Epidemiological Reasons Research Articles

The Resistance of Falciparum Malaria in Africa to 4-Aminoquinolines and Antifolates

Falciparum malaria cannot be eradicated from sub-Saharan Africa with present technology. The mainstay of malaria control in this situation is treatment of fever cases with chloroquine, aiming principally at reduction of mortality. The efficacy of this policy is now endangered because of the appearance and spread of chloroquine-resistance on the African continent. The present review examines laboratory and field research on the resistance of African P.falciparum to chloroquine, amodiaquine, pyrimethamine, proguanil, chlorproguanil and the combination sulfadoxine-pyrimethamine. Drug-resistance in malaria may be assessed with in vivo and in vitro technology. In vivo tests are simple, but the results are difficult to compare because of the influence of immunity. In vitro tests provide a more precise epidemiological tool, but their analysis should be undertaken with consideration of their technical limitations. For parasitological, immunological and epidemiological reasons, a one-to-one correlation between in vivo and in vivo grading of resistance is usually not found. Extended in vivo tests may be at least as sensitive as in vitro tests for detecting rare resistant parasites. On the other hand, the standardized grading of higher levels of in vivo resistance is arbitrary, and it is doubtful, whether such distinction has any clinical relevance. The 4-aminoquinolines (chloroquine and amodiaquine) presumably act by interfering with vital functions in the acid vesicles of parasites. Recent experiments indicate that resistance may be related to an increased rate of efflux of chloroquine from the parasite. It is caused by mutation, and at least three genetic levels of resistance have been identified. The blood stages of resistant plasmodia seem to have a biological advantage over sensitive ones, an observation that raises some hitherto unanswered questions. In the 1970s, a low degree of resistance to chloroquine was found in African P. falciparum in several localities. Resistance to the standard dose of chloroquine of 25 mg/kg was found in 1978 in tourists, who had sojourned in Kenya and Tanzania. Since then, chloroquine-resistance has spread centrifugally with increasing rapidity from an original focus in Northern Tanzania or Southern Kenya. The rate of increase in the proportion of resistant infections has generally been more rapid in the areas, where resistance has been introduced recently than in the original epifocus. The rate of increase is also generally more rapid in urban than in rural areas, an observation that can be ascribed to differences in drug pressure.(ABSTRACT TRUNCATED AT 400 WORDS)

Clinical Features and Management of Severe Dermatological Reactions to Drugs

Cutaneous adverse drug reactions are a frequent occurrence and have been reported in more than 2% of hospitalised patients. Among the most commonly involved drugs are sulphonamides, penicillins, anticonvulsants and non-steroidal anti-inflammatory drugs. Two groups of mechanisms are involved in the pathogenesis of drug reactions: immunological, with all 4 types of hypersensitivity reactions described; and non-immunological, accounting for at least 75% of all drug reactions. Besides minor skin reactions like urticaria, maculopapular rash, fixed eruptions or erythema nodosum, which are generally self-limited, severe life-threatening manifestations also occur. Erythema multiforme is secondary to drugs in half the cases; the minor form is characterised by typical target and iris lesions and is usually benign. However, a much more severe condition, erythema multiforme major or Stevens-Johnson syndrome, is associated with mucosal, ocular and visceral involvement, and carries a mortality of 5 to 15% if untreated. Toxic epidermal necrolysis, which could represent an even more dramatic form of the same disease, is characterised by severe widespread erythema, blisters and loss of skin in sheets, with denudation of more than 10% of the body surface area. This entity is frequently due to drugs. Mortality is 25 to 70%, and 90% of the survivors will have sequelae. Exfoliative dermatitis is an erythematous scaling disease often produced by drugs and carrying significant mortality. Photodermatitis may at times present with severe eczematous features. For clinical and epidemiological reasons it is important to try to identify the culprit drug following an approach based on previous experience with the drug, timing of events, patient reaction to dechallenge, patient reaction to rechallenge (if feasible), alternative aetiological candidates, and drug concentration or evidence of overdose. Management of severe skin reactions to drugs should require admission to a burn unit, where patients should be placed in warmed air-fluidised beds, receive excellent nursing care, analgesics and tranquillisers. Peeling necrotic epidermis should be removed and denuded dermis covered with biological grafts or synthetic dressings. Fluid balance must be adequately maintained; nutritional support and careful monitoring of early signs of skin infections is mandatory to ensure immediate antimicrobial treatment. Ocular care must be excellent to avoid serious sight-threatening sequelae. Steroids are presently not recommended. With these therapeutic modalities, morbidity and mortality can be markedly decreased.

Neurotoxic concerns of human pesticide exposures

While the human effects of acute pesticide poisoning are well known, significant data gaps exist with regard to what is known about some of the chronic effects, particularly neurotoxic and behavioral aspects of organophosphate exposures. The extent of this concern is particularly high in Europe where these issues are being addressed by the World Health Organization and the United Nations Development Programme. These agencies are sponsoring a ten-nation, international study of chronic neurologic and neurotoxic sequelae. In the United States, evidence for chronic neurologic effects have come from case studies, clusters of neurologic disease, or from specific epidemiologic studies. For both toxicologic and epidemiologic reasons, it is essential that the neurobehavioral potential of low-level, prolonged exposure to pesticides and pesticide mixtures be more thoroughly investigated. Workers exposed to pesticides are one of the largest occupational populations at risk in the world. The effects of these occupational exposures on the worker's nervous system and behavior are just beginning to be investigated.

Has sexual behaviour really changed with time?

SummarySexual behaviour is probably extremely stable. What changes from time to time is the degree of social pressure to conform to a particular public image. It is therefore impossible to judge the actual range of private behaviour in the past from written sources. Our generation is possibly the first able to assess this range by surveys. It is important for medicine to be aware of the prevailing diversity both for epidemiological reasons and to avoid nonsensical prescriptions such as those which attributed mental disorder to masturbation. Our growing awareness of the natural history of human sexual behaviour is an important therapeutic and prophylactic asset.

Phage‐typing of coagulase‐negative staphylococci. Factors influencing typability

Factors influencing the phage-typability of coagulase-negative Micrococcaceae have been studied in 2,778 clinical isolates comprising A) 209 consecutive isolates from one laboratory, B) 2,107 clinical strains submitted for phage-typing for epidemiological reasons, and C) 462 strains representing all isolates of presumed clinical significance found in two laboratories during one month. The reproducibility was acceptable at duplicate repeated typing of the same strains as well as by typing epidemiologically-related pairs of strains from the same patient. Strains of Staphylococcus haemolyticus were seldom typable, whereas strains of S. epidermidis and S. hominis had a higher typability. Methicillin-resistant strains and other multiple-resistant strains were rarely typable (11-13%). The typability was higher among susceptible strains (36%) and strains resistant to penicillin only (43-50%). The typability of strains of the same species and antibiotic-resistance pattern differed between hospitals compared and decreased markedly over the years for multiple-resistant S. epidermidis isolates.

Government issues guidelines to stem rising tuberculosis rates in prisons

IN RESPONSE to the alarming increase of tuberculosis (TB) rates in many of the nation's prisons, the Centers for Disease Control (CDC), Atlanta, Ga, has published recommendations for the prevention and control of TB among prison populations ( MMWR . 1989;38:313-320,325 and this issue.) This is the first time the CDC has issued guidelines regarding health care in correctional institutions. Speaking at the 13th National Conference on Correctional Health Care in Chicago, Ill, John J. Seggerson, Jr, MD, chief, Program Services Branch of the CDC's Division of Tuberculosis Control, explained the epidemiologic reasons for the recommendations. Eleven Known Outbreaks Over the last few years, increasing rates of TB in certain demographic pockets have brought the decline in the incidence of TB in the United States to a halt. Since 1985, 11 known TB outbreaks have occurred in prisons in eight states, Seggerson says. One such outbreak was described at the conference by

Epidemiologia y contrahegemonia

The innovation of epidemiology plays a crucial role in the development of the health sciences. The authors emphasize the importance of epistemological analysis related to scientific and technical production. They focus on the theoretical and methodological contributions of the principal Latin American groups in the field of epidemiology, stating their main accomplishments, issues and potentials. When reviewing those conceptual and practical innovations, the authors analyse the effects of broader historical conditions on scientific work. To them, Latin American contemporary innovative epidemiological research and production have developed clearly differentiated principles, methods and technical projections which have led to a movement of critical or ‘social’ epidemiology. The functionalist approach of conventional epidemiology, characterized by an empiricist viewpoint, is being overcome by a more rigorous and analytical approach. This new epidemiological approach, in which the authors as members of CEAS (Health Research and Advisory Center) are working, has selectively incorporated some of the technical instruments of conventional epidemiology, subordinating them to a different theoretical and logical paradigm. The new framework of this group explains the need to consider the people's objective situation and necessities, when constructing scientific interpretations and planning technical action. In order to accomplish this goal, epidemiological reasoning has to reflect the unity of external epidemiological facts and associations, the so-called phenomenological aspect of health, with the underlying determinants and conditioning processes or internal relations, which are the essence of the health-disease production and distribution process. Epidemiological analysis is considered not only as a problem of empirical observation but as a process of theoretical construction, in which there is a dynamic fusion of deductive and inductive reasoning. It is an active formulation of a system of contradictions and relations among and between the structural (socio-economic), political and ideological conditions of each society, the particular social class realities and the individual health conditions which appear in all individuals of every social class. New categories and instrumental procedures are being developed, in order to attain a different and innovative epidemiological paradigm.

Epidemiologic and clinical studies of Chlamydia trachomatis infection in northeastern Poland.

We tested a total of 735 men and women, who either had clinical symptoms of lower urogenital tract infection or were considered for epidemiological reasons to be at high risk for sexually transmitted diseases, for Chlamydia trachomatis infection. Microbiologic examinations were performed by tissue culture with cycloheximide-treated McCoy cells. C. trachomatis infection was diagnosed in approximately 50% of men with nongonococcal urethritis, 23.5% of men with gonococcal urethritis, 69% of men with postgonococcal urethritis, and in 45% of male partners of C. trachomatis-positive women. Among men under 35 years of age with epididymitis, C. trachomatis was isolated from 42%, whereas Neisseria gonorrhoeae was found in only 21 men. C. trachomatis was isolated from 59% of women with nongonococcal cervicitis, 46% of those with gonococcal cervicitis, and 74% of those with postgonococcal cervicitis. Among female partners of men with nongonococcal urethritis, 68% were C. trachomatis-positive, as were 73.5% of the female contacts of C. trachomatis-positive men. In the groups of men and women without clinical or epidemiologic evidence of sexually transmitted infection, C. trachomatis-positive cultures were obtained from 3.8% and 3.6%, respectively. These studies revealed that the prevalence of C. trachomatis infection in northeastern Poland is high and is similar to that reported in Western countries.

Physiologic Categorization of Asbestos-Exposed Workers

Categorization of the pattern of physiologic abnormalities in patients with asbestos-associated disease may be important for clinical, compensation, and epidemiologic reasons. A population of 658 asbestos-exposed workers was divided into six groups (restrictive, mixed restrictive-obstructive, obstructive, abnormal diffusing capacity, small airway disease, and normal) based upon pulmonary function test results. Use of two commonly employed prediction equations for diffusing capacity produced divergent results. Adjustment of the forced vital capacity for airtrapping based upon measurement of residual volume or of total lung capacity can improve the accuracy of categorization, particularly in smokers. Hence, the process of interpretation of pulmonary function testing should be chosen carefully.

Female-to-Male Transmission of HTLV-III

<h3>To the Editor.—</h3> In the Oct 18, 1985, issue of<i>JAMA</i>, Redfield et al¹present evidence for heterosexual transmission of the human T-cell lymphotropic virus type III (HTLV-III). Male-to-female transmission has been documented previously, but female-to-male transmission has yet to be demonstrated. Approximately one tenth of 1% of all US cases of acquired immunodeficiency syndrome (AIDS) (18/14,125) have been attributed to female-to-male sexual transmission (Centers for Disease Control, national surveillance data, 1981 through October 1985). Therefore, any study supporting this mode of transmission must be rigorous. We feel that the study by Redfield et al is based on questionable data and unsound epidemiologic reasoning and that the evidence presented for female-to-male transmission is unconvincing. Our first criticism is that the means used to exclude persons with known AIDS risks were not sensitive and were subject to considerable bias. Risk factors for HTLV-III infection were ascertained through self-reporting by cases,

Red cell transfusions for polytransfused patients.

Patients with chronic anemia tolerate much lower leveis of hemoglobin than those experiencing acute blood loss or acute hemolysis. The compensating mechanism is the increase of red cell 2,3-diphosphoglycerate (DPG), causing increased release of oxygen to the tissues. For this and further clinical and epidemiologic reasons, it is unnecessary to transfuse patients with chronic anemia unless symptoms of anoxia are expressed. This rarely odcurs at hemoglobin leveis higher than 8 g/dl. Many patients tolerate lower leveis of hemoglobin and, therefore, do not require RBC transfusions.

Cost-effectiveness of the two-step skin test for tuberculosis screening of employees in a community hospital.

To assess the frequency of the booster effect as well as the need for and the cost effectiveness of the two-step skin test for tuberculosis screening at our medical center, we conducted a pilot study from June 1980 to March 1983 with hospital and clinic employees. Six (0.4%) of 1,521 employees tested by the two-step skin test demonstrated the booster effect. The mean age of these six employees was 35 years (range, 24 to 44 yr). During the study period, 10 employees converted to a positive skin test. The booster effect would have accounted for approximately 38% (6 of 16) of those converting if the two-step testing were not performed. At our medical center, the additional cost of the two-step skin test was low and justifiable for medical and epidemiologic reasons. We suggest that each hospital review the prevalence of tuberculosis among its patient and employee populations. The need for and cost effectiveness of the two-step skin test for new hospital employees must be re-examined on the basis of these data.

The role of potassium in control of blood pressure.

Extra potassium intake has been found to be a determinant of blood pressure for epidemiological and experimental reasons. People with hypertension have a small fall in blood pressure with added potassium. Potassium chloride (48 mmol/day) was given to 36 male patients with high blood pressure; 5 did not comply with therapy. In the entire group of patients, potassium chloride had no significant effect on blood pressure, but prevented the rise in blood pressure and pulse rate produced by posture. In patients with a urinary Na+ excretion less than 75 mmol per 10 mmol creatinine, potassium chloride had no effect on supine blood pressure, but prevented the rise in blood pressure and pulse rate with standing. In those on a high sodium intake, potassium chloride lowered both the systolic and diastolic pressures. In sodium-responsive subjects, potassium chloride prevented the rise in blood pressure induced by sodium chloride but had no significant effect on blood pressure when on a low sodium intake. These results indicate that potassium reduces the rise in blood pressure caused by sodium chloride and reduces the increased sympathetic postural response seen in people on a low sodium intake.

The application of epidemiology to the prevention of occupational cancer.

Epidemiology attempts to establish a quantitative causality which is essential in preventive medicine strategies for occupational cancer. By studying carefully exposure effect relationships and populations at risk, subtle causes of occupational cancer can be identified. The nature of epidemiological reasoning and the criticism of this methodology are outlined. Using combined epidemiological and industrial hygiene data, a quantitative risk assessment of a lifetime exposure of workers to benzene and its association with leukemia is presented. In a population of 1,000 workers exposed for a working lifetime to 100 ppm benzene vapor, 140 excess deaths from leukemia would occur. At a lifetime exposure of 10 ppm, it is calculated that 14 excess leukemia deaths would occur. Because the current legal standard is 10 ppms for occupational exposure, this epidemiological risk assessment indicates that an unexpectedly large number of excess leukemia deaths will result in a population of workers exposed to 10 ppm.

Hospital-based pneumococcal immunization: the epidemiologic rationale and its implementation.

Many patients hospitalized for or dying of pneumococcal bacteremia have been discharged from a hospital within the previous five years. In addition to age and underlying medical condition, previous hospital care, particularly for high risk conditions, is a useful marker for identifying individuals who are destined to develop serious pneumococcal infections. Relatively few patients, especially those with high risk conditions, would need to receive pneumococcal vaccine at the time of hospital discharge to prevent, within the next five years, each subsequent readmission or death from pneumococcal pneumonia. Although pneumococcal vaccine has not been widely used in the hospital setting, there are sound epidemiologic reasons to expect that organized programs for vaccine delivery in hospitals would be an effective approach to preventing many serious pneumococcal infections.

Coagglutination as an expedient for grouping Escherichia coli associated with urinary tract infections.

Thirteen serogroups of Escherichia coli most frequently are responsible for urinary tract infections in humans. Knowledge of serogroup is required for epidemiological reasons and to help differentiate between new and reemergent strains in infected patients. Coagglutination and bacterial agglutination were compared as serodiagnostic tools for identifying groups of E. coli associated with these infections. In contradistinction to bacterial agglutination, coagglutination showed no cross-reactions for 12 of the 13 known strains obtained from the Center for Disease Control. A single antiserum, E. coli O4, caused bacterial agglutination and not coagglutination. In addition, staphylococcal cells that were coated with antiserum reacted with sheep erythrocytes that had been treated with soluble extract of E. coli. The latter reaction, cohemagglutination, was as specific and rapid as coagglutination; easily visible patterns of clumping developed within 1 min after sensitized staphylococci and E. coli reagent were mixed. These results revealed a method that is sensitive and reproducible for identifying serogroups of E. coli responsible for urinary tract infections.

Interaction of drugs, hormones, and nutrition in the causes of cancer

Hormones may act as promoters in the carcinogenic process, and occasionally their metabolites may act as antihormones or have new physiologic effects. Drugs can interact with the endocrine system in many ways. They can promote secretion of a hormone, alter its rate of removal from plasma, change plasma protein-binding characteristics, or modify routes of metabolism. Estrogens have a preparative effect on the uterine endometrium. There are biologic, clinical and epidemiologic reasons for believing that estrogen administration to postmenopausal women increases the risk for endometrial cancer. Although there are similar biologic reasons to associate prolonged estrogenic stimulation with breast cancerr, evidence for such an association is weak. Oral contraceptive use has been associated with a variety of hepatocellular tumors. Although estrogens, per se, can effect several hepatic functions, it seems likely that the 17 alpha-alkyl and 17 alpha-ethinyl functions of the progestins and estrogens are involved in this process. The role of estrogen use during pregnancy in the causation of vaginal cancer in female offspring and the role of androgens in prostate cancer have been discussed.

Visceral Leishmaniasis in Honduras

Abstract Visceral leishmaniasis was found in three Honduran patients, and in a fourth this diagnosis was suspected because of the clinical presentation and for epidemiological reasons. All four cases originated from the same general area of Honduras. Three patients lived in the same valley approximately 35 km northeast of Tegucigalpa, and were related. Two patients died without the diagnosis having been made; two are responding to specific therapy.

Malignant Lymphoma Resembling Burkitt's Tumour in Rhesus Monkeys (Light- and Electron Microscopic Studies)

Spontaneous tumours of the haematopoetic system have been only rarely observed in nonhuman primates. We had the opportunity to carry out light and electron microscopic investigations of three lymphomas in immature rhesus monkeys from our colony. All animals had tumours of both retroperitoneum and lymph nodes. The relatively uniform lymphoblastic or lymphoreticular tumour cells as well as the massive occurence of the so-called "starry sky macrophages" were histologically characteristic. Histochemically, the marked pyroninophilia of these tumour cells was evident. The electron nicroscopy revealed the tumour cells as lymphoblasts of about 8 mu diameter with the following features: round or oval, occasionally deeply indented cell nuclei with relatively clear interchromatinic substance; mostly well developed nucleoli; sparsely, rough endoplasmatic reticulum; large numbers of free ribosomes and polyribosomes; a few large, bizzarre mitochondria, often situated at one pole; lipid vacuoles in some cells. These histological, cytological and electron microscopic characteristics correspond to those of the human Burkitt's Lymphoma. This tumour is classified as an undifferentiated malignant lymphoma. Tumours of this type are of particular interest on comparative and epidemiological reasons in light of the existence of morphologically similar experimental, virus induced lymphomas in monkeys.

Epidemiological Reasoning: Comments on ‘Popper's Philosophy for Epidemiologists’

Journal Article Epidemiological Reasoning: Comments on ‘Popper's Philosophy for Epidemiologists’ Get access A. MICHAEL DAVIES A. MICHAEL DAVIES Department of Medical Ecology, Hebrew UniversityHadassah Medical School, P. O. Box 1172, Jerusalem, Israel Search for other works by this author on: Oxford Academic PubMed Google Scholar International Journal of Epidemiology, Volume 4, Issue 3, September 1975, Pages 169–170, https://doi.org/10.1093/ije/4.3.169 Published: 01 September 1975