Alveolar echinococcosis: From a deadly disease to a well-controlled infection. Relative survival and economic analysis in Switzerland over the last 35 years

Background/Aims

Alveolar echinococcosis (AE) is a serious liver disease. The aim of this study was to explore the long-term prognosis of AE patients, the burden of this disease in Switzerland and the cost-effectiveness of treatment.

Methods

Relative survival analysis was undertaken using a national database with 329 patient records. 155 representative cases had sufficient details regarding treatment costs and patient outcome to estimate the financial implications and treatment costs of AE.

Results

For an average 54-year-old patient diagnosed with AE in 1970 the life expectancy was estimated to be reduced by 18.2 and 21.3 years for men and women, respectively. By 2005 this was reduced to approximately 3.5 and 2.6 years, respectively. Patients undergoing radical surgery had a better outcome, whereas the older patients had a poorer prognosis than the younger patients. Costs amount to approximately €108,762 per patient. Assuming the improved life expectancy of AE patients is due to modern treatment the cost per disability-adjusted life years (DALY) saved is approximately €6032.

Conclusions

Current treatments have substantially improved the prognosis of AE patients compared to the 1970s. The cost per DALY saved is low compared to the average national annual income. Hence, AE treatment is highly cost-effective in Switzerland.

Introduction

Human alveolar echinococcosis (AE), a hepatic disease resembling liver cancer, is caused by the larval stage (metacestode) of the fox tapeworm Echinococcus multilocularis. The parasite is distributed in the northern hemisphere, the endemic area stretching from North America through central and eastern Europe to central and East Asia including northern parts of Japan [1], [2], [3]. In humans, the metacestode can grow over years before symptoms such as abdominal pain, jaundice, hepatomegaly and weight loss might occur. Untreated, AE may result in severe hepatic dysfunction and metastases in other organs with high mortality. The average survival rate 10 and 15 years after diagnosis of untreated patients, has been reported to be as low as 29% and 0%, respectively [4].

The parasite is highly endemic in Switzerland where it naturally cycles between foxes and various rodent species [5]. Humans acquire the disease by the ingestion of parasite eggs directly or indirectly from fox faeces or from other infected definitive hosts such as dogs. Recently, the fox population in central Europe has increased significantly, which has been accompanied by an invasion of urban areas by foxes due to increases in the anthropogenic food supply. The prevalence rate of E. multilocularis in foxes in the core endemic region of central Europe has been recorded to range between 35% and 65% [2], [3], [5], [6]. This high prevalence together with the increasing urban fox population inevitably will result in increases in the environmental contamination with Echinococcus eggs leading to an increased risk of transmission to humans [5]. Accordingly, current data suggest that the incidence of AE also significantly increased from approximately 0.10 cases per 100,000 between 1993 and 2000 to 0.26 cases per 100,000 between 2001 and 2005 [7]. Improved diagnostic accuracy, due to modern imaging techniques such as computerized tomography [8] was unlikely to fully account for this increase. The increase in incidence occurred after an approximately 4-fold increase in the fox population between 1980 and 1990. The latency period of human AE is thought to be approximately 10–15 years [4] which corresponds well to the observed increase in human AE some 10–15 years after the fox population started to rise in Switzerland [7].

With behaviour similar to that of a malignant tumour, AE can be a devastating human disease. Treatment often requires radical surgery and/or life long anti-parasitic chemotherapy [4], [9]. Relative survival analysis is accepted as the method of choice for population-based cancer survival studies although a randomised clinical trial would be the preferred method to assess clinical efficacy [10]. However, as AE is a rare disease in Europe such clinical trials would be very difficult to conduct. Hence, multivariate survival analysis could indicate likely survival when the background prognostic factors (such as patient age) are removed. Any changes in the survival rates for recently diagnosed patients could also give important clues to treatment efficacy as new patient management strategies are introduced. Therefore, a major objective of this study was to analyze long-term changes in the prognosis of AE-affected patients as an indicator of the effectiveness of modern treatment protocols.

In addition, treatment of this disease represents a considerable, but as yet unknown financial burden. Estimates of the burden of disease of cystic echinococcosis (CE) a related disease, caused by Echinococcus granulosus have been substantial both in localized endemic areas and globally [11]. Estimates for disease burden of AE have been reported only from one highly endemic region in China [12], [13], but there are no estimates for disease burden in the central European endemic area. Because AE has a greater clinical severity and a poorer prognosis the burden of disease of individuals diagnosed with this condition is likely to be higher compared to individuals with CE. In addition, burden analysis can provide an estimate of the cost-effectiveness of present treatment protocols for AE-affected patients.

Studies have shown that periodic treatment of fox populations with anti-helmintic treated baits can result in substantial reductions in the prevalence of Echinococcus in foxes [14]. However, the cost-effectiveness of such strategies in terms of the reduction in AE incidence has not yet been evaluated. An estimate of the burden of AE in Switzerland, in terms of both monetary and non-monetary methods [15], can provide an objective measure against which costs of control strategies such as periodic baiting of foxes can be measured.