Rift Valley fever virus modulates apoptosis and immune response during infection of human astrocytes.

Rift Valley fever (RVF) is an arboviral disease of zoonotic origin that causes recurrent epidemics in Africa, the Arabic Peninsula, and islands of the South West of the Indian Ocean. RVF occurs mainly in livestock but also affects humans with severe clinical manifestations, including neurological disorders. However, human neuropathogenesis of Rift Valley fever virus (RVFV) is still poorly characterized. To study the interactions between RVFV and the central nervous system (CNS), we focused on RVFV infection of astrocytes, the major glial cells of the CNS that have several supporting roles including immune response regulation. We confirmed the permissiveness of astrocytes to RVFV infection and highlighted a strain-dependent infectivity. We showed that RVFV infection of astrocytes induced cell apoptosis and observed that the RVFV Non-Structural protein NSs, a known virulence factor, potentially delayed apoptosis by sequestrating activated-caspase 3 in the nucleus. Our study also showed that RVFV-infected astrocytes upregulated expression of genes associated with inflammatory and type I interferon responses at the mRNA level, but not at the protein level. This inhibition of immune response is potentially due to a NSs-dependent mechanism of mRNA nuclear export inhibition. Together, these results highlighted the direct impact of RVFV infection on the human CNS through the induction of apoptosis and a possible inhibition of early-onset immune responses that are crucial for the host survival.

External quality assessment of Rift Valley fever diagnosis in countries at risk of the disease: African, Indian Ocean and Middle-East regions.

Rift Valley fever virus (RVFV), an arbovirus belonging to the Phlebovirus genus of the Phenuiviridae family, causes the zoonotic and mosquito-borne RVF. The virus, which primarily affects livestock (ruminants and camels) and humans, is at the origin of recent major outbreaks across the African continent (Mauritania, Libya, Sudan), and in the South-Western Indian Ocean (SWIO) islands (Mayotte). In order to be better prepared for upcoming outbreaks, to predict its introduction in RVFV unscathed countries, and to run efficient surveillance programmes, the priority is harmonising and improving the diagnostic capacity of endemic countries and/or countries considered to be at risk of RVF. A serological inter-laboratory proficiency test (PT) was implemented to assess the capacity of veterinary laboratories to detect antibodies against RVFV. A total of 18 laboratories in 13 countries in the Middle East, North Africa, South Africa, and the Indian Ocean participated in the initiative. Two commercial kits and two in-house serological assays for the detection of RVFV specific IgG antibodies were tested. Sixteen of the 18 participating laboratories (88.9%) used commercial kits, the analytical performance of test sensitivity and specificity based on the seroneutralisation test considered as the reference was 100%. The results obtained by the laboratories which used the in-house assay were correct in only one of the two criteria (either sensitivity or specificity). In conclusion, most of the laboratories performed well in detecting RVFV specific IgG antibodies and can therefore be considered to be prepared. Three laboratories in three countries need to improve their detection capacities. Our study demonstrates the importance of conducting regular proficiency tests to evaluate the level of preparedness of countries and of building a network of competent laboratories in terms of laboratory diagnosis to better face future emerging diseases in emergency conditions.

Crimean-Congo Hemorrhagic Fever Virus Antibodies among Livestock on Corsica, France, 2014-2016.

We conducted a serologic survey for Crimean-Congo hemorrhagic fever virus antibodies in livestock (cattle, sheep, and goats; N = 3,890) on Corsica (island of France) during 2014-2016. Overall, 9.1% of animals were seropositive, suggesting this virus circulates on Corsica. However, virus identification is needed to confirm these results.

Development and validation of a pen side test for Rift Valley fever.

BACKGROUND: Rift Valley fever (RVF) is one of the main vector borne zoonotic diseases that affects a wide range of ruminants and human beings in Africa and the Arabian Peninsula. A rapid and specific test for RVF diagnosis at the site of a suspected outbreak is crucial for the implementation of control measures. METHODOLOGY/PRINCIPAL FINDINGS: A first-line lateral flow immunochromatographic strip test (LFT) was developed for the detection of the nucleoprotein (N) of the RVF virus (RVFV). Its diagnostic performance characteristics were evaluated using reference stocks isolates recovered from different hosts and in geographic regions mimicking clinical specimens and from known RVF negative serum samples. A high level of diagnostic accuracy (DSe (35/35), DSp (167/169)) was observed, including the absence of cross-reactivity with viruses belonging to different genera. CONCLUSION/SIGNIFICANCE: The fact no specialized reagents and laboratory equipment are needed, make this assay a valuable, first-line diagnostic tool in resource-poor diagnostic territories for on-site RVFV detection, however the staff require training.

Towards the PCR-based identification of Palaearctic Culicoides biting midges (Diptera: Ceratopogonidae): results from an international ring trial targeting four species of the subgenus Avaritia.

BACKGROUND: Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are biological vectors of internationally important arboviruses. To understand the role of Culicoides in the transmission of these viruses, it is essential to correctly identify the species involved. Within the western Palaearctic region, the main suspected vector species, C. obsoletus, C. scoticus, C. dewulfi and C. chiopterus, have similar wing patterns, which makes it difficult to separate and identify them correctly. METHODS: In this study, designed as an inter-laboratory ring trial with twelve partners from Europe and North Africa, we assess four PCR-based assays which are used routinely to differentiate the four species of Culicoides listed above. The assays based on mitochondrial or ribosomal DNA or microarray hybridisation were tested using aliquots of Culicoides DNA (extracted using commercial kits), crude lysates of ground specimens and whole Culicoides (265 individuals), and non-Culicoides Ceratopogonidae (13 individuals) collected from across Europe. RESULTS: A total of 800 molecular assays were implemented. The in-house assays functioned effectively, although specificity and sensitivity varied according to the molecular marker and DNA extraction method used. The Obsoletus group specificity was overall high (95-99%) while the sensitivity varied greatly (59.6-100%). DNA extraction methods impacted the sensitivity of the assays as well as the type of sample used as template for the DNA extraction. CONCLUSIONS: The results are discussed in terms of current use of species diagnostic assays and the future development of molecular tools for the rapid differentiation of cryptic Culicoides species.

Prevalence of Rift Valley Fever among ruminants, Mayotte.

Rift Valley fever threatens human and animal health. After a human case was confirmed in Comoros in 2007, 4 serosurveys among ruminants in Mayotte suggested that Rift Valley fever virus had been circulating at low levels since 2004, although no clinical cases occurred in animals. Entomologic and ecologic studies will help determine outbreak potential.