Northeastern Tanzania Research Articles

Traditional male circumcision practices among the Kurya of North-eastern Tanzania and implications for national programmes

The World Health Organisation and the Joint United Nations Programme on AIDS recommend male circumcision (MC) as an additional intervention against HIV infection. Various sub-Saharan African countries are at different stages of rolling out MC programmes. Despite initial fears, studies conducted among traditionally non-circumcising communities in Africa have shown that MC is widely accepted as a biomedical intervention. However, little is known on how traditionally circumcising communities where MC carries considerable social meaning and significance would respond to such programmes. This study was conducted among a traditionally circumcising community in Tarime district in Tanzania as part of a national situation analysis prior to initiating a national MC programme. It employed key informant interviews and focus group discussions for data collection. Results show that the Kurya ethnic group practice MC as a rite of passage from childhood to adulthood. Each clan organises its own circumcision ceremony, which takes place every even numbered years. Clan leaders and traditional circumcisers are central to its organisation. Among the Kurya, there is high regard for traditional MC as it is perceived as upholding cultural practice and identity. It also embodies notions of bravery since anaesthetics are not used. On the other hand, medical MC is not viewed as prestigious since anaesthetics are used to suppress pain. Social pressure for traditional MC is applied through ridiculing of those uncircumcised or circumcised at health facilities. In general, there are positive attitudes towards MC as it is perceived as enhancing personal hygiene and having a protective effect against sexually transmitted infections. For the success of nation-wide MC programmes, there is need to develop programmes that incorporate both clinical and sociocultural interests.

USING STRATEGIC ENTRY POINTS AND LINKED TECHNOLOGIES FOR ENHANCED UPTAKE OF IMPROVED BANANA (MUSA SPP.) GERMPLASM IN THE HUMID HIGHLANDS OF EAST AFRICA

ISHS IV International Symposium on Banana: International Conference on Banana and Plantain in Africa: Harnessing International Partnerships to Increase Research Impact USING STRATEGIC ENTRY POINTS AND LINKED TECHNOLOGIES FOR ENHANCED UPTAKE OF IMPROVED BANANA (MUSA SPP.) GERMPLASM IN THE HUMID HIGHLANDS OF EAST AFRICA

New species and new records of Mydidae from the Afrotropical and Oriental regions (Insecta, Diptera, Asiloidea)

New Mydidae species are described from the Afrotropical and Oriental regions including the first records of this family from several countries in eastern Africa (Kenya, Tanzania, and Uganda) and Mauritania in western Africa as well as Nepal and Thailand in Asia. The new species are, Leptomydinae: Leptomydas notos sp. n. (south-western India), Leptomydas rapti sp. n. (south-central Nepal), Leptomydas tigris sp. n. (north-central Thailand); Syllegomydinae: Mydaselpidini: Mydaselpis ngurumani sp. n. (south-eastern Kenya, north-eastern Tanzania), Vespiodes phaios sp. n. (south-eastern Kenya); Syllegomydinae: Syllegomydini: Syllegomydas (Notobates) astrictus sp. n. (Kenya), Syllegomydas (Notobates) heothinos sp. n. (Kenya and Uganda), Syllegomydas (Syllegomydas) elachys sp. n. (northern Zimbabwe). Syllegomydas (Syllegomydas) proximus Séguy, 1928 is recorded from western Mauritania and re-described. Syllegomydas (Notobates) dispar (Loew, 1852), which was previously listed as incertae sedis in the Afrotropical Diptera catalogue, is re-described and illustrated based on examination of the type specimens and several additional specimens from Mozambique. Cephalocera annulata Brunetti, 1912 and Syllegomydas bucciferus Séguy, 1928, described from north-eastern India and previously unplaced in the Oriental Diptera catalogue, are newly combined with Leptomydas Gerstaecker, 1868 and together with Leptomydas indianus Brunetti, 1912, also from north-eastern India, placed in Leptomydinae. Comments on the possible synonymy of the genera of Mydaselpidini are made. Illustrations and photographs are provided to support the descriptions and future identification. A provisional dichotomous key to Mydidae genera occurring in eastern Africa (Kenya, Malawi, Mozambique, Somalia, Tanzania, Uganda) and the Oriental Region is provided. Distribution, occurrence in biodiversity hotspots and high-biodiversity wilderness areas, and seasonal incidence are discussed for all species.

New Species of Aidia and Polysphaeria (Rubiaceae) from East Africa

The two species of Aidia Lour. (Rubiaceae, Gardenieae) newly described here bring this genus to three species in Tanzania and Kenya. Aidia abeidii S. E. Dawson & Gereau, from evergreen coastal forests of eastern Tanzania and Kenya, corresponds to an unnamed species mentioned in the Rubiaceae treatment for the Flora of Tropical East Africa. Aidia crassifolia S. E. Dawson & Gereau, from evergreen forests of northeastern and east-central Tanzania, is a larger tree or shrub with much larger inflorescences than the other two species of Aidia in tropical East Africa. The new species of Polysphaeria Hook. f. (Rubiaceae, Octotropideae), P. ntemii S. E. Dawson & Gereau, from evergreen forests of the East Usambara lowlands in Tanzania, corresponds to Polysphaeria sp. B of the Flora of Tropical East Africa.

A progressive declining in the burden of malaria in north-eastern Tanzania

BackgroundThe planning and assessment of malaria interventions is complicated due to fluctuations in the burden of malaria over time. Recently, it has been reported that the burden of malaria in some parts of Africa has declined. However, community-based longitudinal data are sparse and the reasons for the apparent decline are not well understood.MethodsMalaria prevalence and morbidity have been monitored in two villages in north-eastern Tanzania; a lowland village and a highland village from 2003 to 2008. Trained village health workers treated presumptive malaria with the Tanzanian first-line anti-malarial drug and collected blood smears that were examined later. The prevalence of malaria parasitaemia across years was monitored through cross-sectional surveys.ResultsThe prevalence of malaria parasitaemia in the lowland village decreased from 78.4% in 2003 to 13.0% in 2008, whereas in the highland village, the prevalence of parasitaemia dropped from 24.7% to 3.1% in the same period. Similarly, the incidence of febrile malaria episodes in the two villages dropped by almost 85% during the same period and there was a marked reduction in the number of young children who suffered from anaemia in the lowland village.ConclusionThere has been a marked decline in malaria in the study villages during the past few years. This decline is likely to be due to a combination of factors that include improved access to malaria treatment provided by the trained village helpers, protection from mosquitoes by increased availability of insecticide-impregnated bed nets and a reduced vector density. If this decline in malaria morbidity is sustained, it will have a marked effect on the disease burden in this part of Tanzania.

Biochemical basis of permethrin resistance in Anopheles arabiensis from Lower Moshi, north-eastern Tanzania.

BackgroundDevelopment of resistance to different classes of insecticides is a potential threat to malaria control. With the increasing coverage of long-lasting insecticide-treated nets in Tanzania, the continued monitoring of resistance in vector populations is crucial. It may facilitate the development of novel strategies to prevent or minimize the spread of resistance. In this study, metabolic-based mechanisms conferring permethrin (pyrethroid) resistance were investigated in Anopheles arabiensis of Lower Moshi, Kilimanjaro region of north-eastern Tanzania.MethodsWHO susceptibility test kits were used to detect resistance to permethrin in An. arabiensis. The levels and mechanisms of permethrin resistance were determined using CDC bottle bioassays and microplate (biochemical) assays. In bottle bioassays, piperonyl butoxide (PBO) and s,s,s-tributyl phosphorotrithioate (DEF) were used as synergists to inhibit mixed function oxidases and non-specific esterases respectively. Biochemical assays were carried out in individual mosquitoes to detect any increase in the activity of enzymes typically involved in insecticide metabolism (mixed function oxidases, α- and β-esterases).ResultsAnopheles arabiensis from the study area was found to be partially resistant to permethrin, giving only 87% mortality in WHO test kits. Resistance ratios at KT50 and KT95 were 4.0 and 4.3 respectively. The permethrin resistance was partially synergized by DEF and by PBO when these were mixed with permethrin in bottle bioassays and was fully synergized when DEF and PBO were used together. The levels of oxidase and β-esterase activity were significantly higher in An. arabiensis from Lower Moshi than in the laboratory susceptible strain. There was no difference in α-esterase activity between the two strains.ConclusionElevated levels of mixed function oxidases and β-esterases play a role in detoxification of permethrin in the resistant An. arabiensis population of Lower Moshi.

Lymphatic Filariasis Control in Tanzania: Effect of Repeated Mass Drug Administration with Ivermectin and Albendazole on Infection and Transmission

BackgroundIn most countries of sub-Saharan Africa the control of lymphatic filariasis (LF) is based on annual mass drug administration (MDA) with a combination of ivermectin and albendazole, in order to interrupt transmission. Here we present the first detailed study on the effect of 3 repeated MDAs with this drug combination, as implemented by the Tanzanian National Lymphatic Filariasis Elimination Programme (NLFEP).Methodology/Principal FindingsInfection and transmission was monitored during a five-year period (one pre-intervention and four post-intervention years) in a highly endemic community (Kirare village) in north-eastern Tanzania. The vectors were Anopheles gambiae, An. funestus and Cx. quinquefasciatus. After start of intervention, human microfilaraemia initially decreased rapidly and statistically significant (prevalence by 21.2% and 40.4%, and mean intensity by 48.4% and 73.7%, compared to pre-treatment values after the first and second MDA, respectively), but thereafter the effect levelled off. The initial decrease in microfilaraemia led to significant decreases in vector infection and vector infectivity rates and thus to a considerable reduction in transmission (by 74.3% and 91.3% compared to pre-treatment level after first and second MDA, respectively). However, the decrease in infection and infectivity rates subsequently also levelled off, and low-level transmission was still noted after the third MDA. The MDAs had limited effect on circulating filarial antigens and antibody response to Bm14.Conclusion/SignificanceCritical issues that may potentially explain the observed waning effect of the MDAs in the later study period include the long intervals between MDAs and a lower than optimal treatment coverage. The findings highlight the importance of ongoing surveillance for monitoring the progress of LF control programmes, and it calls for more research into the long-term effect of repeated ivermectin/albendazole MDAs (including the significance of treatment intervals and compliance), in order to optimize efforts to control LF in sub-Saharan Africa.

Identification of Hot Spots of Malaria Transmission for Targeted Malaria Control

Variation in the risk of malaria within populations is a frequently described but poorly understood phenomenon. This heterogeneity creates opportunities for targeted interventions but only if hot spots of malaria transmission can be easily identified. We determined spatial patterns in malaria transmission in a district in northeastern Tanzania, using malaria incidence data from a cohort study involving infants and household-level mosquito sampling data. The parasite prevalence rates and age-specific seroconversion rates (SCRs) of antibodies against Plasmodium falciparum antigens were determined in samples obtained from people attending health care facilities. Five clusters of higher malaria incidence were detected and interpreted as hot spots of transmission. These hot spots partially overlapped with clusters of higher mosquito exposure but could not be satisfactorily predicted by a probability model based on environmental factors. Small-scale local variation in malaria exposure was detected by parasite prevalence rates and SCR estimates for samples of health care facility attendees. SCR estimates were strongly associated with local malaria incidence rates and predicted hot spots of malaria transmission with 95% sensitivity and 85% specificity. Serological markers were able to detect spatial variation in malaria transmission at the microepidemiological level, and they have the potential to form an effective method for spatial targeting of malaria control efforts.

A package of water management practices for sustainable growth and improved production of vegetable crop in labour and water scarce Sub-Saharan Africa

Abstract A package of water management practices including pitcher irrigation method and water conserving techniques of manure application and mulching is experimented for sustainable growth and improved production of cucumber crop in Makanya village in North Eastern Tanzania. The increase in total yield due to package of water management practices is 203 per cent and water use efficiency obtained is 12.06 kg m−3. The seasonal water requirement of cucumber crop under package of water management practices ranges from 146.30 to 198.10 mm, which is on an average 4.19 times less as compared to control treatment of can irrigation. The irrigation interval in package of water management practices is 4.9 times higher than the can irrigation method. The water and labour uses are reduced by 75.9 and 73 per cent, respectively in package of water management practices. The results showed that the self-regulative nature of pitchers and moisture retention by water conserving techniques is helpful in mitigating water stress in crop root zone. The moisture retention period in soil is increased assisting reduction of labour hours required in irrigation. In local context, the water management practices included in the package are easy to understand, adopt, operate and maintain.

Yield and soil system changes from conservation tillage in dryland farming: A case study from North Eastern Tanzania

Abstract Yield levels in smallholder farming systems in semi-arid sub-Saharan Africa are generally low. Water shortage in the root zone during critical crop development stages is a fundamental constraining factor. While there is ample evidence to show that conservation tillage can promote soil health, it has recently been suggested that the main benefit in semi-arid farming systems may in fact be an in situ water harvesting effect. In this paper we present the result from an on-farm conservation tillage experiment (combining ripping with mulch and manure application) that was carried out in North Eastern Tanzania from 2005 to 2008. Special attention was given to the effects of the tested treatment on the capacity of the soil to retain moisture. The tested conservation treatment only had a clear yield increasing effect during one of the six experimental seasons (maize grain yields increased by 41%, and biomass by 65%), and this was a season that received exceptional amounts of rainfall (549 mm). While the other seasons provided mixed results, there seemed to be an increasing yield gap between the conservation tillage treatment and the control towards the end of the experiment, and cumulatively the yield increased with 17%. Regarding soil system changes, small but significant effects on chemical and microbiological properties, but not on physical properties, were observed. This raises questions about the suggested water harvesting effect and its potential to contribute to stabilized yield levels under semi-arid conditions. We conclude that, at least in a shorter time perspective, the tested type of conservation tillage seems to boost productivity during already good seasons, rather than stabilize harvests during poor rainfall seasons. Highlighting the challenges involved in upgrading these farming systems, we discuss the potential contribution of conservation tillage towards improved water availability in the crop root zone in a longer term perspective.

Acquisition of antibodies to merozoite surface protein 3 among residents of Korogwe, north eastern Tanzania

BackgroundA polymorphic malaria parasite antigen, merozoite surface protein 3 (MSP3), is among the blood stage malaria vaccine candidates. It is believed to induce immunity through cytophilic antibodies that disrupt the process of erythrocytes invasion by merozoites. This study aimed at assessing natural acquisition of antibodies to MSP3 in individuals living in an area with different malaria transmission intensity in preparation for malaria vaccine trials.MethodsThe study was conducted in individuals aged 0-19 years from villages located in lowland, intermediate and highland strata in Korogwe district, northeastern Tanzania. Blood samples from 492 study participants were collected between May and June 2006 for malaria diagnosis and immunological investigations. Reactivity of MSP3 to different types of antibodies (immunoglobulin M, G and IgG subclass 1 and 3) were analysed by Enzyme Linked ImmunoSorbent Assay (ELISA).ResultsMalaria parasite prevalence was higher in the lowland (50%) compared to the intermediate (23.1%) and highland (9.8%) strata. Immunogloblin G subclasses 1 and 3 (IgG1 & IgG3), total IgG and IgM were found to increase with increasing age. IgG3 levels were significantly higher than IgG1 (p < 0.001). Furthermore, Plasmodium falciparum infection was associated with higher IgG3 levels (p = 0.008). Adjusting by strata and age in individuals who had positive blood smears, both IgG and IgM were associated with parasite density, whereby IgG levels decreased by 0.227 (95%CI: 0.064 - 0.391; p = 0.007) while IgM levels decreased by 0.165 (95%CI: 0.044 - 0.286; p = 0.008).ConclusionIndividuals with higher levels of IgG3 might be partially protected from malaria infection. Higher levels of total IgG and IgM in highlands might be due to low exposure to malaria infection, recent infection or presence of cross-reactive antigens. Further studies of longitudinal nature are recommended. Data obtained from this study were used in selection of one village (Kwashemshi) for conducting MSP3 phase 1b malaria vaccine trial in Korogwe.

Seroprevalence of Toxoplasma gondii infection amongst residents of Tanga District in north-east Tanzania

Toxoplasmosis is a zoonotic disease, recognized as a serious public health problem worldwide. Toxoplasma gondii infection has become a major public health concern in recent years due to the ravaging HIV/AIDS pandemic. A serological survey was carried out in Tanga district of north-eastern Tanzania to assess T. gondii infection rates among occupationally-exposed groups including abattoir workers, livestock keepers, animal health workers and other groups. The survey was undertaken in November 2005 using modified Eiken latex agglutination test (LAT). Antibodies to T. gondii were detected in 91 (46%) of the 199 individuals studied. T. gondii seroprevalence was slightly higher amongst males (46.2%) than females (43.3%) although the difference was not significant (P > 0.05). Individuals, < or =20 and > or =60 years old had the highest prevalence of 60% and 61.5%, respectively. The lowest prevalence of (35.7%) was observed amongst the 50-60 years age group. The seroprevalence of toxoplasma antibodies was significantly higher amongst individuals who keep livestock (52.2%) and abattoir workers (46.3%). These results suggest exposure to T. gondii infection is present among residents of Tanga district in Tanzania and strengthen further on previous findings that consumption of raw or undercooked meat and keeping pets especially cats presents more of the risk factors than occupational groups. It also emphasizes on the necessity to create awareness of this disease, and advocate protection of risky groups from exposure to infected meat and contaminated environment.

Correction: Cost Implications of Improving Malaria Diagnosis: Findings from North-Eastern Tanzania

Correction: Cost Implications of Improving Malaria Diagnosis: Findings from North-Eastern Tanzania

Cost implications of improving malaria diagnosis: findings from north-eastern Tanzania.

BackgroundOver diagnosis of malaria contributes to improper treatment, wastage of drugs and resistance to the few available drugs. This paper attempts to estimate the rates of over diagnosis of malaria among children attending dispensaries in rural Tanzania and examines the potential cost implications of improving the quality of diagnosis.Methodology/Principal FindingsThe magnitude of over diagnosis of malaria was estimated by comparing the proportion of outpatient attendees of all ages clinically diagnosed as malaria to the proportion of attendees having a positive malaria rapid diagnostic test over a two month period. Pattern of causes of illness observed in a <2 year old cohort of children over one year was compared to the pattern of causes of illness in <5 year old children recorded in the routine health care system during the same period. Drug and diagnostic costs were modelled using local and international prices. Over diagnosis of malaria by the routine outpatient care system compared to RDT confirmed cases of malaria was highest among <5 year old children in the low transmission site (RR 17.9, 95% CI 5.8–55.3) followed by the ≥5 year age group in the lower transmission site (RR 14.0 95%CI 8.2–24.2). In the low transmission site the proportion of morbidity attributable to malaria was substantially lower in <2 year old cohort compared to children seen at routine care system. (0.08% vs 28.2%; p<0.001). A higher proportion of children were diagnosed with ARI in the <2 year old cohort compared to children seen at the routine care system ( 42% vs 26%; p<0.001). Using a RDT reduced overall drug and diagnostic costs by 10% in the high transmission site and by 15% in the low transmission site compared to total diagnostic and drug costs of treatment based on clinical judgment in routine health care system.ImplicationsThe introduction of RDTs is likely to lead to financial savings. However, improving diagnosis to one disease may lead to over diagnosis of another illness. Quality improvement is complex but introducing RDTs for the diagnosis of malaria is a good start.

Association between Mannose-Binding Lectin Polymorphisms and Wuchereria bancrofti Infection in Two Communities in North-Eastern Tanzania

The association between selected mannose-binding lectin (MBL) genotype polymorphisms and Wuchereria bancrofti infection status was assessed among individuals whose infection status had been monitored for three decades. Blood samples were collected in 2006 and examined for polymorphisms in the mbl-2 gene and for W. bancrofti-specific circulating filarial antigen (CFA) status. Logistic regression analysis showed a significant association between MBL genotype and CFA status, with low-expression MBL genotype individuals being almost three times more likely to be CFA positive than high-expression MBL genotype individuals (odds ratio [OR] = 2.90). When individuals' filarial infection (microfilaria) status in 1975 was included in the analyses, the gain of new infections between the two examination points was almost 10 times higher among individuals with low than among those with high MBL expression genotype (OR = 9.51). The susceptibility to W. bancrofti infection thus appears to be significantly affected by the MBL expression genotype of the host.

The Use of Rose Bengal Plate Test to Asses Cattle Exposure to Brucella Infection in Traditional and Smallholder Dairy Production Systems of Tanga Region of Tanzania

A cross-sectional epidemiological study was conducted to determine the seroprevalence and to identify risk factors for bovine brucellosis seropositivity in traditional and smallholder dairy cattle production systems in the Tanga region of North-eastern Tanzania. The study populations comprised 246 indigenous and 409 crossbred cattle, randomly selected from 105 smallholder dairy and 25 traditional managed herds, respectively. Individual animal and herd-level data were collected using a structured questionnaire. Serum samples were screened for Brucella antibodies using the Rose Bengal Plate Test The overall seroprevalence of Brucella antibodies in the smallholder dairy and traditional managed cattle was 4.1% and 7.3% respectively. The corresponding overall herd prevalence was 10.5% and 20% respectively. Using multivariate logistic regression analysis, closeness to stock route, access to surface drinking water and location were identified as the major risk factors for individual herd seroprevalence. Older animals (≥6 years) were associated with increased risk of sero-positivity compared to animals of age category of ≤6 years. The results showed that brucellosis is prevalent and widely distributed locally, underscoring the need for further studies including surveillance and institution of preventive and control measures particularly among female young-stock and the general public who are at high risk of contracting brucellosis.

Peoples response to diminishing natural resource base in the Pare-Usambara area, North Eastern Tanzania

In a geographical area consisting of varying potentials, naturally people will tend to exploit areas where they will gain more productivity with minimum investment. However, they will move towards the marginal areas as resources become depleted in the formally high potential areas. This study is aimed at establishing how communities have responded to diminishing resource base in the Pare-Usambara area of northeastern Tanzania. In the Pare-Usambara area, highlands formally highly endowed with natural resources are surrounded by marginally endowed lowlands on the west. The study was conducted through literature review and field data collection using PRA techniques and questionnaire survey. Findings from this study show that resources have been depleted in the highlands mainly due to population pressure, thus forcing people to move out into the marginal areas i.e. the lowlands. In both areas, land is acquired mainly through inheritance, which leads into land fragmentation, decline in land productivity, and freeze of fallow system. Increased migration into the lowlands is inserting pressure on natural resources resulting in cultivation replacing livestock keeping and land shortage as the case for the highlands. In both uplands and lowlands, more than 50% of households own not more than 2 acres of land. Key words: Natural resources, population, impacts.

Modelling the Impact of Urbanization on Groundwater Using System Dynamic Technique. A Case Study of Arusha Municipal Well Field in Northeastern Tanzania.

This paper is concerned with the impact of urbanization in aquifer well-system located in the Municipalarea of Arusha city, Tanzania. A system dynamic (SD) model was built under VENSIM PLE workbench fromtwenty-five years (1978-2003) physical and non-physical data to simulate their interactions and relations.This involved use of mathematics ideas and concepts in studying the physical and non – physical componentsseparately, and finally putting them together in new form (model) and study their relations. After model wasfound to be structurally complete and simulate properly by using the model and unit check tool of VENSIMPLE,parametric calibration of the model follows. Model output results were then compared with existing fieldconditions and information’s with the help of Excel spreadsheet. Historical data of population, rainfall, GDP,aquifer characteristics and land use was used as inputs. The model was trained for data series of 1978 to 1990and examined for data series of 1990 to 2003. Model efficiency criteria R2, suggested by Nash and Sutcliffe(1970), produced good results ranging from 0.6333 to 0.9868 during calibration and 0.9833 to 0.9985 duringverification. The model reveals that urbanization has enormous impact on population which was increasing ata rate of 4% from 1978 to 2003, which in turn caused increase in water demand for about 6% annually; as aresult aquifer well-system was overstressed due to over-pumping. Lastly a prediction of the situation for 2025was carried out in succession, and then interpretations and discussion concludes the paper.

Tectonic implications of new single zircon Pb-Pb evaporation data in the Lossogonoi and Longido ruby-districts, Mozambican metamorphic Belt of north-eastern Tanzania

Three single zircon Pb-Pb evaporation dating studies were performed on felsic orthogneisses and migmatites from the Longido and Lossogonoi ruby districts, Mozambique Belt of north-eastern Tanzania, in order to better constrain the geological setting of gemstone mineralizations. Igneous emplacement ages of protoliths ranging between 2636 and 2448 Ma document for the first time the presence of a Neoarchean to Lower Paleoproterozoic (Siderian) basement reworked in the Late Neoproterozoic Mozambique Belt of north-eastern Tanzania. This ancient crust of unknown dimension is well documented farther south, but also in south-eastern Kenya. A shearing event under high-grade amphibolite facies conditions, postdating the Pan-African metamorphic peak at 640 Ma and following nappes emplacement is demonstrated at ca. 610 Ma from metamorphic zircons of Lossogonoi district. In Lossogonoi district, ruby crystallizes during this last stage of deformation.

Parasite threshold associated with clinical malaria in areas of different transmission intensities in north eastern Tanzania

BackgroundIn Sub-Sahara Africa, malaria due to Plasmodium falciparum is the main cause of ill health. Evaluation of malaria interventions, such as drugs and vaccines depends on clinical definition of the disease, which is still a challenge due to lack of distinct malaria specific clinical features. Parasite threshold is used in definition of clinical malaria in evaluation of interventions. This however, is likely to be influenced by other factors such as transmission intensity as well as individual level of immunity against malaria.MethodsThis paper describes step function and dose response model with threshold parameter as a tool for estimation of parasite threshold for onset of malaria fever in highlands (low transmission) and lowlands (high transmission intensity) strata. These models were fitted using logistic regression stratified by strata and age groups (0-1, 2-3, 4-5, 6-9, and 10-19 years). Dose response model was further extended to fit all age groups combined in each stratum. Sub-sampling bootstrap was used to compute confidence intervals. Cross-sectional and passive case detection data from Korogwe district, north eastern Tanzania were used.ResultsDose response model was better in the estimation of parasite thresholds. Parasite thresholds (scale = log parasite/μL) were high in lowlands than in highlands. In the lowlands, children in age group 4-5 years had the highest parasite threshold (8.73) while individuals aged 10-19 years had the lowest (6.81). In the highlands, children aged 0-1 years had the highest threshold (7.12) and those aged 10-19 years had the lowest (4.62). Regression analysis with all ages combined showed similar pattern of thresholds in both strata, whereby, in the lowlands the threshold was highest in age group 2-5 years and lowest in older individuals, while in the highlands was highest in age group 0-1 and decreased with increased age. The sensitivity of parasite threshold by age group ranged from 64%-74% in the lowlands and 67%-97% in the highlands; while specificity ranged between 67%-90% in the lowlands and 37%-73% in the highlands.ConclusionDose response model with threshold parameter can be used to estimate parasite threshold associated with malaria fever onset. Parasite threshold were lower in older individuals and in low malaria transmission area.