page_title: Protothecosis
section_title: Cause
hierarchical_section_title: Protothecosis / Cause
caption_attribution_description: English: Photomicrograph of Prototheca wickerhamii infection in a human. Note the floret-like arrangements. Periodic acid-Schiff (PAS) stain.
context_page_description: Protothecosis is a disease found in dogs, cats, cattle, and humans caused by a type of green alga known as Prototheca that lacks chlorophyll. It and its close relative Helicosporidium are unusual in that they are actually green algae that have become parasites. The two most common species are Prototheca wickerhamii and Prototheca zopfii. Both are known to cause disease in dogs, while most human cases are caused by P. wickerhami. Prototheca is found worldwide in sewage and soil. Infection is rare despite high exposure, and can be related to a defective immune system. In dogs, females and Collies are most commonly affected.
  The first human case was identified in 1964 in Sierra Leone.
context_section_description: Prototheca has been thought to be a mutant of Chlorella, a type of single-celled green alga. However, while Chlorella contains galactose and galactosamine in the cell wall, Prototheca lacks these. Also, Chlorella obtains its energy through photosynthesis, while Prototheca is saprotrophic, feeding on dead and decaying organic matter.  When Prototheca was first isolated from slime flux of trees in 1894, it was thought to be a type of fungus. Its size varies from 2 to 15 micrometres.
caption: Photomicrograph of Prototheca wickerhamii infection in a human. Note the floret-like arrangements. Periodic acid-Schiff(PAS) stain.
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