5. The Eukaryotes of Microbiology

5. Introduction

Micrograph of a long cell. Micrograph of blood cells. Some have a red ring labeled “ring form”, others have dark dots and a larger ring labeled “young trophozoite”, and others have many dark dots and an amorphous structure labeled “schizont”. A photograph of mosquito netting over a bed.
Figure 5.1. Malaria is a disease caused by a eukaryotic parasite transmitted to humans by mosquitos. Micrographs (left and centre) show a sporozoite life stage, trophozoites, and a schizont in a blood smear. On the right is depicted a primary defence against mosquito-borne illnesses like malaria—mosquito netting. (credit left: modification of work by Ute Frevert; credit middle: modification of work by Centers for Disease Control and Prevention; credit right: modification of work by Tjeerd Wiersma)

Although bacteria and viruses account for a large number of the infectious diseases that afflict humans, many serious illnesses are caused by eukaryotic organisms. One example is malaria, which is caused by Plasmodium, a eukaryotic organism transmitted through mosquito bites. Malaria is a major cause of morbidity (illness) and mortality (death) that threatens 3.4 billion people worldwide.[1] In severe cases, organ failure and blood or metabolic abnormalities contribute to medical emergencies and sometimes death. Even after initial recovery, relapses may occur years later. In countries where malaria is endemic, the disease represents a major public health challenge that can place a tremendous strain on developing economies.

Worldwide, major efforts are underway to reduce malaria infections. Efforts include the distribution of insecticide-treated bed nets and the spraying of pesticides. Researchers are also making progress in their efforts to develop effective vaccines.[2] The President’s Malaria Initiative, started in 2005, supports prevention and treatment. The Bill and Melinda Gates Foundation has a large initiative to eliminate malaria. Despite these efforts, malaria continues to cause long-term morbidity (such as intellectual disabilities in children) and mortality (especially in children younger than 5 years), so we still have far to go.


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  1. Centers for Disease Control and Prevention. “Impact of Malaria.” September 22, 2015. http://www.cdc.gov/malaria/malaria_worldwide/impact.html. Accessed May 13, 2019.
  2. RTS, S Clinical Trials Partnership. “Efficacy and safety of RTS,S/AS01 malaria vaccine with or without a booster dose in infants and children in Africa: final results of a phase 3, individually randomized, controlled trial.” The Lancet 23 April 2015. DOI: http://dx.doi.org/10.1016/S0140-6736(15)60721-8.


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Microbiology: Canadian Edition by Wendy Keenleyside is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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