Detection of enzootic circulation of a new strain of West Nile virus lineage 1 in sentinel chickens in the north of Tunisia.

Tunisia has experienced various West Nile disease outbreaks. Notwithstanding the serological and molecular confirmations in humans, horses and birds, the human surveillance system can still be improved. Three sentinel chicken flocks were placed in different Tunisian endemic regions and followed up from September 2016 to January 2017. A total of 422 sera from Sejnene (north of Tunisia), 392 from Moknine (east coast of Tunisia) and 386 from Tozeur (south of Tunisia) were tested for West Nile-specific antibodies and viral RNA. The WNV elisa positive rate in sentinel chickens in Sejnene was 10.7% (95% CI: 5.08-21.52). No positive samples were detected in Moknine. In Tozeur, the overall serological elisa positive rate during the study period was 9.8% (95% CI:4.35-21.03). West Nile virus nucleic acid was detected in two chickens in Sejnene.Phylogenetic analysis of one of the detected partial NS3 gene sequences showed that recent Tunisian WNV strain belong to WNV lineage 1 and is closely related to Italian strains detected in mosquitoes in 2016 and in a sparrow hawk in 2017. This report showed the circulation, first molecular detection and sequencing of WNV lineage 1 in chickens in the north of Tunisia and highlights the use of poultry as a surveillance tool to detect WNV transmission in a peri-domestic area.

Efficacy of vaccination for bluetongue virus serotype 8 performed shortly before challenge and implications for animal trade.

Vaccination is the most effective strategy for controlling Bluetongue virus (BTV) spread and economic consequences thereof. In this study we verified in sheep, using one commercially available inactivated vaccine for BTV-8 (BTVPUR AlSap 8), when, during the recommended vaccination schedule, animals start to be effectively protected against challenge with wild-type strain. To this aim, sheep were challenged at different time points shortly after the first vaccine injection. Twenty-four Sarda sheep were divided into four groups vaccinated two weeks before challenge (Group A), one week before challenge (Group B) and concurrently with challenge (Group C). A second vaccine was performed twenty-eight days later with respect the first vaccine administration in each experimental group. The last group consisted of six non vaccinated-infected animals (NVIA). Virological and serological examinations were performed before and after challenge up to 42 and 77days post challenge, respectively. The results of the study show that vaccination commenced as little as two weeks before challenge (Group A) prevented viremia and RNAemia in challenged sheep altogether. Conversely, Group B was partially protected from challenge and Group C showed viraemia and RNAemia similar to NVIA. This study indicates that the first administration of inactivated vaccine performed two weeks before challenge was able to prevent viraemia. Overall, our findings may have direct consequences for the management of an unexpected BTV-8 outbreak in sheep and for the legislation on sheep trade from BTV restriction areas.