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Biomedical subjects

H Dixon

Publications and source records attributed to H Dixon.

At least 37 records · Page 2Linked to original sources
PubMed1989

Control of morbidity due to Schistosoma haematobium on Pemba Island: programme organization and management.

A programme to control urinary schistosomiasis was initiated on Pemba island in January 1986 with the objectives of eliminating morbidity due to S. haematobium by utilizing a primary health care approach of strengthening the existing health care delivery system and creating a sound basis for future control of other parasitic and communicable diseases. The plan of action included training of rural health assistants to undertaken an intervention phase targeted to schools for selective population chemotherapy surveys at six-month intervals during the first two years, using indirect diagnostic techniques (observation of gross haematuria and detection of microscopic haematuria by chemical reagent strips) to identify individuals for treatment with praziquantel at a dose of 40 mg/kg body weight. The evaluation of the indirect techniques indicated that both sensitivity and specificity of the chemical reagent strips to detect infection were greater than 90%. After three selective population chemotherapy surveys, the prevalence of gross haematuria was reduced by 94.2% (15.8% to 0.9%) and both gross and microscopic haematuria were reduced by 76.4% (54.1% to 12.8%) among school children. Community involvement and health education were stressed in this programme. The use of dispensary laboratories to maintain control of urinary schistosomiasis is now being evaluated.

Adolescent↗
PubMed1989

Multicentre clinical trials of benzimidazole-carbamates in human cystic echinococcosis (phase 2).

A multicentre study which constituted the second phase of trials of the efficacy of albendazole and mebendazole in human cystic echinococcosis was coordinated by WHO. A total of 112 patients from four clinical centres in Beirut, Paris, Rome and Sofia completed standardized dosage of regimens of each drug and 68 patients were followed up for at least 12 months after treatment. Albendazole was more effective than mebendazole and adverse reactions were comparable with both treatment regimens. At least 12 months is needed after treatment for an objective evaluation of the efficacy of benzimidazoles. At present, treatment with albendazole or mebendazole should be reserved for inoperable cases of cystic echinococcosis (under strict medical supervision) and individualized according to the patient's response and the occurrence and severity of adverse reactions.

Adolescent↗
PubMed1989

Operational studies on the control of Taenia solium taeniasis/cysticercosis in Ecuador.

A large-scale study in Loja and El Oro Provinces, Ecuador, demonstrated that population-based treatment of human taeniasis with a low dose of praziquantel is feasible and effective for the short-term control of transmission of Taenia solium in hyperendemic areas. Chemotherapeutic intervention also effectively promoted local preventive measures and contributed greatly to the elaboration of a long-term control programme.

Adolescent↗
PubMed1988

The transmission potential of monkeypox virus in human populations.

Data on monkeypox in Zaire over the five years 1980-1984 are analysed to assess the protection imparted by past smallpox vaccination and the transmission potential of the virus in unvaccinated communities. Attack rates in individuals with and without vaccination scars indicated that smallpox vaccination (discontinued in 1980) imparted approximately 85% protection against monkeypox. It is predicted that monkeypox virus will continue to be introduced into human communities from animal sources, and that the average magnitude and duration of monkeypox epidemics will increase as vaccine-derived protection declines in the population. On the other hand, current evidence indicates that the virus is appreciably less transmissible than was smallpox, and that it will not persist in human communities, even in the total absence of vaccination. The findings thus support the recommendation of the Global Commission for the Certification of Smallpox Eradication to cease routine smallpox vaccination in monkeypox endemic areas, but to encourage continued epidemiological surveillance.

Democratic Republic of the Congo↗
PubMed1987

Stochastic model for interhuman spread of monkeypox.

With the eradication of smallpox, systematic routine vaccination with vaccinia has ceased and an increasing proportion of the human population in tropical rain forest areas of central and western Africa lacks vaccinia-derived immunity to monkeypox virus. This raises the question of the ability of monkeypox virus to establish and maintain itself in an unvaccinated population through continuous man-to-man transmission. A computerized stochastic model of Monte Carlo type was constructed to assess this potential risk. Simulated series were repeated 100 times to obtain distributions of predicted outcomes for decreasing levels of vaccination coverage (70 per cent, 50 per cent, and 0 per cent). The results revealed a substantial increase in new secondary cases in the total absence of vaccinia-induced immunity. Nevertheless, none of the simulated series did lead to an "explosive" epidemic. The model clearly indicated diminishing numbers of cases in successive generations and eventual cessation of transmission. Therefore, it appears highly improbable that the virus could maintain itself permanently in communities by interhuman transmission. After the eradication of smallpox, human monkeypox constitutes the most important orthopoxvirus infection in man, but analysis of information collected up to this time suggests that it does not represent currently a serious public health problem or a challenge to the achieved eradication of smallpox.

Adolescent↗
PubMed1987

Collaborative study on antigens for immunodiagnosis of Schistosoma japonicum infection.

Six research laboratories in Australia, Japan, the Philippines and the USA participated in a collaborative evaluation of immunodiagnostic tests for Schistosoma japonicum infections. The serum bank consisted of 385 well-documented sera from Brazil, Kenya, Philippines, Republic of Korea and Europe. Twelve S. japonicum antigen/test system combinations were evaluated.Crude S. japonicum egg antigens showed the highest sensitivity and specificity. The defined or characterized antigens showed no advantage over the crude antigens. Quantitative seroreactivity of all S. japonicum antigens showed a positive correlation with faecal egg counts (log x + 1) in all age groups. The performance of the circumoval precipitin test was satisfactory within the same laboratory but with differences in the results between laboratories. A monoclonal antibody used in a competitive radioimmunoassay test system performed as well as the crude egg antigens.The high sensitivity of crude S. japonicum antigens now permits further evaluation for wide-scale use in public health laboratories of endemic areas to support control efforts.

Antigens, Helminth↗
PubMed1986

Multicentre clinical trials of benzimidazolecarbamates in human echinococcosis.

Studies coordinated by the World Health Organization were conducted in seven clinical centres on the chemotherapy of human echinococcosis with mebendazole, albendazole, and flubendazole. The first phase of these ended with the following conclusions.Treatment of 85 patients with mebendazole for cystic (Echinococcus granulosus) echinococcosis was successful in 8 patients and partially successful in 4 others. Flubendazole was effective in only one case of lung echinococcosis. Albendazole was successful in 5 of 30 patients treated and partially successful in 4 others. Further studies on new drugs or new formulations of existing benzimidazoles and on better forms of their application are needed. In the mean time, chemotherapy of human cystic echinococcosis should be restricted to inoperable cases.In 54 patients with E. multilocularis echinococcosis, it was confirmed that mebendazole therapy may arrest the development of the lesions. This treatment is therefore indicated in most cases of alveolar echinococcosis with or without surgery. However, further studies are needed to clarify the optimal regimen for mebendazole treatment and to explore the effectiveness of albendazole therapy.

Adolescent↗
PubMed1985

Effect of praziquantel on hematuria and proteinuria in urinary schistosomiasis.

In five settlements on Lake Volta, Ghana, 230 persons infected with S. haematobium were treated with either 30 or 40 mg/kg of praziquantel. Both treatment regimes gave similar overall cure rates (60%) and reduction in geometric mean egg counts (92%) at a six-month follow-up. In this highly endemic area, 32% of the initial urine specimens were visibly bloody and only 4% remained bloody after treatment. Geometric mean egg counts of visibly bloody urine specimens were two to six times higher than normal appearing urine specimens. In children under 15 years of age, gross hematuria was reduced by 91% and hematuria as detected by reagent strips was reduced by 77% after treatment with praziquantel. Among adults, gross hematuria was reduced by 76% and hematuria as detected by reagent strips was reduced by 68%. Reduction was observed in 74% of all persons with 100 mg of protein/100 ml of urine or more prior to treatment. The cure rate with praziquantel was only 36.1% in children who had visibly bloody urine specimens associated with high geometric mean egg counts prior to treatment. The lowest cure rate (15.4%) was observed in persons with persistent hematuria and proteinuria after treatment although the geometric mean urinary egg count was reduced 84%. In infected individuals without hematuria or proteinuria prior to treatment, the cure rate was 96%. This study demonstrated that praziquantel reduced clinical signs due to S. haematobium infection as well as achieved a high cure rate and/or reduction of egg excretion. Conversely, individuals with clinical signs of hematuria and proteinuria had a lower cure rate with praziquantel than individuals without clinical signs.

Adolescent↗
PubMed1985

Evaluation of reagent strips in urine tests for detection of Schistosoma haematobium infection: a comparative study in Ghana and Zambia.

The presence of haematuria and proteinuria, detected by reagent strips, was compared with Schistosoma haematobium egg counts in the urines of human subjects from two epidemiologically distinct areas in Ghana and Zambia. In children and adults in both areas, the individual or combined semiquantitative levels of proteinuria and haematuria were related directly to increasing urinary egg counts. In both areas the presence of blood in the urine was highly specific (greater than 85%) and sensitive, being positive in 97% of urine specimens with more than 64 eggs per 5-ml sample of urine. The sensitivity of the protein indicator was also high, but its specificity was less than the blood indicator. The specificity of combined proteinuria and haematuria was higher than either alone; on the other hand, the sensitivity was lower than either alone. At each level of proteinuria and haematuria, the geometric mean urinary egg count was higher in Ghana than in Zambia. This study confirms the necessity to evaluate indirect diagnostic techniques in each endemic country, in order to establish criteria for their interpretation, before wide-scale use.

Adolescent↗
PubMed1985

Indirect screening for Schistosoma haematobium infection: a comparative study in Ghana and Zambia.

Four indirect approaches, based on inquiry into a past history of haematuria, visual inspection for blood in the urine specimens, and the use of reagent strips to detect haematuria and proteinuria, were evaluated to identify persons with Schistosoma haematobium infection. These approaches were applied individually and in three different screening sequences on two populations in Ghana and Zambia in order to identify infected children and adults for subsequent treatment in both areas. Detection of haematuria using reagent strips was the single approach with the highest sensitivity and specificity. The observation of gross haematuria (bloody urine), followed by detection of blood by reagent strips, identified 87% of infected children in both areas. This screening sequence showed the highest combined sensitivity and specificity in the identification of infected children as well as adults for treatment in both areas. Differences in the results between the two countries are discussed. This study emphasizes the need for evaluation of indirect screening procedures for the diagnosis of S. haematobium infection in each endemic area so as to establish criteria for their interpretation, prior to large-scale field application.

Adolescent↗
PubMed1983

Relation between intensity of Schistosoma haematobium infection and clinical haematuria and proteinuria.

In an endemic area on Lake Volta, Ghana, urinary blood and protein levels as determined by chemical reagent strips in persons infected with Schistosoma haematobium, particularly in children aged between 5 and 14, correlated positively with urinary egg counts. Geometric mean S haematobium egg counts were 10 or more times higher in urine specimens with at least 10 mg/dl of protein and detectable haematuria than in those without detectable blood or protein. Chemical reagent strips were both specific and sensitive for detection of urinary blood associated with S haematobium infection. This simple technique could be useful for screening entire populations in which urinary schistosomiasis is endemic so that heavily infected persons needing specific treatment can be identified.

Adolescent↗
PubMed1983

The interrater reliability of DSM III in children.

A total of 195 admissions to a child psychiatric inpatient unit were diagnosed independently by two to four clinicians on the basis of case presentations at the first ward-round after admission. The DSM III as a whole and the major categories were of high or acceptable reliability, though a few were clearly unreliable. The results are generally consistent with other studies. Unlike other studies, the subcategories were examined and found to vary widely in reliability both as a whole across the system and within parent major categories, throwing considerable doubt upon their utility. The results indicate the need both for improved diagnostic data-gathering techniques in child psychiatry and for more better-designed studies of reliability and, most necessarily, of validity.

Adolescent↗
PubMed1982

Epidemiological models of poliomyelitis and measles and their application in the planning of immunization programmes.

This report describes the construction and application of epidemiological models of measles and poliomyelitis. In these models, epidemiological classes and their age structure have been based on the natural history of these diseases in the population aged 0 - 19 years. The flow of the population through the classes has been expressed as an equation system suitable for computer interpretation. The models have been used to simulate both the natural course of the diseases and the effect of various immunization schemes. The models were also used to explore prospects for control and eradication of these diseases with specific immunization programmes, and their relative effectiveness and cost-effectiveness are discussed.

Adolescent↗
PubMed1982

Collaborative study on antigens for immunodiagnosis of schistosomiasis.

Eight research laboratories in Europe and the United States of America were selected on the basis of having published data on Schistosoma mansoni and S. japonicum antigens to participate in a study of various antigen/test combinations for immunodiagnosis of schistosomiasis. The serum bank consisted of 395 well documented sera from four endemic areas in Brazil (2 areas), Kenya, and the Philippines. Altogether, 21 S. mansoni and four S. japonicum antigen and immunoassay combinations were evaluated.S. mansoni egg antigens yielded a higher combined sensitivity than adult worm antigens, irrespective of their purity, in active S. mansoni infections before and after specific treatment. Quantitative seroreactivity of characterized S. mansoni egg antigens showed good correlation with faecal egg counts in the 5-14 year age group. No correlation between morbidity related to S. mansoni and seroreactivity was observed in any test system.Three S. japonicum egg antigens showed high sensitivity and specificity in relation to the presence or absence of eggs in the stool. The quantitative seroreactivity of the characterized S. japonicum egg antigens correlated directly with the intensity of S. japonicum infection in all age groups.The enzyme-linked immunosorbent assay (ELISA), using several different procedures, performed well with the antigens used in the study. The indium slide immunoassay (ISI), a simple qualitative visual test system using an S. mansoni egg antigen, demonstrated a high degree of sensitivity and specificity.The results did not indicate the superiority of any particular immunodiagnostic method for detecting antischistosome antibodies. This collaborative study is considered a first step towards developing and standardizing antigens for immunodiagnosis of schistosomiasis.

Adolescent↗