Hematophagy — an overview, ScienceDirect Topics


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Volume 2


Hematophagy is a feeding behavior that has been adopted by many invertebrates, including some insects and arachnids. It is thought to have evolved independently in many different lineages and is often accompanied by specific adaptations of mouthparts for biting and sucking. Blood feeding arthropods can be regarded as ectoparasites that feed on the blood of their hosts when they are in temporary contact with them (such as mosquitoes, sandflies, tsetse flies, blackflies, tabanids and blood feeding bugs), in permanent contact (such as lice, sheep ked and tungid flies) or in periodic contact (such as fleas and ticks). Many only feed on blood during one phase (often the adult female), whilst others feed on blood throughout their life cycle.

There are two major strategies associated with the acquisition of a blood meal, namely; pool feeding, where biting mouthparts cut open superficial blood vessels and feeding occurs on blood that leaks out to the surface of the host, and piercing and sucking, where specialized mouthparts are inserted into the skin and blood vessels are severed or cannulated. During these feeding events, organisms present in the host blood or superficial skin layers may be imbibed inadvertently. Many of these parasitic organisms continue their life cycles within the arthropod and are transmitted back to another vertebrate host during a future blood feeding episode. Hematophagous arthropods thus act as vectors of parasites and pathogen, including many of medical and veterinary importance. Because of this they are indirectly responsible for tremendous suffering and economic loss.

Fossil Parasites

Christina Nagler, Joachim T. Haug, in Advances in Parasitology , 2015

8.2 Phylogenetic inference of appearance and molecular estimations of early evolution

Throughout their evolution sand flies and parasitic organisms likely have coevolved. Due to their haematophagy parasitic diseases are likely as old as the sand flies themselves ( Azar and Nel, 2003 ). Thus the protozoan parasites should have originated at least in the Early Cretaceous, 140 ma, together with species of Ceratopogonidae as their ancient vectors ( Pérez-de la Fuente et al., 2011; Poinar, 2008a ).

The association of hemipterans and trypanosomas originated at a similar time, in the Middle Caenozoic, supposedly with bats as primary hosts ( Otalora-Luna et al., 2015; Poinar, 2005c ). Similar parasites that were vectored by sand flies have been proposed to have contributed to the extinction of the dinosaurs ( Azar and Nel, 2003 ). The similarity of fossil and extant and fossil trypanosomes has been seen as a strong indication for haematophagy in the past ( Poinar, 2004a; Greenwalt et al., 2013 ).

The interaction between wolbachians and insects is stable at least since 100 million years according to some molecular studies ( Cerveau et al., 2011 ).

The recent discovery of Arsenophonus, a c-proteobacterium, probably played an important role in the evolution of bat flies and louse flies for the development of their true ectoparasitism, at least 20 ma ( Duron et al., 2014 ).

Current research on phytopathogens transmitted via insects sheds new light on their evolution. The traditional role of insects might have evolved over a transitional stage, where the insect served as vector and host, to the final form with the insect as host. Thus phytopathogenic bacteria evolved to become insectopathogenic bacteria ( Nadarasah and Stavrinides, 2011 ).

Different insect-borne viruses, which are viruses transmitted by insects, have been considered to exist for at least 100 million years. These may have coevolved with certain species of Diptera (Psychodidae and Culicomorpha) since the Early Cretaceous, thus providing an evolutionary path for vertebrate infections ( Poinar and Poinar, 2005 ). The long relationship of parasites and insects indicates a coevolutionary mechanism ( Czosnek et al., 2001 ).

Arthropod Vectors of Medical Importance

Jean-Michel Berenger, Philippe Parola, in Infectious Diseases (Fourth Edition) , 2017

Triatominae 35

Among the predaceous bugs Reduviidae (Assassin Bugs), one subfamily, the Triatominae, has evolved to hematophagy . Triatominae are composed of 14 genera and 140 species, inhabiting the Americas from southern Argentina to the Mid-USA. 36 One genus, Linshcosteus, is distributed in India and one species, Triatoma rubrofasciata, associated with rats, migrates with ships and is now distributed to all main tropical ports. Three genera in particular are of medical importance: Triatoma, Rhodnius and Panstrongylus. Triatoma infestans, Rhodnius prolixus ( Figure 12-11 ) and Panstrongylus megistus are domesticated species; they live in houses with people and accomplish their complete biological cycle in this environment.

Figure 12-11 . Female Rhodnius prolixus. Note the elongated head.

Triatominae present a diversity of body size from 5 to 40 mm but the main species are around 20 mm. The head is elongated, with a long and straight rostrum folded under the head. They possess wings, and are black and brown in color; sometimes they show bright colors (red, yellow). The biological cycle comprises eggs, oval or rounded ( Figure 12-12 ), five young stages similar to adult but without wings, and adults (with females larger than males). They bite people during sleep and take a blood meal.

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Figure 12-12 . Eggs of Triatoma infestans. Note the pink colour of some eggs indicating they are near hatching.

Triatominae can transmit a protozoan, Trypanosoma cruzi, the agent of Chagas disease. The trypanosomes live in the gut of Triatominae and they are evacuated with the feces on the skin of humans. Indirect transmission occurs when people scratch the skin, introducing feces into the bite wound. Other ways of inoculation are via the mucous membranes (eyes, for example), blood transfusion, organ donation and food contamination. 37 The reservoirs of the parasite are mammals. Trypanosoma cruzi is responsible for Chagas disease (see Chapter 124 ). 38 Infection can stay in a chronic phase without symptoms for a long time, and in this case humans may also act as reservoirs. In 2008, the World Health Organization estimated that there were >25 million people exposed to Chagas disease in South and Central America.

All countries of South and Central America have begun programs to fight Triatominae and Chagas disease (Southern Cone Initiative) since the 1990s. This program comprises use of insecticides in villages, education to increase the knowledge of the problem in the population and detection in blood donors.

Gene Expression Studies in Mosquitoes

Xiao-Guang Chen, . Anthony A. James, in Advances in Genetics , 2008


Research on gene expression in mosquitoes is motivated by both basic and applied interests. Studies of genes involved in hematophagy , reproduction, olfaction, and immune responses reveal an exquisite confluence of biological adaptations that result in these highly-successful life forms. The requirement of female mosquitoes for a bloodmeal for propagation has been exploited by a wide diversity of viral, protozoan and metazoan pathogens as part of their life cycles. Identifying genes involved in host-seeking, blood feeding and digestion, reproduction, insecticide resistance and susceptibility/refractoriness to pathogen development is expected to provide the bases for the development of novel methods to control mosquito-borne diseases. Advances in mosquito transgenesis technologies, the availability of whole genome sequence information, mass sequencing and analyses of transcriptomes and RNAi techniques will assist development of these tools as well as deepen the understanding of the underlying genetic components for biological phenomena characteristic of these insect species.

Genetics of Major Insect Vectors

3.3 Evolution of the Triatominae

Triatominae is a subfamily of Reduviidae (assassin bugs), which are mostly predators of other arthropods, while triatomines have evolved hematophagy of nest-dwelling vertebrates. It is unclear whether this hematophagy arose once ( monophyletic origin) 26–28 ( Fig. 15.7 ), or several times (paraphyletic/polyphyletic origin) 29,30 within the subfamily. Studies including species from the Alberproseniini, Bolboderini, and Cavernicolini tribes are needed to fill gaps in the comprehensive picture of the evolution of the Triatominae.

Figure 15.7 . Bayesian phylogeny of the Triatominae. 28 Triatoma sp. 1 is an undescribed taxon, morphologically similar to T. gasayana, with short wings, found by F. Noireau in the Bolivian Chaco. Triatoma sp. 2 is an undescribed taxon collected from mammal dwelling in Sucumbios, Ecuador. 30

3.3.1 The Five Triatominae Tribes

Triatominae are classified into 5 tribes and 15 genera and include 147 described species 31 ( Table 15.3 ); most (∼125) occur exclusively in the New World. However, members of the rubrofasciata complex are worldwide, likely spread on ships, and a few others are found only in Asia. The species most important for human transmission are: Triatoma brasiliensis and Triatoma infestans in South America, Triatoma dimidiata and Rhodnius prolixus in Central America and northern South America ( Fig. 15.6 ), which belong to the tribes Triatomini and Rhodniini.

Table 15.3 . Updated List of Triatominae Described Species and Group Assignment Based 166

Tribes Genera Group Complex Subcomplex Species Number of Species
Alberproseniini Alberprosenia goyovargasi, malheiroi 2
Bolboderini Belminus corredori, costaricencis, ferroae, herreri, laportei, peruvianus, pittieri, rugulosus 8
Bolbodera scaborsa 1
Microtriatoma borbai, trinidadensis 2
Parabelminus carioca, yurupucu 2
Cavernicolini Cavernicola lenti, pilosa 2
Rhodniini Pasmmolestes arthuri, coreodes, tertius 3
Rhodnius prolixus barretti, dalessandroi, domesticus, milesi, montenegrensis, nasutus, neglectus, neivai, prolixus, robustus 10
pictipes amazonicus, brethesi, paraensis, pictipes, stali, zeledoni 6
pallescens colombiensis, ecuadoriensis, pallescens 3
Triatomini Dipetalogaster maxima 1
Eratyrus cuspidatus, mucronatus 2
Hermanlentia matsunoi 1
Linshcosteus carnifez, chota, confumus, costalis, kali, karupus 6
Panstrongylus chinai, diasi, geniculatus, guentheri, howardi, humeralis, lenti, lignarius, lutzi, megistus, mitarakaensis, rufotuberculatus, sherlocki, tupynambai 14
Paratriatoma hirsuta 1
Triatoma rubrofasciata phyllosoma (Meccus) dimidiata dimidiata, hegneri, brailovskyi, gomeznunezi 4
phyllosoma bassolsae, bolivari, longipennis, mazzottii, mexicana, pallidipennis, phyllosoma, picturata, ryckmani, 9
flavida (Nesotriatoma) flavida, bruneri, obscura 3
rubrofasciata amicitiae, bouvieri, cavernicola, leopoldi, migrans, pugasi, rubrofasciata, sinica 8
protracta barberi, incrassata, neotomae, nitida, peninsularis, protracta, sinaloensis 7
lecticularia gerstaeckeri, indictiva, lecticularia, recurva, rubida, sanguisuga 6
dispar dispar bolviana, carrioni, dispar, nigromaculata, venosa 5
infestans infestans brasiliensis brasiliensis, juazeirensis, melanica, melanocephala, petrochiae, lenti, sherlocki (tibiamaculata?) (vitticeps?) 9
infestans delpontei, infestans, platensis 3
maculata arthurneivai, maculata, pseudomaculata, wygodzinskyi 4
matogrossensis baratai, costalimai, deaneorum, guazu, jatai, jurbergi, matogrossensis, vandae, williami 9
rubrovaria carcavalloi, circummaculata, klugi, limai, oliveirai, pintodiasi, rubrovaria 7
sordida garciabesi, guasayana, patagonica, sordida 4
spinolai (Mepraia) breyeri, eratyrusiformis, gajardoi, parapatrica, spinolai 5

The Triatomini tribe is the most diverse, with over 100 described species including Triatoma and Panstrongylus, the most diverse and epidemiologically important ( Table 15.3 ). Few morphological differences separate the Triatomini genera 32 and some rank assignments are still unresolved 31,33 ; no cladistic analysis is available to date. T. dimidiata is the most important vector in southern Mexico, Central America, and a secondary vector in northern South America ( Fig. 15.6 ). Triatoma infestans and T. brasiliensis are important vectors across South America and in Brazil, respectively ( Fig. 15.6 ).

Two genera comprise the Rhodniini tribe: Rhodnius and Psammolestes ( Table 15.3 ). Known molecular phylogenies include Psammolestes within the Rhodnius clade 34 despite its morphological adaptations associated with living in bird nests. Rhodnius is morphologically quite different from the other Triatominae, especially in the head morphology; many species are difficult to distinguish. 35 Rhodnius prolixus is currently the main Chagas vector in Colombia and Venezuela and appears to have been introduced (and now eliminated from) Central America. 36

Evolution, Systematics, and Biogeography of the Triatominae, Vectors of Chagas Disease

Fernando Araujo Monteiro, . Fernando Abad-Franch, in Advances in Parasitology , 2018

2.2 Putative Synapomorphies of the Triatominae

The list of putative synapomorphies for the Triatominae is surprisingly short, given the decades-long interest in studying the morphology of the group. Lent and Wygodzinsky (1979) proposed the dorsal flexibility of the labium, haematophagy, and the loss of dorsal abdominal glands as synapomorphies. Clayton (1990) specified that the dorsal flexibility of the labium may be due to an enlarged membrane between the second and third visible labial segments. Weirauch (2008) , based on microdissections of the labium and analyses of muscle origins and insertions, found that this flexibility is likely due to the more dorsal insertion of the head muscle 7 apodeme compared to predatory Reduviidae. Based on her cladistic analysis, Weirauch (2008) also found several additional putative synapomorphies, including a transversely subdivided labrum, the very small mandibular plate, lateral insertion of the antenna, straight labium, the unique structure and armature of the apex of the mandibles and maxillae, the fine structure and orientation of the tenant hairs that form the fossula spongiosa, and dermal glands with uniquely ornamented pores. Future examination of these characters in Alberproseniini, Bolboderini, and Cavernicolini, which were not included in that analysis, will provide a more rigorous assessment of this putative list of synapomorphies.

Volume 2


Arthropods that feed on vertebrate blood are particularly important because of their opportunity to infect their hosts with pathogens that can cause serious illness. As vectors of these pathogens, arthropods such as mosquitoes and ticks must first identify a host, feed on its blood, and use that rich resource to their own advantage. Finding this resource in a complex environment is a considerable challenge for an animal with a relatively unsophisticated nervous system, and the identification and location of these hosts is dependent upon stereotyped behavior patterns that are genetically programmed into the central nervous system and elicited when key stimuli are integrated and associated.

Ectoparasites undoubtedly evolved from free-living ancestors. A parasitic way of life can be evolutionarily approached by several routes, with just a few basic requirements for channeling an organism in this direction. First, two or more organisms must coexist and have ecological opportunities for contact. Second, the smaller of the two must have preadaptations for feeding on the larger, and third, the resulting association must benefit the parasite by increasing its reproductive potential. Protein is often rare in nature, and animals capable of utilizing this rich resource in the blood of vertebrate hosts would reap huge reproductive rewards. Examples are autogenous mosquito species that are able to mature their first batch of eggs by carrying over metabolic reserves that were acquired during the larval stage. However, a larger number of eggs can be produced if the female takes a blood meal and additionally utilizes the external protein source.

The fossil record is rather poor for arthropods in general because their body walls did not resist the pressure of their surroundings, and those that were parasitic and attached to their hosts were easily damaged during the process of carcass decomposition. Despite this limited record, it is thought that beginning about 145 Ma, arthropod hematophagy evolved independently at least six times following two major routes. Lice and fleas probably took the first route. In this scenario, the arthropod initially developed a prolonged intimate association with the host, perhaps by residing in animal burrows that maintained heat and humidity and a source of organic matter. While host feces might have been the first major source of nutrients, skin and hair may also have been encountered, ultimately selecting for arthropods that could utilize these resources more efficiently with their more primitive chewing mouthparts. Behavioral adaptations allowing the arthropod to visit the host directly were eventually followed by the morphological adaptations in mouthpart and digestive system structure and function that were suited to blood ingestion and utilization.

Along the second route toward hematophagy, followed by mosquitoes, bedbugs, and ticks, the arthropod presumably first had the preexisting morphological adaptations that allowed it to pierce the integument of other arthropods or feed on plants and then tend more toward synanthropy. Attracted to other insects aggregating around a vertebrate host or various host products, such contact could eventually lead to hematophagy on the vertebrate host itself. Some unusual insects that follow this path are noctuid moths (genus Calyptra) that have diverged from their plant-feeding relatives to feed on the blood of large vertebrates, feeding not only on eye exudates, but also penetrating skin.

There are also two strategies for removing the blood from a host while feeding. In one, the blood is removed surgically through slender stylets that inject pharmacologically active components in the saliva before feeding. This approach is found in the mosquitoes, blood-sucking bugs, and lice. In the other approach, scissors-like mouthparts lacerate the skin and cause the blood to flow to the surface where it then can be ingested. This mode of feeding is characteristic of ticks, horse flies, black flies, and stable flies.

Most insect ectoparasites that are hematophagous and feed on blood are not parasites in the strict sense, but rather micropredators that prey on host blood and are otherwise free-living. Unless they are present in truly large numbers and reduce the host’s fitness by the removal of enough blood to cause anemia, insect ectoparasites generally do not have a measurable impact on vertebrate host fitness unless they are also vectors of pathogens. The true parasites, such as the lice that live their entire life cycles on a vertebrate host, and a few ticks that complete most of their life cycles on the same hosts, have no need for the more sophisticated host-finding behaviors that are the most essential and challenging behaviors for ectoparasites. Because many hosts also display defensive and grooming behaviors in response to the feeding attempts by their ectoparasites, the parasites have been forced to evolve additional behaviors to contend with these defensive activities.

Flies (Diptera)


The order Diptera is divided by most authorities into two suborders, the Nematocera and the Brachycera ( Table 11.3 ). However, modern systematic studies, including genetic, molecular, morphological, and paleontological datasets for all life stages, indicate that “Nematocera” is a paraphyletic group of superficially similar lineages (Ooseterbrock and Courtney, 1995; Freiderich and Tautz, 1997; Amorim and Yeates, 2006). In fact, studies suggest that hematophagy arose 12 separate times within Diptera, larval endoparasitism 17 times; ectoparasitism 10 times, and loss of functional wings 18 times (Wiegmann et al., 2011). The most current, taxonomically broad, and taxonomically inclusive study of dipteran phylogeny indicates that two rare families, the Deuterophlebiidae and Nymphomyiidae, are the earliest extant fly lineages. The rest of the lower Diptera are composed of four infraorders: Tipulomorpha (crane flies), Culicomorpha (mosquitoes and related groups), Psychodomorpha (sand flies and allies), and Bibionomorpha (March flies and gall midges). The Brachycera are the sister group of the Bibionomorpha and include horseflies, deerflies, houseflies, and other flies with short antennae. The Brachycera are subdivided into Tabanomorpha, including the horseflies and deerflies; Stratiomyomorpha, including the soldier flies; Asiloidea (robber flies, bee flies, and relatives) and Empidoidea (dance flies, dagger flies, and relatives); and Cyclorrhapha. The Cyclorrhapha, in turn, is divided into the Platypezoidea (flat-footed flies, scuttle flies, and allies) and the Schizophora. The latter is divided into a number of acalyptrate superfamilies and Calyptratae. Calyptratae includes the medically important brachyceran families, including the superfamilies Oestridae (bot flies and blowflies), Muscoidea (houseflies, garbage flies, and allies), and Hippoboscoidea (tsetse, bat flies, and louse flies). This taxonomic scheme conflicts to some extent with that proposed by McAlpine et al. (1981) and followed by Borror et al. (1989). Studies on the phylogeny and systematics of Order Diptera are ongoing, and the taxonomy of the order is subject to change as new information comes to light. Table 11.3 reflects the most recent thinking but is by no means final. A catalog of the Diptera of America north of Mexico is provided by Stone et al. (1965).

Table 11.3 . Taxonomic Classification and Families of Diptera of Interest to Medical and Veterinary Entomologists

Higher Taxa Family Common Names
Suborder Nematocera
Infraorder Tipulomorpha Tipulidae Crane flies
Infraorder Bibionomorpha Bibionidae March flies
Mycetophilidae Fungus gnats
Sciaridae Dark-winged fungus gnats
Infraorder Psychodomorpha Psychodidae a Moth flies, sand flies
Infraorder Culicomorpha Chaoboridae Phantom midges
Corethrellidae Frog-biting midges
Culicidae a Mosquitoes
Simuliidae a Blackflies
Ceratopogonidae a Biting midges
Chironomidae Chironomid midges
Suborder Brachycera
Infraorder Tabanomorpha Tabanidae a Horseflies, deerflies
Rhagionidae Snipe flies
Athericidae Athericid flies
Stratiomyidae Soldier flies
Infraorder Xylophagomorpha None None
Infraorder Stratiomyomorpha Stratiomyidae Soldier flies
Cyclorrhapha Syrphidae Flower flies, hover flies
Platypezoidea Phoridae Humpbacked flies
Schizophora Chloropidae Chloropid flies, eye gnats
Tephritoidea Piophilidae Skipper flies
Ephydroidea Drosophilidae Small fruit flies, vinegar flies
Calyptratae Muscidae a Houseflies, stable flies, and allies
Glossinidae a Tsetse
Hippoboscidae a Louse flies
Nycteribiidae a Spider-like bat flies
Streblidae a Bat flies
Oestroidea Oestridae a (including Cuterebrinae, Gasterophilinae, and Hypodermatinae) Botflies, warble flies
Calliphoridae a Blowflies
Sarcophagidae a Flesh flies

Various keys are available for identifying adult flies. Keys to the families and genera of most Nearctic Diptera are presented in McAlpine (1981b). The flies of western North America are treated by Cole (1969). The key in Borror et al. (1989) is adequate for identifying most North American Diptera to the family level. The larvae of many Diptera can be identified to family with the aid of Teskey (1981b) and Foote (1991); those of synanthropic species are treated by Dusek (1971). Furman and Catts (1982) present a usable key to both adults and larvae of medically important flies, particularly in the United States, and James (1947) covers flies that cause myiasis in humans. For identifying taxa outside the Nearctic Region, students should refer to Lindner’s (1949) series on Palearctic Diptera, and to Zumpt (1965) for Old World myiasis-causing flies.


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