What is Butterfly, Moth, and Caterpillar Envenomation?
The Lepidoptera group includes the moths, butterflies, and their larvae, known as caterpillars. Some of these caterpillars around the globe have spines or hairs that release a harmful substance when touched, which can irritate human skin. Common signs of this irritation include localized pain, swelling, and skin turning red.
However, some types of caterpillars can cause more severe injuries, including allergic reactions, issues with blood clotting, bleeding in the brain, kidney damage, coordination problems, difficulty speaking, arthritis, wheezing, and shortness of breath.
“Lepidopterism” is a term used to describe skin and bodily reactions that occur after coming into contact with moths or butterflies. It comes from the Greek words for scale and wing. Another term, “Erucism,” is used to specifically refer to a skin inflammation caused by contact with caterpillars that have irritating hairs. Erucism comes from a Latin word meaning caterpillar.
In the United States, there are over 50 species of venomous caterpillars. One of the most toxic is the puss moth caterpillar, known also by several other names including the asp, tree asp, and wooly slug. This caterpillar, which is found in the south-east and south-central US, particularly Texas, Louisiana, and Florida, is most common from late spring till early fall. It can often be found in trees and bushes near homes, schools, and parks. The caterpillar has a furry body that contains short hollow spines attached to a venom sack that releases venom upon contact.
There are other venomous caterpillars in the US, including the flannel moth, the lo moth, the saddleback moth, and the hickory tiger moth. In South America, especially Brazil, the Lonomia obliqua caterpillars can cause severe pain and a condition that leads to excessive bleeding. In Australia, certain types of caterpillars also have medical significance due to their venom. In Mediterranean and Central Europe, the Pine processionary caterpillars are a major issue for pine forests and those working in them. In Nigeria, the Anaphe venata caterpillar, while being a crucial source of protein, can also cause a deficiency in vitamin B1, leading to a condition similar to dry beriberi. Additionally, in China and Brazil, certain types of caterpillars have been associated with significant joint disease.
What Causes Butterfly, Moth, and Caterpillar Envenomation?
Caterpillars, rather than butterflies and moths, are usually the cause of skin and eye irritation due to certain species of insects. This happens when one comes into physical contact with a caterpillar’s bristles, referred to as “setae”. These hairlike, hollow structures are linked to poison glands that store venom. If someone touches these bristles, they can break and release this venom.
The bristles can stick into the skin or into the body’s mucus layers, causing irritation. This reaction is different from the direct response to the venom. Some moths also have these bristles, but adult insects usually lose these irritating bristles once they leave their cocoons, making them less harmful. However, not all caterpillars produce venom.
If someone’s eyes come into contact with caterpillar bristles or their fluid (called “hemolymph”), it can cause eye inflammation, known as “acute scleritis” or “ophthalmia nodosa”. What might start as simple eye redness can turn into serious inflammation of the whole eye if the bristles penetrate the cornea (the clear front part of the eye). In rare instances, this condition can even cause cataracts (clouding of the lens of the eye).
The reactions are mostly due to the toxins in the caterpillar’s bristles or fluid, or due to immune system responses that make one extra sensitive – a sort of allergic reaction usually resulting from direct contact. The caterpillar’s bristles can also be spread through the air by the wind or transferred by pets or other natural objects.
Risk Factors and Frequency for Butterfly, Moth, and Caterpillar Envenomation
Caterpillars, which belong to the Lepidoptera species, are found all over the world. However, only a few species can cause harmful reactions in humans. In 2021, there were about 1014 reported cases of people coming into contact with caterpillars in the United States. People usually come into contact with caterpillars accidentally. Nearly half of the reported cases are adults over 20 years old, while about a third are children 12 years or younger. Since children naturally love exploring their environment, they are slightly more likely to encounter caterpillars. There are more cases among men than women. Thankfully, no deaths were reported due to contact with caterpillars. Even so, the real number of people affected may be higher than reported, given that most cases of caterpillar contact cause mild reactions that do not require medical attention.
People often come into contact with caterpillars unintentionally, and this can be influenced by where they are located and the time of year. Working in jobs that require tree climbing or close contact with plants increases the risk in adults. In Brazil, for example, rubber tappers, who harvest latex from rubber trees, often encounter the Premolis semirufa caterpillar (locally known as pararama). This caterpillar can cause severe reactions and is considered an occupational hazard for rubber tappers. Certain species of caterpillars can release their setae—or hair—into the air, causing more people to be exposed, especially during seasons when these caterpillars are plentiful.
The number of cases usually increases during the spring and summer months, a time when kids tend to spend more time outdoors, whether on school recess or camping and hiking trips. This is also when there is more logging activity and landscaping, which can disturb caterpillar habitats. One example of a seasonal disease caused by caterpillar contact is ophthalmia nodosa, which typically happens during the months of August-October, when caterpillars are plentiful. However, the exact number of cases is unknown.
Signs and Symptoms of Butterfly, Moth, and Caterpillar Envenomation
Caterpillar exposure can result in two types of reactions: stinging reactions and itchy reactions. Both can differ based on the type of caterpillar involved.
Stinging caterpillars have hollow spines that release venom upon contact, which leads to a painful burning sensation, swelling, and redness. This could also result in blisters and a patterned rash in 2 to 3 hours. You can also experience systemic symptoms like nausea, fever, headache, and more with certain species. An example of a distinctive pattern could be the “M” shape left by opercularis stings.
On the other hand, coming into contact with itchy caterpillars leads to reactions that can be mechanical, allergic or due to chronic irritation. This can result in intense itching and other skin reactions, dermatitis, and in severe cases, anaphylaxis. For instance, the Australian caterpillar Ochrogaster lunifer and the Thaumetopoea pityocampa found in Asia, North Africa, and Europe can cause such reactions.
Coming into contact with certain species can result in more severe conditions. For example, Dendrolimiasis is caused by the central Asian pine tree lappet caterpillar found in China. It can cause a variety of symptoms like inflammation, osteoarthritis, and rarely, acute scleritis. You might also experience fever, fatigue, headaches and more.
Pararamose is another disease similar to Dendrolimiasis, which comes from direct contact with a Brazilian caterpillar called the Premolis semirufa. This is a major concern for people working in rubber tree plantations in the Amazon rainforest. The symptoms are similar and could include painful itching, arthritis, and joint malformation due to regular exposure.
There’s also a dangerous syndrome caused by the South American Lonomia sp caterpillars in Brazil, Venezuela, and northern Argentina. It can cause a severe clotting condition similar to disseminated intravascular coagulation (DIC). Of all the species, Lonomia obliqua from Southern Brazil and Lonomia achelous from Venezuela and Northern Brazil are notorious for causing DIC. If untreated, it could have high fatality rates due to pulmonary and intracerebral hemorrhage with acute kidney failure. The first symptoms are intense burning, redness, swelling, heat, and blistering. The clotting disorder can happen between 6 to 72 hours of envenomation, but in case of L obliqua, it may occur within 4 to 6 hours.
Testing for Butterfly, Moth, and Caterpillar Envenomation
If you’ve had a reaction due to a caterpillar sting that only affects your skin, usually, you won’t need any laboratory or imaging tests. However, depending on the species of caterpillar and the symptoms you’re experiencing, your doctor might suggest different tests.
These might include a complete blood count, which is a measure of the number of blood cells in your body. They may also suggest tests to check how well your blood is clotting, this includes things like Prothrombin time, activated partial thromboplastin time, fibrinogen level, fibrin degradation products, and D-dimer. A basic metabolic panel might also be done, particularly focusing on your BUN and creatinine levels, which can indicate how well your kidneys are functioning.
If you’ve been stung near your eye, you might need a ‘slit-lamp examination to check for any issues in your eyes. A special fluorescence stain might also be used on the affected eye to make sure there aren’t any scratches or damage to your cornea.
Should you have any significant respiratory symptoms, like difficulty in breathing, a chest X-ray might be suggested. An electrocardiogram (ECG) might also be done if your heart rate is too fast or irregular, which could indicate heart issues. Furthermore, they may suggest a urinalysis to check for blood and protein in your urine, which can signal kidney problems.
Treatment Options for Butterfly, Moth, and Caterpillar Envenomation
If you’ve been stung or bitten by caterpillars, it’s important to wash the affected area with soap and water and gently dry it using a hair dryer or fan. Using adhesive tape on the area can help remove any remaining hairs. Take off any tight clothing or jewelry that could become uncomfortable if swelling occurs. You can use rubbing alcohol and an ice pack on the sting to help cool the area. It might also be a good idea to get a tetanus shot, just in case.
If caterpillar hairs get in your eye, you should get medical help immediately. Doctors may want to wash your eyes out with a saline solution and give you a local anesthetic to make you more comfortable. They’ll carefully check your eye for caterpillar hairs and remove any they find under a microscope. To reduce any swelling and infection, the doctors may also suggest a combination of steroids, lubricants, and antibiotics.
In more serious cases, an eye specialist may need to perform surgery to remove any nodules or hairs that have gotten into your eye. They may use a variety of approaches, including steroids and surgery, depending on the severity of your case.
Topical anesthetics, mild painkillers, and stronger narcotics can be used to manage pain. Doctors may also suggest using steroids to further reduce swelling. If you also have skin symptoms such as itching or hives, oral antihistamines may be prescribed. For those with severe respiratory symptoms or an allergic reaction, stronger treatments like epinephrine and systemic steroids may be necessary.
In the case of dendrolimiasis, a disease caused by exposure to certain types of caterpillars, the recommended treatment is usually immediate surgery to remove sinus tracts and affected cartilage, which can help to prevent permanent deformities. If you experience a bleeding syndrome from exposure to dangerous caterpillars, like the L obliqua caterpillar, doctors may administer clotting factors, platelets, and cryoprecipitate. An antidote for this syndrome is also available in Brazil.
If you suspect that you’ve been envenomated by a Lonomia caterpillar, it’s crucial to consult a hematologist. The treatments for different species vary and can be quite serious. You might also need treatments such as cryoprecipitate, purified fibrinogen, and antifibrinolytics. However, you should avoid whole blood or fresh plasma transfusions, as they may worsen the situation.
For those who experience seasonal ataxia, a condition caused by the African silkworm, the doctor may prescribe 100 mg of oral thiamine every 8 hours, which could reduce symptoms within 2 days. For any caterpillar envenomation, it’s also recommended that you consult a medical toxicologist or regional poison control center for further guidance on your treatment.
What else can Butterfly, Moth, and Caterpillar Envenomation be?
If you’re stung by a bug from the Lepidoptera family, which includes butterflies and moths, the symptoms you experience could be mistaken for a range of other conditions, such as:
- Skin conditions, including atopic dermatitis, allergic dermatitis, and contact dermatitis
- Allergic reactions
- Stings or bites from other bugs and animals, like insects, centipedes, millipedes, scorpions, tarantulas, black widow spiders, and brown recluse spiders
- Corneal abrasions and ulcers which can be caused by foreign bodies stuck in the eye
- Poisoning from plants in the Toxicodendron family
- Diseases involving blood vessels such as Henoch Schonlein purpura (HSP) or Immunoglobulin A (IgA) Vasculitis
- Idiopathic thrombocytopenic purpura (ITP), a disorder that can lead to easy or excessive bruising and bleeding
- Eye inflammation conditions like iritis and uveitis
What to expect with Butterfly, Moth, and Caterpillar Envenomation
The outlook for people stung by creatures from the Lepidoptera group (which includes butterflies and moths) is typically very good. The exceptions are severe eye injuries or continuous whole-body symptoms. However, even with these more severe cases, complete recovery is usually expected if the patient receives specialized eye care or other expert treatment at a major hospital.
Deaths from caterpillar stings are infrequent, and are typically due to lack of medical treatment or occurring in remote, hard-to-reach locations.
Possible Complications When Diagnosed with Butterfly, Moth, and Caterpillar Envenomation
The complications from getting caterpillar hair in your eyes vary, depending on how far they penetrate and the effect of the irritating toxins. Brief contact with these hairs can cause symptoms like swelling in the white part of the eye, scratches on the cornea, eyelid swelling, and a sensation of something in the eye that might last weeks.
Further potential problems include persistent inflammation of the cornea and conjunctiva, growths on the cornea, chronic inflammation of the white of the eye, inflammation inside the eye, cataracts, and vision problems. If the toxins become a systemic problem, meaning they affect the entire body, there can be problems with blood clotting and kidney function, which are usually temporary, but in some cases, they may lead to long-term kidney issues.
Common Complications:
- Swelling in the white part of the eye
- Scratches on the cornea
- Swelling of the eyelids
- Foreign body sensation in the eye
- Persistent inflammation of the cornea and conjunctiva
- Growths on the cornea
- Chronic inflammation of the white of the eye
- Inflammation inside the eye
- Cataracts
- Vision impairment
- Problems with blood clotting
- Renal dysfunction
- Potential long-term kidney issues
Preventing Butterfly, Moth, and Caterpillar Envenomation
It’s very important to teach people, especially children, about the risks of touching caterpillars. A lot of people don’t know that some caterpillars can actually hurt us if we touch them. To prevent these kinds of insect bites or stings, it’s best not to touch caterpillars at all. This is especially important in places and times when there are lots of caterpillars around, like during spring and summer.
If you’re going to be outdoors in areas where caterpillars are common, there are also things you can do to protect yourself. Wearing safety glasses, long shirts and pants, work gloves, and a hat with a wide brim can help keep caterpillars away from your skin. You should also tuck your pants into your socks to stop caterpillars from getting up your legs.
If you ever do find a caterpillar on your skin, you should never try to remove it with your bare hands. Instead, you should use a stick or another tool to gently brush it away. This can help prevent the caterpillar from releasing more venom, which could lead to more severe symptoms.