Strategic use of ivermectin during pregnancy to control Toxocara canis in greyhound puppies

Twenty-one greyhound bitches were bred (Day 0) and housed throughout their pregnancies on three greyhound breeding farms in Kansas. These dogs were as signed randomly to one of four treatment groups. Group A dogs (6) were give n ivermectin subcutaneously (300 mu g/kg) on Day 0 (the first day the dogs were bred), and Days 30 and 60 of gestation. Group B dogs (6) were given iv ermectin (300 mu g/kg SQ) on Day 42. Group C dogs (3) were given ivermectin (300 mu g/kg SQ) on Days 0, 30, and 60 plus 10 days after whelping. Group D dogs (6) served as controls and received no anthelmintic. Bitches and pup pies were moved to the university on the day after birth and were maintaine d inside far 28 days. Weekly quantitative fecal exams were done on the bitc hes during this time. The puppies were euthanized humanely at 28 days of ag e. Intestinal parasites were recovered, identified, counted, sexed, and pre served in either 10% formalin or frozen at -70 degrees C. The geometric mea n numbers of adult Toxocara canis in the small intestines for Group A puppi es (n = 40) were 2.8, 8.5 for Group B puppies (n = 39), and 29.7 for Group D puppies (n = 28). No adults were found in the Group C puppies (n = 15). T he geometric mean eggs per gram of feces from the pups in group A, B, and D were 1.3, 704, and 27, 134, respectively. No eggs were recovered from the Group C pups. The strategic use of ivermectin at 300 mu g/kg in greyhound b itches on Days 0, 30, and 60 of gestation reduced the worm burden carried b y the puppies by 90% and the actual number of eggs passed into the environm ent by 99.8%. The same dose on day 42 reduced the worm burden by 71.4% and the number of eggs passed into the environment by 97.4%. This dose given on days 0, 30, and 60 plus 10 days postwhelping, reduced the worm burden by 1 00%, and no eggs were passed into the environment. (C) 1999 Elsevier Scienc e B.V. All rights reserved.