A four-year survey (2011–2014) of West Nile virus infection in humans, mosquitoes and birds, including the 2012 meningoencephalitis outbreak in Tunisia

Abir Monastiri,Badereddine Mechri,Ana Vázquez-González,Meriadeg Ar Gouilh,Mohamed Chakroun,Chawki Loussaief,Maha Mastouri,Najet Dimassi,Lamjed Boughzala,Mahjoub Aouni,Jordi Serra-Cobo

doi:10.1038/s41426-018-0028-y

Abstract

A West Nile virus (WNV) outbreak occurred in Tunisia between mid-July and December 2012. To assess the epidemiological features of the WNV transmission cycle, human cerebrospinal fluid samples from patients with suspected cases (n = 79), Culex pipiens mosquitoes (n = 583) and serum specimens from domestic and migratory birds (n = 70) were collected for 4 years (2011–2014) in the Tunisian Sahel region. Viral testing was performed by polymerase chain reaction (PCR). The WNV genome was detected in 7 patients (8.8%), 4 Culex pipiens pools, and a domestic mallard (Anas platyrhynchos). All PCR-positive samples were from the Monastir region. Phylogenetic analysis revealed that two different WNV strain groups circulated, and isolates from the reservoir (bird), vector (Culex pipiens), and dead-end hosts (humans) were closely related. The Monastir region is a hot-spot for WNV infection, and the reiterative presence of WNV over the years has increased the risk of viral reemergence in Tunisia, which highlights the need for more enhanced and effective WNV surveillance in humans with public awareness campaigns strengthened by monitoring mosquitoes and maintaining avian surveillance for early detection of WNV circulation.

Highlights

Introduction The WestNile virus (WNV) is an arthropod-borne virus of the Flaviviridae family, genus Flavivirus, belonging to the Japanese encephalitis serocomplex and has a complex life cycle, involving several bird species as primary hosts, mosquitoes as primary vectors and humans, and horses as incidental or dead-end hosts[1,2]
Patient clinical characteristics and West Nile virus (WNV) detection Seventy-nine patients (48 males and 31 females) from 22 localities in the Tunisian Sahel region were admitted to Fattouma Bourguiba University Hospital of Monastir (Tunisia) and distributed as follows: 19 infants (24%), 18 children (23%), 36 adults (45%), and 6 elderly patients (8%) (Table 1)
Among the 25 mosquito pools tested for WNV RNA, 4 pools sampled in 4 localities (Khniss, Agba, MoôtmarSahline, Oued Khniss) in the Monastir region were positive by polymerase chain reaction (PCR) (Fig. 1)

Summary

Introduction

Introduction The WestNile virus (WNV) is an arthropod-borne virus of the Flaviviridae family, genus Flavivirus, belonging to the Japanese encephalitis serocomplex and has a complex life cycle, involving several bird species as primary hosts, mosquitoes as primary vectors and humans, and horses as incidental or dead-end hosts[1,2]. In Tunisia, WNV caused three major human epidemics with fatalities and severe central nervous system diseases, such as meningitis and encephalitis, which occurred in 199710,11, 20035,12, and more recently in 20126, with sporadic cases recorded. The WNV strains identified during 1997 and 2003 human outbreaks belonged to lineage 1a and were closely related to the Israeli-American cluster[5,11,15]. WNV is thought to be endemic/enzootic in Tunisia, as shown by several serological studies performed in humans[16,17,18], wild birds[19], and other mammals[20,21,22,23]. WNV has been detected in mosquitoes from Central Tunisia[24]

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