Blood worm disease is a parasitic infection caused by blood cluster parasites, which are spore-forming worms belonging to the genus *Hepatocystis* in the family *Hepatocystidae*. These parasites primarily reside in the blood cells, liver cells, and Kupffer cells of their hosts, where they multiply and develop.
(A) Pathogenic Blood Worms: According to Chai Jianyuan et al. (1990), six species of blood worms have been identified in crickets and turtles in China. The Chinese blood worm (*Hepatocystis sinensis*) has three distinct developmental stages within the host. First, schizonts mature in the liver Kupffer cells, appearing as ovoid or spherical structures measuring 17.92–18.24 μm by 14.84–15.24 μm, producing 15–20 short rod-shaped merozoites. Second, schizonts proliferate in the erythrocytes of hepatic sinusoids, forming X-type and Y-type schizonts that are both columnar in shape. X-type schizonts release 14–18 wedge-shaped merozoites, while Y-type schizonts produce 4–8 rod-shaped merozoites. Female gametocytes are kidney-shaped, and male gametocytes are comma-shaped with a small tail. Third, early schizonts in peripheral blood cells are broadly kidney-shaped, producing 6–12 banana-shaped merozoites. Mid-schizonts generate 6–10 merozoites, and late schizonts produce 2. Gametocytes originate from Y-type merozoites and represent an intermediate stage in the development of the next generation. The intermediate host is the soft-shelled turtle (*Trionyx sinensis*), while the final host is the cockroach. After feeding on infected blood, the parasites develop in the gill's gastrointestinal tract, undergoing gametogenesis and sporogony. During gametogenesis, amphoteric gametocytes fuse, leading to the formation of four male nuclei, one of which fertilizes the female gamete, forming a zygote. Sporogony begins with nuclear division of mononuclear oocysts, eventually producing mature oocysts containing eight sporozoites.
(B) Epidemic Situation: In a study by Chai Jianyuan et al. (1990), 248 Chinese sturgeons, 40 turtles, 25 yellow-edge shell turtles, and 2 flat-faced turtles were examined. Only flat-faced turtles showed infections, though only two individuals were tested. Other species had parasites. The infection rate in Chinese sturgeons was as high as 83.9%, with an intensity of 19.7% (calculated as the number of infected red blood cells per 1,000 red blood cells). Infections peak between May and September due to increased host activity and parasite proliferation. Although no mass deaths have been reported, the disease could become a serious threat to turtle farming if not properly managed.
(C) Symptoms: With current infection intensities not yet very high (up to 19.7%), visible symptoms are rare. However, under a microscope, infected red blood cells appear swollen and deformed, often filled with parasites, pushing the cell contents to the side. When schizonts divide inside red blood cells, they cause hemolysis, leading to an increase in immature red blood cells in the periphery—a compensatory hyperplasia. Leukocytes also show increased activity, with many pseudopodia observed.
(D) Diagnosis: Blood smears from infected turtles are stained with Giemsa or hematoxylin and eosin and examined under a microscope for the presence of blood worms.
(E) Prevention:
(1) Remove excess sludge from the bottom of the tank and disinfect it regularly.
(2) If fish parasites are detected, use old luffa pectin to extract blood. Once the blood clots, place it back in the pond to attract fish, which can then be crushed to kill the parasites.
(F) Treatment: No effective treatment has been developed yet.
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