C. E. Gordon Smith

The epidemiology of louping ill in Ayrshire: the first year of studies in sheep

Following an outbreak of louping ill in lambs on a hill farm (C!amlarg) near Dalmellington, Ayrshire, a study was made of the epidemiology of the disease on three neighbouring farms (Mossda.le, Dalcairnie, Knockgray shaded in Fig. 1). The affected area was that in which Gordon, Brownlee, VVrilson & Macleod (1932) and Gordon (1934) did much of the original investigation into louping ill infection of sheep. These workers developed a formalinized sheep brain vaccine which has been used prophylactically in louping ill areas of the British Isles ever since. Generally, lambs are vaccinated once during the second 6 months of their life a,nd this is the only artificial protection they receive. In the area studied, lambs are born on the hills in April and remain there until weaned in September. The male lambs are then sold off the farm and the female lambs (ewe hoggs) are sent to a tick-free lowland pasture (the wintering) from October until the following April. Generally speaking they return to the hirsel (an area of the hills confined naturally by hill burns, ravines, etc.) on which they were born and where they remain until they are sold as cast ewes at the age of 51-6 years. Black-face hoggs for Dalcairnie Farm are, however, born on Brownhill Farm some 7 miles away. Only cross-bred lambs are produced at Dalcairnie and a11 are sold in the autumn. The sheep on these farms are not mated (tupped) until November in their second year (as gimmers) after which they produce a lamb annually, usually for 4 subsequent years. This paper reports the first year of work in a long-term study of which further reports will follow. The first year of work in sheep was mainly on Dalcairnie Farm which has two hirsels (Dalcairnie Hill and Bajrbeth) separated only by a streaJm and a farm road. Barbeth forms roughly the southern one-third of the farm.

Antibodies to arthropod-borne viruses in Greece

In 1927 and 1928 an extensive epidemic of dengue occurred in Greece. About one million people were affected. THEILER et al. (1960) showed by a retrospective serological study that this epidemic was probably due to dengue-1 virus. The present study was undertaken to find out what other arbovirus (arthropod-borne virus) infections have been occurring in Greece. To eliminate the effect of cross reactions with group B viruses due to residual dengue-1 antibody, sera from persons born before and after 1928 were contrasted.

Arbovirus infections in Sarawak: serological studies in man.

Abstract 1. 1.2,118 human sera collected from all age groups in a wide variety of ecological zones in Sarawak during December 1962 and January 1963, April-May 1964 and September-December 1966, were tested for haemagglutination-inhibiting and neutralizing antibodies to 9 arboviruses. 2. 2.Japanese encephalitis and dengue virus antibodies were prevalent in all areas. The estimated annual infection rate with Japanese encephalitis virus varied from about 2% to over 9% with a mean of 6%. Estimated dengue virus infection rates varied from less than 1 % to over 11% with a mean of just over 5% per annum. 3. 3.There was only slight evidence of infection with group A, Bunyamwera and other group B arboviruses. 4. 4.No significant differences in the prevalence of arbovirus infections could be distinguished between any of the ecological zones. The wide distribution of Japanese encephalitis and dengue virus infections matched the distribution of the principal arthropod hosts of the viruses, C. tritaeniorhynchus, C. gelidus and Ae. albopictus . 5. 5.The general trend of arbovirus infections in Sarawak was of highest infection rates in coastal, estuarine and inland forest areas. Urban areas had the lowest rates while rural areas of settled cultivation had intermediate rates of infection.

Yellow fever in the north. The methods of early epidemiology

the field ofmedical education, beginning with its origins in the London hospitals and concluding with the ructions engendered by two reports on medical education, that of the Royal Commission chaired by Lord Todd (1968) and the internal one produced by Lord Flowers (1980). Harte is particularly illuminating on the changing relations between the medical schools and the University. Indeed, this is just one of the many benefits to be gained from this delightful, instructive, and amusing book, which will be widely enjoyed by specialists and common readers alike. Jack Morrell University of Bradford

Priorities for Medicine and Health in the Tropics

The problems of health and disease in tropical countries differ from those in the temperate zones in several important respects. It is by no means a question only of climate, nor of the parasitic and vector-borne diseases which are largely confined to the tropics and subtropics because their causative parasites require high ambient temperatures for development or because their vertebrate and/or invertebrate hosts are restricted to warm climates. Equally important are the social, nutritional, educational, and environmental factors characteristic of the poverty—both rural and urban—that afflicts the majority of the peoples of most tropical developing countries—poverty not only of income but also of public services and resources, and increasing in many areas because of galloping population growth in the face of slow and often faltering economic growth. In such circumstances, existing knowledge capable of improving health and controlling diseases cannot be effectively utilized, and further advances in knowledge from research will be equally ineffective unless they can be interpreted into economically feasible and socially, culturally, politically, and ecologically acceptable programs of action.

The London School of Hygiene and Tropical Medicine

The London School of Hygiene and Tropical Medicine is the University of London’s postgraduate school of international preventive medicine, community health, occupational medicine and hygiene, and tropical medicine. On a world-wide basis it seeks to develop and promote the application of science to the protection of populations from hazards posed by infections, by the physical environment and by human behaviour; to elucidate the aetiology, pathogenesis, diagnosis and epidemiology of acute and chronic diseases; and to promote health by contributions to the planning, medical management and evaluation of health services and of interventions designed to control or prevent diseases. In addition, the School’s denartments of Clinical Tronical Medicine and Human Nutrition are concerned with the care of patients and with treatment of their diseases. All these activities involve research, teaching (primarily of teachers, research workers and senior medical administrators) and participation in many service and advisory roles which provide active contact with current developments and problems. The School’s uniqueness, nationally and internationally, lies in the wide range of problems, of both industrialized and developing countries, in which it is interested and in its pattern of complementary disciplines which, together with appropriate resources from elsewhere in the University, enable it to offer a comprehensive approach to preventive medicine and community health world-wide. Studies of the aetiology and prevention of acute and chronic diseases as they affect communities and of optimal ways for their amelioration demand an understanding of the ecological, social, behavioural, demographic and economic aspects, as well as of the microbiological, parasitological, nutritional and epidemiological as ventive medicine and community P ects of prehea th. Thus its core departments are (i) those that can measure effects in demogra P hy , (ii) those concerned with laboratory P opulations (epidemiology, statistics,

Some often Neglected Factors in the Control and Prevention of Communicable Diseases

The control of a communicable disease depends on the reduction of ‘effective contact’ between infective and susceptible hosts — eradication requires that the frequency of ‘effective contact’ is reduced below some critical leval at which infective hosts become non-infective or die before having infected another. Effective contact describes the combination of circumstances in which there is a high probability of the transmission of any particular infection from an infective host to a susceptible one; the main relevant circumstances are: (1) the duration of infectivity in infected hosts; (2) the route(s) by which infection leaves them; (3) the stability of the infective micro-organism outside its hosts, in relation to environmental conditions; and (4) the route(s) of infection. The main factors controlling the frequency of successful contact (i.e. transmission) are the population densities of the hosts and the proportions of them which are susceptible to infection. In some infections the duration of infectivity can be reduced by treatment, not only of cases but of carriers. The routes by which infection is released define control measures such as sanitation for faecally transmitted infections, or the deep burying of anthrax-infected carcases. The stability of micro-organisms is more difficult to influence in most circumstances but in laboratories for example ultraviolet light can be used to disinfect air. The routes of infection offer different opportunities for control — for example safe water supplies, or the use of mosquito nets against malaria.