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Hydatid disease in Wales
105 TRANSACTIONSOFTHE ROYAL SOCIETYOFTROPICAL MEDICINE AND HYGIENE, VOL. 7 I, No. 2.1977.
Hydatid disease in Wales T. M. H. WALTERS Ministry of Agriculture, Fisheries and Food, ’ BeI,rave’, Spa Road. Llandrindod Wells, Powys. L DI 5HA
Hydatid disease is caused by the cystic larval stage of the cestodes Echinococcusgranulosus and E. multilocularis. The latter is thought not to occur in the U.K. E. grunu/OJ~LYexists as two distinct forms with different host species. The adult tapeworm lives in the intestinal tract of the definitive host and the cystic larval stage in organs such as the liver, lungs and brain of the intermediate host which is a different species. The incidence of hydatid disease varies in different parts of the world. The condition necessary to produce the disease is that the parasite should be freely circulated between the definitive and intermediate hosts; human hydatid disease will occur when man becomes interposed in this cycle by living in intimate contact with the definitive host, usually dogs. The explanation of the variable frequency of adults and larvae is always to be found in the different occupations and modes of life of the hosts (LEUCKART,1886; FOSTER,1965). Today hydatid disease is a medical and, to a lesser extent, an economic agricultural problem on all the inhabited continents. Epidemiological studies usually have as their object the elucidation of facts about the disease which are essential to its control in a particular country or region. A multiplicity of host, environmental and agent factors accounts for differences in the observable patterns of distribution of the parasite and its transmission in different areas. As with other infections, knowledge of these factors is necessary to identify vulnerable points for practical attacks (SCHWABE,1969). This study has been conducted in the Welsh border area where it is believed there is the highest incidence of hydatid disease in the U.K. and it is in Wales, and this area in particular, that the disease situation will be considered. Life-cycle of E. granulosus in Wales E. gr’anulosus is a cestode 3-9 mm in length, consisting of three or four proglottides. The terminal segment is gravid and is the broadest and longest. The dog and fox are the normal definitive hosts. Eggs free or released from segments passed in the faeces are picked up by cattle, sheep, horses and pigs on pasture or from the water supply to which they may be carried by the wind. Man can be infected by ingesting eggs attached to inadequately washed vegetables or accidentally picked up by handling a dog. It is also possible that flies may carry eggs to uncovered food or that they may be inhaled in dust (SOULSBY,1968). The eggs, once ingested by the intermediate hosts, hatch in the intestine, liberating oncospheres which penetrate the wall of the intestine and pass to the liver by way of the hepatic portal system. They may remain there or some may pass to the lungs and other parts of the body and develop into.hydatid cysts. Brood capsules
containing protoscoleces develop in the cysts and after five or six months are capable of producing infection in the definitive host. Prevalence of E. granulosus in the definitive hosts It is not possible to differentiate the eggs of E. granuIOSLLS from those of other taeniid cestodes which may be present. To establish that a dog is infected it is necessary to administer a drug (usually arecoline acetarsol or arecoline hydrobromide) which will remove the worms from the small intestine and cause them to be purged fairlv raoidlv whilst still intact and identifiable. Postmortem examination of dogs and foxes will also enable infected animals to be identified. In the U.K. information on the prevalence of E. grarzulosus in dogs has been limited to surveys carried out during the past 50 years. The results of some of these surveys are shown in Table 1. These results show that there is a high infection rate in Wales; COOK(1964) found 23 % of farm dogs he examined in mid-Wales to be infected. A recent survey in the same area confirms the high rate of infection in farm dogs. In this survey of 134 farms it was found that 126 (25:‘:;) of 509 dogs on 70 (52”/,) were infected (WALTERS,1975). From the purged faeces of the 126 infected dogs over 100 E. gvanulosus were collected from 47 (377/,) of the samples. These figures are low because it is unlikely that arecoline acetarsol removed all the worms or that all the worms which were purged were collected. Arecoline hydrobromide is effective as a diagnostic agent in only half of the infected animals (TREJOSet nl., 1965; GEMMELL, 1968). The red fox (Vulpes vulpes) is a definitive host for E. gramdosus and results of post-mortem examination of foxes from two areas of England and from Wales are shown in Table II. The relatively high prevalence of fox infection has been confirmed by a survey carried out during 1975 in mid-Wales when 12 (9 %) of 127 foxes were found to be infected (WALTERS,1975). At autopsy most worms are recovered from the small intestines. Fewer worms were present in the foxes than in the farm dogs, seven of the 12 infected foxes having less than 30 worms (WALTERS,1975). Prevalence of hydatid cysts in the intermediate hosts in the U.K. The infection rates in the intermediate hosts (cattle, sheep and pigs) in the U.K. is obtained by analysing the records kept by slaughterhouses. BLAMIRE (1966), from records kept by 30 slaughter-houses in the U.K., concluded, that 0.5 7: of cattle, 1.O% of sheep and 0.06 ‘A of pigs harboured hydatid cysts. The annual loss to the meat industry as the result of the condemnations of offal was about &55,000 in 1967 and figures collected by the Ministry of Agriculture, Fisheries and Food from 60 slaughterhouses are shown in Table III.
106
SYMPOSIUM
Table I - The prevalence of E. grunulosus --
ON HYDATID
DISEASE
in dogs in the UK
Number of dogs examined
Locality
Reference
Birmingham Birmingham Not stated Lake District Aberystwyth South Wales South Wales mid-Wales mid-Wales Dyfed, Wales
Brailsford (1926) Malcolm quoted by Southwell (1927) Skulski quoted by Miller and Poynter (1956) Cook and Clarkson (1971) Lewis (1927) West (1960) Cook and Crewe (1963) Cook (1964) Walters (1975) Williams (1976a)
Number and percentage of dogs infected
100 some hundreds 200 112 59 50 21 87 509 396
4 (3.6%) 3 (5%) 4 (8%) 2 (10%) 20 (23%) 126 (25%) 50 (12.6%)
Number of foxes examined
Number and percentage of foxes infected
0
: (2%)
Table II - The prevalence of E. granulosus in foxes in the UK
Locality
Reference Cook (1965) Cook (1965) Sinclair (1956) Sinclair (1957) Cook (1965) Cook (1965) Cook (1965) Walters (1975) Williams (1976b) Table III - Condemnations
North West England East Anglia mid-Wales mid-Wales North Wales mid-Wales South Wales mid-Wales Dyfed, Wales
90 73 16 89 29 63 8 127 149
; yw,’ 6 0 5 15 2 12 4
(3;&) (17%) (25%) (25%) (9%) (2.7%)
of offal in the U.K. because of hydatid disease. Figures collected from 60 slaughterhouses
Year
Number and percentage of cattle involved
Number and percentage of sheep involved
1973 1974 1975
6,241 (2.5 %) 5,732 (1.3 %) 7,855 (1.5 %)
30,274 (3.4 %) 32,586 (2.4%) 50,113 (3.3%)
Number and percentage of pigs involved 123 (0.01%) 70 (0.006 %) 86 (0.006 %)
Table IV - Prevalence of hydatid disease in sheep slaughtered in the U.K.
Reference Cook (1965) Cook Cook Cook Cook Blake
(1965) (1965) (1965) (1965) (1973)
Number of sheep examined
Locality Lake District and North Pennines Cheshire and Shropshire North Wales mid-Wales South Wales mid-Wales
When these figures are compared with the condemnations of offal from animals from specific areas and particular slaughterhouses, a much higher infection rate occurs in animals known to originate from the WelshEnglish border areas. The age of the animal at slaughter is also important: in a survey in a mid-Wales slaughterhouse BLAKE (1973) found very few hydatid cysts in 17,000 lambs slaughtered, whereas 123 (37%) of 326 adult sheep were infected. The results for specific areas are shown in Table IV, but they do not give an accurate figure for the local prevalence since few animals are slaughtered in the area where they were born and reared. Sheep from Wales are sold to many areas of England and Scotland and are slaughtered at abattoirs throughout Britain.
3,057 1,642 4,806 3,295 184 326
Number and percentage of sheep infected 130 (4.2%) 81 (4.9%) 755 (15.7%) 177 (5.4%) 28 (15.2%) 123 (37%)
Prevalence of hydatid disease in man in the U.K.
Since hydatid disease is not notifiable in the U.K. its incidence in man is not accurately known. HOWELL (I 940) reported that for the period 1927/36 there were 144 cases of hydatid disease, 30 of which were fatal. These figures, based on the records for Welsh hospitals, included three cases from one household in 1934. HOWELL comments that it is impossible to assess the amount of infection among man in Wales because post-mortem examinations are not done as a routine. When such examinations are carried out it is by no means uncommon to find hydatid cysts in the organs although there were apparently no symptoms present during life. JONATHAN (1960) reported on 44 cases being treated in the North Wales area during the period 1948-57 but the hospital records only extended back over a five-year period.
107
T.M.H.-WALTERS
The Registrar General’s returns for England and Wales for the period 1940-60 give the average number of deaths from hydatid disease as 15 per annum, or 0.37 per million of the estimated population, and for 1960-70 the average numbers were eight per annum or 0.14 per million. The figures for Wales alone for 1948-65 were 1.52 per million. THOMAS (1966) found that during the IO-year period 1953-62 there had been 216 persons resident in Wales in whom hydatid was diagnosed. In most cases the diagnosis had been made as the result of routine investigations but in a small number of cases the diagnosis was made after death. Cases diagnosed in rural areas had a definite connection with farming and with dogs but for most urban dwellers it was not possible to establish a definite relationship with dogs. Inquiries regarding all the children included in the survey established that all except two had had, from infancy, a close relationship with dogs. Discussion Hydatid disease is neither a major public health problem of nor the cause of spectacular economic loss to agriculture in the U.K. There are parts of Wales, particularly the Welsh-English border area, where the prevalence of infection in dogs and sheep has been shown to be much higher than elsewhere. THOMAS (1966) found that hydatid disease in man occurs in every county of Wales but particularly in the recognized sheep-rearing areas. Only one of the 216 cases occurred in Pembrokeshire and two in Cardiganshire, equal to 0.1 per 10,000 of the population, whereas in Radnorshire and Breconshire the rate was 4.7 and 6.3 per 10,000. COOK (I 964) suggested that some 70 % of the farming population in mid-Wales are exposed to infected dogs. In 1975, dogs on over 50 :( of the farms visited in the same area were infected, so that virtually all the farming population is likely to be at risk from their own or their neighbours’ dogs. The sheep is the most important intermediate host and becomes infected when grazing pasture in the immediate vicinity of farm buildings, which has become contaminated by eggs of E. granulosrrs passed by the farm dogs. The dogs in their turn become infected by being fed raw offal from infected sheep or by scavenging sheep which have died on the hill grazings. THOMAS (1966) found that cases of hydatid disease in man in rural areas had a definite connection with farming and with dogs. In the early 19th century Iceland had the highest prevalence of hydatid disease in man ever recorded anywhere. A campaign, which included the treatment of dogs and made it illegal to feed them raw offal, was begun in 1863 (DUNGAL, 1957). At the same time there was an educational campaign on the dangers and on control methods. In the last 20 years only 15 infected sheep have been found at slaughter and there have been no reports of infected dogs (PALSSON, 1972). In New Zealand the National Hydatids Council was set up in 195s to co-ordinate control of hydatid disease. As in Iceland, the anthelmintic treatment of all dogs and a campaign to prevent them from gaining access to raw infected offal were the important principles of the control scheme. The prevalence of E. granulosus in dogs has been reduced from 37% in sheep dogs which were being fed offal (GEMMELL, 1958) to 0.35% in all dogs tested during 1972-73. The Ministry of Agriculture and Fisheries survey at freezing works throughout New Zealand, reported that in 1962, 57 7: of sheep livers were
infected with hydatid: this figure had fallen to 24:< by 1972. Both these countries have shown that even before the new anthelmintics which are now available, it has been possible to reduce the incidence of hydatid disease by informing dog owners of the dangers of the disease and the most important principles of control. It would be valuable to obtain information on the prevalence of infection in dogs in different areas of Wales, with a view to recommending procedures for controlling the infection in areas where man is likely to be exposed to a considerable weight of infection. References Blake, J. (1973). Personal communication. Blamire, R. V. (1966). The diseases most commonly found in abattoirs. Veterinary Annual, 7, 310-316. Brailsford, J. F. (1926). The X-ray diagnosis of animal parasites (helminths) in man. Proceedings of the ROJ~ Society of Medicine, 19 (Section Electrotherapeutics), 41-52. Cook, B. R. (1964). The epidemiology of Echinococcus infection in Great Britain. 11. The incidence of Echirzococcns granulosus and some other cestodes in farm dogs in mid-Wales. Am& r?j” Tropical Medicine and Parasitology,
58,147- 152.
Cook, B. R. (1965). The incidence and epidemiology of Echinococcus in Great Britain. Ph.D. Thesis, Liverpool Ukver.sifJ~.
Cook, B. R. & Clarkson, M. J. (1971). The epidemiology of Echinococcus infection in Great Britain. 111. EchinoCOCCI~S granulosus and cestodes of the genus Taenia in farm dogs in England in the Lake District, northern Pennines and East Anglia. Amzals of Tropicul Medicine and Parasitology,
65, 71-79.
-
-
Cook, B. R. & Crewe, W. (1963). The epidemiology of Echinococcus infection in Great Britain. I. Abnormal behaviour of sheep in the mining valleys of South Wales and its relation to hydatid disease in man. Annals
of Tropicul
Medicke
and Parasitology,
57,
150-156. Dungal, N. (1957). Eradication of Echinococcus in Iceland. New Zealand Medical Journal, 56, 212-222. Foster, W. D. (1965). In: A history ofparasitology. W. D. Foster (Ed.). Edinburgh & London: E. and S. Livingstone, pp. 50-51. Gemmel. M. A. (1958). Cestode problem of domestic animals and man in ihe South Island of New Zealand. New Zealand Medical Journal, 57,442458.
Gemmell, M. A. (1968). Screening of drugs and their assessment for use against the strobilate stage of Echinococcus. Bulletin tion, 39, 57-65.
of the World Health
Organiza-
Howell. N. (1940). Hvdatid disease in Wales. Vetrritmrv Recoid, 5i, 49i-506.
Jonathan, 0. M. (1960). Hydatid disease in North Wales. British Medical Journal, i, 1246-I 253. Leuckart, R. (1886). The parasites of rnu~~, p. 641. (Translated by W. E. Hoyle, Pentland, Edinburgh.) Lewis, E. A. (1927). A study of the helminths of dogs and cats of Aberystwyth, Wales. Journal of Helminthology, 5, 171-182. Miller, W. C. & Poynter, D. (1956). Hydatid cysts in a thoroughbred mare. Veterinary Record, 68,51-53. NationalHydatids Council (1973). 13th Annual Report and Statement of Accounts. National Hydatids Council, Wellington, New Zealand.
108
SYMPOSIUM
ON HYDATID
Palsson, P. A. (1972). Unpublished. Quoted in: Beard, T. C. (1973). The elimination of echinococosis from Iceland. Bulletin of the World Health Owanization. I 48.I 653-660. ” Schwabe, C. W. (1969). Principles of epidemiology: case study of hydatid disease. In: Veterinary medicine and human health. (2nd edit.). London: Baillibre, Tindall and Cassell, pp. 251-263. Sinclair, K. B. (1956). Echinococcus infection in the fox. Veterinary Record, 68, 104. Sinclair, K. B. (1957). Echinococcus infection in the fox. Veterinary Record, 69, 1076. Soulsby, E. J. L. (1968). In: Helminths, arthropods and Protozoa of domesticated animals. Monnig’s Veterinary helminthology and entomology (6th edit.), E. J. L. Soulsby (Ed.). London; BailliBre, Tindall and Cassell, pp. 126-141. Southwell, T. (1927). Experimental infection of the cat and the fox with the adult Echinococcus. Annals of Tropical Medicine and Parasitology, 21, 155-163.
Admission to the Fellowship of the Society All registered medical and veterinary practitioners and others interested in scientific pursuits relating to tropical medicine, whose qualifications are deemed satisfactory by the Council, are eligible for election as Fellows of the Society. The annual subscription payable by Fellows is f15.00 which becomes due in advance on the 1st April of each year. The Transactions and the current Year Book of the Society are posted regularly to every Fellow whose subscription is not in arrear. Further information may be obtained from the Hon. Secretaries, Manson House, 26 Portland Place, London WlN 4EY, or from the Local Secretary of the district.
DISEASE
Thomas, T. D. L. (1966). Hydatid disease: an epidemiological study of hydatid disease in Wales. M.D. Thesis. Liverpool
University.
Trejos, A., Szyres, B. & Marchevsky, N. (1975). Comparative value of arecoline hydrobromide and bunamidine hydrochloride for the treatment of Echinococcus granulosus in dogs. Research in Veterinary Science, 19, 212-213. Walters, T. M. H. (1975). Unpublished data. West. L. R. (1960). Hvdatid disease in South Wales. Proceedings ~of the Royal
Society
of Medicine,
53,
1056-1060. Williams, B. M. (1976a). The epidemiology of adult and larval (tissue) cestodes in Dyfed (U.K.). 1. The cestodes of farm dogs. Veterinary Parasitology, 1, 271-276. red fox in south-west Wales. British Veterinary Journal, 132, 309-3 12. Williams, B. M. (1976b). The intestinal parasites of the red fox in south-west Wales. Research in Veterinary Science, 19, 212-213.
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Hydatid disease in Wales T. M. H. WALTERS Ministry of Agriculture, Fisheries and Food, ’ BeI,rave’, Spa Road. Llandrindod Wells, Powys. L DI 5HA
Hydatid disease is caused by the cystic larval stage of the cestodes Echinococcusgranulosus and E. multilocularis. The latter is thought not to occur in the U.K. E. grunu/OJ~LYexists as two distinct forms with different host species. The adult tapeworm lives in the intestinal tract of the definitive host and the cystic larval stage in organs such as the liver, lungs and brain of the intermediate host which is a different species. The incidence of hydatid disease varies in different parts of the world. The condition necessary to produce the disease is that the parasite should be freely circulated between the definitive and intermediate hosts; human hydatid disease will occur when man becomes interposed in this cycle by living in intimate contact with the definitive host, usually dogs. The explanation of the variable frequency of adults and larvae is always to be found in the different occupations and modes of life of the hosts (LEUCKART,1886; FOSTER,1965). Today hydatid disease is a medical and, to a lesser extent, an economic agricultural problem on all the inhabited continents. Epidemiological studies usually have as their object the elucidation of facts about the disease which are essential to its control in a particular country or region. A multiplicity of host, environmental and agent factors accounts for differences in the observable patterns of distribution of the parasite and its transmission in different areas. As with other infections, knowledge of these factors is necessary to identify vulnerable points for practical attacks (SCHWABE,1969). This study has been conducted in the Welsh border area where it is believed there is the highest incidence of hydatid disease in the U.K. and it is in Wales, and this area in particular, that the disease situation will be considered. Life-cycle of E. granulosus in Wales E. gr’anulosus is a cestode 3-9 mm in length, consisting of three or four proglottides. The terminal segment is gravid and is the broadest and longest. The dog and fox are the normal definitive hosts. Eggs free or released from segments passed in the faeces are picked up by cattle, sheep, horses and pigs on pasture or from the water supply to which they may be carried by the wind. Man can be infected by ingesting eggs attached to inadequately washed vegetables or accidentally picked up by handling a dog. It is also possible that flies may carry eggs to uncovered food or that they may be inhaled in dust (SOULSBY,1968). The eggs, once ingested by the intermediate hosts, hatch in the intestine, liberating oncospheres which penetrate the wall of the intestine and pass to the liver by way of the hepatic portal system. They may remain there or some may pass to the lungs and other parts of the body and develop into.hydatid cysts. Brood capsules
containing protoscoleces develop in the cysts and after five or six months are capable of producing infection in the definitive host. Prevalence of E. granulosus in the definitive hosts It is not possible to differentiate the eggs of E. granuIOSLLS from those of other taeniid cestodes which may be present. To establish that a dog is infected it is necessary to administer a drug (usually arecoline acetarsol or arecoline hydrobromide) which will remove the worms from the small intestine and cause them to be purged fairlv raoidlv whilst still intact and identifiable. Postmortem examination of dogs and foxes will also enable infected animals to be identified. In the U.K. information on the prevalence of E. grarzulosus in dogs has been limited to surveys carried out during the past 50 years. The results of some of these surveys are shown in Table 1. These results show that there is a high infection rate in Wales; COOK(1964) found 23 % of farm dogs he examined in mid-Wales to be infected. A recent survey in the same area confirms the high rate of infection in farm dogs. In this survey of 134 farms it was found that 126 (25:‘:;) of 509 dogs on 70 (52”/,) were infected (WALTERS,1975). From the purged faeces of the 126 infected dogs over 100 E. gvanulosus were collected from 47 (377/,) of the samples. These figures are low because it is unlikely that arecoline acetarsol removed all the worms or that all the worms which were purged were collected. Arecoline hydrobromide is effective as a diagnostic agent in only half of the infected animals (TREJOSet nl., 1965; GEMMELL, 1968). The red fox (Vulpes vulpes) is a definitive host for E. gramdosus and results of post-mortem examination of foxes from two areas of England and from Wales are shown in Table II. The relatively high prevalence of fox infection has been confirmed by a survey carried out during 1975 in mid-Wales when 12 (9 %) of 127 foxes were found to be infected (WALTERS,1975). At autopsy most worms are recovered from the small intestines. Fewer worms were present in the foxes than in the farm dogs, seven of the 12 infected foxes having less than 30 worms (WALTERS,1975). Prevalence of hydatid cysts in the intermediate hosts in the U.K. The infection rates in the intermediate hosts (cattle, sheep and pigs) in the U.K. is obtained by analysing the records kept by slaughterhouses. BLAMIRE (1966), from records kept by 30 slaughter-houses in the U.K., concluded, that 0.5 7: of cattle, 1.O% of sheep and 0.06 ‘A of pigs harboured hydatid cysts. The annual loss to the meat industry as the result of the condemnations of offal was about &55,000 in 1967 and figures collected by the Ministry of Agriculture, Fisheries and Food from 60 slaughterhouses are shown in Table III.
106
SYMPOSIUM
Table I - The prevalence of E. grunulosus --
ON HYDATID
DISEASE
in dogs in the UK
Number of dogs examined
Locality
Reference
Birmingham Birmingham Not stated Lake District Aberystwyth South Wales South Wales mid-Wales mid-Wales Dyfed, Wales
Brailsford (1926) Malcolm quoted by Southwell (1927) Skulski quoted by Miller and Poynter (1956) Cook and Clarkson (1971) Lewis (1927) West (1960) Cook and Crewe (1963) Cook (1964) Walters (1975) Williams (1976a)
Number and percentage of dogs infected
100 some hundreds 200 112 59 50 21 87 509 396
4 (3.6%) 3 (5%) 4 (8%) 2 (10%) 20 (23%) 126 (25%) 50 (12.6%)
Number of foxes examined
Number and percentage of foxes infected
0
: (2%)
Table II - The prevalence of E. granulosus in foxes in the UK
Locality
Reference Cook (1965) Cook (1965) Sinclair (1956) Sinclair (1957) Cook (1965) Cook (1965) Cook (1965) Walters (1975) Williams (1976b) Table III - Condemnations
North West England East Anglia mid-Wales mid-Wales North Wales mid-Wales South Wales mid-Wales Dyfed, Wales
90 73 16 89 29 63 8 127 149
; yw,’ 6 0 5 15 2 12 4
(3;&) (17%) (25%) (25%) (9%) (2.7%)
of offal in the U.K. because of hydatid disease. Figures collected from 60 slaughterhouses
Year
Number and percentage of cattle involved
Number and percentage of sheep involved
1973 1974 1975
6,241 (2.5 %) 5,732 (1.3 %) 7,855 (1.5 %)
30,274 (3.4 %) 32,586 (2.4%) 50,113 (3.3%)
Number and percentage of pigs involved 123 (0.01%) 70 (0.006 %) 86 (0.006 %)
Table IV - Prevalence of hydatid disease in sheep slaughtered in the U.K.
Reference Cook (1965) Cook Cook Cook Cook Blake
(1965) (1965) (1965) (1965) (1973)
Number of sheep examined
Locality Lake District and North Pennines Cheshire and Shropshire North Wales mid-Wales South Wales mid-Wales
When these figures are compared with the condemnations of offal from animals from specific areas and particular slaughterhouses, a much higher infection rate occurs in animals known to originate from the WelshEnglish border areas. The age of the animal at slaughter is also important: in a survey in a mid-Wales slaughterhouse BLAKE (1973) found very few hydatid cysts in 17,000 lambs slaughtered, whereas 123 (37%) of 326 adult sheep were infected. The results for specific areas are shown in Table IV, but they do not give an accurate figure for the local prevalence since few animals are slaughtered in the area where they were born and reared. Sheep from Wales are sold to many areas of England and Scotland and are slaughtered at abattoirs throughout Britain.
3,057 1,642 4,806 3,295 184 326
Number and percentage of sheep infected 130 (4.2%) 81 (4.9%) 755 (15.7%) 177 (5.4%) 28 (15.2%) 123 (37%)
Prevalence of hydatid disease in man in the U.K.
Since hydatid disease is not notifiable in the U.K. its incidence in man is not accurately known. HOWELL (I 940) reported that for the period 1927/36 there were 144 cases of hydatid disease, 30 of which were fatal. These figures, based on the records for Welsh hospitals, included three cases from one household in 1934. HOWELL comments that it is impossible to assess the amount of infection among man in Wales because post-mortem examinations are not done as a routine. When such examinations are carried out it is by no means uncommon to find hydatid cysts in the organs although there were apparently no symptoms present during life. JONATHAN (1960) reported on 44 cases being treated in the North Wales area during the period 1948-57 but the hospital records only extended back over a five-year period.
107
T.M.H.-WALTERS
The Registrar General’s returns for England and Wales for the period 1940-60 give the average number of deaths from hydatid disease as 15 per annum, or 0.37 per million of the estimated population, and for 1960-70 the average numbers were eight per annum or 0.14 per million. The figures for Wales alone for 1948-65 were 1.52 per million. THOMAS (1966) found that during the IO-year period 1953-62 there had been 216 persons resident in Wales in whom hydatid was diagnosed. In most cases the diagnosis had been made as the result of routine investigations but in a small number of cases the diagnosis was made after death. Cases diagnosed in rural areas had a definite connection with farming and with dogs but for most urban dwellers it was not possible to establish a definite relationship with dogs. Inquiries regarding all the children included in the survey established that all except two had had, from infancy, a close relationship with dogs. Discussion Hydatid disease is neither a major public health problem of nor the cause of spectacular economic loss to agriculture in the U.K. There are parts of Wales, particularly the Welsh-English border area, where the prevalence of infection in dogs and sheep has been shown to be much higher than elsewhere. THOMAS (1966) found that hydatid disease in man occurs in every county of Wales but particularly in the recognized sheep-rearing areas. Only one of the 216 cases occurred in Pembrokeshire and two in Cardiganshire, equal to 0.1 per 10,000 of the population, whereas in Radnorshire and Breconshire the rate was 4.7 and 6.3 per 10,000. COOK (I 964) suggested that some 70 % of the farming population in mid-Wales are exposed to infected dogs. In 1975, dogs on over 50 :( of the farms visited in the same area were infected, so that virtually all the farming population is likely to be at risk from their own or their neighbours’ dogs. The sheep is the most important intermediate host and becomes infected when grazing pasture in the immediate vicinity of farm buildings, which has become contaminated by eggs of E. granulosrrs passed by the farm dogs. The dogs in their turn become infected by being fed raw offal from infected sheep or by scavenging sheep which have died on the hill grazings. THOMAS (1966) found that cases of hydatid disease in man in rural areas had a definite connection with farming and with dogs. In the early 19th century Iceland had the highest prevalence of hydatid disease in man ever recorded anywhere. A campaign, which included the treatment of dogs and made it illegal to feed them raw offal, was begun in 1863 (DUNGAL, 1957). At the same time there was an educational campaign on the dangers and on control methods. In the last 20 years only 15 infected sheep have been found at slaughter and there have been no reports of infected dogs (PALSSON, 1972). In New Zealand the National Hydatids Council was set up in 195s to co-ordinate control of hydatid disease. As in Iceland, the anthelmintic treatment of all dogs and a campaign to prevent them from gaining access to raw infected offal were the important principles of the control scheme. The prevalence of E. granulosus in dogs has been reduced from 37% in sheep dogs which were being fed offal (GEMMELL, 1958) to 0.35% in all dogs tested during 1972-73. The Ministry of Agriculture and Fisheries survey at freezing works throughout New Zealand, reported that in 1962, 57 7: of sheep livers were
infected with hydatid: this figure had fallen to 24:< by 1972. Both these countries have shown that even before the new anthelmintics which are now available, it has been possible to reduce the incidence of hydatid disease by informing dog owners of the dangers of the disease and the most important principles of control. It would be valuable to obtain information on the prevalence of infection in dogs in different areas of Wales, with a view to recommending procedures for controlling the infection in areas where man is likely to be exposed to a considerable weight of infection. References Blake, J. (1973). Personal communication. Blamire, R. V. (1966). The diseases most commonly found in abattoirs. Veterinary Annual, 7, 310-316. Brailsford, J. F. (1926). The X-ray diagnosis of animal parasites (helminths) in man. Proceedings of the ROJ~ Society of Medicine, 19 (Section Electrotherapeutics), 41-52. Cook, B. R. (1964). The epidemiology of Echinococcus infection in Great Britain. 11. The incidence of Echirzococcns granulosus and some other cestodes in farm dogs in mid-Wales. Am& r?j” Tropical Medicine and Parasitology,
58,147- 152.
Cook, B. R. (1965). The incidence and epidemiology of Echinococcus in Great Britain. Ph.D. Thesis, Liverpool Ukver.sifJ~.
Cook, B. R. & Clarkson, M. J. (1971). The epidemiology of Echinococcus infection in Great Britain. 111. EchinoCOCCI~S granulosus and cestodes of the genus Taenia in farm dogs in England in the Lake District, northern Pennines and East Anglia. Amzals of Tropicul Medicine and Parasitology,
65, 71-79.
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Cook, B. R. & Crewe, W. (1963). The epidemiology of Echinococcus infection in Great Britain. I. Abnormal behaviour of sheep in the mining valleys of South Wales and its relation to hydatid disease in man. Annals
of Tropicul
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150-156. Dungal, N. (1957). Eradication of Echinococcus in Iceland. New Zealand Medical Journal, 56, 212-222. Foster, W. D. (1965). In: A history ofparasitology. W. D. Foster (Ed.). Edinburgh & London: E. and S. Livingstone, pp. 50-51. Gemmel. M. A. (1958). Cestode problem of domestic animals and man in ihe South Island of New Zealand. New Zealand Medical Journal, 57,442458.
Gemmell, M. A. (1968). Screening of drugs and their assessment for use against the strobilate stage of Echinococcus. Bulletin tion, 39, 57-65.
of the World Health
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Howell. N. (1940). Hvdatid disease in Wales. Vetrritmrv Recoid, 5i, 49i-506.
Jonathan, 0. M. (1960). Hydatid disease in North Wales. British Medical Journal, i, 1246-I 253. Leuckart, R. (1886). The parasites of rnu~~, p. 641. (Translated by W. E. Hoyle, Pentland, Edinburgh.) Lewis, E. A. (1927). A study of the helminths of dogs and cats of Aberystwyth, Wales. Journal of Helminthology, 5, 171-182. Miller, W. C. & Poynter, D. (1956). Hydatid cysts in a thoroughbred mare. Veterinary Record, 68,51-53. NationalHydatids Council (1973). 13th Annual Report and Statement of Accounts. National Hydatids Council, Wellington, New Zealand.
108
SYMPOSIUM
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Palsson, P. A. (1972). Unpublished. Quoted in: Beard, T. C. (1973). The elimination of echinococosis from Iceland. Bulletin of the World Health Owanization. I 48.I 653-660. ” Schwabe, C. W. (1969). Principles of epidemiology: case study of hydatid disease. In: Veterinary medicine and human health. (2nd edit.). London: Baillibre, Tindall and Cassell, pp. 251-263. Sinclair, K. B. (1956). Echinococcus infection in the fox. Veterinary Record, 68, 104. Sinclair, K. B. (1957). Echinococcus infection in the fox. Veterinary Record, 69, 1076. Soulsby, E. J. L. (1968). In: Helminths, arthropods and Protozoa of domesticated animals. Monnig’s Veterinary helminthology and entomology (6th edit.), E. J. L. Soulsby (Ed.). London; BailliBre, Tindall and Cassell, pp. 126-141. Southwell, T. (1927). Experimental infection of the cat and the fox with the adult Echinococcus. Annals of Tropical Medicine and Parasitology, 21, 155-163.
Admission to the Fellowship of the Society All registered medical and veterinary practitioners and others interested in scientific pursuits relating to tropical medicine, whose qualifications are deemed satisfactory by the Council, are eligible for election as Fellows of the Society. The annual subscription payable by Fellows is f15.00 which becomes due in advance on the 1st April of each year. The Transactions and the current Year Book of the Society are posted regularly to every Fellow whose subscription is not in arrear. Further information may be obtained from the Hon. Secretaries, Manson House, 26 Portland Place, London WlN 4EY, or from the Local Secretary of the district.
DISEASE
Thomas, T. D. L. (1966). Hydatid disease: an epidemiological study of hydatid disease in Wales. M.D. Thesis. Liverpool
University.
Trejos, A., Szyres, B. & Marchevsky, N. (1975). Comparative value of arecoline hydrobromide and bunamidine hydrochloride for the treatment of Echinococcus granulosus in dogs. Research in Veterinary Science, 19, 212-213. Walters, T. M. H. (1975). Unpublished data. West. L. R. (1960). Hvdatid disease in South Wales. Proceedings ~of the Royal
Society
of Medicine,
53,
1056-1060. Williams, B. M. (1976a). The epidemiology of adult and larval (tissue) cestodes in Dyfed (U.K.). 1. The cestodes of farm dogs. Veterinary Parasitology, 1, 271-276. red fox in south-west Wales. British Veterinary Journal, 132, 309-3 12. Williams, B. M. (1976b). The intestinal parasites of the red fox in south-west Wales. Research in Veterinary Science, 19, 212-213.
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