1. Presented by: Lauren Hannan and Chloe Jensen
Trichinella spiralis
Presented by: Lauren Hannan and Chloe Jensen

2. Taxonomy Kingdom: Animalia Phylum: Nematoda Class: Adenophorea
Order: Trichurida
Family: Trichinellidae
Genus: Trichinella
Species: T. spiralis

3. Introduction
Trichinella spp. is the smallest nematode parasite of humans, which has the most unusual life cycle, and is one of the most widespread and clinically important parasites in the world
Worlds largest intracellular parasite
T. spiralis is actually several strains – 8 “sibling species” are recognized
No morphological differences among the different kinds of Trichinella
Geographic distribution: worldwide

4. Morphology
Males are about 1.4 mm – 1.6 mm long, and are flat anteriorly and posteriorly
Have a large copulatory pseudobursa on each side
Females are about twice the size as males
Vulva is found near the esophagus
The single uterus of the female is filled with developing eggs in the posterior portion, while the anterior portion contains the fully developed juveniles.

5. Hosts Definitive Intermediate hosts Accidental hosts
Carnivorous and omnivorous animals, such as pigs or bears
Intermediate hosts
Primarily rodents
Accidental hosts
Humans

6. Life cycle
Trichinellosis is acquired by ingesting meat containing cysts (encysted larvae) of Trichinella
Once larvae enter the stomach and are exposed to digestive enzymes such as gastric acid and pepsin, the larvae burst out of the cysts and invade the small intestine, where they develop into adults
Live for about 4 weeks in the small intestine
After 1 week, females release larvae that migrate to the striated muscles and encyst – alter gene expression of the host cell!
Complete encystment takes about 4-5 weeks
Encysted larvae can remain viable for several years

7. Life cycle continued
Life cycle traditionally considered to be two epidemiologically distinct types: a domestic (involving pigs and rats, around human habitation), and a sylvatic (involving wild animals)
Rodents are primarily responsible for maintaining the endemicity of this infection
Carnivorous/omnivorous animals, such as pigs or bears, feed on infected rodents or meat from other animals
Humans become accidentally infected when eating improperly processed meat of these animals (or when eating food contaminated with such meat)

9. Pathogenesis Causes Trichinosis Three stages of pathogenesis:
Stage 1: penetration of adult females into the mucosa:
12 hours – 2 days after infection
Low grade infection
Worms migration in intestinal epithelium causes:
Traumatic damage to the host tissues
Inflammation
Nausea, vomiting, diarrhea,
Sweating
Respiratory difficulties
Red skin blotches
Stage ends with facial edema and fever

10. Pathogenesis Continued
Stage 2: migration of juveniles:
Damages blood vessels, creating:
Localized edema
Pneumonia, pleurisy
Encephalitis, meningitis, nephritis, peritonitis
Deafness, brain/eye damage
Sublingual hemorrhage
Death from myocarditis may occur
Don’t stay in the heart, migrate through causing necrosis and infiltration of leukocytes

11. Pathogenesis Continued
Stage 3: Juvenile penetration of muscle fibers:
Symptoms are varied and vague
Intense muscle pain
Difficulty breathing/swallowing
Masseter muscle swelling
Weakening pulse and blood pressure, heart damage
Various nervous disorders
Death by heart failure, respiratory complications, and kidney malfunction
Heavy infection causes:
Reduced heart muscle contraction
Reduced stress, work, and power output

12. Diagnosis Most cases go undetected
Routine exams rarely detect juveniles
Muscle biopsy is the most accurate form of diagnosis
Digestion of the muscle in artificial gastric enzymes for several hours

13. Treatment No treatment Just relieve symptoms Thiabendazole
Analgesics and corticosteroids
Purges during beginning symptoms can dislodge worms
Thiabendazole
Effective in animals
Human trials have been variable

14. Control Cook pork and meats properly and freeze unused meat
Watch out for “backyard butchering”
Don’t used uncooked garbage for pig food
Keep pig pens clean
Proper hygiene and sanitation

15. Review What is the geographic range of this parasite?
What kind of hosts are humans?
T/F: Males are larger than females
After the larvae leave the small intestine, where do they migrate to? How long can they survive there?
What is the treatment method?
Name a control method
What is the most effective diagnosis method?
How does death typically occur?