Pathogenesis
The infectious stage starts when the free-swimming larval form of the schistosome, cercariae, penetrates the human skin using their suckers, proteolytic enzymes, and tail movements; the cercariae transformed into schistosomulae by losing its tail and subsequently travels to the heart and lungs through venous system until it eventually reach the liver where it will mature into the adult form. The diseases caused by the schistomes are characterized into acute schistosomiasis and chronic schistosomiasis, and they can vary dependent on the species of schistosome.Acute Infection

Minutes to days after initial infection:
Cercerial dermatitis (Swimmers itch) - swimmers itch is caused by a localized allergic reaction at the sites of skin penetration by the cercariae causing an inflammatory reaction that is characterized by itchy red pimples and blisters. Few weeks to months after initial infection:
Acute Schistosomiasis (Katayamas Fever) - the exact pathophysiology of this disease remains unknown. It has been hypothesized to be caused by a systemic immune response due to immune complex formation (Type III hypersensivity) with the foreign antigens on the migratory schistosomula and the eggs, and the subsequent deposition of these complexes on various tissues leading to activation of an autoimmune response. Acute schistosomiasis caused by S. mansoni and S. haematobium generally affect people who have been infected for the first time such as tourists visiting endemic regions. In contrast, cases of acute schistosomiasis caused by S. japonicum can occur in reinfection to population who reside in endemic regions, and they occur in higher incidences and can have worse prognosis.
Penile pain refers to pain in the penis, human or otherwise. Common causes
Penile injury
Circumcision
Penile fracture
Priapism
Phimosis
Peyronies disease
Sexually transmitted infections
Chronic prostatitis/chronic pelvic pain syndrome

Cultural references
Priapus, a minor Greek god of fertility, is marked by his oversized, permanent erection, which gave rise to the medical term priapism. Some researchers believe the depiction of Priapus penis referred to a penile disease, and that paintings of Priapus were used to ward off the disease. See also
Genital pain
Vaginal pain
Testicular pain
List of the causes of genital pain


== References ==