Aquatic animal disease and human health
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.
Bacterial fish disease pathogens capable of infecting humans
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
Bacteria | Clinical Effects | Treatment |
|---|---|---|
Aeromonas hydrophila | Serious infection uncommon | Antibiotics |
Clostridium botulinum | 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. | |
Edwardsiella tarda | Soft tissue infections; arthritis; septicaemia; gastroenteritis; meningitis; osteomyelitis | Antibiotics |
Erysipelothrix rhusiopathiae | Skin infection (on hands), septicaemia, endocarditis (rare); lymphangitis | Antibiotics; most strains resistant to Vancomycin |
Streptococcus iniae | Suppurating ulcers; cellulitis; | Antibiotics |
Vibrio spp. | Lesions; gastroenteritis; septicaemia | Antibiotics |
Mycobacterium marinum | Skin lesions (usually hands); ulceration and inflammation of joints | Antibiotics |
Salmonellosis | Septicaemia; abdominal pain; diarrhoea; nausea; vomiting | Antibiotics |
Non-bacterial fish disease pathogens capable of infecting humans
Non-bacterial disease-causing agents include:
- Parasites and harmful algae
- Viruses
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. 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.
Viral diseases
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.
Prevention and control
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:
- Fish should be anaesthetised during handling to avoid injury to fish and fish handlers.
- Gloves should always be worn 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 in any injury.
- 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 open wounds, cuts or abrasions should not come into contact with fish or fish rearing waters.
- Codes of hygienic practice 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.
