Successful fight waged against waterborne killer

Many people enjoy running or walking along the picturesque banks of the Yangtze River in Nanjing's Pukou district, attracted by spacious areas of greenery, countless willow trees and fresh breezes.

However, if they want to swim or wade in the river, they will be stopped by Yang Wenrong and his colleagues.

A member of the district's control center for schistosomiasis, a disease caused by parasitic worms, Yang's daily work involves patrolling the river banks to prevent people becoming infected.

Commonly known in China as "blood-sucking worms", the parasites can penetrate the skin within 10 seconds.

Yang said: "Many people like to play in the water, but on numerous stretches of the Yangtze, this is not safe. Contact with the water should be avoided, especially on warm and hot days. Even those who have to work on the river, such as flood control employees, must wear protective clothing and rubber gloves."

Schistosomiasis, which infects humans and animals, can cause fever, diarrhea and an enlarged liver, among other conditions. Without proper treatment, it may result in death.

The worms lay eggs inside the body, which are later excreted. Eggs that come into contact with water hatch into a larva known as miracidia, which later invades its sole intermediate hosts－oncomelania, or freshwater snails－before developing cercariae, a free-swimming larva.

Once humans or animals come into contact with water containing cercariae, they are infected with schistosomiasis. The parasites will continue to produce numerous eggs, harming the liver and spleen.

Many patients with the disease experience distended stomachs, as they accumulate fluid in the peritoneal cavity, the fluid-filled gap between the walls of the abdomen and organs contained within the abdomen. In advanced cases, women who are infected become infertile and children experience dwarfism－short stature resulting from a genetic or medical condition.

Chinese have been battling the disease for more than 2,000 years. In 1971, in Changsha, Hunan province, the body of a female was unearthed at a tomb used during the Western Han Dynasty (206 BC-AD 24). Scientists later found the eggs of a parasitic flatworm known as a schistosome in the body.

In 1905, in the first confirmed case of schistosomiasis in China, schistosome eggs were found in the feces of a farmer in Changde county, Hunan.

Up to the 1950s, the disease was prevalent in 350 counties across 12 provinces and municipalities in China, including Shanghai, Jiangsu and Zhejiang. More than 10 million people were infected and over 100 million were exposed to it.

Stricken soldiers

In 1949, when the People's Republic of China was founded, the country started to battle the disease.

In May that year, after the PLA liberated Shanghai, the 9th Corps of the 3rd Field Army, stationed in the Shanghai suburbs of Songjiang and Jiading, were training for the battle to liberate Taiwan.

However, after exercises held in water, many of the 100,000 troops became infected with schistosomiasis and developed rashes, fever and diarrhea.

With the help of a Chinese researcher who graduated in the United Kingdom, a schistosomiasis control committee was quickly established in suburban Shanghai. In December 1949, more than 2,000 medical workers and students from hospitals and medical colleges in the city joined the committee to treat the soldiers.

According to the Jiangsu Institute of Parasitic Diseases, since the 1950s, the province has had more than 2.53 million patients with schistosomiasis. Four of 10 counties nationwide with the most serious infections were in Jiangsu.

At the time, the disease wiped out the populations of several villages in Kunshan, a county in Suzhou. In 1955, during medical checkups for military conscription, 85.5 percent of the young men examined were found to be infected with schistosomiasis. In 1956, the county was exempted from military duty for seven consecutive years.

In Xinming village, Gaoyou county, Jiangsu, a total of 4,019 of the 5,257 residents were infected with the disease in 1950, with 1,335 dying in less than six months.

In the two decades from 1950, Rentun village in Shanghai was known as a "ghost village", as half the population had died from the disease. It claimed the members of 121 families and infected 97 percent of the 461 people who were previously healthy. No babies were born in the village for more than seven years.

In 1953, Shen Junru, the first president of the Supreme People's Court, wrote to Chairman Mao Zedong, informing him of the prevalence of schistosomiasis in provinces on the lower reaches of the Yangtze River. As a result, a systematic and effective national battle was launched against the disease.

A central prevention and control team, led by Ke Qingshi, the Shanghai Party secretary, was formed in 1955. Numerous teams were later established in counties, cities and provinces to treat patients and control the disease.

In Wuxi, Jiangsu, Li Wei, head of the general office of the Jiangsu Institute of Parasitic Diseases, said many medical workers have devoted their lives to preventing and controlling schistosomiasis.

"This work has not been easy. The workers have been sent to remote areas, educating locals and combining with them to eliminate schistosomiasis. In the 1960s, some 60 percent of researchers from the institute were sent to Kunshan. They spent at least six months there every year," Li said.

"In the 1970s, researchers were sent to cities along the Yangtze to work with farmers to eliminate oncomelania (freshwater snails) on the river beaches. Inevitably, after many hours in the water, they became infected with schistosomiasis, but they went back into the water after receiving treatment."

Medical workers initially focused on saving patients who were critically ill. However, although the medicine used at the time was effective for treating schistosomiasis, it could also affect heart function.

With researchers' efforts, more effective and safer drugs from foreign countries were introduced and surgeons began to tend to patients in critical condition.

Preventing feces containing schistosome eggs from entering water was central to preventing the disease. At the time, many toilets in rural areas were not hygienic and feces were used to fertilize crops. The eggs could easily spread and pollute soil and water.

Medical workers talked to farmers, asking them not to wash in rivers or use feces as fertilizers. They set up hygienic toilets, told farmers not to drink unpurified water, and cattle were prevented from coming into contact with polluted water.

For farmers who had to grow rice or wash in river water, the researchers made protective coverings to prevent cercariae penetrating the skin.

Eliminating the freshwater snails was also crucial for prevention work, but they multiplied quickly in provinces and municipalities in East and South China.

Although the task seemed impossible, medical workers in infected areas combed all the rivers, ponds and lakes to detect the snails.

They drugged them, reinforced river banks with stones and cement to prevent the snails entering the water, and also buried them in dry soil. After being buried for three months, the number of snails fell by nearly 75 percent.

The disease now can be cured in three days through use of the synthetic drug praziquantel.

After decades of hard work, remarkable progress was made in many areas. In 1985, Shanghai announced that schistosomiasis had been eradicated in the city, while nationwide, the number of patients with the disease fell from more than 11 million in the 1950s to 840,000 in 2004.

Final cases

In Jiangsu, the last two cows were detected with schistosomiasis in 2007, the final acute case was reported the following year, and the last positive case resulting from a stool examination was recorded in 2012, according to the Jiangsu Institute of Parasitic Diseases.

In 2018, data from the national schistosomiasis prevention and control system and 453 national surveillance sites for the disease showed that five of the 12 provinces and municipalities that used to be vulnerable had made significant progress toward eliminating it. Six provinces had controlled transmission of the disease, and the transmission chain was successfully broken in Sichuan.

Also in 2018, no cases of acute schistosomiasis were reported in China.

With their experience in preventing and controlling the disease, Chinese medical workers have been contacted by other countries troubled by infections.

Schistosomiasis is prevalent in 78 countries and regions worldwide, 85 percent of them in sub-Saharan Africa.

Yang Kun, deputy director of the Jiangsu Institute of Parasitic Diseases, said it has held 59 courses to train 1,718 medical professionals from 71 developing countries in Asia, Africa and Latin America.

"In 2017, we participated in the China-Zanzibar schistosomiasis control and elimination project to help local people fight the disease. This was China's first public health program overseas," he said.

In 2013 and 2014, experts from the World Health Organization and China visited Zanzibar several times to assess the feasibility of such a project.

A memorandum of understanding on jointly controlling the disease was signed by the three sides in 2014, and two years later, the Jiangsu institute began work on the project.

"During the following three years, six groups of Chinese experts worked in Zanzibar, sharing their experience with local doctors and residents," Yang said.

"We held lectures for local medical workers, provided medicine and worked with many government organizations to improve awareness of schistosomiasis prevention."

In three years, the schistosomiasis infection rate on Pemba Island, Zanzibar, fell from 8.92 percent to 0.64 percent, Yang said.

"Our work was praised highly by the WHO and the president of Zanzibar asked us to cooperate further in controlling the disease," he added.

"We also offer medical services to some countries taking part in the Belt and Road Initiative to help local people and Chinese working in these nations."