Triatominae

The members of Triatominae (trī·ə′täm·ə′nē), a subfamily of Reduviidae, are also known as conenose bugs, kissing bugs or triatomines. Most of the 130 or more species of this subfamily are haematophagous, i.e. feed on vertebrate blood; exceptionally some species feed on other invertebrates (Sandoval et al. 2000, 2004). They are mainly found and widespread in America, with a few species present in Asia, Africa and Australia. These bugs usually share shelter with nesting vertebrates, from which they suck blood. All triatomine species are potential vectors of Chagas disease, but only those species (such as Triatoma infestans and Rhodnius prolixus) that are well adapted to live with humans are considered important vectors of the Chagas disease parasite Trypanosoma cruzi.

The discovery
At the beginning of the 19th century Charles Darwin made one of the first to report the existence of triatomines in America in his Journal and Remarks, commonly known as The Voyage of the Beagle. The following is an extract of what he wrote on 25 March 1835:

There has been considerable medical speculation as to whether or not Darwin's contact with triatomines in Argentina was related to his later bouts of long term illness.

Discovery of triatomines relation with Chagas disease
In 1909 the Brazilian doctor Carlos Chagas discovered that these insects were responsible for the transmission of T. cruzi to many of his patients in Lassance, a village located on the banks of the São Francisco River in Minas Gerais (Brazil). Poor people living there complained of some insects they called barbeiros that bite during the night. Carlos Chagas put his first observations in words: Another Brazilian, Herman Lent, former student of Carlos Chagas, became devoted to the research of the triatomines and together with Peter Wygodzinsky made a revision work of the Triatominae that was published in the Bulletin of the American Museum of Natural History (New York, 163 (3):125-520, figures 1-320), a summary of 40 years of studies on the triatomines up to 1989.

Biological aspects
Triatomines undergo incomplete metamorphosis. A wingless first instar nymph hatches from an egg and passes successively through 2nd, 3rd, 4th and 5th instars. Finally, the fifth instar turns into an adult, acquiring two pair of wings.
 * Cycle:



All triatomine nymph instars and adults are haematophagous and require the stability of a sheltered environment where they aggregate. Most species are associated with wild nesting vertebrates and are named "sylvatic" triatomines. These live in ground burrows with rodents or armadillos, or in tree-dwellings with bats, birds, sloths or opossums. Few species (5%) live in human dwellings or in the surrundings of human houses (peridomicile) in the shelters of domestic animals, these are named "domestic" species. Many sylvatic species are in process of domiciliation ("semidomestic").
 * Ecology:

Most triatomines aggregate in refuges during day and search for blood during night when the host is asleep and the air is cooler. Odors as well as heat guide these insects to the host. Carbon dioxide emanating from breath, as well as ammonia, short chain amines and carboxylic acids from skin, hair and exocrine glands from vertebrate animals, are among the volatiles that attract triatomines. Vision also serves triatomines for orientation. During night, adults of diverse species fly to houses attracted by light.
 * Behavior:

Adults produce a pungent odour (isobutyric acid) when disturbed, and are also capable to produce a particular sound by rubbing the rostrum over a stridulatory sulcus under the head (stridulation).

Domestic and sylvatic species can carry the Chagas parasite to humans and wild mammals; birds are immune to the parasite. T. cruzi transmission is carried mainly from human to human by domestic kissing bugs; from the vertebrate to the bug by blood, and from the bug to the vertebrate by the insect's feces and not by its saliva as occurs in most bloodsucking arthropod vectors such as Malaria mosquitoes.
 * Epidemiology:

Triatomine infestation especially affects unkempt dwellings. One can recognize the presence of triatomines in a house by its feces, exuviae, eggs and individuals themselves. Triatomines characteristically leave 2 kinds of feces like strikes on walls of infected houses; one is white with uric acid, the other is dark (black) containing haem. Whitish or pinkish eggs can be seen in wall crevices. After having had a blood meal the insects sometimes show a limited mobility and can be identified easily.

Tribes, Genera and numbers of described species

 * Alberproseniini
 * Alberprosenia 2
 * Bolboderini
 * Belminus 9
 * Bolbodera 1
 * Microtriatoma 2
 * Parabelminus 2
 * Cavernicolini
 * Cavernicola 2
 * Linshcosteusinii
 * Linshcosteus 6
 * Rhodniini
 * Psammolestes 3
 * Rhodnius 16
 * Triatomini
 * Dipetalogaster 1
 * Eratyrus 2
 * Hermanlentia 1
 * Meccus 6
 * Mepraia 2
 * Nesotriatoma 3
 * Panstrongylus 13
 * Paratriatoma 1
 * Triatoma 67

Note: For a complete list of species see Galvão et al (2004)

Most important vectors
All 138 Triatominae species are potentially able to transmit T. cruzi to humans but the following five species are the most epidemiologically important vectors of Chagas disease.
 * Triatoma infestans
 * Rhodnius prolixus
 * Triatoma dimidiata
 * Triatoma brasiliensis
 * Panstrongylus megistus