Introduction to Course Flashcards
Why parasitology?
- heavy representation: 30% OF EUKARYOTES ARE PARASITIC! (60% of nematodes, 40% of insects)
- many relevant diseases of animals & humans
- 50% CLINIC PROFITS from dispensing fees, HALF OF THESE ARE FROM PARASITICIDES
What can parasites affect?
- clinical disease
- sub-clinical disease / reduced production
- aesthetics / human animal bond
- animal welfare
- public health
- money
How productive are parasites?
very
- single female of H. contortus (barber’s pole worm) can produce up to 10,000 eggs/day
- it can suck up to 0.05 mL of blood per day (1000 female = 500ML)
- average 1mo lamb: 12kg = 50mL/kg = 600 mL
What can parasites survive?
harsh conditions
- Trichinella - case in US after eating undercooked SK bear meat
- meat was frozen for 45 days & they still got infected
What can parasites be resistant to?
- parasites can develop resistance to drugs used to treat them (ex: malaria (Plasmodium genus), Ru nematodes, Ancylostoma in Ca
Who can parasites cause financial losses to?
Industry & small-scale producers
- production losses in cattle: 74 million pounds per year in UK (exclusive of veterinary car)
- largest animal health cost in Australian sheep industry ($11/ewe)
- most prevalent disease reported by US sheep farmers
What can parasites control?
Brains
- Dicrocoelium dendriticum (lancet liver fluke) is a parasitic worm that can manipulate ants into-zombie-like behaviour, climbing to the top of grass stalks & exposing themselves to the herbivore host
what is symbiosis?
Relationship btwn two organisms in close association with each other
What is mutualism?
- relationship btwn two organisms where both benefit (Ex: bacteria inside the rumen)
What is commensalism?
- relationship btwn two organisms where one organism benefits and the other doesn’t benefit but also isnt harmed (ex: amoeba inside the cecum/colon of cattle & sheep)
What is parasitism?
- relationship btwn two organisms where one benefits and the other is harmed
What is the definition of parasitism?
an ecological relationship where the parasite:
- depends on the host for survival & benefits from the host
- has negative effects on the host
- has greater fecundity than the host
- has an over-dispersed host distribution
What are endoparasites?
internal, causing infections
What are ectoparasites?
external, causing infestations
What kind of distribution do parasites have?
overdispersed distribution
- a lot of hosts have zero or a few parasites while a few hosts have
a lot of parasites (20:80 rule)
Why can an overdispersed distribution of parasites be a challenge?
it can be challenging to test for in a herd or flock
How do hosts differ?
- age, immune status, sex, size, genetics, resistance/resilience, behaviour, metabolism (insect attractants!), clinical presentation
What 3 things do you need for parasitism?
environment, hosts, parasites
What is the infective stage?
life cycle stage infective (can cause disease in) for host
What is the shed stage?
stages that are passed by the host
What is pre-patent period (PPP)?
time btwn infection & shedding of the next generation of parasites
What is the patent period (patency)?
period of shedding
What is prevalence?
proportion of infected hosts (like 1 out of 10)
What is the intensity?
the number of parasites per host (often expressed by proxy of fecal egg counts)
