⟩ This July a group of 30 volunteers went to Kenya to help build a school and all of them took prophylaxis to prevent malaria. They claim that they took the medication as prescribed 2 weeks before, during their stay, and for 4 weeks after returning home. In October, one person developed malaria and by April of this year, 9 of the 30 volunteers had been treated for malaria. Which of the following is the least likely explanation for this apparent failure of prevention?
* A. This is most likely P. vivax or ovale which have a latent stage in their life cycle that persists in the liver and can result in disease weeks to months after exposure
* B. Most of the medication used for prophylaxis of malaria acts only on the red blood cell stage of the infection
* C. This could be P. malariae which is known to result in a more chronic malaria state
* D. This could be P. falciparum that was not completely treated by the prophylaxis
* E. The nine who got malaria must not have taken the medication as prescribed since this should have prevented malaria
Correct Answer: E
