**Author details**

Alemayehu Abate1 and Melaku Wale2 \*

1 Ethiopian Public Health Institute, Addis Ababa University, Ethiopia

2 Department of Biology, Bahir Dar University, Ethiopia

\*Address all correspondence to: melakuwale@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
