The chosen topic should be discussed in a global context and broadlyutilise available literature (you should probably use more than 10 references APA style). The best approach for the essay would be to start with a generalised introduction and then discuss relevant information using sub-headings; should include role of agent, host and environmental factors, and potential policy responses. As part of your discussion/conclusion you should critically assess (where relevant) the literature you have used to construct your essay