2. DEFINITIONTHE ABILITY OF A GIVEN TICKPOPULATION TO SURVIVE
APREVIOUSLY EFFECTIVELETHAL CONCENTRATION OFPESTICIDE AFTER
REPEATEDTREATMENTS. Presentation title Date 3. Resistance
progression start Presentation title Date 4. Totally
susceptibleTICK PopulationGenetically UniformAndA lovely Fairy
Tale.This does not Happen!1 RJ2001 5. In reality any open
tickpopulation looks like this.2Nave to new dipResistant to new
dipResistant to old dipResistant to crop sprayResistant to old
andnew dipRJ2001 6. We now treat withthe New Dip andAssume:90 %
Kill Rate.This is what weare left with.3RJ2001 7. The ticks
multiplyand we now have aPopulation 38%resistant to new dipAndonly
23 % resistantto the old dipBut we have6% resistanceto both
dips.4RJ2001 8. We continue to use theNew dip with90% efficiency on
theSusceptible populationAND end up with thefollowing..At this
point youmay notice that ..you have aPROBLEM5RJ2001 9. The ticks
multiplyand we now have aPopulation 83%Resistant to new dipAnd only
17%resistant to the old dip6And 13%resistance toBoth DipsRJ2001 10.
We continue treatingWith the NEW dipand we now have aPopulation
97%Resistant to new dipAnd only 14%resistant to the old dip.7BUTTHE
NEW DIPIS NO LONGEREFFECTIVERJ2001 11. So now we changeback to the
old dipWhich we assumewill kill 90% of allsusceptible ticks.
Butwith only 77%Efficacy due to thepurple populationresistant to
both dips8RJ2001 12. 9The ticks multiplyand we now have :43%
Populationsusceptibleto old dip, but 56 %now resistant toboth
dipsRJ2001 13. Prolific breeders/short generation period/single
host = Potential Resistance 14. MECHANISMS OF RESISTANCE iGENETIC:
The initial frequency of a dominant Resistant gene in the
populationThe higher the ratio of resistance factor (Rf) in the
population thequicker it will manifest as control breakdown.
Dilution factors due to constant migration of ticks into the
populationIn an open population the dilution or concentration
factor willaccelerate or retard resistance The robustness of the
resistant strains vs susceptible strainsDoes the presence of a
number of Resistant genes give the tick anadditional advantage over
susceptible ticks? Presentation title Date 15. MECHANISMS OF
RESISTANCE iiBIOLOGICAL Generation time and reproductive rateTicks
with multiple generations per year and high reproductive rates
havegreater probability of developing resistance Host selection and
life cycle profile. Single host ticks develop resistance earlier as
all the parasite stages are ona single treated host- The dairy cow.
MigrationWhere you have a closed dairy farm a greater % of the
population is exposedto the acaracide with faster selection for
resistant survivor populations Presentation title Date 16.
MECHANISMS OF RESISTANCE iiBiological continued Ratio of on/off
host (% of the parasite on the host at any one time)In a closed
concentrated compound (Intensive dairy farm) a greater % ofthe tick
population is exposed to the pesticide and selection pressure is
high. Time of application/season/diurnal/Larvae, Nymph and Adult
susceptibility differLower air temperature = lower metabolic rates
= slower effectPre shedding larvae/nymphs have a double chitin
layer = barrierGenerally all fully engorged ticks drop off before
10 am = nextgeneration. Presentation title Date 17. MECHANISMS OF
RESISTANCE iiiOPERATIONAL ChemicalNot all chemicals in the same
group are equally effective.The same active ingredient in a
different formulation .The same active ingredient in a similar
formulation may have agreater or lesser killing effect due to the
chemical process. ApplicationHave I mixed and used the acaracide at
the correct strengthand used the recommended volume per animal.Is
my spray race/plunge dip calibrated and agitated correctly.Are all
the nozzels working and delivering at the recommendedpressure?
Presentation title Date 18. Monitor to ManageQUANTIFICATION OF
RESISTANCE IN VIVO tests Stall test IN VITRO tests Larval Packet
Test (LPT) Engorged Adult Female Immersion Test (EAFT) Egg Laying
Test (not standardized!) Presentation title Date 19. Egg laying
test 20. Monitor to Manage LPT100 fully engorged females
collectedSent to designated laboratoryThese will be incubatedTheir
eggs are allowed to hatch to larvaeLarvae are tested on ~day 4
Against at least 3 Active Ingredients Against at least 3
concentrations A report is compiled with recommendationsThis takes
8-12 weeks!!!! Presentation title Date 21. RESULTS OF A larval
packet testAmitraz needs to be rested: Either use an OP or SP or
DDX Presentation title Date 22. So what do we do while we wait for
the test???We do not have a key to turn the ticksoff!!!!i) We can
change active ingredient and hope it works (History)ii) We can use
a combination acaracide if registered (pour on is easiest)iii)
Farmers used to inject a Macrocyclic Lactones. There is now
resistance incoastal areas of South Africa. (does not work on multi
host ticks)iv) We can, and do recommend in RSA to use a combination
TGR/FlumethrinPO.v) WHY? A) Controls all ticksB) Cleans up the
pastures (vacuum cleaner effect)C) Indicated reversal of resistance
progression Presentation title Date 23. Monitor to ManageChopping
and changing Brands and active ingredients
..maybecounterproductive.Recommended actions Monitor the tick
activity by scouting herds before and after treatment Determine the
resistance profile and pesticide effect by adultimmersion tests and
Larval packet tests. Monitoring the tick profile within a
population bi-annually will prolongthe effective lifeof the
chemicals we have at our disposal.Consult local experts on the
possibility of a realisticIntegrated Pest Management Programme
Presentation title Date 24. Thank You Kindly Presentation title
Date
