Malaria - By the bite of female Anopheles mosquito.

Explanation: Plasmodium is the malarial parasite. Its sexual phase occurs in the female Anopheles mosquito which is its primary host. The asexual phase occurs in humans which is its secondary host. The patient displays symptoms of malarial fever after a period of 14 days from infectious bite. Body temperature may reach 106°F at the height of fever. The patient sweats a lot & the next attack takes place after 48 hours. Quinine is the oldest drug for malaria.