title: Chemoprophylaxis of Dirofilaria immitis (Leidy 1856) infection at a high challenge environment.
abstract: BACKGROUND
  The frequency of canine heartworm infection in the state of Rio de Janeiro, Brazil was high before chemoprophylactic treatment was available, with one of the highest rates of infection (52.5 %) found among dogs living on the eastern shore of the state. Following the launch of a chemoprophylactic product, the rate of infection gradually decreased, and new infections were rarely reported. After 2005, outbreaks reported at the eastern shore as well as for new infections in other areas of high infection frequency were considered to possibly be related to reduced efficacy of macrocyclic lactones. Therefore, this study aimed to evaluate the efficacy of topical heartworm preventatives from different drug families at the high challenge area of the state of Rio de Janeiro.
  
  
  METHODS
  A total of 46 dogs, including animals negative for Dirofilaria immitis microfilariae and antigen (Snap 4 Dx, IDEXX Laboratories, USA) at the initial screening were randomly allocated to two monthly treatment groups. Dogs in one group received topical moxidectin + imidacloprid and dogs in the other group received topical selamectin for eight consecutive months. Blood samples were obtained for microfilariae and antigen detection until the eleventh month after the first treatment. Dogs becoming microfilaremic or antigenemic on or before day 180 were considered to be infected prior to the first dose and were excluded from the study.
  
  
  RESULTS
  A total of 29 dogs completed the study, including 14 treated with moxidectin + imidacloprid and 15 treated with selamectin. No dogs treated with moxidectin + imidacloprid (0/14) became infected during the treatment period, whereas four dogs of the selamectin group (4/15) became infected.
  
  
  CONCLUSIONS
  Topical moxidectin + imidacloprid is 100 % effective in preventing D. immitis infections in dogs living in a high challenge natural environment.
authors.affiliation: Programa de Pós-Graduação em Medicina Veterinária, Faculdade de Veterinária, Universidade Federal Fluminense, Rua Vital Brazil 64, Santa Rosa, CEP 24230-340, Niterói, RJ, Brazil. labarthe@fiocruz.br.|Programa Institucional Biodiversidade e Saúde, Fundação Oswaldo Cruz, Av. Brasil 4036, Manguinhos, CEP 21040-361, Rio de Janeiro, RJ, Brazil. labarthe@fiocruz.br.
authors.forename: Norma Vollmer
authors.initials: NV
authors.lastname: Labarthe
authors.affiliation: Doutoranda do Programa de Pós-Graduação em Medicina Veterinária, Faculdade de Medicina Veterinária, Universidade Federal Fluminense, Rua Vital Brazil 64, Santa Rosa, CEP 24230-340, Niterói, RJ, Brazil. liliwillimonteiro@hotmail.com.
authors.forename: Liliane Maria Valentim
authors.initials: LM
authors.lastname: Willi
authors.affiliation: Departamento de Medicina e Cirurgia Veterinária, Instituto de Veterinária, Universidade Federal Rural do Rio de Janeiro, BR-465, Km 7, CEP 23890-000, Seropédica, RJ, Brazil. jonimarpaiva@uol.com.br.
authors.forename: Jonimar Pereira
authors.initials: JP
authors.lastname: Paiva
authors.affiliation: Médica Veterinária Vet Ypiranga, Rua Ypiranga 107, Laranjeiras, CEP 22231-120, Rio de Janeiro, RJ, Brazil. mgnmiranda@yahoo.com.br.
authors.forename: Marcia Gonçalves Nobre de
authors.initials: MG
authors.lastname: Miranda
authors.affiliation: Bayer S.A., Bayer Technology Services, Av. das Américas, 500, Downtown Bloco 11, Loja 108, 26640-100, Rio de Janeiro, RJ, Brazil. karen.zoreck@bayer.com.
authors.forename: Karen
authors.initials: K
authors.lastname: Zoreck
authors.affiliation: Programa de Pós-Graduação em Medicina Veterinária, Faculdade de Veterinária, Universidade Federal Fluminense, Rua Vital Brazil 64, Santa Rosa, CEP 24230-340, Niterói, RJ, Brazil. fma@centroin.com.br.
authors.forename: Flavya Mendes de
authors.initials: FM
authors.lastname: Almeida
mesh_terms: D000287:Administration, Topical; D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage*; D001938:Brazil; D018890:Chemoprevention; D004183:Dirofilaria immitis / Q000187:drug effects* / Q000276:immunology; D004184:Dirofilariasis / Q000517:prevention & control*; D004283:Dog Diseases / Q000517:prevention & control*; D004285:Dogs; D004359:Drug Therapy, Combination; D004777:Environment; D005260:Female; D007093:Imidazoles / Q000008:administration & dosage*; D007559:Ivermectin / Q000008:administration & dosage / Q000031:analogs & derivatives*; D007783:Lactones / Q000494:pharmacology; D018942:Macrolides / Q000008:administration & dosage*; D008297:Male; D008842:Microfilariae; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000008:administration & dosage*
chemical_list: D000871:Anthelmintics; D007093:Imidazoles; D007783:Lactones; D018942:Macrolides; D000073943:Neonicotinoids; D009574:Nitro Compounds; C082359:imidacloprid; D007559:Ivermectin; C414354:selamectin; C027837:moxidectin