Introduction

There are some fish diseases and infections that can be transmitted from fish, and the water in which they are cultured, to man. Although the infection of humans with fish pathogens is a relatively unusual event, however it is a health risk that needs to be recognised by fish farmers, staff and consumers of farmed seafood.

The incidence of disease transmission is dependant upon several factors including the type of organism (viral, parasitic or bacterial etc), the susceptibility of the host (immuno-compromised individuals, open wounds), and environmental factors (quality of the water, depth of penetration of fish spines).

Most disease causing agents in this category are bacterial and their clinical effects and treatments are listed in Table 1.

Optimum farm design, appropriate husbandry and handling, water quality management and regular fish health monitoring will reduce the risk of disease transfer from fish and their environs to workers in the aquaculture industry.

Fish Disease Pathogens Capable of Infecting Humans

Disease-causing agents include:

• Parasites and harmful algae
• Viruses
• Bacteria

Parasitic Diseases and Harmful Algae

Several parasites can infect humans as non-traditional hosts. They enter humans by ingestion of raw or undercooked infected fish. Infection can be caused by trematodes and nematodes. Harmful algae (dinoflagellates and diatoms) may also accumulate in shellfish. Clinical signs can include gastrointestinal, muscular aches and neurological disorders.

Viral Diseases

Shellfish, such as oysters, mussels and clams can bio-accumulate viral pathogens from polluted waters. The consumption of contaminated shellfish has caused gastroenteritis, respiratory illness, fever and hepatitis.

Bacterial Diseases

Prevention and Control

• Fish should be anaesthetised during handling to avoid injury to fish and fish handlers.
• Gloves should be worn at all times when handling fish.
• Minor wounds should be thoroughly washed with clean water and antiseptic applied.
• More serious injuries and illness should be treated by a medical practitioner.
• Doctors should be informed if "fish handling" is involved.
• Workers having an underlying disease or compromised immune system (diabetes, impaired liver function, cancer or HIV) are more susceptible, and should avoid handling fish.
• Workers having cuts or abrasions should not come into contact with fish or fish rearing waters.
• Codes of hygienic practice, Hazard Analysis and Critical Control Points (HACCP) guidelines and Good Aquaculture Practices are essential to lower the risk to employees.
• Educating workers about the prevalence of these risks will go a long way to preventing these diseases.

Glossary

Cellulitis– inflammation of cellular tissue.

Endocarditis– inflammation of the membranes which line the heart and heart valves.

Lymphadenitis– chronic swelling of lymph nodes

Meningitis– inflammation of the brain and spinal chord membranes.

Osteomyelitis– inflammation of the bone

Septicaemia– bacterial infection of the blood

Suppurating- discharging pus from a wound.

Further Information

Lehane L., Rawlin, G.T., 2000. Topically acquired zoonoses from fish: a review. Medical Journal of Australia 173(5):256-9.

Durborow R.M., 1999. Health and safety concerns in fisheries and aquaculture. Occupational Medicine 1492):373-406.

Contacts

NSW DPI – Fish Health Unit, Elizabeth Macarthur Agricultural Institute
Telephone 02 4640 6333

NSW Health
Telephone 02 9816 0268

NSW Food Authority
Telephone 1300 552 406