Parasitic Skin Infestations

As the skin is constantly exposed to the environment, it represents a common portal of entry for different parasites. Infestations with parasites can cause systemic diseases in humans, but often result in cutaneous lesions which are on the rise in dermatology clinical practice due to the increase of travel and immigration.

Despite the considerable burden parasitic skin infestations can cause, their significance has often been neglected by the health-care providers and scientific community alike. Furthermore, the debilitating impact a persistent itch can have must be taken into account when assessing these conditions.

Protozoan and helminth infestations

Protozoan infestations characterized by a transient skin phase following infestation via the cutaneous route include African trypanosomiasis (sleeping sickness) and South American trypanosomiasis (Chagas disease). In the former vesicular lesion develops approximately five days after a bite of a tsetse fly, whereas the latter is characterized by a marked, usually unilateral periorbital edema known as Romaña’s sign.

Cutaneous amebiasis is a rare skin manifestation of a disease caused by Entamoeba histolytica – a protozoan parasite found worldwide. The disease initially presents as a deep-seated swelling that ulcerates and forms a necrotic base with blood and pus.

A myriad of helminthic diseases can present with various dermatologic signs and symptoms such as skin nodules, migratory skin lesions, cysts and itching. Various cestode or tapeworm species (such as Taenia solium, Echinococcus granulosus and Spirometra spp.) may form cysts under the skin.

Infestation with different nematode or roundworm species (most often zoonotic species that accidentally infect humans) can result in swelling and subcutaneous lesions at the point of entry. Some of the nematodes infecting the skin include filarial species such as Loa loa, Mansonella streptocerca, Onchocerca volvulus, as well as Gnathostoma spp. and Dirofilaria spp.

Trematode (fluke) infestations that involve the skin are scarce; for example, invading cercariae in schistosomiasis may provoke a transient allergic rash that lasts up to five days (cercarial dermatitis) while traveling to the blood stream. The non-human schistosome species can also cause similar type of dermatitis known as pelican itch or swimmer’s itch.

Ectoparasites

Scabies is a cosmopolitan cutaneous infestation caused by the human scabies mite (Sarcoptes scabiei var. hominis) and acquired by personal direct skin contact. The scabies mite lays eggs in a previously burrowed tunnel of up to 4 millimeters into the superficial layer of the epidermis.

Papules (with or without excoriation) and S-shaped burrows are the classical lesions of scabies, which together with intense pruritus support the diagnosis of this condition. Moreover, individuals of all age groups that suffer from chronic crusted scabies may present with eczema, impetiginized plaques and hyperkeratosis masking the typical clinical sings of scabies.

Three species of lice are known to infest humans – the head louse (Pediculus humanus capitis), the body louse (Pediculus humanus corporis) and the pubic louse (Pthirius pubis). All of them feed on the blood of the host, which causes inflammation, itching and skin discoloration.

Similarly, fleas bite humans in order to obtain a blood meal, producing in turn a localized inflammatory reaction. A clinical presentation of itching with papules, vesicles or small nodules (often in clusters) on both feet and lower legs is characteristic, while scratching can result in bacterial superinfections.

Sources

  1. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3552304/
  2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1215558/
  3. http://www.who.int/bulletin/volumes/87/2/07-047308/en/
  4. http://www.cdc.gov/parasites/scabies/gen_info/faqs.html
  5. http://www.tropmed.org/wp-content/uploads/2014/07/chapter10-2.pdf
  6. Chopra S, Knight MA, Vega-Lopez F. Dermatological Problems. In: Cook GC, Zumla A, editors. Manson's Tropical Diseases, Twenty-second Edition. Elsevier Health Sciences, 2009; pp. 333-372.

Further Reading

Last Updated: Aug 23, 2018

Dr. Tomislav Meštrović

Written by

Dr. Tomislav Meštrović

Dr. Tomislav Meštrović is a medical doctor (MD) with a Ph.D. in biomedical and health sciences, specialist in the field of clinical microbiology, and an Assistant Professor at Croatia's youngest university - University North. In addition to his interest in clinical, research and lecturing activities, his immense passion for medical writing and scientific communication goes back to his student days. He enjoys contributing back to the community. In his spare time, Tomislav is a movie buff and an avid traveler.

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Comments

  1. Cindy Wright Cindy Wright United States says:

    I have been very sick for a few years, this is constant morning noon and night. I wake get out of bed, nausea and headache come on severe nausea. My limbs are cold, my face is flushed red with white dripping looking white areas that are cold, I get a rash with swelling on my body random areas. Severe neck pain that comes and goes now but 2 years ago I could barely get out of bed. Now I been on methotrexate and hydroxychloriquine, but I woke with eye pain and watering eye, I took a picture of a white pointy spot where the pain was, I went to ER and he couldn't find it, it is some kind of worm. I have severe burning feeling that is localized to several areas. Where the initial tick bite was back left thigh my muscle and tissue is eaten away. My muscle convulse left leg. Blood counts all over the place, monocytes high, mcv.  I believe I have a terrible co infection of lymes disease, thigh and leg swelljng, blood clots.... very painful. Brain problems. Ringing in ear, face pain numbness swelling.  Please help me if you can. Cindy 715-791-4801

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