The term ringworm is a little bit confusing. Usually, when a word finish by the suffix worm, it means that the organism is effectively a worm, also known as a helminth. For example, it is notably the case for flatworm, tapeworm, roundworm, whipworm, and hookworm. However, despite its name, ringworm is not considered as a worm. As such, it is also not considered as a parasite according to the strict definition accepted in the medical field. The commonly used term ringworm is then considered as a misnomer, as it leads to the false assumption that this organism is a worm.
In fact, the commonly used term ringworm refers to a very common skin infection caused by some types of fungi, namely Microsporum, Epidermophyton and Trichophyton. Even though this infection is caused by fungi rather than by parasites, these fungi can be called parasite in the broader biological sense, because they are able to establish a relationship of parasitism with their humans or mammals hosts. It is also important to note here that pets, such as cats and dogs, can be affected by these fungi and that it is very common for humans to catch the infection from their pets. This infection is effectively very easy to catch by direct contact between the specific fungi and the skin. It could then be transmitted by the contact with an infected human or animal, or by contact with the fungi in the nature, notably in damp areas. It is interesting to note that it is also possible to catch these fungi by contact with objects that had previously been in contact with an infected person. For example, it is susceptible to be acquired by walking barefoot in public shower or locker room, or by sharing clothes or towels with an infected person. It is interesting to note that moisture is also susceptible to increase the possibility of transmission of these fungi.
Finally, the real scientific name for this type of infection is dermatophytosis. This disease is susceptible to be localised to one part of the body only. Some examples of localised dermatophytosis are well known and have specific common names. It is notably the case of the athlete’s foot when the fungus infects specifically the feet and the jock itch when the fungus infects specifically the groin. These types of infections are usually very easy to treat for otherwise healthy people using topical antifungal medication, with the exception of the infection of the scalp that required prescribed oral medication. These topical creams are usually available over-the-counter, meaning that they do not require a medical prescription. However, like almost all the fungal infections, dermatophytosis can be more severe for people with weakened immune system.
Source: Centers for Disease Control and Prevention