Occurrence
It has been observed in spiny lobsters (Panulirus ornatus) in Vietnam, where it is caused by a species of Fusarium.
It has been observed in shrimp, where the agent is microscopic protozoan Hyalophysa chattoni or a close relative, in Galveston Bay, Texas and other locations.
Causes
There are multiple sources known known to cause black gill disease. Poor pond conditions can cause debris to build up in the gills turning them black. Certain kinds of bacteria and the fungus genus Fusarium are also known causes.
Prevention
With extra care taken to the health of the shrimp, it is possible to prevent cases of black gill disease. The water should have 10-20 parts per thousand parts salinity and filtered.
References
Black gill disease Wikipedia(Text) CC BY-SA