KEY POINTS:
New Zealand suffers from one of the highest rates within the Organisation for Economic Co-operation and Development of reported cases of infections caused by cryptosporidium and giardia, research shows.
Papers on both infections, by Otago University's Wellington branch, offered the first comprehensive analyses of their incidence since 1996, Associate Professor Michael Baker said.
Research showed cryptosporidium infections averaged 22 cases per 100,000 from 1997-2006.
In Australia the average figure was 15.8 and Britain 8.5. Figures for the United States and Germany were even lower, at 3 and 1.6 respectively.
Professor Baker said giardia rates followed a similar pattern with an average of 44.1 cases per 100,000 in New Zealand, 5.5 in Britain, 7.1 in the United States and 5.5 in Germany.
Rates were also "highly conservative" as many cases went unseen by medical professionals, he said.
Both infections could cause serious gastroenteritis.
"The reason for our high rate of cryptosporidium probably relates to the fact that we are an agricultural country and it's often spread from animals, particularly cattle," he said.
Cryptosporidium infections were three times higher in rural areas with European children under 10 most likely to contract the disease.
Data indicated giardia was mainly transmitted person to person, and was more prevalent in urban areas and older age groups.
- NZPA
