Dr. Truong Xuan Lam at the Institute of Ecology and Biological Resources examines a kissing bug. Photo courtesy of khoahoc.com.vn
Kissing bugs, so called because they tend to bite (and defecate) on the victims' faces and lips, are moving from the jungle into residential areas in Vietnam in large numbers.
They play a vector for Trypanosoma cruzi, a parasitic single-cell organism causing several diseases in vertebrates including Chagas that is responsible for 21,000 deaths per year, mainly in Latin America. In fact, Chagas has been called the region's HIV/AIDS epidemic in waiting.
The bugs are propagating at a fast rate and Vietnam government has not prepared the public for what can be a calamitous development, scientists said at a conference in Hanoi last week.
Scientists have concerned about the "massive presence" of the bloodsucking insect in Vietnam as well as Thailand, the Philippines and France, after one species, Triatoma rubrofasciata, migrated outside Latin America a few centuries ago.
"It probably uses maritime and fluvial transportation facilities, thank to its association with rats," says a press release handed out at the conference.
Surveys by Vietnam Institute of Ecology and Biological Resources over the past two years have confirmed the presence of a large group of the migrating species in at least 20 cities and provinces, including major localities like Hanoi, Ho Chi Minh City, Da Nang and Hue.
The insect was detected at 121 spots on 31 out of 36 streets in downtown Hanoi, with between 15 and 30 reappearances at some spots, Saigon Tiep Thi reported, citing studies released at the conference.
Pham Thi Khoa of the National Institute of Malariology, Parasitology and Entomology said the bugs used to gather in northern mountainous areas but have now come down to cities, and been found even in skyscrapers.
"That is a noticeable change," Khoa said.
She said analyses will be done to compare the bugs in jungle areas with those in the cities.
The doctor also found out by chance the insect's high birth rate compared to others after bringing one to her lab.
"I didn't think it would give birth. But in seven months, until it died, it produced 327 offspring," Khoa told Saigon Tiep Thi on the sidelines of the conference.
"The species reproduces all year round"¦ It lays eggs even as it sucks blood."
Khoa said summer until the end of fall is the best time for the insect to grow and multiply.
She said she has tried killing the bugs with normal insecticides but they have not worked.
She guessed that the overuse of pesticides and other chemicals in agriculture have led to abnormal development of some species, strengthening harmful creatures and killing their natural predators.
Kissing bugs' natural predators include moles, a burrowing animal.
Scientists at the conference said Vietnam needs a specialized agency that will study and control the bugs so as to avoid possible outbreaks and prevent them from spreading to other countries.
Jun Nakagawa, representative of the World Health Organization for the Western Pacific region, said at the conference that Chagas is considered a Latin American problem but it is actually growing into a global one due to increasing international travel.
He said, cited by news website VnExpress, that the disease has been reported in 19 countries outside Latin America including Japan and Australia, calling for more research and attention to fight it.
Scientists said the disease can develop 10 to 20 years after infection, damaging internal organs including the heart, the esophagus, the colon and the peripheral nervous system. Affected people may die of heart failure.
Truong Xuan Lam, an entomologist at the Institute of Ecology and Biological Resources, who was first to study the bugs in Vietnam, said the country has not reported any Chagas infection, but that is not because there has been no case, but because a proper examination kit is not available.
Many people bitten by the bugs in Vietnam have developed a fever and needed hospitalization.
"The bites can be very painful and cause widespread allergy," Lam said, noting that more people have reported catching the bugs at home of late, mostly in the bedroom. They hide during the day and come out at night.
He said around 2,000 victims of the bites in Vietnam are being medically followed, but this only involves making phone calls to keep track of their health. It was not a proper scientific study, he said.
Single-cell organisms of the Trypanosoma genus have been found in the digestive tract of kissing bugs caught in Vietnam, Lam said.
He said more work is needed to find out about the growth and epidemiological threats that the organisms present.
"Studies on kissing bugs in Vietnam are at zero point, with very few and small works, mostly on their habitats."
He said the studies have stopped at being descriptive and findings that the bugs bite more children than adults and that they are usually found around rats.
Scientists are also concerned about the threats of the bugs passing diseases from rats to humans. Despite being an insectivore, the rodent appears to be the bug's main source of blood supply.
The bug thrives in areas with large rat populations, and 85 percent of 200 kissing bugs tested in Vietnam had rat blood in their digestive tract while 7.5 percent had both human and rat blood.
Khoa said she and a group of foreign scientists had also found bacteria in some bugs' blood during a recent field trip. The blood samples will be tested overseas to identify the bacteria, using principal component analysis (PCA), which is not currently available in Vietnam.
She said "unhygienic" places around homes like duck ponds, chicken coops, and piles of firewood are a "convenient environment" for the insect to grow.
She said the public needs better information about the insect and the harm it can cause. Some families found the bugs but thought they were cockroaches, and only found out different after they were bitten.
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