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Triatoma infestans

By Christopher Bonadio

Geographic Range

Triatoma infestans originates from the Cochabamba region of Bolivia, but is found today from central Argentina and Bolivia north to the Brazilian east coast, and the west coast of southern Peru. (Schofield, 1994)

Habitat

Triatoma infestans live in the forests of the Cochabamba region of Bolivia. T. infestans have been found in birds nests, rock piles, hollow trees, rodent dens, and caves in which bats roost. They prefer a warm, tropical climate, and are found most abundantly today in human dwellings and peridomestic habitats like chicken coops, guinea-pig runs, and goat corrals. (Roberts and Janovy, Jr., 2000; Schofield, 1994)

Physical Description

Triatoma infestans are relatively large insects, about 35mm (3.5cm) in length. Their bodies are divided into three major segments: head, thorax, and abdomen. The head is quite elongate and attached to the thorax via a narrow neck. The mouthparts are adapted for piercing and sucking. A three-segmented proboscis arises from the front of the head. Other mouthparts include a reduced labrum and a small posterior pre-oral cavity, or hypopharynx. The labium contains the spined mandibular stylets and maxillary stylets, which together comprise the fascicle, which is used in feeding. The maxillary stylets form both the food and salivary canal. Other head appendages include the shield-shaped clypeus and the anteclypeus as well as segmented antennae used for sensory input. Triatoma infestans have two bulbous, laterally projecting compound eyes with two smaller vestigial eyes behind them called ocelli. The thorax lies between the head and abdomen and is specialized for locomotion. Six legs are attached to the anterior region of the thorax. The legs consist of three segments: the femur (the segment attached to the thorax or abdomen), the tibia, and lastly the tarsus. Forewings called hemielyra are attached basally to the thorax, and lay on the abdomen. The pronotum and the scutellum are the main segments of the thorax. Finally, the abdomen is specialized for reproduction and digestion. Overall body color is brown with yellow and/or red stripes on the abdominal connexivum and the legs. (Roberts and Janovy, Jr., 2000; Schofield, 1994)

  • Range length
    5 to 35 mm
    0.20 to 1.38 in

Development

Triatoma infestans have a hemimetabolous, exopterygote (wings buds develop externally) lifecycle. This means that nymphs, or immature instars, are similar in body form to adults and become more like the adults with each instar; there is no pupal stage. Nymphs pass through five instars and are then sexually mature adults. They hatch after ten to forty days depending on temperature; warmer temperatures promote faster hatching. Soft, pinkish nymphs emerge from the eggs. Their cuticle hardens soon after hatching, and they generally feed on a host within two to three days. If no host is available, a nymph may survive several weeks before actually feeding. Nymphal stages differ from each other in only minor morphological characteristics. The most distinguishing traits among the nymphal stages are the size of the head capsule and the legs. By the fifth and last nymphal stage, the wing pads are clearly visible. (Roberts and Janovy, Jr., 2000; Schofield, 1994)

Reproduction

Adult females of this species copulate several times and can retain sperm for long periods of time. They may lay 100-600 eggs during their three to twelve month lifespan. Adult male reproductive capacity is temperature sensative, and at low temperatures male accessory gland secretion is reduced, and eggs tend to remain unfertilized.

Mating involves a complex, courtship behavior. Males may be vigilant or indifferent to the female while females may advance males or be non-receptive. A courting session may last ten minutes, but in one study only one out of ten mate encounters were completed. Overall nine steps have been observed in T. infestans mating behavior. Males and females separate after copulation. (Askew, 1971; Flores and Lazzari, 1996; Lazzari and Nunez, 1989; Roberts and Janovy, Jr., 2000; Schofield, 1994)

Eggs are laid in small clumps in arboreal environments or they lay loosely in more subterranean environments. Egg-laying follows a circadian periodicity which commences ten to twenty days after copulation. They hatch after ten to forty days depending on temperature. Warmer temperatures promote faster hatching. Although bloodmeals are important for egg production, the female adults can lay eggs without feeding, as long as the nymphs have consumed sufficient bloodmeals. Adults are free living and sexually reproducing.

Two generations of egg development may be completed per year in warmer climates, but only one generation is completed in colder climates. (Roberts and Janovy, Jr., 2000; Schofield, 1994)

  • Range eggs per season
    100 to 600

Lifespan/Longevity

  • Typical lifespan
    Status: wild
    3 to 12 months

Behavior

Peak adult emergence is in the summer between December and January. When defending itself against predators, kissing bugs may rub the rigid tip of the rostrum against a series of ridges on the ventral surface of the thorax resulting in a squeaking sound. (Askew, 1971; Flores and Lazzari, 1996; Lazzari and Nunez, 1989; Roberts and Janovy, Jr., 2000; Schofield, 1994)

Communication and Perception

There are a number of temperature receptors on the antennae that detect thermal heat radiating from a host. Thermal cues may also indicate places for laying eggs. When feeling threatened, kissing bugs may rub the rigid tip of the rostrum against a series of ridges on the ventral surface of the thorax resulting in a squeaking sound. This is called stridulation. (Askew, 1971; Flores and Lazzari, 1996; Lazzari and Nunez, 1989; Roberts and Janovy, Jr., 2000; Schofield, 1994)

Food Habits

Triatoma infestans are haematophagous meaning that they feed on blood. Specifically, they are solenophages or vessel feeders. They search for whole blood vessels in their host's skin tissue from which to feed. Overall, T. infestans requires at least one large blood meal consisting of one to two grams of blood during development. Females may ingest ten grams more during their reproductive phase. Triatoma infestans feed on mammals. They primarily survive off of marsupials, rodents, and humans. The kissing bug relies on contact chemoreceptors located within the stylet food canal. When hungry, these insects will probe any warm surface by sampling fluid underlying surface tissues. They will continue feeding if the fluid contains a recognizable engorgement factor, or rich in high-energy nucleotides. The mandibular and maxillary stylets are involved in the process of blood consumption. The mandibular stylets pierce the host integument, allowing the maxillary stylets to probe and lacerate blood vessels. Saliva is injected and acts as an anticoagulant to permit the free flow of blood throughout feeding. Typical bloodmeal digestion in adult T. infestans lasts about fourteen days. Since kissing bugs feed solely on blood they have acquired an adaptation for obtaining essential vitamins. Cells called mycetomes carry yeast-like organisms, which synthesize essential vitamins. Nymphs feed on the same hosts as adults, and usually consume eight to nine times their weight in blood. (Askew, 1971; Schofield, 1994)

  • Animal Foods
  • blood

Economic Importance for Humans: Positive

There is no known positive economic importance of Triatoma infestans.

Economic Importance for Humans: Negative

Triatoma infestans is and active vector of Trypanosoma cruzi , a parasitic trypanosome protozoan. Trypanosoma cruzi causes Chagas disease, a deadly disease that may result in irreversible damage to the nervous system, muscle tissue, and the heart, eventually causing death. Chagas disease is a zoonosis, a disease of animals that is transmitted to humans or other animals. Trypanosoma cruzi is transmitted to humans via the feces of the kissing bug. The insect acquires the protozoan from an infected mammal and retains it for life. After the bug defecates during or after feeding, the trypanosome may penetrate the wound left by the feeding insect. Multiplication of the protozoan parasite in local tissue cells follow quickly it has gained entrance to a host body. The protozoan undergo multiplies by binary fission. During its developmental stages, T. cruzi changes in size and shape. In mammalian cells, the parasite is initially a small, unflagellated amastigote, which multiplies by binary fission into a flagellated trypomastigote. These are released throughout the blood stream when the cell ruptures. If removed from the mammal by a feeding kissing bug, the tryopmastigote changes into a epimastigote, eventually forming highly infective and active metacyclic trypomastigotes. Other endosymbionts within the gut of T. infestans function as a trypanosoma maturing factor that is essential for the differentiation of T. cruzi. Trypanosoma cruzi can survive within a dead host for long periods of time. Triatoma infestans is usually not hurt by the protozoan parasite, however, T. cruzi may have a suppressive effect on the insect's haemocoelic immune system. In 1993, sixteen to eighteen million people were infected by Chagas disease and ninety million were at risk -about 4% of the entire population of Latin America. It is the third most important cause of disability from a parasitic disease after malaria and schistosomiasis. In Latin America (as of 1993), it is the fourth most frequent cause of death. Medication can be quite expensive, and many individuals who have Chagas disease lose their jobs and can not find new jobs. Triatoma infestans infestations are often a cause for social embarrassment and considered a symptom of poverty. (Ciojalas and Catala, 1993; Hypsa, 1993; Roberts and Janovy, Jr., 2000; Schofield, 1994)

  • Negative Impacts
  • injures humans
    • bites or stings
    • carries human disease

Conservation Status

Triatoma infestans do not require any special conservation status for Triatoma infestans.

Other Comments

Dr. C. J. Schofield created the "Southern Cone Initiative" for the elimination of T. infestans from domestic environments. Part of this elimiation program includes improvement in floors and house foundations, walls, roofs, and the removal of domestic animals from homes. One other aspect of this program is greater civilian awareness of infestation problems and prevention. Medicine such as amodiorone, a drug used to prevent cardiac arythmias, may also help prevent death from Chagas disease. Insecticides, such as synthetic pyrethroids, have been successful eradicators of T. infestans.

The bite of some other members of the family Reduviidae are excruciatingly painful. One Asian species was used by the Emir of Bokhara to torture prisoners. The bugs were kept in a pit into which prisoners and raw meat were thrown. The pain from the bite was mainly due to a toxin in the saliva.

Trypanosoma cruzi can be transferred by blood transfusion or via organ transplant. This protozoan parasite may cross the placenta from an infected mother to her fetus. (Askew, 1971; Schofield, 1994; Askew, 1971; Schofield, 1994; Askew, 1971; Schofield, 1994)

Contributors

Sara Diamond (editor), Animal Diversity Web.

Christopher Bonadio (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

infrared/heat

(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.

internal fertilization

fertilization takes place within the female's body

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sanguivore

an animal that mainly eats blood

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

suburban

living in residential areas on the outskirts of large cities or towns.

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

Askew, R. 1971. Parasitic insects. New York: American Elsevier Publishing Co., Inc..

Ciojalas, L., S. Catala. 1993. Changes in Triatoma infestans reproduction efficiency caused by suboptimal temperature. J. of Insect Physiology, 39: 297-302.

Flores, G., C. Lazzari. 1996. The role of antennae in Triatoma infestans: orientation towards thermal sources. J. of Insect Physiology, 42: 433-440.

Hypsa, V. 1993. Endocytobionts of Triatoma infestan: Distribution and Transmission. J. Invertebr. Pathol., 61: 32-38.

Lazzari, C., J. Nunez. 1989. The response to radiant heat and the estimation of the temperature of distant sources in Triatoma infestans. J. of Insect Physiology, 35: 525-529.

Roberts, L., J. Janovy, Jr.. 2000. Foundations of Parasitology (6th ed.). New York: McGraw-Hill.

Schofield, C. 1994. Triatominae: Biology and Control. West Sussex: Eurocommunica Publications.

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