Schistosoma japonicum

Schistosoma japonicum

<p align="CENTER"><span style="color: #000000;"><span style="font-size: large;"><i><b>Schistosoma japonicum</b></i></span></span><span style="color: #000000;"><span style="font-size: large;"><b> (Katsurada, 1904) Stiles, 1905</b></span></span></p> <p align="CENTER"><span style="color: #000000;"><span style="font-size: large;"><b>(Figure 2-50)</b></span></span></p> &nbsp; <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>ETYMOLOGY:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Schisto</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> = split and </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>soma</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> = body along with </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>japonicum</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> referring to the geographical region in which it was first found.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>SYNONYMS:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Schistosomum japonicum</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> Katsurada, 1904; </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Schistosoma cattoi</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> Blanchard, 1905</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>HISTORY:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> This parasite was first discovered by Dr. Katsurada in the portal vein of a cat; a single male worm was recovered. Not long after, 32 male and female worms were found by this worker in veins of another cat that was noticed to have a swollen abdomen. In this same year, a female was found in the portal vein of a human being; the first indication of this parasites medical importance. This was also the first schistosome for which the life cycle was described by Drs. Miyairi and Suzuki.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>GEOGRAPHIC DISTRIBUTION: </b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Japan, the Yangtze basin of China, Taiwan, Indonesia, Malaysia, and the Philippines. </span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>LOCATION IN HOST:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> In the portal veins.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>PARASITE IDENTIFICATION:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> The adults of </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Schistosoma japonicum</i></span></span><span style="color: #000000;"><span style="font-size: medium;">, like those of other schistosomatids, occur as separate sexes. Males are about 15 mm long, and females are about 20 mm long. Both sexes are very elongate organisms compared to other trematodes; about 90% to 95% of the total body length is posterior to the ventral sucker, and the worms are no more than 1 mm in width. The male is stouter than the female, and the ventral body surface posterior to the ventral sucker has lateral inflations throughout its length that role towards the midline and form a groove, the gynecophoral canal. The female is held within this groove of the male throughout most of her adult life. The male has seven testes just posterior to the ventral sucker. The female has an elongate uterus that appears as a single chain of eggs that takes up most of the anterior half of her body.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"> The eggs of this species of </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Schistosome</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> are nearly spherical. the thin eggshell is light-yellow in color and lacks an operculum. On one end of the shell a small bump or process is often visible. The eggs are 70-100 µm long by 50-65 µm wide, and they contain a fully developed miracidium when passed in the feces.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>LIFE CYCLE:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Within 15 minutes to an hour after such </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Schistosoma japonicum</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> eggs enter fresh water, the developed miracidium hatches from the eggshell. The released miracidium then penetrates a snail of the genus </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Oncomelania</i></span></span><span style="color: #000000;"><span style="font-size: medium;">. Within the snail, the miracidium develops through several stages to produce cercariae; the cercariae produced by a single miracidium will all be of the same sex as adults. The cercaria is characterized by its possession of a forked tail. The final host is infected by the cercaria penetrating the skin. After going through the skin, the tail is lost, and the so-called schistosomulum makes its way into the vascular system and is carried to the lung. The growing flukes then make their way to the liver and ultimately to the mesenteric veins where they develop. The females begin to lay eggs 5 to 6 weeks after infection of the final host.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>CLINICAL PRESENTATION AND PATHOGENESIS:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> There are no descriptions of clinical illness in cats with this infection which suggests that it may be asymptomatic given the large numbers of cats that are probably infected.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>TREATMENT: </b></span></span><span style="color: #000000;"><span style="font-size: medium;">Praziquantel is probably the drug of choice.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>EPIZOOTIOLOGY:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Numerous mammals are capable of being infected with </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Schistosoma japonicum</i></span></span><span style="color: #000000;"><span style="font-size: medium;">. Other hosts besides the cat include human beings, cattle, horses, dogs, pigs, goats, and rats. </span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>HAZARD TO OTHER ANIMALS:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Other animals appear likely to develop infection and disease similar to that seen in the human, but only if the infective cercariae penetrate the skin. Thus, the infected cat is not a direct threat to other uninfected animals.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>HAZARD TO HUMANS:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Numerous human beings are infected with this parasite and serious disease and perhaps death can result from the infection.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>Figure 2-50.</b></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Schistosoma</i></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>japonicum</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> female (the thinner fluke) within the gynecophoral canal of the male. These flukes were recovered from a cat</span></span><span style="color: #000000;">.</span></p>