University:
University of Alberta
Course:
MMI 133 | Medical Microbiology for Health Care Professionals
Academic year:

2024
Views:

428

Pages:

3
Author:

Ali O

Nematodes (Round) Eggs as infections stage Enterobius Vermicularis (Pinworm) (EV) Life cycle in human Live in large intestine Glue (irritant) eggs at anus Not usually serious Infectious in daycares Ascaris lumbricoides (AL) Live in small intestine of animals eggs in soil very hardy Dioecious Moves to nose and mouth of children Larva as Infectious stage Hookworms Enters intact skin or bare feet Sucks blood in SI (cause anemia) In warm climates Eggs are excreted Anisakis Fish nematodes Rare, accidentally affects humans To prevent you need to heat or blast freeze or cleaning Trichinella spiralis (TS) Ingestion of larvae from undercooked animal Encyst in striated muscle fibers (and heart) Muscle weakness is dominant symptom Difficult to treat Blood hematodes (filaria) Lymphatic filariasis (elephantiasis) ↳ adult worms live in lymph tissue Onchocerciasis ↳ adult worms live in subcutaneous tissue microfilariae (offspring of adult worms) circulate through bloodstream or migrate through subcutaneous tissue transmission by mosquitoes Trematodes (Leaf like) Schistosoma Larvae penetrate intact skin in freshwater ponds Hides from host immune system under a coat of protein acquired from host Reside in the venous plexus of bladder or intestine Eggs cause inflammation 3 types of schistoma: ↳ S. haematobium -inflammation of bladder wall -bladder cancer ↳ S. japonicum -intestinal parasite ↳ S. mansoni -intestinal parasite “Swimmers itch” Caused by duck schistosome Does not enter human circulation Cestodes (tapeworms) Taenia saginata: beef tapeworm Life cycle in humans and cattle Tissue larvae (cysticerci) ingested by humans and mature into adult in intestine Eggs passed in feces Usually mild symptoms Taenia solium: pork tapeworm Life cycle in pigs and humans More dangerous than beef tapeworm (cerebral cysts cause cysticercosis) Person to Person transmission is possible 2 modes of transmission: ↳ eggs: result in hatching of larva in intestine, which then escape and penetrate body tissues,including the brain ↳ larvae: result in adult worm in intestine Echinococcus granulosus: dog tapeworm Humans are dead end hosts Dogs, coyotes, dingoes Larva develops into a hydatid cyst with hundreds of worm parts but cannot form a whole tapeworm in humans Ectoparasites (separate from metazoa) Sarcoptes scabei (Scabies) Finger webs, elbows, armpits, breasts, groin and buttocks Mites burrow into skin, feed, mate, lay eggs in burrow Host defenses cause inflammation around the burrows, intense itching Secondary infections with skin bacteria Other sarcoptes mites to not thrive on humans Phthirus pubis (public lice/crabs) and Pediculus humanus (headlice) Surface dwellers Penetrate skin with mouth, suck blood Female glues eggs to hair shafts Secondary infections when lice feces are crushed into wounds