Epidemiological Field Studies Research Articles

Pattern analysis of epidemiological variables applied in the study of weanling diarrhoeal disease

The need for and requirements of a computer-based pattern analysis approach to the investigation of longitudinal epidemiological records have been considered; it is argued that the objective specification of relevant variables is of first priority. The development and implementation of suitable techniques is reported in context of a continuing study of a large-scale international epidemiological problem-weanling diarrhoeal disease of infants.These techniques have been used for the objective specification of variables measured in an epidemiological field study of an ensemble of 139 weanling infants followed for the first two years of life; rationale, methods, and results are reported here for the simplest of the available variables-the daily defaecation rate (or diarrhoeal signal, DS).Two separate detailed findings have emerged. Three patterns of spontaneous defaecation behaviour have been confirmed and located objectively by a numerical matched filter method; their occurrence statistics were compiled and ...

Antithyroid compound(s) produced by Escherichia coli: preliminary report.

ABSTRACT This series of experimental studies was prompted by several epidemiological field studies of endemic goiter which demonstrated a relationship between bacterial pollution of drinking water and the prevalence of endemic goiter. An in vivo assay for antithyroid activity in the rat was developed. Antithyroid activity was demonstrated in cell-free, lyophilized, broth cultures of four species of organisms. The most consistent producer of antithyroid activity was E. coli and the material was partially purified by ultrafiltration. Dose response studies demonstrated antithyroid activity with known goitrogens and a satisfactory dose response was obtained from various fractions following ultrafiltration. However, based on estimated molecular weights of filtrates, antithyroid activity varied between batches but it was consistently present. The significance of this research is briefly discussed and further experimental work towards purification of the compound and demonstration of its mechanism of activity in...

Life events and psychiatric impairment.

This is a report on relationships between life crises and psychiatric impairment in a community sample of 938 adults in New Haven, Connecticut.It is part of a longitudinal study of the population of a community mental health center catchment area. The theoretical framework for the paper finds its roots in two bodies of socio-medical literature, namely, stress research and epidemiological field studies of mental illness. The specific research question is to determine whether or not there is a relationship between the occurrence of life events, the patterning of such events and the degree of psychological impairment. As in other field studies, we discovered a significant amount of psychiatric impairment in the community. Eighteen per cent of the adults interviewed were classified as having a high symptom level (very impaired), 47 per cent as a medium symptom level (moderately impaired), and 35 per cent as a low symptom level (unimpaired). More important, we found significant relationships between these scores and the occurrence of life events in the year previous to our interview. First, the greater the degree of impairment the more likely is the individual to have experienced at least one of 62 life events for which we gathered information. Equally important, there is a very strong association between the number of events experienced and the individual's mental status: the greater the number of events reported by respondents, the greater the proportional difference between the percentage of unimpaired and the percentage of very impaired who experienced that number of events. When events are categorized according to type of social activity, changes in the respondent's social field and degree of desirability impairment are strongly and positively related to the experiencing of life crises. Finally, similar patterns are found for each of the individual life events with the exception of several biopsychosocial situations associated with the family developmental cycle.Certain cultural and social factors, particularly role expectations and values, are discussed as possible factors helping to account for the relationshipsfound above between life crises and psychiatric impairment.

Nutrition and infection field study in Guatemalan villages, 1959-1964. I. Study plan and experimental design.

A prospective 5-year epidemiological field study (1959-1964) of nutrition and infection in children less than 5 years old in Guatemalan villages is described. Attention is directed to the following: the background (death rates disease incidence synergism of infection and nutrition age of attack and exploratory studies of nutrition and infection); and study plan (a longitudinal investigation experimental design and study objectives). Recorded deaths from nutritional disease are few and often are absent from offical lists. This is the case despite a prevailing malnutrition at childhood ages of such an extent that as many as 85% of village children aged 1-4 years have a deficiency in weight for their age more than 10% below the mean for middle-class families. A field study of deaths among children of 4 rural Guatemalan communities showed that 2/5 of those dying at ages 1-4 years had the signs and symptoms of kwashiorkor yet only 1 death at any age up to 15 years was listed officially as due to malnutrition. As the general result is that causes of death remain highly indefinite the preferred method is the direct survey of cases and deaths using the principles and techniques of field epidemiology. A synergism frequently exists whereby infectious disease has the capacity to precipitate an acute nutritional disease in persons of borderline nutritional status; conversely persons with manifest nutritional deficiency commonly experience a severity and frequency of infection beyond ordinary expectation. In nearly all less developed countries the incidence of both infectious disease and malnutrition is greatest among children under 5 years of age. The experimental design finally adopted combines the advantages of longterm epidemiological observation of a natural population (the control) and those of a direct controlled experiment to test specific hypotheses. The formally stated objectives of this longterm prospective epidemiological study of malnutrition and infectious disease in rural Guatemalan communities were as follows: to observe and describe the interactions of malnutrition and infectious disease among infants and young children through the 5th year of life in a rural population of a developing country where both classes of disease were highly prevalent; to measure the changes in nutritional status resulting from addition of supplementary food to the diet of breastfed children; to measure the results of integrated medical services; and to identify and evaluate the relative influence of other broad ecological factors involved in the frequency and severity of infectious and nutritional diseases of early childhood in rural populations of a developing country.

COMPARABILITY OF A SAMPLE OF CERTIFIED SCHIOTZ TONOMETERS. WITH AN EVALUATION OF THE POTENTIAL INFLUENCE OF TONOMETER VARIABILITY ON THE OUTCOME OF EPIDEMIOLOGIC FIELD STUDIES.

Introduction Any attempt to determine the prevalence of glaucoma with sufficient accuracy to permit legitimate geographic comparisons will require carefully standardized instruments and procedures. For such epidemiologic field studies the use of tonometers of established precision is a preliminary and fundamental requirement. Inconsistency among the recordings obtained from various Schiotz indentation tonometers has led to attempts to establish acceptable manufacturing tolerance. Largely through the extensive efforts of the Committee on Standardization of Tonometers of the American Academy of Ophthalmology and Otolaryngology, there has been considerable improvement in the uniformity of available instruments. Still, it is suggested that residual inconsistencies may exist in theory 1 and in fact. 2-4 Since the Epidemiology Branch of the National Institute of Neurological Diseases and Blindness proposes quantitative field investigations of the relative frequency of chronic simple glaucoma among selected populations, an examination of the comparability among a sample of Schiotz tonometers was undertaken. The

GROWTH ON ARTIFICIAL MEDIUM OF AN AGENT ASSOCIATED WITH ATYPICAL PNEUMONIA AND ITS IDENTIFICATION AS A PPLO

Recent volunteer and controlled epidemiologic field studies have provided evidence which firmly associates the agent first recovered by Eaton in 1944 with lower respiratory tract illness of man.1-3 A serologic response to the Eaton agent occurs in approximately 90 per cent of pneumonia illnesses in which cold agglutinins develop during convalescence as well as in a significant but variable proportion of cold agglutinin-negative pneumonias.2 4 The development of pneumonia and other forms of respiratory disease following the administration of tissue culture-grown Eaton agent to volunteers and the demonstration that naturally acquired antibody offered protection against such illness supports the contention that the agent is a respiratory tract pathogen.5 For many years, the agent was tentatively classified as a virus. The large size of the agent (180-250 m,i) and its sensitivity to streptomycin and various tetracycline derivatives, however, posed some difficulty with such a classification.6-8 Recently, Marmion and Goodburn were able to visualize small cocco-bacillary bodies on the mucous layer covering the bronchial epithelium of the Eaton agent infected chick embryo.9 The distribution of these bodies corresponded with the localization of Eaton agent as visualized by the fluorescent antibody technique. These workers also demonstrated that the Eaton agent was inhibited by an organic gold salt. Clyde visualized extracellular colony-like structures in stained preparations of infected tissue culture; these structures corresponded with the areas of specific immunofluorescence.U? Both groups of workers suggested the possibility that the Eaton agent may be a pleuropneumonia-like (PPLO) rather than a virus. Cultivation of the organism in cell-free media, however, was not achieved. T

The Mode of Transmission of Poliomyelitis

From a practical point of view the mode of transmission is the most useful single factor in combating a disease. The health officer would prefer to know the precise mode or modes of transmission of any disease rather than its cause, or pathologic anatomy, or even its treatment. Hence a large amount of work has been done to determine how the virus of poliomyelitis leaves the body, how it enters its victim, and theroute it takes from one person to the next. Despite all the thought and work that has been focused on this problem, the mode of transmission of poliomyelitis remains an open chapter, and although much light has been thrown on the subject, the present state of our knowledge does not permit of dogmatic, much less final statements. There are two avenues of approach to a problem of this sort; one, through epidemiologic field studies, and the other

THE MODE OF TRANSMISSION OF POLIOMYELITIS

From a practical point of view the mode of transmission is the most useful single factor in combating a disease. The health officer would prefer to know the precise mode or modes of transmission of any disease rather than its cause, or pathologic anatomy, or even its treatment. Hence a large amount of work has been done to determine how the virus of poliomyelitis leaves the body, how it enters its victim, and theroute it takes from one person to the next. Despite all the thought and work that has been focused on this problem, the mode of transmission of poliomyelitis remains an open chapter, and although much light has been thrown on the subject, the present state of our knowledge does not permit of dogmatic, much less final statements. There are two avenues of approach to a problem of this sort; one, through epidemiologic field studies, and the other