A descriptive epidemiology of giardiasis in New Zealand and gaps in surveillance data.
BACKGROUND
Giardia is the most commonly notified waterborne disease in New Zealand, which has high incidence rates compared with other developed countries. Four years of giardiasis notification data were analysed to describe the epidemiological patterns of infection in New Zealand and compared with local and international data.


METHODS
Anonymised information was collected nationally for 7818 notified cases of giardiasis between July 1996 and June 2000. International data were collected from the data sources of respective countries. Infection rates adjusted for confounding factors were calculated and presented by age, gender, ethnicity, and area using statistical and spatial methods.


RESULTS
Most cases occurred in the 1-4 year age group followed by the 25-44 year age group, and were of Pakeha/European ethnicity. Ethnicity was unknown for 18% of cases, thus affecting demographic calculations. Rates were elevated for several Health Districts in New Zealand (West Coast, Wellington, Waikato, Auckland, Hawke's Bay, Hutt, Rotorua, and Tauranga).


CONCLUSIONS
The higher rates of giardiasis observed in New Zealand, in comparison with other developed countries, may be related to environmental or social factors. Time-trend analysis suggests a seasonal pattern. This study identified vulnerable groups and major data-gaps. Recommendations for improvements in disease surveillance and data quality are discussed. Geographical information system (GIS) applications are useful for disease monitoring.
Hoque
Ekramul
E
Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. e.hoque@auckland.ac.nz
Hope
Virginia
V
Scragg
Robert
R
Baker
Michael
M
Shrestha
Rupendra
R
D000293:Adolescent; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D018563:Disease Notification; D005260:Female; D005873:Giardiasis / Q000453:epidemiology* / Q000208:ethnology; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D011159:Population Surveillance; D017678:Sex Distribution