Branchiomycosis (Gill Rot Disease)

This disease is characterized by a marbling appearance in the gills either due to intravascular growth of Branchiomyces sanguinis (B. sanguinis) inside the gill blood vessels or constriction of blood vessels in the case of Branchiomyces demingrans (B. demingrans).  Histologically, gills showed hyperplasia, fusion of gill lamellae, and areas of infarctive necrosis resulting from thrombosis of vessels by fungal hyphae. The prognosis of this disease is bad due to its sudden occurrence and the rapid course of mortality that reaches up to 60% within 48 hrs. The infected fish suffer mainly from respiratory distress. The disease may be predisposed by bad water quality, high water temperatures and high load of organic matters. Preventative measures are much more effective than treatment which could be achieved by strict hygienic measures, water quality improvement, removal of dead and dying fish, and avoidance of overfeeding, especially at high water temperatures.