Use of sentinel lambs to survey the effect of an education programme on control of transmission of Echinococcus granulosus in South Powys, Wales.

In this article the effects of an education programme (area II) on transmission of Echinococcus granulosus from dogs to sheep in Wales and of substitution of the education programme by a 6-weekly anthelmintic control programme (area I) are compared with the situation in an area where no control interventions had occurred (area III). The education programme failed to prevent transmission of E. granulosus to sentinel lambs examined at 15 months of age, 6%, 4%, and 10% of which were infected in areas I, II, and III, respectively. Educational efforts did, however, show some positive effects; for example, significantly more farmers (87-98%) in areas I, II, and III used praziquantel to treat their dogs compared with 39% of farmers in a lowland area in the east of England where E. granulosus is absent. In particular, the interval between treatments of dogs was significantly shorter in areas targeted with education programmes, and 38% of farmers in area I treated dogs at a 4-6 week interval, as did 17% in area II and 10% in area III, compared with only 3% in the lowland area. Also, more dogs in Wales (65-88%) were treated at an interval of < or = 3 months, whereas most of the dogs in the lowland area (64%) were treated at intervals of > or = 6 months. The shorter treatment intervals with praziquantel may account for the significantly fewer positive coproantigen tests among dogs in area I (6.3%) and area II (5.6%) compared with area III (23.9%).

Control of hydatid disease in Wales.

OBJECTIVES: To evaluate the success of the south Powys hydatid control programme by analysis of trends in cystic disease in humans and sheep and dog infestation. DESIGN: A review of hospital admissions for human hydatid disease in 1984-90, abattoir prevalence surveys of hydatid cysts in adult sheep, arecoline acetarsol and coproantigen surveys of prevalence of Echinococcus infestation in dogs. SETTING: All hospitals in England and Wales, three abattoirs, and dog populations in mid ands south east Wales. SUBJECTS: Residents of England and Wales admitted to hospital between 1984 and 1990 with a new diagnosis of human hydatid disease (International Classification of Diseases (ICD), ninth revision, code 122) acquired in the United Kingdom. RESULTS: The average annual incidence of human hydatid disease in Powys, mid-Wales, fell from 3.9x10(-5) in 1974-83 to 2.3x10(-5) in 1984-90. Age specific incidence rates in Wales declined over this period only in children, and no cases occurred in children (<15 years) in Powys. Two Welsh children who lived in Gwent and mid-Glamorgan were infected. Prevalence of hydatid cysts in old sheep from south Wales declined during the control period, but in 1993 prevalence of cysts was 13%. Prevalence of E granulosus infestation was zero in the control area in 1993, but it was 2.4% in Powys dogs outside the control area in 1989 and 9.2% in dogs in Gwent in 1991. CONCLUSIONS: Human hydatid disease has been successfully controlled in south Powys but cystic echinococcosis is still endemic in sheep in mid-Wales, and there is a focus of infection in humans, sheep, and dogs in the bordering areas of Gwent and mid-Glamorgan. There is considerable potential for an upsurge in human cases if control measures are relaxed.

A survey of taeniid cestodes in farm dogs in mid-Wales.

In 1983-1988, dogs on 315 farms in Powys, mid-Wales, were purged once with arecoline acetarsol and the faecal purges were examined for cestodes. A few dogs were examined by autopsy. Ninety-seven farms had at least one infected dog, and cestodes were found in 161 of the 882 dogs examined. The ovine strain of Echinococcus granulosus was found in 41 dogs on 25 farms. Taenia hydatigena, T. pisiformis, T. multiceps, T. serialis, T. ovis and Dipylidium caninum were recovered from 85, 35, 15, 3, 19 and 29 dogs respectively. The results are compared with those of previous surveys in Powys and in other regions of Wales.

The cestodes of foxhounds and foxes in Powys, mid-Wales.

Cestodes were found in 129 of 875 foxhounds from 20 packs in Powys, mid-Wales, examined by purging in 1983-1988, in the following order of prevalence: Taenia hydatigena in 57 hounds (6.51%), Echinococcus granulosus in 27 (3.09%), Dipylidium caninum in 25 (2.86%), T. ovis in 14 (1.60%), T. pisiformis in 10 (1.14%), T. serialis in five (0.57%) and T. multiceps in four (0.46%). Of 197 foxes examined by autopsy, 22 harboured cestodes: two (1.02%) had E. granulosus, nine (4.57%) T. polyacantha, eight (4.06%) T. pisiformis, two (1.02%) T. serialis, one (0.51%) D. caninum and one (0.51%) Mesocestoides sp. This is the first definite report of T. polyacantha in British foxes. The results are compared with those of previous surveys in Powys and in other parts of Wales, and the reasons for changes in prevalence are discussed.

Use of sentinel lambs for early monitoring of the South Powys Hydatidosis Control Scheme: prevalence of Echinococcus granulosus and some other helminths.

Sentinel lambs were used to identify young Echinococcus granulosus infections in sheep, to provide an early indication of the progress of the South Powys Hydatidosis Control Scheme. Four sentinel lambs were purchased on each of 60 farms, from inside and outside the control area; they were examined when approximately six, 10 and 15 months of age. Gross examination, thin slicing of organs and histological examination of the lesions in the viscera revealed no E granulosus hydatid cysts in lambs born within the control area, whereas 25 per cent of the 15-month-old lambs from outside the area harboured E granulosus cysts (less than 1 to 2 mm in diameter). Lambs from E granulosus infected farms had significantly higher anti-E granulosus ELISA antibody titres than lambs from uninfected farms. It was concluded that within one year of beginning to treat dogs with praziquantel every six weeks the transmission of E granulosus to sheep had ceased. In contrast, this treatment did not prevent infections with Taenia hydatigena or T ovis; an examination of the 240 lambs revealed T hydatigena in 33.3 per cent of them, Tovis in 4.2 per cent, Dictyocaulus filaria in 12.1 per cent and Meullerius capillaris in 49.2 per cent.

The growth and development of Echinococcus granulosus of sheep origin in dogs and foxes in Britain.

Four separate experiments were carried out by dosing dogs (Beagles and Border collies) and red foxes with protoscoleces obtained from hydatid cysts in sheep from mid-Wales. The dogs and foxes were killed at intervals over a period from 34-180 days after infection and the intestines were examined for Echinococcus granulosus. Border collie dogs were efficient hosts in that large numbers of worms developed, with gravid segments present by 55 days after infection; but Beagle dogs were poor hosts in that only small numbers of immature worms developed. Foxes were poor hosts in that few or no worms developed, but gravid segments were seen in three of 29 foxes. The worms showed morphological features similar to the 'sheep' rather than the 'horse' strain.

Hydatid disease in Whales: 1. Epidemiology.

The literature on the epidemiology of hydatid disease in domesticated animals in Wales is reviewed and the results of a recent survey in a restricted area of Mid Wales summarised. In this survey the epidemiology of hydatid disease was studied with a view to the formulation of methods of control.