Transmission trials, ITS2-PCR and RAPD-PCR show identity of Toxocara canisisolates from red fox and dog

Toxocara canis isolates from dog and from red fox were compared in transmis sion trials and with molecular analysis using RAPD-PCR technique and compar ison of the ITS2 sequence. After oral infection of bitches with 20,000 embr yonated T. canis eggs of vulpine and canine origin, the vertical transmissi on to pup's was examined. All animals of both groups developed typical clin ical symptoms of toxocarosis. The haematological, serological, parasitologi cal and post mortem results showed no differences between both isolates exc ept for the infectivity of T. canis stages in mice where the fox isolate sh owed a significant higher infectivity than the dog isolate. The RAPD-PCR sh owed a similarity coefficient of 0.95, similar to the range of intraspecifi c variation in Toxocara cati and Toxascaris leonina specimens as outgroups. The ITS2 comparison showed a 100% identity between both isolates with no i ntraspecific variations. Therefore, the study shows that the fox and the cl og isolate of T. canis were identical in infectivity, transmission and mole cular structure; a host adaptation could not be found and the fox has to be seen as a reservoir for T. canis infections in dogs. Considering the incre asing number of forts in urban areas the importance of helminth control in dogs is stressed. (C)1999 Elsevier Science B.V. All rights reserved.