Not only could they be added, but they have been. See for example this article about a program in Vietnam where they have been used to control the mosquito resp

Not only could they be added, but they have been. See for example this article about a program in Vietnam where they have been used to control the mosquito responsible for Dengue fever. http://www.ajtmh.org/cgi/content/full/72/1/67 http://www.ajtmh.org/cgi/content/full/72/1/67 There are many more examples on Google...