Contamination of food by roundworms

作者：admin  点击次数：109  发布时间：2025-04-08

Ascarids lumbricoides in the genus Ascaris parasitizes the small intestine of humans and can also parasitize pigs, dogs, cats and other animals. Ascariasis is a common parasitic disease with a worldwide distribution. It is estimated that there are about 500 million infected people in my country, with a higher infection rate in rural areas than in cities, and higher in children than in adults. 1. Pathogens
Katydids belong to the class Nematoda, the family Ascaridae, and the genus Ascaris. Adults are cylindrical and earthworm-like. They are pink when alive and yellow-white when dead. The size of males is (15~25)cmx(0.2~0.4)cm, and the size of females is (20~35)cmx(0.3~0.6)cm. The fertilized egg is oval, with a size of (45~75)mx(35~50)m. The surface of the egg shell is often covered with a rough and uneven protein membrane, which is brown-yellow due to bile staining. There is a round egg cell inside the egg. The size of unfertilized eggs is (88~94)umx(39~44)mm, irregular in shape, generally oblong, and contains many yolk granules with strong refractive index. Only fertilized eggs can develop. Ascaris eggs are very resistant to various environmental factors. The eggs can survive in the soil for 4~5 years, in pits for 6~12 months, in sewage for 5~8 months, and at -5~-10℃ for 2 years; they can develop normally in 2% formaldehyde solution; 10% white powder solution and 2% NaOH solution cannot kill the eggs; but direct sunlight, high temperature, drying treatment, 20%~30% hot plant ash water, fresh lime water, or 3.5% alkaline water above 60℃ can kill the eggs.
2. Causes and clinical symptoms
The eggs are excreted from the body with feces, and develop into the first stage larvae after about 10 days in an environment with suitable temperature, humidity and sufficient oxygen. After a period of growth and a molt, they become the second stage larvae. It takes a while for the eggs to develop into infective eggs. Once the infective eggs are ingested with food, water, dust, etc., they hatch in the human intestine, drill into the intestinal wall, flow through the liver and heart to the lungs with the blood, then pass through the microvascular wall to the alveoli, and then along the bronchi and trachea to the epiglottis, and are swallowed and develop into adults through the esophagus and stomach in the small intestine. It takes about 2.5 months for people to eat infective eggs and have them excreted in the feces. Adults can lay up to 200,000 eggs per day, and the life span of the worm is generally 1 year. Ascaris eggs contaminate food such as vegetables, fruits and aquatic organisms through dust, water, soil or flies, rats and hands with eggs. People can be infected by eating such foods raw and unwashed. Patients with intestinal ascariasis may have abdominal discomfort or pain in the upper abdomen and around the umbilicus, loss of appetite, hunger, constipation or diarrhea, vomiting, irritability, night teeth, low fever, asthma, urticaria and other symptoms. If the adult worms drill into the bile duct, bile duct ascariasis may occur. If they drill into the gallbladder, liver, tail, glands and other parts, they may cause complications. If they cause intestinal perforation, they may lead to peritonitis. Adult worms may twist each other into a ball, causing intestinal obstruction.
3. Preventive measures Carry out health publicity and education work to enable everyone to develop good hygiene habits, not drink raw water, not eat unclean food, not defecate anywhere, wash hands before and after meals, and children should not play with mud, etc.; improve environmental hygiene, and treat feces harmlessly to achieve the purpose of completely killing the eggs.
(IV) Food contamination by ginger worms
Ginger worms are Fasciolopsis buski, which parasitize the small intestine of humans and pigs. It is more harmful to children and adolescents over 5 years old.
1. Pathogens
Ginger worms belong to the family Fasciolopsis and the genus Fasciolopsis. The fresh worm body is flesh red, large and thick, and the size is (20~75)mmx(8~20)mm. There are one oral sucker and one abdominal sucker. The adult worms attach to the intestinal mucosa with the suckers and are hermaphroditic. The eggs are light yellow, oval, thin-shelled, and the egg cover is small and not obvious. They are the largest eggs among human intestinal worms. Adult worms can lay 15,000 to 25,000 eggs per day.
The eggs enter the water with the feces of the final host (humans and pigs), and hatch after 3 to 7 weeks under suitable conditions. The miracidia move in the water and drill into the body of the intermediate host flat spiral snail when they encounter it. In the snail, the sporocysts, mother red larvae and daughter red larvae develop into cercariae, which continuously escape from the snail and attach to the outer skin of aquatic plants such as water chestnuts, water chestnuts, and lotus roots to form metacercariae. Metacercariae can survive for 1 year in a humid environment, but are prone to death when exposed to dryness. When people eat aquatic plants with metacercariae or chew their skin with their teeth, the metacercariae enter the small intestine through the stomach. In the small intestine, the cyst wall ruptures under the action of intestinal fluid and bile, and the larvae are released from the cyst, attached to the intestinal mucosa of the small intestine, and develop into adults. It takes 1 to 3 months from eating human metacercariae to laying eggs for adults, and the life span of adults is about 2 years. 2. Causes of disease and clinical symptoms
Humans are infected by eating raw aquatic plants contaminated by the metacercariae of the ginger worm. Mild cases are asymptomatic, while more severe cases mainly show abdominal pain, nausea, vomiting, indigestion, frequent diarrhea, anemia, mental fatigue, and some also have ascites and edema. Severe cases may lead to death.
3. Preventive measures Carry out health publicity and education work to popularize the knowledge of preventing and controlling ginger worm disease; change the habit of eating raw aquatic plants; aquatic plants used as pig feed must be harmlessly treated; human and pig feces must be harmlessly treated before application; eliminate flat spiral snails.