Doug Mandler & Albert Teo PRESENTS Trichinela spiralis

Taxonomy Kingdom: Anamalia Phylum: Nematoda Class: Adenophorea Order: Trichocephalida Family: Trichinellidae Genus: Trichinella Species: spiralis * Please note that we will be discussing 5 different subspecies of Trichenella spiralis

General Facts Able to infect a wide range of mammalian hosts Trichinellosis is the collective term used to describe the diseases that this parasite cause Considered endemic in Japan and China Top carnivores are usually infected Smallest nematode of humans Trichinella spiralis is the worlds largest intracellular parasite.

Question! There are five different subspecies for Trichinela spirals. Can you name one of them? 5 subspecies are: T. spiralis (T1) T. nativa (T2) T. britovi (T3) T. pseudospiralis (T4) T. nelsoni (T7)

Geographic Range Worldwide Most common in parts of Europe and the United States.

Definitive Host Almost any species of mammal can get affected Humans Pigs/boars Bears Walruses Tasmanian devil Raccoon dogs Domestic pigs are the main reservoir host for T. spiralis

Morphology

Morphology cont. The males measure 1.5 mm in length by 36 µm in diameter Females are about twice the size of males (measuring 3 mm in length by 36 µm in diameter) Larvae are about 0.08 mm long by 7 µm in diameter

Life Cycle CDC

Life Cycle in picture

Question II How many newborn larvae are estimated to be shed from the adult female in her life time? ~ 500 to 1,500

Life Cycle in words Adult worms live around the columnar epithelial cells of the small intestine and the larvae live in striated muscle cells of the same mammal The worm can infect any species of mammal that consumes its encysted larval stages (Nurse cell complex) While in the small intestine, they are considered to be intracellular-multicellular organisms In order for the life cycle to continue, an infected host must die and be eaten by another mammal

Life Cycle : Enteral Phase When an animal eats meat that contains infective Trichinella cysts, the acid in the stomach dissolves the hard covering of the cyst and releases the worms The worms pass into the columnar epithelium of the small intestine and, in 1–2 days (30 hours), become mature (molts about 4 times) After mating, adult females produce larvae The female is ovo-viviparous. This means that she produces eggs, but doesn't lay them until they have already hatched in her uterus She lays her living larvae within the small intestine beginning the fifth or sixth day after infection

Life Cycle : Parenteral Phase Parenteral phase begins approximately one week after infection and may last several weeks Larvae breaks through the intestinal wall and travel through the lymphatic system to the circulatory system to find a suitable cell Larvae can penetrate any cell, but can only survive in skeletal muscle (sword-like stylet) Within a muscle cell, the worms curl up and direct the cell functioning much as a virus does. The cell is now called a nurse cell complex. Soon, a net of blood vessels surround the nurse cell, providing added nutrition for the larva inside The Nurse cell-parasite complex can live for as long as the host remains alive

Infective first stage larva of Trichinella spiralis in its Nurse cell in muscle tissue. The worm measures 1mm x 36 µm.

Adult T. spiralis in situ

Worm Entering Muscle Cell

Question III What is the only way of getting infected? ~ Ingesting raw or undercooked meat that contains the parasite

Clinical Signs Dysentery due to invasion by adult worms Migrating juveniles cause pain as they invade muscle tissue; there may also be edema (swelling), delirium, cardiac and pulmonary difficulty, pneumonia, nervous disorders, deafness and delayed or lost reflexes Fever can also be caused Many cases are never diagnosed because of the vagueness of the symptoms

Clinical Signs Continued Severe symptoms include: High fever severe muscle pain skin rash headaches swelling of eyelids, face, or extremities

More Clinical Signs Patients may develop neurologic manifestations that rarely appear before the end of the second week of infection and provoke distress. Headache, vertigo and tinnitus, deafness, aphasia, convulsions, and abnormalities related to peripheral reflexes, among others, are frequent complaints or signs found in severely infected individuals. Generally, patients are alert but apathetic, and prolonged insomnia affects their behavior, causing them to become irritable. Other neurologic symptoms such as meningitis, encephalitis, and/or hemiplegia may develop in relation to diffuse damage of brain tissue due to occlusion of arteries or to granulomatous inflammation

eyelids, hands, and feet are a prominent feature of mild symptoms. Splinter hemorrhages & Conjunctivitis Edema of the face, eyelids, hands, and feet are a prominent feature of mild symptoms.

Complications Stillbirths in pregnant women Hearing loss Weight disorders Loss of hair and nails Disturbance of menstruation Muscle stiffness Death may occur from heart failure or central nervous system failure

Diagnosis A blood test or muscle biopsy can identify trichinosis. Stool studies can identify adult worms, with females being about 3 mm long and males about half that size Xenodiagnosis can also be done, where a lab rat is fed with a suspected piece of tissue DNA tests amplified with PCR have found T. spirals. ELISA test

Treatment Symptoms can be treated with aspirin and corticosteroids Thiabendazole can kill adult worms in the intestine; however, there is no treatment that kills the larvae. Immunity for this parasite appears to be lifelong. Neurological symptoms need to be treated with steroids due to inflammation.

Control & Prevention Cook pork thoroughly (also flesh of bear, walrus, wild pigs) Cook all garbage fed to hogs Proper meat handling, ordinary curing and salting of pork products will not kill encysted juveniles Freezing is effective if carried out properly. The freezing requirements differ with the size of the meat. Pieces not exceeding 6 inches in thickness require 20 days at 5ºF, 10 days at -10ºF, 6 days at -20ºF. Larger pieces require longer periods. Quick freezing and storage for 2 days is effective. Cook wild game meat thoroughly. Freezing wild game meats, unlike freezing pork products, even for long periods of time, may not effectively kill all the worms. This is because the species of trichinella that typically infects wild game is more resistant to freezing than the species that infects pigs.

The Centers for Disease Control and Prevention makes the following recommendation: "Curing (salting), drying, smoking, or microwaving meat does not consistently kill infective worms." However, under controlled commercial food processing conditions some of these methods are considered effective by the United States Department of Agriculture. An ELISA for swine trichinellosis is now approved for the certification of pork by the U.S. Department of Agriculture.

Question IV Where do outbreaks occur most frequently? ~ In a community or among family members

References http://animaldiversity.ummz.umich.edu/site/accounts/information/Trichinella_spiralis.html http://www.trichinella.org/ http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/nemas/trichinellaspiralis http://www.phac-aspc.gc.ca/msds-ftss/msds155e.html http://www.dpd.cdc.gov/dpdx/html/Trichinellosis.asp?body=Frames/S-Z/Trichinellosis/body_Trichinellosis_page1.htm http://www.cdc.gov/ncidod/dpd/parasites/trichinosis/factsht_trichinosis.htm http://cmr.asm.org/cgi/reprint/9/1/47