Protothecosis

Protothecosis, otherwise known as algaemia, is a disease found in dogs, cats, cattle and humans that is caused by Prototheca, a type of green alga that lacks chlorophyll and enters the bloodstream of a person or animal. Prototheca and its close relative Helicosporidium are unusual in that they are 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. wickerhamii. Prototheca is found worldwide in sewage and soil, yet infection is rare despite the high exposure and may be related to a defective immune system. In dogs, female collies are the most commonly affected, and the first human case was identified in 1964 in Sierra Leone.