22. Zoonoses Flashcards
What is zoonois?
any disease or parasite that is transmissible from anims to humans - risk of infection to general public is slight, employment with animals or anim products or those to diagnose animal origin should be more aware
What are 3 questions to ask in regards to a zoonotic pathogen?
how do people get infected
what does the parasite do to people
what would you recommend to prevent human infection with each other these
What is the cutaneous larval migrans or creeping eruption?
From ancylostoma spp (hookwork) and strongyloides stercoralis (dog threadworm)
people infected via L3 skin penetration
Linear tortuous, inflamed and intensely pruritic lesions of skin from penetration/migration thru skin (usually on feet) of infective larval stages (L3)
people infected by walking barefoot on beaches or in parks where dogs have defecated, or by lying on damp contaminated soils or beeches
Strongyloides will eventually migrate to the intestine and mature, canine hookworm will not
prevention: quick removal and safe disposal of feces and wear shoes
What is visceral + ocular larval migrans and toxocariasis
toxocara canis and T. cati - people act as accidental PH and larvae will do somatic migration to cause visceral and/or ocular larval migrans
eggs, containing infectinve L3 larvae, are ingested by a person and the larvae hatch and migrate
people are not normal DH - therefor migration larvae end up in a bit “lost” they may end up in various tissues including muscle, organs, brain, eye = clin signs from nothing to malaie, fever, vague abdominal pain, coughing, granulomatous retinal lesions > blindness
What are neural larval migrans?
baylisascaris procyonis (racoon roundworm)
spread by racoons by exposure to racoon latrines
human ingestion of infective L3 eggs = fatal invasion of brain by larva known as neural larval migrans.
do not keep racoons as pets
What is the ascaris suum?
pig round worm - will happily complete its life cycle in human DH
infected by ingesting egg with L3
lab workers, garden fertilizer, chicken
What is the trichinella spp?
infection by ingestion of muscle tissue cysts containing larvae (carnivore)
larvae freed when cyst wall is digested in stomach and L enter mucosa of SI
Develop to adult, mate, release eggs (adults die soon)
larvae migrate to lymphatics and travel thru portal system to circulation, and to striated muscle
there, enter muscle cell and grow, coiling in cell, form capsule which protects larva
L do not develop further until developed by next host
each host acts as DH then IH w/ larvae in muscle tissue
What is trichinella spiralis? T. nativa and other freeze resistant species
parasite associated w/ undercooked pork - freeze and cook properly, smoking and drying (jerky) will not kill parasite
species now only rarely seen in Canada - commercial pork herd is considered trichinella free
Normally infected by WILD meat like bear or walrus (t. nativa and other species)
in wildlife and domestic animal hosts there are no detectable symptoms
in people, can produce fatal symptoms
What are the clinical findings of trichinella spp?
in people: prod a very serious illness w/ symptoms including diarrhea, skin rash, fever, abdominal pain, malaise, myalgia, periorbital oedema, leg swelling, vomiting and even death
How do we dx trichinella sp??
may be suspicious if hx of eating undercooked meat, biopsy of muscle tissue
ELISA (serology) can detect anti-trichinella Ab’s (but not until several weeks after infection)
tissue digestion ( muscle of domestic and wild hosts) - surveys of wildlife can tell us where the parasite is present and what % of a population is infected
What is diphyllobothriasis?
diphyllobothrium latum (broad fish tapeworm)
people are DH and infected by eating plerocercoids from undercooked fish
People treated have elimed several hundred feet of tapeworm (numerous adults infecting an individual)
Can be up to 12m long and can live 10yrs in host
rarely symptomatic but reports of anemia as parasite selectively uptakes VitB12
What is the dipylidiasis?
dipilidiu caninum (cucumber seed tapeworm)
humans infected by ingesting an arthropod (flea or maybe a louse) containing a cystercercoid
infected individuals may show nocturnal irritability, anorexia, weight loss - particularly in children
What might cause cystic hydatid disease in humans?
echinococcus canadensis (e.granulosus)
single lg cyst, covered by a fibrous capsule
people act as IH in this infection after ingesting an egg containing a hexacanth larvae
in people cysts can get as lg as 50cm diameter and contain 16L of fluid
if they rupture, cyst fluid can cause severe anaphylaxis and death
in human host, cyst develops mainly he liver or lung but possibly brain nd does its damage as a space occupying lesion
What migth cause a alveolar hydatid disease/
echinococcus multilocularis
people act as the IH in this infection after ingesting an egg containing a hexacanth larvae
produces a multilocular cyst composted of multiple, thin-walled vesicles, these an grow in place, usually the liver, and they may expand in a highly invasive manner
may also metastasize to other places in body including lungs and brain
Mortality of 50-70% in people
this is emerging infection in w. cad
What is the beef tapeworm?
taenia saginata (cystercerus bovis)
w. T.saginata people act ONLY as the DH and acquire this infection when ingesting undercooked beef containing cystercerci
relatively harmless infection
parasite observed occasionally in Cad, most often detected in cattle @ slaughter cysts in muscle
most human cases acquired oversea
a pos anim usually condemned and removed from human food chain - also traced back and quarantine of farm of origin, and an investigation of extent of problem on farm and attempts to ID source of infection, often very difficult bc promiscuous defecation
