schistosomiasis



OVERVIEW

Definition.

Schistosomiasis, also known as concolorous schistosomiasis, is a disease formed when the larvae of Schistosoma pneumoniae swim, grow and lay eggs in the lungs [1-4]. In China, the infection of Schistosoma welchii and Schistosoma civetii is predominant [4].

The disease is a zoonotic parasitic disease, mostly transmitted by raw or semi-raw food (such as pickled food, drunken food, etc.) of crabs, shrimps, and freshwater crabs, and can also be infected by accidental ingestion of food and water containing eggs or cysts of the worms.

Lung infection with Schistosoma weissei is often manifested by cough, chest pain, and coughing rust-colored sputum [4].

Schistosomiasis is not limited to the lungs, but can also infect other organs of the body, such as the abdominal cavity, brain and spinal cord.

Classification

According to the major organs infested, the disease can be categorized into the following types [4-5].

Thoracic-pulmonary type

Most common. It is mainly caused by Schistosoma vesiculare infection and is characterized by cough, chest pain and shortness of breath.

Abdominal type

It accounts for about 30% of the cases and is mostly seen in the early stage of infection. It manifests as abdominal pain, diarrhea, nausea, vomiting and other symptoms.

Abdominal pain is whole abdomen or mainly in the right lower abdomen. Diarrhea is yellow or yellowish loose stool, 2~4 times a day.

Skin type

Mainly subcutaneous nodules or masses.

The cutaneous type of Schistosoma weiensis accounts for 10% of cases and is usually non-wandering; the dermatologic type of Schistosoma civetii accounts for 50%~80% of cases and is mainly characterized by wandering.

Cerebral spinal cord type

Most commonly seen in children with Schistosoma vesiculare.

Cerebral type often has increased intracranial pressure with intracranial occupying lesion manifestation, which may have recurrent epileptic seizures, visual and limb sensory abnormalities, or paralysis, aphasia, and hemianopsia.

Other types

Scrotal mass, as big as egg or fist, localized mild pain, eggs or adult worms can be found in the mass.

Pathogenesis

The disease is endemic throughout the world, mainly in Asia (especially common in Southeast Asia) and the Americas, including China, Korea, Japan, the Philippines, the United States, Canada, Mexico, Brazil and other countries [4].

Cases have been reported in at least 24 provinces, districts, and rural areas in China, such as Jiangsu, Zhejiang, Fujian, Guangdong, Jiangxi, Guizhou, Henan, Hubei, Yunnan, Sichuan, Jilin, Liaoning, Heilongjiang, Gansu, Shandong, and Shanxi [4].

Zhejiang and Northeast China are dominated by Schistosoma vesiculare, while Sichuan, Yunnan, and Jiangxi are characterized by Schistosoma civetii.

The disease is mainly distributed in the area of direct predation on stream crabs, and the infection is mainly in summer and fall; the disease can occur in all seasons in the area of preferring drunken crabs.

Causes

Causes

Schistosomiasis is caused by the infection of Schistosoma japonicum, and the basic conditions leading to the epidemic are the following three aspects.

Source of infection

Infectious sources are mainly people infected with Schistosoma pneumoniae and patients with schistosomiasis.

Sick animals and sick animals are the main source of infection for some worm types (e.g., Schistosoma civetii) [4].

Routes of transmission

Transmission is mostly due to raw or semi-raw food (e.g., pickled, drunken, etc.) of crabs, shrimps, and freshwater crayfish.

Infection can also occur by accidental ingestion of food and water containing eggs or cysts.

Eating meat (e.g. pork, rabbit, etc.) that contains live cysts from a second host can also be infected.

Susceptible Population

The population is generally susceptible, with a higher prevalence in children and adolescents.

School-age children may be more susceptible due to exposure to crabs or butterfly flies.

Pathogenesis

Adult settlement, larval wandering and eggs can cause mechanical damage, and antigenic substances such as insect metabolites can cause an immunopathological response in the body [4].

Lesions caused by child worms

After the cysts are swallowed, they are decapsulated in the upper part of the small intestine, and the caecal larvae then migrate through the intestinal wall into the abdominal cavity between the organs and develop into child worms.

Child worms enter the lungs and can create sinus tracts and form cysts.

Lesions caused by adult worms

Adult worms cause a wide range of lesions. They may be fixed in one area or may travel to multiple organs.

Schistosoma welchii is often fixed in the lungs or travels along loose tissue, causing lesions to spread to multiple organs.

The worm enters the skull along the internal carotid artery through the rupture hole and invades the brain tissue, producing intercommunicating cysts, or it may invade the lateral ventricles and cause hemiparesis or cerebral herniation.

Lesions caused by worm eggs

Eggs can be found in the tunnels between cysts and in various tissues through which the adult worms travel.

Worm eggs cause a mild tissue reaction with no obvious necrosis of the worm egg nodules, which is a mechanical or foreign body irritation type of granulomatous reaction.

Symptoms

The disease has a complex and varied presentation with a slow onset [1].

The incubation period can be as short as a few days or as long as 10 years or more, mostly 3-6 months.

Massive infections may manifest as acute schistosomiasis within days after a large raw food intake of brook crabs or freshwater crayfish.

Main symptoms

Systemic symptoms

Acute stage patients are more prominent.

Systemic symptoms are common in patients with Schistosoma civetii and are characterized by chills, fever, dizziness, poor appetite, malaise, abdominal pain, and abdominal distension [6].

Symptoms such as chest pain, chest tightness, cough and urticaria may appear after 2 to 3 weeks.

Respiratory symptoms

Schistosoma weissei is most often parasitized in the lungs, cough is the earliest symptom, more acute in the morning, initially dry cough, and later cough sputum, usually 50-100 ml per day, mostly white sticky and with a fishy smell [7].

Sometimes it is rust-colored sputum or rotten peach-like sputum, which is associated with the expulsion of worm eggs.

Blood in the sputum or hemoptysis is often present during the course of the disease. If there is secondary infection, the sputum is increased and purulent.

Only some patients with Schistosoma civetii have occasional blood in sputum. Typical rust-colored sputum or massive hemoptysis is rare, and chest pain and pleural effusion are common, either unilaterally or bilaterally, or alternating between right and left sides.

The amount of pleural effusion is usually small, but there are cases of large amount, straw yellow or bloody, occasionally milky white; it may be encapsulated effusion, leaving pleural thickening [8].

Digestive symptoms

They are more common in the early stages of the disease. Commonly, abdominal pain, diarrhea, nausea, vomiting, and blood in the stool are present to varying degrees.

Intra-abdominal cysts may occasionally adhere to the intestinal wall and rupture into the intestines, resulting in a brownish viscous pus-blood or sesame paste-like stool, in which worm eggs may be found.

There may be pressure pain around the umbilicus or in the lower abdomen (more often in the right lower abdomen), usually without muscle tension, and occasionally nodules or masses may be found.

Occasionally, the large omentum, large and small intestine, liver, spleen and diaphragm produce extensive adhesions causing intestinal obstruction, and may produce ascites, with eosinophils predominating in the exudate.

Nervous system symptoms

Schistosoma vesiculare is the most common cause, and 10% to 20% of the diseases caused by this species are of the cerebral type. This type is manifested:

Such as headache, vomiting, unresponsiveness, simple headache can be the only manifestation.

There is also loss of vision and optic papillae edema, which are mostly seen in the early stages.

Such as paralysis, sensory deficits, aphasia, hemianopsia, etc., seen in the later stages of the disease.

Such as epilepsy, limb sensory abnormalities, etc., which is due to the lesion close to the cortex.

Such as cold, fever, headache, etc., mostly seen in the early stage.

Manifested as severe headache, vomiting, and in severe cases, coma.

Cerebrospinal fluid is bloody and eosinophils are markedly elevated.

Symptoms of spinal schistosomiasis are caused by spinal cord compression; motor disorders such as lower limb weakness and difficulty in movement are the earliest and more common; sensory abnormalities such as numbness of the lower limbs or paresthesia in the saddle area.

Low back pain, sciatica and difficulty in urination and defecation show progressive aggravation and finally paraplegia.

Other symptoms

Subcutaneous nodules or masses

Subcutaneous nodules are present in 1% to 20% of patients with Schistosoma weltii, appearing 2 months after infection in early cases and more than 3 years in late cases.

Mostly found in the lower abdomen to between the thighs, often located in the subcutaneous deep muscle, the naked eye is not easy to find, palpation can be reached.

The diameter is 1~2cm, the larger ones are softer and the smaller ones are harder. Most of them can move, can also be connected into a series, slightly pressure and itching.

The main clinical manifestation of Schistosoma cruzi is subcutaneous masses, the incidence of which reaches 50% to 80%.

Mostly seen in the abdomen, followed by the thoracic back, groin, thighs, scrotum, spermatic cord, cochlear fossa, axillary fossa, and even located in the head, neck and eyelids and other parts of the subcutaneous mass is wandering [9-10].

The masses range from the size of a soybean or walnut to a duck egg, one or several. At the beginning, the border is unclear and there is significant edema, and then gradually shrinks and becomes solid.

Liver manifestations

Both Schistosoma welchii and Schistosoma civetii can cause liver damage, but Schistosoma civetii is more common, mostly in the early stage of the disease.

The manifestations are fatigue, poor appetite, fever, abdominal pain, diarrhea, and in a few cases, ascites.

The liver is often enlarged, medium or hard, with little pressure pain, accompanied by hepatic function impairment and increased γ-globulin.

Pericardial manifestations

It can be seen in Schistosomiasis, which can account for 5% to 19%, mainly in children, and also caused by Schistosoma weizyi, which can present as constrictive pericarditis.

Others

Inflammation and effusion in the plasma cavity, including the pericardium and abdomen. Abdominal pain and abdominal masses, which may be due to involvement of the spleen, mesenteric lymph nodes, and other abdominal organs and tissues.

The kidneys can also be involved, and there may be hematuria and worm eggs in the urine.

Consultation

Department of Medicine

Department of Infectious Diseases

If you have recently eaten raw or semi-raw (e.g., pickled, drunken, etc.) crabs or shrimp and have symptoms such as fever, cough, chest pain, chest tightness, and coughing up sputum, it is recommended that you consult the Department of Infectious Diseases.

Respiratory Medicine

If you experience any of the above symptoms, you may also consult the Department of Respiratory Medicine.

Preparation

Preparation for consultation: registration, preparation of documents, common problems

Tips for the doctor

You may be required to undergo a full body checkup and chest CT examination, so you should wear loose-fitting clothes and avoid wearing clothes made of metal.

If you have a fever before the visit, you can first apply physical cool-down measures, such as applying warm towels to your forehead or wiping your armpits.

Preparation checklist for seeking medical treatment

Particular attention should be paid to the time of onset of symptoms, special manifestations, etc.

Are there any chills and fever?

Any dizziness, poor appetite, fatigue?

Any abdominal pain, bloating?

Chest pain, chest tightness, cough, phlegm?

Have you recently eaten raw or semi-raw food (e.g. pickled food, drunken food, etc.) such as crabs, shrimps, freshwater crayfish?

Have you recently consumed unclean water?

Have you recently traveled to or through an infected area with schistosomiasis infection?

Test results in the past 6 months, which can be brought to the doctor for consultation

Laboratory tests: blood test, liver function, etc.

Imaging tests: chest CT, abdominal ultrasound, etc.

Medication in the last 1 week, if available, bring along the box or package for medical consultation

Antipyretics: ibuprofen, acetaminophen, etc.

Diagnosis

Diagnosis based on

medical history

The following epidemiologic history may be present in patients with this disease.

History of raw or semi-raw food (e.g., pickled, drunken, etc.) such as crabs, shrimp, and freshwater crayfish.

Accidental ingestion of food and water containing eggs or cysts.

History of travel to an infected area with schistosomiasis.

Clinical manifestations

Respiratory symptoms: cough, sputum, hemoptysis, etc.

Digestive system symptoms: abdominal pain, diarrhea, nausea, vomiting, blood in stool, etc.

Neurologic symptoms: headache, vomiting, unresponsiveness, etc.

There may be pleural effusion, the amount is usually not large, but there are cases of large amount, straw yellow or bloody, occasionally milky white; there may be encapsulated effusion, leaving pleural thickening.

There may be pressure pain around the umbilicus or in the lower abdomen (more often in the right lower abdomen), usually without muscle tension, and occasionally nodules or masses may be found.

Laboratory tests

The total number of white blood cells may be normal or elevated.

Eosinophilia, especially high in the acute stage, and more obvious in Schistosoma civetii.

Not every patient will have the characteristic blood changes.

Blood sedimentation may be moderately to highly elevated.

Most patients with Schistosoma wilsonii have pulmonary lesions, and sputum examination reveals eosinophils, Charcot-Lehden crystals and eggs, with a high detection rate of up to 85% of eggs using the Zi-Ne stain.

Eggs that enter the gastrointestinal tract with swallowing can be detected microscopically using the modified Kato thick smear method, and the positivity rate can also reach 15% to 40%.

Early or mildly infected cases of subclinical forms and ectopic damage are often diagnosed on the basis of specific immunologic methods.

Intradermal test: after injection of adult antigen in the forearm, the appearance of dermatomes and redness after 20 minutes is a positive reaction, suggesting Schistosoma pneumoniae infection.

Posterior caecilian membrane test: the positive rate of this test is higher in patients with positive sputum and Schistosoma eggs, with higher specificity and early diagnostic value.

ELISA test: has high sensitivity (92%) and specificity (>90%) and can be performed using serum or cerebrospinal fluid [11].

Immunoblotting test: Immunoblotting test consisting of 3 methods: gel electrophoresis, transfer electrophoresis, and solid-phase immunoassay is an effective method for analyzing protein antigens and identifying biologically active antigenic components.

Pathologic examination

Pathologic examination of subcutaneous nodules or masses reveals Schistosoma japonicum eggs, child worms, or adult worms.

Subcutaneous masses caused by Schistosoma civetii are typically characterized by eosinophilic granulomas.

Imaging

X-ray chest radiograph is an important reference value for the chest and lung type, early stage can be seen in the middle and lower lung field of varying sizes, the edge of the round-like inflammatory infiltration shadow;

In the later stage, cysts and pleural effusion can be seen, which may be accompanied by pleural adhesion or thickening.

It can show lesions in the pleura, lungs, abdomen, brain, spinal cord, or obstructive lesions.

The use of fluorescent deoxyglucose-positron emission tomography/computerized tomography (FDG-PET/CT) has been reported to be informative in the diagnosis of liver, lung, and other juxtasomatous schistosomiasis lesions.

Differential diagnosis

The disease can cause symptoms related to the respiratory tract, gastrointestinal tract, and nervous system, and the symptoms are not specific and need to be differentiated from similarly symptomatic diseases under the guidance of a physician [1,4].

Tuberculosis and tuberculous pleurisy

The misdiagnosis of pulmonary schistosomiasis is as high as 40%, half of which are mistaken for tuberculosis, but the latter has minimal rust-colored sputum and most of the foci are in the lung apices and upper lung fields.

Tuberculous pleurisy is often accompanied by tuberculous foci, and the pleural effusion is predominantly lymphocytic, whereas pleural effusion in pleurisy due to schistosomiasis is more eosinophilic.

The diagnosis is confirmed by the finding of Schistosoma pneumoniae eggs in the pleural effusion or sputum. Epidemiologic information is an important reference value for the diagnosis of pulmonary schistosomiasis.

Bronchitis and pneumonia

Patients with bronchitis and pneumonia have a low rate of eosinophils in the blood and no epidemiologic history.

Lung abscess

Can be determined by a combination of imaging and blood counts. Fever and elevated neutrophils are more pronounced in the presence of abscesses.

Cerebral schistosomiasis and cysticercosis

Both can cause seizures, increased intracranial pressure, and paralysis, but each has a different epidemiologic history.

Most cases of schistosomiasis have varying degrees of hepatosplenomegaly, which can be confirmed by fecal or rectal mucosal biopsy and immunologic examination.

Cerebral cysticercosis with subcutaneous nodules can be diagnosed definitively by biopsy. Cerebrospinal fluid antibody testing is helpful in differentiation.

Intracranial tumors

History of unclean food intake, pulmonary lesions, eosinophilia, etiologic and immunologic and pathologic tests help in differentiation.

Intracranial tumors often have a significant occupying effect.

Viral hepatitis, cirrhosis

Testing for serologic markers of pathogenesis (e.g., Hepatitis B V, etc.) are helpful in the diagnostic differential.

Primary epilepsy

Seizures in encephalitic juxtasomatosis present similarly to primary epilepsy, but there is no past history of epilepsy in the former.

Headache and limb weakness after seizure may last for several days, while symptoms after primary seizure often disappear within hours.

Sputum examination for Schistosoma japonicum eggs and positive cerebrospinal fluid immunologic examination are the basis for differential diagnosis.

Treatment

Aim of treatment: to relieve symptoms, improve prognosis and minimize sequelae [1].

Treatment principle: early deworming treatment, and active symptomatic treatment.

Deworming treatment

Praziquantel

The preferred treatment is praziquantel, which has a good effect on both Schistosoma weissei and Schistosoma civetii.

After treatment, the patient’s bloody sputum disappeared, the sputum was negative for eggs, the absorption of lung lesions improved, the subcutaneous mass subsided, and the pleural effusion disappeared [12].

Triclabendazole

It has good effect on both Schistosoma weissei and Schistosoma civetii and is short and well tolerated [13].

Thiocyanol.

Recent cure rate 84%~95%. Cerebrospinal forms often require 2-3 courses of treatment.

Hirschsprung’s reaction may occur due to the release of a large amount of heterologous proteins after the killing of the worms, which manifests as shortness of breath, irritability, cyanosis, laryngeal edema, and decrease in blood pressure, etc. It should be discontinued immediately and symptomatic treatment such as adrenocorticotropic hormone should be given.

Symptomatic treatment

Dehydrating agents, such as mannitol, are used in those with intracranial hypertension [4].

Those with cough and chest pain are given cough suppressants and analgesics as appropriate.

Seizures can be treated with phenytoin sodium or diazepam, etc.

Surgical treatment

Surgery is feasible in the cerebral type presenting with intractable seizures, large hematoma, occurrence of brain herniation, as well as in the spinal cord type presenting with symptoms of compression and the lesion is not of atrophic type [1].

Lung lesions are mostly scattered and should not be treated surgically.

Skin nodules (or masses) may gradually disappear after drug treatment and usually do not require surgery.

Drainage of fluid is required when there is a large amount of pericardial, pleural, or abdominal effusion, and pericardiectomy is feasible in the presence of constrictive pericarditis.

Questions you may be concerned about

Symptoms and Treatment of Schistosomiasis

Symptoms of schistosomiasis are mainly sputum and hemoptysis, and praziquantel is often used for treatment.

Symptoms of acute stage of pulmonary schistosomiasis are loss of appetite, fatigue, abdominal pain and diarrhea, fever, etc., and in severe cases, there may be high fever, chest pain, cough, shortness of breath and other manifestations; chronic stage of the thoracic lung type of hemoptysis jam-like or rust-colored blood sputum as the main symptom, and when the worms scurrying around the thoracic cavity, there may be exudative pleurisy, pleural effusion, pericarditis, pericardial effusion and so on.

The commonly used treatment drug for schistosomiasis is praziquantel, which has the advantage of high efficacy, a short course of treatment, and low toxicity; two or more courses of treatment may be needed when treating more severe cases of schistosomiasis.

If the diagnosis of schistosomiasis is confirmed, early and standardized treatment is recommended to reduce the adverse effects of the disease. The above medications should be used under medical supervision.

Prognosis

Cure

The prognosis often varies depending on the species of the causative organism, the severity of the infection and the location of the lesion. Most of the patients have a good prognosis after early diagnosis and early targeted treatment; the prognosis of patients with cerebrospinal cord type is poorer, which may lead to paralysis.

Schistosoma cruzi is less likely to invade the brain, the life span of child worms is shorter, easier to treat, fewer sequelae, better prognosis.

Harmfulness

Patients with schistosomiasis may suffer from cough, sputum, chest pain, limb paralysis, etc., which affects the normal life of patients.

If the treatment is not timely, there may be sequelae, especially for patients with cerebral spinal cord type, paralysis, disability, etc. If the intracranial pressure rises sharply, it may also cause brain hernia, leading to death.

Daily

Daily management

Patients with loss of appetite should eat soft food that is easy to digest, such as noodles, rice porridge, etc. Avoid cold and spicy food, and avoid rough and hard food.

Attention should be paid to rest, moderate exercise, reduce strenuous farm work and housework, and avoid strenuous exercise.

Prevention

Control the source of infection

Thoroughly treat patients, people with hidden infection, and livestock such as sick cats and dogs.

Investigate and manage animal sources of infection, and trap and kill animals that are harmful to humans.

Do not feed raw crabs and butterfly flies to cats and dogs to prevent infection.

Cutting off the means of transmission

Do not eat raw or undercooked crabs or crayfish.

Do not drink raw stream water or other water sources that may be contaminated.

Pay attention to food hygiene and wash hands before and after meals.

Do not spit.

Protection of susceptible persons

There is no safe and effective vaccine for Schistosoma pneumoniae.

People in endemic areas and those who work or travel to deep forests and wilderness areas should be on guard against contracting the disease.

People in endemic areas should take the initiative to learn about the prevention and treatment of this disease and strengthen the management of feces and water sources.