/54886) in the same examined population. Lower and middle class neighborhoods had higher entomological indices compared with upper class ones (p<0.001). Although, dengue incidence rate was significantly lower in the middle and lower class neighborhoods (F = 73.97, d.f. = 2, p<0.001), no difference in IgM prevalence was shown. The city is subject to two transmission peaks in the winter (i.e. November–January), and summer (i.e. June–August). The serological peaks of dengue are preceded by entomological peaks that occur before the onset of winter (November) and summer (March) respectively.ConclusionDengue incidence is heterogeneously distributed across the neighborhoods of Port Sudan and exhibits a bi-cyclic intra-annual pattern. Hence, it should be feasible to carry out timely vector control measures to prevent or reduce dengue transmission.

Dengue vector control and surveillance during a major outbreak in a coastal Red Sea area in Sudan

“…Selection of vector control interventions was based on findings of research work carried out in 2008-2009 [3]. In addition, a preliminary survey was carried out at the beginning of the outbreak in March 2010.…”

“…The city is subject to 2 transmission peaks: a winter peak and another major one during summer [3]. Most of the dengue outbreaks in Port Sudan occurred during summer peak (Ministry of Health, personal communication).…”

“…Worldwide, an estimated 2.5 billion people are at risk of infection, approximately 1 billion live in urban areas in tropical and sub-tropical countries in South-East Asia, the Western Pacific and the American regions of the World Health Organization (WHO) [1]. In the WHO Eastern Mediterranean Region, dengue is an emerging health problem in several countries such as Djibouti, Pakistan, Saudi Arabia, Somalia, Sudan and Yemen [2,3].…”

“…Three serotypes of the virus (DENV1, DENV2 and DEN3) are known to circulate [5,6], and infestations of Aedes aegypti, the mosquito vector, have been documented in the area [3]; this is linked to the limited drinking-water and consequent water storage habits of the local community [7]. A lack of an efficient surveillance system has resulted in delayed response to these outbreaks.…”

“…An unprecedented dengue outbreak started in January 2010 in Port Sudan [3]. In this report, we describe how vector control and surveillance were promoted and incorporated in the response plan to the outbreak, and the operational outcomes in terms of evaluation of vector control interventions and the monitoring of the course of the outbreak.…”