Nematodes- Trichinellosis

Question 1

Which species causes trichinellosis?

Answer 1

species from the Trichinella genus

Question 2

What makes Trichinella parasites unique?

Answer 2

largest INTRA-cellular parasites, smallest nematodes, great cause of disease worldwide, same host is both definitive AND intermediate host

Question 3

What is the distribution of Trichinella?

Answer 3

worldwide EXCEPT Puerto Rico and Australia

Question 4

Which sex is larger?

Answer 4

the female

Question 5

How are Trichinella transmitted?

Answer 5

form cysts in muscle tissue, therefore passed by ingesting infected, improperly cooked meat. bears are heavily infected

Question 6

Is trichinellosis a zoonose?

Answer 6

yes. humans are accidental hosts

Question 7

How is Trichinella an intra-cellular parasite?

Answer 7

multi-intracellular parasite, has parts of body in different cells at one time. characteristic of L1-L5 phase larvae

Question 8

Which muscles are more heavily invaded?

Answer 8

eye, tongue, masticator muscles, diaphragm, intercostals, arms, legs

Question 9

Which muscles do not get infected by Trichinella nurse cells (cysts)?

Answer 9

heart muscle, smooth muscle, or nervous tissue

Question 10

What are the steps of trichinellosis pathogenesis?

Answer 10

1. larvae enter muscle fibre cell
2. fibre loses its myofilaments
3. fibre nuclei enlarge
4. fibre smooth ER increases
5. fibre mitochondria degenerate
6. encapsulation of the unit by collagen secretion by adjacent fibroblasts

Question 11

How are Trichinella juveniles like viruses?

Answer 11

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

Question 12

What do Trichinella larvae do to the muscle fibre?

Answer 12

they transform them into nurse cells by inducing angiogenesis around the cell

Question 13

What are the five Trichinella species that affect humans?

Answer 13

T. spiralis, T. nativa, T. britovi, T. pseudospiralis, T. nelsoni

Question 14

What is the stichosome?

Answer 14

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

Question 15

What does the stichocyte cytoplasm contain?

Answer 15

mitochondria, golgi-like structure, RER, 2 types of secretory granules

Question 16

Which 3 stages of development cause disease?

Answer 16

intestinal stage, migrating larvae, muscle stage

Question 17

What is the pathology of the intestinal stage?

Answer 17

causes traumatic damage to the tissues. causes nausea, vomiting, sweating and diarrhea

Question 18

What is the pathology of the migrating larvae?

Answer 18

juveniles damage blood vessels, causing localized edema. can cause pneumonia, encephaitis, eye damage, etc

Question 19

What symptoms do muscle cysts cause?

Answer 19

muscle pain, difficulty breathing and swallowing. causes intense inflammatory reaction in muscle tissue that is alleviated after the secretion of antigen from the stichocytes

Question 20

Which species are not affected by trichinellosis?

Answer 20

fish, reptiles, amphibians are innately protected

Question 21

What are the three types of immune response?

Answer 21

innate response, non-specific acquired immunity, specific acquired immunity

Question 22

What is an example of non-specific acquired immunity with trichinellosis?

Answer 22

previous infection with Mycobacterium tuberculosis protects against trichinellosis because both cause similar Th1 type response
similarly, mice infected with Toxoplasma are protected against trichinellosis

Question 23

Which cells are present after a specific acquired immune response to trichinellosis?

Answer 23

IgM, IgG and IgE in the serum, IgA in the gut, cell mediated Th1 response (particularly eosinophils)

Question 24

How can trichinellosis be diagnosed?

Answer 24

adults and migrating juveniles cannot be detected, muscle nurse cells are detected by biopsy, serology is not very sensitive, PCR is useful

Question 25

How can trichinellosis be treated?

Answer 25

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