Safety Evaluation of Parastar ® Plus in Dogs and Assessment of Transferable Residue of Fipronil and Cyphenothrin from Dogs to Humans

Currently, the world’s dog population is estimated at 900 million (>80 million in the US,15.9 million in Russia, 8.5 million in the UK, 7.3 million in France, 7 million in Italy, and 6.9million in Germany). Dogs are easily infested with fleas, ticks, and other ectoparasites serving asvectors for transmitting bacterial, viral, and parasitic diseases. Therefore, the use ofectoparasiticides is inevitable and important. The present investigation was undertaken with twospecific objectives: one, to evaluate the safety of fipronil and cyphenothrin in dogs after topicalapplication of Parastar ® Plus, and two, to determine the transferable residue of these insecticidesfrom dogs to humans. Six healthy, adult dogs (medium length hair, weighing between 20.5-27.3kg) received topical application of Parastar ® Plus (2.68 mL; fipronil, 9.8% and cyphenothrin,5.2%) on the back between the shoulder blades. At pre-determined intervals, dogs were given afull physical exam, and residues of fipronil and cyphenothrin were determined in dog blood andcotton glove extracts using GC/MS. Fipronil and cyphenothrin peaks eluted at 7.453 and 9.913min, correspondingly, and the compounds were confirmed based on characteristic ions. At notime was fipronil or cyphenothrin residue detected in blood samples. In glove extracts, residuesof fipronil and cyphenothrin were maximally present at 24 hr post-treatment (43.84 ± 5.69 and59.26 ± 8.97 ppm, respectively). By 48 hr, the residue levels sharply declined (16.89 ± 2.82 and17.98 ± 2.07 ppm, respectively). The insecticides’ residues were detected in insignificantamounts after one week (5.69 ± 2.16 and 10.00 ± 1.51 ppm, respectively), and only in traceamounts after two weeks. At no time did any dog show side effects, except itching at the site ofParastar ® Plus application. The findings suggest that Parastar ® Plus was safe for dogs andtransferable residues of fipronil and cyphenothrin were minimal, posing very little or no healthconcern to pet-owners or veterinary personnel. Of course, veterinary personnel, who handlemany dogs daily, may require proper protection to avoid cumulative exposure.Keywords: Parastar ® Plus; fipronil; cyphenothrin; pyrethroids; ectoparasiticide safety; dogs.