Incidence of simultaneous infection of infectious hypodermal and haematopoietic necrosis virus (IHHNV) and white spot syndrome virus (WSSV) in Litopenaeus vannamei

Infectious diseases caused by viruses are quite common in pond cultivated shrimp Litopenaeus vannamei. The present investigation reports a rare consortium of two viruses i.e. infectious hypodermal and haematopoietic necrosis virus (IHHNV) and white spot syndrome virus (WSSV) in adult Litopenaeus vannamei. Collections of diseased and normal shrimps were carried out in eighteen ponds from the farms of Andhra Pradesh and Tamil Nadu. Among the eighteen ponds, nine ponds were found to have infected shrimps either by WSSV or by IHHNV, but interestingly only one pond had the shrimps infected by both the viruses. Shrimp infected only with WSSV exhibited white spot on the carapace. IHHNV infected shrimps showed its principle symptoms including abbreviated rostrum, deformed cuticle and short antennae. Co-infected shrimps showed only symptoms of WSSV; IHHNV symptoms were latent. In histological study, the symptoms for both viral infections were evident such as hypertrophied nuclei and inclusion bodies in the shrimp gill tissues. Further transmission electron microscopic (TEM) examination revealed the presence of both WSSV and IHHNV in the same infected gill of L. vannamei. The unusual infections by both viruses was further confirmed by PCR. This study documents the concurrent occurrence of two different viruses in the gill tissue and their pathogenesis in L. vannamei.