Introduction to Parasitology and Arthropods

Question 1

Definitive host

Answer 1

Where adult or sexually reproductive stages live

Question 2

Intermediate host

Answer 2

Where the larval stages live

Question 3

Vector

Answer 3

Organisms that transmit disease from host to host

Question 4

Reservoir host

Answer 4

Animals that maintain a human infection

Question 5

Insect characteristics

Answer 5

3 pairs of legs, head, thorax abdomen, various types of mouthparts, may have wings

Question 6

Where multiplication of infectious agent usually occurs

Answer 6

Within the vector

Question 7

phthirus pubis

Answer 7

crab louse, large claws on back 2 legs

Question 8

Pediculus humanus capitis

Answer 8

Hair louse, intense pruritis depending on number and host sensitivity

Question 9

Lice treatment

Answer 9

1. Medicated shampoo plus nit picking
2. Repeat one week later
3. Treatment of clothing and furniture with heat/insecticides/seal off for 2 weeks
4. Treat family (highly contagious)

Question 10

Disease transmission of lice

Answer 10

Body louse only - epidemic typhus, trench fever and relapsing fever

Question 11

Pediciculus humanus humanus

Answer 11

nit on clothing

Question 12

Cimex lectularius characteristics

Answer 12

Bed bug

No wings, covered with hairs. Night feeders. Can live a year without feeding. No disease transmission.

Question 13

Triatomid characteristics

Answer 13

Assassin bug or kissing bug, have wings, bite on face, lips and outer angle of eye. Transmit trypanosoma cruzi (chagas)

Question 14

Myiasis

Answer 14

Fly larval infection due to invasion, treat with petroleum jelly to get fly larvae to exit, or surgical intervention

Question 15

Mosquito transmission of disease?

Answer 15

Via the females only, feed on blood and transmit malaria, filarial worms, yellow fever, dengue, viral encephalitis.

Question 16

Tick and mite characteristics

Answer 16

No external segmentation, four pairs of legs, mites are smaller and have no teeth on hypostome

Question 17

Hard tick characteristics and vector for?

Answer 17

Dorsal scutum, not host-specific. Long feeding period. Can cause tick paralysis especially if bite is along spinal column. Vector for Rocky Mountain Spotted Fever, babesiosis, Lyme, ehrlichia, tularemia.

Question 18

Soft tick characteristics

Answer 18

No scutum, bite is short duration, transmit endemic relapsing fever

Question 19

Sarcoptes scabiei

Answer 19

Mite, seen beneath breasts, belly folds of babies and interdigital webs. Adults lay eggs in tunnels, hatched larvae migrate to surface of skin. Severe dermatitis. Disease: scabies or mange.
Secondary bacterial infection is a problem.

Question 20

Demodex folliculorum

Answer 20

50-100 percent of adults infected. Found in hair follicles, sebaceous glands of face. Rarely requires treatment.

Question 21

House dust mites

Answer 21

Feed on organic debris, cause allergic responses including asthma.

Question 22

Centipedes vs Millipedes

Answer 22

Centipedes cause painful wound from venomous claws, one appendage/segment.
Millipedes have no claws and have two appendages/segment.

Question 23

Scorpions

Answer 23

Found in arid regions including SW US. Neurotoxic and hemotoxic venom. 8 legs. Specific anti-venom available.

Question 24

Black widow spider

Answer 24

Latrodectus mactans. Red hour glass on ventral aspect of abdomen. Neurotoxic venom. Pain and swelling, severe burning and aching sensation, leads to cramps with board-like rigidity of abdomen.

Question 25

brown recluse/fiddleback spider

Answer 25

Loxosceles reclusa. Violin-shaped area on dorsum, necrotoxic venom. Central necrosis as skin becomes covered with vesicles and sloughs off. Healing is slow, disfiguring.