Therapeutic efficacy of milbemycin oxime/praziquantel oral formulation (Milbemax®) against Thelazia callipaeda in naturally infested dogs and cats

Background: Over the last few decades, canine and feline thelaziosis caused by Thelazia callipaeda eye worms has gained the attention of the veterinary community due to the spread of this ocular infestation in geographical areas previously regarded as non endemic. The therapeutic efficacy of milbemycin oxime/praziquantel tablets (Milbemax (R)) against T. callipaeda was tested in naturally infested dogs and cats. Methods: From January 2009 to July 2011 a placebo controlled and randomized field study was conducted in T. callipaeda endemic areas of Switzerland (CH) and Italy (ITA) involving client-owned animals. Dogs (n = 56) and cats (n = 31) were physically examined at enrolment Day 0 (D0) and twice afterwards (D7 and D14). Infested animals were orally treated with Milbemax (R) or with placebo tablets on D0 and, if an animal was found still infested with T. callipaeda, also on D7. On D14 nematodes were flushed from the conjunctiva, identified and counted. Results: Out of 56 dogs, 43 were included in the statistical analysis, whereas 13 were excluded because the products under investigation were not administered with food, as required by the label. On D7 and D14, 72.7% and 90.9% of treated dogs were eye worm free, whereas in the placebo group 95.2% and 76.2% still harbored nematodes, resulting in a mean percentage worm count reduction for the Milbemax (R) group of 86.1% and 96.8%, respectively. Both results were significantly higher (p = 0.0001) than the placebo group. Out of the 31 cats included in the study at D7 and D14, 53.3% and 73.3% treated with Milbemax (R) were free of T. callipaeda, while 81.3% and 73.3 in the placebo group were still harbouring eye worms, resulting in a mean percentage worm count reduction for the treated group of 62.2% and 80.0%, respectively. Both results were significantly higher (p = 0.0106 and p = 0.0043) than the placebo group. Conclusions: The commercial formulation of milbemycin oxime at the minimal dose of 0.5 mg/kg and 2 mg/k in dogs and cats, respectively, showed a high therapeutic efficacy in curing T. callipaeda infestations. The advantages of an oral application are additionally increased by the large spectrum of activity of praziquantel and milbemycin oxime against Cestodes and Nematodes infesting dogs and cats.