Trichinella spp. (1)

Question 1

What are the hosts?

Answer 1

Mammals

Birds

Reptiles

Question 2

How do you identify?

Answer 2

Adult stage - rarely found

Infection usually identified by presence of coiled L1 in striated muscle

Question 3

Explain the life cycle

Answer 3

L1 infective

Encysted in striated muscle - primarily in masseter and diaphragm

Infected by ingesting L1 in muscle

Develop into adults in small intestine

Embryonic prelarval stage enter lymphatic vessels of the gut, migrate and encyst in striated muscle

One animal eating another determines the epidemiology of trichinellosis

Ingestion of raw meat (cannibalism, cryptocannibalism, or wild animals)

Larvae establish in small intestine, molt 4 times and become adults

Females invade the small intestinal wall within 4-5 days

L1 larvae may be diagnosed after 17-21 days

Urban transmission cycle
- People -> Pigs -> Rodents

Sylvatic and arctic life cycles
- Wild fauna maintain transmission through predation, cannibalism,
carrion

Domestic Pig Cycle - transmission is maintained by feeding pigs on
food waste containing flesh of infected pigs
- Rats in piggeries maintain a secondary cycle

Question 4

What is the site of infection?

Answer 4

Adults - small intestine

Larvae - Muscles

Question 5

Describe the Pathogenesis

Answer 5

Transmission to humans is commonly associated with ingestion of raw or undercooked pork

Infections also result from improperly cooked horse meat or game meats such as bear, walrus, cougar, or wild boar

Cases associated with domestic swine have decreased
- Other meats have increased

Only humans exhibit clinical signs
- Other animals - infections are asymptomatic

Question 6

How do you diagnose?

Answer 6

3 methods
- Pooled sample digestion: pepsin and HCl added to ground skeletal
muscle, incubated, and the sediment
examined for L1 under microscope
- ELISA: Detects antibodies to Trichinella in serum. Fluids from
muscle at slaughter is simpler and quicker than collecting
blood and processing for serum
- Squash preparation: Muscle tissue squashed between 2 slides and
scanned under microscope. Detect moderate
to heavy infections

Question 7

How do you treat and prevent?

Answer 7

Anthelmintic treatment uncommon

Any meat fed to pigs should be cooked and rats in housing controlled

Meat inspection and consumer education essential to prevent human infection

Hogs raised outdoors in close contact with rodents and other wildlife have an increased change of acquiring Trichinella infection

Question 8

What is important about Trichinella spp.?

Answer 8

It is ZOONOTIC