Southwestern Tanzania Research Articles

Structural Controls on Orogenic Au Mineralization During Transpression: Lupa Goldfield, Southwestern Tanzania

Au mineralization in the western Lupa goldfield, southwestern Tanzania was associated with transpression and reverse sinistral slip along a network of steeply S dipping shear zones with non-Andersonian geometries. Slip was accommodated by: (1) frictional failure and sliding during emplacement of quartz ± Au-bearing veins; and (2) crystal plasticity and fluid-assisted diffusive mass transfer. The Kenge mineral system is situated along a NW-SE-trending shear zone and is characterized by ≤10-m thick, Au-bearing fault-fill veins hosted by well-developed phyllosilicate-rich mylonites. The broadly contemporaneous Porcupine mineral system is situated along an ENE-WSW– to E–W-trending shear zone, which is characterized by narrow, discontinuous mylonitic shear zone within a silicified and nonfoliated granitoid protolith. Au mineralization at Porcupine occurs within steeply dipping fault-fill and subhorizontal extension/oblique-extension veins. Three-dimensional frictional reactivation theory provides a self-consistent explanation for the different vein styles at Kenge and Porcupine and extends the classic fault valve model to the general case of oblique slip along multiple, arbitrarily oriented shear zones. Analysis of the differential stress required for frictional reactivation suggests the following: (1) the Kenge shear zone was intrinsically weaker than the Porcupine shear zone, consistent with the lack of well-developed mylonites at Porcupine; and (2) frictional reactivation of the Kenge shear zone occurred under suprahydrostatic but sublithostatic pore fluid pressures, whereas frictional reactivation of the Porcupine shear zone occurred under near-lithostatic fluid pressures. We hypothesize that near-lithostatic pore fluid pressures relieved effective normal stresses at grain-grain contacts, helping to preserve intragranular and fracture porosity at the Porcupine orebody. As such, these pore spaces may be important microstructural sites for Au mineralization. Low effective normal stresses can also explain the poorly developed phyllosilicate-rich mylonites and limited degree of shear zone weakening at Porcupine.

A new archosauriform (Reptilia: Diapsida) from the Manda beds (Middle Triassic) of southwestern Tanzania.

BackgroundArchosauria and their closest relatives, the non-archosaurian archosauriforms, diversified in the Early and Middle Triassic, soon after the end-Permian extinction. This diversification is poorly documented in most Lower and Middle Triassic rock sequences because fossils of early groups of archosauriforms are relatively rare compared to those of other amniotes. The early Middle Triassic (? late Anisian) Manda beds of southwestern Tanzania form an exception, with early archosaur skeletons being relatively common and preserved as articulated or associated specimens. The Manda archosaur assemblage is exceptionally diverse for the Middle Triassic. However, to date, no non-archosaurian archosauriforms have been reported from these rocks.Methodology/Principal FindingsHere, we name a new taxon, Asperoris mnyama gen. et sp. nov., from the Manda beds and thoroughly describe the only known specimen. The specimen consists of a well-preserved partial skull including tooth-bearing elements (premaxilla, maxilla), the nasal, partial skull roof, and several incomplete elements. All skull elements are covered in an autapomorphic highly rugose sculpturing. A unique combination of character states indicates that A. mnyama lies just outside Archosauria as a stem archosaur within Archosauriformes, but more precise relationships of A. mnyama relative to other early archosauriform clades (e.g., Erythrosuchidae) cannot be determined currently.Conclusions/Significance Asperoris mnyama is the first confirmed non-archosaurian archosauriform from the Manda beds and increases the morphological and taxonomic diversity of early archosauriforms known from the Middle Triassic. The direct association of A. mnyama with species referable to Archosauria demonstrates that non-archosaurian archosauriforms were present during the rise and early diversification of Archosauria. Non-archosaurian archosauriforms and archosaurs co-occur in fossil reptile assemblages across Pangaea from the late Early Triassic to the end of the Late Triassic.

Hookworm Infection and Environmental Factors in Mbeya Region, Tanzania: A Cross-Sectional, Population-Based Study

BackgroundHookworm disease is one of the most common infections and cause of a high disease burden in the tropics and subtropics. Remotely sensed ecological data and model-based geostatistics have been used recently to identify areas in need for hookworm control.MethodologyCross-sectional interview data and stool samples from 6,375 participants from nine different sites in Mbeya region, south-western Tanzania, were collected as part of a cohort study. Hookworm infection was assessed by microscopy of duplicate Kato-Katz thick smears from one stool sample from each participant. A geographic information system was used to obtain remotely sensed environmental data such as land surface temperature (LST), vegetation cover, rainfall, and elevation, and combine them with hookworm infection data and with socio-demographic and behavioral data. Uni- and multivariable logistic regression was performed on sites separately and on the pooled dataset.Principal FindingsUnivariable analyses yielded significant associations for all ecological variables. Five ecological variables stayed significant in the final multivariable model: population density (odds ratio (OR) = 0.68; 95% confidence interval (CI) = 0.63–0.73), mean annual vegetation density (OR = 0.11; 95% CI = 0.06–0.18), mean annual LST during the day (OR = 0.81; 95% CI = 0.75–0.88), mean annual LST during the night (OR = 1.54; 95% CI = 1.44–1.64), and latrine coverage in household surroundings (OR = 1.02; 95% CI = 1.01–1.04). Interaction terms revealed substantial differences in associations of hookworm infection with population density, mean annual enhanced vegetation index, and latrine coverage between the two sites with the highest prevalence of infection.Conclusion/SignificanceThis study supports previous findings that remotely sensed data such as vegetation indices, LST, and elevation are strongly associated with hookworm prevalence. However, the results indicate that the influence of environmental conditions can differ substantially within a relatively small geographic area. The use of large-scale associations as a predictive tool on smaller scales is therefore problematic and should be handled with care.

Water governance and livelihoods: Outcomes for smallholders on the Usangu plains, Tanzania

How does water governance change over time? What are the outcomes for smallholders and the ecosystems that support them? We review the development of water resources management over the past 40 years in the Kimani catchment of the Usangu plains, in southwestern Tanzania. Our analysis is based on a conceptual framework for water governance comprising a system of resources, arrangements for access, and outcomes for people and ecosystems. We discuss how the resources for water governance have changed over time, we consider the changing arrangements for water allocation, particularly relating to water rights, water management organisations and physical infrastructure, and we analyse the outcomes in terms of access to water for people and of maintenance of environmental flows. Development of water resources in Kimani has been successful on many counts, resulting in assured supplies for many users, with consequent improvements in livelihoods, including, in particular, increases in land-holding size. However, these improvements are accompanied by some negative outcomes, as they reduce water access for other users and threaten downstream flows. The experiences from Kimani highlight the need to map the whole institutional landscape and to ensure that physical infrastructure reflects institutional arrangements when designing interventions to enhance water security. Such interventions may well have significant outcomes for equity and power relations amongst water users.

Stakeholders’ participation in planning and priority setting in the context of a decentralised health care system: the case of prevention of mother to child transmission of HIV programme in Tanzania

BackgroundIn Tanzania, decentralisation processes and reforms in the health sector aimed at improving planning and accountability in the sector. As a result, districts were given authority to undertake local planning and set priorities as well as allocate resources fairly to promote the health of a population with varied needs. Nevertheless, priority setting in the health care service has remained a challenge. The study assessed the priority setting processes in the planning of the prevention of mother to child transmission of HIV (PMTCT) programme at the district level in Tanzania.MethodsThis qualitative study was conducted in Mbarali district, south-western Tanzania. The study applied in-depth interviews and focus group discussions in the data collection. Informants included members of the Council Health Management Team, regional PMTCT managers and health facility providers.ResultsTwo plans were reported where PMTCT activities could be accommodated; the Comprehensive Council Health Plan and the Regional PMTCT Plan that was donor funded. As donors had their own globally defined priorities, it proved difficult for district and regional managers to accommodate locally defined PMTCT priorities in these plans. As a result few of these were funded. Guidelines and main priority areas of the Ministry of Health and Social Welfare (MoHSW) also impacted on the ability of the districts and regions to act, undermining the effectiveness of the decentralisation policy in the health sector.ConclusionThe challenges in the priority setting processes revealed within the PMTCT initiative indicate substantial weaknesses in implementing the Tanzania decentralisation policy. There is an urgent need to revive the strategies and aims of the decentralisation policy at all levels of the health care system with a view to improving health service delivery.

Geochemistry and U–Pb zircon dating of the high-K calc-alkaline basaltic andesitic lavas from the Buanji Group, south-western Tanzania

SHRIMP zircon U–Pb and Sm–Nd isotopic data together with major and trace elements data are presented for the basalt andesitic lavas from the Buanji Group, south-western Tanzania in order to establish their emplacement age, ascertain their mantle sources and processes responsible for their generation. Zircon U–Pb data shows that the Buanji Group lavas were emplaced at 1674±15Ma and do not therefore belong to the Neoproterozoic Bukoban Supergroup. Having erupted on top of sedimentary rocks, the 1674±15Ma age of the volcanic rocks provides the younger limit to the age of deposition of underlying un-dated sediments.The Bunaji Group lavas are amygdaloidal and contain euhedral phenocrysts of plagioclase+orthopyroxene+clinopyroxene as well as subhedral quartz and opaque minerals mainly magnetite with quartz filling in the interstices. As a suite, they are compositionally uniform and are classified as high-K calc-alkaline basaltic andesites. The samples display coherent and fractionated REE patterns with La/SmCN and La/YbCN ratios of 2.48–2.72 and 4.03–5.92, respectively; and are characterized by negative Eu anomalies (Eu/Eu*=0.76–0.84). They are depleted in Nb, Ta, Ti and Sr but enriched in the most incompatible elements Rb, Ba, Th, U, K, and Pb leading to high ratios of Ba/Ta (531–1358) and Ba/Nb (35–91, with one outlier). They exhibit Hf/Yb ratios=1.31–1.52, sub-chondritic ratios of Nb/Ta (13–18) and Zr/Hf (32–38), characteristics of shallow melting of mantle derived magmas. The samples display Th/Nb ratios of 0.48–0.95 and have εNd (1.67Ga) values of +0.22 to +2.34 which are much lower than the corresponding εNd (1.67Ga) mantle value of +6.55; characteristics indicative of contamination by the older crust.The geochemical features of the Buanji Group high-K calc-alkaline basaltic andesites are interpreted in terms of derivation of these rocks by partial melting of the a spinel lherzolite mantle wedge that has been metasomatized by the subduction related fluids in a late Paleoproterozoic continental convergent margin. The resultant magmas were subsequently contaminated by the felsic crust prior to their emplacement.

Ultra-high temperature granulite-facies metamorphic rocks from the Mozambique belt of SW Tanzania

The metamorphic rocks in the Neoproterozoic (Pan-African) Mozambique belt of southwestern Tanzania, around the town of Songea, can be subdivided into one- and two pyroxene bearing charnockitic gneisses, migmatitic granitoid gneisses and amphibolite-facies metapelites. Lower-grade amphibolite-facies rocks are rare and can be classified as sillimanite- and/or garnet-bearing metapelites. Most of the studied charnockitic gneisses show excellent corona textures with large orthopyroxene grains rimmed by clinopyroxene, followed by quartz and well developed garnet rims due to the reaction Opx+Pl=Grt+Cpx+Qtz that formed during isobaric cooling. These and other charnockitic gneisses show symplectites of orthopyroxene and An-rich plagioclase that resulted from the breakdown of garnet during isothermal decompression due to the reaction Grt+Cpx+Qtz=Opx+Pl. Geothermobarometric calculations yield up to ~1050°C and up to ~12kbar for peak metamorphic conditions. These are higher temperature and slightly lower pressure conditions than reported for other granulite-facies terrains in the Mozambique belt of Tanzania. Single zircon Pb–Pb evaporation and U-Pb SHRIMP ages for magmatic zircons extracted from two charnockitic and two granitic gneisses cluster in two groups, one at ~750Ma and one at ~1150Ma with the older reflecting the time of emplacement of the igneous precursors, and the younger approximating the time of charnockitization. These protolith ages are similar to those farther east in the Masasi area of southern Tanzania, as well as in northern Mozambique and in southern Malawi, and suggest that the Mozambique belt consists of chronologically heterogeneous assemblages whose pre-metamorphic tectonic setting remains obscure.

Transition of Shifting Cultivation and its Impact on People’s Livelihoods in the Miombo Woodlands of Northern Zambia and South-Western Tanzania

Shifting cultivation has long been a major livelihood for people in the miombo woodlands of southern, central and eastern Africa. However, increasing deforestation and forest degradation throughout the region are resulting in growing pressure on traditional shifting agricultural systems. Indeed, agricultural intensification and expansion itself is considered the primary cause of miombo deterioration, which is driven by both endogenous and exogenous variables operating at various scales. On the basis of data collected in the 1990s and 2010 from two villages in Northern Province, Zambia and two in the Rukwa Region, Tanzania, the paper will document the transition of shifting cultivation towards more intensive land use practices. It is argued that the main drivers influencing miombo degradation, and thereby the transition process of traditional shifting cultivation practices, have been a growing population, government policies, and an increasing commercialization/market integration. Questionnaires, focus group meetings, and in-depth interviews reveal that despite the breakdown of the traditional shifting cultivation practices, a general improvement of livelihoods has taken place. This has happened through adaptation and diversification in both agricultural practices and livelihood activities. However, it is also seen that because of the often rapidly changing external factors (market conditions and policies), life in the shifting cultivation communities involves a continual shift of emphasis among a variety of livelihood strategies.

African Swine Fever Virus, Tanzania, 2010–2012

African Swine Fever Virus, Tanzania, 2010–2012

Karibu Stranger, Come Heal Thy Host: Hospitality as Historical Subject in Southwestern Tanzania, 1600–1900

This study focuses on hospitality in Tanzania, as a topic of historical importance. Although there are many references to hospitality within both primary and secondary sources and anecdotal accounts, hospitality is effectively unexplored in the historical scholarship for any part of sub-Saharan Africa. Looking at southwestern Tanzania between 1600 and 1900 as a case study, this work aims to make hospitality, for the first time, primary focus of historical study rather than a peripheral and passing allusion. Towards that end, I examine why and when some societies chose to extend hospitality to outsiders and strangers. In southwestern Tanzania between the sixteenth and nineteenth centuries, extending hospitality to guests, strangers, and ‘foreign residents’ was a paramount value and social expectation, which could result in inclusion of outsiders. Hospitality towards newcomers became a cultural norm. I contend that direct, immediate, and personal gain was far less important than a circulation of hospitality. In the long term social and political institutions were buoyed by this moral expectation. In order to demonstrate these claims, I employ proverbs, oral traditions, and explorers’ accounts as historical evidence for hospitality's enduring salience in shifting contexts in southwestern Tanzania from precolonial times into the twentieth century.

Fipa cattle in the southwestern highlands of Tanzania: molecular characterization

This study aimed at characterising the genetic diversity of two Fipa cattle populations (Sumbawanga and Nkasi) of South-Western Tanzania, and establishing their genetic relationships with the other indigenous cattle strains (Tarime, Iringa red and Ankole) and Friesian cattle found in the area. The genetic diversity was analysed using 30 microsatellite markers. All the markers used were highly polymorphic. The Nkasi Fipa cattle exhibited the highest mean number of alleles (7.31) and mean genetic diversity (0.732) per locus, followed by Sumbawanga Fipa cattle with 7.10 mean number of alleles and 0.725 mean genetic diversity per locus, with the latter population having a very low mean inbreeding coefficient (FIS = 0.027). Three percent of the genetic diversity was due to differences among indigenous strains while the rest was due to differences among individuals within the strains. Small genetic distances (DA) were observed between Sumbawanga Fipa and Nkasi Fipa (0.032), Tarime (0.073), Iringa red (0.076) and Ankole cattle (0.086). As expected, the largest genetic distances were observed between the Friesian and all indigenous strains since this breed has a quite distinct genetic origin. In the assignment test, the proportion of animals from each group correctly assigned to their source population ranged from 55.3 percent (for Nkasi Fipa) to 100 percent (for Friesian). Despite the low genetic differentiation and genetic indistinctiveness of the Sumbawanga Fipa population from the other indigenous strains, its high genetic diversity, very low inbreeding coefficient and a threat emanating from population admixture with other indigenous strains underscore the importance of establishing appropriate conservation and management strategies for it.

Redescription of the archosaurParringtonia gracilisfrom the Middle Triassic Manda beds of Tanzania, and the antiquity of Erpetosuchidae

AbstractParringtonia gracilisHuene, 1939 is represented by both cranial and postcranial material collected from the lower Middle Triassic (Anisian) Lifua Member of the Manda beds in southwestern Tanzania. This aberrant taxon was previously proposed to have affinities with pseudosuchian archosaurs, and specifically with the enigmaticErpetosuchus grantifrom the Upper Triassic of Scotland. Here, we confirm the close affinities ofParringtonia gracilisandErpetosuchus grantibased on the following unambiguous synapomorphies: mediolaterally expanded posterior portion of the maxilla, alveoli present only in the anterior half of the maxilla, and absence of tooth serrations. Furthermore, the two taxa share osteoderms with deep sculpturing, a deep fossa on the dorsal margin of the neural spines and a heavily waisted shaft of the scapula. We added bothParringtonia gracilisandErpetosuchus grantiinto a comprehensive phylogenetic analysis of early archosaurs and found that these taxa are clearly referable to Archosauria but that relationships are poorly resolved at the base of this clade. However, our analysis demonstrates thatErpetosuchus grantiis not closely related to Crocodylomorpha, as has been hypothesized previously. The Erpetosuchidae are a clade of small-bodied archosaurs that have a poor fossil record but have members from both northern and southern Pangaea, ranging temporally from the Middle to Late Triassic. Thus, Erpetosuchidae is part of the early archosaurian radiation.

Fipa cattle in the southwestern highlands of Tanzania: morphometric and physical characteristics

Assessment of diversity is a prerequisite for the management and conservation of farm animal genetic resources. To study the morphological features of Fipa cattle in Southwestern Tanzania, 108 herds were studied. Fourteen body measurements (body weight, body length, height at withers, heart girth, ear length, ear width, horn length, horn-base thickness, horn-base spacing, horn-tip spacing, rump width, rump length, tail length and tail-base thickness) and qualitative traits were recorded from 307 animals. Measurements were classified according to location and animal sex. Both location and sex significantly (P < 0.05) influenced all the measurements, with castrates and bulls superseding cows. Most measurements were positively and highly significantly (P < 0.001) correlated with the body weight predicted accurately from heart girth. The animals had variable colour patterns, but being predominantly red (20.9 percent), pied black and white (18.6 percent), black (17.9 percent) and pied red and white (14.7 percent). All animals had sloping rumps and most (81.8 percent) had small-sized humps. Most (94.8 percent) animals had pyramid-shaped humps located in the cervico-thoracic position. Most (91.5 percent) animals had upward�forward oriented and lyre-shaped horns. All the animals had flat faces and backs, and laterally oriented ears. Most (97.1 percent) animals had medium-sized dewlaps, medium-sized teats (93.6 percent) and medium-sized quarters (87.2 percent). The navel flap was absent in most (87.6 percent) animals. Thus, the Fipa cattle can be classified as a medium-sized strain with considerable variation in body size and morphological features within and between districts.

Irrigation Scheduling Impact Assessment MODel (ISIAMOD): A decision tool for irrigation scheduling

This paper presents a process-based simulation known as Irrigation Scheduling Impact Assessment MODel (ISIAMOD). It was developed to simulate crop growth & yield, soil water balance and water management response indices to define the impact of irrigation scheduling decisions. ISIAMOD was calibrated and validated using data from field experiments on the irrigated maize crop conducted in an irrigation scheme located in south western Tanzania. The model adequately simulates crop biomass yield, grain yield, seasonal evapotranspiration and average soil moisture content in the crop effective rooting depth. Some unique features of this model make it a major improvement over the existing crop-soil simulation models. Keywords: Simulation model, Irrigation scheduling, Water management, Crop water productivity, ISIAMOD

Irrigation Scheduling Impact Assessment MODel (ISIAMOD): a Decision Tool for Irrigation Scheduling

This paper presents a process-based simulation known as Irrigation Scheduling Impact Assessment MODel (ISIAMOD). It was developed to simulate crop growth&yield, soil water balance and water management response indices to define the impact of irrigation scheduling decisions. ISIAMOD was calibrated and validated using data from field experiments on the irrigated maize crop conducted in an irrigation scheme located in south western Tanzania. The model adequately simulates crop biomass yield, grain yield, seasonal evapotranspiration and average soil moisture content in the crop effective rooting depth. Some unique features of this model make it a major improvement over the existing crop-soil simulation models.

Rock phosphate and lime for small-scale farming in Tanzania, East Africa

Poor soils are a major cause of poverty in sub-Saharan Africa, and thus restoration of soil fertility is a significant challenge for sustainable agriculture. Some of the main resources required, e.g. phosphate and lime, are present in many African countries and can be used by smallholder farmers in a relatively unprocessed form instead of expensive commercial fertilisers. Here we present a small study of the Mbeya region in Tanzania, which locally has both phosphate and lime. Most soils in sub-Saharan Africa are losing nutrients necessary for sustainable agriculture. This is mainly due to intensive farming and the fact that the nutrients are not replaced adequately. Further reasons for nutrient losses are leaching, soil erosion and fixation by iron and aluminium oxides. Vast areas experience moderate to acute phosphorus deficiency (Vanlauwe &amp; Giller 2006). The Mbeya region in south-western Tanzania (Fig. 1) is characterised by intensive smallholder plots along with several local sources of phosphate-bearing rocks and limestone. The former were examined in the 1980s (Chesworth et al.1988, 1989), but have never been utilised (Kalvig et al. 2010).

Fipa cattle in the southwestern highlands of Tanzania: socio-economic roles, traditional management practices and production constraints

This study aimed at determining the socio-economic roles, traditional management practices and production constraints of the Fipa cattle, was conducted in Rukwa region of South-Western Tanzania, using a structured questionnaire. The results indicate that most (90.8 percent) of the respondents depended on crop and livestock production for household income and food security. The Fipa cattle were preferred to other cattle strains by most (91.6 percent) of the farmers owing to their multiple socio-economic functions, adaptive qualities and low management requirements. The Fipa cattle were essentially kept for provision of draught power, income, manure, meat and security against uncertainties. Herded grazing on communal land was practiced by most (99.2 percent) of the farmers all the year-round without any supplementation. However, most (87.5 percent) farmers utilized crop residues in situ during the dry season, after harvesting cereal crops. Kraals made of untreated thorny bushes were the predominant shelters used for Fipa cattle by most (95.8 percent) of the respondents. The majority of respondents mentioned diseases/parasites (94.2 percent) and feed shortages (61.7 percent) during the dry season as the main production constraints. The farmers’ preference for Fipa cattle coupled with the multiple roles of the cattle and traditional management practices used by farmers should be used as the entry point for improvement and sustainable utilization of the strain.

Intraseasonal atmospheric variability and its interannual modulation in Central Africa

The spatial and temporal structures of the intraseasonal atmospheric variability over central Africa is investigated using 2.5° × 2.5° daily outgoing longwave radiation (OLR) and National Centers for Environmental Prediction (NCEP) Reanalysis zonal winds for the period 1980–2010. The study begins with an overview of the Central African rainfall regime, noting in particular the contrast amongst Western and Eastern parts, with different topography and surface conditions features. The annual mean rainfall and OLR over the region revealed a zone of intense convective activity centered on the equator near 30°E, which extends southward and covers almost all the Congo forest. The annual cycle of rainfall reflects the classical bi-annual shift of Inter-Tropical Convergence Zone across the equatorial belt, between 10°S and 10°N. The result of the empirical orthogonal functions (EOFs) analysis has shown that the three leading EOF modes explain about 45 % of total intraseasonal variability. The power spectra of all the three corresponding principal components (PCs) peak around 45–50 days, indicating a Madden–Julian Oscillation (MJO) signal. The first mode exhibits high positive loadings over Northern Congo, the second over Southern Ethiopia and the third over Southwestern Tanzania. The PCs time series revealed less interannual modulation of intraseasonal oscillations for the Congo mode, while Ethiopian and Tanzanian modes exhibit strong interannual variations. Hovmoller plots of OLR, 200 and 850 hPa NCEP zonal winds found the eastward propagating features to be the dominant pattern in all the three times series, but this propagation is less pronounced in the OLR than in the 850 and 200 hpa zonal wind anomalies. An index of MJO strength was built by averaging the 30–50 day power for each day. A plot of MJO indices and El Nino Southern Oscillation (ENSO) cycle confirm a strong interannual modulation of MJO over Eastern central Africa partially linked with the ENSO events (El Nino and La Nina). Strong MJO activity is observed during La Nina years or during ENSO-neutral years, while weak or absent MJO activity is typically associated with strong El Nino episodes.

Species limits within the Praomys delectorum group (Rodentia: Muridae: Murinae) of East Africa: a morphometric reassessment and biogeographical implications

We examined approximately 600 specimens that represent the Praomys delectorum species group (Muridae: Murinae: Praomyini), a rodent complex restricted to Afromontane landscapes in East Africa and currently viewed as a single species. Morphometric analyses of 21 population samples consistently disclosed cohesive patterns of craniodental differentiation that support the recognition of three species: Praomys delectorum Thomas, confined to extreme southern Malawi; P. melanotus Allen & Loveridge, found in highlands of south-western Tanzania and contiguous northern Malawi; and P. taitae Heller (including octomastis Hatt), distributed in mountains and foothills of southern Kenya and northern and central Tanzania. Populations of the P. delectorum group are patchily distributed in moist montane forest, most collecting localities falling within 1000–2400 m, and their range collectively coincides with the Tanganyika-Nyasa Montane Forest Group sensu Moreau. Patterns of faunal similarity derived from distributions of 65 species of terrestrial small mammals recorded from Tanzania's highlands, including the Eastern Arc Mountains, demonstrated pronounced geographical discontinuities in montane associations but failed to uncover a prominent vicariant role for the Makambako Gap.

High Seroprevalence of Rift Valley Fever and Evidence for Endemic Circulation in Mbeya Region, Tanzania, in a Cross-Sectional Study

BackgroundThe Rift Valley fever virus (RVFV) is an arthropod-borne phlebovirus. RVFV mostly causes outbreaks among domestic ruminants with a major economic impact. Human infections are associated with these events, with a fatality rate of 0.5–2%. Since the virus is able to use many mosquito species of temperate climates as vectors, it has a high potential to spread to outside Africa.Methodology/Principal FindingsWe conducted a stratified, cross-sectional sero-prevalence survey in 1228 participants from Mbeya region, southwestern Tanzania. Samples were selected from 17,872 persons who took part in a cohort study in 2007 and 2008. RVFV IgG status was determined by indirect immunofluorescence. Possible risk factors were analyzed using uni- and multi-variable Poisson regression models. We found a unique local maximum of RVFV IgG prevalence of 29.3% in a study site close to Lake Malawi (N = 150). The overall seroprevalence was 5.2%. Seropositivity was significantly associated with higher age, lower socio-economic status, ownership of cattle and decreased with distance to Lake Malawi. A high vegetation density, higher minimum and lower maximum temperatures were found to be associated with RVFV IgG positivity. Altitude of residence, especially on a small scale in the high-prevalence area was strongly correlated (PR 0.87 per meter, 95% CI = 0.80–0.94). Abundant surface water collections are present in the lower areas of the high-prevalence site. RVF has not been diagnosed clinically, nor an outbreak detected in the high-prevalence area.ConclusionsRVFV is probably circulating endemically in the region. The presence of cattle, dense vegetation and temperate conditions favour mosquito propagation and virus replication in the vector and seem to play major roles in virus transmission and circulation. The environmental risk-factors that we identified could serve to more exactly determine areas at risk for RVFV endemicity.