Abstract
White Spot Disease (WSD) caused by the White Spot Syndrome Virus (WSSV) is the most devastating viral disease threatening the shrimp culture industry worldwide, including Madagascar. WDS was first reported on the island in 2012; however, little is known about the circulation of the virus and its genetic diversity. Our study aimed at describing the molecular diversity and the spread of WSSV in the populations of Madagascan crustaceans. Farmed and wild shrimps were collected from various locations in Madagascar from 2012 to 2016 and were tested for WSSV. Amplicons from positive specimens targeting five molecular markers (ORF75, ORF94, ORF125, VR14/15 and VR23/24) were sequenced for genotyping characterizations. Four genotypes were found in Madagascar. The type-I genotype was observed in the south-west of Madagascar in April 2012, causing a disastrous epidemic, then spread to the North-West coast. Type-II strains were detected in October 2012 causing an outbreak in another Penaeus monodon farm. In 2014 and 2015, types II and III were observed in shrimp farms. Finally, in 2016, types II and IV were found in wild species including Fenneropenaeus indicus, Metapenaeus monoceros, Marsupenaeus japonicus and Macrobrachium rosenbergii. Considering the economic importance of the shrimp industry for Madagascar, our study highlights the need to maintain WSSV surveillance to quickly take appropriate countermeasures in case of outbreak and to sustain this industry.
Highlights
White Spot Syndrome Virus (WSSV) is the only virus belonging to the genus Whispovirus within the Nimaviridae family [1]
The variable regions (VR14/15 and VR23/24) and VNTR are used for global and regional molecular epidemiology, respectively [27,32]. These results suggest that the strains observed in Madagascar might share a common lineage with WSSV from China or Australia
This study revealed that at least four distinct strains of WSSV are circulating in Madagascar, both in the wild and in aquaculture
Summary
White Spot Syndrome Virus (WSSV) is the only virus belonging to the genus Whispovirus within the Nimaviridae family [1]. Disease (WSD) and it is the most significant viral pathogen of cultured shrimp [2] This virus has a wide range of potential hosts [3], including lobsters, crayfish and crabs [3,4]. The clinical signs of the disease include lethargy, anorexia, white spots on the cuticle and, often, generalized reddish to pink discoloration [10]. This virus is highly contagious, and transmission can occur either horizontally through oral ingestion of infected prawns or contaminated water, or vertically from infected parents in hatcheries [11]
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