Pemba Island Research Articles

Unexpectedly low prevalence of Helicobacter pylori infection among pregnant women on Pemba Island, Zanzibar

Helicobacter pylori is strongly associated with peptic ulcer and gastric cancer and may be the most common human bacterial infection. The epidemiology of H. pylori has been poorly studied in Africa, where its relevance to disease has not been fully appreciated. Following a cross-sectional study design, H. pylori infection was measured by (13)C-urea breath test among 857 pregnant women attending antenatal care clinics. Location, water use practices, anthropometry, and social and demographic variables were assessed as covariates. The prevalence of H. pylori infection was 17.5%. Multiple logistic regression showed that H. pylori was positively associated with location of enrollment clinic along the main road leading from the southern seaport (odds ratio (OR)=2.5), presence of costlier household lighting in the home (OR=1.6) and height (10 cm) (OR=1.5). The prevalence of H. pylori infection was unexpectedly low for a developing country population, where prevalence is typically very high. Higher prevalence along the road from the southern seaport suggests that infection was imported from the mainland. The reason for very low prevalence should be investigated further because the discovery of bacterial or dietary factors that limit infection in this population could have useful public health applications.

A review of East and Central African species of Letheobia Cope, revived from the synonymy of Rhinotyphlops Fitzinger, with descriptions of five new species (Serpentes: Typhlopidae)

The genus Letheobia Cope 1869 is revived for the “worm-like blind-snakes” which were assigned to the genus Rhinotyphlops Fitzinger 1843 by Roux-Estève in 1974 (her Groups IV to VII). Letheobia pallida is restricted to Zanzibar, and the specimens from Pemba Island, the East African coast, southern Sudan and southwestern Ethiopia are described as four new species. Three species included by Roux-Estève (1974) in the polyphyletic genus Typhlops Oppel, T. uluguruensis Barbour & Loveridge (Group II), T. obtusus Peters and T. decorosus Buchholz & Peters (Group V) are considered basal forms in the genus Letheobia and a related species, L. jubana sp. nov., is described from southern Somalia.

Nuttingins A−F and Malonganenones D−H, Tetraprenylated Alkaloids from the Tanzanian Gorgonian Euplexaura nuttingi

Six new tetraprenylated purine alkaloids, designated nuttingins A-F (1-6), were isolated together with three known malonganenones, A-C (12-14), and five new closely related malonganenones, D-H (7-11), from the gorgonian Euplexaura nuttingi collected in Pemba Island, Tanzania. The structures of the compounds were elucidated by interpretation of 1D and 2D NMR data including 15N chemical shifts obtained from 1H-15N HMBC spectra. Nuttingins A-E (1-5) and malonganenones D-G (7-10) displayed inhibitory activity against both K562 and UT7 tumor cell lines, compounds 3-5 being the most active ones, approximately 3-fold more potent than the others. Compounds 1-5 and 7-11 also induce apoptosis in transformed mammalian cells at a concentration of 1.25 microg/mL.

Geophagia is not associated with Trichuris or hookworm transmission in Zanzibar, Tanzania

Geophagia may be harmful as a method for the transmission of geohelminths. In this study, we pose two questions in a representative sample of 970 pregnant women from Pemba Island, Zanzibar, Tanzania. Can consumed earth be a vector for geohelminth infection? And do geophagists have differential parasitic infection? The parasitological content of 59 non-food substance samples was analysed. Cross-sectional data regarding pica behaviour were collected through interviews conducted by local researchers. Ascaris, Trichuris and hookworm status was ascertained through Kato-Katz smears. The prevalence of geophagia at baseline was 5.6% and the overall prevalence of Ascaris, Trichuris and hookworm infection was 5.6%, 33.2% and 32.9%, respectively. No consumed soil samples contained infectious parasitic stages, and only one of the consumed pica substances (charcoal) contained parasites of potential risk to human health. In bivariate analyses, neither the prevalence nor the intensity of infection with Ascaris, Trichuris or hookworm differed significantly by geophagia status. Furthermore, in multivariate models, geophagia was not a significant predictor of helminth infection status. We conclude that geophagia is not a source of Trichuris or hookworm infection among pregnant women in Pemba (insufficient power to evaluate the effect of Ascaris), which is in contrast to existing findings of helminth infection and geophagia.

Tropical African Platycnemis damselflies (Odonata: Platycnemididae) and the biogeographical significance of a new species from Pemba Island, Tanzania

The damselfly, Platycnemis pembipes sp. nov., is described from Pemba Island (Ngezi Forest, Tanzania) and its affinities with Guineo‐Congolian and Malagasy congeners are examined. For this purpose the identity and distribution of Afrotropical Platycnemis is reviewed, especially the taxonomically confused continental species. The Pemba species is nearly identical to some species of the Malagasy radiation of Platycnemis, but distant from the Guineo‐Congolian species that have tropical Asian affinities. It is argued that the species is a long‐distance wind‐borne arrival from Madagascar, which survived due to favourable climatic conditions on Pemba. Habitats on the mainland, only 50 km further, are or have been drier and therefore seem unsuitable. The new species, living proof of a remarkable colonisation event, is under immediate threat, confined to a single stream in an imperilled forest, over 1000 km from its nearest relatives. The holotype of the enigmatic P. mauriciana, not recorded on Mauritius after its description, cannot originate from the island as it pertains to the European P. latipes. Five species recalling the Asian genus Copera are known in the male sex from central and western Africa; all were confused to some degree with P. congolensis and a key is given. The lectotype of P. congolensis is designated and its identity is clarified. Platycnemis flavipes and P. xanthopus are junior synonyms of P. nyansana. Discovery of the P. rufipes female showed that P. escherichi, known only from the female holotype, is a junior synonym of it. The generic classification of Platycnemis and Copera is not resolved, but data and hypotheses that should aid future analysis are provided.

A COMPARISON OF METHODS FOR DETECTING THE EGGS OF ASCARIS, TRICHURIS, AND HOOKWORM IN INFANT STOOL, AND THE EPIDEMIOLOGY OF INFECTION IN ZANZIBARI INFANTS

This study compared five methods for detecting the eggs of the human parasitic geohelminths Ascaris, Trichuris, and hookworm in infant stool, and describes the epidemiology of infection in infants from a parasite-endemic area. A total of 424 infants 5-11 months old were enrolled from three villages on Pemba Island, Zanzibar. Methods used included the Kato-Katz technique, formol ethyl acetate sedimentation, modified formol ethyl acetate sedimentation, modified Wisconsin floatation, and simple gravity sedimentation. Of methods used alone, Wisconsin floatation and simple gravity sedimentation each provided the highest sensitivity for detecting eggs of these three geohelminths (89.6%). Of methods used in combination, the Kato-Katz technique/simple gravity sedimentation and Wisconsin floatation/simple gravity sedimentation each provided the highest sensitivity (99.0%). Prevalence of geohelminth infection was 26.5%. Between five and nine months of age the mean prevalence was 9.4%, while at 10 and 11 months of age the mean prevalence was 43.4%. Village prevalence varied from 3.6% to 43.8%. Infant geohelminth infection can occur at a high prevalence, and what method is best depends on research specifics.

Measurement of blood loss at childbirth and postpartum

Objective To accurately measure blood loss during childbirth in a developing country. Method The alkaline hematin technique was used to quantify blood lost during delivery and 24 h postpartum in 158 women in Pemba Island, Zanzibar. Result Women were found to lose less blood during childbirth and 24 h postpartum than previously reported. Compared with laboratory values, nurse–midwives approximated blood loss accurately (mean difference, i.e., mean underestimation by nurse–midwives, 4.90 mL); however, their imprecision was greater for higher laboratory values. Conclusion This study may prompt further investigation, as no comparable data exist for developing countries where maternal mortality is high and severe anemia prevalent.

Phylogenetic affinities of Comoroan and East African day geckos (genus Phelsuma): Multiple natural colonisations, introductions and island radiations

The day-geckos of the genus Phelsuma (Gray, 1825) are amongst the most prominent reptiles from the Malagasy region. The whole genus consists of about 42 species, most of them inhabiting exclusively Madagascar. It is generally accepted that Phelsuma originated in Madagascar, and that from there they dispersed to several other Indian Ocean islands. In fact, they can be found on essentially every Indian Ocean archipelago: the Comoros, the Mascarenes, the Seychelles, Aldabra and even the Andamans. Having colonised these archipelagos they often radiated, producing several sets of endemic species. One of the species, P. dubia, mostly distributed on the western Malagasy coast, can also be found on mainland Africa, in coastal Kenya and Tanzania and in the islands of Zanzibar and Pemba (Loveridge, 1942). The island of Pemba also contains an additional endemic species, P. parkeri (Loveridge, 1941). The Comoro islands, a set of four major volcanic islands located north-west of Madagascar, are inhabited by four endemic species (Fig. 1): P. v-nigra (with subspecies v-nigra, anjouanensis, comoraegrandensis and pasteuri), P. nigristriata, P. robertmertensi and P. comorensis. Additionally, P. dubia and P. laticauda, which are also found on Madagascar (and on the East African coast in the case of P. dubia), can be found on the Comoros (Glaw and Vences, 1994). This species abundance, as opposed to what happens for example in the Seychelles, inhabited by only two species of Phelsuma, is presumably due to the proximity of the

Knowledge and practice of help-seeking for treatment of mental disorders in Pemba Island, Zanzibar

The objective of this study was to describe how people explain mental disorders and its treatment in Pemba Island, Zanzibar. Eight hundred and twenty-one participants (users, carers, health professionals, traditional healers, community members and leaders) were interviewed as part of a cross-sectional survey. Most people viewed mental disorder as arising within their internal or supernatural world. Although they thought that they could be helped both by primary health care and alternative healing, the majority described going to the traditional healers when things went wrong. This provides evidence that there is considerable reliance on traditional care for the treatment of mental disorders. It is therefore important for the health services to be in dialogue with the traditional healers.

Maternal anemia and blood loss at childbirth and postpartum in Pemba Island, Zanzibar, Tanzania

Severe bleeding at childbirth or postpartum hemorrhage (PPH) is the leading cause of maternal death worldwide. Anemia is purported to contribute to PPH, however, the relationship between blood loss and maternal anemia has not been examined. A study of these relationships requires a reliable, valid technique to measure blood loss and a setting where maternal anemia is prevalent. The study objectives were to quantify blood loss at childbirth and 24-hours postpartum and to evaluate determinants of blood loss. This study was nested within a community-based trial evaluating treatments to prevent severe anemia. Participants from antenatal clinics provided prenatal blood draws and presented for childbirth at a government hospital. We quantified blood loss using the alkaline hematin method. Approximately 61% of women were anemic during pregnancy. Our blood loss estimates, median (5th- 95th percentiles) for delivery, postpartum and in total were 153 mL, (21 – 416), 112 mL (43 – 242), and 286 mL (97 – 579). Moderate to severely anemic women had greater blood loss, (91 mL), than non-anemic women (p < 0.01). These findings have implications for treatment strategies alleviating maternal anemia. Future research may extend the alkaline hematin technique to elucidate risk factors for blood loss in home deliveries and to evaluate methods for the reduction of blood loss and prevention of postpartum hemorrhage.

The Makran-Baluch-African Network in Zanzibar and East Africa during the XIXth Century

Throughout the western Indian Ocean during the XIXth Century there were not just one, but people from many regions, merchandise and slave routes. They were generally divided in two main monsoon directions: one from East Africa and the Red Sea to Arabia, to India and to South East Asia, and the other in the opposite direction; consequently, slaves were not only black Africans, but also Asians. 1 African slaves were imported in great numbers annually from East Africa to Oman, travelling on Arab dhows (sanbuq). Around the first half of the XIXth Century there was an extensive commerce of slaves from Ras Assir (“The Cape of Slaves”) and Pemba, and many African people were bought with cloth and dates on Zanzibar and Pemba Islands, enslaved, and transported to the Arabian Peninsula where they were mainly engaged in fishing pearls in the Persian/Arab Gulf. 2 Slaves also became lords of African “reigns”, as they were considered to be more loyal than anybody else within their clans and tribes. In this

Gastrointestinal nematode infection is associated with variation in innate immune responsiveness

Ex vivo monocyte cytokine responses (IL-1 β, TNF-α, IL-12p70, IL-10, TGF-β) to bacterial TLR2 and TLR4 ligands were quantified in 47 gastrointestinal (GI) nematode-exposed children in Pemba Island, Tanzania. Worminess (estimated by faecal egg counts (FEC)) had a positive relationship with pro-inflammatory TNF-α and IL-1β responsiveness to the TLR ligands. In particular, there was a strong significant relationship with TNF-α response to TLR4 ligand (LPS). There were no significant associations between regulatory responses (IL-10, TGF-β) and worminess. These results are consistent with the possibility that GI nematodes modulate innate responses and may indicate a potential mechanism for interactions between GI nematodiasis and important bystander pathogens.

Development of the egg hatch assay for detection of anthelminthic resistance in human hookworms

Evidence of development and rapid spread of anthelminthic resistance in veterinary nematodes raises concern that the increasingly frequent treatments used in chemotherapy-based programmes to control human soil-transmitted helminths may select resistant worms. The aim of this study was to adapt, refine, and evaluate the Egg Hatch Assay (EHA) test, which has been used for veterinary nematodes, for field testing of benzimidazole (BZ) susceptibility/resistance in human hookworms. A second objective was to use this EHA to assess whether a population of worms resistant to mebendazole (MBZ) has built up in a sub-population of frequently treated children in Pemba Island. Stools from 470 school children enrolled in the first (Standard 1) and in the fifth (Standard 5) class were examined at baseline and at 21 days after treatment with 500 mg MBZ or placebo tablets. Standard 1 children had never received any MBZ treatment whilst Standard 5 children had received a total of 13 rounds of treatment. The EHA, involving culture of purified eggs with increasing drug concentrations showed that, for thiabendazole (TBZ), the mean ED 50s (concentrations required to prevent 50% of the viable eggs from hatching) for all children at baseline were 0.079 μg/ml at 48 h and 0.120 μg/ml at 72 h ( P<0.001). For MBZ, the mean ED 50s for all children at baseline were 0.895 μg/ml at 48 h and 1.50 μg/ml at 72 h ( P<0.001). For TBZ and for MBZ the ED 50 from Standard 1 were similar to those from Standard 5 children both at 48 and at 72 h. At the follow-up for TBZ and for MBZ, there was no significant difference between the ED 50 from children who had received MBZ and children treated with placebo. In Pemba, TBZ ED 50 values of children non-exposed (Standard 1) and of children exposed (Standard 5) to MBZ treatment, and data from children treated with MBZ and placebo indicate that a drug-resistant worm population has not built up within treated individuals, and that periodic treatment has not yet selected for widespread BZ resistance, at least at the threshold detectable by the EHA in this study. However, ED 50 values for strains isolated from Mafia island, an area never exposed to BZ treatment were lower than for Pemba, suggesting lowered sensitivity of hookworm eggs recovered from Pembian children towards BZ.

Clinical predictors of malaria and other febrile illnesses in children under five on Pemba Island, Tanzania

Under the current guidelines of presumptive treatment of all children with reported fever, the risk of over-prescribing antimalarial drugs and missing other important causes of fever, like acute respiratory tract infection (ARI), is substantial. Clinical algorithms have been shown to be useful in diagnosing malaria, but often with differing results, due to regional variations. We set out to explore the clinical features associated with malaria compared with other febrile illnesses and specifically severe malaria with ARI in children under five in Pemba. Two hundred and seven children aged six months to five years presenting to a hospital clinic with fever were studied in Pemba. Clinical findings were related to the presence of malaria parasitaemia. Malaria accounted for 67.7% of the febrile episodes investigated. Five symptoms and signs, including pallor, drowsiness, splenomegaly, fever duration and no chest crackles, could accurately predict a case of malaria with a sensitivity of 91.3% and specificity of 53% and positive predictive value of 80.3%. Several clinical features were found to differentiate severe malaria from ARI. These results confirm that clinical algorithms can increase the diagnostic accuracy of malaria, although not sufficiently to replace microscopy, and by promoting the use of clinical skills other treatable causes of febrile illnesses may be identified. These findings could have implications in optimizing treatment and malaria control in children on Pemba.

Linking traditional treatments of maternal anaemia to iron supplement use: an ethnographic case study from Pemba Island, Zanzibar

Iron deficiency anaemia is the most common form of malnutrition in the world. Pregnant women are particularly at risk for anaemia. Insufficient attention has been paid to the reasons underlying the only moderate success of iron supplementation. In this article an additional factor that can affect the use of iron supplements is proposed: their relevance to 'traditional' or nonbiomedical treatments of anaemia. This paper represents what is to our knowledge the first ethnographic description of nonbiomedical treatments for maternal anaemia. The research was conducted over several months on Pemba, one of the islands of the Zanzibar archipelago. Data were collected using a variety of qualitative methods, including in-depth interviews, focus group discussions and participant observation. Informants included 25 mothers and 27 traditional and biomedical health care workers. The resulting ethnography elucidates Pembans' beliefs about the relationship of food, traditional medicine, spirits and biomedical medicine in relation to anaemia. In the analysis of the ethnography, both anthropology and public health perspectives are incorporated to suggest how the understanding of these beliefs is useful for increasing iron supplement use.

Low-Dose Daily Iron Supplementation for 12 Months Does Not Increase the Prevalence of Malarial Infection or Density of Parasites in Young Zanzibari Children

Conflicting evidence exists on the possible role of iron supplementation in the predisposition to malaria infection or the enhancement of its clinical severity. Where anemia prevalence is >40%, current guidelines are to provide low-dose daily iron to young children for up to 18 mo. Earlier studies used doses higher than the current guidelines, intermittent doses, or have supplemented for durations < or = 4 mo. We aimed to assess the effect of low-dose, long-term iron supplementation on malaria infection using a double-blind, placebo-controlled, randomized design, and to examine possible subgroup effects by season and child age. The study was conducted in Pemba Island, Zanzibar, where Plasmodium falciparum malaria has year-round high transmission. A community-based sample of 614 children 4-71 mo old was randomly allocated to 10 mg/d iron or placebo for 12 mo. Outcome measures were the prevalence and density of malaria infection, which was assessed by blood films at monthly intervals. At baseline, 94.4% were anemic (hemoglobin < 110 g/L), 48.1% were stunted (height-for-age Z-score less than -2) and >80% had malaria-positive blood films. No significant differences in malariometric indices were observed between children in the iron-supplemented and placebo groups. Parasite density was higher in certain months and in younger children, but iron supplementation was not associated with any malarial infection outcome in any season or age subgroup. We conclude that in this environment of high malaria transmission, daily oral low-dose supplementation of iron for 12 mo did not affect the prevalence of malaria infection or parasite density.

Molecular analysis of the beta-tubulin gene of human hookworms as a basis for possible benzimidazole resistance on Pemba Island.

Molecular analysis of the beta-tubulin gene of human hookworms as a basis for possible benzimidazole resistance on Pemba Island.

Microsatellites in the freshwater snail Bulinus globosus (Gastropoda: Planorbidae) from Zanzibar

AbstractSix microsatellite loci were isolated and characterized in Bulinus globosus, a freshwater snail with a wide distribution throughout sub‐Saharan Africa. Bulinus globosus is an intermediate host of Schistosoma haematobium, the causative agent of human urinary schistosomiasis. Microsatellites were tested using 32 snails from four populations collected from Pemba and Unguja islands of Zanzibar. The microsatellite loci displayed relatively low levels of variation, with between two and five alleles per locus. FST estimates indicate that gene flow is low, as has previously been suggested for other species of Bulinus.

Evaluation of the efficacy of pyrantel-oxantel for the treatment of soil-transmitted nematode infections

A randomized controlled trial comparing the efficacy of pyrantel-oxantel (10 mg/kg) with mebendazole (500 mg) was performed on 1329 schoolchildren aged 6–9 years on Pemba Island in September–October 2000 to evaluate alternative single-dose drugs for regular treatment of intestinal nematode infections. Both mebendazole and pyrantel-oxantel were very effective in eliminating Ascaris lumbricoides infection, inducing cure rates of more than 96% and reducing the mean egg counts by more than 95%. Both drugs had a moderate efficacy against Trichuris trichiura infection, but pyrantel-oxantel had a higher cure rate (31·5% vs. 23·3%, P < 0·01), though the reductions in egg counts did not differ significantly and were more than 80%. Pyrantel-oxantel and mebendazole had a similar, poor efficacy in curing hookworm infections and had a moderate effect in reducing the egg counts by 67% and 68%, respectively. Pyrantel-oxantel (10 mg/kg) offers a valuable alternative to mebendazole as a single-dose treatment for the control of intestinal nematode infections in children in endemic areas of sub-Saharan Africa, due to its comparable efficacy, its low cost and its suitability for use in young children.

Review of the Dispholidini, with the description of a new genus and species from Tanzania (Serpentes, Colubridae)

The tribe Dispholidini (Bourgeois 1968) is reviewed, paying particular attention to dentition and visceral anatomy. A new genus and species, Xyelodontophis uluguruensis, is described from the Uluguru Mountains in Tanzania. All five genera have enlarged rear maxillary teeth. Thrasops seems to be basal, Rhamnophis shows the development of dagger-like teeth tapering from base to tip, then the other three genera appear to radiate, with Xyelodontophis having more derived dagger teeth broadest in the middle, while Dispholidus and Thelotornis seem to have independently developed enlarged grooved rear fangs.Thrasops schmidti is recognised as a relict evolutionary species. No subspecies of Rhamnophis aethiopissa or Dispholidus typus are recognised, but the population of Dispholidus on Pemba Island probably represents an undescribed species.