OVERVIEW
The Chinese testicular schistosome, commonly known as liver fluke, was first found in the bile ducts of an overseas Chinese in Calcutta, India, in 1874 and was confirmed in China in 1908. It is mainly distributed in China, Japan, Korea, Vietnam and other Asian countries. At present, there are 26 provinces, autonomous regions and special administrative regions in China where this disease occurs or is endemic. It is infected because of bad dietary habits. Guangdong Province in China has the largest number of infected people, about more than 5 million accounting for half of the total number of infected people in the country. The adult worms are parasitized in the biliary system, causing biliary Chinese testicular schistosomiasis.
Epidemiology
Chinese testicular schistosomiasis is mainly distributed in Asia, such as China, Japan, Korea, Vietnam and Southeast Asian countries. In China, in addition to Qinghai, Ningxia, Inner Mongolia, Tibet, etc. has not been reported, the remaining 25 provinces, municipalities and autonomous regions have varying degrees of prevalence.
The prevalence of Chinese testicular schistosomiasis, in addition to the need to have a suitable first and second intermediate host and final host, but also with the local residents of the dietary habits and many other factors are closely related.
1. Source of infection
Patients, infected people, infected livestock and wild animals that can excrete the eggs of Schistosoma huazhiensis can be used as infectious sources. The main hosts are cats, dogs and pigs. Rodents, minks, foxes, feral cats, badgers, and otters have also been reported as worm-preserving hosts. In the laboratory, guinea pigs, rabbits, rats, beaver rats, hamsters, and many other mammals can be infected with Treponema pallidum.
With a wide range of hosts, the infection rate and degree of infection are higher than that of human infections, which is potentially threatening to the population.
2.Transmission
After passing through the first intermediate host (freshwater snail) and the second intermediate host (freshwater fish and shrimp), the eggs of S. oryzae will develop into cysts, and the live cysts, after being ingested, will be activated by bile, and the larvae in the cysts will break the cyst wall and come out, and then they will enter into the hepato-biliary ducts through the common bile ducts to develop into adults, and they can also arrive at the liver through the blood vessels or pass through the wall of the intestines, and then they will finally develop into adult parasites in the hepato-biliary ducts. The life span of adult worms is generally 20-30 years, and they are mainly found in the liver and bile ducts of human beings, dogs, cats and pigs, and when there are many worms, they can also migrate to larger bile ducts or even the gallbladder, and occasionally adult worms can be found in the pancreatic ducts.
3.Susceptible people
There is no gender, age or race difference in the infection of Schistosoma oryzae, and the population is generally susceptible. The key factor for the prevalence is whether the local population has the habit of eating raw or semi-raw fish. When whole fish is broiled, grilled, scalded or steamed, it may fail to kill all the cysts due to insufficient temperature, insufficient time, or excessive thickness of the fish. Adults are more often infected by eating raw fish, such as in the Pearl River Delta of Guangdong, Hong Kong, Taiwan and other places where people are mainly infected by eating “fish sashimi”, “fish sashimi congee” or scalding fish slices; residents of the Korean ethnic group in the northeast of the country are infected by eating raw fish with alcohol; children are infected by eating raw fish in the wild, which is related to their habit of eating raw fish. Infections in children are associated with eating uncooked fish and shrimp in the wild.
In addition, people may be infected if they do not wash their hands after catching fish or if they hold fish in their mouths, if they use knives and cutting boards that have been used to cut raw fish to cut cooked food, or if they use utensils that have been used to serve raw fish to serve cooked food.
Causes of the disease
The disease was first found in the bile ducts of an overseas Chinese in Calcutta, India, in 1874 and confirmed in China in 1908. The infection is caused by poor dietary habits.
Symptoms
There are no obvious clinical symptoms in mild infections, and in severe infections, in the acute phase, the main manifestations are allergic reactions and gastrointestinal discomforts, including fever, gastric pain, abdominal distension, loss of appetite, weakness of the limbs, pain in the liver area, and a marked increase in eosinophils on blood tests, etc. However, the acute symptoms of the disease are not very obvious in most patients. Most of the cases seen in the clinic are in the chronic stage, and the patients’ symptoms often appear gradually after several years. The symptoms of the digestive system are usually dominated by fatigue, epigastric discomfort, loss of appetite, anorexia, dyspepsia, abdominal pain, diarrhea, vague pain in the liver area, and dizziness, which are more common.
Common signs include hepatomegaly, mostly in the left lobe, soft texture, mild pressure pain, splenomegaly is less common. Severe infections are accompanied by dizziness, emaciation, edema and anemia, which can lead to cirrhosis, ascites and even death in the advanced stage. Children and adolescents infected with Schistosoma oryzae tend to have more severe clinical manifestations and a higher mortality rate. In addition to digestive symptoms, there are often malnutrition, anemia, edema, hepatomegaly and developmental disorders.
Examination
1. Pathogenetic examination
Fecal examination to find the eggs of Schistosoma oryzae is the basis for confirmation of the diagnosis, usually 1 month after infection can be found in the stool, commonly used methods are:
(1) Smear method The direct smear method is easy to operate, but due to the small amount of feces used, the detection rate is not high, and the eggs are very small, so it is easy to miss the diagnosis. Quantitative transparent method (Kato-Katz, glycerol paper thick smear transparent method), in the large-scale intestinal parasite survey, is considered to be one of the most effective fecal inspection methods, can be used for qualitative and quantitative examination of eggs.
(2) Egg collection method The detection rate of this method is higher than that of the direct smear method. Egg collection method includes floating egg collection method and precipitation egg collection method, precipitation egg collection method commonly used in water washing centrifugal precipitation method, ether precipitation method.
(3) Duodenal drainage bile examination Centrifugal precipitation examination of the drainage bile can also detect eggs. The detection rate of this method is close to 100%, but the technology is more complicated, and it is difficult for patients to accept. Clinically, when patients are treated with bile drainage, live adult worms can also be seen, the surface of the worm is smooth, curled up with peristalsis, which can be used as the basis for diagnosis according to the morphological characteristics.
2. Immunological examination
In recent years, with the development and application of enzyme, isotope, biotin and colloidal gold and other labeling techniques and new methods, immunological methods have been widely used in clinical auxiliary diagnosis and epidemiological investigation. Commonly used methods include indirect hemagglutination test (IHA), indirect fluorescent antibody test (IFAT), enzyme-linked immunosorbent assay (ELISA) and so on.
3. Imaging examination
When B-mode ultrasound is used to examine patients with schistosomiasis, a variety of abnormal changes can be seen on the ultrasound image, such as coarse and uneven intrahepatic spots, speckles, clumps or snowflakes, diffuse small and medium-sized dilatation of the bile ducts of varying degrees, bile duct wall coarseness, thickening, echo enhancement, or bile ducts in proportion to the distortion and dendritic echogenicity. Although the specificity of sonogram is not strong, it still has certain diagnostic value when compared and analyzed with epidemiology, clinical manifestations and laboratory tests.
CT examination is also of great value in the diagnosis of Hirschsprung’s disease.
Diagnosis
Ultrasound and CT of early cholangitis in Chinese testicular schistosomiasis may have no special manifestations, and bile duct stones and obvious characteristic dilatation of bile ducts can be seen in the middle and late stages. Intrahepatic bile ducts are uniformly dilated from the hepatic hilum to the periphery, and the subperitoneal bile ducts may show cystic dilatation. Characteristic ultrasound and CT manifestations help to clarify the diagnosis, but those without characteristic manifestations are often missed. Fecal worm egg test for Schistosoma China Branchiensis eggs, bile worm egg test to find adult Schistosoma China Branchiensis and ERCP are significant in confirming the diagnosis of the disease.
Treatment
The most widely used drugs for the treatment of Chinese testicular schistosomiasis are praziquantel and albendazole.
Prevention
Chinese testicular schistosomiasis is caused by eating raw or semi-raw freshwater fish and shrimp containing cystic larvae. Prevention of Chinese testicular schistosomiasis should grasp the link of oral transmission, and preventing the ingestion of live cystic larvae is the key to preventing and controlling this disease. Do not eat raw fish and uncooked fish or shrimp, improve cooking methods and eating habits, pay attention to raw and cooked food utensils should be used separately. Domesticated cats and dogs with positive fecal examination should be given treatment, do not feed uncooked fish and shrimp to cats, dogs and other animals, so as not to cause infection. Strengthen the management of feces. Combine with agricultural production to clean up pond mud or use medicine to kill snails.