Parasites 1

Question 1

What is the difference between a definitive and intermediated host?

Answer 1

definitive- host in which the sexual stage of a parasite life cycle occurs
intermediate-host in which asexual reproduction or development occurs

Question 2

What is a reservoir?

Answer 2

animal host that maintain the natural cycle in the wild (often not harmed by the carriage)

Question 3

List the CDC neglected parasitic infections in the US.

Answer 3

Chugs
Cysticercosis
Toxocariasis
Toxoplasmosis
Trichomoniasis

Question 4

Contrast the immune responses to parasitic and protozoan parasites.

Answer 4

helminth- eosinophils and TH2 response

protozoan: TH1 response

Question 5

T/F Although parasites vary widely by phylum, they are separated from hosts as prokaryotes.

Answer 5

F. Parasite represent a wide variety of phylums within eukaryotes, which is shared with humans and other mammals

Question 6

Distinguish the difference between cyst and cysticerci.

Answer 6

cyst is a dormant stage found encysted in hosts (intermediate or definitive) in undercooked meat

cysticerci: encysted chested larval forms in an infected intermediate host (Hydatid is a specialized cysticercal form in Echinoccocccus granulosus)

Question 7

Contrast the physical characteristics of cestoda and trematoda and examples of each.

Answer 7

cestoda (tapeworms) have flat segmented bodies that they use to absorb nutrients, attaching by scolex and reproduce by hermaphroditic reproduction using proglottids: Tania saginata, solium, Diphyllobothrium datum, Echinoccoccus granulosus

trematoda (flukes) have a simple digestive system and single opening as mouth and anus, intermediate often a snail and transmission can be invasive or ingestive: Schistosoma spp.

Question 8

How can you contract Taenia infection and how can spread and what infections result from each route of transmission.

Answer 8

infection by ingesting raw or undercooked infected meat that includes cysticerci (tapeworm of the intestine) or when they eat tapeworm eggs from humans (cysticercosis of the muscle, eyes and brain)

both forms can occur in the same person

Question 9

What are the symptoms of Taeniassis or Cysticercosis?

Answer 9

often asymptomatic or causes abdominal discomfort, occasionally NVD, weight loss and obstruction

cysticercosis: symptoms related to tissue involved: muscle lumps, brain neurocysticercosis (confusion, balance difficulty, brain swelling, excess fluid around the brain, seizures, headaches and mortality

Question 10

What are the dx. and tx. available for Taenia infection.

Answer 10

self or clinical observation of active prologttids/ proglottids or eggs in the stool; CAT/MRI: ribbon-like structure in the intestine, or calcified dead larva visible often

tx is praziquantel, niclosamide or albendazole, single dose effective for adult worms, prolonged treatment for cysticerci

humoral response, reinfection possible

Question 11

How is Diphyllobothrium latum infection unique from other tape worm infections?

Answer 11

caused by undercooked fish containing larvae (copepod infects fish)

causes B12 deficiency and anemia with neurological symptoms

additional tx is Vitamin B12 deficiency if evident

Question 12

How is Echnoccocosis transmitted? What is the resulting infection?

Answer 12

ingestion of eggs from dogs (definitive host) who eat raw intestine (intermediate host is ungulates) and effects primarily the lungs and liver but also the spleen, kidneys, heart, bone and CNS **formation of hydatid cysts (large), onset of disease when cysts cause pain or rupture; anaphylaxis associated with rupture can be fatal

humans serve only as a dead end host

Question 13

How is echinococcosis dx or tx?

Answer 13

immunology is pathologic, dx. by risk factors of area with serology for confirmation

tx. percutaneous drainage with instillation of hypertonic saline or alcohol of cysts, or surgical removal with care to avoid rupture; DEWORM dogs

Question 14

Correlate the different species of Schistosomiasis with the location of blood invasion and site of egg migration.

Answer 14

S. mansoni: mesenteric veins- descending colon
S. japonica: superior mesenteric veins- small intestine
S. haematobium: venous plexus- bladder

Question 15

How is schistosomiasis transmitted?

Answer 15

is an invasive aquatic free-living cercaria that can penetrate skin with snails as an intermediate host, this is most common when public or agricultural water supply is contaminated with human waste

peak infection is in children playing in the water in their second decade; S. mansion and heamatobium mostly in Africa, S. japonicum mostly in Asia

Question 16

How are schistosome eggs differentiated?

Answer 16

Distinctive spikes determine the eggs (i.e. lateral v. terminal)

Question 17

What are the symptoms of early, middle and chronic schistosomiasis pathology?

Answer 17

early: many have no symptoms, rash and hypersensitivity to exposure, fever headache and nausea with larval migration
middle: symptoms mostly from immune response to eggs (Katayama syndrome), intestinal causes abdominal pain, diarrhea and blood in stool, urogenital cause hematuria
chronic: eggs lodge in the tissues, esp. intestine/liver, bladder respectively and egg secretion lead to eosinophilic inflammatory response of granuloma formation and cancer, liver disease and portal HTN, or bladder mucosal thickening/cancer

Question 18

What is the dx/ treatment for schistosomiasis?

Answer 18

dx by observation of eggs in feces or urine

single dose praziquantel in S.m and S.h. or multiple doses in S.j. which potentiates the active immune system killing of adult worms

avoid contact with contaminated water