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Microbiology > Exam #8: Parasitic/ Arthropod Skin, Soft Tissue, & Muscle Infections > Flashcards

Exam #8: Parasitic/ Arthropod Skin, Soft Tissue, & Muscle Infections Flashcards

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Biology 101 flashcards
1
Q

What is Leshmaniasis?

A

Protozoa that is transmitted by the bite of an infected female sand fly
- Canines & rodents are important reservoirs

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2
Q

Describe the lifecycle of Leishmaniasis.

A
  • Infected female sand flies deliver extracellular flagellated promastigote forms of the parasite
  • Parasite is rapidly phagocytosed by macrophages & monocytes
  • In macrophages & monocytes, Leshmania differentiate into non-motile amastigote forms
  • Amastigote form replicates & persists in the host
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3
Q

What are the three major Leishmaniasis-associated diseases in man, what specific species cause them?

A

1) Cutaneous leishmaniasis= L. major, tropica, & mexicana
2) Mucocutaneous leishmaniasis= L. braziliensis
3) Visceral leishmaniasis= L. donovani, infantum, and chagasi

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4
Q

What are the symptoms of cutaneous Leishmaniasis?

A
  • Raised , dry, crusty lesion at site where parasites were inoculated.
  • Lesion slowly enlarges and then ulcerates.
  • Self limiting infection.
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5
Q

What are the symptoms of mucocutaneous Leishmaniasis? How is it treated?

A
  • Infection initially presents as a typical cutaneous lesion.
  • Months to years after resolution of the initial infection, ulcerative lesions develop, typically in the nasal mucosa and septum

*Note that within infected individuals, only intracellular (found EXCLUSIVELY in mononuclear phagocytes) forms are found; thus, antibodies offer little or no protection. Cell-mediated immunity is important. Treatment is with heavy metal compounds that are considerably toxic.

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6
Q

What is Onchocerciasis?

A

River Blindness

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7
Q

What causes Onchocerciasis?

A

Onchocerca volvulus, which is a filarial nematode

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8
Q

Describe the lifecycle of Onchocerca volvulus.

A
  • Infected black fly bites human
  • Microfilariae are introduced via the open wound & mate
  • Adult worms exist knotted together in subcutaneous nodules
  • Microfilariae escape from the nodules & migrate through subuctaneous tissue
  • The inflammatory reaction to these migrating microfilariae leads to an intense pruritic rash
  • In the eye, this leads to sclerosing keratitis resulting in a hardening inflammation of the cornea and blindeness

*Note that transmission is through INFECTED BLACK FLIES

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9
Q

What is Onchocerciasis most endemic?

A

1) Africa

2) Central & South America

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10
Q

What are the symptoms of Onchocerciasis?

A
  • Intense pruritic rash (itching) from immune response to microfilariae
  • Blindness may take years to develop & occurs in 5-10% of infected individuals

*Note that the itching accompanied by this rash is so bad that suicide is NOT uncommon

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11
Q

How is Onchocerciasis diagnosed?

A

Visualizing microfilariae from skin snips

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12
Q

How is Onchocerciasis treated?

A

Ivermectin, which appears to interfere with the release of microfilariae

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13
Q

What is Filariasis? What causes Filariasis?

A

Filariasis is caused by Mansonella sp., a filarial nematode

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14
Q

Where is mansonella endemic?

A

M. streptocerca- Central Africa
M. perstans- Africa, Caribbean, South America
M. ozzardi- Central & South America + Caribbean

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15
Q

What is the lifecycle of mansonella?

A

Microfilaria are transmitted by the bite of infected midges

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16
Q

What are the symptoms of mansonella infection?

A
  • Cutaneous itching

- Joint pain

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17
Q

What is Dracunculiasis?

A
  • A nematode infestation of the skin that is endemic to Africa
  • The causative organism is Dracunculus medinensis, which is a tissue dwelling nematode that grows to be 50-100cm in length
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18
Q

Describe the lifecycle of Dracunculus medinesis.

A
  • Larvae are released from ingested copepods in the small intestine
  • Larvae penetrate the intestinal & abdominal wall, entering the connective & subcutaneous tissue
  • Larvae develop into adults
  • Gravid females migrate to the extremities & trunk
  • It is the presence of these gravid females that leads to the development of indurated papules the eventually ulcerate
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19
Q

How do humans acquire Dracunculus medinesis?

A
  • Swallowing microscopic freshwater copepods (crustaceans) that are infected with larval forms of the worm
  • I.e. contaminated drinking water
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20
Q

How has Dracunculosis been prevented?

A

Preventing water contamination

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21
Q

What is the treatment for Dracunculosis?

A

Wind the worm out on a stick

*Note that it is important NOT to break to he worm during removal; severe anaphylactic reactions have been reported in response to disintegrating adult worms

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22
Q

What is cutaneous larva migrans?

A

Hookworms of dogs and cats infecting humans

23
Q

How is cutaneous larva migrans transmitted?

A
  • Penetration skin of humans
  • Fail to get into circulation; rather, migrate in subcutaneous tissue and die, causing an inflammatory reaction

*Happens in the caribbean with wild dogs and cats

24
Q

What are the symptoms of cutaneous larva migrans?

A

Erythematous, pruritic lesions usually on the feet & legs

“Creeping eruption” is pathognomonic for cutaneous larval migrans

25
Q

What is Scabies?

A

The most common superficial dermatitis seen in the US, caused by “Sarcoptes scabiei”

26
Q

Describe the lifecycle of Scabies.

A
  • Infection begins when a female mites is transferred from an infected individual via direct contact
  • Mite burrows into the skin, laying eggs all the while
  • Larvae hatch, leave the burrow, & establish new burrows
  • Males & females mate & produce more eggs
27
Q

Where are Scabies mites most commonly found?

A

Webbing & sides of fingers, later spreading to the wrists, elbows, and the trunk

28
Q

What are the symptoms of Scabies?

A
  • Itching in the webbing & sides of fingers, later spreading to the wrists, elbows, and the trunk
  • Lesions appear as short, serpentine, slightly raised cutaneous tracts

*Note that typical infection only involve s 1/2-12 female mites

29
Q

What is Norwegian or crusted Scabies?

A

Scabies hyperinfection that presents as crusted scabies; this is caused by infestation with thousands of mites

30
Q

How is Scabies diagnosed?

A
  • Direct visualization of mites
  • Microscopic evaluation of skin scrapings

*Mites or eggs confirms diagnosis

31
Q

How is Scabies treated?

A
  • Topical formula
  • Recommended that all members of a household are treated
  • Aggressive cleaning of clothing & linens
32
Q

Describe the characeristics of lice.

A

Lice or “Pediculosis” is an obligate blood-feeding ectoparasites

  • Wingless
  • Six-legged
  • Flattened insects
33
Q

What are the three species of lice that infect humans?

A

Body louse= Pediculus humans
Head louse= P. humanus capitis
Crab louse= Phthirus pubis

*Note that the crab louse has 2nd & 3rd sets of legs that are clawed, resembling crabs

34
Q

What is the presentation of lice?

A

The usual characteristics of all infestation types is intense itching with pruritic reddened papules

35
Q

What two species of lice are “sedentary?”

A

Head
Crab

*Thus, the body louse is mobile; it remains on clothing and moves from clothes to body for a meal–then goes back to the clothing

36
Q

Describe the lifecycle of lice.

A
  • Female lice lay eggs (nits) that attach to hair shafts
  • Eggs hatch

*The body louse is different; it resides in clothing & is mobile. Eggs around found in the seams of infested garments

37
Q

How is lice diagnosed?

A

Identification of lice or eggs in hair or in seams of clothing

38
Q

What are nits?

A

Louse eggs that attach to hair

39
Q

How is lice treated?

A

Low dose insecticides in dusts, shampoos, lotions, and creams

  • Aggressive washing of bedding and clothing (hot water)
  • Nit combs
40
Q

What is Myiasis?

A

Myiasis is the term used to describe the infestation of tissue by the larvae i.e. maggots of flies

41
Q

Describe the lifecycle of the Human Botfly.

A
  • Adult flies capture blood sucking athropods, lay their fly eggs on the abdomens of the arthropod, and then release the arthropod
  • When the arthropod with fly eggs lands on the mammal, eggs hatch, releasing larvae onto the skin & into the wound created by the bite
  • Eggs grow into maggots
42
Q

What species of Botfly infects humans?

A

Dermatobia hominis

43
Q

What is Trichinosis?

A

Trichinosis or Trichinellosis is a nematode infection caused by the ingestion of infected meat, mainly pork

  • Larvae from infected females encysts in muscle causing tissue specific symptoms
  • GI symptoms include diarrhea, abdominal pain, and vomiting
44
Q

What organism causes Trichinosis?

A

Trichinella spiralis, a nematode associated with eating under prepared meat (esp. pork)

45
Q

Describe the lifecycle & transmission of Trichinella spiralis.

A
  • Infection begins following the ingestion of infected meat (pork)
  • Within the small intestine, larvae excyst and develop into adults
  • Fertilized females release infectious larvae that penetrate the mucosa, enter the bloodstream, and encyst with muscles
46
Q

What is a nurse cell?

A

Encysted larvae in muscle cells

47
Q

How is Trichinosis diagnosed?

A
  • Eosinophilia
  • Elevated muscle enzymes
  • Antibody testing
  • Observation of encysted larvae in muscle biopsy= definitive diagnosis
48
Q

What is Loiasis?

A
  • Colloquially, the “eye worm”
  • Filarial nematode infestation seen in Africa that can be found in subcutaneous tissues & peripheral blood
  • Has a tendency to travel to the eye
49
Q

What causes Loiasis?

A

Loa Loa

50
Q

How is Loa Loa transmitted?

A

Bite of infected Mango flies

51
Q

What are the symptoms of Loiasis?

A

Calabar swellings= inflammatory response to subcutaneous adults that is characterized by 10-20cm non-erythematous angioedematous swellings that last for a few days

*Note that findings worms in the conjunctiva is common; these must be surgically removed

52
Q

What is Paragonimus westermani?

A

Lung Fluke

53
Q

Where is the Lung Fluke endemic?

A

Asia & South America

54
Q

Describe the presentation of the Lung Fluke.

A
  • Masquerades as TB
  • Patient presents with “Rust colored sputum”

*Note that “rust colored” sputum is also associated with S. pneumoniae–>pneumonia

Microbiology (49 decks)

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