A survey of parasites in freshwater fishes from Nong Han wetland, Udon Thani Province, Thailand.

The diversity of fish parasites from freshwater fishes collected from the Nong Han wetland (Udon Thani Province, Thailand) was studied by visually examining 22 freshwater fish species (253 samples) from 19 genera for external and internal parasites. A majority of fishes in the Nong Han wetland were infected by parasites (75.89%). Twenty fish species (75.89%) were infected with a total of 29 species of parasites. These included 9 species of monogeneans, 5 crustaceans, 5 acanthocephalans, 4 nematodes, 3 digeneans, and 3 species of cestodes. Cyclocheilichthys apogon had the most diverse parasite community (8 species). Seasons affected the prevalence and mean intensity of parasitic infection; the prevalence was highest during the rainy (85.54%) and winter (84.75%) seasons, and lower during the summer (63.96%) season. Fish diversity and parasite diversity exhibited a positive correlation relationship. In the light of declining fish populations in the Nong Han wetland, this study may provide critical information for the sustainable management of this wetland. Furthermore, some of the identified fish parasites can be harmful to humans if fish is eaten raw or improperly cooked, as is the tradition in northeastern Thailand, so our findings may bear relevance for public health workers as well.