Diseases

Lymphocystis

This is a common viral disease (herpes) that affects both freshwater and saltwater fish. It is noticed by aquaraists when their fish have become stressed, and was thought to have started through invasion of external damage. However, it has now been discovered that it enters the body as a spore taken in through the gills or injested. It can occur in the best kept koi ponds and does not depend on water quality or fish health.

The first signs are small, white pin-prick looking growths that occur on their fins and skin and at this early stage can be mistaken for Ich/Ick (Ichthyophthirius multifiliis). However, it soon clumps together and forms a cauliflower-like growth on the skin, fins and occasionally the gills.

Koi herpes virus ( or CyHV-3) is a viral disease that is very contagious to the common carp Cyrpinus carpio. It is most common found in ornamental koi, which are often used in outdoor ponds or as feeder stock. It can cause 80-100% mortality among infected groups. The first case of KHV was reported in 1998, but not confirmed until later in 1999.

The virus transfers between fish extremely rapidly especially at temperatures between 15-27 degrees C. Studies from the Hebrew University, Israel have concluded that contact with10-40 virus particles per ml of water for five minutes, is sufficient to result in a 70% mortality rate within 15 days.

Carp Pox (Cyprinid herpes virus 1 or CyHV-1) although related to KHV is not as infectious. It is unsightly but not harmful to the fish. Although it is contagious it normally only spreads to young fish with undeveloped immune systems or to older fish as their immune systems begin to weaken. Once infected the fish will have it for life.

Brought on by stress or dropping water temperatures, Carp Pox often occurs during the winter months and into Spring when the fishes immune system is at it's weakest. The condition may improve as the temperatures begin to increase but this is not always the case, some fish may be affected all year round. As the koi's immune system matures it will usually keep the condition under control, however there may be reoccurances during times of stress and when the immune system is weakened.

Can also be known as Head and Lateral Line Erosion (HLLE) and is a fish disease that can affect freshwater and marine fish, especially those in captivity. Hole in the Head may be used in reference to the freshwater variety and HLLE to the marine.