roundworm
Although human beings are exposed to a large number of microorganisms and eggs every day, many microorganisms and eggs will be eroded by gastric acid because of its strong acidity, and they will lose their activity and cannot infect human beings.
However, roundworms are an exception. Their eggs can resist the erosion of human stomach acid and reach the intestine. Eggs will hatch into larvae in the small intestine and hide in the small intestine to steal food that has not been fully digested by human beings, leading to emaciation and malnutrition.
Larvae develop into adults in the small intestine, where females will lay eggs. Ascaris eggs enter the external environment with feces, which leads to Ascaris infection through feces contact, so Ascaris is an infectious disease.
Let's talk more here. Fecal mouth transmission does not mean that human beings directly contact feces and then contact the mouth. But when feces come into contact with food or water, when these contaminated food and water enter the human body again, human beings will be infected with ascariasis.
In the past, the living conditions in rural areas were poor, and many people used human excrement as organic matter to fertilize agricultural products, which led to the pollution of agricultural products by ascaris.
Eating these contaminated foods without thorough cleaning will lead to ascaris infection. If infected with ascaris lumbricoides is not treated, it is likely to lead to malnutrition, cough and fever, and even severe intestinal obstruction, leading to a decline in quality of life.
However, the treatment of ascariasis is relatively simple, and a little pesticide can cure it. But if you don't pay attention to hygiene, you may continue to be infected with ascaris lumbricoides.
(Insect repellent Baota sugar)
Why are there so few roundworms now?
I once heard a story. After a medical student found out that he had ascaris, the teacher who taught infectious diseases was very happy and told him not to take medicine in a hurry. He could donate feces and provide fresh ascaris specimens. This is because the ascaris specimen in the classroom has not been updated for nearly 10 years.
This story also shows that the incidence of roundworm is very low at present. In a short period of 10 years, what have we done right to control the spread of ascaris lumbricoides?
Generally speaking, the spread of infectious diseases to others requires three steps: the source of infection, the route of transmission and the susceptible population. The reason why we control the transmission of ascaris lumbricoides is because we cut off the transmission route of ascaris lumbricoides.
In the past, there was no running water in many rural areas, so it was inconvenient to use water. Therefore, personal hygiene work such as washing hands before and after meals is not done well enough, which gives ascaris a chance to spread.
Now, even in remote mountainous areas, tap water is installed. The popularization of compulsory education makes more rural people realize the importance of personal hygiene, which makes ascaris eggs have little chance to enter the human body, so the infection rate will drop until it disappears completely.
Changes of parasites
In addition to roundworms, fleas and lice, which were common in rural areas before, also lost their living space, and the incidence rate among the population became lower and lower, or even disappeared completely.
In the past, the reason why parasites were rampant in rural areas was partly due to the intensive contact between people and animals in the past, in addition to personal hygiene.
In the past, pigs were directly raised in the corner of their own yard, and the excrement discharged by pigs could not be cleaned up in time, which led to the pollution of human living space by animal excrement, so that some parasites would be transferred from animals to humans, the most common being fleas.
At present, some rural areas prohibit families from raising livestock, and some places have installed sewers, which can clean up animal feces in time, cut off the source of infection to a certain extent, and lead to a decrease in the infection rate of parasites, so there are fewer and fewer roundworms, lice and fleas now.
abstract
In fact, the present countryside is very different from the past. In the past, due to imperfect living facilities, mixed living of people and animals, personal hygiene and other conditions, it was easy to come into contact with various parasites. At present, the conditions in many rural areas are comparable to those in cities, which makes parasites lose their living conditions, so the infection rate of ascaris lumbricoides is getting lower and lower until it becomes a rare disease.