share the same pattern in reproductive cycle, the transmission occurring through eggs, a proportion of which are eliminated through urine (S. haematobium) or feces (S. mansoni, S. japonicum and others). These eggs release larvae (miracidium) that infect freshwater molluscs in which the parasites multiply through asexual reproduction. These molluscs release aquatic larvae (cercariae) that actively penetrate the skin of a new, vertebrate host. These larvae become adults that inhabit inside the veins in the digestive system (S. mansoni and S. japonicum) and of the urinary system (S. haematobium). The geographic distribution of each species is varied and depends on the presence of molluscs capable of serving as hosts (each Schistosoma species has different molluscs as hosts). Precarious sanitary conditions also contribute in the definition of locations where schistosomiasis occurs [14]. Schistosoma mansoni occurs in 74 countries located in Africa, the Middle East, South America and the Caribbean. Its eggs measure about 60 x 140 μm, with lateral spine and are eliminated in the feces, being a main cause of intestinal, hepatosplenic, cardiopulmonary and cerebral diseases, aside from being the main cause of spinal cord schistosomiasis. S. haematobium occurs in Africa and in the Middle East and its eggs measure about 60 x 150 μm, with terminal spine, are eliminated in the urine and on rare occasions in the feces, being the mains cause of urinary diseases and spinal cord schistosomiasis. S. japonicum, S. mekongi and S. malayensis occur in Asia (they are also called S. japonicum-like); eggs measure about 60 x 100 μm, lack spine and are eliminated in the feces, causing hepatic diseases, cerebral neuroschistosomiasis, although there have been rare reports of cases in which spinal cord schistosomiasis was caused by S. japonicum. S. intercalatum occurs in Africa. Eggs are eliminated in the feces. It causes mild intestinal disease but not neuroschistosomiasis, being the least important species, clinically. The presence of spines in the eggs of S. mansoni and S. haematobium might explain why medullar and cerebral neuroschistosomiasis are more common in these species. Spine makes it more difficult for the eggs to travel through the vertebral veins, causing them to be stuck in the lumbar or thoracic spinal cord. S. japonium's eggs, being smaller and lacking spine, migrate more easily to the brain through these veins, crossing the spinal cord without sticking to it. There are, still, species belonging to the Schistosomatidae family (ex: Trichobilharzia regenti) that can cause cercarial dermatitis (or summer's itch) without, however, reaching adult life in men and, therefore, not having any major clinical importance. 2. Clinical forms of schistosomiasis 2.1. Acute phase Acute forms are basically cercarial dermatitis or summer's itch, cutaneous lesion secondary to the penetration of the skin by the cercaria, and Katayama's fever (or syndrome), which is also called acute or toxemic schistosomiasis and occurs, in genera, after three to ...