Fish die when attacked by lice
THE LICE THAT KILLS
WHAT makes the fish similar to human and animals when exposed to the sweltering summer heat?
The fish gets attacked by lice, very much under the same conditions that affect people and animals. The only difference is, the fish can die of it.
Dr. Westly Rosario, interim director of the National Integrated Fisheries Technology Development Center in this city, said Thursday that some of the saline tilapia they are culturing had been found to have these parasites.
These are Caligid copepods (Caligus epidemicus) that cause skin and muscle erosion) and isopods (Rhexanella sp.) that make fish feel itchy and sustain scratches from their bodies.
After heavy infection, secondary bacterial may occur resulting in high or mass mortality, Rosario explained.
He said Caligids are oval in shape, up to three millimeters in length and 1.6 mm in width with four pairs of legs and found in Indonesia, Malaysia, Thailand, Vietnam and Philippines.
“They are like human lice,” Rosario said.
The isopods measure about 10 to 50 mm with seven pairs of legs, he said. “They attach on the body surface, mouth, nasal cavity and opercular cavity. The fish would lose appetite and would have slow growth rate. The fish tissue is destroyed. There is necrosis of the dermis and gill filaments,” Rosario said.
“If the problem is not contained, there will be continuous fish mortality,” he said.
Prevention and control of isopods is done by removing them manually and by destroying and crushing them. Fish growers have to “bathe” and disinfect the fish with some chemical in a drying pond bottom.
He added that rapid death occurs in one to two days in young fish during heavy infection.
The infected fish looks like it has many pimples because it is attacked on its skin and gills.
The lice attack the fish whether it is found in freshwater, brackish water and marine water during the extreme summer heat when they easily multiply. And the bigger the density of the fish (where more are cultured in one pond), more become infested.
He said signs are wounds in the fish body “because perhaps due to the itch, the fish scratches its body on the side of the pond or in rough surfaces”. (Tita Roces)
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