Skin fluke infestation

Skin fluke infestation is caused by Neobenedenia spp. a parasitic flatworm found in the marine environment.

The disease spreads rapidly in dense fish populations and can be hard to detect because it is transparent when on the skin.

Scientific name

Neobenedenia spp.

Cause

Neobenedenia spp. a capsalid monogenean fluke

Other names

  • Neobenedenia melleni

Description

Neobenedinia spp. are flattened, transparent worms up to 1cm long (by 0.2cm wide) and have characteristic chitinous hooks at one end of their bodies.

Distribution

Known to occur throughout the world, it causes disease in wild, farmed and aquarium fish.

Outbreaks have occurred in Australia during winter when seawater temperatures were less than 20ºC.

Life cycle

The lifecycle of skin fluke infestation is direct. The adult sheds eggs from which an immature infective stage hatches (an oncomiracidium) and that stage actively seeks a new fish host to live on and mature.

Affected animals

  • Most tropical marine finfish with scales

Symptoms

  • Typically presents on the skin, fins and eyes of host fish.
  • Initial signs include cloudy eyes (cornea) and pale patches on the skin (excess mucus).
  • Affected fish can stop eating and swim weakly.
  • As the infestation progresses, the fish will lose scales and its skin will redden due to epidermal damage and the fins will be frayed.
  • The host may rub themselves on hard objects to remove the parasites.

Impacts

There have been reports from seawater cage farms where more than 200,000 barramundi have died in an outbreak.

How it is spread

  • Thrives in crowded conditions (such as aquariums) and marine aquaculture facilities (such as sea cages).
  • Multiplies rapidly in dense populations of susceptible host fish.

Risk period

  • Low seawater temperature
  • High density population
  • Stressed fish.

Monitoring and action

Neobenedenia spp. is a marine parasite and can be killed by freshwater bathing.

Control

Neobenedenia spp. is not known to cause disease in humans.

People should not eat fish affected by Neobenedenia spp. because the damaged skin may allow water bacteria to enter the body, contaminating the flesh.

Contact

General enquiries 13 25 23