Spatial Heterogeneity Association of HIV Incidence with Socio-economic Factors in Zimbabwe

This study examined the spatial heterogeneity association of HIV incidence and socio-economic factors including poverty severity index,permanently employed females and males, unemployed females, percentage of poor households i.e., poverty prevalence, night lights index, literacy rate,household food security, and Gini index at district level in Zimbabwe.A mix of spatial analysis methods including Poisson model based on original log likelihood ratios (LLR), global Moran’s I, local indicator of spatial association - LISA were employed to determine the HIV hotspots.Geographically Weighted Poisson Regression (GWPR) and semi-parametric GWPR (s-GWPR) were used to determine the spatial association between HIV incidence and socio-economic factors. HIV incidence (number of cases per 1000) ranged from 0.6 (Buhera district) to 13.30 (Mangwe district). Spatial clustering of HIV incidence was observed (Global Moran’s I = - 0.150; Z score 3.038; p-value 0.002). Significant clusters of HIV were observed at district level. HIV incidence and its association with socioeconomic factors varied across the districts except percentage of females unemployed. Intervention programmes to reduce HIV incidence should address the identified socio-economic factors at district level

Predicted changes in habitat suitability for human schistosomiasis intermediate host snails for modelled future climatic conditions in KwaZulu-Natal, South Africa

Introduction: Climate change alters environmental and climatic conditions, leading to expansion or contraction and possible shifts in the geographical distribution of vectors that transmit diseases. Bulinus globosus and Biomphalaria pfeifferi are the intermediate host snails for human schistosomiasis in KwaZulu-Natal (KZN) province, South Africa.Methods: Using the Maximum entropy (MaxEnt) model, we modelled the current and future distribution of human schistosomiasis intermediate host snails in KZN using two representation concentration pathways (RCP4.5 and RCP8.5) for the year 2085. Thirteen and ten bioclimatic variables from AFRICLIM were used to model the habitat suitability for B. globosus and B. pfeifferi, respectively. The Jack-knife test was used to evaluate the importance of each bioclimatic variable.Results: Mean temperature warmest quarter (BIO10, 37.6%), the number of dry months (dm, 32.6%), mean diurnal range in temperature (BIO2, 10.8%), isothermality (BIO3, 6.7%) were identified as the top four bioclimatic variables with significant contribution to the model for predicting the habitat suitability for B. globosus. Annual moisture index (mi, 34%), mean temperature warmest quarter (BIO10, 21.5%), isothermality (BIO3, 20.5%), and number of dry months (dm, 7%) were identified as the four important variables for the habitat suitability of B. pfeifferi. Area under the curve for the receiving operating characteristics was used to evaluate the performance of the model. The MaxEnt model obtained high AUC values of 0.791 and 0.896 for B. globosus and B. pfeifferi, respectively. Possible changes in the habitat suitability for B. globosus and B. pfeifferi were observed in the maps developed, indicating shrinkage and shifts in the habitat suitability of B. pfeifferi as 65.1% and 59.7% of the current suitable habitats may become unsuitable in the future under RCP4.5 and RCP8.5 climate scenarios. Conversely, an expansion in suitable habitats for B. globosus was predicted to be 32.4% and 69.3% under RCP4.5 and RCP8.5 climate scenarios, with some currently unsuitable habitats becoming suitable in the future.Discussion: These habitat suitability predictions for human schistosomiasis intermediate host snails in KZN can be used as a reference for implementing long-term effective preventive and control strategies for schistosomiasis

A composite inherent resilience index for Zimbabwe:An adaptation of the disaster resilience of place model

Building resilience to disasters has become a strategic goal of many risk reduction programs across the globe. This is because resilience ensures that communities develop capacities which prevent or minimise loses to disasters. In view of this, there is need to develop a baseline that tracks changes in resilience through time. This study responded to this gap in Zimbabwe by developing composite resilience indices (CRI) using 26 variables that reflected 5 subdomains of resilience: community capital, economic, infrastructure, social and health. The CRI were then used to map the spatial variation of resilience across 91 districts. The results show that the majority of the districts with below moderate resilience are mainly rural and marginalised, while the most resilient districts emerged in urban areas where service provision and infrastructure are better developed. These findings were further subjected to factor analyses which deconstructed the overall CRI and identified six latent factors behind resilience: infrastructure, health, household head, and income, access to maize and fortified food. These factors were mapped in a GIS environment to show their geographic variation in the country. Furthermore, Moran's Index and the Getis Ord Gi* statistical tests were applied to determine clusters of resilience across space. Results confirmed the spatial clustering of CRI. The results are therefore, useful in planning mitigation, response and preparedness measures across the country

Perceived impacts of climate variability and change:an exploration of farmers’ adaptation strategies in Zimbabwe’s intensive farming region

Climate variability and change (CVC) affect many economic sectors including agriculture. In order to alleviate the negative impact of CVC on food production, farmers must adopt a range of strategies. However, the strategies will be less effective if farmers’ perceptions on CVC are not considered. This study therefore, examined the perceptions of commercial farmers on CVC and their adaptation strategies to the perceived impacts. It used a cross-sectional survey involving 365 farmers in the intensive farming region of Zimbabwe. Results showed that farmers’ perceptions on increasing temperatures and decreasing rainfall amounts were cognate with climate data from the meteorological office. The findings also demonstrated that farmers were well aware of the CVC impacts on their livelihoods. These include increases in the frequency and severity of drought, and a shortening of the length of the rainy season. However, the most significant changes were observed among the natural and economic capitals including soil salinization, reduction in grazing pastures, fodder and crop yields in addition to increases in food prices. In response to the perceived impacts of local CVC, the farmers were adopting crop and land use management strategies that include planting rotation, cultivating short-season varieties and drought tolerant crops, crop and farm diversification, intensified irrigation, agroforestry, soil moisture conservation and mixed farming. The study concludes that farmers are active observers of local CVC. Therefore, they should modify their agricultural calendar and diversify their farming systems so as to better meet current and future risks from CVC

Data and tools to integrate climate and environmental information into public health

Background During the last 30 years, the development of geographical information systems and satellites for Earth observation has made important progress in the monitoring of the weather, climate, environmental and anthropogenic factors that influence the reduction or the reemergence of vector-borne diseases. Analyses resulting from the combination of geographical information systems (GIS) and remote sensing have improved knowledge of climatic, environmental, and biodiversity factors influencing vector-borne diseases (VBDs) such as malaria, visceral leishmaniasis, dengue, Rift Valley fever, schistosomiasis, Chagas disease and leptospirosis. These knowledge and products developed using remotely sensed data helped and continue to help decision makers to better allocate limited resources in the fight against VBDs. Main body Because VBDs are linked to climate and environment, we present here our experience during the last four years working with the projects under the, World Health Organization (WHO)/ The Special Programme for Research and Training in Tropical Diseases (TDR)-International Development Research Centre (IDRC) Research Initiative on VBDs and Climate Change to integrate climate and environmental information into research and decision-making processes. The following sections present the methodology we have developed, which uses remote sensing to monitor climate variability, environmental conditions, and their impacts on the dynamics of infectious diseases. We then show how remotely sensed data can be accessed and evaluated and how they can be integrated into research and decision-making processes for mapping risks, and creating Early Warning Systems, using two examples from the WHO TDR projects based on schistosomiasis analysis in South Africa and Trypanosomiasis in Tanzania. Conclusions The tools presented in this article have been successfully used by the projects under the WHO/TDR-IDRC Research Initiative on VBDs and Climate Change. Combined with capacity building, they are an important piece of work which can significantly contribute to the goals of WHO Global Vector Control Response and to the Sustainable Development Goals especially those on health and climate action

Modelling the spatial and seasonal distribution of suitable habitats of schistosomiasis intermediate host snails using Maxent in Ndumo area, KwaZulu-Natal Province, South Africa

Abstract Background Schistosomiasis is a snail-borne disease endemic in sub-Saharan Africa transmitted by freshwater snails. The distribution of schistosomiasis coincides with that of the intermediate hosts as determined by climatic and environmental factors. The aim of this paper was to model the spatial and seasonal distribution of suitable habitats for Bulinus globosus and Biomphalaria pfeifferi snail species (intermediate hosts for Schistosoma haematobium and Schistosoma mansoni, respectively) in the Ndumo area of uMkhanyakude district, South Africa. Methods Maximum Entropy (Maxent) modelling technique was used to predict the distribution of suitable habitats for B. globosus and B. pfeifferi using presence-only datasets with ≥ 5 and ≤ 12 sampling points in different seasons. Precipitation, maximum and minimum temperatures, Normalised Difference Vegetation Index (NDVI), Normalised Difference Water Index (NDWI), pH, slope and Enhanced Vegetation Index (EVI) were the background variables in the Maxent models. The models were validated using the area under the curve (AUC) and omission rate. Results The predicted suitable habitats for intermediate snail hosts varied with seasons. The AUC for models in all seasons ranged from 0.71 to 1 and the prediction rates were between 0.8 and 0.9. Although B. globosus was found at more localities in the Ndumo area, there was also evidence of cohabiting with B. pfiefferi at some of the locations. NDWI had significant contribution to the models in all seasons. Conclusion The Maxent model is robust in snail habitat suitability modelling even with small dataset of presence-only sampling sites. Application of the methods and design used in this study may be useful in developing a control and management programme for schistosomiasis in the Ndumo area

Efficacy of praziquantel on Schistosoma haematobium and re-infection rates among school-going children in the Ndumo area of uMkhanyakude district, KwaZulu-Natal, South Africa

Abstract Background Despite its low cure rates and possible resistance, praziquantel (PZQ) is the only drug available for schistosomiasis treatment. Hence, monitoring its efficacy is crucial. This study assessed the efficacy of PZQ, determined re-infection and incidence rates of Schistosoma haematobium infection among school-going children in the Ndumo area, KwaZulu-Natal. Methods A cohort of 320 school-going children (10 – 15 years) in 10 primary schools was screened for S. haematobium infection using the filtration technique. Infected children were treated at different times and hence were divided into two sub-cohorts; A1 and A2. Non-infected children constituted the sub-cohort B. Children who continued excreting viable eggs 4 weeks post-treatment received a second dose of PZQ. Re-infection rates were determined in sub-cohort A1 and A2 at 28 and 20 weeks post-treatment, respectively. Cure rates (CR) and egg reduction rates (ERR) were calculated. Incidence rate was assessed 28 weeks post baseline survey using children that were negative for schistosome eggs at that survey. Analysis of data was done using the Chi square and the Wilcoxon rank test. A 95% confidence interval with a P-value < 0.05 determined significance. Results At baseline, 120 (37.5%) of the 320 study participants were found infected with Schistosoma haematobium. Heavy infections accounted for 36.7%. The calculated cure rates were 88.07% and 82.92% for females and males, respectively. Egg Reduction Rates of 80% and 64% for females and males were observed 4 weeks after the initial treatment. After the second treatment, CR was 100% in females and 50% in males with an ERR of 100% in females and 70% in males. At 20 and 28 weeks post treatment, reinfection rates of 8.03% and 8.00% were observed, respectively, giving an overall rate of 8.1%. An incidence rate of 4.1% was observed 28 weeks after the baseline screening. Conclusions The study indicated high CR while the ERR was low suggesting a reduced PZQ efficacy. The efficacy improved among females after the second dose. Re-infection rates at 20 and 28 weeks post-treatment were low. The study also indicated a low incidence rate for the 28 weeks period

Species Diversity, Distribution, and Abundance of Freshwater Snails in KwaZulu-Natal, South Africa

Disease distribution is correlated to the distribution of the freshwater snails which in turn is influenced by the physicochemical status of the habitats. This study aimed to evaluate freshwater snail species diversity, abundance, and distribution in KwaZulu-Natal (KZN) province, South Africa, between December 2020 to February 2021. A total of 4576 freshwater snails consisting of 8 species were collected from 127 sites in 11 districts. Tarebia granifera snails were the most abundant (n = 2201), while bivalves (n = 95) were the least abundant. The highest and least Shannon&ndash;Weiner Simpson&rsquo;s diversity indices were recorded in Ugu and iLembe districts, respectively. A negative relationship was observed between rainfall, Bulinus tropicus, Lymnaea natalensis, bivalves, and Physa acuta, while temperature had a positive relationship with B. globosus, B. pfeifferi, and T. granifera. A positive relationship was observed between B. globosus and B. pfeifferi (r = 0.713, p &lt; 0.05). Snail presence constitutes potential health and economic risks to humans and animals in contact with the waterbody. Hence, our study described the current distribution, abundance, and species diversity of freshwater snails in the KZN province with insights into the possibilities of snail-based biological control for schistosomes intermediate host snails

Application of geo-spatial technology in schistosomiasis modelling in Africa: a review

Schistosomiasis continues to impact socio-economic development negatively in sub-Saharan Africa. The advent of spatial technologies, including geographic information systems (GIS), Earth observation (EO) and global positioning systems (GPS) assist modelling efforts. However, there is increasing concern regarding the accuracy and precision of the current spatial models. This paper reviews the literature regarding the progress and challenges in the development and utilization of spatial technology with special reference to predictive models for schistosomiasis in Africa. Peer-reviewed papers identified through a PubMed search using the following keywords: geo-spatial analysis OR remote sensing OR modelling OR earth observation OR geographic information systems OR prediction OR mapping AND schistosomiasis AND Africa were used. Statistical uncertainty, low spatial and temporal resolution satellite data and poor validation were identified as some of the factors that compromise the precision and accuracy of the existing predictive models. The need for high spatial resolution of remote sensing data in conjunction with ancillary data viz. ground-measured climatic and environmental information, local presence/absence intermediate host snail surveys as well as prevalence and intensity of human infection for model calibration and validation are discussed. The importance of a multidisciplinary approach in developing robust, spatial data capturing, modelling techniques and products applicable in epidemiology is highlighted

Effects of temperature on the life history traits of intermediate host snails of fascioliasis: A systematic review.

BackgroundThe impact of climate change has led to variations in various biological processes, leading to altered transmission dynamics of infectious diseases, including snail-borne diseases (SBDs). Fascioliasis is one of the neglected zoonotic tropical snail-borne diseases caused by the trematode of the genus Fasciola. This review focused on laboratory experimental and model studies that evaluate the potential effect of temperature change on the ecology and biology of the intermediate host snails (IHS) of Fasciola.MethodsA literature search was conducted on Google Scholar, EBSCOhost, and PubMed databases using predefined medical subject heading terms, Boolean operators, and truncation symbols in combination with direct keywords: Fasciolosis AND Temperature, Lymnaea OR Austropeplea OR Radix OR Galba OR Fossaria OR Pseudosuccinea AND growth, fecundity, AND survival at the global scale. Other search terms used were (Fascioliasis AND Temperature), (Lymnaea AND Temperature), (Austropeplea AND Temperature), (Fossaria AND Temperature), (Galba AND Temperature), (Pseudosuccinea AND Temperature), and (Radix AND Temperature).ResultsThe final synthesis included thirty-five published articles. The studies reviewed indicated that temperature rise may alter the distribution, and optimal conditions for breeding, growth, and survival of IHS, ultimately resulting in changing the transmission dynamics of fascioliasis. The literature also confirmed that the life history traits of IHS and their interaction with the liver fluke parasites are driven by temperature, and hence climate change may have profound outcomes on the population size of snails, parasite density, and disease epidemiology.ConclusionWe concluded that understanding the impact of temperature on the growth, fecundity, and survival of IHS may broaden our knowledge of the possible effects of climate change and hence inform fascioliasis control programs