People in certain Ho Chi Minh City areas are having sleepless nights worrying about a leech invasion after an enterprise buying them to send to China moved suddenly last month, leaving thousands of the hardy worms behind.
With the traders offering very good prices, people in different localities were attracted to the business of supplying the bloodsuckers, raising concerns that the sudden increase in the parasitic creatures numbers will upset the balance of local ecosystems and threaten the life of other creatures, including people.
The business started almost two years ago and boomed from the middle of this year.
Several Chinese dealers had asked local people to join in the trade by supplying the blood-sucking worms.
In Hoc Mon, sacks of leeches had been brought at night to a house for VND80,000-150,000 (US$7.14) a kilogram. The house was rented by a Chinese man and his Vietnamese wife Kim Anh.
The business soon attracted people in provinces neighboring the city like Tay Ninh, who bred leeches in their own ponds to sell.
Since the business moved to another district in mid October, all the leeches left behind started to multiply at a flooded field nearby. The field has an area of about 3,000 square meters.
A local named Thanh said several suppliers were not informed of the move. A supplier had sent a sack of leeches there and the driver just threw it into the field, finding that the buyer was not there.
The leeches in the field are now as big as an adult's thumb, according to local reports.
Parents are worried as around 800 children visit a nearby kindergarten every day.
Some people who rented houses in the area have moved.
Residents say they have been complaining about the leeches to local authorities, but no action has been taken
In many northern and central provinces, where one leech is bought at VND10,000 (nearly $50 cents) and dried leeches for VND1.5 million a kilo, people have even planned to build leech farms.
It is believed that the leeches are being taken to China for use in making medicines.
However, when the buyers move from time to time, like in Hoc Mon District, leaving large populations of leeches are left behind.
Dang Huy Huynh, chairman of the Vietnam Zoology Association, said the situation can be a "disaster."
Huynh said leeches in natural environment grow and die at an normal rate.
"But when people raise leeches, they will grow to a number beyond the ecosystem's capacity," he said.
Bui Quang Te, an aquaculture expert, expressed similar concerns about the unusually large leech population.
"The leeches will suck the blood of other creatures in the same environment," Te was cited as saying by news website VnExpress in a Friday report.
He said the worms can also spread infectious diseases between animals and people.
Some experts have suggested destroying the leeches by burning or burying them in lime.
Scientists said it's hard to say what the leeches are wanted for in China.
But it is similar to Chinese businessmen seeking Vietnam's rare precious trees like sua, (Dalbergia tonkinensis prain), or buying all cats in Vietnam villages in the 1990s, which was followed by farmers struggling to deal with a burgeoning mice population, Huynh said.
The situation should also remind people of the yellow snails disaster in the 1990s, scientists warned.
Known in Vietnam as oc buou vang, the snails were imported first in 1975 from South America, as a kind of food.
They were Vietnam's first and biggest lesson in the import of harmful foreign species, after the snails went on to become the nemesis of rice and water spinach crops.