Question

why malarial concepts called hypothesis

Answer 1

there are three types of hypothesis

Answer 2

A hypothesis is some kind of assumption (speculation,roughly speaking), which may be not based on experimental data. In brief, the main difference between a hypothesis and a theory is that the theory requires repeated testing. Malaria hypothesis is not a actually hypothesis, since it has been already validated. Although there are some new malaria hypothesis, which still require testing and experimental data. Probably, you are talking about one of such new hypothesis.