Post 8: Gill Flukes

Gill flukes are highly infectious, 1-2 mm long, flatworm parasites commonly found in fresh and salt water aquariums (Klinger & Floyd 1998). This post will focus on the monogenean trematodes-trematodes being a common name for the flukes, and monogenean which describes the host-site specific life cycle of the parasite. Monogenean trematodes affect the gills, skin and fins of the host fish (Klinger & Floyd 1998).

Gill flukes can enter an aquarium water body through water exchanges, transplants of live rocks or be brought in with introduced fish. Gill fluke parasites are equipped with hooks which they use to latch onto their host-with the parasites life span being roughly 7-9 days (Ogawa 2015).

Directly diagnosing flukes through visual observation of the parasite is unlikely until the later stages of infection. Fish that are infected can almost always be seen participating in 'flashing', where the fish brushes the infected area on the sides or bottom of the tank due to physical irritation (Kiskaroly 1977). In the later stages, flukes growing on the fishes gills will interfere with respiration, thus the host will either be seen gasping for air (generally at the surface where oxygen diffusion is greatest), or lethargically sitting at the bottom as it dies.

Preventative steps can be taken to avoid outbreaks of gill flukes, such as fresh water bathing new fish and live rocks before introducing them into a saltwater aquarium; although doing this to fish that have suffered a prolonged fluke infection can cause further damage to the skin and fins (Ogawa 2015). Praziquantel has been shown to be effective in treating gill flukes and other aquatic worm parasites as it generally only requires 1-2 treatments and is non toxic to plants (Ishimaru et al 2013).

Gill fluke vs Skin fluke in fish 

References:

Ishimaru, K. Mine, R. Shirakashi, S. Kaneko, E. Kubono, K. Okada, T. Sawada, Y. Ogawa, K 2013, '

Praziquantel Treatment against Cardicola Blood Flukes: Determination of the Minimal Effective Dose and Pharmacokinetics in Juvenile Pacific Bluefin Tuna', 'Aquaculture', vol. 402-403, pp. 24-27

Kiskaroly, M 1977, 'Study of the Parasite Fauna of Freshwater Fishes from Fish Ponds of Bosnia and Herzegovina. A. Monogenean Trematodes 1. I. Cyprinid fish ponds', 'Veterinaria', vol. 26, pp. 195-208

Klinger, R. Floyd, R 1998, 'Introduction to Freshwater Fish Parasites', 'University of Florida-Fredrick, Aldridge & Jerome' 

Ogawa, K 2015, 'Diseases of Cultured Marine Fishes caused by Platyhelminthes (Monogenea Digenea, Cestoda)', 'Parasitology', vol. 142, pp. 178-195