VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

VIRAL DISEASES

• Although there are relatively few common viruses of fish, these viruses do cause important diseases, which can result in markedly high mortality in a very short period.

Viral disease	Causative agent	Symptoms
Lymphocystis	Iridovirus	Multiple creamy white nodules on the skin and fins Increased water temperature and stocking density may facilitate the lymphocystis. Affected fish have multiple raised epithelial nodules 2-3mm in diameter ranging from pure white to pink colour. The nodules may be singular but more commonly appear in granular cluster of several dozen or more. Affected fish usually behave normally and mortality is usually low or non-existent. No effective treatment methods are reported.
Fish pox (also known as carp pox or warts)	Herpes virus	Fishes infected by this disease show the presence of glistening, smooth, flat, milky to tan slightly raised plaques on the skin surface called a papilloma, otherwise known as a wart. These plaques are not permanent but may join to form larger, irregularly shaped lesions over one inch in size. Once they disappear the affected sites may be become darkly pigmented destroying the value of fish.
Spring viraemia of carp virus  (SVCV) disease	Rhabdovirus	It is an acute, systemic, contagious disease It affects primarily the common carp, Cyprinus carpio and several other cyprinids. External signs of SVC includes skin darkening, swollen belly, exophthalmia, petechial haemorrhage on the skin and gills, anaemia and pale gills as well as protrusion and inflammation of the vent. It typically occurs at water temperature below 18°C, and predominantly in the spring.
Koi herpes virus  (KHV) disease	Koi herpes virus (KHV)	Clinical signs of KHV are often non-specific. External signs of KHV include red and white patches on the body, bleeding gills, sunken eyes, pale patches or blister on the skin.
White spot syndrome virus (WSSV) disease	Whispovirus of Nimaviridae	Rapid reduction in food consumption, lethargy, loose cuticle with white spots on inside surface of carapace Also manifested as red coloration (disease also known as "red disease", chromatophore aggregation, not unique 100% mortality within 3-10 days of onset of clinical signs
Monodon baculovirus (MBV) disease	Nucleo polyhedrosis virus	Reduced feeding, variation in growth.
Yellow head virus (YHV) disease	Yellow head virus (YHV)	There are no pathognomonic gross lesions. Yellow discoloration of the cephalothorax
White muscle disease or White tail disease	Extra small virus (XSV) and Macrobrachium rosenbergii nodavirus -MrNV	Lethargy, anorexia and opaqueness of abdominal muscle in post-larvae and adults. Whitish appearance of the tail