Helminthic Infection

Question 1

Eosinophils

Answer 1

Contain basic proteins toxic to some helminths and are a major component of inflammatory responses

Question 2

Lymphatic Filarisasis

Answer 2

Filarial
Massive lymphedema (elephatiasis)
Inflammatory parasitic infection of lymphatic vessels caused by round worms
Wuchereria bancrofti Brugia malayi
**Humans are the only definitive hosts
Inhabit lymphatics leading to obstruction of flow
Granulomatous rxn may occur & degenerating worms can provoke acute inflammation

Question 3

Onchocerciasis “River Blindness”

Answer 3

Filarial
Causes blindness, transmitted from Blackflies
*Humans are the only definitive host
Chronic inflammatory disease of skin, eyes and lymphatics
Onchocerca volvulus
Microfilariae die and incite a vigorous inflammatory and immune response
Skin manifestations begin w/ generalized pruritis, continuing damage produces areas of depigmentation, hypertrophy and atrophy of the skin

Question 4

Loiasis

Answer 4

Filarial
Affects the skin and eyes
Loa loa- “eye worm” - transmitted by mango flies
Migrate in the skin and cross the eye beneath the conjunctiva
Migrating worms cause no inflammatory rxns
Most infections are asymptomatic, can persist for years
Dead worms in or near major nerves can cause paresthesia or paralysis

Question 5

Ascariasis

Answer 5

Asymptomatic Infestation of the Small Bowel
Ascaris lumbricoides
**Most common helminthic infection of humans
larvae eggs emerge in the small intestine, penetrate the bowel wall adn reach the lungs through the venous circulation
Adult worms which live in the small intestine cause no pathologic changes
Ascaris pneumonia, which may be fatal, develops when large numbers of larvae migrate within the air spaces

Question 6

Trichuriasis

Answer 6

Superficially invasive infection of colon
Trichuris trichura “whipworm”
Adult worms live in the cecum & upper colon, this invasion causes small erosions, focal active inflammation and continuous loss of small quantities of blood
Most Infections are asymptomatic

Question 7

Hookworms
A. duodenale
N. americanus

Answer 7

Intestinal Blood Loss and Anemia
Infect small bowel, lacerate the bowel mucosa, causing intestinal blood loss, which can produce symptomatic disease in heavy infestations.
larvae penetrate epidermis and enter the venous circulation. Travel to the lungs and lodge in alveolar capillaries
**Most important cause of chronic anemia worldwide

Question 8

Stronglyoidiasis

Answer 8

Disseminated in Immunocompromised
S. stercoralis
Worms mature in the small bowel
**May reproduce in human hosts via Autoinfection
Internal autoinfection is increased in these patients& a lot of filariform larvae penetrate intestinal walls and disseminate to distant organs.
Gut may show ulceration, edema and severe inflammation

Question 9

Pinworm (Enterobiasis)

Enterobius vermicularis

Answer 9

Perianal itching
Most common amongst children
Adult female resides in the cecum ad appendix, but migrates to the perianal region to deposit eggs.
The eggs stick to fingers, bed linens, towels and clothing.
Readily transmitted from person to person

Question 10

Trichinosis

Trichinella spiralis

Answer 10

Myositis acquired by eating pork w/ cysts
larvae from the small bowel invade the intestinal wall and enter circulation, they can only survive in striated skeletal muscle, where they encyst and remain viable for years.
Skeletal muscle is the major site of tissue damage
Cysts calcify
Most infections are asymptomatic

Question 11

Visceral Larva Migrans (toxocariasis)
Toxocara canis
Toxocara cati

Answer 11

Transmitted by cats and dogs
Infection of deep organs
Larvae invade intestinal wall, carried to the liver, reach systemic circulation
In tissue when the larve die & elicit small granulomas, which eventually heal by scarring.
Many cases are asymptomatic, but can cause severe disease.
Hypereosinophilia, pneumonitis, hypergammaglobinemia, ocular manifestations (cheif complaint of loss of vision in one eye)

Question 12

Cutaneous Larva Migrans

Answer 12

Puritic eruption
Caused by larval nematodes migrating through the skin, where they provoke severe inflammation that appears as serpiginous urticarial trails.

Question 13

Dracunculiasis

Dracunculiasis medinensis “guinea worm”

Answer 13

Infection of CT and SubQ tissues
Contaminated drinking water
A year after ingestion of infected crustaceans pruritic uticarial rash, systemic allergic symptoms appear. Reddish papule develops and vesiculates
Dead worms provoke an intense inflammatory response, causing debilitation in many patients

Question 14

Schistosomiasis (bilharziasis)
Schistosoma mansoni
Schistosoma haemtobium
Schistosoma japonicum

Answer 14

**Most important human helminthic disease
Intense inflammatory & immune responses damage the liver, intestine or urinary bladder
Alternate b/w asexual generations in snail and sexual generations in vertebrate host.
Cercaria penetrate human skin, tissue, BV & migrate to the liver and lungs.
Basic lesion is a circumscribed granuloma- leading to ischemic damage to adjacent tissue.
Progressive scaring and dysfunction in affected organs.
Hepatic involvement leads to portal hypertension, splenomegaly, ascites. Intestinal disease is usually only minimally symptomatic. In the bladder, hematuria, recurrent UTIs & sometimes progressive obstruction leading to renal failure.

Question 15

Clonorchis sinensis

Answer 15

Clonorchiasis leads to biliary obstruction
usually causes only mild symptoms, sometimes associated with bile duct stones, cholangitis and bile duct cancer.
Uncooked freshwater fish containing larvae- Asain countries
Adult worms live in bile duct, elicits an inflmmatory response that does not eliminate the worm, but causes dilation and fibrosis of the ducts.
Most infected persons are asymptomatic

Question 16

Paragonimus westermani

Answer 16

Paragonimiasis is a lung disease
Uncooked fresh crabs- Asian countries
**Unlike TB peripheral eosinophilia is common

Question 17

Fasciola hepatica

Answer 17

Fascioliasis is a biliary disease acquired form sheep
Small bowel to peritoneal cavity, penetrate the liver ad migrate through the hepatic parenchyma into the bile ducts.
Adults feed in hepatocytes. Induce hyperplasia of bile duct epithelium, portal and periductal fibrosis, proliferation of bile ductules & varying degrees of biliary obstruction.
Eggs lead hepatic abscesses and granulomas.

Question 18

Fasciolopsis buski

Answer 18

Fasciolopsiasis in an infestation of the small bowel.
Eating aquatic veggies contaminated w/ cysts
Giant intestinal fluke attached to intestinal wall, which may ulcerate, become infected adn cause pain like that of a peptic ulcer.
Acute symptoms may be due to intestinal obstruction of by toxins released by large numbers of worms.

Question 19

Taenia saginata

Answer 19

Intestinal tapeworm acquired from eating undercooked beef contain cystic larvae in muscle
Grows into adult form in humans
Usually asymptomatic

Question 20

Taenia solium

Answer 20

Intestinal tapeworm acquired from eating undercooked pork contain cystic larvae in muscle
Grows into adult form in humans
Cysticercosis- systemic infection caused by the release of oncospheres from the ingested eggs, which penetrate the gut wall and enter the blood stream
Multiple cysticeri in the brain- “swiss cheese” appearance

Question 21

Diphyllobothrium latum

Answer 21

Intestinal tapeworm acquired from eating undercooked fish contain cystic larvae in muscle
Grows into adult form in humans
Usually asymptomatic

Question 22

Echinococcus granulosus

Answer 22

Echinococcosis (hydatid disease)-
Humans contaminated by infectious eggs-herding population
Adult tapeworm lives in small intestine, has scolex w/ suckers and numerous hooklets to attach to the intestinal mucosa.
Hydatid cyst is slow growing and is only discovered when it interferes with normal function.
Major complication of cyst rupture is seeding of adjacent tissues w/ brood capsules and scolices. These germinate, produce additional cysts, each with the growth potential of the original cyst.