Infestations and Bites

1. Infestations and Bites Medical Student Core Curriculum in Dermatology Last updated August, 2011

2. Goals and Objectives • The purpose of this module is to help medical students develop a clinical approach to the evaluation and initial management of patients presenting with bites and infestations • After completing this module, the learner will be able to: • Recognize risk factors for lice infestation and scabies • Identify nits and adult lice as diagnostic of pediculosis • Identify a burrow as the primary morphology of scabies • Identify common causes and clinical presentations of insect bite reactions, with an emphasis on bedbugs and brown recluse spider bites • Discuss treatment options and patient education for pediculosis capitis, scabies, and insect bite reactions

3. Case One Mary Thompson

4. Case One: History • HPI: Mary is a 6-year-old girl with a two week history of an itchy scalp. It has not been relieved by over-the-counter dandruff shampoo. She recently stayed over at her cousin’s house who now has the same problem. • PMH: no chronic illnesses or prior hospitalizations • Allergies: no known allergies • Medications: none • Family history: noncontributory • Social history: lives at home with parents and attends first grade • ROS: negative

5. Case One, Question 1 • What information is relevant in Mary’s history? • Recent contact with similar complaint • Scalp pruritus (itching) • School-aged child • All of the above

6. Case One, Question 1 Answer: d • What information is relevant in Mary’s history? • Recent contact with similar complaint • Scalp pruritus • School-aged child • All of the above

7. Pediculosis (Lice): The Basics • Three different varieties of lice may infest humans • Head louse – Pediculus humanus var. capitis • Body louse – Pediculus humanus var. corporis • Pubic or crab louse – Phthirus pubis • Head lice are spread by close physical contact and may be transferred by use of head gear, combs, brushes, and pillows • Commonly affects school-age children

8. Pediculosis Capitis: The Basics • Affects all ethnic and socioeconomic groups, but is less common in African-Americans. • Frequently has associated scalp pruritus and may also have posterior cervical lymphadenopathy. • Live adult lice and nits (ova or eggs) may be noted on examination. • Most common sites to find nits are the retroauricular and occipital scalp. • Nits within 0.6 cm of the scalp are typically viable. In warm environments the distance may be greater. • Nits must be distinguished from hair casts. Hair casts encircle the hair shaft and move freely in contrast to the nit which is cemented to the hair.

9. Back to Case One

10. Skin Exam Findings Exam of occipital scalp: Structures on the hair are not freely movable

11. Case One, Question 2 • How would you describe Mary’s exam? • Multiple hair casts present in the occipital scalp. No nits or lice noted. • Multiple nits present in the occipital scalp. No lice noted. • Negative exam, no nits or lice noted.

12. Case One, Question 2 Answer: b • How would you describe Mary’s exam? • Multiple hair casts present in the occipital scalp. No nits or lice noted. • Multiple nits present in the occipital scalp. No lice noted. • Negative exam, no nits or lice noted.

13. Skin Exam Findings Exam of occipital scalp: numerous nits

14. Pediculosis: Pathogenesis • Female adult lice live 30 days and lay 5-10 eggs (nits) per day at the base of the hair where it meets the scalp. • Eggs hatch in 8-12 days. • Lice typically survive 1-2 days away from the scalp. Eggs may survive up to 10 days away from the scalp. • Live eggs remain close to the scalp to maintain warmth and moisture but as the hair grows, the nits move off the scalp with the hair. • Because hair grows at a rate of ~ 1cm per month, the duration of infestation can be estimated by the distance of the nit from the scalp.

15. Pediculosis: Pathogenesis • The adult louse at the right typically is 2-3 mm in length. • The presence of live adult lice, immature nymphs, and/or viable eggs indicates active infection.

16. Back to Case One

17. Follow-up • Mary returns to clinic in four weeks for follow-up. Therapy was completed as directed but she still has nits present on exam which are approximately one inch from the scalp. A sample is on the slide that follows.

18. Hair Mount This image shows a nit without an intact cap (operculum) and is not viable (no larva inside). Continued presence of nits does not always represent treatment failure.

19. Pediculosis: Treatment • Physical removal of nits may be facilitated by using a fine-toothed comb (or nit picker) on wet, well-conditioned hair. • Occlusive methods have also been used to suffocate head lice using substances such as petroleum jelly and mayonnaise, but study results have been variable. • Over-the-counter and prescription topical therapies are listed on the following slide.

20. Pediculosis: Treatment

21. Pediculosis: Treatment • Individual patient risks should be assessed prior to choosing a topical therapy (age, allergy history, prior treatment, etc.). • It is prudent to retreat with topical therapies one week after initial therapy to kill the newly hatched lice. • Patients with refractory lice should be referred to a dermatologist.

22. Back to Case One

23. Case One, Question 3 • If Mary had live lice in the scalp on follow-up, what would be possible causes of treatment failure? • Not treating contacts (reinfestation) • Not properly cleaning the environment • Not retreating in 7-10 days • Incorrect application of the medication • Resistance of the organism to medication • All of the above

24. Case One, Question 3 Answer: f • If Mary had live lice in the scalp on follow-up, what would be possible causes of treatment failure? • Not treating contacts (reinfestation) • Not properly cleaning the environment • Not retreating in 7-10 days • Incorrect application of the medication • Resistance of the organism to medication • All of the above

25. Pediculosis: Patient Education • All persons living in the home should be examined to avoid reinfestation. • If it is not possible to examine household members, treat without an exam if the treatment is not contraindicated. • Clothing and bedding should be washed and dried on the hot cycle. • Non-washable items may be placed in the dryer or stored in a sealed plastic bag for two weeks.

26. Pediculosis: Patient Education • Combs and brushes should also be washed in hot water and may be treated with a pediculocide. • Floors, furniture, and vehicles should be vacuumed to remove hair with potentially viable nits attached.

27. Michael Miller Case Two

28. Case Two: History • HPI: Mike is a 21-month-old boy who was referred to the dermatology clinic for a rash that has been present for two weeks. He has been having problems sleeping due to itching. • PMH: no history of major illness or hospitalizations • Allergies: no known drug allergies • Medications: none • Family history: noncontributory • Social history: lives in the city and attends day care • ROS: pruritus

29. Case Two: Skin Exam • Multiple erythematous papules throughout the trunk, extremities. Also involving the scrotum. • Burrows present in the 2nd-3rd web space on the right hand.

30. Case Two, Question 1 • What in-office procedure would best help to confirm the diagnosis? • KOH preparation • Nail clipping • Skin scraping (mineral oil prep) • Wood’s light examination

31. Case Two, Question 1 Answer: c • What in-office procedure would best help to confirm the diagnosis? • KOH preparation • Nail clipping • Skin scraping (mineral oil prep) • Wood’s lamp examination

32. Case Two, Question 2 • You perform a skin scraping on the patient and see the image on the following slide when you look through the microscope. What is present on the slide? • Eggs • Scabies mite • Scybala (scabies feces) • All of the above

33. Case Two, Question 2

34. Case Two, Question 2 Answer: d • You perform a skin scraping on the patient and see the image on the following slide when you look through the microscope. What is present on the slide? • Eggs • Scabies mite • Scybala (scabies feces) • All of the above

35. Case Two, Question 2 mite scybala (feces) egg

36. Scabies: The Basics • Sarcoptes scabiei (scabies) affects patients of all ages and all socioeconomic classes, although more common in women and children. • Patients incongregated facilities are more prone to the infestation, such as nursing homes. • Most infections occur from direct contact with an infected individual. However, fomites can transmit the infection. • Females lay about three eggs per day, which hatch in four days. Most patients have less than 20 mites on the skin at a time.

37. Scabies: The Basics • The time from initial infestation to symptoms is 3-4 weeks because the rash is caused by hypersensitivity to the mites. • Papules may commonly involve the breasts, umbilicus, penis, scrotum, finger webs, wrists, and axilla. • The scalp and head are more frequently involved in infants, elderly, and immunosuppressed.

38. Case Two, Question 3 • Which of the following clinical findings are considered pathognomonic for scabies? • Burrows • Diffuse involvement • Erythematous papules • Sparing of the groin

39. Case Two, Question 3 Answer: a • Which of the following clinical findings are considered pathognomonic for scabies? • Burrows • Diffuse involvement • Erythematous papules • Sparing of the groin

40. Scabies • Burrows are linear markings in the skin due to the movement of the mite. They are 1-10 mm in length and may be found most readily in the interdigital spaces, wrists, and elbows.

41. Back to Case Two

42. Case Two, Question 4 • Mike’s mother tells you his uncle has AIDS and is currently hospitalized. Why is this important? • His uncle may have been the source of infection • If his uncle has scabies, it could cause an institutional outbreak • If his uncle gets scabies, it may be a more severe form • All of the above

43. Case Two, Question 4 Answer: d • Mike’s mother tells you his uncle has AIDS and is currently hospitalized. Why is this important? • His uncle may have been the source of infection (Immunosuppressed patients are at increased risk for infection) • If his uncle has scabies, it could cause an institutional outbreak (Patients with crusted scabies harbor more mites) • If his uncle gets scabies, it may be a more severe form (Immunosuppressed patients may develop crusted scabies) • All of the above

44. Crusted Scabies Refer to the HIV Dermatology module for more information on crusted scabies

45. Scabies: Treatment • As in pediculosis, scabies treatment includes a two-pronged approach. The patient and the environment must both be treated. • Environmental care includes washing all clothing and linens in hot water, sealing items which may not be washed in bags for two weeks, and vacuuming.

46. Scabies: Treatment For difficult to treat or severe scabies, refer to a dermatologist

47. Mrs. Marsha Koehler Case Three

48. Case Three: History • HPI: Mrs. Koehler is a 33-year-old woman who presented to clinic with “itchy bumps” which started over the weekend. No one else at home has a similar complaint. • PMH: GERD • Allergies: none • Medications: Omeprazole • Family history: not contributory • Social history: works in a diner as a waitress • ROS: negative

49. Case Three: Skin Exam Edematous papules scattered over the body. Some with signs of excoriation.

50. Case Three, Question 1 • What is the most likely diagnosis? • Bedbug bites • Brown recluse spider bite • Chickenpox • Methicillin-resistant S. aureusfolliculitis • Pediculosiscorporis