A recently repor1t.d dlsease s y n d~o m e of Penaeus monodon In Thalland IS called 'yellow-head' or hua leung In Thal It is usually charactenzed by llght yellow coloratlon of the dorsal cephalothorax area and generally pale or bleached appearance of a f f~c t e d prawns The yellow color In the cephalothorav reglon iesults from the underlying y e l l o~~ hepatopancreas showlng through the translucent carapace In m o~i b u n d shrimp In h~stological prepdrations of moribund yellow-head specimens for the light mlcloscope. no consistent bacteiial fungal or parasltlc agents could be found The lylnphold organs ot yellow-head specimens sho\ved extensive abnormalities These Included obv~ously necrotlc cells and vacuolated cells with hypertrophied nuciel Also evldent were vely densely basophil~c, globose cytoplasmic ~nclusions located adjacent to some ot the hypertroph~ed nuclei Slrn~lar basophil~c inclusions were found In interst~tl~il hepatopancreat~c tissue In connective tlssue u n d e~ lylng the mld gut, In cardlac tissue, In glll t~s s u e and In hematopoetlc tissue T l a n s m~s s~o n electron mlclographs revealed the presence of pic\iously undescrlbed rod-shaped, enveloped virions in the cytoplasm adjacent to the nuclei of cells f~ om various tissues Free vlnons \yere also present In intercellular spaces The virions were s~r n d a to those of the ~tlsect grahulosls vlruses (Baculov~r~dae) In terms of cytoplasmic locatlon size, morphology and development. However, they were not occluded by granulln

A picorna-like virus was detected from diseased fry and fingerling grouper Epinephelus malabaricus cultured in southern Thailand. Affected grouper exhibited dark coloration of the head and tail, loss of equilibrium and corkscrew-like swimming. Pathological changes of affected fish showed vacuolating encephalopathy and retinopathy. Intracytoplasmic inclusions were observed in the nerve cells. From electron microscopic studies, virus particles could be detected in the brain and eyeball of affected fishes. They were round to icosahedral, without an envelope, 20 to 25 nm in diameter and had an electron dense core of 16 nm. Filtrates (0.45 pm) of affected brain and eyeball tissues can produce the same clinical signs in healthy grouper after injection, and the identical virus particles could be observed in the brain and retina of experimentally infected fish.

Sphaerospora epinepheli n. sp. is described from grouper, Epinephelus malabaricus, in cage-cultured and wild fish collected from both coastal lines of southern Thailand. Subspherical to spherical spores and mono- or disporous pseudoplasmodia were observed in the lumen of kidney tubules. Pseudoplasmodia were round to elongate, size range 15.6-22.9 microns (length) x 8.4-21.6 microns (width). Spores were 7.8-10.0 microns (length) x 12.3-14.5 microns (thickness), and 7.0-9.5 microns (width) with two spherical polar capsules of equal size measuring 2.9-4.4 microns in diameter and containing polar filaments with six or seven windings. Two uninucleate sporoplasms showed iodine vacuoles. Blood stages, similar to C-blood protozoans observed from freshwater fish in Europe, were found from peripheral blood smears of grouper. Ultrastructural studies of blood stages showed a similar structure to unidentified mobile protozoans from the blood of carp. Electron dense bodies were observed in the cytoplasm of the primary cell blood stages. Infected proximal-tubular epithelial cells showed highly vacuolated cytoplasm and pycnotic nuclei.

No abstract

Presporogonic (blood) stages of Sphaerospora epinepheli Supamattaya, Fischer-Scherl, Hoffmann, Boonyaratpalin, 1990 were observed in the circulating blood, sinus of kidney, glomerurar capillaries and liver arteries of grouper Epinephelus malabaricus. The earliest detectable stage was a primary cell with one secondary cell. After cell divisions, nine to 16 secondary cells were found in one primary cell. Ultrastructural examination revealed electron-dense bodies (118-145 nm) in the cytoplasm of primary cells. Sporogonic stages and spores were located in Bowman's space and in kidney tubule lumens. Electron micrographs revealed a similar pattern of spore development as described from other Sphaerospora spp. Kidneys infected with S. epinepheli showed highly vacuolated tubular epithelial cells and severely affected renal corpuscles.