Equine Epizootic Lymphangitis: Validation of Histofarcin Skin Test and an in Vitro Assessment of Growth Inhibition Effects of Argemone Mexicana and Zehneria Scabra on the Mycelial Phase of Histoplasma Capsulatum var. Farciminosum
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2020-06
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Abstract
Epizootic lymphangitis is a chronic disease of equids caused by Histoplasma capsulatum var. farciminosum, resulting in remarkable loss in cart horses in Ethiopia. Absence of cheap and effective treatment and diagnostic tests are among the factors contributing to the widespread occurrence of the disease. In this study, histofarcin skin test was evaluated on 30 infected horses (15 clinically cases 15 recovered) and 15 healthy horses. Each horse was injected with 0.1mL of the histofarcin skin test antigen intradermally in the middle of the 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) caliper. The sensitivity and specificity of histofarcin skin test was 66.7 % and 100 %, respectively. In Vitro growth inhibitory effects of leaves and stem of A. mexicana and leaves of Z. scabra was evaluated. For this isolates of Histoplasma capsulatum var farciminosum were identified from clinical cases of EL in carthorses from six sites (Bishoftu, Akaki, Dukam, Asella, Shashemene and Gindhiir). Two-fold serial dilutions of the methanol extracts of the plants were prepared and assessed. Hcf culture media without antifungal agent used as negative control and media with ketoconazole taken as positive control. The result showed that A. mexicana and Z. scabra had inhibited Hcf growth at concentration 10mg/ml up to 2.5mg/ml. 2.5mg/ml was the minimum inhibitory concentration of the two plants. In conclusion, this study demonstrated that histofarcin skin test is a promising diagnostic tool for screening of equine histoplasmosis. Besides, the methanol extracts of A. mexicana and Z. scabra showed good in vitro growth inhibitory activity against the mycelial phase of Histoplasma capsulatum var farciminosum.
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Epizootic lymphangitis, Equines, Ethiopia, H. capsulatum var. farsiminosum, Medicinal Plants, Histofarcin Skin Test