Human hydatidosis in New South Wales and the Australian Capital Territory, 1987-1992

Human hydatidosis in New South Wales and the Australian Capital Territory, 1987-1992

David J Jenkins and Karen Power

Abstract - Authors' details - Introduction - Methods - Results - Discussion - Acknowledgement - References - Box 1 - Box 2 - Figure 1 - Figure 2 - Figure 3 - ©MJA1996 -
For editorial comment, see McCullagh

Objective: To determine the prevalence of human hydatidosis in New South Wales and the Australian Capital Territory.
Methods: Data on human hydatid infection occurring between 1987 and 1992 were collected retrospectively from 25 hospitals and 13 health services in New South Wales and four hospitals in the Australian Capital Territory. Mean annual prevalences of human hydatidosis were determined for shires in eastern New South Wales and data on infection in immigrants and Australian-born patients were compared.
Results: 321 patients were diagnosed with hydatid disease, 1987-1992; 195 were new cases and 117 readmissions (nine cases were not identified as new or recurrent). Most patients lived in the eastern half of New South Wales (which includes the Australian Capital Territory), half in rural areas and half in the major coastal cities. Most Australian-born rural patients lived in 39 shires in the north-eastern and south-eastern Tablelands. Sixty per cent of the patients in major cities were born overseas.
Conclusions: Hydatid infection occurs more commonly in south-eastern Australia than the official figures suggest. In rural areas of the north-eastern and south-eastern Tablelands hydatid infection is of public health importance. The national notification system must be improved and control campaigns alerting the public to the dangers of hydatid infection promoted. (MJA 1996; 164: 18-21)

Introduction

The tapeworm genus Echinococcus is an important zoonosis which is endemic in many parts of the world. The only species occurring in Australia is Echinococcus granulosus. It was probably introduced with infected domestic livestock during European settlement and is now widespread in domestic livestock and wildlife, with wildlife acting as an important reservoir.¹ Dogs (domestic and wild) and foxes are the definitive hosts (Figure 1).

Humans become infected by the ingestion of eggs passed in faeces of dogs. Oncospheres released from the eggs penetrate the intestinal mucosa and, via the portal system, lodge in the liver, lungs, muscle or other organs, where the hydatid cysts form.

Because of inadequate reporting, the prevalence of human hydatid infection in Australia is unknown. From the earliest published studies human hydatidosis in New South Wales has occurred mainly in people living in rural areas in the eastern half of the State associated with the Great Dividing Range.^2-4 Dew, in 1928, reported a relatively even distribution of patients with hydatidosis in eastern New South Wales, but subsequent reports showed an increasing trend for patients to be concentrated in the north-eastern and south-eastern Tablelands.^3-5

To assess the health risk associated with E. granulosus, a retrospective survey of hydatid infection was conducted between 1987 and 1992 by examining records of patients with hydatidosis from hospitals and health services in New South Wales (NSW) and the Australian Capital Territory (ACT).

Methods

All the public and private hospitals and area and district health services in NSW and the ACT were asked to supply data of patients with confirmed hydatidosis who were admitted between January 1987 and December 1992. After approval of our written request, all institutions ( four hospitals in the ACT and 25 hospitals and 13 health services in NSW ( supplied data comprising:

- Sex;
- Date of admission;
- Date and country of birth;
- Place of residence at admission;
- Cyst location; and
- Whether the infection was new or recurrent.

We maintained patient confidentiality by using initials only for individual identification. Multiple admissions for the same patient were identified from admission dates, initials, age, sex and general location of residence at the time of admission. We calculated mean annual prevalences of infection using 1991 Census data.⁶

Results

Three hundred and twenty-one patients with confirmed hydatidosis were treated between 1987 and 1992. These comprised 195 new cases (107 males and 88 females), 117 recurrent cases (27 cases had their first treatment before this survey began) and nine cases not identified as new or recurrent.

Two hundred and eighty-two patients (172 new cases and 110 recurrent cases [including those not classified as new or recurrent]) were treated in NSW and 39 patients (23 new cases and 16 recurrent and unclassified cases) were treated in the ACT (16 and 14, respectively, of those treated in the ACT lived in NSW).

Rural patients

Except in three cases, hydatid infection in rural patients, most of whom were Australia-born, occurred in the eastern half of NSW at higher altitudes, mainly associated with the Great Dividing Range (Figure 2). There were concentrations of patients in the north-eastern and south-eastern Tablelands, and these two areas were connected by a corridor parallel to the coast where further cases occurred.

The mean annual prevalence of human hydatidosis in rural NSW was 2.6 cases per 100 000 rural population. Cases occurred in 15 shires [counties] in the north-east and 24 shires in the south-east. On a shire-to-shire basis, the mean annual prevalence of infection ranged from 0.3 to 17.7 and 0.5 to 23.5 (cases per 100 000 population), respectively, in these two areas (Box 1).

Four of the cases (three new and one recurrent) were in Aboriginal people. These four cases represented a mean annual prevalence of hydatid infection of 1.1 cases per 100 000 in the Aboriginal population of NSW.

Urban patients

There were 152 cases diagnosed from the three major metropolitan centres of NSW (Sydney, Newcastle and Wollongong), which included 98 new cases, mostly in patients born overseas (60%); in rural areas the reverse was evident (85% of rural patients were born in Australia).

Of the patients born overseas, all were living in NSW, except one ACT resident. The mean annual prevalence of infection was calculated for 25 ethnic groups (each with a population of over 1000) resident in NSW (Box 2). The highest mean annual prevalence occurred in the Iranian population (6.6 cases/100 000) and the lowest in the German population (0.5 cases/100 000). Most cases came from the Greek and Lebanese communities and communities of people from the former Yugoslavia (13, 10 and 8, respectively), but because of their relatively large populations in NSW, these cases represented only a mean annual prevalence of 4.8, 3.2 and 2.2, respectively.

Age distribution

Age-group distribution profiles of the patients born in Australia and those born overseas are compared in Figure 3. All age groups are represented among Australian-born patients with hydatidosis, especially the older age groups, whereas the immigrant population, being generally younger, has fewer cases in the older age groups.

Cyst location

Infection in the liver occurred most commonly (157 of the 195 new cases); 13 cases involved infection in the lungs and four had infection in both liver and lungs. Infection in other less common sites were two each in the spleen, pancreas and leg muscle and one each in the diaphragm, pelvic area, arm muscle, brain, adrenal gland and gallbladder.

Discussion

Retrospective survey data on human hydatidosis cannot give an accurate picture of the prevalence of infection. A number of cases are not seen in hospitals because the infection is asymptomatic, or does not require surgical intervention, and mistakes in coding may occur. However, these data remain a useful indication of infection prevalence.

Our study confirmed the concentration of hydatidosis in the north-eastern and south-eastern Tablelands reported previously.^3-5 The narrow corridor parallel to the coast in the central part of the State is an area where there have been few cases reported previously, but where considerable urban development has occurred over the last decade, and previously undiagnosed patients may have moved to this region.

Population movement from country areas to cities may also account for many of the Australian-born patients diagnosed in urban areas. However, it is also possible for urban residents to be exposed to eggs of E. granulosus. Recent studies have identified infection with E. granulosus in dogs of a recreational pig hunter living in suburban Perth,⁷ and in dogs of Perth residents living in uncleared areas on the outskirts of the city.⁸ Foxes infected with E. granulosus have been found in the suburbs of Canberra.⁹

The older age of the Australian-born compared with the immigrant patients largely reflects the different age-group structures of the two groups. In 1990, 88.3% of immigrants were aged less than 45 years when they arrived in Australia and 27.4% were less than 14 years of age.¹⁰ Migrants may be already infected when they arrive as children, but the long latent period of hydatid disease means it is first detected in adulthood. It is difficult to explain why most Australian-born patients were detected in the age group 31 to 40 years whereas most immigrants were not detected until 41 to 50 years. Infections in immigrants may be caused by a different strain type of E. granulosus with a slower cystic growth rate. Alternatively, there may be a reluctance among newer immigrants to consult local doctors.

The migrants infected with hydatid disease origin(Box 2)ated in countries where E. granulosus is endemic. The order of ranking of countries according to the mean annual prevalence of hydatid infection in their migrant populations in NSW closely reflected the relative importance of human hydatidosis in their countries of origin. The range of prevalences in the migrant populations were no higher than those recorded in shire populations in north-eastern and south-eastern NSW. In at least three of these shires the prevalence of human hydatidosis was two to three times higher than the highest level recorded in a migrant population.

Three of the urban patients and one of the rural patients born in Australia were Aboriginals. The three urban Aboriginal patients are likely to be from a rural background, but as their place of birth was unknown it was not possible to calculate a prevalence of hydatid infection for rural Aboriginal people. The mean annual prevalence of 1.1 cases per 100 000 for the total Aboriginal population of NSW is about a third of the prevalence in the rural non-Aboriginal population. Few cases of hydatid disease in Aboriginal people have been reported. All the reports are from studies in Western Australia during the 1970s, where Aboriginals were always highly represented: 15/57 cases¹¹ and 13/31 cases.¹² Our data represent the first report of hydatid infection in Aboriginal people in NSW; a previous study reported E. granulosus infection in a dog from a NSW Aboriginal community.¹³

The reason for human hydatidosis not being perceived as a problem in Australia can be attributed largely to under-reporting of this notifiable disease;⁵ this has been a problem for many years,^,5,12,14,15 with no signs of improvement. Only 17 of the 321 new and recurrent cases identified in this study had been notified, and in a retrospective study in Victoria for the 12 months up to July 1991¹⁶ only two of the 50 new or recurrent cases had been notified.

Disease recurrence after operative treatment is an important aspect of human hydatid infection. A carefully conducted follow-up study of 39 patients treated surgically in Australia first drew attention to this problem;¹⁷ 22% had had recurrent infection by 30 months, mainly caused by cyst rupture before surgery. In our study, 37.5% of patients (for whom information on new or recurrent infection status was supplied) were treated for recurrent infection.

Effective chemotherapy of patients with hydatid infection would substantially reduce the cost of treatment. This topic has been reviewed,¹⁸ and the most promising drug studied was albendazole. Data from studies on 253 patients indicated that albendazole was an effective cure in 28%, 51% showed improvement, 18% were unchanged and in 2% the cysts continued to grow.¹⁹ The most appropriate use of albendazole may be as an adjunct to surgery. Rupture of cysts and spilling of protoscoleces (which can form new cysts) into the body cavity during surgery is a constant risk, but an immediate postoperative course of albendazole will greatly reduce the chance of new cysts developing.²⁰

Hydatid disease is preventable, and education is one of the most effective tools to achieve this. It is important that State and Federal governments take a responsible attitude towards increasing community awareness, and implement control strategies through education, either by themselves or by funding organisations such as the Australian Hydatid Control and Epidemiology Program. Control of this parasite in Australia requires a long term commitment; the alternative is that hydatid disease will continue to incapacitate individuals and be an additional financial drain on an already overstretched health service.

Acknowledgements

The authors gratefully acknowledge the assistance of the staff of the medical records departments of the following hospitals: Albury, Armidale and New England, Bathurst, Broken Hill, Calvary (ACT), Camperdown, Casino and District, Cooma, Dubbo, Goulburn, Grafton, Grenfell, Griffith, Inverell, John James Memorial (ACT), Lismore, Orange, Parkes District, Prince Henry, Prince of Wales Children's, Queanbeyan, Royal Canberra (ACT, now closed), Royal North Shore, Royal Prince Alfred, St Vincent's, St Vincent's Private, Tamworth, Wagga Wagga, Westmead and Woden Valley (ACT); also the following area and district health services: Brunswick-Byron, Central Coast, Cooma, Hunter, Illawarra, Macleay Valley, Manning Valley, Queanbeyan, South Western Sydney, Southern Sydney and Tumut, Wentworth. We also thank Ms Celia Moss (Australian Bureau of Statistics) and Ms Irene Pasaris (ACT Health Department) for their help and advice and Dr M W Lightowlers, Dr E Bennet, Dr P McCullagh and Professor R C A Thompson for their suggestions in the preparation of the manuscript. This study was funded partly through contributions from the Shire Councils of Bega Valley, Boorowa, Cooma-Monaro, Crookwell, Gunning, Harden, Snowy River, Tumbarumba, Yarrowlumla, Yass and Young, Queanbeyan City Council and the ACT Health Authority. Dr Jenkins' salary was funded by the National Health and Medical Research Council of Australia.

(©MJA 1996; 164: 14-17)

References

1. Schantz PM, Chai J, Craig PS, et al. Epidemiology and control of hydatid disease. In: Thompson RCA and Lymbery AJ, editors. The biology of Echinococcus and hydatid disease. Wallingford, UK: C A B International, 1995: 233-302.
2. Dew HR. Hydatid disease. Its pathology, diagnosis and treatment. Sydney: The Australasian Medical Publishing Company Ltd, 1928.
3. Christopher PJ, Lopez WA. Hydatid disease notifications in New South Wales. Med J Aust 1970; 1: 54-56.
4. Little JM. Hydatid disease at Royal Prince Alfred Hospital, 1964 to 1974. Med J Aust 1976; 1: 903-908.
5. Schreuder S. Survey of hospital admissions for hydatidosis in New South Wales and the Australian Capital Territory, 1982-1987. Aust Vet J 1990; 67: 149-151.
6. Australian Bureau of Statistics. 1991 Census of population and housing. State comparisons. Canberra: ABS, 1993. (Catalogue No. 2731.0.)
7. Thompson RCA, Lymbery AJ, Hobbs RP, Elliot AD. Hydatid disease in urban areas of Western Australia: an unusual cycle involving western grey kangaroos (Macropus fuliginosus), feral pigs and domestic dogs. Aust Vet J 1988; 65: 188-190.
8. Thompson RCA, Robertson ID, Gasser RB, Constantine CC. Hydatid disease in Western Australia: a novel approach to education and surveillance. Parasitol Today 1993; 9: 431-433.
9. Jenkins DJ, Craig NA. The role of foxes Vulpes vulpes in the epidemiology of Echinococcus granulosus in urban environments. Med J Aust 1992; 157: 754-756.
10. Australian Bureau of Statistics. Migration, Australia. Canberra: ABS, 1994. (Catalogue No. 3412.0.)
11. Joske RA. The changing pattern of hydatid disease, with special reference to hydatid of the liver. Med J Aust 1974; 1: 129-132.
12. Stein GR, McCully DJ. Hydatid disease in Western Australia (1957-1967). Med J Aust 1970; 1: 848-850.
13. Jenkins DJ, Andrew PL. Intestinal parasites in dogs from an Aboriginal community in New South Wales. Aust Vet J 1993; 70: 115-116.
14. Davies P, Nicholas WL, Beard TC. Hospital records of hydatid disease in Victoria for 1970 to 1974. Med J Aust 1977; 2: 493-495.
15. Beard TC. Hydatids in Australia ( the present position in man. Aust Vet J 1979; 55: 131-135.
16. Taylor K. Hydatids in 1992: public health lessons. Update. A quarterly bulletin of infectious diseases. Victoria: Department of Health and Community Services, 1993; 2: 63-64.
17. Little JM, Hollands MJ, Ekberg H. Recurrence of hydatid disease. World J Surg 1988; 12: 700-704.
18. Morris DL, Richards KS. Hydatid disease current medical and surgical management. Oxford: Butterworth-Heinemann Ltd, 1992: 94-118.
19. Horton RJ. Chemotherapy of Echinococcus infection in man with albendazole. Trans R Soc Trop Med Hyg 1989; 83: 97-102.
20. Morris DL, Taylor DH. Optimal timing of postoperative albendazole prophylaxis in E. granulosus. Ann Trop Med Parasitol 1988; 82: 65-66.

(Received 11 Apr, accepted 27 Sep 1995)

---

Authors' details

Australian Hydatid Control and Epidemiology Program, Canberra, ACT.
David J Jenkins, MSc, PhD, Research Officer.
Karen Power, BApplSci, Field Officer.