Stinging caterpillars from the genera Podalia, Leucanella and Lonomia in Misiones, Argentina: A preliminary comparative approach to understand their toxicity

Geographical and temporal distribution of Megalopygidae in the United States and Puerto Rico

Background

The venom of Megalopygidae caterpillars causes inflammation and pain. Understanding geographic and temporal variation in exposure will help physicians and the public understand when and where the species in this family may be encountered.

Methods

Photographs uploaded by community scientists to the iNaturalist database were reviewed and identified. GIS data points were used to model distribution of species based on geographic variables at the location of photographs for each group. Data on temporal abundance was also noted.

Results

Maps were created predicting the geographic range for 11 species of Megalopygidae. Peak larval abundance for the most abundant species, Megalopyge opercularis, was determined as September in the southeastern United States and October in south-central US.

Conclusion

Geographic and temporal distributions, based on community science observations, allow for more accurate predictions on the likelihood of encountering venomous Megalopygidae caterpillars.

Horizontal gene transfer underlies the painful stings of asp caterpillars (Lepidoptera: Megalopygidae)

Larvae of the genus Megalopyge (Lepidoptera: Zygaenoidea: Megalopygidae), known as asp or puss caterpillars, produce defensive venoms that cause severe pain. Here, we present the anatomy, chemistry, and mode of action of the venom systems of caterpillars of two megalopygid species, the Southern flannel moth Megalopyge opercularis and the black-waved flannel moth Megalopyge crispata. We show that megalopygid venom is produced in secretory cells that lie beneath the cuticle and are connected to the venom spines by canals. Megalopygid venoms consist of large aerolysin-like pore-forming toxins, which we have named megalysins, and a small number of peptides. The venom system differs markedly from those of previously studied venomous zygaenoids of the family Limacodidae, suggestive of an independent origin. Megalopygid venom potently activates mammalian sensory neurons via membrane permeabilization and induces sustained spontaneous pain behavior and paw swelling in mice. These bioactivities are ablated by treatment with heat, organic solvents, or proteases, indicating that they are mediated by larger proteins such as the megalysins. We show that the megalysins were recruited as venom toxins in the Megalopygidae following horizontal transfer of genes from bacteria to the ancestors of ditrysian Lepidoptera. Megalopygids have recruited aerolysin-like proteins as venom toxins convergently with centipedes, cnidarians, and fish. This study highlights the role of horizontal gene transfer in venom evolution.

Exploring the antibacterial potential of venoms from Argentinian animals

The resistance to antimicrobials developed by several bacterial species has become one of the main health problems in recent decades. It has been widely reported that natural products are important sources of antimicrobial compounds. Considering that animal venoms are under-explored in this line of research, in this study, we screened the antibacterial activity of venoms of eight snake and five lepidopteran species from northeastern Argentina. Twofold serial dilutions of venoms were tested by the agar well-diffusion method and the minimum inhibitory concentration (MIC) determination against seven bacterial strains. We studied the comparative protein profile of the venoms showing antibacterial activity. Only the viperid and elapid venoms showed remarkable dose-dependent antibacterial activity towards most of the strains tested. Bothrops diporus venom showed the lowest MIC values against all the strains, and S. aureus ATCC 25923 was the most sensitive strain for all the active venoms. Micrurus baliocoryphus venom was unable to inhibit the growth of Enterococcus faecalis. Neither colubrid snake nor lepidopteran venoms exhibited activity on any bacterial strain tested. The snake venoms exhibiting antibacterial activity showed distinctive protein profiles by SDS-PAGE, highlighting that we could reveal for the first time the main protein families which may be thought to contribute to the antibacterial activity of M. baliocoryphus venom. This study paves the way to search for new antibacterial agents from Argentinian snake venoms, which may be a further opportunity to give an added value to the local biodiversity.

Unraveling the distinctive venomous features of the saturniid Hylesia sp.: An integrative approach of a public health concern in Argentina

The saturniid genus Hylesia is well known for the cutaneous lepidopterism induced by airborne setae on contact with the skin. Although several cases of such dermatitis have been reported in Argentina, no information about their venoms and toxicological implications on human health is available yet. Thus, we conducted a morphological analysis of the setae/spines and a toxinological characterization (through biological assays and proteomic techniques) of the bristle extract from caterpillars and moths of Hylesia sp. from Misiones, Argentina. By scanning electron microscopy, we revealed the various and distinctive types of urticating structures: harpoon-shaped or spiny setae in caterpillars, and setae with barb-like structures in female moths. Their venom electrophoretic profiles were substantially different, presenting proteins related to toxicity, such as serpins and serine peptidases. The female moth venom exhibited higher caseinolytic activity than the caterpillar venom, and coincidentally only the former noticeably hydrolyzed fibrinogen and gelatin. In addition, the female venom displayed a dose-dependent procoagulant effect. The injection of this venom into mouse skin led to the rapid detection of an increased number of intact and degranulated mast cells in the dermis; a few areas of focal subcutaneous hemorrhage were also observed after 5 h of injection. Altogether, this study provides relevant information about the pathophysiological mechanisms whereby Hylesia sp. from northeastern Argentina can induce toxicity on human beings, and paves the way for treatment strategies of accidents caused by this saturniid lepidopteran.

Lonomia envenomation in Brazil: an epidemiological overview for the period 2007-2018

BACKGROUND

Among the Lepidoptera with medical importance in Brazil, larvae of Lonomia moth (Saturniidae: Hemileucinae) stand out by being the etiological agent of the lonomism, a form of erucism in which the most troubling symptoms include systemic hemorrhage that can lead to death.

METHODS

This study provides an epidemiological overview of accident notifications with Lonomia registered by the Brazilian Reportable Disease Information System (SINAN) between 2007 and 2018. The categories of sociodemographic aspects of the victim, accident characteristics, and clinical data (6,636 records) were analysed by the chi-square test for goodness of fit (α=0.05). By the same test, accident frequencies by month, year, and state were also compared. To explore the spatial distribution of notifications and to identify significant space-time and purely spatial clusters, a spatial scan statistic (SaTScan) was used.

RESULTS

The epidemiological profile of most of the victims had at least one of the following characteristics: male, >50 y of age, ethnically classified as white, and with a low level of education. Accidents in urban areas were as frequent as in rural areas. A higher frequency of non-work-related accidents was detected. Victims were mostly stung on the upper limbs. Most victims received medical care within the first 3 h after the accident. Most cases were classified as mild, although 12 deaths were reported. The south states of Brazil concentrate the highest frequencies of notifications. Summer was the season with the greatest number of cases, and the majority of the notifications occurred between 2017 and 2018.

CONCLUSION

These results provide an overall and current situation assessment of the lonomism in Brazil, and they should enable health authorities to improve the management of this envenomation in states/regions that share the high epidemiological risk of exposure to Lonomia.

Identification of Novel Toxin Genes from the Stinging Nettle Caterpillar Parasa lepida (Cramer, 1799): Insights into the Evolution of Lepidoptera Toxins

Simple Summary

Many caterpillar species can produce toxins that cause harmful reactions to humans, varying from mild irritation to death. Currently, there is very limited knowledge about caterpillar toxin diversity, because only a few species have been investigated. We used the transcriptome technique to identify candidate toxin genes from the nettle caterpillar Parasa lepida (Cramer, 1799). It is a common pest of oil palm, coconut, and mango in South and South-East Asia, which can cause severe pain and allergic responses to those in contact with them. We reported 168 candidate toxin genes. Most of them are members of the toxin genes families commonly recruited in animal venoms such as serine protease and serine protease inhibitors. However, we identified 21 novel genes encoding knottin-like peptides expressed at a high level in the transcriptome. Their predicted 3D structures are similar to neurotoxins in scorpion and tarantula. Our study suggests that P. lepida venom contains diverse toxin proteins that potentially cause allergic reactions and pain. This study sheds light on the hidden diversity of toxin proteins in caterpillar lineage, which could be future fruitful new drug sources.

Abstract

Many animal species can produce venom for defense, predation, and competition. The venom usually contains diverse peptide and protein toxins, including neurotoxins, proteolytic enzymes, protease inhibitors, and allergens. Some drugs for cancer, neurological disorders, and analgesics were developed based on animal toxin structures and functions. Several caterpillar species possess venoms that cause varying effects on humans both locally and systemically. However, toxins from only a few species have been investigated, limiting the full understanding of the Lepidoptera toxin diversity and evolution. We used the RNA-seq technique to identify toxin genes from the stinging nettle caterpillar, Parasa lepida (Cramer, 1799). We constructed a transcriptome from caterpillar urticating hairs and reported 34,968 unique transcripts. Using our toxin gene annotation pipeline, we identified 168 candidate toxin genes, including protease inhibitors, proteolytic enzymes, and allergens. The 21 P. lepida novel Knottin-like peptides, which do not show sequence similarity to any known peptide, have predicted 3D structures similar to tarantula, scorpion, and cone snail neurotoxins. We highlighted the importance of convergent evolution in the Lepidoptera toxin evolution and the possible mechanisms. This study opens a new path to understanding the hidden diversity of Lepidoptera toxins, which could be a fruitful source for developing new drugs.

Caterpillar Venom: A Health Hazard of the 21st Century

Caterpillar envenomation is a global health threat in the 21st century. Every direct or indirect contact with the urticating hairs of a caterpillar results in clinical manifestations ranging from local dermatitis symptoms to potentially life-threatening systemic effects. This is mainly due to the action of bioactive components in the venom that interfere with targets in the human body. The problem is that doctors are limited to relieve symptoms, since an effective treatment is still lacking. Only for Lonomia species an effective antivenom does exist. The health and economical damage are an underestimated problem and will be even more of a concern in the future. For some caterpillar species, the venom composition has been the subject of investigation, while for many others it remains unknown. Moreover, the targets involved in the pathophysiology are poorly understood. This review aims to give an overview of the knowledge we have today on the venom composition of different caterpillar species along with their pharmacological targets. Epidemiology, mode of action, clinical time course and treatments are also addressed. Finally, we briefly discuss the future perspectives that may open the doors for future research in the world of caterpillar toxins to find an adequate treatment.

Understanding toxicological implications of accidents with caterpillars Megalopyge lanata and Podalia orsilochus (Lepidoptera: Megalopygidae)

Megalopygids Megalopyge lanata and Podalia orsilochus are common causative agents of accidents in agricultural workers. These accidents are provoked by dermal contact at their larval stage and are characterized by cutaneous reactions, such as burning pain, edema and erythema, typically mild and self-limited. There is very little information about their venoms and their toxicological implications on human health. Thus, we employed proteomic techniques and biological assays to characterize venoms (bristle extracts) from caterpillars of both species collected from Misiones, Argentina. The electrophoretic profiles of both venoms were substantially different, and they presented proteins related to toxicity, such as serinepeptidases, serpins and lectins. P. orsilochus venom exhibited higher caseinolytic activity than M. lanata venom, agreeing with the fact that only P. orsilochus venom hydrolyzed human fibrin(ogen). In addition, the latter shortened the clotting time triggered by calcium. While the venom of M. lanata induced a mild inflammatory lesion in mouse skin, P. orsilochus venom caused prominent necrosis, inflammatory infiltration and hemorrhage at the site of venom injection. On the other hand, P. orsilochus venom was better recognized by Lonomia obliqua antivenom, although many of its proteins could not be cross-reacted, what may explain the difference in the clinical manifestations between accidents by Podalia and those by Lonomia. Altogether, this study provides relevant information about the pathophysiological mechanisms whereby both caterpillars can induce toxicity on human beings, and paves the way for novel discovery of naturally occurring bioactive compounds.

Management of severe pain after dermal contact with caterpillars (erucism): a prospective case series

CONTEXT

Erucism, envenomation caused by dermal contact with larval forms of moths, may result in intense local pain, mainly after contact with puss caterpillars (family Megalopygidae).

OBJECTIVE

To evaluate the response to different treatments for controlling severe pain in a case series of erucism in Campinas, southeastern Brazil.

PATIENTS AND METHODS

Prospective cohort study. A Numeric Pain Rating Scale (NPRS 0-10) was used to assess pain intensity in the Emergency Department (ED). Pain was considered as severe upon ED admission (T0) when the NPRS was ≥8.

INCLUSION CRITERIA

age ≥8 years old, severe pain at T0, with continuous assessment of pain intensity in all patients using the NPRS during the ED stay (T5, T15, T30, T60 min and at discharge).

RESULTS

Fifty-five patients fulfilled the inclusion criteria and were divided into three groups according to the initial treatment at T0: local anesthesia alone with 2% lidocaine (group 1, n = 15), local anesthesia and analgesics (group 2, n = 26) and analgesics without local anesthesia (group 3, n = 14). Most patients were admitted within 2 h after dermal contact with the stinging bristles of caterpillars (median =90 min, IQR: 40-125 min). In 22 cases (40%), the caterpillar was brought for identification (Podalia spp., n = 18; Megalopyge spp., n = 4). There was a significant decrease in pain from T5 onwards with all of the treatments. When the short-term response (T5 and T15) was considered, analgesia was more effective in groups 1 and 2 compared to group 3 (p < .01). Additional analgesia (from T5 until discharge) was frequently required (n = 25/55), mainly in group 1 (n = 11/15). The median length of stay in the ED was 120 min (IQR: 80-173 min).

CONCLUSIONS

The association of local anesthesia with analgesics was apparently a good combination for the rapid management of severe pain in the ED.

Venomous caterpillars: From inoculation apparatus to venom composition and envenomation

Envenomation by the larval or pupal stages of moths occurs when the victim presses their hairs. They penetrate the subcutaneous tissue, releasing toxins such as proteolytic enzymes, histamine and other pro-inflammatory substances. Cutaneous reactions, including severe pain, oedema and erythema are frequent local manifestations of caterpillar envenomation, but, in some cases, the reactions can evolve into vesicles, bullae, erosions, petechiae, superficial skin necrosis and ulcerations. Alternatively, some individual can develop allergic reactions, renal failure, osteochondritis, deformity and immobilization of the affected joints and intracerebral bleeding. Caterpillars produce venom to protect themselves from predators; contact with humans is accidental and deserves close attention. Their venoms have not been well studied, except for toxins from some few species. The present review brings together data on venomous caterpillars of moths, primarily addressing the available literature on diversity among the different families that cause accident in humans, the structures used in their defense, venom composition and clinical aspects of the envenomations. Understanding the molecular mechanisms of action of caterpillars' toxins may lead to the development of more adequate treatments.