Trichophyton rubrum (most commonly known as ringworm or tinea) is a keratinophilic (feeds on keratin) fungus that can only parasitize humans (obligate antropophile). It is believed to have evolved fairly recently and was first described in Southeast Asia in the 19th century. This fungus is now endemic to every continent except for Antarctica and it accounts for more than half of all skin infections caused by fungi . This makes this fungus not only economically important but also militarily important as it has been known to immobilize troops in various instances .
Trichophyton rubrum produces club-shaped or pear-shaped microconidia (spore producing structure) and thin-wall cigar shaped macroconidia (larger spore producing structure) which are very similar to many other species in the same family . This means that it is extremely hard to properly identify this organism. This augmented by the fact that even when properly grown and isolated, the fungus can change its shape in accordance with environmental stress, makes it almost impossible to identify by morphology alone .
Even though Trichophyton rubrum accounts for more than half of all fungal skin infections and has been documented to have incapacitated military troops in two different occasions (Vietnam in the 1960s and Panama in the 1980s) very little is known about its life cycle. Both sexual and asexual reproductive cycles are assumed to be like closely related organism but it is only from empirical evidence .
Although Trichophyton rubrum is so ubiquitous and a very common cause for skin infections that can be very painful, it is known to have very low lethality . In fact it has been reported to only cause death in immunocompromised patients and infants whose immune system are not fully developed yet, which is probably one of the reasons that there are no effective treatments that can address this problem .