title: Ivermectin and milbemycin oxime in experimental adult heartworm (Dirofilaria immitis) infection of dogs.
abstract: BACKGROUND
  The US Food and Drug Administration reports an increase in the frequency of reports of lack of effectiveness claims for heartworm (HW) prevention products.
  
  
  OBJECTIVE
  At their labeled doses, single doses of commercially available HW prevention products are not completely effective against all field isolates of HW.
  
  
  METHODS
  Forty-two HW-free dogs experimentally inoculated with a recent HW field isolate.
  
  
  METHODS
  Placebo-controlled, blinded laboratory clinical trial. Dogs randomly allocated to 1 of 3 treatment groups with 14 dogs per group. Groups were untreated control or p.o. dosed with milbemycin oxime (MBO) or ivermectin (IVM). Dogs were inoculated with 50 HW third stage larvae 30 days before dosing and necropsy was performed on Day 123 after treatment to enumerate adult HW.
  
  
  RESULTS
  Thirteen of 14 control dogs had adult HW detected at necropsy with a geometric mean worm count of 22.3. One HW was found in 1 dog in each of the MBO and IVM treatment groups.
  
  
  CONCLUSIONS
  Two currently approved macrocyclic lactone HW preventives used at their labeled dose rates were <100% effective against a recent HW field isolate, supporting the hypothesis that the effectiveness of a single dose of these preventives can vary. This is important in guiding clients on expectations of product effectiveness.
authors.affiliation: Elanco Animal Health Research and Development, a Division of Eli Lilly and Company, Greenfield, IN 46140, USA. snyder_daniel_e@Lilly.com
authors.forename: D E
authors.initials: DE
authors.lastname: Snyder
authors.forename: S
authors.initials: S
authors.lastname: Wiseman
authors.forename: L R
authors.initials: LR
authors.lastname: Cruthers
authors.forename: R L
authors.initials: RL
authors.lastname: Slone
mesh_terms: D000818:Animals; D000977:Antiparasitic Agents / Q000008:administration & dosage*; D004183:Dirofilaria immitis / Q000254:growth & development*; D004184:Dirofilariasis / Q000469:parasitology / Q000517:prevention & control*; D004283:Dog Diseases / Q000469:parasitology / Q000517:prevention & control*; D004285:Dogs; D005260:Female; D007559:Ivermectin / Q000008:administration & dosage*; D018942:Macrolides / Q000008:administration & dosage*; D008297:Male
chemical_list: D000977:Antiparasitic Agents; D018942:Macrolides; C078973:milbemycin oxime; D007559:Ivermectin