NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
Page 2“African Illness” by Kevin M. Bonney
Part II – Diagnosis Because Robert had spent much of his time outdoors in an area of the world where the Anopheles mosquitoes that transmit malaria are common, the doctors immediately suspected he had contracted malaria. His symptoms matched those generally expected of people with malaria, but to confirm the diagnosis doctors collected a blood sample from Robert to analyze for the presence of the Plasmodium falciparum parasites that cause the disease.
When doctors looked at Robert’s blood smear under a light microscope, they did not see any malaria parasites. However, they did make a startling discovery.
“I found Trypanosoma brucei parasites in the patient’s blood,” one of the doctors remarked.
“What is Trypanosoma brucei? ” asked a nurse. “Is it a type of malaria?”
“Trypanosoma brucei is a protozoan parasite. It is not closely related to Plasmodium falciparum genetically, but there are many similarities in the way it infects people and in the symptoms it causes. The disease caused by Trypanosoma brucei, called African trypanosomiasis, is also known as African sleeping sickness. All of the patient’s symptoms are explained by this diagnosis.”
Use the sources below to learn more about African trypanosomiasis.
• “Parasites—African Trypanosomiasis,” Centers for Disease Control and Prevention http://www.cdc.gov/parasites/sleepingsickness/
• “Trypanosomiasis, African,” World Health Organization (WHO) http://www.who.int/topics/trypanosomiasis_african/en/
After thoroughly investigating these and other relevant sources, answer the questions below.
Questions 1. What is a protozoan? How is a protozoan parasite different from bacteria and multi-celled parasites such
as intestinal worms? How does T. brucei differ from the closely related American trypanosome T. cruzi, the causative agent of Chagas disease, and from the P. falciparum parasite that causes malaria? Describe notable differences in morphology, life cycle, infectivity, transmission, geographical range, disease presentation, and treatment.