Kissing bugs under Triatoma genus were recognized in Vietnam in the past. However, now they tend to live in many localities nationwide and have moved closer to humans, especially in inhabited areas of several major cities such as Hanoi, Da Nang and Ho Chi Minh City. Kissing bugs affect local people’s daily lives, causing health worries when they spread into houses, attack and suck the blood of humans, leaving a swelling or even fever. A few studies have now been done on kissing bugs with scientific data, especially studies about their distribution, biology, epidemiology and relation with humans and domestic animals in Vietnam.
To supplement open scientific materials about kissing bugs and build a foundation for the study of medical responses and the prevention of kissing bugs in Vietnam, Assoc. Prof. Dr. Truong Xuan Lam and scientists from the Institute of Ecology and Biological Resources conducted a study on classification, biology and ecology of kissing bugs under Triatominae genus (Heteroptera: Reduviidae) and its distribution characteristics in Vietnam. The study focused on determining the distribution and habitats of the kissing bugs under Triatominae genus in several representing provinces and cities in Vietnam, and biological and ecological characteristics and the habit of sucking the blood of the Triatoma rubrofasciata species (De Geer).
Kissing bugs copulate and reproduce in Hanoi
The distribution and habitats of kissing bugs in Vietnam
Kissing bugs have been living in 20 provinces and cities in Vietnam, including the popular Triatoma rubrofasciata species. The Triatoma bouvieri species was only found in one province in Vietnam and the Triatoma migrans was only discovered in Ho Chi Minh City. In Hanoi, the T. rubrofasciata species lived in 21 districts in Hanoi. A large number of kissing bugs were caught in the outskirts of Hanoi, especially in Co Nhue commune and Gia Lam district. There were over 1000 individuals per group. Big groups were often collected from June to September every year.
Nymphs, eggs and kissing bugs collected in a nest in Co Nhue commune, Tu Liem district, Hanoi
Kissing bugs' habitat has the same characteristics as living places of humans, especially wet places or wood and goods stores, sharing habitat with mice. These nests are the best environment for T.rubrofasciata kissing bugs to development in egg and nymphs, and grow to scatter and find blood for reproduction.
Creating nest of kissing bugs related to mouse
Study on growth and development of kissing bugs
In the living condition of freeze (temperature: 30 Celusius temperature; humidity: 75 %), life cycle of the T. rubrofasciata kissing bug is 327.56 days. In which, the stages of egg, nymph and pre-adult are 15.76 days, 298.65 days and 13.15 days. Time for laying eggs is from 3 to 32 days. Eggs concentrate from the first to the 16th day of egg-laying and fewer in later days.
In the same living conditions, the natural rate of increase (r) of the T. rubrofasciata kissing bug is 0.012, the natural increasing limited index (λ) = 1.01 of a generation time (Tc) = 337.29 days and a generation multiply rate (Ro) = 41.93. The initial result showed that in natural conditions in a year the kissing bug has only one generation with a high rate of increase.
The growth and development of the kissing bug
The T. rubrofasciata kissing bug is an insect living based on sucking the blood of animals, including humans. It must regularly suck the blood of warm-blooded to live, reproduce and grow. In nature, nymphs and adults directly suck blood from living bodies. When not sucking blood, its trunk closes and arranged near to the breast. When meeting animals, its trunk will stick perpendicular with the animal body and suck blood until being full up. The blood sucking is often consists of two phases. The first phase is fast injection to numb the area. The second phase is blood sucking. Blood sucking time depends on age stages of the kissing bugs.
A kissing bug suck blood of a chicken to live, reproduce and grow
Study about hibernation ability of the kissing bug
Nymphs of the T. rubrofasciata kissing bug in the laboratory have high ability to hibernate without food, for an average of 22.30 – 61.43 days. However, some can last for 114 to 120 days. This property showed the high adaptability of the kissing bugs when they have no food source, allowing them to have long time to find hosts. During these periods, if the kissing bug sucks blood once, it will develop age and maintain reproduction.
Studies about effects on human health when bitten by kissing bugs
The bite by kissing bugs on humans
Kissing bugs living near humans actively bite and suck human blood because they always need food for reproduction and development in both nymphs and adults. The bite after sucking the blood of human are different. A person can have numerous bites caused by one individual blood sucking bug, even up to ten bites. However, bites can be caused by many kissing bugs. Bites can be separated or close to each others. Bites are often red, easily found and are often bigger than bites by mosquitoes and have an interconnecting mark. After being bitten, the bites are often painful, swell on a large scale, have pus and can cause fever, especially for children. In many case, bites on legs and arms can cause the difficulties in movement due to significant swelling. Bites are often on nape, neck, shoulder, back, arms and legs.
Unicellular parasites in the digestive system of the kissing bugs in Hanoi
In initial studies about the unicellular parasites in the digestive system of the kissing bugs, researchers identified unicellular parasites under Trypanosoma genus in the digestive system of the kissing bugs. People penetrated by the kissing bugs will feel tired and sleepy and suffer from high fever. The disease can be chronic, lasting for many years. Clinic manifestation is easily found in heart, brain, esophagus and lungs. Accordingly, the esophagus often stretches and is painful; patients feel pain in the chest, have difficulty swallowing, vomit, have difficulty breathing when inhaling, especially when sleeping. Parasites then attack the brain, causing serious trouble in slumber and leading to coma and possibly death. Living parasites in the digestive system of the kissing bugs were found in highest numbers in Co Nhue and Sai Dong in Long Bien district, respectively accounting for 90% and 80%, followed by Nghia Do, Hoang Cau and Hoang Mai accounting from 61.11 to 70.5% and lowest in the East and De La Thanh Ha, from 56 to 57.4%.
Translated by Tuyet Nhung