Pseudallescheria boydii is a species of fungus classified in the Ascomycota. It is associated with some forms of eumycetoma/maduromycosis and is the causative agent of pseudallescheriasis. Typically found in stagnant and polluted water, it has been implicated in the infection of immunocompromised and near-drowned pneumonia patients. Treatment of infections with P. boydii is complicated by  resistance to many of the standard antifungal agents normally used to treat infections by filamentous fungi.Pseudallescheria boydii fungal infection was the cause of death in three athletes submerged in the Yarkon River after a bridge collapsed during the 1997 Maccabiah Games. Taxonomy
The fungus was originally described by American mycologist Cornelius Lott Shear in 1922 as a species of Allescheria. Shear obtained cultures from a patient of the Medical Department of the University of Texas. The microbe was apparently associated with a penetrating thorn the patient had incurred in his ankle while running barefoot 12 years before. The diseased area was found to contain hyphae-containing granules that, when cultured, led to the growth of the organism. Shear considered the fungus most closely related to Eurotiopsis gayoni (now called Allescheria gayoni). The specific epithet boydii refers to Dr. Mark F. Boyd, who sent Lott the specimen. David Malloch moved the species to the newly created genus Petriellidium in 1970. The genus name of Petriellidium was in honour of Lionello Petri (1875-1946), who was an Italian botanist (Mycology) and Phytopathologist from Florence.
But it has been hypothesized that primaquine (and perhaps also the newer, related drug tafenoquine) might kill a proportion of non-circulating merozoites as well as hypnozoites, such as merozoites in bone marrow, thereby reducing the number of recrudescences (not only hypnozoite-mediated relapses) that take place. Clarity in this regard is expected to be forthcoming soon. Use of primaquine in combination with quinine or chloroquine each of which is very effective at clearing P. vivax from blood, improves outcomes; they appear to also potentiate the action of primaquine.As of 2016, the US Centers for Disease Control and Prevention recommends the use of primaquine for primary prophylaxis prior to travel to areas with a high incidence of P. vivax, and for terminal prophylaxis (anti-relapse therapy) after travel.A single dose of primaquine has rapid and potent ability to kill gametocytes (stage V) of P. falciparum and P. vivax in blood; it also kills asexual trophozoites of  P. vivax in blood, but not of P. falciparum. Because of its action against gametocytes, the WHO recommends it for use in reducing transmission to control P. falciparum infections. Pneumocystis pneumonia
Primaquine is also used in the treatment of Pneumocystis pneumonia (PCP), a fungal infection commonly occurring in people with AIDS and, more rarely, in those taking immunosuppressive drugs. To treat PCP effectively, it is usually combined with clindamycin.