Distribution and spread of pyrethroid and DDT resistance among the Anopheles gambiae complex in Tanzania

The development of insecticide resistance is a threat to the control of malaria in Africa. We report the findings of a national survey carried out in Tanzania in 2011 to monitor the susceptibility of malaria vectors to pyrethroid, organophosphate, carbamate and DDT insecticides, and compare these findings with those identified in 2004 and 2010. Standard World Health Organization (WHO) methods were used to detect knock‐down and mortality rates in wild female Anopheles gambiae s.l. (Diptera: Culicidae) collected from 14 sentinel districts. Diagnostic doses of the pyrethroids deltamethrin, lambdacyhalothrin and permethrin, the carbamate propoxur, the organophosphate fenitrothion and the organochlorine DDT were used. Anopheles gambiae s.l. was resistant to permethrin in Muleba, where a mortality rate of 11% [95% confidence interval (CI) 6–19%] was recorded, Muheza (mortality rate of 75%, 95% CI 66–83%), Moshi and Arumeru (mortality rates of 74% in both). Similarly, resistance was reported to lambdacyhalothrin in Muleba, Muheza, Moshi and Arumeru (mortality rates of 31–82%), and to deltamethrin in Muleba, Moshi and Muheza (mortality rates of 28–75%). Resistance to DDT was reported in Muleba. No resistance to the carbamate propoxur or the organophosphate fenitrothion was observed. Anopheles gambiae s.l. is becoming resistant to pyrethoids and DDT in several parts of Tanzania. This has coincided with the scaling up of vector control measures. Resistance may impair the effectiveness of these interventions and therefore demands close monitoring and the adoption of a resistance management strategy.     

The effect of maternal care on child survival: a demographic, genetic, and evolutionary perspective

Models of population dynamics generally assume that child survival is independent of maternal survival. However, in humans, the death of a mother compromises her immature children's survival because children require postnatal care. A child's survival therefore depends on her mother's survival in years following her birth. Here, we provide a model incorporating this relationship and providing the number of children surviving until maturity achieved by females at each age. Using estimates of the effect that a mother's death has on her child's survival until maturity, we explore the effect of the model on population dynamics. Compared to a model that includes a uniform child survival probability, our model slightly raises the finite rate of increase lambda and modifies generation time and the stable age structure. We also provide estimates of selection on alleles that change the survival of females. Selection is higher at all adult ages in our model and remains significant after menopause (at ages for which the usual models predict neutrality of such alleles). Finally, the effect of secondary caregivers who compensate maternal care after the death of a mother is also emphasized. We show that allocare (as an alternative to maternal care) can have a major effect on population dynamics and is likely to have played an important role during human evolution.     

Effects of adult body size on fecundity and the pre-gravid rate of Anopheles gambiae females in Tanzania

Abstract. The influence of adult body size on the pre-gravid state and fecundity was studied in Anopheles gambiae Giles females hand-caught inside houses and virgin females collected as pupae in Tanzania. Blood-fed mosquitoes were kept for 2-3 days before dissection and examination for insemination and ovarian condition. Those females which did not develop eggs were classified as pre-gravid. The number of mature eggs in those mosquitoes which became gravid was counted. Virgin females were fed and kept for egg maturation in the laboratory. Wing-length of females was measured as an index of mosquito size. The overall pre-gravid rate in the resting An. gambiae population was found to be 21% and, of these, 66% had been inseminated. In the virgin females the pre-gravid rate was 92.6%. The mean wing-length of wild females which became gravid was significantly larger than those which remained pre-gravid. There was a positive correlation between fecundity and wing-length. Smaller females tended to require two or three bloodmeals to facilitate completion of the first gonotrophic cycle. The critical size permitting oviposition from the first blood-meal was a wing-length of 3 mm.     

Reducing child malnutrition in Tanzania. Combined effects of income growth and program interventions.

Malnutrition is associated with an inadequate diet, poor health and sanitation services and inadequate care for young children. A combination of income growth and nutrition interventions are therefore suggested to adequately tackle this issue [Haddad, L., Alderman, H., Appleton, S., Song, L., Yohannes, Y., 2003. Reducing child malnutrition: how far does income growth take us? World Bank Econ. Rev., 17, 107-131.], yet evidence to support this claim is often not available, especially for African settings. This paper evaluates the joint contribution of income growth and nutrition interventions towards the reduction of malnutrition. Using a four round panel data set from northwestern Tanzania we estimate the determinants of a child's nutritional status, including household income and the presence of nutrition interventions in the community. The results show that better nutrition is associated with higher income, and that nutrition interventions have a substantial beneficial effect. Policy simulations make clear that if one intends to halve malnutrition rates by 2015 (the MDG objective), income growth will have to be complemented by large scale program interventions.     

A comparison of sex ratio,birth periods and calf survival among Serengeti wildebeest sub‐populations,Tanzania

Although adaptation and environmental conditions can easily predict demographic variation in most savannah ungulates, no study on demographic consequences arising from natural and anthropogenic factors among Serengeti wildebeest (Connochaetes taurinus) sub‐populations in Tanzania has been carried out. Here, I report estimates of annual sex ratio, calf and yearling survival rate and birth seasonality between resident and migratory sub‐populations to explore demographic patterns arising from the different age and sex structure. The results indicate significantly higher female‐biased sex ratios in the resident and almost even sex ratios among individual migrants. The calf recruitment estimated as mother: offspring ratios indicate a more synchronous birth in the migrant than the resident sub‐population. Also, birth seasonality in the migratory sub‐population coincided with seasonal variability of rainfall and the timing of the birth peak was more variable in the migrants than the resident sub‐population. The migratory sub‐population had a higher annual proportional mean calf survival estimate (0.84) than that of the residents (0.44) probably due to higher mortality resulting from predation in the western corridor. However, the proportion of yearling survival estimates was much lower (0.31) in the migrants and relatively higher (0.39) in the residents. Different demographic outcomes resulting from environment, predation, movements and ecological factors including resource competition have conservation implications for the two sub‐populations.     

Surface and leaf-litter arthropods in the coastal forests of Tanzania

Surface and leaf litter arthropod assemblages of the seasonal lowland coastal forests of eastern Tanzania were investigated from eleven sites over a 3-year period (1991–93). Pit-fall trap data show that four groups comprise more than 10% of the total sample: ants (Hymenoptera: Formicidae, 31%), grasshoppers and crickets (Orthoptera, 22%), beetles (Coleoptera: 17.39%) and spiders (Araneae: 13.48%). Arthropod abundance varies considerably with season, with greater total numbers of arthropods in all groups found in wetter periods. Arthropod abundance also varies considerably according to habitat, with greatest numbers found in forests with the most intact canopy cover, and in valley-bottom forest as compared to ridge-top forest; the valleys are normally both wetter and with a more complete and taller canopy. Tullgren Funnel data show that over 50% of the leaf litter fauna comprises tiny arthropods of the groups Collembola and Acarina. Abundance of arthropods in the leaf litter of these forests varies from a maximum of ≈ 16,000 m^–2, to a minimum of 780 m^–2. Abundance is highest in wetter periods, in the forest areas with the most intact canopy cover, and in valley-bottom as opposed to ridge-top habitats.     

Butterfly species richness and abundance in the Katavi ecosystem of western Tanzania

We sampled butterflies in six different habitat types in and around Katavi National Park, a remote reserve consisting primarily of miombo woodland and seasonal lakes in western Tanzania. Blendon traps set for 531 trap days and 143 h of butterfly netting at 35 sites yielded 186 species from five families over a 4‐month period during the wet season. Eight of these species constituted possible range extensions. Butterfly abundance and species richness were low in cultivated habitats but high in open riverine habitats; many butterfly species were found only in seasonally flooded grassland. This study constitutes the first butterfly species inventory from this poorly‐known national park, shows that protection of dry season water sources provides an important conservation service for invertebrates as well as large mammals, and that increased cultivation outside miombo parks can reduce local butterfly diversity.     

Comparison of sampling anopheline mosquitoes by light-trap and human-bait collections indoors at Bagamoyo, Tanzania

Abstract. The mosquito sampling efficiency of CDC miniature light-traps, relative to night-biting collections, was evaluated indoors at two sites in coastal Tanzania. We found that the total number of anophelines captured overnight by light-traps (hung beside a bednet in use) was 1.23 times the number of anophelines captured by human-bait collections. This relationship was not affected significantly by changes in the mosquito density, order of trapping method, date of sampling, or number of household occupants. Malaria sporozoite rates were twice as high among mosquitoes captured by light-trap as compared to those captured by night-biting collection. This was attributed to the tendency of light-traps to capture a larger proportion of gravid mosquitoes, which also had high sporozoite rates. The differences in sporozoites rates according to abdominal stage indicates that unfed mosquitoes captured by light-traps may define more precisely the human-biting activity and sporozoite rates as seen by night-biting collections. Our study shows that light-traps, when used in combination with night-biting collections, can be an effective and sensitive means for measuring human-biting activity and the sporozoite rate.     

Medicinal Plants of the Washambaa (Tanzania): Documentation and Ethnopharmacological Evaluation

Abstract: Medicinal plants are an important local resource for the Washambaa of the Western Usambara Mountains in Tanzania. In this study the Washambaa medicinal plants are inventoried. It is based on ethnobotanical fieldwork carried out over 15 months. This study presents for the first time an analysis of medicinal plants used in Africa with a ranking of these taxa by the frequency of their reported use. A total of 328 taxa were collected and yielded 2260 individual use reports. The most popular species are Myrica salicifolia and Toddalia asiatica. Subsequently, the use reports were arranged into 9 groups of medicinal uses based on the types of illness treated. The F actor of I nformant C onsensus (F_IC) is used in order to evaluate the ethnobotanical importance of the plants. The largest number of plants and of use reports are in the group of gastrointestinal disorders. For the most commonly used taxa, an ethnopharmacological evaluation was performed. Studies to evaluate the Washambaa therapeutic claims as well as toxicological data are still lacking for many of the species. This study will form the basis for pharmacological and phytochemical research on selected Washambaa medicinal plants.     

Observations on the susceptibility of Ctenocephalides felis (Siphonaptera: Pulicidae) to malathion and permethrin in Tanzania

Laboratory-reared Ctenocephalides felis (Bouche) adults were tested with 0.5% malathion and 0.5% permethrin, using the standard WHO methods. After 24 h exposure to malathion (3.6 mg/cm2), 92% of the fleas died. The LT50 for malathion was approximately 8 h. Permethrin (0.45 mg/cm2) produced 100% mortality of exposed insects after 24 h while with a higher dose (0.9 mg/cm2) all fleas died after 8 h exposure. LT50 for the two doses of permethrin were 7.7 and 1.05 h, respectively. The failure of the diagnostic dose of malathion to kill 100% of the population was attributed to resistance. Permethrin is a suitable pesticide for controlling fleas of domestic animals in Tanzania.     

Describing the current status of Plasmodium falciparum population structure and drug resistance within mainland Tanzania using molecular inversion probes

High‐throughput Plasmodium genomic data is increasingly useful in assessing prevalence of clinically important mutations and malaria transmission patterns. Understanding parasite diversity is important for identification of specific human or parasite populations that can be targeted by control programmes, and to monitor the spread of mutations associated with drug resistance. An up‐to‐date understanding of regional parasite population dynamics is also critical to monitor the impact of control efforts. However, this data is largely absent from high‐burden nations in Africa, and to date, no such analysis has been conducted for malaria parasites in Tanzania countrywide. To this end, over 1,000 P. falciparum clinical isolates were collected in 2017 from 13 sites in seven administrative regions across Tanzania, and parasites were genotyped at 1,800 variable positions genome‐wide using molecular inversion probes. Population structure was detectable among Tanzanian P. falciparum parasites, approximately separating parasites from the northern and southern districts and identifying genetically admixed populations in the north. Isolates from nearby districts were more likely to be genetically related compared to parasites sampled from more distant districts. Known drug resistance mutations were seen at increased frequency in northern districts (including two infections carrying pfk13‐R561H), and additional variants with undetermined significance for antimalarial resistance also varied by geography. Malaria Indicator Survey (2017) data corresponded with genetic findings, including average region‐level complexity‐of‐infection and malaria prevalence estimates. The parasite populations identified here provide important information on extant spatial patterns of genetic diversity of Tanzanian parasites, to which future surveys of genetic relatedness can be compared.     

Sighting frequency and food habits of the leopard tortoise, Geochelone pardalis, in northern Tanzania

Sighting frequency and food habits of the leopard tortoise (Geochelone pardalis) were studied in northern Tanzania from October 1993 to June 1996. Sighting frequency varied significantly between protected (0.22 mhr^?1) and unprotected sites (0.59 mhr^?1), and between Arusha (0.27 mhr^?1) and Serengeti sites (0.56 mhr^?1). The tortoise diet comprised mostly plants (97.8%) and rarely inorganic matter (2.2%). A total of 47 plant species from 21 families was eaten. Forbs made up 74.5% of the plant items and monocots the remainder. Succulents contributed 51.0% of the plant items eaten while grasses and legumes accounted for 16.8% and 13.5%, respectively. Some plant items were eaten more frequently than their occurrence in the habitats.     

Post-sampling dissolution and the consistency of nannofossil diversity measures: A case study from freshly cored sediments of coastal Tanzania

This study investigates the potentially deleterious effect of prolonged sample storage on the reliability of calcareous nannofossil species abundance and community diversity measures and their subsequent interpretation as paleoceanographic proxies. Nannofossil assemblages from two freshly cored successions of hemipelagic clay were documented over a one-year period using a series of paired smear-slides, the first made from sediment samples within a day of coring and the second either 6 months or 1 year later. Diversity measured by Shannon's H is consistent between the two sets for the majority of samples, however significant changes, both positive and negative, were recorded in a number of cases and appear to be largely due to variations in smear-slide thickness and not to post-sampling dissolution. There is no significant change in nannofossil fragmentation or abundance over time, although the relative abundances of small, dissolution susceptible placoliths of Reticulofenestra minuta do appear to decrease with time in some samples. Counts of mineral grains show that there is a significant loss of fine, 1–2 μm, cubic pyrite within months of drilling, and this, combined with the decline in abundance of R. minuta, suggests that limited pyrite oxidation coupled to carbonate dissolution is occurring. Geochemical analyses confirm that these sediments contain significant concentrations of sulphate one year after sample recovery, which may be the result of gypsum formation associated with the oxidation of pyrite. Estimates of pyrite oxidation suggest that up to 3% of the original calcium carbonate has dissolved in the year after coring, which could account for the observed loss of small placoliths. Effects of this kind are almost certainly confined to hemipelagic sequences rich in organic matter and/or reduced iron but are frequently offset by the exceptional preservation of calcareous microfossils that can occur within such sediments.     

Prevalence of Schistosomes and Soil-Transmitted Helminths among Schoolchildren in Lake Victoria Basin,Tanzania

The objectives of this study was to conduct a survey on schistosomiasis and soil-transmitted helminth (STH) infections in order to come up with feasible control strategies in Lake Victoria basin, Tanzania. Depending on the size of the school, 150-200 schoolchildren were recruited for the study. Duplicate Kato-Katz stool smears were prepared from each child and microscopically examined for Schistosoma mansoni and STHs. Urine specimens were examined for Schistosoma haematobium eggs using the filtration technique. After the survey, mass drug administration was done using praziquantel and albendazole for schistosomiasis and STHs infections, respectively. A total of 5,952 schoolchildren from 36 schools were recruited for the study and had their stool and urine specimens examined. Out of 5,952 schoolchildren, 898 (15.1%) were positive for S. mansoni, 754 (12.6%) for hookworms, 188 (3.2%) for Ascaris lumblicoides, and 5 (0.008%) for Trichuris trichiura. Out of 5,826 schoolchildren who provided urine samples, 519 (8.9%) were positive for S. haematobium eggs. The results revealed that intestinal schistosomiasis, urogenital schistosomiasis, and STH infections are highly prevalent throughought the lake basin. The high prevalence of intestinal and urogenital schistosomisiasis in the study area was a function of the distance from Lake Victoria, the former being more prevalent at localities close to the lake, whilst the latter is more so away from it. Control of schistosomiasis and STHs in the study area requires an integrated strategy that involves provision of health education to communities, regular treatments, and provision of adequate safe water supply and sanitation facilities.     

Towards an ecohydrology-based restoration of the Usangu wetlands and the Great Ruaha River, Tanzania

An open channel flow model, calibrated against field data, suggests that cattle intrusion in the eastern Usangu wetlands, as well as both dry and wet weather irrigation upstream, are responsible for the seasonal drying out of the Great Ruaha River (GRR) downstream. This human-induced change has severe socio-economic implications downstream, including hindering hydroelectricity production, as well as a devastating impact on the Ruaha National Park (RNP) ecosystem that is now shifting from wet tropics to dry tropics. To ensure sustainable development, governance is urgently needed for the Usangu catchment in a way that is compatible with ecohydrology principles for the sustainable use of water resources. In order to do that, perennial flow must be restored to the GRR. For this to happen this study suggests that all the livestock must be removed from the eastern Usangu wetlands and dry weather irrigators must return at least 25% (∼4 m³ s⁻¹) of the water to the river.     

Changing places: how the results of new field work in the Rubeho Mountains influence conservation priorities in the Eastern Arc Mountains of Tanzania

The Rubeho Mountains are a poorly studied mountain block within the Eastern Arc Mountain range of Tanzania and Kenya. We present the results of field surveys for vertebrates undertaken during the period February 2000 to December 2002. One hundred and twelve man‐days of surveys recorded 35 mammal, 107 bird, ten reptile and nine amphibian species, including eleven species endemic and seven near‐endemic to the Eastern Arc, with one species new to science. Of these, nine species are regarded as threatened with extinction. The new survey data significantly elevate the biological importance of the Rubehos within the Eastern Arc range. Further analyses highlight how the overall biological ranking of the Eastern Arc mountain blocks is correlated with survey effort. The majority of the forest habitat on the Rubehos is contained in three national (Central Government) Forest Reserves (Mang'alisa, Mafwomero and Ukwiva). Our surveys recorded high levels of disturbance to the forest habitat in all three reserves and we draw attention to the need for additional conservation investment in this area.     

Deforestation and biodiversity: effects of bushland cultivation on dung beetles in semi-arid Tanzania

Dung beetles provide important ecosystem services in the habitats where they occur. The activity of dung beetles enhances soil nutrient cycling and increases the soil’s ability to absorb and hold water. Consequently, these beetles are particularly important in semi-arid environments. This study analyses the importance of remaining wooded habitat patches (bushland) for the survival of a diverse dung beetle fauna in an otherwise cultivated landscape in semi-arid Tanzania. Dung beetles were sampled by pitfall trapping in maize fields and bushland habitats. In total, 6037 dung beetles (Scarabaeidae: Scarabaeinae), representing 77 species from 25 genera, were collected. Many species, particularly amongst the ball-rollers, showed a clear preference for wooded patches, species richness being significantly higher in the bushland patches than in the cultivated sites. The number of trapped specimens in bushland was also considerably higher than that found in maize fields, although the differences were not significant. In conclusion, bushland fragments appear to have an important conservation value as to maintaining a high diversity and abundance of dung beetles, thereby enhancing the ecosystem services provided by these beneficial insects.     

Fertility and child spacing among the urban Poor in a Third World city: The case of Calcutta,India

Studies of fertility behavior in the Third World have relied heavily on two variables, income and education, to explain variations in fertility rates. If the socio-economic variables traditionally employed to account for variations in fertility rates are invariant, what other factors could influence fertility rates and child spacing? On the basis of data from 180 slum households in Calcutta, India, the paper indicates that in a situation where material and social conditions are comparable, cultural and demographic variables play a major role in influencing reproductive behavior. In this case study, caste and family type are shown to have a significant effect on the numbers of surviving children. As regards child spacing, the woman's age is of paramount importance.     

Causes and consequences of increase in child survival rates: ethnoepidemiology among the Hmong of Thailand.

The Hmong "hill tribe" minority in Thailand has much higher exposure to factors usually associated with risk of child mortality (high fertility, low status of women, low education, less use of modern medical care for births, exposure to warfare, economic and physical disruption, and poor hygienic conditions) than the rural ethnic Thai population. Nonetheless, infant mortality has declined from over 120 per 1000 to under 50 per 1000 live births among both these populations in the past 30 years. The reason for the rapid increase in child survival among the Hmong appears to be better access to and more use of modern curative and preventive medical care associated with road construction rather than major changes in social or hygienic conditions. Conventional wisdom suggests that high fertility is both a cause and a consequence of high infant and child mortality and that parents will not reduce fertility until they see that mortality has declined. Most Hmong parents recognize the decline in child mortality and attribute it to better access to modern medical care. Most Hmong parents also say that, if they were starting to have children now, they would want to have fewer children. Fear of child death is infrequently mentioned as a motive for having more children, and the perceived decline in child mortality is rarely mentioned as a reason for reduced fertility. Most Hmong parents explain their desired family size in terms of economic conditions rather than perceived risk of child mortality. Results of this study suggest that fertility and child mortality can vary independently of one another and that major reductions in child mortality can be accomplished without waiting for major social changes (e.g., improved education or status of women) or major reductions in fertility.