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S N Cousens

Publications and source records attributed to S N Cousens.

At least 19 recordsLinked to original sources
PubMed2004

A case-control study of sporadic Creutzfeldt-Jakob disease in the United Kingdom: analysis of clustering.

BACKGROUND: The authors investigated whether cases of sporadic Creutzfeldt-Jakob disease (CJD) had lived closer to one another at some time in life than individuals without sporadic CJD. Such a phenomenon would be compatible with some cases resulting from transmission. METHODS: UK sporadic CJD cases occurring from 1990 to 1998 were identified. Age-, sex- and hospital-matched controls were recruited. Lifetime residential histories were obtained by interview, usually with a proxy respondent. With use of Monte Carlo simulation, the residential proximity of cases during various time periods was compared with that expected in the absence of any clustering, using the information collected on the controls. RESULTS: Two hundred twenty sporadic CJD disease cases and 220 controls were included. Cases lived closer together than might be expected in the absence of any disease-clustering mechanism. This evidence became stronger as the critical period during which residential proximity was required to have occurred extended further into the past. CONCLUSIONS: These findings are consistent with some sporadic Creutzfeldt-Jakob disease (CJD) cases resulting from exposure to a common external factor. The rarity of sporadic CJD suggests that repeated point-source outbreaks of infection are more likely to explain our observations than direct case-to-case transmission. Identifying sources of such outbreaks many years after the event will be extremely difficult.

Adult↗
PubMed2004

Child mortality in a West African population protected with insecticide-treated curtains for a period of up to 6 years.

OBJECTIVES: To determine the impact of insecticide-treated curtains (ITC) on all-cause child mortality (6-59 months) over a period of six years. To determine whether initial reductions in child mortality following the implementation of ITC are sustained over the longer term or whether "delayed" mortality occurs. METHODS: A rural population of ca 100 000 living in an area with high, seasonal Plasmodium falciparum transmission was studied in Burkina Faso. Annual censuses were conducted from 1993 to 2000 to measure child mortality. ITC to cover doors, windows, and eaves were provided to half the population in 1994 with the remainder receiving ITC in 1996. Curtains were re-treated or, if necessary, replaced annually. FINDINGS: Over six years of implementation of ITC, no evidence of the shift in child mortality from younger to older children was observed. Estimates of the reduction in child mortality associated with ITC ranged from 19% to 24%. CONCLUSIONS: In our population there was no evidence to suggest that initial reduction in child mortality associated with the introduction of insecticide-treated materials was subsequently compromised by a shift in child mortality to older-aged children. Estimates of the impact of ITC on child mortality in this population range from 19% to 24%.

Animals↗
PubMed2004

The epidemiology of variant Creutzfeldt-Jakob disease.

Variant Creutzfeldt-Jakob disease (vCJD) was identified as a new disease in 1996. It was linked to infection with the bovine spongiform encephalopathy (BSE) agent although the epidemiological evidence for this was not strong, but later strain typing studies confirmed the association. The disease has affected predominantly young adults whose dietary and other characteristics are unexceptional compared to control groups, other than that all patients to date have been methoinine homozygous at codon 129 of the prion protein gene and the incidence has been about two times higher in the North of the UK. The number of cases in the 7 years after first identification of the disease has been considerably lower than initially feared, given the likely widespread exposure of the UK population to the BSE agent through contaminated beef products. Predictions of the possible future course of the epidemic have many associated uncertainties, but current mathematical models suggest that more than a few thousand cases is unlikely. Such modelling is limited by the absence of a test for infection with the vCJD agent. The development of a test that could be used on easily accessible tissue to detect infection early in the incubation period would not only advance understanding of the epidemiology of infection with the agent but would also aid the implementation of control measures to prevent potential iatrogenic spread.

Age Factors↗
PubMed2003

Deaths from variant Creutzfeldt-Jakob disease in the UK.

In 2002, 17 people died from variant CJD (vCJD) in the UK, compared with 20 in 2001 and 28 in 2000. We analysed data for deaths from vCJD since 1995 and estimated the underlying trend in mortality. The trend had a quadratic component (p=0.005), suggesting that the increase was not exponential, and that the previously increasing trend is slowing down. The death rate peaked in 2000. These findings are encouraging, but mortality might increase again in the future.

Adolescent↗
PubMed2003

Humoral responses to defined malaria antigens in children living since birth under insecticide treated curtains in Burkina Faso.

Insecticide treated materials (ITM) are considered a useful malaria control measure for endemic countries, but whether they also delay the acquisition of immunity to malaria remains unclear. This study investigates plasma antibody levels in 160 children aged 3-6 years from five villages protected by insecticide treated curtains (ITC) over 6 years and in 184 children of the same age group from five villages in the same area never covered by ITC. The antigens to which antibodies were investigated were: the Plasmodium falciparum circumsporozoite protein (CSP) repetitive sequence (NANP)5; the C-terminal domain of the P. falciparum exported protein 1 (Cter-PfExp1); three fragments of the glutamate rich protein (GLURP), referred to as R0, R1 and R2; the merozoite surface protein 3 (MSP3). The level of antibodies was lower in children from the ITC area than in children from the non-ITC area for (NANP)5, R0, R2 and MSP3. Prevalence and intensity of P. falciparum infection were similar in the two groups of children. These findings suggest that reducing the level of malaria transmission over a long period may affect the level of antibodies in children to both sporozoite and blood stage malaria antigens.

Animals↗
PubMed2003

IFN-gamma is associated with risk of Schistosoma japonicum infection in China.

Before the start of the schistosomiasis transmission season, 129 villagers resident on a Schistosoma japonicum-endemic island in Poyang Lake, Jiangxi Province, 64 of whom were stool-positive for S. japonicum eggs by the Kato method and 65 negative, were treated with praziquantel. Forty-five days later the 93 subjects who presented for follow-up were all stool-negative. Blood samples were collected from all 93 individuals. S. japonicum soluble worm antigen (SWAP) and soluble egg antigen (SEA) stimulated IL-4, IL-5 and IFN-gamma production in whole-blood cultures were measured by ELISA. All the subjects were interviewed nine times during the subsequent transmission season to estimate the intensity of their contact with potentially infective snail habitats, and the subjects were all re-screened for S. japonicum by the Kato method at the end of the transmission season. Fourteen subjects were found to be infected at that time. There was some indication that the risk of infection might be associated with gender (with females being at higher risk) and with the intensity of water contact, and there was evidence that levels of SEA-induced IFN-gamma production were associated with reduced risk of infection.

Adolescent↗
PubMed2002

Down-regulation of specific antigen-driven cytokine production in a population with endemic Schistosoma japonicum infection.

Schistosome antigen-driven cytokine responses and antischistosome antibody levels of residents of a Schistosoma japonicum endemic island in Poyang Lake, Jiangxi Province were studied before and 45 days after treatment with praziquantel. IL-4, IL-5, IL-10 and INF-gamma were all detected in the supernatants of whole-blood cultures after stimulation with schistosome soluble egg antigen (SEA) and soluble worm antigen preparation (SWAP). The percentages of subjects producing detectable amounts of each cytokine assayed were higher in the group who were negative by stool examination at the start of the study than in those who were initially stool positive. After praziquantel treatment the percentages of subjects producing both type I and type II cytokines increased. This suggests that the production of both types of cytokine was down-regulated in the presence of live, egg-laying S. japonicum adult worms but that this was reversible by treatment. In contrast, the antibody studies showed higher levels of SWAP and SEA-specific antibodies (IgE, total IgG, IgG4, IgM) in subjects who were originally stool-positive than in those who were stool-negative. After treatment specific IgE responses were elevated, but total IgG and IgG4 anti-SEA and IgM anti-SWAP antibody levels all fell significantly.

Adolescent↗
PubMed2001

Predictability of the UK variant Creutzfeldt-Jakob disease epidemic.

Back-calculation analysis of the variant Creutzfeldt-Jakob disease epidemic in the United Kingdom is used to estimate the number of infected individuals and future disease incidence. The model assumes a hazard of infection proportional to the incidence of bovine spongiform encephalopathy in the United Kingdom and accounts for precautionary control measures and very wide ranges of incubation periods. The model indicates that current case data are compatible with numbers of infections ranging from a few hundred to several millions. In the latter case, the model suggests that the mean incubation period must be well beyond the human life-span, resulting in disease epidemics of at most several thousand cases.

Adolescent↗
PubMed2001

Insecticide treated curtains and allelic polymorphism of Plasmodium falciparum genes in a rural area of Burkina Faso (west Africa).

To assess the possible impact of insecticide treated curtains (ITC) on the composition of a Plasmodium falciparum population in a rural area of Burkina Faso, blood samples were collected during the rainy season of 1997 from 226 children aged 3-6 years, from 4 villages equipped with ITC and 2 control villages without ITC. The analysis of fragment lengths of 3 highly polymorphic P. falciparum genes (msp-1, msp-2 and glurp) revealed a maximum number of 3 alleles per infected person for each gene. The mean number of clones per infected person was similar in villages with and without ITC.

Alleles↗
PubMed2001

Glaucoma prevalence may not be uniformly high in all 'black' populations.

Epidemiological data on the prevalence of glaucoma are generally presented for populations described as "whites" or "blacks". "Black" populations appear to have a higher glaucoma preva lence than "white" populations. We describe a population-baseed survey for glaucoma in rural Northern Nigeria. A total of 1563 Hausa/Fulani individuals aged 5 years and above, underwent an extensive screening test and a detailed ophthalmological examination was performed on individuals who failed the test. The overall prevalence of open angle glaucoma in this population was 1.02% (0.12 to 3.64, 95% confidence interval) in individuals 45 years of age and older. This is lower than the prevalence rates reported for other "black" populations. The low prevalence of glaucoma detected in this African population may be, to some extent, a reflection of the age structure of the population studied or methodological differences in ophthalmic examinations performed. It is also possible that the prevalence of glaucoma varies considerably between "black" populations due to genetic heterogeneity or the effect of some unidentified environmental exposure. The use of the simple description of populations as 'black' (or 'white'), which focuses on a commonality, tends to obscure the potential heterogeneity within and between populations and thus may be unhelpful in some circumstances.

Adolescent↗
PubMed2000

Incidence of variant Creutzfeldt-Jakob disease in the UK.

The number of deaths from variant CJD (vCJD) in the UK increased in the last quarter of 1998, although numbers were lower in subsequent quarters. We analysed the numbers of definite and probable (living and dead) vCJD cases since 1994 to assess trends in incidence. We estimated that the number of onsets increased by 23% per year for 1994-2000 (p=0.004), and that deaths increased by 33% for 1995-2000 (p=0.005). The absolute number of cases in the UK is still low, but such an increase should be a matter of concern.

Creutzfeldt-Jakob Syndrome↗
PubMed2000

Diagnosis and prognosis of wheezing disorders in young children in the city of São Paulo, Southeast Brazil.

UNLABELLED: Three-hundred-and-ninety-seven children aged 2-59 mo presenting to the paediatric emergency departments of five public hospitals in São Paulo, Brazil, with an acute episode of lower respiratory disease were examined. The children were classified into the following diagnostic categories: acute bronchitis, acute bronchiolitis, pneumonia, asthma, post-bronchiolitis wheezing and wheezing of uncertain aetiology. Three years after the initial study, the homes of the children diagnosed as asthmatic or as having wheezing of uncertain aetiology were visited to collect information on subsequent episodes of lower respiratory disease. This paper reports the proportional incidence of different categories of lower respiratory disease and the results of an analysis to investigate clinical features that might distinguish wheezing children between those with asthma and those with an infectious disease. The predictions made for children with wheezing of uncertain aetiology were then compared with the follow-up data. Recurrent wheezing disorders (asthma, post-bronchiolitis wheezing) were common in the study sample (47% of children). Thirty-six percent of children with an initial diagnosis of wheezing of uncertain aetiology were diagnosed as asthmatic by another doctor over the next 3 y. We were unable to identify any clinical features that were useful in identifying those children likely to be diagnosed subsequently as asthmatic. CONCLUSIONS: The use of a diagnostic category similar to that which we have called "wheezing of uncertain aetiology" might help to alert physicians early to the possibility of asthma without interfering in the management of the illness. Such a classification might also be useful in epidemiological investigations of the aetiology of lower respiratory diseases.

Asthma↗
PubMed2000

Design and analysis issues in cluster-randomized trials of interventions against infectious diseases.

This paper discusses the application of the cluster-randomized trial (CRT) design to evaluate the effectiveness of interventions against infectious diseases. In addition to the usual rationale for this design, there are a number of other advantages that are peculiar to the study of infectious diseases. In particular, CRTs are able to measure the overall effect of an intervention at the population level, capturing both the direct effect of an intervention on an individual's susceptibility to infection, and also the indirect effects due to changes in risks of transmission to other individuals, or to the mass effect or 'herd immunity' resulting from intervening in a large proportion of the population. We briefly review published CRTs of interventions against infectious diseases, most of which have been conducted in the developing countries where such diseases predominate. The focus is on trials in which communities or other large groupings are randomized, and in which impacts on infectious disease incidence or mortality are assessed. We then discuss three issues that are of special relevance to CRTs of infectious diseases. First, issues relating to the definition and size of clusters; secondly, the role of matching or stratification, and the choice of matching factors; and thirdly, the definition of direct and indirect effects of intervention, and methods of assessing these components in a CRT. We conclude by outlining some areas for future research.

Biometry↗
PubMed2000

Diagnosis of new variant Creutzfeldt-Jakob disease.

As of December 31, 1998, 35 deaths had been attributed to new variant Creutzfeldt-Jakob disease (nvCJD) in the United Kingdom, of which 33 cases had been neuropathologically confirmed and 2 classified as probable nvCJD. Fifteen cases were male and 20 female. The median illness duration was 14 months (range, 8-38 months) and the median age at death was 29 years (range, 18-53 years). The dinical features were consistent with previous descriptions. In nearly all cases, there were early psychiatric symptoms after a median period of 6 months ataxia developed, followed by involuntary movements and cognitive impairment. Electroencephalograms did not show the "typical" appearances found in sporadic CJD, about half the cases tested had a positive 14-3-3 immunoassay, and over 70% of cases had bilateral pulvinar high signal on magnetic resonance brain scanning. Prion protein gene analysis showed that all cases were homozygous for methionine at codon 129. Diagnostic criteria for nvCJD have been formulated, which have a high sensitivity and specificity.

Adolescent↗
PubMed1999

Impact of fly control on childhood diarrhoea in Pakistan: community-randomised trial.

BACKGROUND: Several million children are killed each year by diarrhoeal diseases; preventive strategies appropriate for developing countries are vital. Despite strong circumstantial evidence that flies are vectors of diarrhoeal diseases, no convincing studies of the impact of fly control on diarrhoea incidence in developing countries have been reported. We undertook a randomised study of the effect of insecticide spraying on diarrhoea incidence. METHODS: Six study villages were randomly assigned to two groups. Flies were controlled through insecticide application in group A in 1995 and in group B in 1996. In 1997 the effectiveness of baited fly traps was tested in group A villages. Diarrhoea episodes were monitored in children under 5 years through mothers' reports during weekly visits by a health visitor. Fly density was monitored by use of sticky fly-papers hung in sentinel compounds. FINDINGS: During the fly seasons (March-June) of both 1995 and 1996, insecticide application practically eliminated the fly population in the treated villages. The incidence of diarrhoea was lower in the sprayed villages than in the unsprayed villages in both 1995 (mean episodes per child-year 6.3 vs 7.1) and 1996 (4.4 vs 6.5); the reduction in incidence was 23% (95% CI 11-33, p=0.007). At times other than the fly season there was no evidence of a difference, in diarrhoea morbidity between sprayed and unsprayed villages. Fly density data for 1997 indicate the ineffectiveness of baited traps in this setting. INTERPRETATION: Fly control can have an impact on diarrhoea incidence similar to, or greater than, that of the interventions currently recommended by WHO for inclusion in diarrhoeal disease control programmes in developing countries. This important finding needs confirmation in other settings in developing countries. Technologies and practices that interrupt disease transmission by flies need to be developed and promoted.

Animals↗
PubMed1999

Geographical distribution of variant CJD in the UK (excluding Northern Ireland).

BACKGROUND: The agent that causes variant Creutzfeldt-Jakob disease (variant CJD) is indistinguishable from the causative agent of bovine spongiform encephalopathy (BSE). The transmission route by which human beings are infected has not been established. One hypothesis is that cases of variant CJD have resulted from exposure to the BSE agent via rendering plants involved in the production of meat and bone meal, the main vehicle of the BSE epidemic. METHODS: We identified cases of variant CJD through the National CJD Surveillance Unit, and obtained lifetime residential histories of cases by interviewing a relative. The addresses of all rendering plants in the UK (excluding Northern Ireland) in production in 1988 were available from a survey done in that year. We calculated the distance between each case's place of residence on Jan 1, 1988, and the nearest rendering plant from postcode data, and used data from the 1991 UK census to estimate the population living within various distances of rendering plants. We compared the observed number of cases of variant CJD within a particular distance of a rendering plant with the number expected if there is no association between residential proximity to a rendering plant and the risk of developing variant CJD. FINDINGS: Up to Aug 31, 1998, 26 cases of variant CJD with onset in the UK (Northern Ireland not included) had been identified. The observed and expected numbers of variant CJD cases living within a specified distance of any rendering plant up to 50 km were almost the same. Two plants in the county of Kent each had four cases within 50 km in 1988, significantly more cases than expected (plant A, 1.04 expected; plant B, 0.74 expected). Multiple significance tests were done, so some tests would be expected to appear significant by chance alone. Computer simulations suggested that the observation of four cases of variant CJD living in an area with a population of 1.5 million (the size of Kent) is not unexpected. INTERPRETATION: There is no evidence that people with variant CJD tended to live closer than the population as a whole to rendering plants in the 1980s. The reported cluster of variant CJD cases in Kent is most probably a chance finding.

Abattoirs↗
PubMed1999

Insecticide-treated curtains reduce the prevalence and intensity of malaria infection in Burkina Faso.

A large, randomized controlled trial to investigate the impact of insecticide-treated curtains (ITC) on child mortality was conducted in an area of seasonal, holoendemic malaria in Burkina Faso. 158 communities totalling some 90,000 people were censused and grouped into 16 geographical clusters, 8 of which were randomly selected to receive ITC in June-July 1994, just prior to the rainy season. In September-October 1995, at the peak period of malaria transmission, a cross-sectional survey was conducted in 84 of the villages. A random sample of 905 children aged 6-59 months was identified and visited. 763 children (84%) were present at the time of the visit and recruited into the study. Mothers were asked about fever in the past 24 h, the child's temperature was taken, and a sample of blood collected to identify and quantify malaria infections and to measure haemoglobin (Hb) levels. Children protected by ITC were less likely to be infected with Plasmodium falciparum (risk ratio = 0.92; 95% CI 0.86, 0.98) or P. malariae (risk ratio = 0.42, 95% CI 0.19, 0.95). The mean intensity of P. falciparum infections was lower among children protected by ITC (899 vs. 1583 trophozoites/microliter; P < 0.001), while the mean Hb level was 0.4 g/dl higher (P < 0.001). While we found no evidence that ITC had an impact on the prevalence of malaria-associated fever episodes, the confidence intervals around our estimates of the impact of ITC on malaria morbidity were wide. We conclude that widespread implementation of ITC in this area of high malaria transmission led to a modest reduction in the prevalence of malaria infection and to a more substantial reduction in the intensity of these infections which caused increased Hb levels. We were unable to demonstrate any impact of ITC on malaria morbidity, but the wide confidence intervals around our point estimates do not preclude the possibility of a substantial impact.

Age Distribution↗