Forest malaria in Vietnam: a challenge for control

Forest malaria is a complex but common phenomenon occurring in southeast Asia. We studied its epidemiology through a prospective community-based study in central Vietnam. A total of 585 individuals were followed for two years by active case detection and biannual cross-sectional surveys. The prevalence of antibodies to Plasmodium falciparum was constantly about 20% across surveys and the incidence rate of clinical episodes of P. falciparum malaria was 0.11/person-year. Multivariate analysis showed that regular forest activity was the main risk factor for clinical malaria and malaria infections. Untreated bed nets had a significant protective effect (60%), except for people regularly sleeping in the forest. The population-attributable fraction for regular forest activity was estimated to be 53%. Our results confirm the major role played by forest activity on the malaria burden in this area and provide the basis for targeting control activities to forest workers. New interventions based on insecticide-treated materials need to be urgently evaluated.     

云南省南部农村居民疟防KAP变化影响因素

目的了解云南省南部农村居民疟防知识、态度、行为（KAP）变化的影响因素。方法选择云南省南部4个县，采用分层整群不等比例抽样调查方法，问卷收集居民一般情况、疟防常识知晓、疟防态度及行为习惯等资料，对回答内容进行KAP量化分析。结果农村居民的疟防KAP水平于宣教后呈显著提高，疟防态度改善最为明显（O．8051±0．0050，F=3132．85，P〈0．01），疟防常识知晓得分增幅最小，但仍有统计学意义（0．2046±0．0061，F=29．98，P〈0．01），影响疟防常识知晓变化的主要因素有年龄、文化程度、求医意向、蚊帐拥有及其使用，影响疟防态度变化的主要因素为年龄、疟疾症状知晓、蚊帐拥有及其使用，影响疟防行为变化的主要因素有年龄、文化程度、疟疾症状知晓、蚊帐使用意愿，研究地区农村居民的疟防态度和卫生行为构成不完全依赖疟防常识的积累。结论宣教后，居民的疟防KAP影响因素及其程度发生改变，人类学指标的影响强度增大，疟防常识宣教对人群的正向引导作用明显。     

Cost-effectiveness research in malaria control and the need for health behaviour and socio-economic research in malaria control in Thailand

The complexity of the malaria situation in Thailand requires behavioural and socio-economic research in wide variety of areas including; migration, illness behaviour, motivation of staff and communities and the relationship of institutional and community expenditure to reduction in morbidity. The research ideally should be constructed in such a way as to maximize the availability of methods for incorporation into routine monitoring, evaluation, and policy making activities of the Anti-Malaria Programme.     

Forest malaria in central Vietnam

Studies were conducted in a village in central Vietnam to explain the existence of a forest malaria cycle of transmission external to the village. The findings suggested no malaria transmission in the village because of the absence of a suitable vector, but suggested evidence for transmission in villagers when attending garden plots in the forested hills surrounding the village. A sizeable population residing near these garden plots, the presence of Anopheles dirus (a highly efficient vector), and a degree of malaria immunity within the inhabitants created suitable conditions to sustain malaria transmission outside the village.     

威海市疟疾监测点居民有关疟防知识、态度和行为的调查

2005年威海市经济技术开发区泊于镇被定为国家级疟疾监测点，为掌握基线资料和制定新的疟防措施提供科学依据，对监测点的居民进行了疟防知识、态度和行为（KAP）调查。     

Pathology of falciparum malaria in Vietnam.

Autopsy samples from the brains of 20 patients who died of falciparum malaria were examined by light microscopy and by an immunohistologic method. Particular attention was paid to a comparison of the pathologic features of the white matter and the cortex. In the high-sequestration (greater than 50%) group (n = 8), the mean +/- SD percentage of cerebral microvessels that showed parasitized red blood cell (PRBC) sequestration was 71.2 +/- 8.1% in the cortex and 84.0 +/- 6.7% in the white matter. The difference in the PRBC sequestration rate between cortex and white matter was statistically significant (P less than 0.01). Perivascular and ring hemorrhages were seen more frequently in the white matter than in the cortex. Deposition of IgG and Plasmodium falciparum antigen in the cerebral microvessels was more highly significant in the white matter than in the cortex (P less than 0.01). Our study demonstrated that the localized concentration of PRBC sequestration in the brain correlated with the marked immunohistologic differences in the microvessels of cortex and white matter.     

河南省疟疾防治研究回顾

本文从病原学、流行病学、诊断学、传播媒介和现场控制等方面回顾了河南省疟疾防治研究所取得的成果，并根据疟疾流行的现状，提出了将来的研究方向。     

How local community knowledge about malaria affects insecticide-treated net use in northern Ghana

Large-scale trials of insecticide-treated nets (ITNs) throughout Sub-Saharan Africa demonstrated that they reduce child mortality in malaria endemic communities. These encouraging results have generated interest in ITNs as a viable malaria control strategy in many malaria endemic countries. However, regular use of ITNs under routine or non-project conditions has been beset with several problems. This paper explores how local community knowledge about malaria acts as a barrier to the use of ITNs in three settings. We employed structured formal observation and a range of interviewing techniques which included informal interviews, focus group discussions, semi-structured in-depth interviews, and structured survey interviewing. People recognize the term 'malaria' but have limited biomedical knowledge of the disease, including its aetiology, the role of the vector, and host response. Convulsions and anaemia are rarely linked to malaria. The people acknowledged a role for ITNs in nuisance reduction, but not for malaria prevention.     

Performance characteristics and quality control of community based ultrasound surveys for cystic and alveolar echinococcosis

The probability of disease given the results of a test, is called the predictive value of the test. The predictive value of a test is not a property of the test itself but will vary according to the prevalence of the disease in the studied population. The positive predictive value (PPV) is the probability that the subject tested has the disease given that a positive result is obtained. The negative predictive value (NPV) is the probability that the subject tested is normal given that a negative result is obtained. As the prevalence of a disease in a population approaches zero so does the PPV and most of the positive cases will be 'false positives'. Conversely the NPV will be very high at low prevalences and there will be few 'false negative' results. The sensitivity and specificity of a test are properties of the test and do not vary with prevalence. The higher the sensitivity and specificity of a particular test the greater the predictive values will be at any given prevalence of the disease. Ultrasound (US) is increasingly used for detecting lesions due to cystic and alveolar echinococcosis (CE and AE) and portable US scanners facilitate community based mass screening surveys in remote rural communities. Screening is justified with AE and CE in endemic areas as diagnosis at an early stage can lead to a better prognosis following treatment. The sensitivity and specificity of US has been reported to be between 88-98% and 95-100% respectively for CE and the sensitivity is a little higher for AE. Both species have pathognomonic signs on US and the technique is considered to be the 'gold standard' although it is still an imperfect test. Clinical, laboratory and epidemiological data also play an important role in the diagnosis of CE and AE. US results where possible, should be evaluated in relation to these findings. Suspected CE and AE images, may benefit from the use of other imaging techniques such as magnetic resonance imaging, computerised tomography and in the case of AE angiography or cholangiography. Immunological tests or molecular biological techniques also provide a useful back up, especially for AE. As sensitivity and specificity are properties of the US diagnostic test they should not vary if the case mix reported in different studies remains the same. The use of the WHO standardised US classifications for CE and AE should be used so that the properties of the test are standardised. Quality control of field based studies will depend on geographical variations in the case mix and the relative proportions of cyst types without pathognomonic signs. The latter will have the most bearing on variations in specificity, as would the use of different classifications. Inter- and intra-observer variability and differences in prevalence will affect the performance of US in different endemic settings. Community based surveys must adhere to the highest ethical standards and the outcome of surveys should result in appropriate treatment and follow-up strategies for all infected individuals and suspected cases found during the surveys.     

云南省元阳县高疟山区中小学生疟疾KAP调查

目的揭示当地人群对疟疾的认识和防治方面的行为特点。方法对元江流域贫困山区疟疾高发区的 473名中小学生进行疟疾 KAP问卷调查。结果 44.6%的人最怕的疾病是疟疾 ,1 8.8%、2 4.5 %和 8.7%的人分别认为疟疾是由喝生水、洗冷水澡和鬼神作怪引起。他们只有 3 5 .3 %的人有蚊帐 ,其中 5 0 .9%的人经常使用 ,3 8.9%的人有时用 ,1 0 .2 %的人从不使用 ;其不用的原因 47.1 %的人不知道用蚊帐的好处 ,2 9.4%的人是怕麻烦 ,2 3 .5 %的人怕热。平时生病 4.4%的人不看医生 ,3 5 .7%的人有时看 ;其原因 1 9.0 %的人没有钱 ,1 4.3 %的人是医院较远 ,42 .9%的人是家长未带去 ,2 3 .8%的人是认为看医生也看不好。家里人生病时 3 2 .1 %的家庭有求神送鬼行为。结论这些特点严重的影响了疟防措施的落实和实施 ,建议通过普及中小学生的疟防知识 ,提高整个人群的自我防护意识 ,促进各项抗疟措施的落实和实施。     

The need for health behaviour and socio-economic research in malaria control in Thailand

Malaria is still a disease of public health importance in Thailand despite the encouraging downward trend in the number of malaria cases during the past ten years. In the last few years there were still nearly a quarter of million malaria cases detected and about 3,000 malaria deaths yearly reported. The social and economic factors seem to play major roles in keeping low persistent transmission of malaria in certain communities especially those residing in and near forested areas, mountains and foothills in the places not far away from Thai-Kampuchea border in East Thailand and Thai-Burmese border in West Thailand. These communities consist of migrants and local native residents living in newly opened lands for agriculture, and some are remote areas where communication and transportation are inaccessible. Preliminary results on these people revealed some interesting social and economic problems and health behaviour of the people in connection with persistent malaria transmission among them. It is suggested that further investigation should be carried out on the social and economic elements in these communities including migratory pattern, their population characteristics and life, social behaviour, health belief and practice, malaria prone behaviour, etc. in association with malaria transmission among them. The results to be obtained may lead to the effective control measures of malaria in future.     

Knowledge and beliefs about malaria transmission and practices for vector control in southern Mexico

OBJECTIVE: To investigate the knowledge and beliefs about malaria transmission and practices for vector control in eight villages on the coastal plain of Chiapas, Mexico. MATERIAL AND METHODS: A cross-sectional survey was conducted during May and June 1995 in Chiapas, Mexico. A questionnaire to investigate family structure, knowledge on malaria transmission, preventive measures and attitudes towards seeking treatment was applied to both family heads of a sample of households. Associations were analyzed by estimating odds ratios with confidence intervals and p values, using bivariate and multivariate logistic regression methods. RESULTS: Malaria knowledge was poor and only 48% associated malaria with mosquito bites. The perceived benefit of indoor residual spraying was associated to a reduction of mosquitoes, a reduction in the numbers of cockroaches and rats, but only 3% associated it directly with the prevention of malaria transmission. Most villagers (97.6%) agreed with the indoor residual spraying of insecticides. Ninety nine percent of villagers had mosquito bednets, 75.7% used them all year round. Other measures used by villagers to prevent mosquito bites were smoke and mosquito coils. Above 40% of villagers self-medicated when any member of the family had a fever episode, but 51% attended proper health services (community dispensary, private physician, health worker). About 61% used pesticides for agricultural or livestock purposes and 55% applied themselves. Women had a greater participation as family health promoters, with 70% of the housewives being in charge of the application of self-protection preventive measures. CONCLUSIONS: Educational programs aimed at increasing awareness on the participation of mosquitoes on malaria transmission could promote community participation in malaria control in the region. The English version of this paper is available too at: http://www.insp.mx/salud/index.html.     

INTERSALT in Italy: findings and community health implications

In INTERSALT, an international cooperative study on electrolytes and blood pressure, significant associations were found, in the pooled data for 52 centres, between systolic BP and sodium (Na) excretion, body mass index (BMI), high alcohol intake and low potassium (K) excretion. We have assessed the status of the four Italian centres (Mirano, Gubbio, Bassiano, Naples) on these variables. The four centres examined a total of 794 men and women aged 20-59 years. Combined values were similar to overall INTERSALT levels for daily Na excretion (170 mmol) and BMI (25 kg/m2). The Italian centres had slightly higher potassium excretions (57 vs. 55 mmol/day), a higher prevalence of drinkers and a greater average alcohol consumption. Participants were divided into those below or above median levels of Na, K, BMI, and by alcohol intake (below or above 300 ml/week). Both systolic BP and diastolic BP were found to be lower in the more favourable stratum, for each variable. When all four factors were combined, those below median Na excretion and BMI, above median K, and with alcohol intake less than 300 ml/week had age-adjusted systolic BP 7.5 mmHg lower than those with less favourable levels of all four variables. The difference in adjusted diastolic BP was 4.3 mmHg. The data indicate the potential for lower population average BP with improved lifestyles.