Giardia lamblia
Introduction
Introduction to Giardia lamblia After the human body is infected with Giardia, there is a malabsorption syndrome mainly characterized by diarrhea. The diarrhea is watery stool, large amount, bad breath, no pus and blood. Children with diarrhea can cause malnutrition such as anemia, leading to diseases with slow growth. If it is not treated in time, it will develop into chronic, manifested as periodic loose stools, repeated attacks, stools are very stinky, and the course of disease can last for several years. Giardia cysts have strong resistance to the external environment. Some commonly used disinfectants have no killing effect on the capsule at standard concentration. Ozone and halogen have mild lethality to the capsule, but for disinfection. The concentration of green gas dissolved in tap water does not reach the purpose of killing the capsule. Therefore, drinking tap water is not reliable. The pollution of water sources mainly comes from human and animal manure and sewage. The water pipes communicate with the sewage pipes due to long-term disrepair, or the sewage is sucked into the pipes due to leakage of pipe walls. basic knowledge The proportion of illness: 0.005% Susceptible people: no special people Mode of infection: digestive tract spread Complications: anemia
Cause
The cause of Giardia lamblia
Infectious factor
Giardia is infected by fecal-mouth and is generally considered to be related to the following factors:
Water pollution (20%):
Giardia cysts have strong resistance to the external environment. Some commonly used disinfectants have no killing effect on the capsule at standard concentration. Ozone and halogen have mild lethality to the capsule, but for disinfection. The concentration of green gas dissolved in tap water does not reach the purpose of killing the capsule. Therefore, drinking tap water is not reliable. The pollution of water sources mainly comes from human and animal manure and sewage. The water pipes communicate with the sewage pipes due to long-term disrepair, or the sewage is sucked into the pipes due to leakage of pipe walls.
Food contamination (20%):
Food contamination comes mainly from food processors or managers, and some people are carriers of Giardia. In addition, foods or fruits contaminated with Giardia are shared among children.
Unusual sexual behavior (14%):
This type of communication has attracted more and more attention. The anal sex of homosexuals often leads to indirect "fecal-mouth" infection of the cyst.
Giardia lamblia infection, the mechanical and chemical effects of the body on the body, resulting in a non-specific and specific host response.
Pathogenesis
1. Pathogenicity of Giardia: It is generally believed that the incidence is related to the virulence of the strain, the immune status of the organism and the symbiotic internal environment. The trophozoite is adsorbed on the surface of the intestinal mucosa by suction cups, causing mechanical irritation and damage leading to mucosal inflammation. When the worms are multiplied, they can cover the intestinal mucosa in large areas, affecting the absorption of fat and fat-soluble vitamins. The worms also compete with the host for intra-cavity nutrition, and changes in the intestinal flora can cause intestinal dysfunction to varying degrees.
2. Immune response: In recent years, human immune factors are considered to be the main pathogenesis. The surface antigen components of trophozoites can induce the body to produce protective immune responses, activate immune cells, and inhibit or kill insects. Among them, 82kDa/88kDa antigen is present on the surface of trophoblast cells and flagella. The 56 kDa/57 kDa antigen is also present on the surface of the somatic cells, which stimulates the body to produce protective IgA and IgG antibodies during natural infection. After infection in normal immune function, most of them produce specific humoral immune responses, producing specific IgM, IgG, and IgA antibodies that kill, dissolve, or phagocytose by direct cytotoxicity, complement-mediated lysis, and opsonization. In addition, the intestinal mucosa can be found to secrete IgA antibodies and obtain certain immunity, which can affect the activity of the insects through agglutination; or act on the surface components of the insects involved in the adsorption, and block the adsorption of the insects on the intestinal mucosa. Patients with AIDS and other immunodeficiency are susceptible to the worm and have a high incidence due to the inability to produce an effective immune response.
3. Pathology: The lesions involve the duodenum and the upper jejunum. In severe cases, the gallbladder, bile duct, small intestine, appendix, colon, pancreatic duct, and hepatic duct can all be affected. Small intestinal mucosa congestion, edema, inflammatory cell infiltration and superficial ulcers. Intestinal microvilli edema, degeneration and vacuolation. During severe infection, microvilli thickened and atrophied, and a large number of neutrophils and eosinophils infiltrated in the submucosa and lamina propria.
Epidemiology
The genus Giardia lamblia is widespread throughout the world, with tropical and subtropical tropics being the most common parasitic protozoa in China. The resulting infection rates vary depending on the time of the investigation and the method of examination used. According to recent data, in Beijing and Gansu, the fecal test result was 2.7%, while the ELISA method was 12.8%. The fecundity of Yueqing County in Zhejiang was 2.5%, the faecal examination of farmers in Chaoyang City of Liaoning was 6.1%, and that of Shenyang was 12.5%. The world infection rate is 1 to 30%. Most of them are scattered, and in special cases can also cause outbreaks. The former Suwen infection rate is high, such as Britain, the United States and many other countries are infected by the former Soviet Union.
People are the main source of infection, especially those who carry the capsules. Often, one person has a cyst infection in the whole family, which is recorded at home and abroad. Encapsulation is the main part of the spread, and people are infected by swallowing contaminated water and food. The capsule has strong resistance in the outside world. From the observation of transmission electron microscopy of the freeze-etching complex method, the wall of the capsule is opened, showing the structure of more than a thousand layers of plate-like membrane in the wall of the capsule, indicating that the capsule has a strong external Self-protection. The capsule can survive for 3 weeks in moist feces, 5 weeks in water, and 2 to 3 days in chlorinated water, but it can easily die at 50 ° C or in a dry environment. The capsule can live for 24 hours in the digestive tract of the fly, and still viable in the digestive tract for 12 days. Due to the large number of cysts in the feces, the resistance in the external environment is strong, and the infection mode is simple, so the insects are widely distributed. It has been reported that in the United States, leeches can be found to carry cysts, and it is found that cattle, horses, sheep, wolves and dogs also have this worm, which may have certain significance in epidemiology and should be taken seriously.
Pathological change
When the parasite is parasitic in the biliary system, it may cause cholecystitis or cholangitis. Such as upper abdominal pain, loss of appetite, hepatomegaly and fat metabolism disorders. The pathogenic mechanism of Giardia is not fully understood. It is generally believed that the incidence of the disease is related to a variety of influencing factors such as virulence, body reaction and symbiotic internal environment. The mechanical barrier of the insect group, the nutritional competition, the stimulation and damage of the trophozoite adsorbed on the intestinal mucosa by the suction cup, the synergistic effect of the bacteria in the intestine, etc., can cause intestinal dysfunction to varying degrees. In particular, the host's immune status is an important factor in the severity of clinical symptoms, such as low-gammaglobulinemia and immune dysfunction or AIDS patients, are prone to serious infections.
Prevention
Giardia lamblia prevention
1. Check and treat pets and control the source of animal infection.
2. Examine the staff of the food service industry and nursery institutions and find that the infected person is treated promptly.
3. Pay attention to environmental hygiene, personal hygiene, diet and drinking water hygiene.
4. Manage feces, promptly treat the feces of infected people and pets, and protect water sources from pollution.
5. Eliminate flies and cockroaches.
Complication
Complications of Giardia lamblia Complications anemia
1. Anemia.
2. Growth retardation.
3. Water and electrolyte metabolism disorders.
Symptom
Blue Giardia symptoms common symptoms anorexia abdominal pain diarrhea bloating
Patients with Giardia lamblia infection are mostly asymptomatic carriers. The incubation period is more than two weeks, and can even vary from several months. The clinical symptoms vary depending on the lesion, and the surface is varied and the symptoms are different. In summary, it can be divided into three categories: systemic symptoms, biliary system symptoms and gastrointestinal symptoms.
(1) Systemic symptoms:
1. Neurological symptoms: such as insomnia, headache, fatigue, dizziness, black eyes, sweating, increased nerve excitability, and hyperreflexia.
2. Thyroid dysfunction: It has been found that some (15.5%) patients with giardiasis have altered thyroid function, of which thyroid hyperthyroidism accounts for the majority, basal metabolism increases by 16% to 20%, and some patients may increase 30%, and therefore symptoms of hyperthyroidism.
(B) biliary system symptoms:
Giardia lamblia is parasitic in the biliary system and can cause cholecystitis and cholangitis. The main symptoms are upper abdominal pain, loss of appetite, indigestion, nausea, belching, burning sensation in the stomach, hepatosplenomegaly, tenderness, aggravation when eating greasy, and sometimes jaundice.
(three) gastrointestinal symptoms:
1. Duodenal inflammation: There is duodenal ulcer-like pain, accompanied by anorexia, hypotension and so on. X-ray examination showed more deformation of the ball and even ulceration. These symptoms can be eliminated after anti-insect treatment.
2 acute or chronic appendicitis type: symptoms similar to general appendicitis. Excised appendix, inflammatory lesions, sometimes visible ulcers in the mucosa, a large number of trophozoites can be found between the villi.
3. Colitis type: The main symptoms are dull abdominal pain, increased bursts, accompanied by nausea, vomiting, diarrhea, often misdiagnosed as dysentery.
4. Rectal sigmoiditis type: same as general rectosigmoiditis. Examination with sigmoidoscopy revealed diffuse hyperemia, edema, severe round ulcers, and an exudative pseudomembrane on the surface of the ulcer. A large number of trophozoites can be seen by swab inspection. No special pathological changes.
According to Schulz's 324 clinical observations, diarrhea accounted for 96%, fatigue accounted for 72%, weight loss accounted for 60%, abdominal pain accounted for 61%, nausea accounted for 60%, soft stools accounted for 57%, bloating accounted for 57% 42%, fever accounted for 17%. According to Wolfe, the symptoms of acute infection are sudden attacks, fulminant diarrhea, watery stools, stench, and abdominal pain. Therefore, acute symptoms are very similar to acute amoebic dysentery or bacterial dysentery and Salmonella infection, should be noted. Some patients have subacute infection symptoms, mainly characterized by intermittent loose stools, abdominal pain, loss of appetite and so on. Chronic patients are the most common, manifested as periodic loose stools, repeated attacks, stools are very stinky, because patients do not pay attention, the course of disease can often be as long as several years. Chronic infections in children with weight loss, developmental delay, patients often have lactose, xylose, vitamin A and vitamin B12 and abnormal fat absorption.
Examine
Examination of giardiasis
1. Pathogen examination: trophozoites can be found in fresh diarrhea, and most of the mushy and formed stools are cysts. The faeces can be found directly in the saline smear; the iodine solution can make the capsule easy to identify. Concentration methods such as zinc sulfate floating method can increase the detection rate of the capsule. The stool examination should be sent three times and three times, and the positive rate of the three tests can be increased to 97%. The worms can be found in duodenal drainage, intestinal mucus or biopsy.
2. Immunological test: It can be divided into two types : serum antibody and fecal antigen.
(1) Detection antibody: Since the pure culture of Giardia lamblia has been successfully cultured, the preparation of high-purity antigen has become possible, which greatly improves the sensitivity and specificity of immunodiagnosis. Two strains of Giardia lamblia have been established in China, which provides conditions for domestic immune diagnosis. Enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent antibody assay (IFA) were used to examine serum antibodies in patients, with the former up to 75% to 81% positive and the latter up to 66.6% to 90% positive.
(2) Detection of antigen: The antigen in the fecal diluent can be detected by an enzyme-linked immunosorbent assay (double sandwich method), a dot enzyme-linked immunosorbent assay (Dot-ELISA), or convective immunoelectrophoresis (CIE). The double-sandwich ELISA positive rate was as high as 92%, the Dot-ELISA was also 91.7%, and the CIE was 94%. Detection of fecal antigens can be used not only for diagnosis, but also for efficacy.
3. Molecular biological diagnosis; in recent years, polymerase chain reaction (PCR) is used to detect the ribosomal RNA (rRNA) gene product of Giardia lamblia, which can detect an amplified copy of the amount of genomic DNA equivalent to a trophozoite. Trophozoites and cysts can also be detected using radiolabeled chromosomal DNA probes. Molecular biological methods have high specific sensitivity and thus have broad application prospects.
Abdominal B-ultrasound understands the liver and gallbladder. X-ray and ECG should be performed.
Diagnosis
Diagnosis and identification of Giardia lamblia
1, pathogen diagnosis
(1) Fecal examination The trophozoites were examined by saline smear method, and the capsules were examined by iodine staining and smear, and the capsules were also examined by formaldehyde diethyl ether precipitation or zinc sulfate concentration method. The cysts are usually examined in the formed feces, while the trophozoites are found in the thin stools. Due to the intermittent characteristics of the capsule formation, it is advisable to check the feces every other day for more than three times.
(2) Duodenal juice or bile examination can be used for multiple negative feces to increase the positive detection rate.
(3) Intestinal capsule method allows the subject to swallow the capsule containing the nylon thread, the free end of the thread is left outside the mouth, after the capsule is dissolved, the nylon thread is loosened and stretched, and after 3 to 4 hours, it reaches the duodenum and the jejunum, nourishing The body adheres to the nylon thread, then slowly pulls out the nylon thread and scrapes the attached object for microscopic examination.
2, immunodiagnosis
For the auxiliary diagnosis, there are mainly enzyme-linked immunosorbent assay (ELISA), indirect fluorescent antibody test (IFA) and convective immunoelectrophoresis (CIE), among which ELISA is simple and easy, and the detection rate is high (92% to 98.7%). Features apply to epidemiological investigations.
Differential diagnosis
Gastrointestinal inflammation caused by amoebic dysentery, bacterial dysentery or other causes should be considered for differential diagnosis. Above abdominal pain, hepatic hypertonia, and liver function impairment are considered cholecystitis, biliary tract infection and viral hepatitis. It is an important step to identify the giardia larvae repeatedly.
