2007 Volume 16 Issue 4 Pages 103-107
The primary factor in developing adult Dirofilaria immitis infection was closely examined in 5 dogs which had not been properly administered prophylactic agents against canine dirofilariasis. The first case was given a tablet formulation of milbemycin oxime from June to August and a tablet formulation of moxidectin in November and December of 2001, but was not treated with any prophylactic in September and October of 2001. The second case had not been treated until August of 2001 and was given a chewable formulation of ivermectin from September to December. In these two cases, improper periods of medication was considered to be an important factor in developing adult D. immitis infection. The third case was given a chewable formulation of ivermectin from June to December of 2003, but the dog had diarrhea when treated in August and September. It was thought that the amount of the active ingredient absorbed was insufficient at those medications due to malfunction of the digestive tract of the dog. The forth case was treated with a spot-on formulation of ivermectin from June to December of 2004. In this case, probably an amount of the active ingredient cutaneously absorbed was not enough, because the dog owner had not administered the formulation by pushing the dog's hair aside to make the medicine reach the skin directly. The fifth case was given a tablet formulation of moxidectin from June to December of 2005. But the dog grew rapidly during this period, so the enough dosages were not continuously administered, because the drug was prescribed based on the body weight at a time in June. In conclusion, it is necessary to take various factors into consideration in prescribing and administering prophylactics against canine dirofilariasis. And it is also necessary to give careful and concrete instructions to dog owners.