Overview of the disease
Guangzhou tubular nematode disease is a relatively common form of helminthic larval migratory disease in China, with the pathogen being the larval or early adult (sexually immature) stage of Guangzhou tubular nematode. Clinically, visceral, especially central nervous system infections occur more often, resulting in fever, headache, vomiting, convulsions, coma and other eosinophilic meningoencephalitis or meningitis. The disease is a form of foodborne parasitic disease, also known as eosinophilic meningoencephalitis. The disease is mainly contracted by eating raw or semi-raw snail meat containing larvae of the Guangzhou tubeworm. It is now classified as a national emerging infectious disease. It is a disease named after the pathogen.
Causes
C. guangzhouensis is mainly parasitized in the pulmonary artery and the right heart of rodents, and its intermediate hosts include the brown agate snail, the rugose snail, the snail, the Chinese round snail, and the eastern wind snail, etc. More than 1,600 larvae may be found in a single snail. Guangzhou tubular nematodes are found in land snails, freshwater shrimps, toads, frogs, snakes and other animals. If people eat them without cooking, they are susceptible to parasitic diseases caused by Guangzhou tubular nematodes. People are infected by eating raw or semi-raw food containing the larvae of this worm in the intermediate host and the transfer host, and eating raw vegetables, fruits and vegetables contaminated by the larvae or drinking raw water can also be infected. Animal experiments suggest that third-stage larvae can actively enter the host through the skin. Since humans are not normal hosts of the parasite, the parasite stays in the fourth larval or early adult (sexually immature) stage in the human body.
Symptoms
The incubation period ranges from 1 to 25 days, mostly 7 to 14 days, with the incubation period in children being about three days shorter than in adults. Since the lesions in the central nervous system are more obvious and the symptoms are more severe, the inflammatory manifestations of central nervous system infection account for more than 50% of the clinical cases. Persistent headache, generalized aches and pains, loss of appetite, nausea, vomiting, and mental anomalies are often the main clinical manifestations. The headache is severe while the meningeal irritation signs are often mild, and some patients may have fever, rash, indifference, local skin pain hypersensitivity, chest pain; 30% of the patients have decreased sensation of limbs, pain hypersensitivity, mild to complete paralysis, urinary and fecal incontinence, decreased visual acuity, signs of damage to the brain nerves of the Ⅱ, Ⅲ, Ⅳ, Ⅵ and Ⅶ pairs of brain nerves, drowsiness, and coma, etc.; the early funduscopic examination is mostly without any abnormality, and in the late stage, it may show In the early stage, fundus examination is usually unremarkable, but in the later stage, there may be optic disk edema and retinal vein dilatation, however, subcutaneous wandering mass is rarely found.
Examination
1. Routine examination
(1) Blood The total number of leukocytes can be in the normal range, but it is more than 10×109/L, and eosinophilic granulocytes are increased, accounting for 0.08～0.37, and often more than 0.15.
(2) Cerebrospinal fluid: clear or slightly yellowish turbid appearance, elevated leukocyte count, up to (50-1400)×106/L, multinucleated cells and mononuclear cells roughly half, eosinophils accounted for 0.10-0.62, protein is normal or elevated, 0.27-1.09g/L, and sugar and chloride are mostly in the normal range.
2. Microscopic examination of pathogens
The fourth or fifth stage larvae of Guangzhou tubular round nematode can be found in the cerebrospinal fluid of patients, with a detection rate of 10%～44%. Naked eye observation shows yellowish fine cotton threads, 1.3-4.5cm in length, and microscopic observation shows that the appearance of male nematodes is black and white, and the tail end is slightly curved to the abdomen, which is kidney-shaped. The tail end of the female is obliquely conical, and the cuticular epidermis of the insect body is transparent and smooth, with microscopic transverse lines visible. The head is slightly rounded, with a mouth capsule at the anterior end, a short esophagus, a nerve ring, a fecal pore, a yellowish intestinal branch at the posterior end of the body, the genitalia, the vulva and the anal pore, and a long, slender, slightly obliquely conical caudal end. Sometimes single-celled eggs can be seen in the uterus of female worms.
3.Specific antigen detection
The antigen is made from the larvae of the nematode, immunize the mice, isolate their spleen cells, prepare monoclonal IgG antibody by cell fusion and cloning technology, and detect the soluble antigen of the larvae of the nematode in the cerebrospinal fluid and serum of the patients by ELISA, and a positive test can be used as a definite diagnosis basis, and the detection rate of soluble antigen of the larvae of the nematode is higher than that of the serum in cerebrospinal fluid.
4. Specific antibody test
(1) Indirect Fluorescent Antibody Test (IFAT) The larvae or adult nematodes of C. guangzhouensis are used to make antigenic slides, which are incubated by adding appropriate dilution of patient’s serum, rinsed and then added with fluorescein-labeled animal anti-human IgG or IgM antibody, incubated, rinsed and then examined by fluorescence microscope, and the results show that the detection rate of the specific IgG antibody reaches more than 90% two weeks after infection, and is positive for all four weeks after infection. The results show that the detection rate of specific IgG antibody is more than 90% in two weeks after infection, and four weeks after infection is positive; positive serum specific IgM antibody suggests recent infection; positive serum specific antibody, combined with relevant epidemiological data, clinical manifestations and other laboratory results, can make a definite diagnosis of the disease.
(2) Enzyme-linked immunosorbent assay (ELISA): The ultrasonic fragmentation of the larvae or adult nematodes of the Guangzhou tubular nematode is used to make soluble antigens, and specific antibodies are detected in the patient’s serum. This assay has been matured, and is considered to be a simple, rapid and specific assay that can be used for clinical diagnosis. Improved detection methods include spot enzyme-linked immunosorbent assay (Dot-ELISA), anti-biotin protein-biotin enzyme-linked immunosorbent assay (AB-ELISA), and immunoenzymatic staining test (IEST), etc. Detection of specific antibodies in patient’s serum by ELISA is the most commonly used immunological method for the diagnosis of the disease in clinical laboratories at present.
5. Imaging examination
(1) Cranial CT or MRI examination can find patchy changes in the brain tissue, with an area of 0.5~l.0cm2, blurred borders and irregularities.
(2) Chest CT examination There are often small nodular foci in the lung tissue, mostly scattered in the peripheral part of the two lungs, with frosted glass-like infiltrative changes around the small nodules.
(3) Electroencephalography Slowing of alpha wave is more common in patients.
Diagnosis
The diagnosis of the disease is based on: (1) a history of ingestion of or contact with an intermediate host or a transfer host containing the parasite; (2) typical symptomatic features; (3) elevated cerebrospinal fluid pressure, with a marked increase in the total number of leukocytes, of which the number of eosinophils is more than 10%; (4) a positive immunological examination or detection of larvae or developing adult females or males from the cerebrospinal fluid, although the detection rate of the etiologic agent is generally not high.
Treatment
1. Symptomatic and supportive treatment
Patients should take bed rest, give light, easy to digest, high vitamin diet, and drink more water. Give fluids appropriately according to the needs of the condition to replenish electrolytes and glucose. Timely and accurate monitoring of temperature changes should be done and recorded.
Cranial hypertension can be significantly reduced by the concomitant application of adrenocorticotropic hormones during treatment of the pathogen. Dexamethasone is commonly used and is tapered to discontinuation depending on the response to treatment. It may also be given orally in less severe cases, with the dose depending on the condition. When patients with intracranial hypertension, such as agitation, severe headache, projectile vomiting, elevated blood pressure, heart rate slowing, bilateral pupil unequal size, should be promptly injected intravenously or rapid intravenous drip injection of 20% mannitol injection, if necessary, can be repeated after 4 to 8 hours, in order to reduce intracranial pressure, to prevent cerebral herniation. Patients with obvious fever can be given physical cooling or drug cooling. Patients with severe headache can be given sedatives as appropriate; neurotrophic drugs can be given as appropriate; intermittent, low-flow oxygen inhalation; antibiotics and antifungal therapy should be given accordingly to those with combined bacterial and fungal infections; if there are worms in the eyes, ocular treatment should be carried out first and then pathogenic treatment.
2.Pathogenic treatment
Albendazole (propylthiomidazole) has good curative effect on this disease. Reduce the dose as appropriate in pediatric patients. Combination with corticosteroids can prevent and significantly reduce drug-induced adverse reactions. Animal studies have shown that treatment with flubendazole or parbendazole can also be effective. The broad-spectrum antiparasitic drug ivermectin may also be tried.
Prevention
The prevention of Guangzhou tubular nematode disease is mainly to avoid eating raw or semi-raw snails or fish, eating raw vegetables and drinking raw water; it should also prevent infection during the processing of snails.