Peptide toxins that target vertebrate voltage-gated sodium channels underly the painful stings of harvester ants

Harvester ants (genus Pogonomyrmex) are renowned for their stings which cause intense, long-lasting pain, and other neurotoxic symptoms in vertebrates. Here, we show that harvester ant venoms are relatively simple and composed largely of peptide toxins. One class of peptides is primarily responsible for the long-lasting local pain of envenomation via activation of peripheral sensory neurons. These hydrophobic, cysteine-free peptides potently modulate mammalian voltage-gated sodium (NaV) channels, reducing the voltage threshold for activation and inhibiting channel inactivation. These toxins appear to have evolved specifically to deter vertebrates.

Ant venoms contain vertebrate-selective pain-causing sodium channel toxins

Stings of certain ant species (Hymenoptera: Formicidae) can cause intense, long-lasting nociception. Here we show that the major contributors to these symptoms are venom peptides that modulate the activity of voltage-gated sodium (Na_V) channels, reducing their voltage threshold for activation and inhibiting channel inactivation. These peptide toxins are likely vertebrate-selective, consistent with a primarily defensive function. They emerged early in the Formicidae lineage and may have been a pivotal factor in the expansion of ants.

Functional and Proteomic Insights into Aculeata Venoms

Aculeate hymenopterans use their venom for a variety of different purposes. The venom of solitary aculeates paralyze and preserve prey without killing it, whereas social aculeates utilize their venom in defence of their colony. These distinct applications of venom suggest that its components and their functions are also likely to differ. This study investigates a range of solitary and social species across Aculeata. We combined electrophoretic, mass spectrometric, and transcriptomic techniques to characterize the compositions of venoms from an incredibly diverse taxon. In addition, in vitro assays shed light on their biological activities. Although there were many common components identified in the venoms of species with different social behavior, there were also significant variations in the presence and activity of enzymes such as phospholipase A2s and serine proteases and the cytotoxicity of the venoms. Social aculeate venom showed higher presence of peptides that cause damage and pain in victims. The venom-gland transcriptome from the European honeybee (Apis mellifera) contained highly conserved toxins which match those identified by previous investigations. In contrast, venoms from less-studied taxa returned limited results from our proteomic databases, suggesting that they contain unique toxins.

Seasonal Flight Pattern of the Kissing Bugs Triatoma rubida and T. protracta (Hemiptera: Reduviidae: Triatominae) in Southern Arizona, United States

The two most common kissing bugs, Triatoma rubida and T. protracta, in the Sonoran Desert around Tucson, Arizona are hematophagous vectors of Chagas disease and can induce potentially life-threatening allergic reactions. They were surveyed during their summer dispersal flight period to determine which environmental factors are correlated with flight activity. The two most important factors governing flights of T.rubida were temperatures in the range of 26–35 °C and wind speeds below 14 km/h (9 miles/h). Flights were reduced below or above those temperatures, or when wind speeds exceeding 14km/h. Relative humidity and presence or absence of moonshine appeared unimportant. During their dispersal flight periods of May through July and, especially, between the peak of the flight season, 20 June to 5 July, biologists seeking to collect bugs and homeowners wishing to exclude these biting bugs from entering their homes should be most attentive during evenings of average temperature and low wind speed.

Scorpion Stings and Antivenom Use in Arizona

BACKGROUND

Arizona's rugged desert landscape harbors many venomous animals, including a small nocturnal scorpion, Centruroides sculpturatus, whose venom can cause severe neuromotor disturbance. An effective antivenom is available at selected health care facilities in the state.

METHODS

We analyzed 4398 calls of scorpion stings to the Arizona Poison and Drug Information Center (APDIC) in Tucson over a period of 3 years, from January 2017 to December 2019.

RESULTS

We followed 1952 (44.4%) of the victims to resolution. We excluded 2253 callers with minimal effects of the sting and 193 victims with possible toxic effects who were lost to follow-up. The most common complaints among callers were pain at the sting site in 88.9% and local numbness in 62.2%. Detailed clinical information was obtained from 593 calls from a health care facility. Neuromotor signs consistent with C. sculpuratus envenomation included nystagmus in 163 (27.5%), hypersalivation in 91 (15.3%), and fasciculations in 88 (14.8%). Antivenom (Anascorp; Rare Disease Therapeutics, Inc., Franklin, Tenn) was administered to 145 patients. Most were children <5 years old (n = 76, or 54.4%); 27 (18.6%) were 5-9 years old and 42 (30.0%) were ≥10 years of age. About half, 79 of 145 (54.5%) victims who received antivenom, met the APDIC recommended use criteria.

CONCLUSIONS

Patients treated with antivenom exhibited a rapid resolution of symptoms without immediate or delayed hypersensitivity reactions. We recommend broadened availability of antivenom at sites where it is most needed.

Venom chemistry underlying the painful stings of velvet ants (Hymenoptera: Mutillidae)

Velvet ants (Hymenoptera: Mutillidae) are a family of solitary parasitoid wasps that are renowned for their painful stings. We explored the chemistry underlying the stings of mutillid wasps of the genus Dasymutilla Ashmead. Detailed analyses of the venom composition of five species revealed that they are composed primarily of peptides. We found that two kinds of mutillid venom peptide appear to be primarily responsible for the painful effects of envenomation. These same peptides also have defensive utility against invertebrates, since they were able to incapacitate and kill honeybees. Both act directly on cell membranes where they directly increase ion conductivity. The defensive venom peptides of Dasymutilla bear a striking similarity, in structure and mode of action, to those of the ant Myrmecia gulosa (Fabricius), suggesting either retention of ancestral toxins, or convergence driven by similar life histories and defensive selection pressures. Finally, we propose that other highly expressed Dasymutilla venom peptides may play a role in parasitisation, possible in delay or arrest of host development. This study represents the first detailed account of the composition and function of the venoms of the Mutillidae.

Autochthonous Chagas Disease: How Are These Infections Happening?

Proven cases of vector-transmitted acute autochthonous Chagas disease in the United States are rare (<10 cases). Possible or probable cases of unknown duration determined by serology are uncommon as well (<100). In Latin America it is widely accepted that after feeding, the kissing bug defecates and Trypanosoma cruzi in the feces is rubbed into the bite punctum. This is an inefficient method of parasite transmission. The average infected individual in Latin America suffers more than 1000 bites, but more importantly, there are often thousands of kissing bugs in a household dropping feces on the inhabitants and living quarters. Today in Brazil the most common form of acute Chagas is secondary to oral ingestion of the parasite in food and drink. We present our experience with many hundreds of individuals bitten by kissing bugs and the possibility of oral ingestion occurring in the United States.

Ontogeny, species identity, and environment dominate microbiome dynamics in wild populations of kissing bugs (Triatominae)

BACKGROUND

Kissing bugs (Triatominae) are blood-feeding insects best known as the vectors of Trypanosoma cruzi, the causative agent of Chagas' disease. Considering the high epidemiological relevance of these vectors, their biology and bacterial symbiosis remains surprisingly understudied. While previous investigations revealed generally low individual complexity but high among-individual variability of the triatomine microbiomes, any consistent microbiome determinants have not yet been identified across multiple Triatominae species.

METHODS

To obtain a more comprehensive view of triatomine microbiomes, we investigated the host-microbiome relationship of five Triatoma species sampled from white-throated woodrat (Neotoma albigula) nests in multiple locations across the USA. We applied optimised 16S rRNA gene metabarcoding with a novel 18S rRNA gene blocking primer to a set of 170 T. cruzi-negative individuals across all six instars.

RESULTS

Triatomine gut microbiome composition is strongly influenced by three principal factors: ontogeny, species identity, and the environment. The microbiomes are characterised by significant loss in bacterial diversity throughout ontogenetic development. First instars possess the highest bacterial diversity while adult microbiomes are routinely dominated by a single taxon. Primarily, the bacterial genus Dietzia dominates late-stage nymphs and adults of T. rubida, T. protracta, and T. lecticularia but is not present in the phylogenetically more distant T. gerstaeckeri and T. sanguisuga. Species-specific microbiome composition, particularly pronounced in early instars, is further modulated by locality-specific effects. In addition, pathogenic bacteria of the genus Bartonella, acquired from the vertebrate hosts, are an abundant component of Triatoma microbiomes.

CONCLUSION

Our study is the first to demonstrate deterministic patterns in microbiome composition among all life stages and multiple Triatoma species. We hypothesise that triatomine microbiome assemblages are produced by species- and life stage-dependent uptake of environmental bacteria and multiple indirect transmission strategies that promote bacterial transfer between individuals. Altogether, our study highlights the complexity of Triatominae symbiosis with bacteria and warrant further investigation to understand microbiome function in these important vectors. Video abstract.

Kissing Bugs Harboring Trypanosoma cruzi, Frequently Bite Residents of the US Southwest But Do Not Cause Chagas Disease

BACKGROUND

Kissing bugs are common household pests in the Desert Southwest of the United States. These hematophagous bugs enter homes and suck blood from resident humans and pets. They are vectors of Trypanosoma cruzi, an enzootic parasite in small mammals and the cause of Chagas disease in humans. Autochthonous cases of Chagas disease are rare in the United States despite the presence of the vector and parasite. Environmental and biological factors accounting for this phenomenon need studying.

METHODS

Homeowners in Bisbee and Tucson, Arizona captured kissing bugs inside homes during 2017-2018. Bugs were tested for presence of T. cruzi by polymerase chain reaction. Residents bitten by kissing bugs were tested for Chagas disease by serology. We evaluated invaded homes in the 2 cities.

RESULTS

Three species of kissing bugs (n = 521) were collected in or near homes. Triatoma rubida was the most common triatomine in Tucson; T. recurva in Bisbee. T. protracta was uncommon. Seventeen percent of bugs captured in Bisbee and 51.1% in Tucson harbored T. cruzi. Bite victims (n = 105) recalled more than 2200 bites. Reactions to bites were common, including 32 episodes of anaphylaxis in 11 people (10.5%). Tests for Chagas disease (n = 116) were negative. Median age of houses was 91 years in Bisbee and 7 years in Tucson. Bisbee houses had pier and beam foundations. Tucson houses were built on concrete slabs.

CONCLUSIONS

Kissing bugs harboring T. cruzi readily entered new and old homes. Bites of humans caused severe, life-threatening reactions. There was no serological evidence of Chagas disease among those bitten.

Unconscious Woman in Shock and Covered with Ants Pulled from an Abandoned Automobile

BACKGROUND

A middle-aged woman was taken from an abandoned automobile unconscious and covered with ants in Tucson, Arizona. When hospitalized in July 2018, she had an extensive papular-pustular skin eruption on her abdomen and thigh and disseminated intravascular coagulation. She was stung innumerable times by native golden fire ants (Solenopsis aurea) while sleeping in the vehicle. The large amount of venom injected by stings into this individual may have triggered dissemnated intravascualar coagulation because the venom contains powerful hemolytic factors.

METHODS

The patient history is presented and ants were captured and identified.

RESULTS

Clinical findings of fire ant stings are presented and the importance of recognizing the distinctive skin lesions that occur is emphasized. Stings of the red imported fire ant, Solenopsis invicta, and the black imported fire ant, Solenopsis richteri, cause skin lesions recognized by physicians and victims alike in the southern and southeastern United States. Native fire ant stings are documented much less often. However, there is significant cross-reactivity among the venoms of Solenopsis species.

CONCLUSION

It is important for clinicians to recognize the characteristic skin lesions of fire ant envenomation as fire ant populations are expanding and they sting millions of people each year.

Pain and Lethality Induced by Insect Stings: An Exploratory and Correlational Study

Pain is a natural bioassay for detecting and quantifying biological activities of venoms. The painfulness of stings delivered by ants, wasps, and bees can be easily measured in the field or lab using the stinging insect pain scale that rates the pain intensity from 1 to 4, with 1 being minor pain, and 4 being extreme, debilitating, excruciating pain. The painfulness of stings of 96 species of stinging insects and the lethalities of the venoms of 90 species was determined and utilized for pinpointing future directions for investigating venoms having pharmaceutically active principles that could benefit humanity. The findings suggest several under- or unexplored insect venoms worthy of future investigations, including: those that have exceedingly painful venoms, yet with extremely low lethality—tarantula hawk wasps (Pepsis) and velvet ants (Mutillidae); those that have extremely lethal venoms, yet induce very little pain—the ants, Daceton and Tetraponera; and those that have venomous stings and are both painful and lethal—the ants Pogonomyrmex, Paraponera, Myrmecia, Neoponera, and the social wasps Synoeca, Agelaia, and Brachygastra. Taken together, and separately, sting pain and venom lethality point to promising directions for mining of pharmaceutically active components derived from insect venoms.

Rapid detection of human blood in triatomines (kissing bugs) utilizing a lateral flow immunochromatographic assay - A pilot study

OBJECTIVES

We tested a rapid and specific immunochromatographic assay (that detects human blood in forensic samples) to determine if human blood was present in triatomines and their fecal excreta.

METHODS

We fed Triatoma rubida human blood (positive control) or mouse blood (negative control) and performed the assay on the abdominal contents and fecal excreta. Triatomine field specimens collected in and around human habitations and excreta were also tested.

FINDINGS

The assay was positive in triatomines fed human blood (N = 5/5) and fecal excreta from bugs known to have ingested human blood (N = 5/5). Bugs feeding on mice (N = 15/15) and their fecal excreta (N = 8/8) were negative for human blood. Human blood was detected in 47% (N = 23/49) triatomines, representing six different species, collected in the field.

MAIN CONCLUSIONS

The pilot study shows that this rapid and specific test may have applications in triatomine research. Further study is needed to determine the sensitivity of this assay compared to other well-established techniques, such as DNA- and proteomics-based methodologies and the assay’s application in the field.

Second-Best Is Better Than Nothing: Cockroaches as a Viable Food Source for the Kissing Bug Triatoma recurva (Hemiptera: Reduviidae)

Kissing bugs in the genus Triatoma are obligate blood feeders that feed mainly on vertebrate blood and have lost the predatory lifestyle found in other reduviid bugs. They occasionally also feed on the hemolymph of arthropods, especially during the first and second instar stages. The largest kissing bug species in the United States, Triatoma recurva (Stål) (Hemiptera: Reduviidae), is poorly known and was chosen to investigate its ability to feed and develop on a diet of cockroach hemolymph. Molting from first instar individuals to second instars readily occurred at approximately the same rate reported for the species feeding on mammalian blood. Subsequent instars also fed on and survived on cockroach hemolymph with some individuals maturing to adults. In the larger instars, development time and survival rates were reduced relative to the results reported in the literature for mammalian-blood-fed individuals. Two other species of kissing bugs, Triatoma protracta (Uhler) and T. rubida (Uhler) failed to survive on cockroach hemolymph with most individuals failing to molt from the first instar stage. Although T. recurva does not thrive on a diet limited to hemolymph of cockroaches, it appears to be an unusual species in which cockroaches might be a primary source of nutrition for smaller individuals and are a viable exclusive source of nutrition for all immatures. At a minimum during times of limited availability of vertebrate blood sources, the presence of cockroaches enhances survival opportunities. Efforts to control populations of this kissing bug species likely will be improved with additional control of cockroach populations in the environment.

Protein mass spectrometry extends temporal blood meal detection over polymerase chain reaction in mouse-fed Chagas disease vectors

BACKGROUND

Chagas disease is highly prevalent in Latin America, and vector control is the most effective control strategy to date. We have previously shown that liquid chromatography tandem mass spectrometry (LC-MS/MS) is a valuable tool for identifying triatomine vector blood meals.

OBJECTIVES

The purpose of this study was to determine blood meal detection ability as a function of method [polymerase chain reaction (PCR) vs. LC-MS/MS], time since feeding, and the effect of molting in mouse-fed triatomine insect vectors targeting hemoglobin and albumin proteins with LC-MS/MS and short interspersed nuclear elements (SINE)-based PCR.

METHODS

We experimentally fed Triatoma protracta on mice and used LC-MS/MS to detect hemoglobin and albumin peptides over time post-feeding and post-molting (≤ 12 weeks). We compared LC-MS/MS results with those of a standard PCR method based on SINEs.

FINDINGS

Hemoglobin-based LC-MS/MS detected blood meals most robustly at all time points post-feeding. Post-molting, no blood meals were detected with PCR, whereas LC-MS/MS detected mouse hemoglobin and albumin up to 12 weeks.

MAIN CONCLUSIONS

In our study, the hemoglobin signature in the insect abdomen lasted longer than that of albumin and DNA. LC-MS/MS using hemoglobin shows promise for identifying triatomine blood meals over long temporal scales and even post-molting. Clarifying the frequency of blood-feeding on different hosts can foster our understanding of vector behavior and may help devise sounder disease-control strategies, including Ecohealth (community based ecosystem management) approaches.

Microbiomes of North American Triatominae: The Grounds for Chagas Disease Epidemiology

Insect microbiomes influence many fundamental host traits, including functions of practical significance such as their capacity as vectors to transmit parasites and pathogens. The knowledge on the diversity and development of the gut microbiomes in various blood feeding insects is thus crucial not only for theoretical purposes, but also for the development of better disease control strategies. In Triatominae (Heteroptera: Reduviidae), the blood feeding vectors of Chagas disease in South America and parts of North America, the investigation of the microbiomes is in its infancy. The few studies done on microbiomes of South American Triatominae species indicate a relatively low taxonomic diversity and a high host specificity. We designed a comparative survey to serve several purposes: (I) to obtain a better insight into the overall microbiome diversity in different species, (II) to check the long term stability of the interspecific differences, (III) to describe the ontogenetic changes of the microbiome, and (IV) to determine the potential correlation between microbiome composition and presence of Trypanosoma cruzi, the causative agent of Chagas disease. Using 16S amplicons of two abundant species from the southern US, and four laboratory reared colonies, we showed that the microbiome composition is determined by host species, rather than locality or environment. The OTUs (Operational Taxonomic Units) determination confirms a low microbiome diversity, with 12-17 main OTUs detected in wild populations of T. sanguisuga and T. protracta. Among the dominant bacterial taxa are Acinetobacter and Proteiniphilum but also the symbiotic bacterium Arsenophonus triatominarum, previously believed to only live intracellularly. The possibility of ontogenetic microbiome changes was evaluated in all six developmental stages and feces of the laboratory reared model Rhodnius prolixus. We detected considerable changes along the host's ontogeny, including clear trends in the abundance variation of the three dominant bacteria, namely Enterococcus, Acinetobacter, and Arsenophonus. Finally, we screened the samples for the presence of Trypanosoma cruzi. Comparing the parasite presence with the microbiome composition, we assessed the possible significance of the latter in the epidemiology of the disease. Particularly, we found a trend toward more diverse microbiomes in Trypanosoma cruzi positive T. protracta specimens.

A reexamination of poneratoxin from the venom of the bullet ant Paraponera clavata

In 1991, Piek et al. [45] described a voltage-gated sodium channel (VGSC) modifier from "bullet ant" (Paraponera clavata) venom they called poneratoxin (PoTx). Using UV chromatography and Edman degradation they showed two "identical peptides" of 25 residues. We reinvestigated PoTx using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-TMS). De novo sequencing showed the two peptides were actually structurally different peptides: the originally described PoTx and a glycyl pro-peptide (glycyl-PoTx) that lacks C-terminus amidation. We examined P. clavata venom from different geographical locations and discovered two additional PoTx analogs: an A23E substitution analog and a D22N; A23V substitutions analog. We tested PoTx and these three natural analogs on the mammalian sensory voltage-gated sodium channel, Na_v1.7, using whole cell voltage-clamp. PoTx and each analog induced slowly activating currents in response to small depolarizing steps and sustained currents due to blockade of channel inactivation, similar to that described previously in skeletal muscle [19]. Glycyl-PoTx had the same potency and efficacy as PoTx. A23E PoTx, with a decrease in both C-terminal net positive charge and hydrophobicity, had an eight-fold reduction in potency compared to PoTx. In contrast, the D22N; A23V PoTx, with an increase in both C-terminal net positive charge and hydrophobicity, had a nearly five-fold increase in potency compared to PoTx. We found that changes in PoTx C-terminus caused a significant change in PoTx potency.

Kissing Bug (Triatoma spp.) Intrusion into Homes: Troublesome Bites and Domiciliation

Kissing bugs (Triatoma spp.) frequently enter homes and bite human and pet occupants. Bites may lead to severe allergic reactions and, in some cases, death. Kissing bugs are also vectors of Trypanosoma cruzi, the cause of Chagas disease. In general, modern houses in the United States are not conducive to domiciliation of kissing bugs (bugs living out their entire life within the home with the presence of eggs, nymphs, adults, and exuviae). Construction features such as concrete foundations, solid walls and ceilings, window screens, tight thresholds for doors and windows, and other measures impede bug entry into homes, and air conditioning reduces the need for open doors and windows. Where Chagas disease is endemic in Mexico and Central and South America, homes often have thatch roofs, adobe walls, and open doors and windows. We investigated numerous instances of kissing bug intrusions into homes in Southern Arizona, California, and Louisiana and documented the reactions to kissing bug bites. Our work confirms the importance of modern home construction in limiting kissing bug intrusions. Older homes, especially those lacking modern screening, caulking, and weather stripping to reduce air leakage, may be subject to kissing bug intrusions and domiciliation. We describe a community in Southern Arizona where domiciliation of homes by Triatoma recurva is common. We also provide recent data regarding kissing bug bites and allergic reactions to the bites.

Repellency of the Components of the Essential Oil, Citronella, to Triatoma rubida, Triatoma protracta, and Triatoma recurva (Hemiptera: Reduviidae: Triatominae)

The kissing bugs--Triatoma rubida (Uhler), Triatoma protracta (Uhler), and Triatoma recurva (Stal)--are common hematophagous bugs in southeastern Arizona and responsible for severe allergic reactions in some individuals who are bitten. They also possess the potential to transmit the blood parasite, Trypanosoma cruzi. We previously found the essential oil, citronella, to be an excellent deterrent of feeding of T. rubida on a restrained mouse. In this work, we tested major components--alcohols, aldehydes, and monoterpenes--of citronella oil for repellency against the three common triatome species endemic in southern Arizona. The following citronella oil components--geraniol, citronellol, limonene, and citronellal--in different concentrations and combinations were tested. All components of citronella oil demonstrated some inhibition of feeding, ranging from very weak inhibition (limonene) to significant inhibition (geraniol and citronellol). A mixture of geraniol and citronellol was found to be repellant at concentrations of .165 and .165 vol%, respectively, for all three triatome species. Citronellal and limonene had no significant repellent activity. The repellent activity of citronella oil appears to be acting through direct contact with the bugs rather than diffusion of vapors.

Free-roaming kissing bugs, vectors of Chagas disease, feed often on humans in the Southwest

BACKGROUND

Kissing bugs, vectors of Trypanosoma cruzi, the parasite that causes Chagas disease, are common in the desert Southwest. After a dispersal flight in summer, adult kissing bugs occasionally gain access to houses where they remain feeding on humans and pets. How often wild, free-roaming kissing bugs feed on humans outside their homes has not been studied. This is important because contact of kissing bugs with humans is one means of gauging the risk for acquisition of Chagas disease.

METHODS

We captured kissing bugs in a zoological park near Tucson, Arizona, where many potential vertebrate hosts are on display, as well as being visited by more than 300,000 humans annually. Cloacal contents of the bugs were investigated for sources of blood meals and infection with T. cruzi.

RESULTS

Eight of 134 captured bugs were randomly selected and investigated. All 8 (100%) had human blood in their cloacae, and 7 of 8 (88%) had fed on various vertebrates on display or feral in the park. Three bugs (38%) were infected with T. cruzi. Three specimens of the largest species of kissing bug in the United States (Triatoma recurva) were captured in a cave and walking on a road; 2 of 3 (67%) had fed on humans. No T. recurva harbored T. cruzi.

CONCLUSIONS

This study establishes that free-roaming kissing bugs, given the opportunity, frequently feed on humans outside the confines of their homes in the desert Southwest and that some harbored T. cruzi. This could represent a hitherto unrecognized potential for transmission of Chagas disease in the United States.

Kissing bugs in the United States: risk for vector-borne disease in humans

Eleven species of kissing bugs are found in the United States. Their home ranges may be expanding northward, perhaps as a consequence of climate change. At least eight of the species, perhaps all, are reported to harbor Trypanosoma cruzi, the parasite that causes Chagas disease. Because humans are encroaching on kissing bug habitat, there is concern for vector-transmitted Chagas disease in the United States. To date, documented autochthonous cases of Chagas in humans in the United States are rare. Kissing bugs are capable of adapting to new habitats such as human domiciles; however, they do not colonize homes in the United States as in Central and South America. We review the biology, behavior, and medical importance of kissing bugs and the risk they pose for transmission of Chagas disease in the United States. Where possible, descriptions of US species are compared to the epidemiologically important Latin American species.

Volatiles from mandibular glands of male beewolves (Hymenoptera: Sphecidae,Philanthus) and their possible roles

Observations of wasp behavior indicate that male beewolves,Philanthus basilaris andP. bicinctus apply a "marking pheromone" to the leaves and stems of plants within their territories. We now provide direct evidence for the presence of volatile chemicals in the paired mandibular glands of the males, provide preliminary identification of these volatiles, and show that all of the volatile chemicals in the mandibular glands are present on freshly marked plant surfaces but are absent from unmarked plants. Pyrazines, which have been reported in other species of aculeate wasps including the EuropeanPhilanthus triangulum, were not found inP. basilaris orP. bicinctus.

Chemistry of male mandibular gland secretions ofPhilanthus basilaris cresson andPhilanthus bicinctus (Mickel) (Hymenoptera: Sphecidae)

Detailed chemical characterizations are provided for the species-specific mixtures of marking pheromones utilized by the male beewolvesPhilanthus basilaris andP. bicinctus. Successful analysis of these complex mixtures of 2-ketones, fatty acids, ethyl esters, and aldehydes was facilitated by the treatment of the crude extracts with 1,1-dimethylhydrazine and direct analysis of the resulting hydrazones, methyl esters, and starting ethyl esters by GC-MS.

Mandibular gland secretions of the male beewolvesPhilanthus crabroniformis, P. barbatus, andP. pulcher (Hymenoptera: Sphecidae)

The composition of the territorial marking pheromones from mandibular glands of males of the beewolvesPhilanthus crabroniformis, P. barbatus, andP. pulcher have been determined. The structures of the components were elucidated by gas chromatography-mass spectrometry and gas chromatography-Fourier transform infrared spectroscopy. The major compound ofP. crabroniformis is isopropyl tetradecanoate, with somewhat lesser amounts of 2-tridecanone, 3-methyl-3-butenyl tetradecanoate, and 92∶8 (Z)∶(E)-11-eicosen-1-ol. The major compounds ofP. barbatus are ethyl tetradecanoate and hexadecanal, which are present in approximately a 60∶40 ratio. These two compounds comprise over 95% of the neutral lipids. Also present in lesser amounts are ethyl dodecanoate, tetradecanal, hexadecan-1-ol, a Δ (x) -octadecen-1-ol, and octadecan-1-ol. The major compounds ofP. pulcher are ethyl (Z)-7-hexadecenoate and geranylgeraniol acetate, which comprise nearly 90% of the neutral lipid fraction, with smaller amounts of tetradecanal, pentadecanal, and ethyl hexadecanoate; trace amounts of Δ (x) hexadecenal, hexadecanal, and octadecanal are also present.

Attraction of reproductive honey bee swarms to artificial nests by Nasonov pheromone

A crossover experimental design was established to test the attractancy of Nasonov pheromone to reproductive swarms of honey bees. Nineteen swarms were attracted to artificial nest cavities containing a slow-release blend of the Nasonov components citral, geraniol, and nerolic + geranic acids, and only four swarms were attracted to pheromone-free artificial nests. The results indicate that Nasonov pheromone plays a key role in the attraction of honey bee swarms to nest cavities.

Repellency of DEET, picaridin, and three essential oils to Triatoma rubida (Hemiptera: Reduviidae: Triatominae)

The kissing bug, Triatoma rubida (Uhler) is a common hematophagous bug in Tucson, AZ, and is responsible for causing severe allergic reactions in some bitten individuals. DEET, picaridin, tea tree oil, peppermint oil, and citronella oil were tested for repellency to T. rubida and its ability to probe and feed on a small restrained rat. No long range repellency was observed with any of the test materials. The lowest repellent concentrations observed were: 10% DEET, 7% picaridin; 30% tea tree oil, 3.3% peppermint oil, and 0.165% citronella oil. Only citronella oil was able to stop all probing and feeding by T. rubida. Citronella oil appears to be a promising potential repellent to prevent sleeping people from being bitten by kissing bugs.

Vector blood meals and Chagas disease transmission potential, United States

A high proportion of triatomine insects, vectors for Trypanosoma cruzi trypanosomes, collected in Arizona and California and examined using a novel assay had fed on humans. Other triatomine insects were positive for T. cruzi parasite infection, which indicates that the potential exists for vector transmission of Chagas disease in the United States.

Kissing bugs. The vectors of Chagas

A complete picture of Chagas disease requires an appreciation of the many species of kissing bugs and their role in transmitting this disease to humans and other mammals. This chapter provides an overview of the taxonomy of the major species of kissing bugs and their evolution. Knowledge of systematics and biological kinship of these insects may contribute to novel and useful measures to control the bugs. The biology of kissing bugs, their life cycle, method of feeding and other behaviours contributing to the transmission of Trypanosoma cruzi are explained. We close with a discussion of vector control measures and the allergic complications of kissing bug bites, a feature of particular importance in the United States.

Adverse reactions to ants other than imported fire ants

OBJECTIVE

To identify ants other than Solenopsis invicta and Solenopsis richteri reported to cause adverse reactions in humans.

DATA SOURCES

We conducted a literature review to identify reports of medical reactions to ants other than S. invicta and S. richteri. Our review of medical and entomological literature on stinging ants was generated from MEDLINE and FORMIS, respectively, using the key words stinging ants and ant stings. The search was limited to articles in English published from 1966 to 2004 on MEDLINE and all years on FORMIS. We also present 3 new case reports of severe reactions to stings by 2 different species of ants, Pseudomyrmex ejectus and Hypoponera punctatissima.

STUDY SELECTION

Articles that concerned anaphylactic (IgE-mediated) or anaphylactic-like (resembling anaphylaxis but mechanism unknown) immediate reactions to ant stings or bites were included in this review.

RESULTS

Taken together, our data demonstrate that S. invicta and S. richteri are not alone in their capability to cause serious allergic or adverse reactions. A diverse array of ant species belonging to 6 different subfamilies (Formicinae, Myrmeciinae, Ponerinae, Ectatomminae, Myrmicinae, and Pseudomyrmecinae) and 10 genera (Solenopsis, Formica, Myrmecia, Tetramorium, Pogonomyrmex, Pachycondyla, Odontomachus, Rhytidoponera, Pseudomyrmex, and Hypoponera) have now been shown to have this capability.

CONCLUSION

Awareness that species other than imported fire ants may cause severe reactions should lead to more rapid evaluation and treatment and further investigation of the medical entomology of these ants.

Modulation of nicotinic acetylcholine and N-methyl-d-aspartate receptors by some Hymenopteran venoms

The effect of 19 venoms from solitary wasps, solitary bees, social wasps and ants were investigated for their effects on nicotinic acetylcholine receptors (nAChR) and ionotropic glutamate receptors (IGRs) of both the N-methyl-d-aspartate (NMDAR) and non-NMDAR type. Whole-cell patch clamp of human muscle TE671 cells was used to study nAChR, and of rat cortical and cerebellar granule cells for IGRs. Solitary wasp venoms caused significant voltage-dependent antagonism of nAChR responses to 10 microM ACh and NMDAR responses to 100 microM NMDA (+10 microM glycine) when co-applied at 1 microg/ml with the agonists. At positive holding potentials (V(H)) potentiation of these receptors was observed with some venoms. Solitary bee venoms only affected nAChR by causing either voltage-independent antagonism or potentiation of their responses to 10 microM ACh. Of four social wasp venoms, one acted on nAChR by potentiating responses to 10 ACh, while another generated an ACh-like response when applied alone. They had no effect on IGRs. Of the two ant venoms, one caused voltage-independent inhibition of nAChR. Neither affected IGRs. The data indicate the presence of nAChR agonists and antagonists and NMDAR antagonists in Hymenopteran venoms and warrant further investigation to separate and identify these venom components.

Olfactory stimulation of Africanized honey bee (Hymenoptera: Apidae) attacks by insect repellents

Three common insect repellents (N,N-diethyl-m-toluamide [DEET], Pyranha, and Repel X) were tested to determine whether they affected Africanized honey bee attack behavior. Eight Africanized honey bee (Apis mellifera L.) colonies were exposed in an alternating series to the test repellents or blank controls delivered in a stream of air directed toward the colony entrances. The response generated by the repellents and the controls was measured as the number of attacking honey bees recorded with an electronic temper tester. Neither a citronella-based repellent (Pyranha) nor DEET had any effect on colony behavior; however, Repel X consistently caused a greater attack response after exposure.

Head kidney neutrophils of carp (Cyprinus carpio L.) are functionally modulated by the haemoflagellateTrypanoplasma borreli

In the present work responses of carp (Cyprinus carpio) head kidney-derived neutrophils to the blood parasite T. borreli, and the consequences of these responses for parasite survival and other host response mechanisms, were studied. In co-cultures of head kidney leucocytes (HKL) with viable and lysed T. borreli a prominent shape change of neutrophilic granulocytes towards increased size and complexity was observed. In addition, the longevity of neutrophils in vitro was prolonged in the presence of T. borreli antigens. In these cultures, neutrophils also exhibited an increased phagocytosis activity. An up regulation of the production of nitric oxide (NO) and reactive oxygen species (ROS) was observed in T. borreli- and mitogen-stimulated HKL cultures. However, addition of live, fluorescence-labelledT. borreli to previously stimulated HKL cultures, revealed neither killing nor phagocytosis of the parasite by activated neutrophils. Moreover, viable T. borreli, when added to HKL cultures of infected carp, reduced their phagocytosis activity and NO production. Supernatants of co-cultures between T. borreli and HKL also contained mediators, which suppressed a mitogen-induced proliferative response of peripheral blood leucocytes (PBL) in vitro. Thus, while T. borreli itself appeared not to be sensitive to responses of activated neutrophils, the flagellates interferes with the production of immunomodulatory signals of these cells, probably resulting in a partial immunosuppression, which may favour the parasite development in vivo.

The effect of octopamine on behavioral responses of free-foraging bumblebees to a change in food source profitability

The invertebrate neuromodulator octopamine is known to be involved in bees' associative learning, enhancing the responsiveness of a bee to a conditioned stimulus. In this study, we tested the effect of octopamine on the choice behavior of free-flying bumblebees using a two-phase experiment in an array of artificial flowers. During the first phase of the experiment, the bee was allowed to collect octopamine-laden sugar water from two types of equally rewarding flowers (yellow versus blue). In the second phase, one type of flower was set to be unrewarding. The behavior of the bee (proportion of visits to the unrewarding flowers) over the two phases was fitted to a sigmoid regression model. Our results show that octopamine had no significant effect on the bees' equilibrium choice or on the overall rate of the behavioral change in response to the change in reward. Rather, octopamine significantly affected the time interval between the change in reward status and the initiation of behavioral change in the bee.

The haemoflagellate Trypanoplasma borreli induces the production of nitric oxide, which is associated with modulation of carp (Cyprinus carpio L.) leucocyte functions

In an attempt to characterise the role of nitric oxide (NO) in immune responses of carp, carp leucocytes obtained during an acute T. borreli infection were examined, for their capacity to generate NO. In a second set of experiments the impact NO on viability of the parasite and on the modulation of functional carp leucocyte responses were tested in vitro. Both in carp head-kidneys and in the peripheral blood, the fractions of lymphoblasts among separated leucocytes were increased. However, the relative proportions of granulocytes among head-kidney leucocytes (HKL) significantly decreased during infection, whereas granulocytes appeared among peripheral blood leucocytes (PBL). The cellular dynamics of HKL and PBL of infected carp were paralleled by an enhanced spontaneous NO release in vitro. NO production was further increased after addition of viable parasites to these cultures. The hypothesis that NO had a possible role in granulocyte activation and lymphocyte proliferation in carp was supported by the reduction of mitogen-induced proliferative responses of PBL from healthy carp in the presence of NO donor substances. The negative effects of NO on lymphocyte proliferation were contrasted by enhancing effects on granulocyte functions: the inhibition of NO generation in T. borreli-stimulated HKL cultures by the l-arginine analogue L-NMMA reduced the viability of granulocytes and their phagocytic activity. Even massive amounts of nitric oxide produced by donor substances (up to 600 micromol l(-1) NO(-)(2)) caused no reduction in the numbers of viable T. borreli flagellates in vitro. Thus, in carp, T. borreli seems to induce high amounts of NO in vivo which are apparently not harmful for the parasite but which may interfere with co-ordinated interactions of activated cells aiming at the defence of the parasite.

(Z)-3-hexenyl (R)-3-hydroxybutanoate: a male specific compound in three North American decorator wasps Eucerceris rubripes, E. conata and E. tricolor

The males of the decorator wasps Eucerceris have been observed to display abdomen-dragging behavior on plants surrounding their nest. It is thought that this applies a territorial-marking sex pheromone that serves to alert females to the males' territory for courtship and mating. The extracts of three species E. rubripes, E. conata, and E. tricolor have been analyzed by GC-MS. The gas chromatograms revealed the presence, in large quantities, of one common volatile compound in the male head extracts. By analogy with the closely related bee wolves Philanthus, we believe the pheromone is produced in the mandibular glands. Utilizing mass spectrometry, microreactions, FT-IR, and 1H and 13C NMR spectroscopy the structure of the pheromone was proposed to be (Z)-3-hexenyl 3-hydroxybutanoate, which was confirmed by synthesis. The absolute configuration of the chiral center was determined to be R for the three species by preparing the Mosher esters of the insect samples and comparing their GC retention times with a synthetic sample of known absolute configuration. In addition 2- and 3-hexenoic acid and some aromatic compounds were also found in varying quantities in both males and females along with hydrocarbons and fatty acids, although no species-specific profiles emerged.

Labial gland chemistry of three species of bumblebees (Hymenoptera: Apidae) from North America

The volatile secretion emanating from the cephalic part of the paired labial gland in male bumblebees of three North American species, viz. Bombus sonorus Say, Bombus huntii Greene and Psithyrus insularis (F. Smith) has been analysed by GC-MS and GC-FTIR. The secretion, which is deposited as a marking secretion on various objects along a repetitive flight path, is composed of isoprenoids, (acyclic sesqui- and diterpenes) and straight-chain fatty acid derivatives (alcohols containing 14, 16 and 18 carbon atoms, and odd numbered hydrocarbons ranging from 23 to 27 carbons). The secretions are species-specific with just a few major components. In B. sonorus (Z)-11-octadecen-1-ol is the main compound accompanied by geranylgeraniol and tetradecan-1-ol; in B. huntii the dominating compound is trans-2,3-dihydrofarnesol and it also contains (Z)-11-octadecen-1-ol and hexadecan-1-ol; P. insularis is characterized by geranylcitronellol, together with the (Z)-11-octadecen-1-ol and hexadecan-1-ol. These results agree with analyses of 36 species and two forms of Scandinavian bumblebees analysed previously.

Toxinology of venoms from the honeybee genus Apis

The venoms of Apis dorsata, A. cerana, A. florea, and three different populations of A. mellifera were compared for lethal activity toward mice. All venoms exhibited identical activities, a finding consistent with recent evolutionary history within the genus. Young queen honeybees use their venoms only for stinging other queens and possess a venom only half as lethal to mice as worker venom, and by the time queens are 1-2 years of age their venom has become essentially inactive. Phospholipase A2 is the most lethal of the honeybee venom peptides, whereas melittin, which is only slightly less lethal, is the most abundant. Concurrent analyses of melittin, phospholipase, and the combination of the two at their natural 3:1 mixture in bee venom revealed that the lethal activity of the mixture was about the same as native honeybee venom. This value was less than that for either melittin or phospholipase alone and indicates that synergism of the two peptides is not occurring. The results are consistent with independent lethal activities for the venom components, and show that melittin is not only the dominant, but also the main lethal component in honeybee venom.

Serine proteinase inhibitor profiles in the hemolymph of a wide range of insect species

1. The inhibition of trypsin, chymotrypsin, neutrophil elastase and cathepsin G, and pancreatic elastase by the hemolymph of 14 insect species in six orders has been investigated. 2. All samples showed great diversity in terms of both total proteinase inhibitory capacity and specificity. 3. The highest total inhibitory capacity was found in the larval hemolymph of species in the beetle family Tenebrionidae and the lowest in that of an adult coreid bug, Acanthocephala femorata.

Biochemical variability of venoms from individual European and Africanized honeybees (Apis mellifera)

To study biochemical differences between venom from individual honeybees, venom sacs from 103 European (EU) bees and 92 Africanized bees representing 12 different colonies were dissected, and the dry weight (DW) of venom from each bee was determined. Venom from each of these bees was studied with isoelectric focusing and functional assays for phospholipase A2 and melittin. Phospholipase concentrations in individual EU bee venoms varied between 1.8% and 27.4% (wt/wt). The melittin concentration in EU bee venom varied less and, on the average, was found to be much lower than previously reported. There was an eightfold to ninefold difference between lowest and highest venom sac DW contents, suggesting the possibility of highly variable venom delivery from bee stings. One EU bee contained greater than 300 micrograms of venom, three times the recommended maintenance dose for venom immunotherapy. Isoelectric focusing also demonstrated large differences between individual bees, with respect to major and minor components of their venoms. Africanized bees contained significantly less venom but more phospholipase than did EU bees. Bee venoms from different colonies differed in their DW content and in their concentrations of phospholipase and melittin. The results are relevant to the uncertainty of responses from sting challenges and field stings in allergic patients and massive stinging attacks on normal subjects.