In the past, I lived in the countryside, and there was a disease that made people fearful, that is, "big belly disease", and people who got this disease to a certain extent, whether men, women and children, would have a big belly and lose the ability to work.
Even the most illiterate people in the village know that the disease comes from contact with the river and will warn the children around them not to go around the water to avoid contracting the disease.
Now, I know that this disease, also known as schistosomiasis, is the second most destructive parasitic disease in the socioeconomy, after malaria, and its emergence is related to a water worm, the blood sucker.
Note: Schistosomiasis hugging under an electron microscope
With the trend of urbanization, the population is flowing to the city, and the disease seems to have rarely appeared in our field of vision, but in fact, it is still severe, and hundreds of millions of people are still infected every year.
There are still 800,000 infections in our country, and there are still one to two thousand cases of acute infections every year, but compared to the past, it is indeed much better.
At the time of the founding of New China, countless villages were directly destroyed by this disease, and more than 1362 villages in Jiangxi alone became "ghost villages" directly due to schistosomiasis, and the huge villages could not find a single living person, including some large villages with more than 1,000 households that were directly destroyed, with a cumulative death toll of more than 310,000 people.
Today we will talk about this worm, what is it sacred, why does it have such great power?
What is Schistosomiasis?
Schistosomiasis also has a more written name, Schizoma, which is actually very interesting because it is named directly from the appearance of the bug.
Schistosomiasis is a parasitic worm, but they are hermaphroditic worms, and the male and female exhibit strong amphoteric dimorphism, and the male is much larger than the female, which is very rare in the "worm world" (most parasitic worms are hermaphrodites).
What is even more interesting is the way they survive and reproduce between male and female.
Adult schistosomiasis are between 10 and 20 mm long, and they circulate in the body by sucking the host's blood and transporting the host's hemoglobin through globin.
Note: The green part is female and the brown part is male
Although they are dioecious, the male and female live together, and the male and female insects surround the female insect in their own worm tubes until the female worm reaches adulthood, which is the origin of their name "split body fluke".
In fact, male schistosomiasis and female schistosomiasis are a bit like the relationship of "child brides", the male is responsible for sucking the host, it will transfer part of the nutrients it smokes into the female body, and even some hormones similar to human growth and development are provided by the male - when the male and female hug together, the male will help the female to complete the development.
After the female development is completed, they will begin to lay eggs, their reproductive ability is no longer comparable to these species that we can see with the naked eye, they just hold together and keep breeding, a female worm can lay about 1,000 eggs a day.
However, the "love" between schistosomiasis is not long-lasting, they will also "divorce", females will often leave the male and look for a partner again, but scientists do not think that they are looking for a better "rich and handsome", but to avoid inbreeding, if the blood relationship between male and female schistosomiasis is close, separation is inevitable.
Schistosomiasis is not a separate parasitic human, most birds and mammals are their hosts, and there are several main human beings, including Egyptian schistosomiasis, Schistosomiasis Mansonii, Japanese schistosomiasis, etc. There is only one species in China, that is, Japanese schistosomiasis.
(Digression: Many people hear that the persecution Chinese is called Japanese schistosomiasis, often think that this is brought by the Japanese, in fact, Japanese schistosomiasis is not from Japan, but japanese scholars named it, the earliest record of schistosomiasis in China can be traced back to 2100 years ago. ）
Illustration of Schistosomiasis niger under the microscope
The reproductive phase of hermaphrodites is done in birds and mammals, and when they enter the body and begin to reproduce, they develop schistosomiasis.
The terrible thing is that if left untreated, they will last in our bodies for thirty or forty years, encroaching on the human body but not fatal, which shows how successful their evolution is.
However, it should be mentioned here that the classic feature of schistosomiasis, the large belly, is not directly caused by adult worms, but because a large number of eggs are trapped in the tissue after embolism in organs such as liver, spleen or lungs during the migration of the human body, at this time, fibrotic granulomas will appear around the eggs.
So how does the human body get schistosomiasis?
Schistosomiasis go through several processes in their lifetime, and after adults have completed their reproduction in the human body, their eggs are excreted through urine or feces (whether the route of excretion is urine or feces depends on the type of schistosomiasis).
When these excretory streams into the water body, they begin to hatch and release hairy cymbals, which seek snails, their first host, and for the Japanese schistosomiasis that persecute Chinese, they look for snails.
Hairy lice become tail cymbals inside the snail and are released by snails, at which point they begin to look for the mammals that have sewage as a second host.
When the host is a human, the tail cercaria sticks to the human skin and then penetrates the skin into the blood vessels, a process a bit like being sucked by leeches.
After entering the human body, they will shed their forked tails and become true schistosomiasis. It migrates first to the lungs through venous circulation, then to the heart, and finally to the liver, and when mature, it leaves the liver and enters the intestine through the portal venous system.
Here they lay eggs every day, and once they lay eggs, it is thirty or forty years (the lifespan of schistosomiasis is not generally long), and the eggs are also transported and discharged through the blood circulation system.
Judging from their reproductive capacity, this disease should be difficult to eradicate, how did China manage it decades ago?
In fact, although China was not developed a few decades ago, China is considered to be the best country in the world in the fight against schistosomiasis.
Finally: the three major tactics of new China to treat schistosomiasis
Now in the countryside, those elderly, do not know how to read the villagers basically know what schistosomiasis is, which was the effect of the first major move at that time - to increase the popularization of knowledge on schistosomiasis prevention and control.
As long as everyone understands the way this disease is transmitted, the basic disease will be more than half successful, and the future work can be doubled with half the effort.
Picture note: The intermediate host of schistosomiasis - the light shell nail snail
The second trick is to cut off the intermediate host, and the intermediate host of the Japanese schistosomiasis is the nail snail, so it will often organize personnel to salvage the nail snail, and sometimes even drain the river channel just to remove the nail snail.
The third trick is early detection and early treatment, for high-risk areas, every day there will be medical staff to go door to door to collect excrement, academician Li Lanjuan has also participated in this incident.
Under these three heavy blows, the schistosomiasis known as the "plague god" has almost disappeared in China, from more than 11 million people infected at the founding of the country, and many people have hardly heard of the disease now.
It is indeed remarkable that New China can treat schistosomiasis, after all, it is really too difficult to control such a breeding "machine" as schistosomiasis.