Rhodnius nasutus | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Hemiptera |
Suborder: | Heteroptera |
Family: | Reduviidae |
Genus: | Rhodnius |
Species: | R. nasutus |
Binomial name | |
Rhodnius nasutus Stål, 1859 | |
Rhodnius nasutus is a Chagas disease vector native to the northeast of Brazil. [1] It belongs to the family Reduviidae and subfamily Triatominae, which are commonly known as "kissing bugs" or "assassin bugs". [2] They are considered a highly important species concerning the infectious Chagas disease as they carry the parasite Trypanosoma cruzi , that can be transmitted to the blood of mammals, including humans. [3] This disease is an important issue in Brazil and central America due to the large number of Rhodnius species inhabiting these areas, however in recent efforts to reduce human infection, multiple variations of pesticides have dramatically reduced Triatomine populations. [4] Therefore, the understanding and knowledge of Rhodnius nasutus greatly benefits our efforts in reducing life threatening infections.
R. nasutus species are known for their chromatic pattern and range from red to chestnut-colored. [5] These color differences have been hypothesized in many studies to correlate with the species of palm that the insect inhabits. Connection to the coloration of R. nasutus and the colors found on the stems and frond bases of the inhabited palm tree suggests a way of camouflage. [6]
It is important to note that the Rhodnius species are especially hard to decipher from one another as they are morphologically similar, thus taxonomy has been controversial regarding their independence. [7] Accurately identifying R. nasutus from other species with common features plays an important role in reducing human contact with these vectors. Random amplification of polymorphic DNA (RAPD) can identify taxonomic relationships on a molecular level providing valid phylogenetic evidence on speciation. The continuation of this practice is essential for following disease transmission dynamics. [7]
Using mitochondrial DNA sequence analysis, R. nasutus has been dated 66 thousand years, giving rise to stable populations during the Pleistocene-Holocene epochs. [8] This time frame is consistent with the climate change event that took place in South America which marked the end of a major drought and dry season.
R. nasutus is predominantly found in the caatinga biome of Northeast Brazil, although due to increased deforestation and environmental damage the insect has expanded its geographic range and habitat. [9] The species is primarily associated with the Copernicia prunifera palm tree (Carnaúba) in this area, however more recently they have been found colonizing suburban areas such as Jaguaruana, Ceará, and infesting various other palms including Licania rigida (now Microdesmia rigida ) (Oiticica). [1] The allocation of chemical measures in rural areas have pushed these insects to colonize closer to localities and urban districts. [4] Migration into central areas of Brazil pose a threat to humans as it increases the risk of contracting Chagas disease. [9] [10]
When compared to other species of the genera, R. nasutus is found to thrive better in dryer and warmer conditions. [11] Palms located in semi-arid, higher-altitude environments inhabit greater populations compared to palms located in lower elevations where flooding occurs during rainy seasons. [12]
The insect is found predominantly in the crowns of palm trees, they burrow their bodies into the auxiliary nodes and foliar sheaths of palms, which act as a barrier to protect them from environmental and predatory threats. [12]
More recently, R. nasutus has been found infesting homes and farm buildings, including corrals and coops. [13]
In efforts to inhibit human contraction of diseases harbored by R. nasutus, preventative measures such as chemical controls (insecticides) are distributed to high density Triatomine areas, including human dwellings. [14] Although, the continuous re-infestation of homes that had been treated with insecticides presents the need for further research in controlling populations. [15]
The first insecticide used in Brazil to reduce infestations was a synthetic DDT formulation which was later found to have negative impacts on the environment. [14] In 1970, a lindane and dieldrin compound insecticide was used until a safer organophosphorus and carbamate insecticide was formulated in the 1980's. This insecticide however, emitted a strong odor and stained walls of houses undergoing extermination. The favored and most recent insecticide used on R. nasutus is a pyrethroid formula, although the evolution of insecticide resistance has been documented in some Triatomine species. [14]
Biological controls such as the "Mark-Release-Recapture" (MRR) method, involving the placement and evaluation of trace elements in R. nasutus, allows for long-lasting molecular marking under natural conditions. [16] This method aims to identify host-seeking behaviors of the insect by tracking migration and population dispersion. Understanding the movement of these insect vectors provides important information regarding medical insights and preventative measures towards the transmission of Chagas disease. Other biological controls such as dusting and physically marking the insect are not as effective as growing nymphs will eventually shed the marked cuticle. [16]
R. nasutus is a hematophagous insect and will feed on blood through all life stages. [17] Their main hosts are birds and mammals, however there is evidence that these insects will find invertebrates hosts and feed on hemolymph. [12]
Compared to other Rhondius species, R. nasutus displays a slower feeding time around 15-20 minutes before full engorgement. [17] [18] They are solenophagous insects so in order to feed they must find a suitable blood vessel in their host. [18] During the probing period, the maxillae that is pierced into the hosts skin contract in rapid whip-like movements until a blood vessel is detected from which they can feed on. During feeding the cibarial pump, which is connected to strong muscles in the head, regulate the suction and volume intake of bloodmeal through the proboscis. Saliva plays an important role in the probing period to find blood, as well as the feeding period to regulate the flow of blood via the proboscis. R. nasutus has adapted highly efficient salivary glands which reduces the time is takes for them to find blood vessels. [18]
Feeding done by R. nasutus is one of the leading causes of T. cuzi parasites being transmitted to mammals, which leads to Chagas disease. [19] T. cruzi is found in the fecal matter of infected R. nasutus and is transmitted to mammals through the blood stream. While feeding or immediately after feeding, the vector insect will defecate on their host near the pierced skin. If the host disrupts the fecal matter by scratching or any other means of moving the feces around, T. cruzi will be able to get in through the pierced skin where it then spreads disease throughout the bloodstream. [19]
This video shows how the transmission of harmful diseases via T. cruzi is not limited to Latin America and Brazil, but has made its way through other Rhodnius species posing threats to Americans in Tennessee, US.
This video establishes in more detail how T. cruzi gets into the bloodstream and how Chagas disease affects the body.
Chagas disease, also known as American trypanosomiasis, is a tropical parasitic disease caused by Trypanosoma cruzi. It is spread mostly by insects in the subfamily Triatominae, known as "kissing bugs". The symptoms change over the course of the infection. In the early stage, symptoms are typically either not present or mild, and may include fever, swollen lymph nodes, headaches, or swelling at the site of the bite. After four to eight weeks, untreated individuals enter the chronic phase of disease, which in most cases does not result in further symptoms. Up to 45% of people with chronic infections develop heart disease 10–30 years after the initial illness, which can lead to heart failure. Digestive complications, including an enlarged esophagus or an enlarged colon, may also occur in up to 21% of people, and up to 10% of people may experience nerve damage.
The Reduviidae is a large cosmopolitan family of the suborder Heteroptera of the order Hemiptera. Among the Hemiptera and together with the Nabidae almost all species are terrestrial ambush predators; most other predatory Hemiptera are aquatic. The main examples of non-predatory Reduviidae are some blood-sucking ectoparasites in the subfamily Triatominae, with a few species from South America noted for their ability to transmit Chagas disease. Though spectacular exceptions are known, most members of the family are fairly easily recognizable; they have a relatively narrow neck, sturdy build, and formidable curved proboscis. Large specimens should be handled with caution, if at all, because they sometimes defend themselves with a very painful stab from the proboscis.
The members of the Triatominae, a subfamily of the Reduviidae, are also known as conenose bugs, kissing bugs, or vampire bugs. Other local names for them used in the Americas include barbeiros, vinchucas, pitos, chipos and chinches. Most of the 130 or more species of this subfamily feed on vertebrate blood; a very small portion of species feed on invertebrates. They are mainly found and widespread in the Americas, with a few species present in Asia and Africa. These bugs usually share shelter with nesting vertebrates, from which they suck blood. In areas where Chagas disease occurs, all triatomine species are potential vectors of the Chagas disease parasite Trypanosoma cruzi, but only those species that are well adapted to living with humans are considered important vectors. Also, proteins released from their bites have been known to induce anaphylaxis in sensitive and sensitized individuals.
Triatoma infestans, commonly called winchuka or vinchuca in Argentina, Bolivia, Uruguay and Chile, barbeiro in Brazil, chipo in Venezuela and also known as "kissing bug" or "barber bug" in English, is a blood-sucking bug and the most important vector of Trypanosoma cruzi which can lead to Chagas disease. It is widespread in the Southern Cone countries of South America. This region has joined the control intervention called Southern Cone Initiative managed by the PAHO.
Triatoma is a genus of assassin bug in the subfamily Triatominae. The members of Triatoma are blood-sucking insects that can transmit serious diseases, such as Chagas disease. Their saliva may also trigger allergic reactions in sensitive individuals, up to and including severe anaphylactic shock.
The Genus Panstrongylus Berg, 1879 belongs to the subfamily Triatominae. It is found in South America.
Rhodnius is a genus of assassin bugs in the subfamily Triatominae, and is an important vector in the spread of Chagas disease. The Rhodnius species were important models for Sir Vincent Wigglesworth's studies of insect physiology, specifically growth and development.
Dipetalogaster, a genus of Triatominae, the kissing bugs, has only a single species, Dipetalogaster maxima, which is found in the Mexican state of Baja California Sur. Originally the blood-sucking Dipetalogaster lived in crevices in rocks where it typically fed on lizards, but following human growth in its range it now also commonly feeds on humans and domestic animals.
Parabelminus is a genus of bugs in the subfamily Triatominae. The species of this genus could be found in Brazil, specially in Rio de Janeiro and Bahia. It is a vector of Chagas disease.
Panstrogylus geniculatus is a blood-sucking sylvatic insect noted as a putative vector of minor importance in the transmission of Trypanosoma cruzi to humans; this is a parasite, which causes Chagas disease. The insect is described as sylvatic; subsisting primarily in humid forests, and is also known to inhabit vertebrate nesting places such as those of the armadillo, and is also involved in enzootic transmission of T. cruzi to those species. It has wide distribution throughout 16 Latin American countries.
Rhodnius prolixus is the principal triatomine vector of the Chagas parasite due to both its sylvatic and domestic populations in northern South America as well as to its exclusively domestic populations in Central America. It has a wide range of ecotopes, mainly savanna and foothills with an altitude of between 500 and 1,500 metres above sea level and temperatures of 16 to 28 °C. Sylvatic R. prolixus, as virtually all Rhodnius spp., is primarily associated with palm tree habitats and has a wide range of hosts including birds, rodents, marsupials, sloths, and reptiles.
Triatoma nigromaculata is a sylvatic species of insect usually found in hollow trees, in vertebrate nests on trees and occasionally in human dwellings. It usually lives in relatively humid forests at high altitudes on mountain regions and foot hills. As all members of the subfamily Triatominae, T. nigromaculata is a blood-sucking bug and a potential vector of Chagas disease. This species is distributed mainly in Venezuela, but some specimens have also been found in Perú and Colombia (Cauca).
Triatoma brasiliensis is now considered the most important Chagas disease vector in the semiarid areas of northeastern Brazil. T. brasiliensis occurs in 12 Brazilian states, including Maranhão, Piauí, Ceará, Rio Grande do Norte, and Paraíba.
Triatoma rubrovaria is a species of triatomine that is ubiquitous to Uruguay, neighboring parts of northeastern Argentina, and in the southern states of Paraná and Rio Grande do Sul in Brazil. It was earlier reported as T. (triatoma) rubrovaria, a sylvatic species believed to be a highly competent vector of Trypanosoma cruzi, the causative agent of Chagas disease.
Trypanosoma rangeli is a species of hemoflagellate excavate parasites of the genus Trypanosoma. Although infecting a variety of mammalian species in a wide geographical area in Central and South America, this parasite is considered non-pathogenic to these hosts. T. rangeli is transmitted by bite of infected triatomine bugs of the Reduviidae family, commonly known as barbeiro, winchuka(vinchuca), chinche, pito ou chupão.
Triatoma gerstaeckeri is an assassin bug in the genus Triatoma. It is an important vector of Trypanosoma cruzi, the causative agent of Chagas disease. The range of T. gerstaeckeri is from the south-western United States to north-eastern Mexico. T. gerstaeckeri goes through three stages during its paurometabolous life cycle: egg, nymphal instars and adult.
Triatoma indictiva is an arthropod in the assassin bug family of Reduviidae, and is an important vector of Trypanosoma cruzi. T. cruzi is the protozoan that causes Chagas Disease, which affects approximately eight million people a year in the western hemisphere alone. Triatoma indictiva is found in Mexico and throughout the southern United States, including Arizona and Texas.
Panstrongylus megistus is a blood-drinking insect in the subfamily Triatominae. It is found in the Guianas, Brazil, Bolivia, Paraguay, Uruguay and Argentina. It is an important vector of Trypanosoma cruzi, found particularly in Brazil. Besides humans, P. megistus is known to feed on birds, rodents, horses, dogs, opossums and bats.
Triatoma sordida is an assassin bug within the genus Triatoma. This species consists of three subspecies. Also referred to as kissing bugs, T.sordida are most well known for their role as a secondary vector of Chagas Disease. Inhabiting warm, dry climates, T.sordida are widely distributed throughout South America, occupying houses, farming structures, and wild habitats. Pest control is currently focused on insecticide application. However, biological controls utilizing fungi appear promising.
Paleotriatoma metaxytaxa is a species of fossil insect belonging to the subfamily Triatominae of the family Reduviidae. Living kissing bugs are blood-sucking insects responsible for the transmission of Chagas disease. Chagas is a parasitic disease affecting millions of people mainly in South America, Central America and Mexico.