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Intestinal Nematodes > Trichinelosis > Flashcards

Trichinelosis Flashcards

1
Q

Trichinella spiralis has 4 subspecies:

A

Trichinella spiralis spiralis- cosmopolitan
Trichinella spiralis nelsoni -afrucan predators and scavenger
Trichinella spiralis nativa- arctic polar bears
Trichinella spiralis pseudospiralis- birds and mammals

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2
Q

Where does the adult form live ?

A

Duodenal and jejunal mucosa of flesh eating mammals

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3
Q

Infectious Larval form lives??

A

In striated muscles of carnivorous and omnivorous mammals

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4
Q

Describe epidemiology of trichinella spiralis

A

Cosmopolitan more in Us than in tropics and orient
Associated with pork consumption
Adult worm lives buried in SI mucosa of pig rat or man
Also polar bears in arctic account for outbreaks

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5
Q

Estimates

A

1.5 m American carry trichinella cysts in their musculature
150k to 300k new infections annually

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6
Q

Morphology

A

One of the smallest nematodes
Females 3-4mm
Males- 1.4-1.6mm, have tail end pappilae - claspers - hold onto female when mating
Larvae :80um

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7
Q

Classification of female Trichinella based on egg/larvae laying

A

Viviparous- release 1st stage larva in SI

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8
Q

Adult life span of Trichinella is short. Explain

A

Male dies after fertilizing females
Females die after discharging larvae- approx 16 weeks

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9
Q

Life cycle

A
  • sylvatic cycle
  • domestic cycle

Enteric stage- ingestion of meat that contains encysted larvae> larvae released into small intestine> mature into adults in the small intestine where fecund female produce first stage larvae
Systemic/migratory stage- larvae penetrate the gut, enter lymphatics and then circulation via thoracic duct.
Diagnostic/ infective stage - larvae enter striated muscle ( extraocular, tongue, deltoid, PECS, gastrocnemius) > larvae molt, encyst and develop into infective third larvae within the 15 days

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10
Q

Where does the encystment happen?

A

Where muscles attach to tendons
And superficially in bulky muscle

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11
Q

T/F: only a single cycle of trichinella occurs in one host

A

True
For continuation of the cycle and maintenance of species, infection needs to be transmitted to another host. Same or different species

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12
Q

T/F: salting, smoking and drying destroys larval forms

A

False

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13
Q

Prolonged freezing decontaminates trichinella

A

True (20days)

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14
Q

T/F : man is the dead end host of the parasite

A

True

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15
Q

T/F: larvae kills all cells they enter except striated muscle

A

True

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16
Q

How long does it take the larvae to encyst

A

20 days after entry of the larvae into the muscle cell

17
Q

Nurse cell

A

First muscle cell invaded

18
Q

Muscles invaded most frequently are??

A

Have low glycogen levels and are relatively active.
Extraocular muscles of the eye
Tongue
Jaw
Deltoid , pectoral
The diaphragm
Gastrocnemius

19
Q

Cysts in trichinella

A

Are formed by tissue reaction around encapsulated larvae.
Ovoid approx 400 by 250um
May calcify in 2 years but remains viable even in calcified cysts

20
Q

T/F : the cysts lie longitudinally ALONG muscle fibres

A

True

21
Q

Most common muscle used for biopsies

A

Deltoid

22
Q

Clinical features of trichinella

A
  1. Enteric phase- penetration of host intestinal mucosa
  2. Larval migration - migratory phase - muscle invasion
  3. Intramuscular encystment
23
Q

Enteric phase-

A

2-30 hrs after ingestion
Presents as acute food poisoning

24
Q

Larval migration/ migratory phase

A

1-4 weeks after infection
Pneumonia, splinter hemorrhages, facial edema neurological symptoms

25
Q

Intramuscular encystment

A

Difficulty swallowing
Dyspnea-
Myocarditis
Respiratory arrest
Lethal trichinosis

26
Q

Splinter hemorrhages

A

Under Fingernails

27
Q

Lab diagnosis

A

Clinical observation and eosinophilia
Positive history of pork consumption
Serological test - ELISA, western blot,
Muscle biopsy - digest with pepsin and examine trichinoscope
Brachman intradermal test
Molecular test - PCR

28
Q

Lethal trichinitis

A

Combines myocarditis, encephalitis, meningitis and pneumonitis

29
Q

Respiratory arrest

A

Heavy invasion and muscle destruction of diaphragm

30
Q

Treatment

A

Anthelmintic not effective for newborn or maturing larvae
Corticosteroid and mebendazole ( within 2 weeks of eating contaminated meat or GI symptoms) for severe illness

31
Q

Prevention

A

Cook meat to temperature of 55°c or higher education on pork transmission from pork and bear meat
Avoid rats in piggery
Avoid feeding garbage or pork scrabs to pigs
Meat and pork inspectors in abbatoirs
Irradiation of packaged meat

32
Q

Heavy infection

A

Approx 1000 cysts / gram of muscle

Intestinal Nematodes (8 decks)

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