Lonomia obliqua– The Giant Silkworm Moth

 

Introduction

The Giant Silkworm Moth is found in South America. Specimens have been sited in southern Brazil, Uruguay, Paraguay, and Argentina. The name Giant Silkworm moth has been given to several giant moths found in the Saturniidae family, but the focus here will be on Lonomia obliqua. While the adult form of the L. obliqua is fairly inconspicuous, the larval form can be deadly, causing more than a thousand cases of poisoning from 1997 to 2005, with several human deaths every year. These numbers are underestimated due to many accidents occurring in rural areas that are too distant to report.

The L. obliqua caterpillar form is covered in spiny protrusions that carry an extremely potent venom. These spines can easily puncture human skin and release the venom into the body. Caterpillars group together low on tree trunks during the day, increasing the risk of accidentally brushing or falling into the group. This grouping can also increase the severity of the poisoning, since the venom of many caterpillars could be released into the victim at once. Another aspect of increased poisonings is deforestation and planting of fruit trees. The caterpillars gather on the fruit plantations trees as they are a rich source of food and workers are put at risk.

History

Lonomia obliqua was originally described in 1855 by Francis Walker. In the 1960s, there was an epidemic of patients with hemorrhagic symptoms, causing massive bleeding through the body and into the brain, leading to death in several cases. The only common aspect of the incidents was the presence of L. obliqua at the site of poisoning. Since the 1980s, cases of L. obliqua toxicity have steadily increased, making the caterpillar one of the most important venomous animals in the area.

Toxicity

The caterpillar stage of the Lonomia obliqua (larval instars 1-6) have spines that contain a sack of venom at the base. When the spines penetrate skin, the venom flows through the hollow spine and into the victim. This toxin has potent anti-clotting agents that cause hemorrhagic symptoms. Toxic effects require 20-100 stings, depending on the size and age of the victim. This is easily acquired with the gregarious nature of the caterpillar.

 

Activity (toxin)	Source	MW (kDa)	Characteristics and observed effects
Prothrombin activation (Lopap)	Bristle extract	21	Serine protease, activity increased by Ca2+; consumption coagulopathy in vivo; cell survival in endothelial cell culture. Recombinant form produced in bacteria and yeast.
FXa-like	Bristle extract	21	Hydrolytic activity on S-2222 chromogenic substrate, Ca2+-independent; N-terminal sequence similar to Lopap.
Factor X activation (Losac)	Bristle extract	45	Serine protease, Ca2+-independent; Cell survival in HUVEC. Recombinant form produced in bacteria.
Phospholipase A2-like	Bristle extract	15	Indirect hemolytic activity in human and rat red blood cells in vitro, Ca2+-independent; intravascular hemolysis in vivo.
Fibrinogenolytic (Lonofibrase)	Hemolymph	35	αβ fibrinogenase activity; enable to affect fibrin cross-linked.
Hyaluronidase (Lonoglyases)	Bristle extract	49 53	β-endohexosaminidase activity; degradation of extracellular matrix.
Antiapoptotic	Hemolymph	51	Activity on Spodoptera frugiperda (Sf-9) cell culture.
Antiviral	Hemolymph	20	Antiviral activity against measles, influenza and polio viruses. Recombinant form produced in baculovirus/insect.
Nociceptive and Edematogenic	Bristle extract	NI	Nociception facilitated by prostaglandin production; edematogenic response facilitated by prostanoids and histamine.
Kallikrein-kinin system activation	Bristle extract	NI	Kinin release from low molecular weight kininogen; edema formation and fall in arterial pressure.
Platelet adhesion and aggregation	Bristle extract	NI	Direct platelet aggregation and ATP secretion; activity inhibited by p-bromophenacyl bromide, a specific PLA2 inhibitor.

Table 1.

Target Organs

The main target of L. obliqua venom is the blood. This causes widespread hemorrhagic symptoms, acute kidney failure, pulmonary hemorrhage, and intracranial hemorrhage.

Signs and Symptoms

Clinical Symptoms

• Local pain and inflammation starts immediately after envenomation
• A few hours after contact: headache, fever, vomiting, and lethargy
• Up to 72 hours after exposure: bleeding diathesis, hematomas, ecchymosis, hematuria, pulomonary and intracranial hemorrhage, and acute renal failure

Blood work

• Prolongation of coagulation paramaters
  • prothrombin time
  • partial activated thromboplastin time
• Decrease in plasma levels of:
  • fibrinogen
  • factors V and XIII
  • pre-kallikrein
  • plasminogen
  • protein C
  • alpha2-antiplasmin
• Increase in plasma levels of:
  • thrombin-antithrombin complex
  • fragment 1 and 2 from prothrombin activation
  • D-dimers

Treatment

The main treatment for L. obliqua toxicity is antifibrinolytics. Blood products should not be given until the hemorrhagic syndrome is resolved to avoid fueling the consumptive coagulopathy. There is an antiserum that is produced by the Butantan Institute in São Paulo, Brazil that effectively reverses the coagulation disorder caused by the venom.

References

1. A purified prothrombin activator from bristles of Lonomia obliqua caterpillars. (2000). Toxicon, 38(4), 521-522. doi: 10.1016/s0041-0101(00)80043-4
2. Chudzinski-Tavassi, A., & Carrijo-Carvalho, L. (2006). Biochemical and biological properties of Lonomia obliqua bristle extract. Journal Of Venomous Animals And Toxins Including Tropical Diseases, 12(2). doi: 10.1590/s1678-91992006000200002
3. Chudzinski-Tavassi, A., Alvarez-Flores, M., Carrijo-Carvalho, L., & Ricci-Silva, M. (2013). Toxins from Lonomia obliqua — Recombinant Production and Molecular Approach. Retrieved 14 July 2019, from https://www.intechopen.com/books/an-integrated-view-of-the-molecular-recognition-and-toxinology-from-analytical-procedures-to-biomedical-applications/toxins-from-lonomia-obliqua-recombinant-production-and-molecular-approach
4. Maggi, S., & Faulhaber, G. (2015). Lonomia obliqua Walker (Lepidoptera: Saturniidae): hemostasis implications. Revista Da Associação Médica Brasileira, 61(3), 263-268. doi: 10.1590/1806-9282.61.03.263
5. Pinto, A., Berger, M., Reck, J., Terra, R., & Guimarães, J. (2010). Lonomia obliqua venom: In vivo effects and molecular aspects associated with the hemorrhagic syndrome. Toxicon, 56(7), 1103-1112. doi: 10.1016/j.toxicon.2010.01.013