L25 People parasites and pets Flashcards
Define Parasite
‘A parasite is an organism living in or on another living organism, obtaining from it part or all of its organic nutrition, commonly exhibiting some degree of adaptive structural modification and potentially causing some degree of damage to its host’
What is commensualism
one species benefits and the other is unharmed
What is mutualism
Mutually beneficial symbiotic, can be essential
What is parasitism
One species benefits, the other is harmed
What is meant by prevalence
The proportion (%) of a population infected,
What is meant by incidence
The frequency of a population acquiring infection in a unit of time
What is meant by intensity
Measure of the number or density of parasites per host
What is morbidity
The level of ill-health or disability among all cases of infection, or among the general population
What is Mortality
The number of deaths in a given time, or the % of deaths among all cases of infection
What are DALYs
Disability Adjusted Life Years
A measure of overall disease burden. Number of healthy years lost to disease, disability or early death
Where do these diseases come from: Ascaris, Schistosomiasis, Malaria, Sleeping sickness
Ascaris is directly transmitted through faecal contamination of soil
Schistosomiasis is snail-borne
Malaria is mosquito-borne
Sleeping sickness is tsetse fly-borne
Types of parasites
Protozoa
Helminths
Arthropods
Types of parasitic protozoa
Amoeboid
Kinetoplastid
Apicomplexa
Types of Helminths
Nemetoda
Platyhelminthes
Types of ectoparasites
Insects (lice and fleas)
Arachnids (ticks)
What is zoonosis
An infection or disease that is transmissible from animals to humans under natural conditions
Toxicara Canis: target organism and how its infected, what it does
Dogs and foxes
infection by ingesting eggs from soil
Invades liver, causes fevers, can impair sight
Toxicara Canis life cycle
Adult females release eggs in faeces
Eggs hatch in stomach releasing larvae
Larvae migrate (lungs, liver, brain)
In dogs, move to small intestine and mature to adult worms
What happens to Toxicara Canis during dog pregnancy
larvae is reawakened
Larvae travel cross placenta to infect pups or migrate into colostrum to infect milk
What is the Echinococcus granulosus’ definitve and intermediate host
Definitive host: dog
Intermediate host: sheep
Echinococcus granulosus cycle in the body
Embryonated egg in feces
Onconosphere hatches; penetrates intestinal wall
Hyatid cyst in various organs
Toxoplasma gondii key features
Protozoan parasite
Zoonotic
Cosmopolitan
Definitive host: cats
What do oocysts develop into to disseminate infection in the host
Tachyzoites
Toxoplasma gondii cycle
Oocysts -> oral ingestion -> Tachyzoites (acute infection) -> Bradyzoites (chronic infection)-> can reactivate
What are the pathological consequences of toxoplasma infection
Cysts in brain (mice loose aversion to cats)
Tachyzoites invade foetus (infection of brain)
What parasites spread lyme disease
Ticks
