Pythium
One genus of parasitic oomycetes is called Pythium. They are commonly called water molds. The genus Pythium consists of about 200 species and are common pathogens which cause disease in crops, plants and fish. Pythium insidiosum is the only species which causes infection in both plants AND animals.
Pythium Insidiosum
P.I., the etiological agent of pythiosis insidiosii, causes life-threatening infections in animals. The disease most commonly infects horses and dogs. It also infects cats, cattle, equines, captive polar bears and humans.
Pythiosis is frequently reported in tropical and subtropical regions of the world. In the United States, the disease frequents states along the Gulf of Mexico and East coastal areas, but also occurs in cooler and dryer areas of the U.S. as well.
Areas Found
P.I., like other Pythium spp, needs wet environments to carry out its life cycle in nature. Pythiosis occurs primarily in the fall and early winter after warm summer months, especially after periods of high precipitation and/or flooding. Areas of warm, stagnant water water or objects such as sticks that rest in these areas are more likely to harbor the infectious zoospores. Animals that encounter these areas or objects have an increased risk for the disease; however, the infection can be acquired after simply contacting moist soil and grass. Irrigated fields and irrigation pipes can also harbor the pathogen.
Infection
It is suspected that the invading zoospores enter an animal through open wounds, either in the skin or in the gastrointestinal tract. Water lilies and other aquatic plants and submerged grasses, including rice plants, are thought to be normal hosts. The zoospores have a strong attraction for hair, water-lily, and grass leaves.
Young dogs most often are affected, with several breeds such as the Labrador Retriever, German Shepherd and the Cavalier King Charles being seen most often.
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Pythiosis Description by Leonel Mendoza
