Studies on the inflammatory response of the striped snakehead Channa striatus (Fowler)

Experiments were carried out to define the cellular response of snakehead fish, Channa striatus (Fowler), to integumental ulceration: chronic granulomatosis associated with the standard irritant Freund's adjuvant; bacterial septic abscessation due to Aeromonas hydrophila , and focal exposure to the aquatic phycomycete Achlya debaryana. Following exposure, the pathogenesis of the resultant lesion was followed by means of histopathologlcal examination of sequentially sampled specimens. In the case of integumental ulceration, small artificially induced wounds had re-epithelialized within the remarkably short space of 2-3 hours after incision. Large numbers of macrophages were found throughout the degenerated muscle area at 4-5 hours but had completely disappeared from the area of defect by day 6-12. Small numbers of polymorphonuclear leucocytes were observed only at the very earliest stage after wounding. The wounded site was restored to normal condition by around 21-28 days. Chronic granulomata were invoked by injection with Freund’s complete adjuvant. Macrophage infiltration was particularly active in the early stages after the inoculation and started to decrease by day 21. It started to take on an epithelioid configuration within 24 hours of its development. Fibrosis and vascularization were seen at about the same time around day 4.The regeneration of myofibres had strongly developed by day 6 and the new muscle bundles had replaced the area of fibrosis almost completely by the 28th day. The granulomata lesions were still extant, albeit in a very modified, and highly fibrosed form, by the end of the experiment (11 weeks).The acute inflammatory response was demonstrated in the snakehead by injection with the bacterium, Aeromonas hydrophila. An ulcerative wound developed by day 2 after the inoculation. PMN showed a marked response to the bacterial infection and had infiltrated into the inflammatory area by the second hour after the injection. Bacterial colonies, found in the inflammatory area, were very closely related to these PMN clusters. Fibrosis started to encapsulate the necrotic area around 30-36 hours post injection. The lesion began to heal by day 7 to 10 and the healing process was completed around day 28. A very mild inflammatory response occurred in the snakehead injected with the fungus, Achlya debaryana. Some infiltrated PMN and lymphocytes migrated into the inoculated site at the early stages of the experiment, but macrophage activity dominated in the necrotic muscle area. Fibrosis, new capillaries, and regenerated muscle fibres were found by day 3-4 and the lesion was completely healed around day 6

Biodiversity of chloramphenicol-resistant mesophilic heterotrophs from Southeast Asian aquaculture environments

In the present study, samples of pond water, sediment and farmed species were collected at 12 fish and shrimp farms in Malaysia, Thailand and Vietnam to determine the biodiversity and environmental distribution of chloramphenicol-resistant (CmR) mesophilic heterotrophs in Southeast Asian aquaculture sites. Following isolation on Iso-Sensitest agar supplemented with 35 μg ml−1 Cm and dereplication using (GTG)5-PCR fingerprinting, 557 genotypically unique CmR strains were subjected to polyphasic identification. The 557 mesophilic heterotrophic CmR isolates represented 18 different genera largely dominated by the genera Escherichia (40.2%), Pseudomonas (11.7%), Acinetobacter (11.1%), Klebsiella (7.5%) and Bacillus (5.9%). A total of 439 CmR isolates were further assigned to 31 described species or species groups, mainly including organisms that have been associated with various human opportunistic infections such as Escherichia coli (n = 219), Pseudomonas putida (n = 47), Klebsiella pneumoniae (n = 38) and Acinetobacter baumannii (n = 23). Strains of Escherichia, and most notably, of E. coli, were the only common group of CmR heterotrophs irrespective of country, sample type or farm type. Together with other predominant but less widespread groups such as acinetobacters and pseudomonads, the results of this biodiversity study suggest that E. coli can be regarded as a potential indicator of Cm resistance in Southeast Asian aquaculture environments

Health management for sustainable aquaculture

Aquaculture is a dynamic activity. To be successful and sustainable in this business, new techniques have to be continually developed, and adopted by farmers. Over the last decade, sustainability has become a key word for many different activities, including aquaculture. Many factors are involved in aquaculture sustainability, and health management has an important role among these. In order for aquatic animal health management at the farm level to aid the achievement of optimum yields, the following issues should be considered: suitable site selection, quality of broodstock and seed, reasonable stocking density, feed and feeding programme, water management, prophylactic and therapeutic treatment, and information dissemination. The sustainability of aquaculture at the national and regional levels requires different considerations among which are national policy, assistance priorities for farmers, legislation needs, technology development, and information needs

Thailand

Meeting: Fish Quarantine and Fish Diseases in Southeast Asia, 7-10 Dec. 1982, Jakarta, IDIn IDL-773

Parasites of grouper (Epinephelus coioides) cultured in Thailand

Orange-spotted grouper (Epinephelus coioides) cultured in Thailand were examined for their parasites. There were five parasitic groups found in this investigation, viz., protozoans (four genera), monogeneans (five genera), digeneans (three genera), nematodes (two genera), and crustaceans (two genera). Two ciliated protozoans, Trichodina sp., Cryptocaryon irritans, and a single species of Amyloodinium sp. (flagellated protozoan) were observed externally on the gills and skin, while Sphaerospora sp. (myxozoan) was found to parasitize the kidney tubules of fish samples. Eight species of monogeneans were found, viz., Diplectanum grouperi, Pseudorhabdosynochus coioidesis, P. lantauensis, P. epinepheli, Haliotrema sp., two undescribed species of Pseudorhabdosynochus, Megalocotyloides sp. from the gills, and one species of monogenean, Benedenia epinepheli, from the skin. Digeneans, Aphanurus stossichi and Prosorhynchus pacifica, were found in the alimentary tract and a species of didymozoid, Gonapodasmius epinepheri, was present as yellow cysts attached to the gill filament. Two species of rare Philometra sp. and anisakid larva were observed on the body wall near the rectum and in the intestine, respectively. Two groups of crustaceans were found as external parasites, Caligus (copepod) and Rhaxanella (isopod). Monogeneans seemed to be major parasites of orange-spotted grouper in this study, which was indicated by great numbers and occurrence of Diplectanum epinepheli. There was no significant difference in parasite abundance among their own groups during the sampling period. Overall water quality parameters studied were stable, except transparency that fluctuated depending on the rainfall and tide. The occurrence of monogeneans showed correlation to water transparency. All fish samples showed no abnormal sign or symptom caused by parasitic infection

<i>Rohdella siamensis</i> gen. et sp.nov. (Aspidogastridae: Rohdellinae subfam.nov.) from fresh water fishes in Thailand, with a reorganization of the classification of the subclass Aspidogastrea

SUMMARYRohdella siamensis, a new genus and species of aspidogastrean, is described from freshwater fishes in Thailand. A new subfamily, the Rohdellinae, is erected to accommodate this worm on the grounds that it differs from all known aspidogastreans in that the male and female ducts unite to form an hermaphroditic duct, with the result that the intromittent organ is a sinus-organ and not a cirrus. A new classification of the subclass Aspidogastrea is presented. Two orders are recognized: the Aspidogastrida, containing a single family, the Aspidogastridae, which in turn contains 3 subfamilies, the Aspidogastrinae, the Cotylaspidinae and the Rohdellinae subfam.nov.; and the Stychocotylida ord.nov., containing 3 families, the Stichocotylidae, the Multicalycidae fam.nov. and the Rugogastridae. The systematic position of the Stichocotylida, and especially the Rugogastridae, is commented upon.</jats:p