Nematodes- Trichinellosis Flashcards
Which species causes trichinellosis?
species from the Trichinella genus
What makes Trichinella parasites unique?
largest INTRA-cellular parasites, smallest nematodes, great cause of disease worldwide, same host is both definitive AND intermediate host
What is the distribution of Trichinella?
worldwide EXCEPT Puerto Rico and Australia
Which sex is larger?
the female
How are Trichinella transmitted?
form cysts in muscle tissue, therefore passed by ingesting infected, improperly cooked meat. bears are heavily infected
Is trichinellosis a zoonose?
yes. humans are accidental hosts
How is Trichinella an intra-cellular parasite?
multi-intracellular parasite, has parts of body in different cells at one time. characteristic of L1-L5 phase larvae
Which muscles are more heavily invaded?
eye, tongue, masticator muscles, diaphragm, intercostals, arms, legs
Which muscles do not get infected by Trichinella nurse cells (cysts)?
heart muscle, smooth muscle, or nervous tissue
What are the steps of trichinellosis pathogenesis?
- larvae enter muscle fibre cell
- fibre loses its myofilaments
- fibre nuclei enlarge
- fibre smooth ER increases
- fibre mitochondria degenerate
- encapsulation of the unit by collagen secretion by adjacent fibroblasts
How are Trichinella juveniles like viruses?
they invade the hepatoportal system and pass through all types of tissues before reaching skeletal muscle.
they invade host cells, redirect the host cell metabolism for their own survival, and alter host cell gene expression
What do Trichinella larvae do to the muscle fibre?
they transform them into nurse cells by inducing angiogenesis around the cell
What are the five Trichinella species that affect humans?
T. spiralis, T. nativa, T. britovi, T. pseudospiralis, T. nelsoni
What is the stichosome?
the mature muscle larval stage that forms a single row of ~50 cells called stichocytes.
antigens released by stichocytes cross-react with antigen of living muscle larvae. may be immunogenic and responsible for host cell gene expression alteration
What does the stichocyte cytoplasm contain?
mitochondria, golgi-like structure, RER, 2 types of secretory granules
Which 3 stages of development cause disease?
intestinal stage, migrating larvae, muscle stage
What is the pathology of the intestinal stage?
causes traumatic damage to the tissues. causes nausea, vomiting, sweating and diarrhea
What is the pathology of the migrating larvae?
juveniles damage blood vessels, causing localized edema. can cause pneumonia, encephaitis, eye damage, etc
What symptoms do muscle cysts cause?
muscle pain, difficulty breathing and swallowing. causes intense inflammatory reaction in muscle tissue that is alleviated after the secretion of antigen from the stichocytes
Which species are not affected by trichinellosis?
fish, reptiles, amphibians are innately protected
What are the three types of immune response?
innate response, non-specific acquired immunity, specific acquired immunity
What is an example of non-specific acquired immunity with trichinellosis?
previous infection with Mycobacterium tuberculosis protects against trichinellosis because both cause similar Th1 type response
similarly, mice infected with Toxoplasma are protected against trichinellosis
Which cells are present after a specific acquired immune response to trichinellosis?
IgM, IgG and IgE in the serum, IgA in the gut, cell mediated Th1 response (particularly eosinophils)
How can trichinellosis be diagnosed?
adults and migrating juveniles cannot be detected, muscle nurse cells are detected by biopsy, serology is not very sensitive, PCR is useful
How can trichinellosis be treated?
Analgesics and immunosuppressive drugs like
prednisone and corticosteroids are given to relieve
the symptoms due to the intense inflammatory
reaction.
mebendazole and albendazole are used to eliminate worms from the intestine, but not recommended to remove nurse cells
with small pathogens such as these, most of the pathology is due to the immune system reaction
