Browsing by Author "Magana, Adiel M."

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Modeling HIV/AIDS Co Infection with Malaria and Tuberculosis: The role of treatment and counseling
(2018-05) Okong’o, Mark; Lawi, George; Musundi, Sammy; Magana, Adiel M.
HIV/AIDS remains one of the leading causes of death in the world with its effects most devastating in Sub Saharan Africa due to its dual infection with opportunistic infections especially malaria and tuberculosis. This study presents a co infection deterministic model defined by a system of ordinary differential equations for HIV/AIDS, malaria and tuberculosis. The HIV/AIDS only model is analyzed to determine the conditions for the stability of the equilibria points and assess the role of treatment and counseling in controlling the spread of the infections. This study shows that effective counseling reduces the value of the reproduction number for HIV/AIDS (RH) to less than unity eliminating the HIV/AIDS problem. Numerical simulations show that applying anti-retroviral treatment (ARV’S) without effective counseling increases the value of RH, worsening the HIV/AIDS problem, however ARV treatment coupled with effective counseling reduces the value of RH to a level below one eliminating the disease. The study further shows that when the proportion of those receiving ARV treatment without effective counseling increases, the value of RH also increases to a level above one, however effective counseling maintains the value of RH below unity therefore strategies for the control of HIV/AIDS should emphasize counseling and not only treatment.
Variation in Seagrass Carbon Stocks Between Tropical Estuarine and Marine Mangrove-Fringed Creeks
(Frontiers in Marine Science, 2020) Juma, Gabriel A.; Magana, Adiel M.; Michael, Githaiga N.; Kairo, James G.
Seagrass and associated blue carbon ecosystems are important carbon sinks, and hence understanding their spatial and temporal variability is vital in appreciating their potential roles in climate change mitigation and adaptation. The Indo-Pacific region has the highest seagrass biodiversity, yet little focus has been made to compare seagrass habitat extent and carbon dynamics with their temperate counterparts. The present study assessed habitat characteristics and seagrass species distribution, diversity, and carbon storage in Eastern (marine) and Western (estuarine) mangrove-fringed creeks of Gazi Bay, Kenya. Data on species composition, canopy cover, biomass, and sediment organic carbon were collected in 80 plots of 0.25 × 0.25 m laid along transects established perpendicular to the waterline. Five species formation, viz., Thalassia hemprichii, Cymodocea rotundata, Cymodocea serrulata, Enhalus acoroides, and Thalassidendron ciliatum, were encountered as either single or mixed stands. There was a significant difference in total seagrass biomass between creeks (p < 0.01), with the Eastern creek recording a mean of 10.2 ± 0.6 Mg C ha–1 while the Western creek recording 4.3 ± 0.3 Mg C ha–1. In addition, sediment carbon to 1-m depth varied significantly (p < 0.01) between species in the two creeks and ranged from 98 to 302 Mg C ha–1, with the Eastern and Western creeks recording means of 258 ± 90 and 107 ± 21 Mg C ha–1, respectively. The total carbon stock from 50 ha of seagrasses in the Eastern creek was 13,420 Mg C, whereas in the 70 ha of the Western creek it was 7,769 Mg C. The study shows that seagrass community attributes such as species composition and productivity can vary dramatically over a small spatial extent due to differences in biophysical conditions and caution estimations of site-specific carbon stocks using generalized global values.