Which scientist and physician is credited with discovering the protozoan germs that cause malaria in humans?

Introduction / Context:
Malaria is a serious infectious disease transmitted by mosquitoes and caused by protozoan parasites of the genus Plasmodium. Identifying the actual germs that cause malaria was a major milestone in medical science. This question asks which scientist first discovered these malaria parasites in human blood.

Given Data / Assumptions:

• The focus is on the germs that cause malaria, not simply on mosquitoes or treatment.
• The pathogens are protozoa visible under a microscope in blood smears.
• The options list several important microbiologists and physicians.
• We assume awareness that malaria is not caused by bacteria or viruses.

Concept / Approach:
Charles Louis Alphonse Laveran, a French army surgeon, observed parasites in the blood of patients suffering from malaria in Algeria in the nineteenth century. He saw pigmented bodies and later identified them as the causative organisms. This work earned him a Nobel Prize and established the protozoan nature of malaria. Therefore, he is credited with discovering the malaria causing germs.

Step-by-Step Solution:
Step 1: Remember that malaria is caused by protozoa, not bacteria or viruses. Step 2: Recall that Laveran was the first to see these protozoan parasites in human blood and connect them with malaria symptoms. Step 3: Compare with Ivanovsky and Beijerinck, who studied viruses in plants, and Christiaan Barnard, who performed heart transplants. Step 4: Conclude that Charles Louis Alphonse Laveran is the correct answer.

Verification / Alternative check:
Medical history timelines list Laveran as the discoverer of the malaria parasite. Ross later worked on the mosquito transmission cycle, but the first demonstration of parasites in human blood is attributed to Laveran. Because the question specifically mentions malaria causing germs, not its transmission, this distinction confirms that Laveran is the correct choice.

Why Other Options Are Wrong:

• Christiaan Barnard: Famous for performing the first successful human heart transplant, not for malaria research.
• Dmitri Ivanovsky: Pioneer in virology, who studied tobacco mosaic disease in plants.
• Martinus Willem Beijerinck: Also an early virologist, who proposed the concept of viruses, not malaria protozoa.
• Louis Pasteur: A major figure in microbiology and vaccination, but not the first to identify malaria parasites.

Common Pitfalls:
Students sometimes choose Louis Pasteur because they associate him with many discoveries in microbiology, or they confuse malaria parasites with bacteria and think of Koch or Pasteur. To avoid this, remember that malaria involves a protozoan parasite and that Laveran is the name linked directly with this discovery in standard general knowledge references.

Final Answer:
The malaria causing protozoan germs in human blood were discovered by Charles Louis Alphonse Laveran.