1314

Although the treatment of dementia is the best known aswell as the most controversial indication, hydergine is widelyprescribed in many countries for peripheral vascular diseaseand for hypertension. In France and Italy, about one-third ofthe prescriptions are for use as a hypotensive. While theefficacy of hydergine in peripheral vascular disease is

questionable, it does seem to be a safe and effective

antihypertensive agent, particularly in the elderly. 11,12Hydergine may also be effective in some patients with tardivedyskinesiay,14 In the United Kingdom the data sheet forhydergine gives its sole indication as "an adjunct in themanagement of mild to moderate mental impairment in theelderly". The obvious question is, should the drug beprescribed to these patients? It is frustrating that, after 30years and many trials, the answer is still not clear. For

instance, direct comparisons of hydergine with

antidepressants would be valuable. It is unlikely in theextreme that hydergine, or any other existing drug, willgreatly alter the quality of life of a severely demented elderlypatient. Even in those less severe affected, cure is out of thequestion; and this should be made very clear to the patients’relatives before the question of drug treatment is even raised.Therapeutic objectives must therefore be rather modest, andmany doctors may feel that they do not warrant the cost oftherapy or the, admittedly small, risk of side-effects. Others,however, will judge that a course ofhydergine, at least 4’ 5 mga day, probably for at least 3 months, is justified. Patientswith multi-infarct dementia may be less likely to benefit thanthose with Alzheimer’s.]5 Even if, as many believe, the effectof the drug is on mood rather than on cognition, the benefitsto the patients and their families may still be worthwhile. Wemust add that other drugs, such as naftidrofuryl and

pentoxyifylline, have shown promising results in clinicaltrials, though the evidence is not as extensive as that for

hydergine.16

VETERINARY EPIDEMIOLOGY AND HUMANDISEASE

EPIDEMIOLOGICAL observations on domestic animals havebeen important in the study of human infections and dietarydeficiencies. Now they are beginning to give clues to theenvironmental causes ef cancer.The inhabitants ofHenan Province in northern China have

an unusually high incidence of oesophageal cancer.’ Thatoesophageal tumours are also more common than expectedamong domestic chickens from the region suggests that thefocus is due to a feature of the environment which the birdsshare with their owners. Furthermore, migrants from Henanto the province of Hubei continue to experience high rates of

11. Bellani M, Meregalli M, Guffant E, Bartucci F, Fiurella G, Chierichetti SM, MazzulaC. Treatment of hypertension in the elderly: a controlled clinical trial of

Dihydroergotoxine mesylate in comparison with Nifedipine. Curr Ther Res 1983;34: 1014-22.

12. Wilbrandt R. Treatment of hypertension with Hydergine A review of 200 cases.Angiology 1953; 4: 183-89.

13. Hajioff J, Wallace M Effect of co-dergocrine mesylate in tardive dyskinesia. Apreliminary report. Psychopharmacology 1983; 79: 1-3.

14. Lancranjan I. New perspective in the treatment of tardive dyskinesia with

dihydroergotoxine. In: Agnoli A, et al, eds Ageing, vol 23: ageing brain and ergotalkaloids. New York: Raven Press, 1983: 329-38.

15. Fanchamps A. Dihydroergotoxine in senile cerebral insufficiency. In: Agnoli A, et al,eds Ageing, vol 23. ageing brain and ergot alkaloids New York: Raven Press, 1983:311-22

16. Yesavage JA, Tinklenberger JR, Berger PA, Hollister LE Vasodilators in seniledementias: a review of the literature. Arch Gen Psychiatry 1979; 36: 220-23.

1. Yang CS. Research on esophageal cancer in China: a review Cancer Res 1980; 40:2633-44.

oesophageal carcinoma after they have moved. This might bea late manifestation of tumours initiated before migration.However, the observation that chickens owned by the

migrants get oesophageal cancer more frequently than thosebelonging to natives of Hubei indicates that the explanationlies, at least in part, in the customs and practices which thepeople from Henan bring with them when they migrate.In Scotland and northern England alimentary cancer is

more common among beef cattle in upland areas than inadjacent lowlands.2 More specifically the geographicalvariation in incidence of papilloma and carcinoma of thealimentary tract in the cattle has been shown to correlate withthe density of bracken infestation of grazing land. Thesefindings heighten suspicions generated by laboratory studiesthat bracken may have a role in human carcinogenesis (viawater or milk).3A further example of a study of domestic animals with

possible implications for human carcinogenesis can be foundon p 1301 of this issue. In New Zealand, Dr Newell and hiscolleagues have related the prevalence of small-intestinaladenocarcinoma in sheep to their exposure to agriculturalchemicals. They report an excess of tumours in animals fedon pastures or crops recently sprayed with phenoxy and/orpicolinic acid herbicides, and suggest that heavy use of thesecompounds may be a factor in the high incidence of humanlarge-bowel carcinoma in New Zealand. In drawing thisconclusion they are rightly cautious. Phenoxy herbicideshave previously been linked with the occurrence of soft-tissuesarcomas and lymphomas in man, but not with cancer of thebowel. A Swedish case-control study of colonic carcinomashowed only a weak and statistically insignificant associationwith phenoxy acids.5 Potentially the most important findingof the New Zealand study is the similarity of the risksassociated with phenoxy herbicides which do or do notcontain 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as a

contaminant. If phenoxy herbicides are indeed carcinogenic,it will be important to establish whether the hazard arisesfrom the phenoxy acids themselves or from associated

impurities.Domestic animals have a more constant environment than

human beings, and their exposure to adverse influences in itmay therefore be more intense. Observations on them are lessconfounded by variations in behaviour. Because of economicinterest in the health of livestock and affection for household

pets, their illnesses do not go unremarked. Their potential asindicators of environmental hazards has not been lost on the

general public. Recent debate about the safety of a chemicalwaste disposal plant at Bonnybridge in Scotland was fuelledby stories of sickness among cattle grazing nearby.6 Potentiallinks to bring together medical research and veterinaryepidemiology already exist. For example, in Britain a Societyfor Veterinary Epidemiology and Preventive Medicine (honsec, Mr M. Thrusfield, Department of Animal Health,University of Edinburgh) was inaugurated in 1982. Althoughthere are obvious difficulties in extrapolating veterinary datato man, veterinary epidemiology is an under-exploitedresource in the investigation of human disease.

2. Jarrett WFH. Bracken fern and papilloma virus in bovine alimentary cancer Br MedBull 1980; 36: 79-81.

3. Wang CY, Chiu CW, Pamukcu AM, Bryan GT. Identification of carcinogenic tanninisolated from bracken fern (Pteridium aquilinum). J Natl Cancer Inst 1976, 56:33-36

4. Coggon D, Acheson ED. Do phenoxy herbicides cause cancer in man? Lancet 1982; i.1057-59.

5. Hardell L. The relation of soft tissue sarcoma, malignant lymphoma and colon cancer tophenoxy acids, chlorophenols, and other agents. Scand J Work Envir Health 1981,7: 119-30.

6. Clough P Dioxin a formula for conflict. Times, Sept 14, 1984, p 18.