The epidemiology of giardiasis in New Zealand, 1997-2006

Aims New Zealand has a higher incidence rate of giardiasis than other developed countries. This study aimed to describe the epidemiology of this disease in detail and to identify potential risk factors.

Methods We analysed anonymous giardiasis notification (1997–2006) and hospitalisation data (1990–2006). Cases were designated as urban or rural and assigned a deprivation level based on their home address. Association between disease rates and animal density was studied using a simple linear regression model, at the territorial authority (TA) level.

Results Over the 10-year period 1997–2006 the average annual rate of notified giardiasis was 44.1 cases per 100,000 population. The number of hospitalisations was equivalent to 1.7% of the notified cases. There were 2 reported fatalities. The annual incidence of notified cases declined over this period whereas hospitalisations remained fairly constant. Giardiasis showed little seasonality. The highest rates were among children 0–9 years old, those 30–39 years old, Europeans, and those living in low deprivation areas. Notification rates were slightly higher in rural areas. The correlation between giardiasis and farm animal density was not significant at the TA level.

Conclusions The public health importance of giardiasis to New Zealand mainly comes from its relatively high rates in this country. The distribution of cases is consistent with largely anthroponotic (human) reservoirs, with a relatively small contribution from zoonotic sources in rural environments and a modest contribution from overseas travel. Prevention efforts could include continuing efforts to improve hand washing, nappy handling, and other hygiene measures and travel health advice relating to enteric infections.

A tale of two parasites : the comparative epidemiology of cryptosporidiosis and giardiasis

New Zealand has a higher reported incidence of cryptosporidiosis and giardiasis than most other developed countries. This study aimed to describe and compare the epidemiology of these infections in New Zealand, to better understand their impact on public health and to gain insight into their probable modes of transmission. We analysed cryptosporidiosis and giardiasis notification data for a 10-year period (1997–2006). Highest rates for both diseases were in Europeans, children aged 0–5 years, and those living in low-deprivation areas. Cryptosporidiosis distribution was consistent with mainly farm animal (zoonotic) reservoirs. There was a dose–response relationship with increasing grades of rurality, marked spring seasonality, and positive correlation with farm animal density. Giardiasis distribution was consistent with predominantly human (anthroponotic) reservoirs, with an important contribution from overseas travel. Further research should focus on methods to reduce transmission of Cryptosporidium in rural areas and on reducing anthroponotic transmission of Giardia.

Epidemiology of acute rheumatic fever in New Zealand 1996-2005

Aim: Acute rheumatic fever (ARF) and its sequela chronic rheumatic heart disease remain significant causes of morbidity and mortality in New Zealand, particularly among Māori and Pacific peoples. Despite its importance, ARF epidemiology has not been reviewed recently. The aims of this study were to assess trends in ARF incidence rates between 1996 and 2005 and the extent to which ARF is concentrated in certain populations based on age, sex, ethnicity and geographical location.

Methods: This descriptive epidemiological study examined ARF incidence rates using hospitalisation data (1996–2005) and population data from the 1996 and 2001 censuses. Rates were compared by using rate ratios and 95% confidence intervals.

Results: New Zealand's annual ARF rate was 3.4 per 100 000. ARF was concentrated in certain populations: 5- to 14-year-olds, Māori and Pacific peoples and upper North Island areas. From 1996 to 2005, the New Zealand European and Others ARF rate decreased significantly while Māori and Pacific peoples’ rates increased. Compared with New Zealand European and Others, rate ratios were 10.0 for Māori and 20.7 for Pacific peoples. Of all cases, 59.5% were Māori or Pacific children aged 5–14 years, yet this group comprised only 4.7% of the New Zealand population.

Conclusion: ARF rates in New Zealand have failed to decrease since the 1980s and remain some of the highest reported in a developed country. There are large, and now widening, ethnic disparities in ARF incidence. ARF is so concentrated by age group, ethnicity and geographical area that highly targeted interventions could be considered, based on these characteristics.

The epidemiology of the first wave of H1N1 influenza pandemic in Australia : a population-based study

Objectives: Following the recent H1N1 influenza pandemic we were able to describe seropositivity in a repre-sentative sample of adults prior to the availability of a specific vaccine.

Methods: This cross-sectional serological study is set in the Barwon Statistical Division, Australia. Blood samples were collected from September 2009 through to May 2010, from 1184 individuals (569 men, 615 women; median age 61.7 years), randomly selected from electoral rolls. Serum was analysed for specific H1N1 immunity using a haemagglutina-tion inhibition test. A self-report provided information about symptoms, demographics and healthcare. Associations be-tween H1N1 infection, gender, households and occupation were determined using logistic regression, adjusting for age.

Results: Of 1184 individuals, 129 (58 men, 71 women) were seropositive. Gender-adjusted age-specific prevalence was: 8.3% 20-29 years, 13.5% 30-39, 10.4% 40-49, 6.5% 50-59, 9.7% 60-69, 10.3% 70-79, 18.8% 80+. Standardised preva-lence was 10.3% (95%CI 9.6-11.0). No associations were detected between seropositivity and gender (OR=0.82, 95%CI 0.57-1.19) or being a healthcare worker (OR=1.43, 95%CI 0.62-3.29). Smokers (OR=1.86, 95%CI 1.09-3.15) and those socioeconomically disadvantaged (OR=2.52, 95%CI 1.24-5.13) were at increased risk. Among 129 seropositive individu-als, 31 reported symptoms that were either mild (n = 13) or moderate (time off work, doctor visit, n = 18). For age <60, 39.6% of seropositive individuals reported symptoms, whereas the proportion was 13.2% for age 60+.

Conclusions: Following the pandemic, the proportion of seropositive adults was low, but significant subclinical infection was found. Social disadvantage increased the likelihood of infection. The low symptom rate for older ages may relate to pre-existing immunity.

Toxic marine microalgae and shellfish poisoning in the British isles : history, review of epidemiology, and future implications

The relationship between toxic marine microalgae species and climate change has become a high profile and well discussed topic in recent years, with research focusing on the possible future impacts of changing hydrological conditions on Harmful Algal Bloom (HAB) species around the world. However, there is very little literature concerning the epidemiology of these species on marine organisms and human health. Here, we examine the current state of toxic microalgae species around the UK, in two ways: first we describe the key toxic syndromes and gather together the disparate reported data on their epidemiology from UK records and monitoring procedures. Secondly, using NHS hospital admissions and GP records from Wales, we attempt to quantify the incidence of shellfish poisoning from an independent source. We show that within the UK, outbreaks of shellfish poisoning are rare but occurring on a yearly basis in different regions and affecting a diverse range of molluscan shellfish and other marine organisms. We also show that the abundance of a species does not necessarily correlate to the rate of toxic events. Based on routine hospital records, the numbers of shellfish poisonings in the UK are very low, but the identification of the toxin involved, or even a confirmation of a poisoning event is extremely difficult to diagnose. An effective shellfish monitoring system, which shuts down aquaculture sites when toxins exceed regularity limits, has clearly prevented serious impact to human health, and remains the only viable means of monitoring the potential threat to human health. However, the closure of these sites has an adverse economic impact, and the monitoring system does not include all toxic plankton. The possible geographic spreading of toxic microalgae species is therefore a concern, as warmer waters in the Atlantic could suit several species with southern biogeographical affinities enabling them to occupy the coastal regions of the UK, but which are not yet monitored or considered to be detrimental.