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79 Cards in this Set
- Front
- Back
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What kind of parasite is tricinellosis?
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Round worm: Nematode
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What is unique about trichinella?
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Its one of the smallest nematodes
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What kind of disease is trichinellosis? (transmitted)
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Food-borne zoonosis
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Where is there the greatest incidence of this disease?
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In developing countries
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Which trichiniella species infect humans?
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T. spiralis
T. britovi T. murreli T. nativa T nelsoni T. pseudospiralis |
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Which trich species can be found in North America?
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T. murreli
T. nativa |
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Which trichinella species affects the arctic?
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T nativa
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Do all trichinella species encyst?
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NO!
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Which trichinella species do not encyst?
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T. pseudospiralia
T. papuae T. zimbabwensis |
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How does this worm behave?
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Like a virus
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Is this worm segmented?
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No
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Is this worm host specific?
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No, can adapt to a variety of hosts
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Which 2 countries are free of trichinellosis?
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Puerto Rico
Australia |
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Where does this nematode go once it infects somebody?
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Goes INTO the cells
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What is the widespread form of this parasite?
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T. pseudospiralis
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What is the most common American Trich?
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T. murreli
Also have T genotype 6 in the States and Canada |
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How can someone get infected with this worm?
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Eating undercooked meat
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What happens when you ingest the worm?
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Juveniles are carried by the hepatoportal system, though the liver, heart, lungs and arterial system
Eventually reach the skeletal muscle |
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Where can this nematode be found in the body?
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In all tissues
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How is Trichinella like a virus?
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Penetrates individual fibers
Subverts and redirects the host cell activities to its own survival Alters gene expression of the host cells from that of a contractile fiber to that of a nurse cell |
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What is unusual about Trichinella as a nematode?
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Largest Intra-cellular parasite
NON-host specific Smallest worms amongst nematodes One of the most widespread and clinically important nematode in the world Same individual can serve as the definitive and intermediate host |
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Does trichinella cause larval migrant like Strongyloides?
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No, it cannot cause larval migrants
->Goes everywhere in the body except the skin |
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Describe the life cycle of Trichinella for humans
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Infected mostly by eating raw meat that contains infective juveniles
Juveniles digested from muscle Juveniles penetrate into tissues of small intestine and grow to sexual maturity Male and female worm mate, female produce living juveniles, which are shed into the lymph Juvenile worms migrate into muscles of the host and mature into the infective stage |
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How are carnivores and omnivores infected?
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When they eat meat containing the infective juvenile stage
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How long does it take the larvae that are released in the stomach to mature?
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1-2 weeks in the bowel
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What are the clinical symptoms once infected with this worm?
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Following infection have: irritation, abdominal cramping
Once larvae have migrated and penetrated the muscle: Eosinophilia, muscle pain, CNS/cardiac damage |
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Which Trichinella species do not encyst?
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T. papuae, T. pseudospiralis, T. zimbabwelis
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What kind of a parasite is trichinella?
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Zooonotic
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Does human infection play a role in the trichinella life cycle?
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No
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Where does the sylvatic cycle take place?
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Temperate zone
Tropic zone Arctic zone |
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How many molts do Trichinella larvae undergo to develop into adults?
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4 molts in a 30 hour period
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How long is the female trich?
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3 mm
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How long is the male trich?
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1.5 mm
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How long is the newborn?
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0.8 mm
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When do females begin to release larvae?
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After a few copulations (males die after several copulations)
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When does patency begin?
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5 days after mating
(males die soon after adult females release offspring) |
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How are the larvae distributed throughout the body?
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By the hepatoportal system
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What are the steps leading to encystation?
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Larvae enter the muscle fiber cell
Fiber loses myofilaments fiber nuclei enlarge Fiber smooth endoplastic reticulum increases Fiber mitochondria degenerates Encapsulation of the unit with collagen secreted by neighbouring fibroblasts |
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What do the larvae do once they enter the host cell?
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Alter the gene expression on the host cell
-->Able to change the vocation of the contractile fiber to that of a nurse cell -->Become intracellular parasites |
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How long does it take to calcify encysted larvae?
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~18 months
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What is the reservoir for T. spiralis and T. pseudospiralis?
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Pig
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What is the reservoir for T. nativa?**
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Polar bear
Walrus |
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What is the reservoir for T. britovi?
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Fox
Opossum Stray dogs/cats |
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T. spiralis:
Distribution Reproductive capacity Freezing resistance |
Distribution: Cosmopolitan
Reproductive capacity: High* Freezing resistance: None |
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T. nativa
Distribution Reproductive capacity Freezing resistance |
Distribution: Arctic region
Reproductive capacity: Low Freezing resistance: Yes, resistant ** |
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T. pseudospiralis
Distribution Reproductive capacity Freezing resistance |
Distribution" Cosmopolitan
Reproductive capacity: low Freezing resistance: Yes, resistant ** |
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T. nelsoni
Distribution Reproductive capacity Freezing resistance |
Distribution: Africa
Reproductive capacity: Low Freezing resistance: yes, resisitant |
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What special characteristic does T. pseudospiralis have?
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Doesn't have a capsule
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Which Trichinella species don't have capsules?
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The one that don't encyst don't have capsules
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What is a stichosome?
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Row of discoid cells containing secretory granules
-->These cells are stichocytes |
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What do stichocytes secrete?
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Ag into the nurse cell-parasite complex during nurse cell formation
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What is assumed about the substances secreted by the stichocytes?
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They are immunogenic and mediate alteration of host gene expression
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Is there an equal distribution of the worm in the muscle?
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No, some muscles are more heavily invaded than others (unknown reason)
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What are the most frequently infected muscles?
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Eyes
Tongue Masticatory muscles diaphragm Intercostals Arms Legs |
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Where do nurse cells not form?
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In the heart muscle cells
Do not encyst in smooth muscles -->Myocarditis is transitory Do not form in the nervous system |
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What happens when the muscles are invaded by this parasite?
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Intense inflammatory reaction
Edema develops after 2 weeks |
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When is the inflammatory reaction raised?
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After the release of secretory-excretory Ags
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What are the 3 categories under which resistance to infections can be classified?
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Innate resistance
Non-specific acquired immunity Specific acquired immunity |
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Describe innate resistance
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Natural resistance to infection
-->Trichinella is not infective to fish or amphibians Innate immunity can act like a barrier (mucus) |
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Describe non-specific acquired immunity
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Resistance acquired after first contact with an unrelated infectious agent or an immunogenic substance
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What are some examples of non-specific acquired immunity?
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1st infection with M tb protect vs trichinellosis cuz acquired immunity to Trich needs Th1 types response, which is what M tb stimulates
Mice infected with Toxoplasma are protected vs Trich, because that also stimulates Th1 type |
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Desscribe specific acquired immunity
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Resistance acquired after a first contact with the same infectious agent
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Which Th arm plays a role in trichinellosis immunity?
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Both Th1 and Th2
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Which Ab are made vs this worm?
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IgM, IgG, IgE
IgA in the gut |
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What other immune systems play a role in fighting off this worm?
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T cells (Tcyt)
ADCC |
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How do T cells help combat this infection?
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1) Ag stimulates DCs, macs
-> Activates T cells, which makes GM-CSF, IL-3, IL-5, which attracts Eosinophils 2) Trich Ag can stimulate eosinophils, which can activate T cells which respond back to the eosinophil |
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When does pathogenesis occur?
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After the 3 stages of development
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What are the 3 stages of development of this worm?
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Intestinal stage
Migrating larvae Muscle |
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Describe the intestinal stage
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Worms migrating in the intestinal epithelium cause traumatic damage to the tissues
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What pathogenesis is caused by this stage?
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Inflammation causes nausea, vomiting, sweating and diarrhea
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Describe the migrating larvae stage
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Juveniles damage blood vessels
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What pathogenesis is caused by this stage?
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Edema
Also: pneumonia, encephalitis eye damage |
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What happens in the muscle stage?
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Formation of the nurse cell
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What pathogenesis is caused by this stage?
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*Muscle pain*
Difficulty breathing and swallowing Also have edema and eosinophilia in tissues |
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What are the 4 cardinal features of this disease?
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Fever
Orbital edema Myalgia Eosinophilia |
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What is a frequent sign of acute trichinellosis?
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Nailbed hemorrhages
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How can this disease be diagnosed?
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Subclinical cases go undetected
Adult worms cannot be detected in the stool Juvenile migrants cannot be detected -->Muscle nurse cells are detected by biopsy -Serology not very sensitive in the acute phase -PCR useful in epidemiological studies |
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How can larvae be seen in the muscle?
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Crushing the tissue btw microscope slides
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How can this be treated?
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Basically treat to relieve the symptoms
->Use analgesics and immunosuppresive drugs: Prednisone and corticosteroids to reduce the inflammation |
