Assessment of Histofarcin Skin Test and in vitro Evaluation of Effects of Selected Medicinal Plants on the Growth Inhibition of Mycelial form of Histoplasma capsulatum var. farciminosum
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Date
2019-06
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Abstract
Epizootic lymphangitis is one of the neglected infectious diseases of equines causing remarkable loss in cart horses in Ethiopia. Lack of effective treatment and appropriate diagnostic tools for screening of the disease contributed to its continued occurrence. In this study, histofarcin skin test was developed and evaluated on 10 clinically infected, 10 healthy and 10 recovered horses. The histofarcin antigen used was prepared from field isolates of Histoplasma capsulatum var farciminosum. The concentration of the antigen was determined using bicinchonic acid protein assay method (Pierce, BCTTM protein assay kit number 23225) at Black lion teaching hospital, Addis Ababa University. Each horse was injected with 0.1mL of the antigen intradermally in the middle of their neck. The thickness of the skin was measured before injection and 24, 48 and 72 hrs post injection using Bar knight Mc Lintock (McLK- P0005) calliper. The sensitivity and specificity the skin test was 80 % and 70%, respectively. In addition, the in vitro growth inhibitory effects of the root of Curcuma longa, berry of Phytolacca dodecandra and leaf of Datura Stramonium were evaluated. For this isolates of Histoplasma capsulatum var farciminosum were identified from four sites (Bishoftu, Akaki, Holota, Mojo). Two fold serial dilutions of the methanol extracts of the three plants were prepared and assessed. The minimum inhibition concentration of the plants was determined by agar dilution assay at Aklilu Lema Institute of Pathobiology, Addis Ababa University. A culture media with no antifungal agent and media containing ketoconazole served as negative and positive control, respectively. The results showed that Curcuma longa and Phytolacca dodecandra had inhibitory effect at ranges of concentrations. Curcuma longa had lower minimum inhibitory concentrations (0.07mg/mL) than Phytolacca dodecandra (0.156mg/mL) where as Datura stramonium showed no inhibitory effect on Histoplasma capsulatum var farciminosum. In conclusion, this study demonstrated that histofarcin skin test is a promising diagnosing tool for screening of equine histoplasmosis. Besides, the methanol extracts of Curcuma longa and Phytolacca dodecandra showed strong in vitro growth inhibitory activity against Histoplasma capsulatum var farciminosum.
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Msc Thesis
Keywords
Cart horses, Epizootic lymphangitis, Histofarcin skin test