Tilapia Topic: Disease Vector

Leeches

The fish leech, Myzobedella lubugris is occasionally found on tilapia cultured in brackish to saltwater areas. These leeches appear as thin, round brown to black þwormsþ which attach to the ventral surfaces of the head or body, the pelvic, pectoral or caudal fins of tilapia. Usually, the number of leeches found on a tilapia is one or two, however, in exceptional cases higher infections have occurred. Since the leech feeds on blood from the host fish, heavy infestation may cause fatal blood loss anemia.

Juvenile and adult leeches attach to the fish host, but also move between the host and the bottom substrate where the eggs -- known as cocoons -- are deposited. Juveniles are just small versions of adults in appearance. While M. lubugris will utilize tilapia as a host, tilapia are probably not the preferred host species for this leech.

Since M. lubugris can adapt to salt and freshwater, treatment with salinity shock is probably not effective for control of this parasite. Trichlorfon, an organophosphate insecticide, has been reported as an effective chemical control for leech infestation of fish. However, this chemical has not been approved for use in tilapia and is not recommended. If only a few fish in a cultured population are infected by leeches, the parasites can be removed manually.

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