Identification of four members of the Anopheles funestus (Diptera: Culicidae) group and their role in Plasmodium falciparum transmission in Bagamoyo coastal Tanzania.

The role of Anopheles funestus group in malaria transmission was investigated in Bagamoyo coastal Tanzania, in the process of characterizing the area as a malaria vaccine testing site. Mosquitoes were sampled inside houses and multiplex PCR was used to identify 649 specimens. The following species were found: A. funestus s.s. (84.3%), A. leesoni (13.6%), A. rivulorum (1.5%) and A. parensis (0.6%). Multiplex PCR of 147 blood-fed specimens showed that over half (57.1%) of the identifiable blood meals were taken from human hosts, and human blood index in A. funestus and A. leesoni was 55% and 82% respectively. Plasmodium falciparum infection rate determined by nested PCR was 11% in A. funestus s.s. Although the abundance was low, 26 specimens of A. leesoni, two of A. rivolurum and one of A. parensis were found positive for P. falciparum. The presence of four A. funestus species in Tanzania emphasizes the relevance to define precisely their spatial and temporal distribution, specific behaviour, ecology and exact role in malaria transmission.

Sulfadoxine-pyrimethamine monotherapy in Tanzanian children gives rapid parasite clearance but slow fever clearance that is improved by chloroquine in combination therapy.

Following widespread chloroquine (CQ) resistance, sulfadoxine plus pyrimethamine (SP) is now the first line antimalarial drug in a number of African countries including Tanzania. Unlike CQ, SP has no antipyretic effects, a feature that might delay fever clearance, and by acting on late stage parasites, SP could theoretical be slow in parasite clearance. We therefore assessed the antipyretic effects of CQ in therapeutic combination with SP, and the speed of parasite clearance by SP in an open-labelled, randomized trial of CQ alone (n=39), SP alone (n=39), SP plus CQ (n=37) and SP plus paracetamol (PCM) (n=38) in children with uncomplicated malaria. Over 72 h, there were eight (20.5%) treatment failures in the CQ group but none in the other groups. Although not significant (P > 0.1), irrespective of resistance CQ alone had a shorter median survival time to fever clearance than SP alone (54 vs. 60 h). SP plus CQ had a highly significantly shorter median survival time to fever clearance than SP alone (48 vs. 60 h) (P < 0.001). Although borderline (P=0.038), the median survival time to parasite clearance was significantly longer in SP plus PCM (72 h) than SP alone (48 h). Irrespective of resistance, CQ alone had a median survival time to parasite clearance equal to that of SP alone (48 h). Parasite clearance by SP was rapid and at the end of 72 h, most (77.3%, 95% confidence interval: 69.6, 85.0) of the children on SP (as a group) had become aparasitaemic. The findings rule out concerns on possible delayed parasitological and clinical responses to SP that could result from its action on late stage parasites. Despite its diminishing antimalarial activity, CQ has beneficial in vivo antipyretic effects in therapeutic combination with SP.

Perception of chloroquine efficacy and alternative treatments for uncomplicated malaria in children in a holoendemic area of Tanzania: implications for the change of treatment policy.

Prior to policy change from chloroquine (CQ) to sulphadoxine/pyrimethamine (S/P; Fansidar) we assessed the perception of CQ efficacy and the alternative treatment options for malaria in children among parents/guardians (N=527) of under-fives attending first level health facilities on account of fever. It was hypothesized that the long experience with CQ and its antipyretic effect (lacking in S/P) might impede acceptance of S/P for wider use as first-line drug. Malarial fevers in children were most commonly treated with CQ (92.8%), followed by quinine (60.7%) and S/P (28.7%). A 63.2% knew the reasons for non-response to antimalarial treatment, and only 50% were aware that CQ could fail to treat malaria, and 57.1% knew alternative treatment options, namely quinine (52.2%) and S/P (20.5%). Generally, decreased efficacy of CQ had been noticed, and quinine was prescribed for both suspected and proven CQ failures in first level health facilities and the district hospital. S/P was judged to be more effective than quinine, but too strong for children, and was the least known drug in the study area. All formulations of S/P cost more per dose for a child and an adult than CQ. The implications of these findings on the change of malaria treatment policy are discussed.

Malaria diagnosis and treatment under the strategy of the integrated management of childhood illness (IMCI): relevance of laboratory support from the rapid immunochromatographic tests of ICT Malaria P.f/P.v and OptiMal.

The algorithm developed for the integrated management of childhood illness (IMCI) provides guidelines for the treatment of paediatric malaria. In areas where malaria is endemic, for example, the IMCI strategy may indicate that children who present with fever, a recent history of fever and/or pallor should receive antimalarial chemotherapy. In many holo-endemic areas, it is unclear whether laboratory tests to confirm that such signs are the result of malaria would be very relevant or useful. Children from a holo-endemic region of Tanzania were therefore checked for malarial parasites by microscopy and by using two rapid immunochromatographic tests (RIT) for the diagnosis of malaria (ICT Malaria P.f/P.v and OptiMal. At the time they were tested, each of these children had been targeted for antimalarial treatment (following the IMCI strategy) because of fever and/or pallor. Only 70% of the 395 children classified to receive antimalarial drugs by the IMCI algorithm had malarial parasitaemias (68.4% had Plasmodium falciparum trophozoites, 1.3% only P. falciparum gametocytes, 0.3% P. ovale and 0.3% P. malariae). As indicators of P. falciparum trophozoites in the peripheral blood, fever had a sensitivity of 93.0% and a specificity of 15.5% whereas pallor had a sensitivity of 72.2% and a specificity of 50.8%. The RIT both had very high corresponding sensitivities (of 100.0% for the ICT and 94.0% for OptiMal) but the specificity of the ICT (74.0%) was significantly lower than that for OptiMal (100.0%). Fever and pallor were significantly associated with the P. falciparum asexual parasitaemias that equalled or exceeded the threshold intensity (2000/microl) that has the optimum sensitivity and specificity for the definition of a malarial episode. Diagnostic likelihood ratios (DLR) showed that a positive result in the OptiMal test (DLR = infinity) was a better indication of malaria than a positive result in the ICT (DLR = 3.85). In fact, OptiMal had diagnostic reliability (0.93) which approached that of an ideal test and, since it only detects live parasites, OptiMal is superior to the ICT in monitoring therapeutic responses. Although the RIT may seem attractive for use in primary health facilities because relatively inexperienced staff can perform them, the high cost of these tests is prohibitive. In holo-endemic areas, use of RIT or microscopical examination of bloodsmears may only be relevant when malaria needs to be excluded as a cause of illness (e.g. prior to treatment with toxic or expensive drugs, or during malaria epidemics). Wherever the effective drugs for the first-line treatment of malaria are cheap (e.g. chloroquine and Fansidar), treatment based on clinical diagnosis alone should prove cost-saving in health facilities without microscopy.

Urinary schistosomiasis in schoolchildren in Dar-es-Salaam, Tanzania, and the factors influencing its transmission.

The prevalence of urinary schistosomiasis among the schoolchildren living in Kigogo administrative ward of the Kinondoni district of Dar-es-Salaam city, Tanzania, and the factors influencing the transmission of the causative agent, Schistosoma haematobium, were investigated in a cross-sectional study. The estimate of overall prevalence, based on microscopical examination of a single urine sample/subject, was 47.6%. Compared with the girls, the boys were more likely to be excreting schistosome eggs (54.6% v. 40.8%; P = 0.004) and had, in general, higher intensities of infection (54 v. 38 eggs/10 ml urine; P = 0.001). The children aged 10-14 years had higher prevalences and intensities of infection than those in the younger or older age-group studied. The sensitivity of micro-haematuria as an indicator of infection (compared with the microscopical examination of single urine samples) was 84.3% overall, reaching 92% among the children excreting > or = 50 eggs/10 ml urine. The corresponding positive and negative predictive values were 77% and 84%, respectively. The sensitivity, specificity and positive and negative predictive values of the history of haematuria as an indirect screening technique for S. haematobium were 60.4%, 72.7%, 67% and 67%, respectively. Recreational activities such as bathing, swimming and playing in the water were the most frequent activities attracting children to water bodies and carried the highest risks of infection with S. haematobium. Knowledge about the disease, especially on the symptoms and mode of transmission, was generally good but the methods of prevention were inadequately known. Chemotherapy to control urinary schistosomiasis in schoolchildren is recommended; infected children may be identified on the basis of haematuria, detected using questionnaires or reagent strips. Additional health education, to heighten awareness of the disease and its prevention, would also be beneficial.

Mothers' perceptions and knowledge on childhood malaria in the holendemic Kibaha district, Tanzania: implications for malaria control and the IMCI strategy.

Prior to an intervention on improving the quality of malaria case management, we assessed mothers' abilities to recognize nonsevere and severe/complicated malaria in children when a child has fever with other physiological and behavioural symptoms associated with malaria. Malaria was mentioned as the commonest febrile illness (94. 1%), convulsions the least (11.4%). Fever and enteric symptoms featured as the most important symptoms of childhood malaria at frequencies of 93.5% and 73.8%, respectively. The need for laboratory diagnosis was very high (98.3%), the reason being to get accurate diagnosis and treatment (89.4%). Poor outcome of treatment was ascribed to incorrect diagnosis and prescription, noncompliance at home and ineffective drugs (62.1%). Most mothers (86.6%) would take antipyretic measures first when a child has fever, and subsequently the majority (92.9%) would seek care at a modern health facility. About 50% of the mothers would give traditional treatments for childhood convulsions and wait till fits cease before the next action. A high proportion of the mothers (75%) held the belief that an injection in a child with high fever would precipitate convulsions or death. The implications of these findings for chemotherapeutic malaria control in holoendemic areas within the context of the Integrated Management of Childhood Illnesses (IMCI) strategy are discussed.

Current clinical efficacy of chloroquine for the treatment of Plasmodium falciparum infections in urban Dar es Salaam, United Republic of Tanzania.

Reported is the use of a 14-day WHO protocol, which takes into account the clinical, parasitological and haematological responses to antimalarial drugs, to determine the efficacy of chloroquine in the treatment of uncomplicated malaria in young children (n = 200) in urban Dar es Salaam. Chloroquine failure was found in 43% of the children. Of these, 12.5% were considered to be early treatment failures and were given a single dose of sulfadoxine-pyrimethamine. Fever subsided in all children treated with sulfadoxine-pyrimethamine and there were no parasitological failures. In addition, children treated with sulfadoxine-pyrimethamine because of early treatment failure with chloroquine had better haematological recovery than the chloroquine-sensitive group. It is concluded that chloroquine can no longer be considered an effective therapy for P. falciparum malaria in young children in Dar es Salaam.

The role of four anopheline species (Diptera: Culicidae) in malaria transmission in coastal Tanzania.

Malaria is holoendemic in coastal Tanzania with Anopheles funestus and members of the A. gambiae complex being mainly responsible for transmission. Over a 4 months' sampling period 2222 anopheline mosquitoes were collected using light-traps and indoor resting catches, of which 58.6% were A. gambiae, 7.6% A. arabiensis, 6.9% A. merus and 26.9% A. funestus. Plasmodium falciparum circumsporozoite antigen (CSA) rates were: A. funestus 6.05% (n = 479), A. gambiae 8.4% (n = 1042), A. arabiensis 7.3% (n = 136) and A. merus 9.8% (n = 122). The P. malariae CSA rate for all anophelines was 0.07% (n = 1862). Estimated sporozoite densities were less than 2000 for at least 50% of all the positive mosquitoes. Along the coast the abundance of A. merus (41.3%) and A. gambiae (46.1%) was similar, and their CSA rates were comparable (11.6% and 12.5%, respectively) and higher than those for A. arabiensis (7.7%) and A. funestus (4.6%). These results indicate that A. merus plays an unexpectedly important role in malaria transmission in coastal Tanzania.

Social and cultural factors affecting rates of regular retreatment of mosquito nets with insecticide in Bagamoyo District, Tanzania.

Insecticide-treated mosquito nets have an impact on mortality and morbidity in young children under controlled conditions. When integrated into larger control programs, there is the danger that rates of regular retreatment of the nets with insecticide will drop, greatly limiting their effectiveness as a public health intervention. In Bagamoyo District, Tanzania, rates of retreatment dropped significantly when payment for the insecticide was introduced. A series of neighbourhood (hamlet) meetings were held in all study villages to discuss people's concerns about the insecticide and ways to increase rates of retreatment. Although changes were made in the procedure for retreatment, rates of retreatment remained lower than expected and showed marked variation within as well as between villages. We then conducted unstructured key informant interviews as well as informal discussions in a village with strong variation between different sectors of the villages in rates of retreatment. While logistical problems were most frequently cited as reasons not to bring nets for retreatment, political and social divisions within the community provided a better explanation. This is borne out by the low response to rearrangements in logistics which made retreating the nets significantly easier for households, and the higher response when changes were made in the channels of communication as well as the logistic features. It is clearly more difficult for villagers to appreciate the benefits of the insecticide than those of the nets. Great emphasis needs to be placed on the insecticide and its beneficial effects from the outset for any large-scale programme to be sustainable.

Community based studies on childhood mortality in a malaria holoendemic area on the Tanzanian coast.

Demographic surveillance of children under 5 years of age was undertaken over a 2 year period in a rural area of coastal Tanzania where holoendemic malaria conditions exist. The mean annual entomological innoculation rate (EIR) during the period under study was 234 infective bites per person. There were 192 deaths in children and 1130 live births during the 2 years. Of these, 148 were infant deaths giving an infant mortality rate of 131/1000 live births (95% CI 101, 154). There were 44 deaths in children 1-4 years of age and the overall child mortality rate was 10/1000 (95% CI 6.1, 14.3). Using verbal autopsy questionnaires, 56% of the deaths under 4 years were tentatively attributed to malaria.

Treatment practices for degedege, a locally recognized febrile illness, and implications for strategies to decrease mortality from severe malaria in Bagamoyo District, Tanzania.

Malaria remains one of the chief causes of mortality among young children in sub-Saharan Africa. Verbal autopsies for cases of childhood mortality in Bagamoyo District, Tanzania demonstrated that degedege, a locally defined illness of children characterized by fever and convulsions, is frequently treated by traditional healers. To investigate this further, an ethnographic study was carried out in one village that included in-depth interviews with 14 traditional healers and 3 focus groups with parents. Parents and traditional healers were unanimous in their conviction that degedege requires traditional treatments, at least initially, and that these treatments are effective. While traditional healers do refer cases that are not improving to the District Hospital, this frequently occurs late in the course of the illness, after one or more stages of traditional treatments. The prognosis will thus be poor for those children who are suffering from severe malaria. Consideration should be given to enlisting the support of traditional healers in efforts to improve treatment for severe malaria, including teaching them how to distinguish febrile convulsions from cases of severe malaria.

The polymerase chain reaction method as a tool for identifying members of the Anopheles gambiae complex (Diptera:Culicidae) in northeastern Tanzania.

Polymerase chain reaction (PCR) primers developed at the Centers for Disease Control in Atlanta for the identification of members of the Anopheles (Cellia) gambiae Giles complex were tested on material collected in the Bagamoyo and Muheza districts of northeastern Tanzania. Part of the sample from Bagamoyo was chromosomally identified and correlated with the PCR identifications. This sample contained 170 Anopheles arabiensis, 328 An. gambiae, and 58 Anopheles merus, of which 121, 237, and 54 specimens, respectively, were identified with both PCR and chromosomes. Three specimens identified chromosomally as An. merus gave only the PCR fragment characteristic for Anopheles quadriannulatus, but on retesting gave the correct result. The Muheza sample consisted of 771 An. arabiensis, 852 An. gambiae, 43 An. merus, and 4 specimens producing the fragment characteristic for An. quadriannulatus. Because An. quadriannulatus has never been recorded from mainland Tanzania and due to the high number of specimens that produced no result (193), it is probable that DNA degradation led to misidentification of An. merus specimens as An. quadriannulatus. The overall probability of correct identification by PCR was 99.685% at first testing, which compares favorably with other genetic methods currently in use.

Prevalence of intestinal parasites in adult patients with enteropathic AIDS in north-eastern Tanzania.

A six month study was conducted in north-eastern Tanzania to determine the prevalence of pathogenic intestinal parasites among adult patients with enteropathic AIDS. A total of 352 patients were recruited of whom 158 (45%) had chronic diarrhoea. Of the 352 patients, 123 (35%) had intestinal parasites. Of the 123, 77 (62.6%) patients had chronic diarrhoea. The types of parasites detected were Cryptosporidium, Isospora belli, Strongyloides stercoralis, Schistosoma mansoni, Trichuris, trichiura, Ascaris lumbricoides, hookworm and Entamoeba histolytica. The prevalence of intestinal parasites was significantly higher in patients with chronic diarrhoea than in those without (P < 0.05). Cryptosporidium and Isospora belli were only detected in patients with chronic diarrhoea and were thus the most likely cause of the diarrhoea. This study has established that coccidian parasites are the most important gut opportunistic infections in Tanzanian patients with enteropathic AIDS. The fact that a high proportion of patients with chronic diarrhoea (51.3%) had no identifiable parasitic agents, suggests that other infectious agents or alternative mechanisms other than infections are responsible for the diarrhoea.

PIP: A 6-month study was conducted in northeastern Tanzania to assess the prevalence of pathogenic intestinal parasites among adult patients with enteropathic AIDS. Of the 352 patients recruited, 158 had chronic diarrhea and 123 had intestinal parasites. 77 of the 123 patients with intestinal parasites had chronic diarrhea. Cryptosporidium, Isospora belli, Strongyloides stercoralis, Schistosoma mansoni, Trichuris trichiura, Ascaris lumbricoides, hookworm, and Entamoeba histolytica were detected. The prevalence of intestinal parasites was significantly higher in patients with chronic diarrhea than in those without. Cryptosporidium and Isospora belli were only detected in patients with chronic diarrhea and were therefore the most likely cause of the diarrhea. Coccidian parasites have thus been identified as the most important gut opportunistic infections in Tanzanian patients with enteropathic AIDS. However, that 51.3% of patients with chronic diarrhea had no identifiable parasitic agents suggests that other infectious agents or alternative mechanisms are responsible for the condition.

Changes in weight gain and anaemia attributable to malaria in Tanzanian children living under holoendemic conditions.

We investigated the effect of Plasmodium falciparum malaria on weight gain and haematocrit in Tanzanian children aged 6-40 months following a malaria control scheme which combined insecticide-impregnated bed nets with chloroquine chemotherapy on demand. Data from 7 villages (3 intervention and 4 control) were collected before, and one year after, the implementation of the programme. Initially, 82% of the children were parasitaemic, 78% were anaemic (i.e., packed cell volume < 33%) and 38% were underweight (i.e., 2 standard deviations below their weight-for-age Z score). One year after implementation of the programme, children not protected by the bed nets grew 286 g less (95% confidence interval [CI] 171-402 g) in a 5 months period and were twice as likely to be anaemic (95% CI 1.4-2.7) than were children not using impregnated bed nets. Our results indicated that, under holoendemic conditions, P. falciparum infection has a marked effect on both weight gain and anaemia.

Local terminology for febrile illnesses in Bagamoyo District, Tanzania and its impact on the design of a community-based malaria control programme.

This paper reviews results of several ethnographic studies that have examined the issue of local terminology for malaria in Africa, then presents findings from an on-going study in Bagamoyo District, Tanzania. The study used a mixture of qualitative and quantitative interview methods to examine local perceptions of malaria and malaria treatment practices. Although the local term homa ya malaria or malaria fever appeared on the surface to correspond closely with the biomedical term malaria, significant and often subtle differences were found between the two terms. Of perhaps greatest importance, common consequences of malaria in endemic areas such as cerebral malaria in young children, severe anaemia and malaria in pregnancy were not connected with homa ya malaria by many people. A set of guidelines are described that were used to determine how best to promote acceptance and use of insecticide-impregnated mosquito nets, given these results. It is demonstrated that the position of the term used to denote malaria in the local taxonomy of febrile illnesses has important implications for the design of health education interventions.

Changes in malaria associated morbidity in children using insecticide treated mosquito nets in the Bagamoyo district of coastal Tanzania.

A community based malaria control intervention using insecticide treated mosquito nets (IMN) has been implemented and tested in 13 villages of the Yombo Division, Bagamoyo District in the Coastal Region, Tanzania, an area holoendemic for P. falciparum malaria. Following extensive sociological research into local perceptions of malaria, the programme was implemented. It wa decided by consensus that village mosquito net committees would be the appropriate local level implementors. These were formed and provided with IMN's which were sold to villagers at subsidised cost. The income was invested for use by the committees for sustaining the activity. Use patterns were determined and high coverages were obtained among the community, particularly after promotions e.g. plays, school meetings etc. Malaria morbidity was measured among children 6-40 months of age in 7 index villages prior to the intervention in 1992 and in a comparison study between 3 villages using nets and 4 villages not using nets in 1993. Examination of the 7 cohorts of children was done from June to October each year covering the period of most severe transmission. The children using nets showed marked improvement in several malariometric indices. Following an initial clearance of parasitaemia with sulphadoxine/pyrimethamine, when compared with unprotected children, those with nets were slower to become re-infected (Relative Risk 0.45), had lower parasitaemias and showed marked improvement in anaemia (RR 0.47). Use of IMN's produced a 54% reduction in the prevalence of anaemia among young children. Attempts are being made to ensure that the programme is locally sustained.