OVERVIEW
The fecal roundworm is a parthenogenetic parasite. The life history consists of autochthonous and parasitic generations, with the autochthonous generation taking place in the soil and the parasitic generation taking place in the human body. In the parasitic generation, adult nematodes are mainly parasitic in the small intestine of the host (e.g. human, dog, cat, etc.), and larvae can invade the lungs, brain, liver, kidneys and other tissues and organs, resulting in fecal nematode disease. The life stages of fecal roundworms in the host include adult worms, eggs, rod-shaped larvae and filarial larvae. The filarial larvae of fecal roundworms are very similar to the larvae of hookworms and Trichinella orientalis and should be identified. The pathogenesis is long. Clinical symptoms are complex and varied, with mild cases being asymptomatic, and severe cases showing ulcerative enteritis of the small intestine and colon, even causing death of the patient.
Etiology
Filamentous larvae invade the body through the skin, and the body itself and its movement cause irritation and symptoms.
When the larvae are parasitized in the human body, there are also autoinfections, and there are often 3 types of such autoinfections:
1. Direct in vivo autoinfection
After the eggs escape from the intestinal mucosa, the larvae invade the blood circulation in the intestinal mucosa and continue to develop.
2. Indirect in vivo autoinfection
After the rod-shaped larvae escape from the intestinal mucosa, they molt rapidly in the intestinal lumen for two times to develop into filamentous larvae, and then invade the blood circulation from the mucosa of the lower part of the small intestine or the colon.
3. Autoinfection in vitro
After being discharged with feces, the filarial larvae invade into the human body from the skin around the anus.
Symptoms
Most of the disease has no obvious clinical symptoms, but because the worm can cause repeated autoinfection, when the body resistance is low, such as suffering from various diseases, malnutrition, immunodeficiency, or receiving hormones and other immunosuppressive drugs treatment, often repeated severe autoinfection, appear quite serious symptoms, or even death. Therefore, its pathogenicity has become more and more attention.
1.Skin damage
When the filarial larvae invade the skin, they can cause small bleeding spots and papules, accompanied by tingling or itching, which can easily cause secondary infection after scratching. In addition, migratory linear urticaria can occur. The above lesions can often recur in the perianal, inguinal, and buttock skin due to their own extracorporeal infections. As the larvae migrate faster in the skin, the urticaria caused spreads faster.
2. Lungs
The larvae migrate in the lungs can cause hemorrhage, or inflammatory cell infiltration, and patients with severe infection can have cough, sputum, asthma, etc. Individual patients can have dyspnea, cyanosis or with bacterial bronchopneumonia, etc. If the worms settle in the lungs and bronchial tubes, the symptoms are more serious and last longer.
3. Digestive tract
Female worms lay eggs in the intestinal mucosa and soon hatch out larvae, which cause inflammatory reactions in the tissues due to mechanical stimulation and toxic effects of the worms. In mild cases, it is mainly mucosal congestion, which is characterized by catarrhal enteritis; in severe cases, it can be characterized by edematous enteritis or ulcerative enteritis. It even causes erosion of the intestinal wall, leading to intestinal perforation, and can involve the stomach and colon. Patients have symptoms such as burning sensation in the upper abdomen, nausea, vomiting or intermittent recurrent diarrhea. It is accompanied by fever, anemia, peripheral discomfort and eosinophilia.
4. Other organs
In addition, the filarial larvae can also migrate to various organs of the body, such as the heart, liver, kidney, pancreas, brain and genitourinary system, etc., and granulomas can be formed. This causes multi-organ damage, leading to disseminated fecal roundworm disease.
Fecal roundworm disease is generally a chronic course, but when the patient is extremely malnourished due to various wasting diseases, such as malignant tumors, leukemia, tuberculosis, etc., or has congenital immunodeficiency, or due to long-term high-dose use of hormones or immunosuppressive drugs, as well as patients with AIDS, the condition is often significantly aggravated by their own super-infection. Patients may develop neuropsychiatric allergic symptoms, sepsis, steatorrhea or dysentery, as well as severe dehydration, which can eventually become life-threatening due to generalized exhaustive shock.
Examination
1. Pathogen examination
The diagnosis is mainly based on the detection of larvae in feces, sputum, urine or cerebral fluid or the culture of filarial larvae. Since the patient has intermittent worm expulsion, the examination should be repeated several times. Drops of Lugol’s iodine solution can make the larvae appear brownish yellow. Eggs can also be detected in the feces of patients with diarrhea. Routine examination can use fecal smear method, Behcet’s separation method or sedimentation method, and also can use petri dish culture method.
2. Immunological examination
ELISA method can be used to detect specific antibodies in the patient’s serum, which has good auxiliary diagnostic value for patients with mild or moderate infection.
3. Other tests
Gastric and duodenal fluid drainage for pathogen detection, the value of gastrointestinal fecal nematode disease diagnosis is greater than the fecal test.
Diagnosis
The clinical manifestations of this disease are atypical, about half of the patients infected with asymptomatic, so the diagnosis is mainly based on epidemiological data, fecal examination and serological examination.
Treatment
1. Pathogen treatment
Symptomatic drugs are selected according to the diagnosis of patients. Thiabendazole is the most effective in the treatment of this disease, with a cure rate of more than 95%. However, it has more side effects and should be used with caution for people with poor liver and kidney function; the cure rate of propylthiimidazole can also reach more than 90%; in addition, thiopyrimidine and levamisole also have a certain degree of efficacy. Foreign reports citronella plants (such as lemongrass) have the effect of inhibiting the development of rodent larvae, if planted near the residence, it can play an ecological preventive effect. For diagnosed cases, should immediately deworming treatment, and keep the bowel movement, pay attention to the cleanliness around the anus, to prevent self-infection.
2.Supportive treatment
Serious patients with malnutrition, anemia, edema or dehydration should be given fluids, blood transfusion, correction of water-electrolyte disorders, active prevention and treatment of shock and respiratory failure. Avoid using immunosuppressants before deworming to prevent self-infection and spread of infection.
Prevention
The principle of prevention of this disease is to strengthen the management of feces and water source, pay attention to personal protection and avoid self-infection, especially before clinical application of hormone drugs or immunosuppressants, routine examination of fecal roundworm should be done, and if found to be infected with the worm, thorough treatment should be given to avoid serious self-infection.