How They Are Important Flashcards
Parasite
Animal that lives in or on another animal from which it obtains nourishment. The host does not benfit and is often harmed by the relationship
Why parasites concern us
They cause disease which can be fatal, distressing, cause production loss or lead to human disease
Feeding and repro
Most parasites are massive feeders to support R type repro eg human tapeworm (taenia saginata)
Some are K type repro eg warble fly
Sometimes feeding itself is the cause of dis by metabolic disturbance, imm effects or transmission to other pathogens
Parasite normal distrib
Most have low density or no infestation and only a few have very high density infestation so infection prevalence is high but disease prevalence is low
What causes parasite distrib
Variation in host suscept and imm competence
And can also be due to enviro concerns
Which animals is clinical disease normally seen in
Those with Poor immunity or to introduced, not previously exposed animals this leads to the state known as endemic stability
Rules about harm types caused by parasites
Often parasite causes more than one type of harm
There are a wide variety of subcategories as one parasite may cause different subtypes in diff hosts eg toxoplasma cause behavioural disturbance in rodent brains and abortion in sheep repro syst
Pruritic stress/itching harm category
Eg scabies by mites
In pigs causes production loss and in camels causes loss of draught power
Not in contact with nerve endings but still cause intense pruritus med by imm resp (dermal hypersens) to antigens in excretion and dead mite bodies
Similar to contact hypersensitisation
Effector cells eg mast release med with direct effect on nerve endings
Biting nuisance harm type
Eg stable flies
Can cause red prod in dairy cattle as oxytocin released which affects milk let down and some hormones involved in appetite lead to anorexia. Hormones med stress
Acute inflam resp by organ syst to infection harm type
Babesiosis Babesia live in blood Transmitted by ticks Asex repro Destruc of RBC release of proteases and excr into blood (pyrogenic and cause fever)
Physical dam of host tissue and organs
Coccidiosis
Liver fluke
Competition for resources harm
Eg food and metabolites
Helminth and nematode worms in horses
