PA CME : Dermatology – Insects and Parasites

Insects and Parasites Part 1

There are many different little critters that can wreck havoc on the skin. It is important to know the different insects and parasites, how they will affect the skin and body, and how to get rid of them. Below is a summary of common insects and parasites that you might see on a patient:

Head Lice

These guys are six legged insects, about 2-3 mm long (about the size of a sesame seed) which can make then difficult to see. They can live up to 3 weeks and they feed every 3-6 hours. They cling to the hair follicle with their claws. Lice eggs are called nits and they are stuck on the hairs near the scalp (about ¼” from the scalp) and more difficult to view than the adult lice since they are even smaller. They hatch in 5-10 days and become adults after 10 days. Head lice are most common in children who attend daycare, preschool, or elementary school since these children play more closely and have more “hair to hair” contact. Lice prefer a host with clean hair. Family members of these children are also more likely to get lice than persons not around younger children. Children can spread head lice to each other via hair-to-hair contact, sharing of hairbrushes, hats, or anything that helps the lice to its new host since they cannot jump or fly to a new host.

When looking for head lice the most common place to find them is on the hair at the back of the neck or behind the ears. You may see many white 1 mm nits on the hair shaft, excoriations, adult insects, and papular bite marks. You might even find a secondary infection due to the itching. The patient may or may not have an itchy head depending on how long they have been infested for.

Everyone in the family must be treated at the same time. Over the counter treatment for lice includes a topical 1% permethrin rinse. Listerine and also mayonaise home treatments have also been seen to work. Prescription options includes: permethrin 5% cream rinse, Malathion (must be > 6 years old), Ulesfia (must be > 6 months old), Spinosad 0.9% (must be > 4 years old), and Ivermectin lotion 0.5% (must be > 6 months old). The treatments kills the adults and nits but they don’t remove them from the hair. Be careful not to overuse the lotions as they can be poisonous.

The household, school, or wherever the patient spends time needs to be cleaned of lice too by washing all recently worn clothing with hot water or pressing them with an iron. Don’t forget to disinfect and hats, combs and brushes. It is important that you educate patients on house lice spreads and how to prevent it in the future.

Pubic Lice

This is a 2 mm flat, crab-like creature that hold onto the hair shaft with once pincer and attaches the eggs to the hair. They bite the host and can be passed by skin to skin contact. They survive for 1 or 2 days. They are most often found in the genital area on pubic hair but may also be found on other densely hairy areas such as the thighs, upper abdomen, chest, axillae, and even the eyebrows.The patient may experience mild or severe itching or might see a gray, flake-like, slow moving bug.

The treatment for pubic lice is similar to that of head lice but the treatment is from the lower abdomen to the knees. Sexual partners need to be treated as well. Educate patients on how pubic lice are spread and how to prevent them in the future.

Fleas

Fleas are tiny bugs that are about the size of a tip of a pen. They have thin, flat bodies with hard shells. If a patient has pets in their house then they are at a higher risk of getting flea bites. The bit appears as a small central hemorrhagic lesion surrounded by erythema and urticaria. This is actually the body’s reaction to the flea’s saliva, not the bite itself. The bites are a firm, itchy nodule that are grouped in about 2-3 in each area with more possible. These bites are typically found on the lower extremities or feet.

Treatment for flea bites includes calamine lotion to suppress itching and also antihistamines for the itch and reaction. The animals in the house of the patient need to be treated as this is likely where the fleas came from. Clothes and bedding need to be thoroughly cleaned if infested. Flea bombs are available for purchase if infestation is suspected. Patients need to be educated on the importance of treating their household pets for fleas for not only their pet’s health but for their own.