Internal Parasite Control

1. Internal Parasite Control DL Step, DVM, DACVIM Elisabeth Giedt, DVM, MBA Oklahoma State University Veterinary Medical Hospital Stillwater, OK October 2015

2. Internal Parasite Control Programs

3. Common Concerns or Questions WHICH DRUG---What is the best dewormer to use ? WHEN---When is the best time of the year to deworm my cattle ?

4. Clinical and Subclinical Parasitism • Clinical • Low BCS • Anemia • Rough hair coat • Diarrhea • Bottle jaw • death • Subclinical • Suppression of immune system • Reduced weight gain • Reduced conception rate • Reduced milk production

5. Best Advice Programs MUST be customized Work closely with your veterinarian

6. Goals • Understand the biology of the parasites (worms) • Discuss classes of dewormer medications • Discuss types of deworming programs • Answer commonly asked questions • Stimulate Discussion

7. 3 Stages of Parasite Life Cycle • Developmental stage/ free living (outside animal) • Prepatent stage (time from ingestion until capable of producing viable eggs) • may consider as a “pre-adult” stage of the worm • Patent stage (also known as adult stage)

8. INSIDE HOST L4 = 4th stage larvae (inhibition may occur) L5 = 5th stage larvae OUTSIDE HOSTL1 = 1st stage larvae L2 = 2nd stage larvae L3 = 3rd stage larvae

9. Developmental/ Free Living Stage • Outside the host • Egg, 3 larval stages—L1, L2, L3 • Largest portion of population • L3 only infective form of parasite • L3 able to survive over winter • L3 migrates from manure pat to blade of grass to facilitate ingestion by grazing cattle

10. Developmental Stage(cont’d) • L3 can survive freezing conditions • Some eggs and L3 can survive dry, drought conditions if protected inside manure pat

11. “Pre-Adult” Stage (Prepatent Stage) • L3 ingested  digestive tract for further development • 4th stage larvae (L4) • If external conditions favor further development  next stage –> L5 • If external conditions are unfavorable  inhibition-hypobiosis may occur • What advantage is hypobiosis to the parasite?

12. “Pre-Adult” Stage (cont’d) • Why is hypobiosis important to farmer/rancher ? • Arrested or inhibited development (hypobiosis) • Damages digestive tract • Affects future production • Hypobiotic parasites may be unaffected by certain dewormers • 5th stage larvae (L5) or young adult

13. Adult Worms (Patent Stage) • Mature adults • Male & female mate • Goal is to produce viable fertile eggs-pass on genetic information to next generation

14. Duration of eggs laid -> ingest and mature-> new generation • Adult cattle without arrested stage 4-6 weeks • Young cattle (<2years) without arrested stage 3-4 weeks • With arrested stages - can add 12-16 weeks depending on climate

15. Suitable Environment for Completion of Life Cycle • Moisture • dew • humidity • rainfall • Temperature 45-85 degrees F • Pasture

16. Environmental Conditions Unsuitable for Completion of Life Cycle • Cold • High temperatures with DRY conditions • Feedlot, drylotoperations • How do parasites respond to this? • some eggs, L2 and L3 may dry out and die if exposed • some protected inside manure pat • L3 has protective coat to survive cold • arrest development inside host-hypobiosis

17. Emerge from Hypobiosis / Arrested Development  complete life cycle • Conditions for survival improve • Fall after hot summer • Spring after cold winter • Emergence from arrested state…. • affect on host cattle • “flood” pasture with infective larvae to find a new home

18. Immunity to Parasites • Develops over time in most cattle—adults may not have clinical parasitism • BUT adults shed parasites --SOURCE of eggs-- that cause problems in young animals • Adults contaminate pastures

19. Dewormer Medications • Vary in the spectrum of parasites affected • Vary in ability to kill hypobiotic/arrested larvae in gut wall • Vary in route of administration • Vary in safety with pregnant animals • Vary in residual killing activity = the period of time after a product has been administered to an animal that will still provide killing action to the parasite should the animal ingest infective larvae

20. Classes of Dewormer Medications Marketed as generics and under trade names Macrocyclic Lactones * based on mode of action against parasites NOT which parasite(s) are killed

21. Same drug----- different names

22. Resistance to Dewormers • Resistant parasites are not killed by dewormer medication at same rate as susceptible population • Resistance can be passed from one generation of parasite to next • Newer focus…Parasite MANGEMENT not parasite elimination

23. Deworming Programs (3 types) • Therapeutic program • Tactical program • Strategic program Remember that as beef producers the goal is to produce the most possible pounds of calf per cow unit and per acre of resources

24. Therapeutic Program • Treat clinical disease • Limited effect on pasture contamination

25. Tactical Program • Treat or administer medicine when it is convenient for the producer • Limited effect on minimizing pasture contamination

26. Strategic Program • Definition: program to allow young cattle to graze “parasite safe” pastures for approximately 90 days • Early in the grazing period • sometimes referred to as turn-out

27. How can we assess worm burdens? • Necropsy • Fecal Float • Fecal egg counts • Identify specific species of parasite --DNA

28. Fecal Egg Counts • Sample 20% of herd • Monitor pasture contamination • Select animals for ability to resist parasites • Limitations:

29. Determining the Efficacy of Dewormers (DW) • Measure FECRT = fecal egg count reduction test • 95-100 % • small number resistant worms, or worms that survive • 80-95% • treatment effective but resistance increasing • < 80% • production losses become apparent as effectiveness of DW moves closer to zero • anthelmintic failure  animals die

30. Best Practices for Parasite control • Dose based on weight • Proper product storage • Follow expiration dates • Proper product choice • Dewormers cannot overcome bad management! • Follow sound biosecurity practices • isolate new arrivals • Avoid overgrazing and overstocking

31. Goal of Parasite Control for Pastured Animals • Parasite “safe” pastures NOT parasite free • Parasite “safe”= adequate grazing with reduced number of infective L3 larvae • Practice good pasture management • Provide adequate acres per animal • Utilize dewormers as recommended by your veterinarian

32. Adult Cows • Individual performance benefit in adult animals is difficult to justify • HOWEVER, adults grazing with young stock contribute to pasture contamination • Deworm adult cattle to reduce challenge to young stock

33. Adult Cows(cont’d) • If dewormed previous fall or winter & likelihood of acquiring infection is minimal, then assume adults fairly clean at turn out • If deworming history is unknown or adults probably infected, deworm at turn out

34. Adult Cows(cont’d) • Deworm 4 – 6 weeks later (if used medicine with no residual killing activity) • 6 weeks plus 6 weeks = approx 90 days • Generally deworm after grazing (late fall, winter)

35. Young Cattle • How early should calves be dewormed? • RuleOfThumb: • 2 months of age or calves that weigh ≥ 200 pounds • OR……

36. Young Cattle (cont’d) • If calves are older than 2 months or 200 pounds at turn out, then assume the calves will start to acquire infective larvae day 1 • Prepatent period 3 – 4 weeks • Time from ingestion of L3 to shedding eggs • Need to be administered a dewormer medication 3 – 4 weeks

37. Young Cattle (cont’d) • If medicine does not have any residual killing activity, calves will need to be dewormed again at 3 – 4 weeks • AND at another 3 – 4 weeks • Provides approximately 90 days of grazing • If the medicine has residual activity, then add the residual time to the 3 – 4 week intervals

38. Additional Methods to Control Parasites • Does dragging pastures help with parasite control ? • Does burning pastures help with parasite control? • Does mowing pastures …..? • Can using poultry litter as fertilizer spread parasites from poultry to cattle? • Should we rotate classes of dewormers and how often?

39. Future Approaches to Parasite Control • Pasture rotational grazing • Rotate grazing species—horses, sheep/goats • Hay meadows • Tillage • Genetic selection for parasite “hardy” animals • Select specific individuals for treatment

41. Questions ?

42. Liver Flukes • Clinical • Loss of condition • Anemia • Bottle jaw • Death • Liver condemnation at slaughter • Predispose to C. haemolyticum Red Water • Subclinical • Reduce feed efficiency • Reduce weight gain • Reduce reproductive rates • Reduce immune response • Lighter calves at weaning • Reduced milk production

43. Distribution Liver Flukes • GI internal parasites—universal across US • Liver Flukes • Requires environment with aquatic snail

44. 4-6 months to complete life cycle

45. Treatment Liver Flukes • Timing of Treatment …CRITICAL to control population • Varies on geographic area • Drug/product • Some kill both adults and immature forms • Management • Restrict access to snail infested areas