Water-borne diseases related to recreational water

This section presents statistics on three potentially water-borne diseases in New Zealand: campylobacteriosis, giardiasis and cryptosporidiosis. 

These gastrointestinal diseases cause symptoms like diarrhoea and vomiting. Contaminated recreational water is one way that people may contract these diseases. Other ways include contact with drinking water, farm animals, sick animals, faecal matter, other symptomatic people, and eating contaminated food [1].

Potentially waterborne disease notification rates

The campylobacteriosis notification rate in 2018 was 132 (128–135) per 100,000 people (6,463 notifications). Year-on-year, the notification rate has mostly trended downwards since 2009. The notification rate in 2018 was tied approximately equal lowest with 2015: 128 (124–131) and 2017: 128 (125–131) since reports began in 2001 (Figure 1).

A campylobacteriosis outbreak in Havelock North likely explains the increase in 2016.

The large decrease in the campylobacteriosis rate from 2008 onward (Figure 1) has been attributed to the introduction of food safety regulations for poultry production in 2007 and 2008 [1].

Figure 1: Campylobacteriosis notification rate, 2001–2018

Fig1

Source: [2]

In 2018, the age-standardised notification rate for giardiasis was 31 (29–33) per 100,000 people (1,392 notifications). The rate has remained unchanged from 2015 (Figure 2).

The age-standardised notification rate for cryptosporidiosis was 38 (36–40) per 100,000 people (1,551 notifications) in 2018. The rate marks an increase from 2014 and it is now approximately equal highest with 2001: 35 (33–37) (Figure 2).

Improvements in diagnostic testing partly explain changes in potentially waterborne disease rates. Across New Zealand, there has been a gradual shift to culture-independent diagnostic testing (CIDT) for enteric diseases. CIDT tests for several enteric diseases simultaneously, which has resulted in improved detection rates [3].

Figure 2: Cryptosporidiosis and giardiasis notification rates, 2001–2018

Fig2

Source: [2]

In 2019, there were 146 notifications of campylobacteriosis, 120 notifications of giardiasis, and 39 notifications of cryptosporidiosis that reported contact with recreational water during the incubation period. 

However, risk factor information was not collected for a substantial proportion of notifications, so these numbers may be an underestimate. Risk factor information was only collected for 33% of campylobacteriosis notifications, 45% of giardiasis notifications, and 46% of cryptosporidiosis notifications. 

In 2015–19, the following District Health Boards (DHBs) had higher rates of campylobacteriosis, giardiasis and/or cryptosporidiosis where contact with recreational water was listed as a risk factor:
- West Coast DHB
- Tairāwhiti DHB
- Lakes DHB

However, low completion rates for risk factor information in many DHBs suggest the rates presented in the 'Notifications of potentially waterborne disease with recreational water as a risk factor' factsheet are likely to be underestimates (Figure 3a-c).

 Figure 3a: Risk factor completion rate for campylobacteriosis notifications, by DHB, 2015–19

Fig4 v2

 

 Figure 3b: Risk factor completion rate for cryptosporidiosis notifications, by DHB, 2015–19

 Fig6

 Figure 3c: Risk factor completion rate for giardiasis notifications, by DHB, 2015–19

 Fig8

Source: [6]

 

References

  1. Duncan, G. 2014. Determining the health benefits of poultry industry compliance measures: the case of campylobacteriosis regulation in New Zealand. New Zealand Medical Journal 127(1391): 22–37.
  2. ESR. 2020. Notifiable diseases EpiSurv data extraction. Porirua: Institute of Environmental Science and Research Limited. (personal communication with ESR Senior Analysts)
  3. New Zealand Food Safety. 2019. Annual report concerning Foodborne Disease in New Zealand 2018. Ministry for Primary Industries
  4. ESR. 2015. Notifiable and Other Diseases in New Zealand: Annual Report 2014. Porirua: The Institute of Environmental Science and Research. Available online: https://surv.esr.cri.nz/surveillance/annual_surveillance.php
  5. ESR. 2017. Notifiable Diseases in New Zealand: Annual Report 2016. Porirua: Institute of Environmental Science and Research. https://surv.esr.cri.nz/PDF_surveillance/AnnualRpt/AnnualSurv/2016/2016AnnualNDReportFinal.pdf (Accessed 2019)
  6. ESR. 2020. Notifiable diseases EpiSurv data extraction. Porirua: Institute of Environmental Science and Research Limited
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