Roundworms And Medically Important Arthropods

Question 1

What are the characteristics of roundworms?

Answer 1

Male and female sexes
Complete GI tract (mouth and anus)
Diseases caused:
Perianal pruritus
Inflammatory reaction
Pneumonitis
Anemia
Damage due to movement

Question 2

What are the characteristics of Enterobius vermicularis?

Answer 2

Also called pinworms
Worlwide distribution
Most common helminthic infection in the USA
Humans are the only host
Ingestion, inhalation of eggs( fecal-oral)
Female lay eggs in perianal area at night
Autoinfection due to larvae crawling back in
Causes enterobiasis

Question 3

What are the characteristics of enterobiasis?

Answer 3

Perianal itch
Perianal pruritus
Genitourinary granulomas
Associated with Dientamoeba fragilis infections 
ID: scotch tape mount for pinworm eggs

Question 4

What are the characteristics of Ascaris lumbricoides?

Answer 4

The most common helminthic infection worldwide
Pathway: intestine-blood- lung- intestine
Most common cause of parasitic infection of bile duct
ID: Knobby eggs in feces
Eggs or adults in feces
Larvae in sputum

Question 5

What are the diseases caused by Ascaris lumbricoides?

Answer 5

Asymptomatic
Pneumonitis
Loeffler syndrome
Perforation of intestine and other organs
Intestinal blockage
Distension of small and large bowel with air fluid levels
may enter bile uct ansd cause biliary colic,gallstone formation,liver abscess

Question 6

What are the characrteristics of Toxocara canis, Toxocara cati, Baylisascaris procyonis?

Answer 6

Ascarids of dogs, cats and raccoons respectively
T. Canis and T. Cati have visceral and ocular larva migrans
B. Procyonis have neural larva migrans
ID: clinical picture, eosinophilia, ELISA/serology

Question 7

What are the charactreristics of Trichuris trichiura?

Answer 7

Also called Whipworm
Humans are the only host 
Diseases caused :
Asymptomatic
Bloody diarrhea
Appendicitis
Rectal prolapse 
ID: barrel shaped eggs

Question 8

What are the characteristics of Trichinella spiralis?

Answer 8

Infection from ingestion of cysts in undercooked pork, walrus and bear
Larvae migrate to striated muscle
larvae live years, eventually cysts calcify
Cause trichinosis, trichinellosis-

Question 9

What are the characteristics of trichinellosis?

Answer 9

Asymptomatic to lethal depending on worm burden
Deadly triad: myocarditis, encephalitis, pneumonitis
death within 4-6 weeks
ID: Splinter hemorrhages, microscopy of meat, serological tests

Question 10

What are the characteristics of Necator americanus and Ancylostoma duodenale?

Answer 10

Respectively called New World and Old World hookworms
Infection by penetration of skin by filariform larvae
Adults attach to intestinal wall with chitinous plates (N. Americanus), and teeth (A. Duodenale)

Question 11

What are the diseases caused by N. americanus and A.duodenale?

Answer 11

Pruritus at skin site
Diarrhea
Pneumonitis
Microcytic anemia
Emaciation
Physical and mental retardation from nutritional deficiency
ID: eggs in feces

Question 12

What are the characteristics of Ancylostoma braziliense?

Answer 12

Dog and cat hookworm
Fecal contaminated beaches (SE USA)
Cutaneous larva migrans- pruritus, «serpiginous or creeping eruption» lesions of 3 weeks duration
Humans are dead end hosts

Question 13

What are the characteristics of Strongyloides stercoralis?

Answer 13

Threadworm similar to hookworm
Domestic pets are reservoirs
Filarifrom larvae penetrate skin 
Pathway: Skin-blood-lung-intestine
Autoinfection possible 
In the intestine female can reproduce by parthogenesis

Question 14

What are the diseases caused by Strongyloides stercoralis?

Answer 14

Ground itch/creeping eruption
Pneumonitis
Asymptomatic to peptic ulcer like disease
Chronic infections can last years
86% fatality in IC patients with disseminated disease (hyperinfection)
ID: Baermann funnel gauze method to concentrate larvae from feces
Larvae in fecal smears, eggs are rare

Question 15

What are the filarid parasites?

Answer 15

Wuchereria bancrofti and Brugia malaya
Loa loa
Onchocerca volvulus
All found in tropical and subtropical regions
ID: eosinophilia, microfilaria in Giemsa stained blood smears or tissue preps

Question 16

What are the Characteristics of Wuchereria bancrofti?

Answer 16

The mosquitoes are vectors
causes elephantiasis which is due to clogging of the lymphatic vessels by microfilaria
Occur 9-12 months post bite

Question 17

What are the characteristic of loiasis?

Answer 17

Occurs in Central Africa
Introduced by a bite of the mango fly, deer fly or horsefly
Worms mature and migrate for as much as 17 years
Causes Loiasis of eye
Calabar skin swellings: transient large nodular, painful, pruritic swellings in the extremities caused by worm migration

Question 18

What are the characteristics of Onchocerca volvulus?

Answer 18

The female blackfly is the vector
Causes river blindness
Acute and chronic inflammation involving many tissues but most notably the eyes, hyperpigmented skin

Question 19

What are the characteristics of Latrodectism mactans?

Answer 19

Caused Latrodectus mactans or black widow bite
Painful bite
Symptoms appear 40 minutes after a bite
Pain and abdominal stiffness
Erythema or pain at the site of the bite, thoracic pain
Pain in extremities and contractures
Psychomotor alterations
Relief within 24 hours
DX: difficult without clear history of spider bite

Question 20

What are the characteristics of Loxoscelism?

Answer 20

Caused by bite by Loxosceles reclusa or brown recluse spider
Less painful bite compare to black widow bite
Mild local urticarial (hive like) reactions to full thickness skin necrosis in 3-4 days
Location: hands, arms and lower extremities
Other symptoms: fever headache, malaise. Joint aches, nausea and vomiting
Widely distributed in the southeast USA and Midwest in outdoors and basements

Question 21

What are the toxins in scorpions?

Answer 21

Neurotoxin
Hemorrhagic/hemolytic toxin-pain swelling, necrosis
Death can result from pulmonary edema or respiratory paralysis
Horse antivenin available
Possibility of serum sickness

Question 22

What are the characteristics of Sarcoptes scabiei?

Answer 22

Causes by scabies, mange, itch mite
Also an STD
Transmitted through close contact and fomites
ID: ova and mites present in skin scrapings treated with 20% KOH
For confirmation must find Scybala: barrel shaped brown fecal pellet on a skin scraping of a burrow

Question 23

What are the chracteristics of Trombiculiasis?

Answer 23

Caused by Trombicula irritans, Eutrombicula or Chigger bites
Chiggers bite and suck fluids
Larvae mites have 3 pairs of legs and adults have 4

Question 24

What are the characteristics of Myiasis causing flies?

Answer 24

Caused maggots in nasal,intestinal,urinary or dermal tissue
Larvae develop over 40-50 days causes warble lesion
Secondary infections, abscesses when larvae die

Question 25

What are the characteristics of pediculosis,Phthiriasis?

Answer 25

Caused by Pediculus,Phthrius- lice
have 3 types:
Pediculus humanus capitis predominantly on the scalp may involve other facial hair and mainly in children
Pediculus humanus corporis- body
Phthrius pubis-pubic crabs

Question 26

What are the characteristics of Pulex, Ctenocephalides?

Answer 26

Fleas dont normally reside on humans
Close contact with animals
Siphonaptera
Vector for D.caninum, plague and murine typhus

Question 27

What are the characteristics of Cimex?

Answer 27

Bed bugs due to crowded, poor hygiene
Bugs, eggs, fecal droppings in bedding 
Bites occur at night
Erythematous bites
Locations: face, neck, hands or arms