2.7.3. Muscle Parasites Flashcards
What does DALYs stand for?
Disability Adjusted Life Years
Used when looking at global health impact
Define: Phoresis
Traveling together, hitching a ride, no interdependency
Define: Commensalism
One partner benefits, the other isn’t harmed
Define: Parasitism
Generally, one partner is harmed
What is parasitology?
It should include all pathogenic nacteria, fungi, etc.
Historically, however, it is restricted to protozoan and metazoan invaders:
Protozoa (malaria)
Nematodes (round worm)
Platyhelminthes (flat worm)
Arthropods (tics)
Trichinella spiralis
Globally, one of the most prevalent and clinically important parasites
8-12 species complex
What are two important life cycles in regards to parasites?
- Domestic Cycle (pigs and rat/transmission from meat scraps)
- Sylvatic Cycle (in the forrest/scavenging)
What happens upon infection with Trichinella?
- Larva forms cyst in muscle of many hosts (usually after eating porks)
- From larvae to adult in 30-40 hours
- Mate and producing larvae in under 5 days
- Live until the T cell response evicts them (generally about a month)
Where are Trichinella larvae deposited?
In the mucosa, after which they enter the villous lymphatics and migrate (5-6 microM wide, so they can traverse capillaries)
Nurse cell pathophysiology
- Larva penetrates myocytes, coil in a spiral and modify myosyncitium to become a nurse cell
- Secrete nuclear regulatory factors that alter the way the myocyte behaves
- Increased host nuclear division followed by mitochondrial damage (by secreting VEGF)
- Loss of muscle protein (actin/myosin) complete by 8 days
- Affects Collage Types IV and VI
When does angiogenesis begin and end?
About Day 12 after the larva invades the muscle cell and ceases by Day 26
What is a common symptomatic presentation of parasites?
Facial edema (specifically, circumorbital)
Other clinical signs of Trichinella
Fever, Muscle soreness/pain, GI symptoms, Facial edema, Eosinophilia
Sublingual, retinal and subconjunctival hemorrhages
What do people die from in regards to Trichinella?
Myocarditis, encephalitis, pneumonitis
Laboratory signs of Trichinella
Eosinophilia, Demonstration of larvae in muscle biopsies, Trichinella-specific antibody response
Treatment for Trichinella
Corticosteroids may be life-saving, but they permit longer adult infection
Mebendazole
Albendazole
Why does Trichinella show up as a serious life threatening disease in the “clean world?”
Because second and future infections are typically self-limiting (people in Africa were exposed as kids and are immune)
What do you give a pregnant woman with Trichinella?
Pyrantel (only effective in the gut)
Prevention and Control of Trichinella
Food for pigs is cooked (by law)
Uncooked pork frozen at -15C for 14 days
Public awareness of the dangers of undercooked pork
Controlling pig environments to avoid rodents
What is Taenia solium?
The pork tapeworm: an intestinal cestode parasite that releases millions of eggs
Why is Taenia solium bad?
Two types:
Taeniasis (occurs from ingestion the larval form and is generally harmless)
Cysticercosis, the bad type, occurs when larval eggs are ingested
-Skin, muscle, and CNS are affected
What is sarcocystis?
Protozoa that creates muscle-dwelling cysts (people usually do not know that they have it)
Will see “spotty” soft tissue radiographically
Who usually gets toxoplasma?
Pregnant women, kids, and the immunosuppressed
Emerging parasites of AIDS
Microsporidians
Apicomplexans
What are microsporidians
Intracellular parasite, complex, near to fungi with pronounced gene reduction
Types of microsporidians
Trachipleistophora hominis & anthropopthera (causes myositis in AIDS patients)
Anncaliia vescicularum
Encephalitozoon spp.
Types of apicomplexans
Toxoplasma, sarcocystis, and other coccidiosis
What is dracunculiasis?
Infection by the guinea worm (aka guinea worm disease/GWD)
A person becomes infected when they drink water that contains water fleas infected with guinea worm larvae
What is the progression of dracunculiasis?
Initially there are no symptoms.
One year later, the person develops a painful burning feeling as the female worm forms a blister in the skin, usually on the lower limb.
The worm then comes out of the skin over a few weeks.
It is very uncommon for the disease to cause death
What is used to treat neurocysticercosis?
Albendazole
What is used to treat flatworm infection?
Praziquantel (effective against everything but neurocysticercosis)
How do you typically get toxoplasma gondii
Consumption of undercooked meat containing cysts or ingestion of cysts from cat feces
Why are HIV patients at risk for toxoplasma gondii
Can develop into a severe disease:
encephalitis and brain abscesses due to cyst formation in the tissue
Clinically, what due brain abscesses appear as on imaging?
Multiple enhancing lesions
Classic triad of TORCH infections (caused by toxoplasma gondii)
Chorioretinitis, hydrocephalus, and intracranial calcification
What is used to treat protozoal infections?
Pyrimethamine
How does pyrimethamine work?
Interferes with tetrahydrofolic acid synthesis and by inhibiting the enzyme dihydrofolate reductase (necessary for DNA and RNA synthesis)
What is used in combination with pyrimethamine to treat toxoplasmosis?
Sulfadiazine
