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Zika virus (ZIKV) is a major public health problem worldwide. After several reported outbreaks, the current extent of infections caused by this orthoflavivirus in the Sahel remains to be explored. We investigated the prevalence of neutralizing antibodies against ZIKV in the general population, in HIV-infected individuals and in livestock in Chad using a seroneutralization assay that ensures high specificity level. In this retrospective serological serosurveillance investigation, we estimated the neutralizing seroprevalence to be approximately 26 % (18/69) in healthy Chadian participants and 17 % (16/94) in HIV-infected individuals, with no statistical difference between these two subgroups or genders. In addition, we found an overall ZIKV prevalence of 14 % (8/59) in small ruminants (sheep and goats) living in the Lake Chad Basin area, demonstrating virus circulation in animals. Our pilot study shows for the first-time evidence of ZIKV circulation in humans and in livestock in Chad in close interaction with humans, and highlights the main challenges associated with this virus in Sahelian areas.

Mosquito-borne diseases have a significant impact on humans and animals and this impact is exacerbated by environmental changes. However, in Tunisia, surveillance of the West Nile virus (WNV) is based solely on the surveillance of human neuroinvasive infections and no study has reported mosquito-borne viruses (MBVs), nor has there been any thorough serological investigation of anti-MBV antibodies in horses. This study therefore sought to investigate the presence of MBVs in Tunisia. Among tested mosquito pools, infections by WNV, Usutu virus (USUV), and Sindbis virus (SINV) were identified in Cx. perexiguus. The serosurvey showed that 146 of 369 surveyed horses were positive for flavivirus antibodies using the cELISA test. The microsphere immunoassay (MIA) showed that 74 of 104 flavivirus cELISA-positive horses were positive for WNV, 8 were positive for USUV, 7 were positive for undetermined flaviviruses, and 2 were positive for tick-borne encephalitis virus (TBEV). Virus neutralization tests and MIA results correlated well. This study is the first to report the detection of WNV, USUV and SINV in Cx. perexiguus in Tunisia. Besides, it has shown that there is a significant circulation of WNV and USUV among horses, which is likely to cause future sporadic outbreaks. An integrated arbovirus surveillance system that includes entomological surveillance as an early alert system is of major epidemiological importance. [ABSTRACT FROM AUTHOR]

Mosquito-borne diseases have a significant impact on humans and animals and this impact is exacerbated by environmental changes. However, in Tunisia, surveillance of the West Nile virus (WNV) is based solely on the surveillance of human neuroinvasive infections and no study has reported mosquito-borne viruses (MBVs), nor has there been any thorough serological investigation of anti-MBV antibodies in horses. This study therefore sought to investigate the presence of MBVs in Tunisia. Among tested mosquito pools, infections by WNV, Usutu virus (USUV), and Sindbis virus (SINV) were identified in Cx. perexiguus. The serosurvey showed that 146 of 369 surveyed horses were positive for flavivirus antibodies using the cELISA test. The microsphere immunoassay (MIA) showed that 74 of 104 flavivirus cELISA-positive horses were positive for WNV, 8 were positive for USUV, 7 were positive for undetermined flaviviruses, and 2 were positive for tick-borne encephalitis virus (TBEV). Virus neutralization tests and MIA results correlated well. This study is the first to report the detection of WNV, USUV and SINV in Cx. perexiguus in Tunisia. Besides, it has shown that there is a significant circulation of WNV and USUV among horses, which is likely to cause future sporadic outbreaks. An integrated arbovirus surveillance system that includes entomological surveillance as an early alert system is of major epidemiological importance.

Infectious hematopoietic necrosis virus (IHNV) is a pathogen of importance for salmonid aquaculture. In this study, we aimed to characterize virus behavior and defense mechanisms developed in rainbow trout (RT, Oncorhynchus mykiss) experimentally infected with isolates belonging to the five described genotypes of IHNV, i.e. L, U, M, E and J. Mortality was monitored for two months, and blood and target organs were sampled at different times post-infection to assess viral load and cellular and humoral immune responses. Profiles of virulence were highly linked to precocious viral replication but also to the innate and specific immunity elicited in the host. Seroneutralization test (SNT) used for specific antibodies detection exhibited reliable results, with efficient cross-neutralization observed in heterologous systems except for the Asian representative. These data bring new insights about IHNV/RT interaction and reinforce the interest of SNT as preventive and epidemiological tool. • Innate and specific immunity in rainbow trout are highly connected to strain virulence. • Cross-neutralization was demonstrated between strains belonging to different genotypes. • Cross-neutralization is more marked between strains adapted to a specific host. • Standard SNT targeting IHNV antibodies is a reliable indicator (except Asian strains). [ABSTRACT FROM AUTHOR]