Giardiasis

Introduction to Giardiasis Giardia lamblia is now known as giardiasis, a protozoal disease caused by parasitic giardialambila in the human small intestine. Clinically, diarrhea, abdominal pain and bloating are the main manifestations, and can cause cholecystitis, cholangitis and liver damage. In addition to endemic epidemics, this disease can also lead to waterborne outbreaks. Infection among tourists is also very common. In recent years, it has been found that AIDS patients can often be infected with the worm. basic knowledge The proportion of illness: 0.03% Susceptible people: no specific population Mode of infection: non-infectious Complications: electrolyte imbalance anemia malnutrition

The cause of giardiasis

(1) Causes of the disease

The insect was first discovered by Leeuwenhoek (1681) in his own feces. Lambl (1859) described its morphology in detail and named it Lamblia intestinalis. Stiles (1915) proposed to rename it giardia lamblia to commemorate the worm. The two founders, Giardia and Lambl, belong to the genus of the foot of the foot, the genus of the genus, the genus, the genus, the genus, the genus, the genus, the genus, the genus, the genus In addition to the flagellate (G. lamblia), there are a variety of Giardia, such as G. bovis, and G. egui, which are parasitic in mammals, birds, and amphibians. , G. muris and so on.

Form

The worm has two forms of trophozoites and cysts. The trophozoites are like a half-cut pear, which is named after it.

The front end is round and blunt, the back end is sharp, the back ridge is semi-circular, the ventral surface is flat, the worm body is 9-21 m long, the width is 5-15 m, the thickness is 2-4 m, and the front half of the abdomen is depressed to form a suction cup, and the worm body is adsorbed by the suction cup. On the surface of the intestinal mucosa, the worm body is bilaterally symmetrical, with four pairs of flagella, two pairs of lateral flagella are located on both sides of the worm body, a pair of abdominal flagella are located on the ventral surface of the worm body, a pair of tail flagella are extended to the rear of the worm body, and the flagella can swing to make the worm body For rapid flipping movement or swinging left and right, the cytoplasm of the trophozoites is granular after staining. There are two nucleus on both sides of the anterior midline of the worm body. There is a large nucleolus inside and four pairs of bases, two of which are clearly visible, respectively. The shaft column is connected with the front side flagella, and the shaft column extends backward to connect a pair of tail flagella. There is a pair of half-moon shaped middle body in the middle of the shaft column. The capsule is elliptical, 8 to 12 m long and 7 to 10 m wide. There are uneven gaps between the worms and the worms. The immature capsules have two nucleuses, and the mature capsules have four nucleuses. The capsular worms have the same structure as the trophozoites except for the free free flagella. The trophozoites are observed by scanning electron microscopy. Uplift, the surface is orange peel, abdominal suction It is an asymmetric spiral structure composed of a single layer of microtubules. The periphery of the worm body has a prominent pseudopod-like circumference. Transmission electron microscopy reveals that the flagella originates from the matrix, and the matrix first emits a naked cytoplasmic axis, and the axis is extended in vitro. The flagella is formed. The cross-sectional structure of the flagella is composed of nine pairs of surrounding microtubules and two central microtubules. The whole body is supported by microtubules. The median body is located at the back end of the two cores. Tubular structure, without membrane wrap, that is, the old sub-matrix, a flat vesicle on the back of the worm, the cytoplasm of the worm is filled with free ribosome and polynucleoprotein, but the wireless granule, smooth endoplasmic reticulum, Golgi And lysosome and other organelles, scanning electron microscopic observation of the surface of the cyst wall is orange peel, uneven, fine texture, the capsule wall is composed of more than ten layers of membrane structure.

2. Life history

The life history of the worm is simple, and the trophozoite is parasitic in the small intestine, especially in the duodenum, gallbladder, liver, pancreas, etc., and the trophozoites are attached to the intestinal mucosal epithelial cells by suction cups to obtain nutrients by infiltration. The schizophrenia breeds, some trophozoites fall off the intestinal wall, and the contents enter the end of the small intestine and form cysts, which are excreted with the feces. After the human mouth is ingested by the mouth, it enters the duodenum through the stomach. The nucleosome breaks out of the sac, and the cytoplasm divides into two trophozoites. It is a trophozoite in the acute phase of diarrhea. In the chronic phase, the capsule is mainly in the capsule, and the number of cysts in the human feces is large. The amount of cysts can reach hundreds of millions or even tens of billions, and Giardia lamblia can survive in artificial medium. Two pure cultured strains (Beijing strain and Sichuan strain) have been obtained in China.

(two) 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 stimulation and damage leading to mucosal inflammation. It can cover a large area of the intestinal mucosa, affecting the absorption of fat and fat-soluble vitamins. The insect body also competes 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 the main pathogenesis. The surface antigen components of trophozoites can induce the body to produce protective immune responses, activate immune cells, inhibit or kill insects, and 82kDa/88kDa antigens are present on the surface of trophoblasts and flagella. Above, the 56kDa/57kDa antigen is also present on the surface of the somatic cells. This antigen can stimulate the body to produce protective IgA and IgG antibodies during natural infection. After infection, most of the antibodies produce specific humoral immune responses, resulting in specific IgM, IgG, IgA antibodies through direct cytotoxicity, complement-mediated lysis and opsonization, killing, lysing or phagocytosis, and the intestinal mucosa can detect secretory IgA antibodies and obtain certain immunity, can pass Agglutination affects the activity of the worm; or acts on the surface components of the worms involved in the adsorption, blocking the adsorption of the worms on the intestinal mucosa, and AIDS and other immunodeficiency patients are susceptible to the worm due to their inability to produce an effective immune response. The rate is high.

3. Pathology

The lesions involve the duodenum and the upper part of the jejunum. In severe cases, the gallbladder, bile duct, small intestine end, appendix, colon, pancreatic duct, hepatic duct, etc. can be invaded, small intestinal mucosa congestion, edema, inflammatory cell infiltration and superficial ulcer. Intestinal microvilli edema, degeneration and vacuolization, microvilli thickening, atrophy in severe infection, a large number of neutrophils in the submucosa and lamina propria, eosinophil infiltration.

Giardia disease prevention

Strengthen water sanitation management, pay attention to food hygiene, thoroughly treat patients and asymptomatic cyst carriers, eliminate vectors such as cockroaches, flies, do harmless treatment of feces, maintain normal immune function, etc., all prevent the occurrence or prevalence of this disease Important measures.

Giardiasis complications Complications, electrolyte imbalance, anemia, malnutrition

Water, electrolyte imbalance can occur, which can cause anemia and malnutrition, and growth retardation.

Giardia disease symptoms common symptoms gastrointestinal symptoms loose stools low heat nausea and vomiting anorexia thin abdominal distension fatigue upper abdominal pain loss of appetite

The incubation period is generally 1 to 3 weeks, with an average of 9 to 15 days. The clinical manifestations are mainly gastrointestinal symptoms. The typical symptoms in the acute phase are fulminant diarrhea, watery stools and stench, but a small amount of mucus, but no pus, Patients are often accompanied by nausea, vomiting, bloating, belching, abdominal pain, common in the upper abdomen, colic, some patients have low fever, chills, headache, fatigue, loss of appetite and other systemic symptoms.

The acute phase lasts for several days. If the treatment is not timely, it may turn into subacute infection. The main manifestations are intermittent diarrhea, abdominal pain, loss of appetite, etc., which last for several months. The chronic phase mainly manifests as recurrent or persistent loose stools. For periodic short-term diarrhea, the stool is a loose yellow foam on the surface, stench, more than 10 times / d, bloating, belching, anorexia, nausea, but abdominal cramps are rare, the course of disease can often be several years.

Children and severely infected people may cause weight loss, weight loss, developmental disorders, anemia, etc. due to long-term malabsorption. If the worm invades the gallbladder and bile duct, the patient presents with cholecystitis and cholangitis symptoms, pain in the right upper abdomen or xiphoid. Nausea and vomiting, fever, tenderness in the gallbladder area, etc., the lesions involve the liver, patients with liver pain, liver pain with tenderness and liver damage as the main performance, in addition, some patients can be manifested as gastritis, appendicitis.

Giardiasis check

Pathogen examination

The trophozoites can be found in fresh diarrhea, and the succulent and formed stools are mostly cysts. The faeces can be directly smeared with saline to find trophozoites; after iodine staining, the capsules can be easily identified, zinc sulfate floating method, etc. The concentration method can improve the detection rate of the capsule. The fecal examination should be performed three times and three times. The positive rate of the three tests can be increased to 97%. The duodenal drainage, intestinal mucus or biopsy can be found.

2. Immunological test

Can be divided into two types of detection of serum antibodies and fecal antigens.

(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 have been established in China. Insect culture provides conditions for domestic immunodiagnosis. Enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent antibody assay (IFA) are used to examine patients' serum antibodies. The former can reach 75%-81% positive, and the latter can reach 66.6%~ 90% positive.

(2) Detection of antigen: enzyme-linked immunosorbent assay (double sandwich method), dot enzyme-linked immunosorbent assay (Dot-ELISA), convective immunoelectrophoresis (CIE), etc. detection of antigen in fecal dilution, double sandwich ELISA positive rate 92%, Dot-ELISA can also reach 91.7%, CIE can reach 94%, detection of fecal antigen can be used not only for diagnosis, but also for efficacy.

3. Molecular biology diagnosis

In recent years, polymerase chain reaction (PCR) has been 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. Radioactively labeled chromosomal DNA probes can also be used. The detection of trophozoites and cysts, molecular biology methods with high specific sensitivity, and thus has broad application prospects.

Abdominal B-ultrasound to understand the liver, bile, should be X-ray and ECG.

Diagnosis and identification of giardiasis

The disease according to the patient has diarrhea, abdominal distension, upper abdominal pain or discomfort, fecal odor, and can be found in the general diagnosis of Giardia lamblia is not difficult.

Differential diagnosis should consider amoebic dysentery, bacterial dysentery or other causes of gastroenteritis, abdominal pain, liver hypertonia, liver function impairment, consider cholecystitis, biliary tract infection and viral hepatitis, repeatedly looking for blue Giardia is an important step in identification.

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