Control of Parasites Flashcards
what are antiparasitic chemicals?
types of antimicrobials with crossover with antibacterial and antifungal chemical agents
what do antiparasitic chemicals do? (3)
- interfere with metabolism
- interfere with reproduction
- interfere with growth of parasitic agents
what do antinematode agents specifically do?
affect adult reproduction so eggs can’t hatch and there are no larvae to continue the cycle
what is the risk of using antiparasitic agents and why?
they have low selective toxicity because the eukaryotic parasite cells are very similar to our own eukaryotic cells, so there are extensive side effects
what are the main kinds of antiprotozoals?
coccidiostats
what do coccidostats work against? (coccidia types)
eimeria and isospora!!
what are the 2 groups of coccidiostats?
- polyetherionophore antibiotics: like monensin
2. nonpolyetherionophore antibiotics/synthetics/chemicals
what do polyetherionophores do?
target ion channels to disrupt movement of ions across cell membranes, leading to an osmotic pressure imbalance that causes coccidia to die
what is standard practice to avoid resistance to coccidiostats?
rotate between polyetherionophores and nonpolyetherionophores
what Kind of effect does monensin, a polyetherionophore, have? how?
increases permeability in coccidia cell membranes to create an antibacterial effect
in what 4 animals is monensin widely used preventatively?
- rabbits
- poultry
- swine
- ruminants
how is monensin used in the US? why?
as a feed additive as a promotor of growth and feed conversion efficiency; the antibacterial effect leads to more efficient digestion
how is monensin used in the EU?
only in poultry and rabbits where coccidiosis is systemic/widespread problem
in what animals in monensin highly toxic?
horses
what 2 things are countries trying to figure out with monensin? answer those questions
- is monensin absorbed in meat/does it enter food? research says no because it can’t get inside of cells, can only target free-living parasites
- is coccidia becoming resistant to monensin? it IS becoming an issue, so we have to be very careful in our usage (@US)
where was most of the control of ectoparasites developed from?
pesticides on crops
what are the 2 types of ectoparasite situations that determine how we treat it? tell how treat
- parasites that live permanently in the host; we can treat the host directly
- parasites that have only one life stage in the host; need to combine control of parasites and environment
list and describe 3 methods of control of ectoparasites
- biological control: used a lot now in crop to decrease pesticide use, like lady bugs eating parasites
- off-host control: fumigate the area to kill eggs and larvae, here you can use pesiticides since not in direct contact with living host
- insect growth retardants: block growth hormone of insects/parasites, inhibiting their development
why are insect growth retardants completely safe to use on animals?
because animals use a different mechanism/hormone to grow, so no effect
what are the 3 GENERAL classes of antihelmintics?
- benzimidazoles
- imidazothiazoles
- macrolides, like ivermectin
what is the problem with the fact that we only have three very general classes of antihelmintics?
drugs utulize similar mechanisms within each class, so resistance to one drug in the class by a parasite indicates likely resistance to all drugs in that class; the classes themselves are also all very similar, so resistance is a HUGE issue
what are the 4 modes of action of antihelmintics?
- inhibit tubulin polymerization, a structural/cytoskeleton protein that inhibition of leads to noviable cells
- uncouple oxidative phosphorylation, so no energy production
- inhibit enzymes in glycolytic pathways, so no energy production
- neuromuscular coordinators, so paralyze parasite basically
what is antiparasitic resistance?
the ability of parasites to survive doses of drugs that would normally kill parasites of the same species and life stage
what happens reproductively when parasites mutate and develop resistance?
they produce eggs that are also resistant
what does every exposure of an antiparasitic, especially antihelmintics, do?
exerts some selection pressure for resistance development
what aare the 3 main goals in determining deworming strategies for livestock?
- reduce the chance of developing resistant parasites
- decrease operational expenses for livestock producers (antiparasitics are expensive)
- decrease use of drugs in food animals
how do you avoid parasitic resistance?
reduce exposure of anthelmintics to parasites and minimize the frequency of use
what is the “golden rule” followed when determining a deworming strategy for livestock?
in a herd, 20% of animals will shed 80% of the parasite load
how do livestock producers use the 20/80 rule when developing a treatment strategy?
don’t have to treat entire herd, can use fecals (inexpensive) to find individual shedders and treat just them instead
what are deworming protocols for livestock based on? (4)
type, location (geography and seasons), herd, and individual animals of an operation
what do livestock producers in the southeast US have to do concering parasites?
manage parasites year round
describe deworming strategies in equines (3)
- moved away from the use of a rotational deworming every few weeks to just treating individuals
- use fecal egg counts to determine which horses have a high enough parasite load to treat (lost the battle)
- fecal egg counts above 500 should be treated based on species of eggs present
give some general techniques (4) of parasite management in equines
- clean and dispose of manure in the pasture
- rotate pastures
- keep housing/pasture density low
- remove bot fly eggs from hair to prevent ingestion
describe the 2 types of deworming strategies in small ruminants
- FAMACHA scoring: eye mucosal inspection, tells anemia levels; indicates blood sucking (Haemonchus contortus parasite)
- fecal egg count gives more specific recommendations and tells species present beyond blood sucker
in the southeast US, what 2 parasites are of economic importance in small ruminants? fancy and common names please
- Haemonchus contortus: barber pole worms
2. Ostertagia circumcinta: brown stomach worm
how are cattle deworming strategies different from equines and small ruminants?
is treated by management category, not by individual animal
what “most likely to be affected” groups of cattle are dewormed? (3)
- nursing calves
- stockers (5-11 months of age)
- replacement heifers
all under 1 year old
when does cattle immunity to worms develop?
1 year after weaning
cattle producers use stratgic deworming programs with 4 core production aspects; what are they?
- time of year grazing begins: if pasture freezes during winter, deworm before cows go out to keep pature parasite free
- age/category
- type of operations grazing system
- grazing history of parasites: 6 month rule
what is the 6 month rule concerning parasites and pastures?
if no animals have been on a pasture for over 6 months, it’s probably parasite free; if animals have been there in the last six months, parasites are likely still there
when do you deworm weanling cattle? (4)
- their first grazing season
- at weaning and anytime moved to a new pasture
- when 6 month rule indicates pasture could have parasites
- when stocking density is high
what is rotational grazing?
only a portion of the pasture is grazed at a time while the remainder of the pasture “rests,” allows free forms of parasites (eggs and oocysts) to be exposed to the environment and die before closing the cycle
what is important to know when using rotational grazing?
the life cycle of the main parasites found in your pastures/animals
