What is the Giant Silkworm Moth?
The giant silkworm moths are members of the Saturniidae family. They range in size from medium to very large moths, they have hairy, stubby bodies and feathery antennae. A female’s antenna can be a feathery or a thin filament. These moths only live a few weeks because they do not feed as they have a little or absent mouthpart. Many species of this family have prominent eyespots and decorated with bright colors.
75 different species of Lonomia Obliqua live in North America north of Mexico and about 16 species live in Missouri including luna, imperial, rosy maple, royal moths, and more.
Lonomia Obliqua larvae are fairly large and rounded with tubercles and spines or hairs. These hairs can cause skin irritation or sting. The larvae or caterpillar stage corresponds with the spring and summer months and this is of concern because this increases the chances of contact with humans.
History and Exposure
Exposure to Giant silkworm moth larvae (caterpillars) and their bristles can cause a variety of symptoms ranging “from mild discomfort to systemic bleeding” (3). The earliest records of exposure to lepidopteran caterpillars date back to 1912 in Brazil and were described by Zoroastro Alvarenga. Interactions with Lonomia Obliqua occur mostly through the skin on the upper limbs of children and rural workers. There has shown to be a higher incidence of accidents with Lonomia Obliqua in the spring and summer months, which is the time they are in the caterpillar stage, as stated earlier.
Route of Administration and Effects
Giant silkworm larvae can release its toxins with anticoagulant properties through its bristles and if it comes into contact with the skin it can cause leukocytosis, anemia, bruising, hematuria, hematoma, vomiting, nausea, headache, a burning sensation at the site, swelling, redness, and pain. Clinically, fibrin degradation products increase, coagulation factor levels decrease, and clotting time increases. However, exposure does not cause a decrease in platelets as usually seen in coagulopathies.
Skin contact symptoms
- Pain, redness and swelling
- Burning sensation at the site of contact
- Headache and nausea
- Hematoma and hematuria
Additional clinical signs following skin contact
- Increased clotting time
- Increase in fibrin degradation products
- Decrease in coagulation factor levels
It is important to note that more severe cases of poison from Lonomia Obliqua have been studied in relatively recent times, and more surprising findings have come to light. Experimental findings have led researchers to believe that the venom released from Lonomia Obliqua larvae damages the blood-brain barrier. Renal failure has also been reported.
Mechanism of action
Systemic vascular and inflammatory disorders can be stimulated by the venom of Lonomia Obliqua. By increasing intravascular thrombin ( a protein that causes blood clotting) concentration and disrupts endothelial cell monolayers, leading to hemorrhagic conditions and few leukocytes in test animals (5).L. Obliqua is thought to indirectly cause an up-regulation of several genes involved in the amplification and generation of the clinical manifestations listed above. There is evidence that supports that Obliqua venom has bioactive peptides that change the migratory characteristics of different cell types.
Cell migration involves molecules on cells itself, and in the extracellular matrix, and L. Obliqua venom seems to interfere with both which can influence cell migration and blood vessel permeability. an important part of cell migration is coordinated by the Rho family GTPases. Rac1 promotes or initiates actin assembly which is involved in cell to extracellular matrix adhesion and cell to cell adhesion. When certain RhoGTPases regulators (Rho GAP 21, Rho GEF 12) are modified by LOBE (L.Obliqua Bristle extract), this may cause activation Rac1 and cause an increase in cell membrane protrusion. This makes all of the previously mentioned molecules good biomarkers in the clinical setting.
Currently, the only known treatment for L. Obliqua envenomation is Lonomia Antivenom (LAV).
(1) http://www.naturenorth.com/spring/bug/silkmoth/Fsilk2.html Accessed July 27th, 2020
(2) http://web.b.ebscohost.com.proxy.lib.ohio-state.edu/ehost/pdfviewer/pdfviewer?vid=2&sid=1ddac6a9-86ce-4b27-8281-ced3b1fb6fb9%40pdc-v-sessmgr05 Accessed July 27th, 2o2o
(3) https://www-sciencedirect-com.proxy.lib.ohio-state.edu/science/article/pii/S0041010104003198 Accessed July 27th, 2020
(4) https://onnaturemagazine.com/butterfly-and-moth-guide.html Accessed July 27th, 2020
(5) https://www-sciencedirect-com.proxy.lib.ohio-state.edu/science/article/pii/S0041010119300601 Accessed July 28th, 2020