Date Published: April 22, 2019
Publisher: Public Library of Science
Author(s): Akaninyene A. Otu, Ubong A. Udoh, Okokon I. Ita, Joseph Paul Hicks, William O. Egbe, John Walley, Peter M. Mugo.
In Nigeria, recent reports suggest that dengue viruses could be a major cause of acute fevers. We sought to make a cross-sectional estimate of the prevalence of current and previous dengue infections in patients presenting with fever to healthcare centres in Cross River State Nigeria.
This cross-sectional health facility survey recruited persons with temperature ≥38°C. Dengue virus immunoglobulin M (IgM)/immunoglobulin G (IgG) antibody testing using Onsite Duo dengue Ag-IgG/IgM lateral flow immunoassay cassettes was done. Samples which tested positive were further confirmed using the RecombiLISA dengue IgM and IgG enzyme linked immunosorbent assay kits and classified into primary and secondary dengue infection. Malaria testing was carried out using microscopy. Between 4 January 2017 and 24 August 2017 a total of 420 participants were sampled across 11 health centres. The mean age was 34 (range = 1–99), 63% were female, 49% reported sleeping under a treated mosquito net in the past week and 44% reported taking an antimalarial prior to seeking care. The mean number of days fever was present prior to seeking care was 8, and many of the participants presented with symptoms indicative of respiratory or urinary tract infections. Testing indicated that 6% (95% CI: 2, 13; n = 24) had either a primary or secondary dengue infection with or without co-existing malaria, while 4% (95% CI: 2, 9; n = 16) had either a primary or secondary dengue infection without co-existing malaria. 52% (95% CI: 46, 58; n = 218) had a malaria infection with or without any dengue infection, and 50% (95% CI: 44, 57; n = 210) had a malaria infection without any dengue infection.
Our study confirms the presence of dengue at not insignificant levels in patients attending health centres with fever in this south eastern province of Nigeria. These data highlight the danger of the common presumption in this setting that fever is due to malaria. Surveillance for dengue is vital in this setting.
Dengue is the most important arboviral infection of humans caused by four dengue virus serotypes, namely dengue virus 1,2,3, and 4 (DENV 1–4), which belong to the Flaviviridae family . On a global scale, the sharp increase in prevalence of dengue recorded in recent decades has caused it to be regarded as a major international public health concern. With an estimated annual incidence of 390 million cases , dengue poses a risk to 2.5–3.6 billion people  annually in over 125 endemic countries and has a case fatality rate exceeding 5% in some areas . The high morbidity and economic impact of dengue are well understood in many tropical countries across Asia and Latin America [5,6]. However, across Africa the burden of dengue remains very poorly documented, despite serologic evidence indicating DENV infections are present in several countries [7,8]. In Nigeria recent reports suggest that DENV could be a major cause of acute fevers , although many people presenting with fever to health facilities get treated with an antimalarial without confirmatory tests despite the overlap in symptoms between malaria and dengue. The dengue mosquito vectors (principally Aedes aegypti and Ae. albopictus) are known to be well established , and serologic evidence indicates the presence of DENV infections in some cities [1,10–13]. However, evidence on the prevalence of DENV infections in Nigeria from more robust and generalisable surveys is lacking.
A total of 11 health centres were sampled, with an additional health centre selected in one LGA due to a very low recruitment rate. Dates of patient recruitment varied across health centres. Across all health centres the earliest date of patient recruitment was 4 Jan 2017 and the latest was 24 Aug 2017. Across all health centres the range in the number of days between first and final patient recruitment dates was 0–232 (median = 97).There was also a large amount of variation in the number of patients recruited per facility, with a median sample size of 34 and a range of 2-96.There were a total of 420 participants with a mean age of 35 and 63% being female(Table 1).Twenty-six percent (26%) had university education, while 17% had not received any formal education. Fifty-nine (59%) resided in a rural area, with the mean household size being 5. Most (90%) participants lived in houses roofed with sheet metal. 46% had waste around their homes, but 86% also indicated that they practiced some form of environmental management to keep waste down to a minimum. Forty-nine (49%) reported sleeping under a mosquito net during the previous week (Table 2). The use of mosquito nets on doorways and windows was a common practice (65%). The use of antimalarials prior to presentation at a healthcare facility was also frequently reported (44%). The average axillary temperature among participants was 38°C, and the mean duration of fever was 8 days. Many of the participants presented with symptoms indicative of urinary tract and respiratory infections, namely dysuria, cough/coryza, breathlessness and sore throats (Table 1).
We found that 6% of patients tested positive for primary or secondary DENV infections either with or without a malaria co-infection. In these undifferentiated fever cases 50% tested positive for malaria but not dengue, while just 2% had co-existing primary dengue and malaria infections (and none had secondary dengue and malaria positivity).Symptoms indicative of urinary tract and respiratory infections were commonplace among this cohort and may account for some proportion of the fevers experienced. Dengue seroprevalence from a survey done in Maiduguri  Northern Nigeria was 10.1% (testing specifically for DEN V 3 using a microneutralization assay) and was 17.2% in Ogbomoso , South Western Nigeria (testing for dengue IgM using ELISA). However, these studies used a one-stage testing for dengue antibodies using microneutralization and ELISA respectively. To the best of our knowledge, this is the first survey of dengue seroprevalence from any setting in the South Eastern part of Nigeria.