There are some fish diseases and infections that can be transmitted from fish, or the water in which they are cultured, to humans. Although the infection of humans with fish pathogens is a relatively unusual event, it is a health risk that needs to be recognised by fish farmers and other people who handle and/or consume farmed seafood.
The incidence of transmission of disease from fish to humans is dependent upon several factors including the type of organism (viral, parasitic or bacterial), the susceptibility of the host (immuno-compromised individuals, presence of open wounds) and environmental factors (quality of the water, depth of penetration of fish spines).
Most disease-causing agents which can transmit from fish to humans are bacterial and their clinical effects and treatments are listed below.
Most disease-causing agents which can transmit from fish to humans are bacterial and their clinical effects and treatments are listed in the table below.
Some species have been recorded in Australian fishes.
Table 1. Some common bacteria and their clinical effects following infection in humans
Serious infection uncommon
Sometimes found in intestinal tract of fish, produces botulinum toxins that can cause botulism from improperly processed food. Can lead to respiratory and muscular paralysis. Early symptoms include fatigue, vertigo, vomiting, diarrhoea, constipation and abdominal swelling.
Soft tissue infections; arthritis; septicaemia; gastroenteritis; meningitis; osteomyelitis
Skin infection (on hands), septicaemia, endocarditis (rare); lymphangitis
Antibiotics; most strains resistant to Vancomycin
Suppurating ulcers; cellulitis;
Lesions; gastroenteritis; septicaemia
Skin lesions (usually hands); ulceration and inflammation of joints
Septicaemia; abdominal pain; diarrhoea; nausea; vomiting
Non-bacterial disease-causing agents include:
Several parasites can infect humans as non-traditional hosts. They enter humans by ingestion of raw or undercooked infected fish. Trematodes and nematodes are known to cause infection in humans.
Harmful algae (dinoflagellates and diatoms) may also accumulate in shellfish and can cause illness in humans. Clinical signs can include muscular aches, gastrointestinal and neurological disorders.
Shellfish, such as oysters, mussels and clams can bio-accumulate viral pathogens from polluted waters. The consumption of contaminated shellfish can cause gastroenteritis, respiratory illness, fever and hepatitis.
Commercial shellfish are grown under a strict food safety program administered by the NSW Food Authority.
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.
Measures that should be taken to reduce the risk of aquatic animal disease transmission include: