Where can I find information on the ratio of malaria cases treated annually globally or per country?
A great resource for information on malaria is the World Health Organisation (WHO). They publish an annual malaria report which also includes lots of statistics about numbers of cases, numbers treated, and numbers of deaths from malaria. Some of the data is even available at the country level, I believe. You can download these reports, and also find out a lot more information about malaria, at the World Health Organisation malaria page.