Rice irrigation and schistosomiasis in savannah and forest areas of Côte d'Ivoire.

Prevalence and intensity of infection of Schistosoma haematobium and Schistosoma mansoni were studied in relation to irrigated rice cultivation in Côte d'Ivoire. Urine and stool samples were collected from 4 to 15-year-old children in 24 villages in the savannah zone and 21 villages in the forest zone. Villages were classified according to surrounding inland valleys into three agro-ecosystems: (R2) full or partial water control allowing two rice cycles per year; (R1) no or partial water control allowing one harvest per year and (R0) absence of rice growing. In the savannah zone, S. haematobium prevalence was 4.8%, 2.3% and 0.7% and S. mansoni prevalence was 16.1%, 11.9% and 2.1% in R2, R1 and R0, respectively. In the forest zone, S. haematobium prevalence was 0.9%, 4.4% and 1.7% and S. mansoni prevalence was 61.3%, 46.6% and 17.5% in R2, in R1 and R0, respectively. Prevalences of S. mansoni adjusted for village effects were significantly different between agro-ecosystems in both zones. Significance of differences between agro-ecosystems of S. haematobium infection were strongly influenced by outlying villages. In savannah rice growing villages, negative binomial regression on infection intensity of each species showed significant positive relations to the surface of rice cultivated inland valleys, whereas uncultivated inland valleys showed no significant relation. However, in forest rice growing villages, S. mansoni infection intensity showed significant positive relations to the surface of uncultivated inland valleys, whereas surface water on rice cultivated land showed significant negative relations with infection intensity of each schistosomiasis species.

Inland valley rice production systems and malaria infection and disease in the savannah of Côte d'Ivoire.

In sub-Saharan Africa, lowlands developed for rice cultivation favour the development of Anopheles gambiae s. l. populations. However, the epidemiological impact is not clearly determined. The importance of malaria was compared in terms of prevalence and parasite density of infections as well as in terms of disease incidence between three agroecosystems: (i) uncultivated lowlands, 'R0', (ii) lowlands with one annual rice cultivation in the rainy season, 'R1' and (iii) developed lowlands with two annual rice cultivation cycles, 'R2'. We clinically monitored 2000 people of all age groups, selected randomly in each agroecosystem, for 40 days (in eight periods of five consecutive days scheduled every 6 weeks for 1 year). During each survey, a systematic blood sample was taken from every sick and asymptomatic person. The three agroecosystems presented a high endemic situation with a malaria transmission rate of 139-158 infective bites per person per year. The age-standardized annual malaria incidence reached 0.9 malaria episodes per person in R0, 0.6 in R1 and 0.8 in R2. Children from 0 to 9-year-old in R0 and R2 had two malarial attacks annually, but this was less in R1 (1.4 malaria episodes per child per year). Malaria incidence varied with season and agroecosystem. In parallel with transmission, a high malaria risk occurs temporarily at the beginning of the dry season in R2, but not in R0 and R1. Development of areas for rice cultivation does not modify the annual incidence of malarial attacks despite their seasonal influence on malaria risk. However, the lower malaria morbidity rate in R1 could be explained by socio-economic and cultural factors.

[Surgical lengthening of the lower face in patients with class II deformities and skeletal deep bite--"short face syndrome" controlled clinical study on the "Würzburger Konzept"]. / Chirurgische Untergesichts--verlängerung bei der Therapie von Patienten mit Klasse-II-dysgnathien und skelettal tiefem Biss--"Short-face-Syndrom". Kontrollierte klinische Studie zum "Würzburger Konzept"

Among Angle Class II patients scheduled for orthognathic surgery, those with short face syndrome with skeletal deep bite only make up a small portion. Nevertheless, it represents a complex challenge for the orthodontist as well as for the surgeon with respect to the individual treatment goals. The harmony of facial relations is impaired in these patients: The skeletal lower face and consequently the soft tissue profile show a deficit in height compared to the midface. Lengthening of the lower face with its respective effect on facial aesthetics can only be corrected by causal therapy, i.e., a combined approach with surgical enlargement of the gonion angle. In this study, a therapy concept specifically suited for the correction of Class II deformities with short face syndrome is presented. Consequences for the skeletal and dental situation with their benefit for extraoral appearance were tested in a clinical trial ( n=15, patients with class II deformities and short face syndrome). To evaluate skeletal and dental changes, cephalograms were taken prior to initiation of orthodontic treatment, 3 days after surgery but before initiation of postsurgery orthodontics, and 1 year after the end of treatment.

Comparison of incisor mobility after insertion of canine-to-canine lingual retainers bonded to two or to six teeth. A clinical study.

BACKGROUND: Fixed appliance therapy often extends over several years. Debonding is warmly welcomed and is often seen by the patient as the end of treatment. Yet both patients and parents often underestimate the importance of the subsequent retention period and the speed at which negligence in this treatment phase results in relapse. Bonded retainers guarantee excellent long-term stability at least while they are in situ. The reliable attachment of lingual retainers with modern bonding techniques has led to widespread application of this retention method. The present study investigated its influence on tooth mobility and on the damping properties of the periodontal tissue, by means of a dynamic measuring method (Periotest). PATIENTS AND METHOD: For this purpose two groups with mandibular bonded retainers and one control group were formed. The control group wore removable retention appliances. In all groups, active treatment with fixed appliances had been completed at least half a year before baseline. RESULTS: The results showed that bonded retainers had a negative impact on the damping properties of the periodontal tissue and thus in the broader sense on tooth mobility. Tooth mobility decreased with the number of teeth to which the retainer was bonded but remained, as in the control group, within the physiologic range.

An empirical malaria distribution map for West Africa.

The objective of this study was to produce a malaria distribution map that would constitute a useful tool for development and health planners in West Africa. The recently created continental database of malaria survey results (MARA/ARMA 1998) provides the opportunity for producing empirical models and maps of malaria distribution at a regional and eventually at a continental level. This paper reports on the mapping of malaria distribution for sub-Saharan West Africa based on these data. The strategy was to undertake a spatial statistical analysis of malaria parasite prevalence in relation to those potential bio-physical environmental factors involved in the distribution of malaria transmission intensity which are readily available at any map location. The resulting model was then used to predict parasite prevalence for the whole of West Africa. We also produced estimates of the proportion of population of each country in the region exposed to various categories of risk to show the impact that malaria is having on individual countries. The data represent a very large sample of children in West Africa. It constitutes a first attempt to produce a malaria risk map of the West African region, based entirely on malariometric data. We anticipate that it will provide useful additional guidance to control programme managers, and that it can be refined once sufficient additional data become available.

Age dependence of the multiplicity of Plasmodium falciparum infections and of other malariological indices in an area of high endemicity.

The relationship between age and various malariological indices in the Kilombero valley of Tanzania were examined by compiling data from 6 different community studies carried out between 1989 and 1996. The rate of acquisition of Plasmodium falciparum infection was highest in children 1-5 years of age, while recovery rates were lowest between the first birthday and early adolescence. As a result, peak prevalence was reached in 3-5 years old children. However, the prevalence of clinical malaria (estimated from the excess risk of axillary temperatures > or = 37.5 degrees C attributable to parasitaemia) was highest in children under one year of age. The peak in multiplicity of infection (identified by polymerase chain reaction-restriction fragment length polymorphism of the msp2 locus) occurred in 3-7 years old children. There was a significant correlation between parasite density and multiplicity of infection in infants and young children (1-2 years of age) but not in older individuals.

An atlas of malaria in Africa.

PIP: The Mapping Malaria Risk in Africa (MARA) project will use computerized geographic information systems (GIS) to create an atlas of malaria risk in Africa. This is the first time GIS will be used to predict such risk and the first attempt to map malaria risk on a continental scale. Many heterogenous data sets relevant to the transmission dynamics of the disease will be combined, including the manipulation of the climatic factors which affect vector distribution and malaria transmission into a new index of malaria risk, and its validation against actual data. Specifically, the MARA project will collate measures of malaria risk, mainly the parasite ratio and annual incidence, to obtain an index for Africa and to create a continental, spatial, and temporal database. Five planned regional centers will work with a coordinating center in Durban, South Africa. The effort recently received its first funding. Canada's International Development Research Center, the World Health Organization/TDR bednet task force, the Wellcome Trust, and the South African Medical Research Council are supporting the effort.^ieng

Is fever a good sign for clinical malaria in surveys of endemic communities?

Although fever is the characteristic sign of clinical malaria, many Plasmodium falciparum malaria cases in endemic areas do not present with measurable temperature elevations. In a field study in Tanzania, malaria morbidity was defined to be any current self- or parentally reported illness associated with malaria parasite densities higher than those in healthy individuals. Without diagnosis of individual episodes, prevalences of malaria-attributable morbidity of 9.8% in infants, 1.3% in children 1-4 years of age, and 0.6% in those 5-9 years of age were estimated. No illness was considered to be due to malaria in older individuals. In infants, 66.5% of malaria-attributable morbidity episodes corresponded to axillary temperatures < 37.5 degrees C. In older children, most of the episodes due to malaria corresponded to increased temperatures. This age dependence should be considered when designing diagnostic procedures and outcome measures for epidemiologic studies of malaria.

Random mating in a natural population of the malaria parasite Plasmodium falciparum.

The genetic structure of a population of the malaria parasite Plasmodium falciparum has been examined in a village in Tanzania. Seventeen alleles of the merozoite surface protein MSP-1 and 23 of MSP-2 were detected by the polymerase chain reaction (PCR) among the blood parasites of the inhabitants. Most infections contained mixtures of genetically distinct parasite clones. PCR was then used to examine individual P. falciparum oocysts, the products of fertilization events, in wild-caught mosquitoes. Forty-five out of 71 oocysts were heterozygous for one or both genes, showing that crossing between clones was taking place frequently, following uptake of mixtures of gametocytes by the mosquitoes. The frequency of heterozygous forms showed that random mating events probably occurred within mosquito bloodmeals between gametes belonging to different parasite clones.

Severe childhood malaria in two areas of markedly different falciparum transmission in east Africa.

Malaria remains a major public health challenge in sub-Saharan Africa, yet our knowledge of the epidemiology of malaria in terms of patterns of mortality and morbidity is limited. We have examined the presentation of severe, potentially life-threatening malaria to district hospitals in two very different transmission settings: Kilifi, Kenya with low seasonal transmission and Ifakara, Tanzania with high seasonal transmission. The minimum annual rates of severe disease in children below five years in both populations were similar (46 per 1000 children in Kilifi and 51 per 1000 children in Ifakara). However, there were important differences in the age and clinical patterns of severe disease; twice as many patients were under one year of age in Ifakara compared with Kilifi and there was a four fold higher rate of cerebral malaria and three fold lower rate of malaria anaemia among malaria patients at Kilifi compared with Ifakara. Reducing malaria transmission in Ifakara by 95%, for example with insecticide-treated bed nets, would result in a transmission setting comparable to that of Kilifi and although this reduction may yield early successes in reducing severe malaria morbidity and mortality in young, immunologically naive children, place these same children at increased risk at older ages of developing severe and potentially different manifestations of malaria infection hence producing no net cohort gain in survivorship from potentially fatal malaria.

Do high levels of C-reactive protein in Tanzanian children indicate malaria morbidity.

Children under 6 years of age living in an area of Tanzania highly endemic for malaria were tested for C-reactive protein (CRP) in order to determine how the acute-phase response is related to malaria in children of different ages and to investigate whether serum CRP concentrations might be useful in the qualification of morbidity in such children. The median CRP level in the 629 finger-prick blood samples measured, 6.0 mg/liter, was much higher than that reported in the blood of children in Europe. The CRP concentration was correlated with recent illness reported by the parents. High CRP levels were most strongly associated with Plasmodium falciparum parasitemia in children under 1 year of age. In older children, lower levels of CRP were associated with parasitemia, and fewer children had increased CRP levels attributable to parasitemia. The levels of malaria-attributable CRP appear to track the acquisition of parasitological and clinical tolerance in this area with very high levels of P. falciparum transmission. Determination of CRP levels should be useful in the rapid assessment of the overall burden of morbidity, especially in infants. In areas where malaria is endemic, CRP associated with increased parasite densities provides an objective measure of malaria-specific morbidity. This would be an efficient approach to estimating malaria morbidity risks from small-scale serological surveys.

Evaluation of C-reactive protein and haptoglobin as malaria episode markers in an area of high transmission in Africa.

Field studies of malaria in endemic areas frequently use the presence or levels of parasitaemia, together with the measurement of fever, as the primary criteria with which to identify cases. However, since malaria cases do not always present with measurable fever, and since asymptomatic parasitaemia occurs, additional episode markers might be useful epidemiological tools. We have measured the C-reactive protein and haptoglobin levels in paediatric patients presenting to a village health post in the Kilombero District in Tanzania and in convalescent sera from the same patients, in order to evaluate these acute-phase reactants as alternative markers of Plasmodium falciparum episodes. Among afebrile patients, C-reactive protein levels were highly correlated with parasite density. High C-reactive protein levels are therefore probably indicative of recent clinical malaria episodes in currently afebrile individuals with high parasite densities. An appropriate case definition for malaria in epidemiological studies in endemic areas might therefore be hyperparasitaemia accompanied by either, or both, measurable fever and raised C-reactive protein levels. This would give less biased estimates of the overall burden of malaria morbidity than does a definition which requires measurable fever. Levels of haptoglobin were highly negatively correlated with parasitaemia, but did not appear to be useful episode markers because this correlation was probably not related to acute morbidity. However, haptoglobin can be useful to assess at community level the impact of interventions on parasitaemia.

SPf66, a chemically synthesized subunit malaria vaccine, is safe and immunogenic in Tanzanians exposed to intense malaria transmission.

As part of the first trial of the SPf66 malaria vaccine in Africa, three randomized double-blind placebo-controlled studies of SPf66 have been conducted in a highly endemic area of Tanzania. The objectives were to confirm that the product is immunogenic and safe in highly exposed individuals. Results from ten male adult expatriates indicated that the product used in Tanzania is at least as immunogenic as that used in Colombia. No major side-effects were observed in indigenous SPf66 recipients (18 adults, and 25 children aged 1-4 years). Anti-SPf66 antibody titres in all groups showed clear responses to three doses of the vaccine.

Assessment of process quality in Tanzanian primary care.

Process quality is the commonly used operational definition of health care quality. Its key components are technical and inter-personal skills, but most assessments undertaken in developing countries focus only on technical skills. This study from Tanzania used explicit observation checklists to review the process of providing antenatal, curative and nursing care in primary health units, assessing both technical and inter-personal skills. The study findings emphasize the weaknesses in available care, particularly in the attitudes of health staff but also in aspects of technical care. Differences in performance between health units appear to be influenced by factors such as workloads, structure and staff allocations. Differences between cadres were also identified and may underlie some of the inter-unit differences. The policy actions required to address the problems must reflect the diversity of the underlying influences, seeking to raise both technical and inter-personal quality, as the two are mutually reinforcing.

Childhood anemia in Africa: to transfuse or not transfuse?

Blood transfusions are an important route for HIV transmission in Africa. To explore whether transfusions are necessary in the case management of childhood anemia, a randomized trial was performed in Ifakara, Tanzania, a holoendemic malaria region. 116 children were randomized to receive either treatment for malaria and hookworm alone or, in addition, a transfusion of whole blood which had been tested negative for antibodies against the human immunodeficiency virus. Mean packed cell volume (PCV) at admission was 14.0% in the transfusion and 14.4% in the no transfusion group. Children were followed up for 8 weeks with measurements of PCV at 2 days, 4 weeks and 8 weeks after study entry. PCV was similar in both groups after 4 and 8 weeks (22.9% in the transfusion and 23.6% in the no transfusion group). There was a trend towards more hospital admissions and deaths in the no transfusion group; however, 95% confidence intervals included both a beneficial and an adverse effect of blood transfusions. The costs and benefits of transfusion for childhood anemia in countries with a high HIV prevalence need to be considered carefully before a rational treatment policy can be adopted. For that purpose, a larger randomized trial is urgently needed.

Maternal recall of symptoms associated with childhood deaths in rural east Africa.

Verbal autopsies (VA) are frequently used to determine causes of death for individuals for whom there is no reliable clinical information regarding the terminal illness. VA interviews are used to note key symptoms and signs recalled by relatives of the deceased and diagnoses ascribed according to the symptom complexes. The VA technique assumes that individual disease entities have discrete symptom complexes and that these can be accurately recognized and recalled by the interviewees. We have examined the accuracy with which specific symptoms are recalled over time by mothers or normal guardians of 491 children who died on the paediatric wards of two district hospitals in East Africa. Kwashiorkor, measles, trauma, generalized convulsions and neonatal tetanus were all reported with a high degree of accuracy for children who died of these conditions and had low false positive rates for children without these conditions. Recall was similar within 1 month of death compared to recall after 6 months for most symptoms and signs except neonatal tetanus where false positive reports by mothers increased with time since death. Symptoms and signs commonly used to describe malaria, respiratory tract and diarrhoea-related deaths were reported by mothers to have been present during the terminal illness in 43% of cases where these features were absent. Recall abilities differed between the two communities studied for some symptoms and signs highlighting the importance of such studies in every setting where VA are applied.

PIP: Verbal autopsies (VA) are widely used by population and health scientists to determine individual causes of death in areas where most deaths occur at home and well-documented clinical data on cause of death are usually unavailable. VA interviews are based upon key symptoms and signs recalled by relatives of the deceased. In order to assess the reliability of the technique, the accuracy with which mothers and normal guardians recognize and recalled specific symptoms and clinical signs over time was assessed in the cases of 491 children who died on the pediatric wards of 2 district hospitals in Ifakara, Tanzania, and Kilifi, Kenya. The bereaved were interviewed 3 days to 24 months after child death. Recall after 1 month was similar to recall after 6 months for most signs and symptoms except neonatal tetanus for which false positives reported by mothers increased with time after death. Kwashiorkor, measles, trauma, generalized convulsions, and neonatal tetanus were reported with a high degree of accuracy. Symptoms and signs commonly used to describe malaria, respiratory tract and diarrhea- related deaths, however, were reported by mothers to have been present during terminal illness in 43% of cases where the features were absent. Finally, recall abilities differed between the 2 communities studied.

Absence of seasonal variation in malaria parasitaemia in an area of intense seasonal transmission.

Parasitological surveys carried out in two villages of the Kilombero district of Tanzania indicated a very high prevalence of Plasmodium falciparum parasitaemia throughout the year (all ages mean prevalence = 69.2%) and a low, unstable prevalence of P. malariae (all ages mean prevalence = 4.5%). Fevers (temperature > or = 37.5 degrees C) in both children and adults showed irregular changes in prevalence over time, but there was no seasonal pattern. Neither was there seasonal variation in either P. falciparum parasite prevalence or parasite densities. This was despite marked seasonality in vectors caught in CDC light-traps and in estimated sporozoite inoculations determined by ELISA. The estimated mean annual inoculation rate was extremely high, over 300 infectious bites per person per year, the main vectors being members of the A. gambiae complex and Anopheles funestus. There was considerable variation between houses but even in houses with relatively low mosquito numbers the inoculation rate was sufficient to maintain a maximal P. falciparum prevalence. Heterogeneities in exposure cannot explain why the parasite prevalence is not always 100%. In areas of such high transmission, parasitaemias are likely to be determined mainly by the interaction of schizogony and anti-blood stage immunity, since parasites arising from new inoculations generally comprise only a small proportion of the total in the circulation. In any one individual, this will lead to periodic fluctuations in levels of parasitaemia. These are unlikely to show a close relationship to either seasonal variation in inoculations or to differences between households in the local inoculation rate.