An iridovirus (tentatively named SIV, sergestid iridovirus) that causes high mortality in the sergestid shrimp, Acetes erythraeus, was found in Madagascar in 2004. Severely affected shrimp exhibit a blue–green opalescence. Histological examination revealed massive cyto-plasmic inclusions in the cuticular epithelial cells, connective tissues, ovary and testes. The electron microscopic examination showed paracrystalline arrays of virions at a size of 140 nm, suggesting infection with an iridovirus. A pair of PCR primers were selected from the conserved region of the major capsid protein (MCP)-coding sequence among insect iridoviruses and used to amplify a 1.0 kb frag- ment from the infected A. erythraeus. This fragment was cloned, sequenced and found to be highly similar (upto 80% similarity in trans- lated amino acids with an E value of 1e [1] 124) to the MCP of invertebrate iridoviruses. This clone was then labeled with digoxigenin-11-dUTP and hybridized to tissue sections of infectedA. erythraeus, which reacted positively to the probe. The reacting tissues included epithelial cells, connective tissues, and the germinal cells the same cells as those with inclusions. A PCR method was also developed from the MCP coding sequence for detecting SIV. Journal of Invertebrate Pathology 96 (2007) 255–260. Kathy F.J. Tang, Rita M. Redman, Carlos R. Pantoja, Marc Le Groumellec,Panchayuthapani Duraisamy, Donald V. Lightner. Department of Veterinary Science and Microbiology, University of Arizona, Tucson, AZ 85721, USA. AQUALMA, Aquaculture de la Mahajamba, Mahajanga 401, Madagascar. Corresponding author. Fax: +1 520 6214899.

E-mail address: fengjyu@u.arizona.edu (K.F.J. Tang).