Emerging vector-borne diseases in dromedaries in Tunisia: West Nile, bluetongue, epizootic haemorrhagic disease and Rift Valley fever

Abstract

A total of 118 sera were collected during 2016 from two groups of dromedaries from Kebili and Medenine governorates in the south of Tunisia. The aim of this study was to provide the first serological investigation of four emerging vector-borne diseases in two groups of dromedaries in Tunisia. Sera were tested by ELISA and serum neutralisation test to identify West Nile virus (WNV), bluetongue virus (BTV), epizootic haemorrhagic disease virus (EHDV) and Rift Valley fever virus (RVFV). In the first group, the seroprevalence for BTV was 4.6%, while in the second group, it was 25.8% for WNV and 9.7% for BTV. Only serotype 1 was detected for BTV in the two groups. No evidence for circulation of RVF and EHD viruses was revealed. Results indicated that dromedaries can be infected with BTV and WNV, suggesting that this species might play a significant role in the epizootiology of these viral diseases in Tunisia and neighbouring countries.

Risk based serological survey of Rift Valley fever in Tunisia (2017–2018)

“…In 2017, Ben Hassine et al. did not find any RVF seropositive samples in camels (n = 118) in the southern region of Tunisia [ 20 ]. However, a serological survey carried out in the summer of 2014 in the governorates of Sousse, Sfax and Mahdia (east-central Tunisia) indicated that among the 181 sera of human patients suffering from a febrile episode, 14 were RVF IgM positive.…”

“…In Tunisia, a serological survey was carried out in 2014 in the Centre of Tunisia (governorates of Sfax, Mahdia and Sousse) and revealed the presence of RVF specific IgG antibodies in human samples despite their absence in samples from febrile patients and slaughterhouse workers [ 19 ]. Additional RVF focused seroprevalence studies conducted on animal samples such as dromedaries in 2017 [ 20 ], goats and sheep in 2006–2007 [ 21 ] did not confirm active circulation of RVF in Tunisia. However, a study by Selmi et al.…”

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

“…During the summer-autumn of 2012, a WNV infection outbreak occurred in Tunisia after an apparent silent period following the 2003 epidemic, although epidemiological and clinical surveys have demonstrated WNV circulation in humans 5 , 10 – 12 , as well as in mosquitoes 24 , and seropositivity has been reported in equids 20 – 22 , dromedaries 23 , and wild birds 19 in the years since the first WNV epidemic in 1997. However, to date, no information on the epidemiological characteristics of the WNV transmission cycle in the Tunisian Sahel region has been available.…”

“…pipiens during the 2014 transmission season suggesting WNV persistence in the country 24 . More studies are needed regarding vector competence and overwintering cycles in mosquitoes, local birds and potential non-avian reservoirs 23 as an endemization mechanism in Tunisia.…”

“…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 – 18 , wild birds 19 , and other mammals 20 – 23 . Furthermore, WNV has been detected in mosquitoes from Central Tunisia 24 .…”