Wolbachia endobacteria depletion by doxycycline as antifilarial therapy has macrofilaricidal activity in onchocerciasis: a randomized placebo-controlled study

In a randomized, placebo-controlled trial in Ghana, 67 onchocerciasis patients received 200-mg/day doxycycline for 4–6 weeks, followed by ivermectin (IVM) after 6 months. After 6–27 months, efficacy was evaluated by onchocercoma histology, PCR and microfilariae determination. Administration of doxycycline resulted in endobacteria depletion and female worm sterilization. The 6-week treatment was macrofilaricidal, with >60% of the female worms found dead, despite the presence of new, Wolbachia-containing worms acquired after the administration of doxycycline. Doxycycline may be developed as second-line drug for onchocerciasis, to be administered in areas without transmission, in foci with IVM resistance and in areas with Loa co-infections

Above-ground carbon stocks, species diversity and fire dynamics in the Bateke Plateau

Savannas are heterogeneous systems characterised by a high spatial and temporal variation in ecosystem structure. Savannas dominate the tropics, with important ecological functions, and play a prominent role in the global carbon cycle, in particular responsible for much of its inter-annual variability. They are shaped by resource availability, soil characteristics and disturbance events, particularly fire. Understanding and predicting the demographic structure and woody cover of savannas remains a challenge, as it is currently poorly understood due to the complex interactions and processes that determine them. A predictive understanding of savanna ecosystems is critical in the context of land use management and global change. Fire is an essential ecological disturbance in savannas, and forest-savanna mosaics are maintained by fire-mediated positive feedbacks. Over half of the world’s savannas are found in Africa, and over a quarter Africa’s surface burns every year, with fires occurring principally in the savanna biome. These have strong environmental and social impacts. Most fires in Africa are anthropogenic and occur during the late dry season, but their dynamics and effects remain understudied. The main objective of this research is to understand the floristic composition, carbon storage, woody cover and fire regime of the mesic savannas of the Bateke Plateau. The Bateke Plateau is savanna-forest mosaic ecosystem, situated mainly in the Republic of Congo, with sandy Kalahari soils and enough precipitation for potential forest establishment (1600 mm/yr). Despite occupying 89,800 km2, its ecology and ecosystem functions are poorly understood. This study combines two approaches: firstly experimental, setting up long term field experiments where the fire regime is manipulated, and then observational, using remote sensing to estimate the carbon storage and study the past history of the fire regime in the region. I established four large (25 ha) plots at two savanna sites, measured their carbon stocks, spatial structure and floristic composition, and applied different annual fire treatments (early and late dry season burns). These treatments were applied annually during 3 years (2015, 2016 and 2017), and the plots were re-measured every year to estimate tree demographic rates and the identification of the key processes that impact them, including fire and competition. Field data were combined with satellite radar data from ALOS PALSAR, and the fire products of the MODIS satellites, to estimate carbon stocks and fire regimes for the entire Bateke Plateau. I also analyse the underlying biophysical and anthropogenic processes that influence the patterns in Above-Ground Woody Biomass (AGWB) and their spatial variability in the Bateke landscape. The total plant carbon stocks (above-ground and below-ground) were low, averaging only 6.5 ± 0.3 MgC/ha, with grass representing over half the biomass. Soil organic matter dominate the ecosystem carbon stocks, with 16.7 ± 0.9 Mg/ha found in the top 20 cm alone. We identified 49 plant species (4 trees, 13 shrubs, 4 sedges, 17 forbs and 11 grass species), with a tree hyperdominance of Hymenocardia acida, and a richer herbaceous species composition. These savannas showed evidence of tree clustering, and also indications of tree-tree competition. Trees had low growth rates (averaging 1.21 mm/yr), and mortality was relatively low (3.24 %/yr) across all plots. The experiment showed that late dry season fires significantly reduced tree growth compared to early dry season fires, but also reduced stem mortality rates. Results show that these mesic savannas had very low tree biomass, with tree cover held far below its climate potential closed-canopy maximum, likely due to nutrient poor sandy soils and frequent fires. Results from the remote sensing analysis indicated that multiple explanatory variables had a significant effect on AGWB in the Bateke Plateau. Overall, the frequency of fire had the largest impact on AGWB (with higher fire frequency resulting in lower AGWB), with sand content the next most important explanatory variable (with more sand reducing AGWB). Fires in the Bateke are very frequent, and show high seasonality. The proportion of fires that occurred in the late dry season, though smaller predictor, was also more important than other factors (including soil carbon proportion, whether or not the savanna area was in a protected area, annual rainfall, or distance to the nearest town, river or road), with a larger proportion of late dry season fires associated with a small increase in AGWB. The results give pointers for management of the savannas of the Bateke Plateau, as well as improving our understanding of vegetation dynamics in this understudied ecosystem and help orient policy and conservation

Hyperreactive onchocerciasis is characterized by a combination of Th17-Th2 immune responses and reduced regulatory T cells

<div><p>Clinical manifestations in onchocerciasis range from generalized onchocerciasis (GEO) to the rare but severe hyperreactive (HO)/sowda form. Since disease pathogenesis is associated with host inflammatory reactions, we investigated whether Th17 responses could be related to aggravated pathology in HO. Using flow cytometry, filarial-specific cytokine responses and PCR arrays, we compared the immune cell profiles, including Th subsets, in individuals presenting the two polar forms of infection and endemic normals (EN). In addition to elevated frequencies of memory CD4⁺ T cells, individuals with HO showed accentuated Th17 and Th2 profiles but decreased CD4⁺CD25^hiFoxp3⁺ regulatory T cells. These profiles included increased IL-17A⁺, IL-4⁺, RORC2⁺ and GATA3⁺CD4⁺ T cell populations. Flow cytometry data was further confirmed using a PCR array since Th17-related genes (IL-17 family members, IL-6, IL-1β and IL-22) and Th2-related (IL-4, IL-13, STAT6) genes were all significantly up-regulated in HO individuals. In addition, stronger <i>Onchocerca volvulus</i>-specific Th2 responses, especially IL-13, were observed <i>in vitro</i> in hyperreactive individuals when compared to GEO or EN groups. This study provides initial evidence that elevated frequencies of Th17 and Th2 cells form part of the immune network instigating the development of severe onchocerciasis.</p></div

Data from: The mesic savannas of the Bateke Plateau: carbon stocks and floristic composition

The Bateke Plateau in the Republic of Congo is one of the last frontiers for ecology, with little known about its floristics and physiognomy. Despite occupying 89,800 km2 and its importance for local livelihoods, its ecology and ecosystem functions are poorly understood. Situated on Kalahari sands, the Bateke has a complex evolutionary history, mainly isolated from other savannas for much of its past, with currently unresolved ecological implications. Here we assess the biomass and floristic diversity of this savanna. We established four 25 ha permanent sample plots at two savanna sites, inventoried all trees, and assessed shrub, forb and grass species and biomass, and characterised the soils. Total plant carbon stocks (aboveground and belowground) were only 6.5 ± 0.3 MgC/ha, despite precipitation of 1600 mm/yr. Over half the biomass was grass, with the remainder divided between trees and shrubs. The carbon stock of the system is mostly contained in the top layer of the soil (16.7 ± 0.9 MgC/ha in 0-20 cm depth). We identified 49 plant species (4 trees, 13 shrubs, 4 sedges, 17 forbs and 11 grass species), with an average species richness of 23 per plot. There is tree hyperdominance of Hymenocardia acida (Phyllanthaceae), and a richer herbaceous species composition dominated by Loudetia simplex and Hyparrhenia diplandra. The low carbon stocks and tree biodiversity, compared to other African savannas, is surprising considering the high rainfall. We speculate it is due to low nutrient soils, high fire frequency and the effect of a temporally variable and restricted connection to the main southern African savanna complex

Nieto_Quintano_et_at_DATAsubplots

Species composition data (presence/absence) for 1-ha subplots, situated inside 4 plots of 25-ha (plots LWR1 and LWR2 in Lefini Reserve and plots LLR1 and LLR2 in Lesio Louna Reserve), located in the Bateke Plateau (Republic of Congo

Nieto_Quintano_et_al_DATASubplots_Grass_Saplings

Subplot level grass data (Above ground Carbon stocks) for 4 25-ha plots in the Bateke Plateau (plots LWR1 and LWR2 in Lefini Reserve and plots LLR1 and LLR2 in Lesio Louna Reserve), and Subplot level saplings/shrubs data (Above ground Carbon stocks) for 4 25-ha plots in the Bateke Plateau (plots LWR1 and LWR2 in Lefini Reserve and plots LLR1 and LLR2 in Lesio Louna Reserve)

Nieto_Quintano_et_at_DATAsubplots

Species composition data (presence/absence) for 1-ha subplots, situated inside 4 plots of 25-ha (plots LWR1 and LWR2 in Lefini Reserve and plots LLR1 and LLR2 in Lesio Louna Reserve), located in the Bateke Plateau (Republic of Congo

Wolbachia endobacteria depletion by doxycycline as antifilarial therapy is macrofilaridical in onchocerciasis

In Tanzania malaria is the leading cause of morbidity and mortality, especially in children under 5 years. The disease ranks number one in both outpatient and inpatient statistics. The socio-economic impact of malaria is so high that it contributes highly to poverty and underdevelopment. Efforts made during the past century to combat and control malaria have not been successful. The prospects of achieving the Abuja declaration targets are uncertain within the remaining period of time. Currently, the Ministry of Health through a 5-year strategic plan advocates four main approaches in the fight against the disease. These include improved case management, vector control using insecticide treated mosquito nets, prevention and control of malaria in pregnancy and epidemic preparedness, prevention and control. However, these strategies face various challenges including inadequate human, financial, and material resources; inefficiency in the healthcare system that is incapable of providing quality health services and access to prompt diagnosis and treatment; lack of an effective disease surveillance system; and an inefficient health education communication mechanism. Tanzania is at the crossroads and is challenged with the need to introduce a new antimalarial treatment regimen and the reintroduction of DDT for indoor residual spray. Unless malaria control strategy adopts an integrated approach its success is far from being realized. This article reviews the current malaria control strategies and its challenges in Tanzania and proposes new strategies. Copyrigh