Women and children (peaking at age 10 to 19 years) are at high risk. Children play in water and women Bosutinib cost use water for their daily chores.4 Given the increased migration from rural to urban regions, the disease is spreading to urban areas and infecting swimmers. Due to increased ecotourism, the cases of schistosomiasis are being diagnosed more often in travelers. Lifecycle The lifecycle of schistosomes begins from the miracidia that are excreted in human feces or urine into fresh water (Figure 2). The miracidia have 1 to 3 weeks to search for their intermediate host-a snail. The infected snail eventually excretes the larva form, called cercaria. The two-tailed cercariae swim until they reach a human host and burrow through intact skin using oral suckers (Figure 3). Figure 2 Lifecycle of schistosomiasis.

Available at http://med.stanford.edu/labs/michael-hsieh/images/Schistosomiasis_Life_Cycle.jpg. Reprinted with permission. Figure 3 Cercariae. Available at http://www.abdn.ac.uk/ibes/research/int_phys/vector/. Reprinted with permission. The cercariae lose their tail upon entry and transform into schistosemulae that develop a double-lipid barrier that is resistant to human immune responses. They incorporate host proteins and major histocompatibility complexes and migrate through blood vessels. They enter pulmonary capillaries and eventually enter the portal veins where they mature into adult worms. Male and female worms attach together at the male��s gynecophoric canal (Figure 4). Here they migrate into mesenteric veins (S mansoni, S japonicum) or vesicular veins (S haematobium).

Figure 4 Male and female worm paired. Available at http://www.blessedherbs.com/images/pck-09.jpg. Reprinted with permission. Eggs are released into the bowel or bladder and cause a granulomatous response. During this time, they mature into miracidia that are excreted out of the human host via urine or feces, thus completing the cycle.5 Symptoms Most people do not develop symptoms of acute schistosomiasis. Individuals who have had prior infections are most likely to develop high temperatures known as Katayama fever. Although symptoms resolve after a few weeks, mortality rates can be as high as 25% during this acute phase. A maculopapular rash appears at the site of entry. Those with prior exposure to schistosomiasis can develop a significant schistosomal dermatitis (Figure 5).

Laboratory findings show increased eosinophilia and circulating immune complexes. Figure 5 Maculopapular rash. Available at http://www.stanford.edu/group/parasites/ParaSites2006/Schistosomiasis/dermat.jpg. Reprinted with permission. In the chronic stage, symptoms can present months Dacomitinib or years later. They vary depending on the species that has infected the host. In general, the eggs induce a significant immune response and form granulomas. S mansoni and S japonicum cause abdominal pain, bloody diarrhea, and colonic polyposis.