Fish Diseases and Management

7.1.3.Normally found external signs in fish and causes

Level I

Gills necrotic – Bacterial, parasitic, fungal

Gills with excess mucus – Bacterial, parasitic, environmental or nutritional

Gills pale – Viral, bacterial, nutritional

Skin with excess mucus – Parasitic, environmental

Re-pigmented areas in skin – Bacterial or parasitic

Dark skin pigmentation – Viral, bacterial, nutritional, eye parasite

Haemorrhage, erythemia – viral, bacterial, parasitic, toxicants

Frayed, eroded, erythemia in fins – Bacterial, parasite, mechanical, physiological disorder

Exophthalmia, haemorrhaged opaque eyes – Viral, bacterial, parasitic, gas super saturation

Ulceration, necrotisation – Bacterial, parasitic

Dropsy – Bacterial, viral, metazoan parasite.

Enlarged abdomen (fluid accumulation) – Viral, bacterial, parasitic

Growth, nodules, raised  spot on skin – Viral, parasitic, neoplasmic, fungal.

Clinical signs observed in shrimps

Major behavioural changes that can be observed in shrimp are:

• reduced escape reflexes

• abnormal swimming near pond edges or at the surfaces associated with lethargy

• unusual aggregations

• reduced preening activity and

• increased feed consumption followed by anorexia.

Morphological abnormalities observed in shrimps

Ø surface fouling of appendages and cuticle for filamentous bacteria and protozoans.

Ø oral region for bacterial "plaques" (presumptive for Vibrio spp.).

Ø larval mycosis - diagnosed by demonstration of hyphae, discharge tube, and motile zoospores.

Ø muscle atrophy in abdomen, especially in 6^th abdominal segment (muscle should fill half of space available).

Ø hepatopancreas atrophy, vacuolisation, lipid droplets and BP inclusion bodies.

Ø cuticular deformities: bent or broken setae or spines

Ø melanized appendages tips or foci.