Bacteraemia in cerebral malaria

As part of a treatment trial of cerebral malaria, blood cultures were done in 276 Gambian children, aged between 1 and 9 years, with cerebral malaria. Fourteen (5%) of these were positive. The organisms isolated were Staphylococcus aureus (6), coliforms (4), Pseudomonas spp. (2), Salmonella spp. (1) and Streptococcus spp. (1). Thirteen of these children survived, most without appropriate antibiotic treatment. Most of the retrieved organisms were therefore suspected to be contaminants. Bacteraemia complicating cerebral malaria is not common in The Gambia, and routine antibiotic treatment of children with cerebral malaria is not warranted.

Causes of mortality in twins in a rural region of The Gambia, West Africa

Little is known about birth or mortality rates of twins in The Gambia. There are no reports of the causes of death among twins in sub-Saharan Africa. We identified twin births and deaths from a community-based study which had been carried out in a large rural region of The Gambia over a 5-year period from 1989 to 1993. The overall twinning rate excluding stillbirths was 14.3 (95% CI 12.9, 15.8) per 1000 live deliveries. This was significantly lower among the Mandinka ethnic group (8.8 per 1000) than among the Serahulis (15.1 per 1000) or Fulas (18.3 per 1000). The early-neonatal, late-neonatal and post-neonatal twin mortality rates were 114.0, 45.9 and 64.2 per 1000 live twin births, respectively. In comparison, the early-neonatal, late-neonatal and post-neonatal mortality rates of singletons were 18.6, 16.0 and 41.1 per 1000, respectively. In the post-neonatal period, malnutrition was more frequently a cause of death among twins than among singletons (7.8 per 1000 twin births vs 2.0 per 1000 singleton births; p = 0.0008). Appropriate strategies for preventing malnutrition are required for this high-risk group.

A randomized controlled trial of artemether/benflumetol, a new antimalarial and pyrimethamine/sulfadoxine in the treatment of uncomplicated falciparum malaria in African children

We report here the results of a randomized double blind trial comparing coartemether (CGP56697), a combination of artemether and benflumetol, with pyrimethamine/sulfadoxine (P/S). Two hundred eighty-seven children 1-5 years of age with uncomplicated falciparum malaria were enrolled at two centers in The Gambia between July 1996 and December 1996. Following treatment, children were visited at home every 24 hr until a blood film free of asexual parasites was obtained. Genotyping of parasites was used to distinguish recrudescence from new infections. Three days after the start of treatment, 133 (100%) of the CGP56697-treated children compared with 128 (93.4%) of children treated with P/S had cleared their parasites (P = 0.003). The day 15 cure rate was 93.3% for CGP56697 and 97.7% for P/S (P = 0.13). Within the third and fourth week after initiation of therapy, 20 children treated with CGP56697 and one of the P/S-treated children returned with second malaria episodes (P < 0.0001). Genotyping suggested that the majority (19 of 23 [82.6%]) of these second episodes were due to new infections, supporting the World Health Organization recommendation that longer follow-up is not relevant for the assessment of drug efficacy. At the two-week follow-up, 28.9% of the P/S treated children but none of the CGP56697-treated children carried gametocytes (P < 0.0001). This study showed that CGP56697 is safe in African children with acute uncomplicated falciparum malaria, clears parasites more rapidly than P/S, and results in fewer gametocyte carriers. More frequent new infections within the third and fourth week following treatment with CGP56697 than treatment with P/S are likely to be due to the short prophylactic effect of CGP56697.

A polymerase chain reaction for the diagnosis of Haemophilus influenzae type b disease in children and its evaluation during a vaccine trial

BACKGROUND

Determination of the etiology of pneumonia in young children is difficult because blood culture, the usual method of diagnosis, is positive in only a small proportion of cases. For this reason vaccine trials that include bacterial pneumonia as an endpoint must be large.

OBJECTIVES

To determine whether a diagnostic test based on a polymerase chain reaction could be used as an alternative to conventional blood culture for diagnosis of invasive Haemophilus influenzae type b (Hib) infections in young children investigated during the course of a large vaccine trial.

METHODS

DNA was extracted from blood culture supernatants and probed for the presence of Hib DNA with a PCR assay with primers derived from the cap gene locus of Hib. Results of the PCR assay were compared with those obtained by conventional culture techniques.

RESULTS

Blood cultures were obtained from 1544 children with suspected pneumonia, meningitis or septicemia and from 31 healthy control children who were contacts of cases. Blood culture supernatants were tested for Hib DNA in the PCR test. The sensitivity and specificity of a positive PCR test in blood culture supernatant as against culture of Hib from any normally sterile site were 100 and 99%, respectively. Eleven children had positive Hib PCR tests on blood culture supernatants but were negative by culture. In one of these cases Hib was isolated from a lung aspirate and in two other patients H. influenzae strains other than Hib were obtained from the cerebrospinal fluid. Eight of these 11 children were in the control group. When the results of the PCR assay were used to determine vaccine efficacy, a value of 86% was obtained compared with a figure of 95% obtained when conventional culture techniques were used.

CONCLUSIONS

An Hib PCR assay on blood culture supernatants proved to be sensitive and specific for the diagnosis of Hib disease in children. The distribution of PCR-positive, culture-negative cases between Hib-vaccinated and control groups paralleled that of culture-positive cases, suggesting that most of these children had been infected with Hib. A trial of a highly efficacious vaccine provides a novel way for evaluating new diagnostic tests for which there is no standard diagnostic test of 100% reliability.

Traditional medicine to DNA vaccines: the advance of medical research in West Africa

West Africa has a rich medical history. Herbal medicine has been practiced for hundreds of years and the establishment of an effective herbal pharmacopoeia was probably the first medical research carried out in West Africa. Arabic medicine was practiced in the countries of the Sahel in the 15th and 16th centuries. The coming of the Europeans focused research on infectious diseases such as malaria, yellow fever and sleeping sickness, to which Europeans were very susceptible and which caused devastating epidemics among the populations of their new colonies. The end of the colonial era saw the establishment of a few large, well-equipped teaching hospitals but these proved too expensive for the newly independent states of West Africa to run effectively, and the second generation of West African medical schools was based on more modest government hospitals. This led to a change in the focus of research away from the more unusual conditions seen in a specialist referral hospital to an interest in conditions, such as the common infectious diseases, seen more frequently in district hospitals. The advent of the primary health care movement in the 1970s was followed by an increased emphasis on community studies. Molecular biology is likely to have an enormous impact on medicine in general in the coming years. One of the main challenges facing medical researchers in West Africa is how these new technologies can be used most effectively to improve health in countries with limited resources.

Meal type affects heartburn severity

This study compared heartburn severity, number of episodes, and changes in esophageal pH induced by three meals. Symptomatic volunteers consumed the following on different occasions: McDonald's Quarter Pounder, french fries, and chocolate shake; McDonald's Sausage Biscuit with Egg, cheese, raw onion, and chocolate milk; and Wendy's Chili and red wine. Increases in reflux episodes over baseline for the hamburger, sausage biscuit, and chili meals were 28.8 +/- 5.7, 36 +/- 5.5 and 43.7 +/- 8.8, respectively. The sausage biscuit and chili increased reflux compared to the hamburger (P < 0.05), but the chili did not differ statistically from the sausage biscuit meal. Onset and peak heartburn for the hamburger, sausage biscuit, and chili meals were 45 and 90, 30 and 120, and 15 and 150 min, respectively. Despite lower fat content, chili and red wine promoted more reflux and heartburn pain than the other meals, demonstrating the importance of meal selection in provocative meal studies.

The Gambian National Impregnated Bednet Programme: costs, consequences and net cost-effectiveness

Clinical trials have indicated that treating mosquito nets with insecticide could be a potentially cost-effective method of preventing malaria. As malaria is one of the most common causes of death in children under five in developing countries, there has been substantial interest in whether such findings can be replicated for a country's control programme in practice. The cost-effectiveness of the Gambian National Insecticide-impregnated Bednet Programme (NIBP), from the viewpoint of providers (government and non-governmental agencies) and the community, has been calculated. Information was collected from existing records, interviews with NIBP personnel, observation and household surveys. Information is provided on the resource use consequences of the NIBP in terms of reduced expenditure on anti-malaria preventive measures, treatment in government health services, household financed treatment and "charity" (burial, funeral and mourning activities), as well as cash income lost as a result of child death. The annual implementation cost of the NIBP was D757,875 (US$91,864), of which 86% was recurrent cost. The estimated number of death averted was 40.56. The net implementation cost-effectiveness ratio per death averted and discounted life years gained were D3884 (US$471) and D260 (US$31.5), respectively. Adding the cost of all mosquito nets would increase the cost-effectiveness ratios by over five times, which is an important consideration for countries with a lower coverage of mosquito nets per capita. It is concluded that insecticide-impregnated mosquito nets are one of the more efficient ways of reducing deaths in children under 10 years in rural Gambia.

Epidemiology of invasive pneumococcal disease in the Western Region, The Gambia

BACKGROUND

Streptococcus pneumoniae is a major cause of morbidity and mortality in young children in the developing world. The recent development of pneumococcal polysaccharide/protein conjugate vaccines may make possible prevention of this infection. However, little is known about the epidemiology of invasive pneumococcal disease in children in the developing world.

OBJECTIVES

To determine the incidence and epidemiologic features of invasive pneumococcal disease in children resident in a semiurban area of The Gambia.

METHOD

The study was part of a large trial of an Haemophilus influenzae type b vaccine that recruited 42 848 children at the age of 2 months during the period March, 1993, to October, 1995. Follow-up of study children continued until December 31, 1995; therefore the first children to enter the trial were followed for 2.5 years and the last for just a few months. During the period of surveillance, 2256 children were investigated for possible invasive pneumococcal disease when they presented to a hospital or health center.

RESULTS

We detected 110 cases of pneumococcal disease. Pneumonia was the most common form of invasive pneumococcal disease observed (75.5% of patients). The incidence of pneumococcal disease was 224 [95% confidence interval (CI) 171, 277] per 100,000 child years among children ages 2 to 11 months, 139 (95% CI 93, 184) per 100,000 among children ages 12 to 23 months and 82 (95% CI 21, 143) per 100,000 among children ages 24 to 35 months. Pneumococci of serogroups 14, 6, 5, 23, 19, 46 and 2 were isolated most frequently. Susceptibility to pneumococcal disease was not increased significantly among Haemophilus influenzae type b-vaccinated children.

CONCLUSIONS

The pneumococcus is a major cause of bacterial infection in The Gambia. A proposed nine-valent pneumococcal conjugate vaccine for developing countries containing conjugates of serogroups 1, 4, 5, 6, 9, 14, 18, 19 and 23 would cover 74% of cases of invasive pneumococcal disease in children resident in the Western Region of The Gambia.

Effects of oral rabeprazole on oesophageal and gastric pH in patients with gastro-oesophageal reflux disease

BACKGROUND

This study examined the dose-response effects of the new proton-pump inhibitor rabeprazole on oesophageal and gastric pH in patients with gastro-oesophageal reflux disease.

METHODS

This study had a single-centre, double-blind, randomized, two-way crossover design. Twenty patients were treated for two 7-day periods separated by a 7-10-day washout period. Patients were randomly assigned to receive either 20 mg of rabeprazole once daily during the first treatment period and 40 mg once daily during the second treatment period, or 40 mg during the first treatment period and 20 mg during the second treatment period. The primary efficacy variable was oesophageal acid exposure determined by 24-hour ambulatory pH monitoring. Acid-reflux time was defined as the percentage of time over 24 h that oesophageal pH was < 4. A dosage was considered effective if reflux time was reduced to < 6%, a number which has been our internal laboratory reference.

RESULTS

Both rabeprazole 20 mg and 40 mg, given once daily, normalized reflux time, with decreases of 79% and 92% in acid exposure by day 7. Both dosages also decreased the mean total number of reflux episodes and the number of episodes lasting > 5 min, with no significant differences between dosages for any reflux parameter. Mean gastric pH increased with 20 mg from 1.86 at baseline to 3.71 on day 1 and 4.17 on day 7. Rabeprazole 40 mg once daily increased gastric pH from 2.01 to 4.37 on day 1, and to 4.65 on day 7. Safety analyses revealed no significant acute side-effects for either dosage.

CONCLUSIONS

Pathological oesophageal acid exposure was normalized with both 20 mg and 40 mg dosages of rabeprazole, and the effects of these two doses did not differ. Rabeprazole was well-tolerated in this short-term study.

Treatment of African children with uncomplicated falciparum malaria with a new antimalarial drug, CGP 56697

New antimalarial drugs are urgently needed. The use of short courses of the new antimalarial drug artemether as monotherapy has been limited by secondary malaria episodes following parasite clearance. Therefore, a new antimalarial drug, CGP 56697, has been developed, which combines artemether with a longer-acting antimalarial agent, benflumetol. A safety trial was undertaken in 60 Gambian children 1-6 years old with uncomplicated Plasmodium falciparum malaria. All children treated with CGP 56697 cleared their parasites 72 h after the start of treatment. No neurologic, cardiac, or other adverse reactions were observed. Second episodes of falciparum malaria were recorded in 16 (27%) of the children. Second infections were more frequent during the rainy season than during the dry season. Molecular epidemiologic studies suggested that 12 of the 14 second episodes of malaria in children treated with CGP 56697 were due to new infections. CGP 56697 proved to be a safe and effective antimalarial drug in African children.

Predictors of a fatal outcome following childhood cerebral malaria

Despite prompt treatment with an effective anti-malarial drug, cerebral malaria still has a mortality of 20-30%. To identify factors that may contribute to this high fatality rate, we have studied the relationship between clinical and laboratory features and a fatal outcome in 624 Gambian children with strictly defined cerebral malaria. One hundred twenty-four children (21.5%) died. Three-quarters of the deaths occurred within 24 hr of admission. Multiple logistic regression analysis showed that a cold periphery (odds ratio [OR] = 2.7), a deep coma (OR = 2.0), and hypoglycemia (OR = 4.1) were the clinical signs and laboratory parameters that predicted death most strongly. More than 90% of the children who died had at least one of these conditions. Also, children with elevated urea levels on admission or those who experienced multiple episodes of hypoglycemia or multiple convulsions subsequently were more likely to die. A combination of clinical and laboratory abnormalities can identify a group of children with cerebral malaria who are most at risk of dying, who require intensive care and who are candidates for new forms of therapy.

The Gambian National Impregnated Bednet Programme: evaluation of the 1994 cost recovery trial

Following the success of a controlled trial of insecticide-impregnated bednets in reducing mortality in children. The Gambia started a National Impregnated Bednet Programme (NIBP) in 1992. The objectives of this programme were to introduce impregnated bednets into all primary health care (PHC) villages and to establish a system of cost recovery over a three-year period. During the initial phase of the programme, when insecticide was given out free, a high uptake was achieved. However, after small user charges were introduced in 1993, coverage dropped to a low level. In 1994, different systems of insecticide distribution and permethrin formulations were tried in an attempt to improve coverage. A nationwide cross-sectional survey carried out during the 1994 rainy season measured coverage by distribution channel, as well as the knowledge, attitudes and practices of health workers and villagers during the intervention. Overall, only 16% of bednets were impregnated in 1994, compared to 80% when the insecticide was offered free of charge in previous years. Lack of money was the major reason given by villagers for not impregnating their bednets in 1994. Use of impregnated bednets was higher in areas where the sale of permethrin emulsion by village health workers was supplemented by the sale of insecticide in individual packages through shops. In villages where insecticide was distributed free to women with small children through governmental mother and child health (MCH) services, higher levels of coverage were achieved among women and young children than in villages where other distribution systems were used. We conclude that the sale of insecticide through the private sector may increase bednet impregnation rates in African communities, and that the free distribution of insecticide through MCH services may be an effective way of targeting young children, the group most at risk of malaria.

Prolongation of the QTc interval in African children treated for falciparum malaria

Antimalarial drugs can affect the heart and trigger life-threatening arrhythmias. However, little is known about the frequency with which cardiac abnormalities occur during uncomplicated attacks of malaria. Therefore, we have studied the electrocardiograms of 139 Gambian children with uncomplicated falciparum malaria who were treated with co-artemether, pyrimethamine/sulfadoxine, or chloriquine. The QTc intervals were measured on presentation, and four and eight days after treatment. No significant differences in mean QTc or heart rate were found between children in the three treatment groups on days 0, 4, or 8. After adjustment for the type of antimalarial thearapy in an analysis of variance, the mean (SD) QTc intervals on days 0, 4, and 8 were 402 (22.6), 416 (23.1), and 405 (24.3) msec, respectively. The mean QTc on day 4 was significantly longer than the mean QTc on days 0 or 8 (P < 0.01 in both cases). A quadratic line was fitted for QTc against time for each antimalarial therapy. No significant differences were found between the quadratic lines of the three groups. A weak association was found between QTc and the degree of parasitemia (r = 0.17, P = 0.04) and temperature (r = -0.23, P = 0.01) measured on day 0. The QTcs were measured in 18 children who experienced a second episode of malaria. The changes in QTc observed during second episodes were similar to those observed during the first attack. Changes in QTc in five children who developed severe malaria were similar to those found in the remaining children who did not develop severe malaria. This study indicates that the QTc interval changes during the early phase of malaria and this change is independent of the type of antimalarial therapy given.

Randomised trial of Haemophilus influenzae type-b tetanus protein conjugate vaccine [corrected] for prevention of pneumonia and meningitis in Gambian infants

BACKGROUND

In developing countries, pneumonia and meningitis due to Haemophilus influenzae type b (Hib) are common in children under age 12 months and the mortality from meningitis is high. Protein-polysaccharide conjugate vaccines have brought Hib disease under control in industrialised countries. We did a double-blind randomised trial in The Gambia to assess the efficacy of a Hib conjugate vaccine for the prevention of meningitis, pneumonia, and other invasive diseases due to Hib.

METHODS

Between March, 1993, and October, 1995, 42,848 infants were randomly allocated the conjugate vaccine Hib polysaccharide tetanus protein (PRP-T) mixed with diphtheria-tetanus-pertussis vaccine (DTP), or DTP alone at age 2 months, 3 months, and 4 months. Children who presented with signs of invasive Hib were investigated by blood culture and, where appropriate, by lumbar puncture, chest radiograph, or percutaneous lung aspirate. Children were followed up for between 5 and 36 months.

FINDINGS

The median ages at which children received the study vaccine were 11 weeks, 18 weeks, and 24 weeks. 83% of children enrolled received all three doses of vaccine. 17 cases of culture-positive Hib pneumonia, 28 of Hib meningitis, and five of other forms of invasive Hib disease were detected amongst the study children. The efficacy of the vaccine for the prevention of all invasive disease after three doses was 95% (PRP-T vaccinees 1, controls 19 [95% CI 67-100]), for the prevention of Hib pneumonia after two or three doses, 100% (vaccinees 0, controls 10 [55-100]), and for the prevention of radiologically defined pneumonia at any time after enrollment, 21.1% (PRP-T vaccinees 198, controls 251 [4.6-34.9]).

INTERPRETATION

PRP-T conjugate Hib vaccine prevented most cases of meningitis and pneumonia due to Hib in Gambian infants. The reduction in the overall incidence of radiologically defined pneumonia in PRP-T vaccinees suggests that about 20% of episodes of pneumonia in young Gambian children are due to Hib. The introduction of Hib vaccines into developing countries should substantially reduce childhood mortality due to pneumonia and meningitis.

Muscarinic analgesics with potent and selective effects on the gastrointestinal tract: potential application for the treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a pathopysiolocal condition characterized by abnormal bowel habits that are frequently accompanied by abdominal pain. Current therapy based on reducing high-amplitude GI contractions with nonselective muscarinic antagonists is limited in efficacy due to typical muscarinic side effects and provides no pain relief. We have previously found potent antinociceptive agents acting through muscarinic receptors. In the present work, new 1,2,5-thiadiazole-based structures with muscarinic activity have been evaluated both for activity as analgesics in the mouse withing assay and for activity in normalizing spontaneous cluster contractions in ferret jejunum as a model of IBS in humans. (5R,6R)-exo-6-[4-[(4,4,4-Trifluorobutyl)thio]-1,2,5-thiadiazol+ ++-3-yl] -1-azabicyclo[3.2.1]octane (35, LY316108/NNC11-2192) was found to offer an exceptional profile combining analgesic potency in mouse writhing (ED50 = 0.1 mg/kg) along with potency for normalization of GI motility (ED50 = 0.17 mg/kg). This combination of GI and analgesic potency suggests 35 as an excellent candidate for evaluation as a potential treatment of IBS.

Persistence of antibodies to meningococcal IgA1 protease versus decay of antibodies to group A polysaccharide and Opc protein

Sera were taken over a 5 year period from Gambian children vaccinated in 1983, when aged 1-4 years, with A + C meningococcal capsular polysaccharide, ELISA tests were devised to determine the concentrations of immunoglobulin A, G and M reacting with A polysaccharide and of IgG reacting with Opc protein, IgA1 protease and an internal 104 mer peptide derived from IgA1 protease. Vaccination resulted in a brief rise of antibodies to A polysaccharide followed by decline to pre-immunization levels. IgM levels were very high even before vaccination. Antibodies to Opc protein stimulated by natural exposure also declined over the 5 year period. In contrast, antibodies stimulated by natural exposure to IgA1 protease or to the internal peptide remained constant or increased (final geometric mean level of 47 micrograms IgG ml-1). We speculate that healthy carriage of Neisseria meningitidis or Haemophilus influenzae is responsible for this increase in IgG concentration.

The effect of a monoclonal antibody to tumor necrosis factor on survival from childhood cerebral malaria

Tumor necrosis factor (TNF) is thought to play a key role in the pathogenesis of cerebral malaria. A double-blind, placebo-controlled trial of an anti-TNF monoclonal antibody (B-C7) comprised 610 Gambian children with cerebral malaria, with mortality and residual neurologic sequelae as primary study end points. Sixty (19.9%) of 302 children who received B-C7 died compared with 64 (20.8%) of 308 children who received placebo (adjusted odds ratio [OR], 0.90; 95% confidence interval [CI], 0.57-1.42). Residual neurologic sequelae were detected in 15 (6.8%) of 221 survivors from the B-C7 group and in 5 (2.2%) of 225 survivors of the placebo group (adjusted OR, 3.35; 95% CI, 1.08-10.4). The monoclonal antibody used in this study did not improve survival in cerebral malaria and was associated with a significant increase in neurologic sequelae. A possible explanation of the latter observation is that the antibody acts to retain TNF within the circulation and thereby prolongs its effects on vascular endothelium.

A trial of artemether or quinine in children with cerebral malaria

BACKGROUND

Cerebral malaria has a mortality rate of 10 to 30 percent despite treatment with parenteral quinine, a situation that may worsen with the spread of quinine resistance. Artemether is a new antimalarial agent that clears parasites from the circulation more rapidly than quinine, but its effect on mortality is unclear.

METHODS

We conducted a randomized, unblinded comparison of intramuscular artemether and intramuscular quinine in 576 Gambian children with cerebral malaria. The primary end points of the study were mortality and residual neurologic sequelae.

RESULTS

Fifty-nine of the 288 children treated with artemether died in the hospital (20.5 percent), as compared with 62 of the 288 treated with quinine (21.5 percent). Among the 418 children analyzed at approximately five months for neurologic disease, residual neurologic sequelae were detected in 7 of 209 survivors treated with artemether (3.3 percent) and 11 of 209 survivors treated with quinine (5.3 percent, P = 0.5). After adjustment for potential confounders, the odds ratio for death was 0.84 (95 percent confidence interval, 0.53 to 1.32) in the artemether group, and for residual neurologic sequelae, 0.51 (95 percent confidence interval, 0.17 to 1.47). There were fewer local reactions at the injection site with artemether than with quinine (0.7 percent vs. 5.9 percent, P = 0.001).

CONCLUSIONS

Artemether is as effective as quinine in the treatment of cerebral malaria in children.

Geographical perspectives on bednet use and malaria transmission in The Gambia, West Africa

Insecticide-impregnated bednets are now widely accepted as an important tool in reducing malaria-related deaths in children in Africa. Defining the circumstances in which net treatment programmes are likely to be effective is essential to a rational development of this control strategy. In The Gambia a National Impregnated Bednet Programme was introduced into the primary health care system in 1992. Prior to its introduction baseline epidemiological and entomological studies were conducted throughout the country. These studies showed that in areas where mosquito biting nuisance was high, people protected themselves with bednets and that where mosquito densities (and therefore bednet usage) was low malaria prevalence rates were relatively high. Since the national programme is designed to assist only those people who already own a bednet (by providing the insecticide) an understanding of the factors which determine bednet ownership is needed to help evaluate the programme's effectiveness and provide guidelines for increasing bednet usage. Village scale bednet usage rates and malaria prevalence rates obtained from the baseline survey were correlated with certain geographical variables: dominant ethnic group, area, habitat, distance from the River Gambia and distance from the 'bluffline' (the interface between the sandstone soils and alluvial soils which border the river system). In a multiple regression analysis, bednet usage was independently associated with area (P < 0.001), ethnic group (P = 0.010), habitat (P = 0.006) and distance from the river (P = 0.013). A negative association of bednet usage with malaria prevalence persisted after allowing for the other variables. Malaria prevalence was not independently associated with area, ethnic group, habitat or distance from the river. Our analysis showed that the impregnated bednet programme is likely to be most effective in villages which are sited near to or on the alluvial soils in the middle and lower river zones. These villages, which were originally settled for easy access to the river (for transport) and its swampy margins (for rice production) are within the flight distance of mosquitoes that have their breeding sites on the poorly drained alluvial soils. Variation in malaria prevalence rates (after bednet usage has been taken into account) may be related to factors such as poverty and access to health care, and/or to localized differences in the ecology of The Gambia, which determine the duration and intensity of transmission. If the National Bednet Programme is to be effective throughout The Gambia it is vital to develop promotional activities which will encourage bednet usage in areas where nuisance biting by mosquitoes is low.

Neural integration of jejunal motility and ion transport in nematode-infected ferrets

Jejunal motility measured manometrically and coupled fluctuations in electrogenic ion transport measured as transmural potential differences (PD) were simultaneously studied in ferrets infected with enteric stages of the parasitic nematode, Trichinella spiralis. Vagotomy in uninfected ferrets abolished jejunal motility clusters and associated PD oscillations. Conversely, in infected ferrets on days 8-12 postinfection (PI), vagotomy did not abolish jejunal motility and PD. Calculated motility indexes (MI) indicated that postvagotomy MI decreased to 12% of prevagotomy MI in uninfected ferrets, whereas, in T.spiralis-infected ferrets, postvagotomy MI declined only to 48% of prevagotomy MI. Atropine abolished all vagotomy-resistant residual jejunal motility clusters and PD oscillations in T. spiralis-infected ferrets. Decreased intestinal content of substance P (27% of control) and vasoactive intestinal peptide (41% of control) and increased myeloperoxidase activity (262% of control) were detected in T. spiralis-infected ferrets. Our results suggest that integrated neural control of muscular and epithelial effectors in the small bowel is altered by nematode-induced inflammation.