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Abstract:
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To demonstrate pathological changes due to white spot virus infection in Fenneropenaeus indicus, a batch
of hatchery bred quarantined animals was experimentally infected with the virus. Organs such as gills,
foregut, mid-gut, hindgut, nerve, eye, heart, ovary and integument were examined by light and electron
microscopy. Histopathological analyses revealed changes hitherto not reported in F. indicus such as
lesions to the internal folding of gut resulted in syncytial mass sloughed off into lumen, thickening of
hepatopancreatic connective tissue with vacuolization of tubules and necrosis of rectal pads in hindgut.
Virus replication was seen in the crystalline tract region of the compound eye and eosinophilic granules
infiltrated from its base. In the gill arch, dilation and disintegration of median blood vessel was observed.
In the nervous tissues, encapsulation and subsequent atrophy of hypertrophied nuclei of the neurosecretory
cells were found. Transmission electron microscopy showed viral replication and morphogenesis in
cells of infected tissue. De novo formed vesicles covered the capsid forming a bilayered envelop opened at
one end inside the virogenic stroma. Circular vesicles containing nuclear material was found fused with
the envelop. Subsequent thickening of the envelop resulted in the fully formed virus. In this study, a correlation
was observed between the stages of viral multiplication and the corresponding pathological
changes in the cells during the WSV infection. Accordingly, gill and foregut tissues were found highly
infected during the onset of clinical signs itself, and are proposed to be used as the tissues for routine disease
diagnosis. |