Author: Matt Klein, MD (EM Resident Physician, PGY-3, NUEM) // Edited by: Bill Burns, MD (EM Resident Physician, PGY-4 NUEM) // Expert Commentary: Abra Fant, MD

Citation: [Peer-Reviewed, Web Publication] Klein M, Burns B (2017, January 10). Infestations [NUEM Blog. Expert Commentary By Fant A]. Retrieved from


It’s just after signout on a busy Monday evening, and the Emergency Department (ED) is buzzing with activity as staff members scurry down the hallways and the waiting room teems with patients all itching to be seen. Skin crawling with excitement about the possibility of saving another life, you follow EMS into a room as they deliver your new patient, a middle aged male complaining of skin irritation. Watching him slowly snake his arm into the hospital gown, the hair on the back of your neck suddenly stands on end as you discover that your patient did not arrive unaccompanied: a tiny black bug scampers across the crisp white hospital sheet. 

Skin infestations are frequently encountered in the ED, particularly among the homeless population, though data on the number of visits are lacking. While patients with infestations may seem like pests in the middle of a busy shift, these conditions can be a public health menace, and may be markers of serious underlying pathology. 


Pediculosis, or louse infection, can result from Pediculus humanus capitus (head lice) or Pediculus humanushumanus (body lice). Like the scabies mite, lice cannot jump or fly, and are transmitted by direct contact.

Head lice, commonly encountered in school age children, survive for only several hours off the scalp and can cause pruritus, cervical lymphadenopathy, and conjunctivitis. Diagnosis is made when crawling lice are seen on or combed from the scalp. The presence of nits (shells of dead eggs) within ¼ inch of the scalp suggests active infection. Permethrin 1% (Nix) - applied for five to ten minutes, then rinsed off and repeated in a week - is commonly used for treatment in the United States. Alternatively, the patient’s head can be shaved. Lindane 1% is no longer considered first line given concerns about potential toxicity.

Body lice live in the seams of clothing, particularly the waistband, and can survive without a blood meal for up to three days. Treatment primarily focuses on personal hygiene and washing infested clothing and bed linens in hot water. Additional modalities, including oral ivermectin and permethrin-impregnated underwear, have met with limited success. 

Body lice are known carriers of Bartonella quintana, which is transmitted when lice feces are scratched into the skin by the host. B. quintana can lead to trench fever, typhus, bacillary angiomatosis, endocarditis, and chronic bacteremia. In a study of homeless patients presenting to a French ED, 14% were found to have blood cultures positive for B. quintana, and those with bacteremia were more likely to have been exposed to lice when compared to patients with negative cultures. Among 138 homeless individuals studied in San Francisco, 24% were infested with body lice, and 33% of lice collected were positive for Bartonella DNA.


Scabies is an infection with the mite Sarcoptes scabiei, an obligate parasite transmitted primarily by skin-to-skin contact. A retrospective review of dermatology consultations in a busy urban ED found that scabies was the second most common cutaneous diagnosis among non-admitted patients.  Infected individuals report intense pruritus, which usually spares the head and is often worse at night. Burrows are classically found in intertriginous spaces and flexor surfaces of the wrist, and can progress to excoriations, eczematizations, and nodules. Scabies can be diagnosed clinically, though skin scraping and biopsy are confirmatory. Overcrowding and time constraints have been associated with missed diagnosis of scabies in the ED prior to hospital admission.

Permethrin 5% (Elimite) is considered first line treatment in the US, and should be applied for eight to ten hours, with a second application one week later often recommended. Oral ivermectin has been shown to be effective, especially when followed by a second dose two weeks later . While fomite transmission of scabies is considered quite rare, washing clothes and linens in hot water or sealing them in plastic bags for two to three days is commonly advised. 

Crusted (also known as Norwegian) scabies represents a hyperinfection with hundreds to thousands of mites, which is typically limited to institutionalized elderly or immunocompromised hosts, and can lead to secondary bacterial infection, sepsis, and death.


Human bedbug infestations result from Cimex lectularius and Cimex hemipterus, blood-feeding parasites that avoid direct light and frequently hide in mattresses, bed frames, and wallpaper, while waiting to feed on human hosts at night. Anesthetic compounds in their saliva allow bites to go unnoticed, while vasodilatory factors lead to hypersensitivity reactions with pruritic macules and papules. Lesions are commonly found in unclothed areas and classically follow the “breakfast, lunch, and dinner” pattern of bites grouped in rows or clusters. Reactions are typically self-limited, and can be symptomatically treated with antihistamines or topical steroids as needed to prevent superinfection due to scratching. While multiple pathogens have been detected in bedbugs, they are not known to serve as vectors for disease.

Case Conclusion

Additional bugs are found in your patient’s waistline, and are identified as body lice. His belongings are placed in a plastic bag, and he is showered and given a new set of clothes.

Take Home Points

  • Head lice should be treated with Permethrin 1%
  • Body lice are commonly found in clothing seams (particularly the waistband) and should be treated with good hygiene and washing clothes/linens
  • Body lice may carry Bartonella quintana, which can lead to trench fever, endocarditis, and bacteremia
  • Scabies presents as intense pruritus, worse at night, in intertriginous areas and can be treated with permethrin 5%
  • Crusted scabies are found in elderly nursing home patients and the immunocompromised and can lead to sepsis and death
  • Bedbug bites cause local hypersensitivity reactions, usually at unclothed surfaces, which can be treated symptomatically and are not known to serve as disease vectors

Expert Commentary

Thank you for this excellent overview of human infestations by arthropods. While many EM providers loathe seeing the complaint of “bugs” on the tracking boards, most arthropod infestations are merely a nuisance. Treatment is largely symptomatic with antipruritics and typically topical permetherin of varying strengths depending on the suspected organism. Many providers fear becoming infested themselves, but the arthropods discussed above all require skin-to-skin contact, frequently for prolonged amounts of time, to transfer to another human. Therefore, simple protective gear such as gloves and gowns are usually sufficiency to prevent transmission from a patient to a caregiver. One exception is the flea, which can jump long distances, but is rarely found living on human beings as its preferred host is canine or feline.

The one worrisome arthropod infestation is Norwegian or crusted scabies. Due to the large number of mites, transfer can occur relatively quickly although it still requires skin-to-skin contact. It is frequently found in elderly or immunocompetent individuals, so HIV testing in these patients is certainly a consideration. The rash of Norwegian scabies is often confused with psoriasis so be mindful in patients who do not have a prior dermatologic history.

A final consideration is psychological. Patients under the influence of amphetamines or experiencing withdrawal may develop formication, the sensation of bugs crawling under the skin. These patients may scratch themselves and leave skin lesions such as excoriations that can be hard to distinguish from actual bug bites. The treatment for these patients is symptomatic. Additionally there are psychogenic causes of itching. Patients with delusional parasitosis have a fixed belief that they are infected with bugs. They will often present with evidence of the “bug” such as hairs, strings or pieces of lint they want examined by healthcare providers. It is important to build a therapeutic alliance with these patients; soliciting the help of family members may be of use. While they typically do not need emergent psychiatric evaluation (unless they are in danger of hurting themselves to eliminate the “bugs”) they may benefit from referral and possible atypical antipsychotic therapy once other physiologic causes of pruritis (such as kidney disease, hypothyroidism or liver disease) have been ruled out.

Abra Fant , MD, MS

Instructor; Department of Emergency Medicine, Northwestern University, Feinberg School of Medicine


Studdiford, J. et al. Bedbug Infestation. American Family Physician. 2012;86(7):653-658.

Delaunay, P. et al. Bedbugs and Infectious Diseases. Clinical Infectious Diseases. 2011;52(2):200-210.

Shroff, S. Update on Emerging Infections: News From the Centers for Disease Control and Prevention. Annals of Emergency Medicine. 2010;55(3):280-282.

Brouqui, P. et al. Chronic Bartonella Quintana Bacteremia in Homeless Patients. New England Journal of Medicine. 1993;340:184-9.

Tran, L. et al. Crusted (Norwegian) Scabies. Journal of Emergency Medicine. 2002;22(3):285-287.

Jack, A. et al. Cutaneous conditions Leading to Dermatology Consultations in the Emergency Department. Western Journal of Emergency Medicine. 2011;12(4):551-555.

Hong, M. et al. Factors Related to Missed Diagnosis of Incidental Scabies Infestations in Patients Admitted Through the Emergency Department to Inpatient Services. Academic Emergency Medicine. 2010;17:958-964.

Heukelbach, J. et al. Scabies. Lancet. 2006;367:1767-74.

Chosidow, O. Scabies. New England Journal of Medicine. 2006;354:1718-27.

Ko, C. et al. Pediculosis. Journal of the American Academy of Dermatology. 2004;50:1-12.

Cox, N. Permethrin treatment in scabies infestation: importance of the correct formulation. British Medical Journal. 2000;320:37-8.

Benkouiten, S. et al. Effect of Permethrin-Impregnated Underwear on Body Lice in Sheltered Homeless Persons: A Randomized Controlled Trial. JAMA Dermatology. 2014;150(3):273-279.

Posted on January 9, 2017 and filed under Infectious Disease.