Abalone have been cultured in South Africa for seventeen years. The growing industry has led to
increased intensification. Farms are concentrated in certain areas, notably Hermanus on the South coast,
and may be close to wild abalone populations and processing facilities. These factors contribute to
increased risk of disease emergence. Data on parasite prevalence generated from the abalone health
management program between 2000 and 2004 was analysed for trends. Abalone were sampled
systematically from participating farms and subjected to gross and histological examination. Data on age,
size, gonad development, diet and type of system were recorded. This paper presents the most
significant results for gut protozoa, digestive gland protozoa and rickettsia like prokaryotes, which are all
gut associated. Prevalence was found to increase with increasing age and size. Higher parasite
prevalences were found on the West coast than on the South coast, and outside Hermanus compared to
within Hermanus, suggesting that concentration of farms is not leading to increased prevalence. Gut
associated parasites were significantly more prevalent in animals fed on kelp than artificial feed. It was
found that animals younger than 24 months are more at risk of infection when fed kelp than older animals.
The results indicate that separation of age groups, removal of poor performers and use of artificial feed,
especially in younger animals, are likely to reduce risk of infection with gut associated parasites.