The role played by protozoa in causing disease
Laveran’s first studies were on the tissues and blood of patients suffering from malaria. He became certain that the pigmented formations in the blood were different forms of a parasitic organism, although the thinking at the time was that malaria was caused by a bacteria found in the soil around marshes. He was eventually able to demonstrate that malaria was caused by a parasitic protozoan, and during the remainder of his career he classified other protozoa responsible for infectious diseases in animals and humans.
Through experiments on many animals, including fish, reptiles, rats, mice, cattle, birds and monkeys he described many varieties of protoza, including Trypanosomes, which are responsible for sleeping sickness in humans, and the animal form of the disease, nagana. Laveran’s study of these parasites led to the discovery that arsenic was an effective treatment for sleeping sickness, and to the development of the first drugs. He described and classified numerous species of protozoa, and his discovery that protozoa cause disease is considered a major advance in human and veterinary pathology.