1. 1 Ectoparasite Faculty: Samuel Aguazim, M.D. Lange Chapter 69Lange Chapter 69

2. MINOR PARASITE 2

3. Anisakiasis simplex The larvae of A. simplex cause anisakiasis. They are ingested in raw seafood, such as sashimi and sushi, and migrate into the submucosa of the intestinal tract. Acute infection resembles appendicitis. Diagnosis is not dependent on the clinical laboratory. There is no effective drug therapy. Prevention consists of not eating raw fish 3

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5. In this patient the Anisakiasis worm has invaded the gastrointestinal tract. 5

6. ECTOPARASITE 6

7. Introduction What is an ectoparasite? Why is the control of ectoparasites so important? Does anyone have any previous experience of ectoparasites?

8. What are ectoparasites? Ecto means outside. Parasites are organisms that live on other animals. Ectoparasites are therefore parasites that live on the skin or hair of other animals. Ectoparasites

9. Pediculus humanus & Phthirus pubis Disease Pediculosis. Characteristics Lice are easily visible. P. humanus has an elongated body, whereas P. pubis has a short body resembling a crab. Nits are the eggs of the louse, often attached to the hair shaft or clothing. 9

10. Vector Biology Three types of lice: Head lice: Pediculus humanus capitis (2-3 mm long) Body lice: Pediculus humanus humanus (2.3-3.6 mm long) Pubic lice (crabs): Phthirus pubis (1.1-1.8 mm long)

11. Vector Biology All three types of lice: Are ectoparasites: lice live on the surface of the host Move by crawling, as opposed to flying Have humans as their only host Have similar life cycles Head LiceBody LicePubic Lice

12. Lice Life Cycle Lice stages: 1.Egg/nit 2.Nymph (3 molts) 3.Adult Both nymphs and adults take blood meals from the human host.

13. History of Lice & Humans DNA evidence suggests that human lice split off from gorilla lice approximately 3-4 million years ago

14. Lice in the News Outbreaks do show up in national news! Not severe: most of the stories related to school and campus outbreaks “Head Lice Epidemic Closes Anderson Schools” 1973 “Lice Outbreak Cancels Classes” 1980

15. Symptoms Head Lice Itching Difficulty sleeping Sores and secondary bacterial infections from scratching

16. Symptoms (Continued) Body lice: Intense itching –Skin discoloration/thickening –Secondary bacterial infection also possible from prolonged scratching –Red rash Pubic lice “crabs”: Itching

17. Disease Head lice: does not spread disease Body lice spreads bacterial disease! Pubic lice: does not spread disease

18. Diagnosis by Direct Visualization Observation of live nymphs or adult lice. Finding nits is suggestive of infection but not definitive. Use fine-tooth comb and magnifying glass. NITS

19. Epidemiology & Risk Factors Head lice: “head-to-head” transmission 6-12 million cases/yr in the United States in children age 3-11 Found worldwide Girls at higher risk than boys African Americans lower risk than other racial groups

20. Epidemiology & Risk Factors (Continued) Pubic Lice (“Crabs”): Current worldwide prevalence estimated 2% Spread through sexual contact and is considered an STD Can be spread through fomites: contact with clothing, linens, and towels belonging to an infected person. Pubic lice found on children can be an indicator of sexual abuse.

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22. Transmission :Hair and body lice are transmitted from human to human by contact, especially fomites such as hats and combs. Pubic lice are transmitted by sexual contact. Pathogenesis: Itching is caused by a hypersensitivity response to saliva of the louse. Excoriations may result from scratching and secondary bacterial infections may occur Laboratory Diagnosis :Not involved. Treatment : Permethrin. Prevention : Personal items should be treated or discarded. 22

23. Dermatobia hominis Disease: Myiasis. Characteristics: Fly larvae (maggots) cause the disease not the adult flies. Transmission :Adult fly deposits egg in lesion. Egg hatches to form larva. Dermatobia deposits its egg on mosquito, and when the mosquito bites the eggs are then deposited on the skin. Pathogenesis: Larva induces an inflammatory response. Laboratory Diagnosis :Not involved. Treatment :Surgical removal of larva. Prevention :Limit exposure to flies and mosquitoes. 23

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26. Bedbugs: Cimex lectularius is the most common bedbug found in the United States. It has an oval, brownish body and is about 5 mm long. Bedbugs reside in mattresses and in the crevices of wooden beds. At night, they emerge to take a blood meal from sleeping humans. The main symptom is a pruritic wheal caused by a hypersensitivity reaction to proteins in the bug saliva. Some individuals show little reaction. The bite of a bedbug is not known to transmit any human disease. Calomine lotion can be used to relieve the itching. Malathion or lindane can be used to treat mattresses and beds. 26

27. Maculopapular lesions from bedbugs that follow the linear pattern, often referred to as "breakfast, lunch, and dinner 27

28. Sarcoptes scabiei Disease: Scabies. Characteristics Round body with eight short legs. Too small to be seen with naked eye. Transmission Person-to-person contact or fomites such as clothing. Pathogenesis: Itching is caused by a hypersensitivity response to feces of the mite. Laboratory Diagnosis: Microscopic examination reveals mites and their feces. Treatment: Permethrin. Prevention: Treat contacts and discard fomites. 28

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30. Scabies infection involving the hand 30

31. Serpiginous lesion from scabies. 31

32. Dermacentor Species Disease: Tick paralysis. Characteristics: Certain species of ticks produce a neurotoxin. Transmission: Ticks reside in grassy areas and attach to human skin. Pathogenesis: Female tick requires a blood meal and toxin enters in tick saliva at bite site. Neurotoxin blocks release of acetyl choline at neuromuscular junction. Similar action as botulinum toxin. Laboratory Diagnosis: Not involved. Treatment: Removal of tick results in prompt reversal of paralysis. Prevention: Remove ticks; wear protective clothing. 32

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34. Latrodectus mactans (Black Widow Spider) Disease: Spider bite. Characteristics Black widow spiders have an orange-red hourglass on their ventral surface. Pathogenesis: Neurotoxin causes pain in extremities and abdomen. Numbness, fever, and vomiting also occur. Laboratory Diagnosis: Not involved. Treatment: Antivenom should be given in severe cases. 34

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36. Loxosceles reclusa (Brown Recluse Spider) Disease: Spider bite. Characteristics Brown recluse spiders have a violin-shaped pattern on their dorsal surface. Pathogenesis Dermotoxin is a protease that causes painful necrotic lesions Laboratory Diagnosis Not involved. Treatment Antivenom is not available in the United States. 36

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