Abstract
1 Department of Virology, Erasmus University, PO Box 1738, 3000 DR Rotterdam, The Netherlands
2 Seal Rehabilitation Centre, Hoofdstraat 94A, 9968 AG Pieterburen, The Netherlands
3 National Institute for Public Health and Environmental Protection, Antonie van Leeuwenhoeklaan 9, 3720 BA Bilthoven, The Netherlands
4 Laboratory of Clinical Virology, Huddinge Hospital, Huddinge, Sweden
5 Institute for Animal Health, Pirbright Laboratories, Ash Road, Woking, Surrey GU24 0NF, UK
and6 J. A. Baker Institute of Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
Specific pathogen free (SPF) domestic cats were inoculated with tissue homogenate obtained from a Chinese leopard (Panthera pardus japonensis) that had died in a North American zoo from a natural infection with canine distemper virus (CDV). The cats developed a transient cell-associated CDV viraemia along with pronounced lymphopenia but did not show any clinical symptoms. Plasma neutralizing-antibody titres against the homologous CDV (A92-27/4, isolated from the Chinese leopard) were consistently higher than against the CDV vaccine strain Bussell. The Chinese leopard CDV isolate showed in vitro biological properties reminiscent of virulent, wild-type CDV strains. Sequence analysis of the H gene of two large felid CDV isolates from the USA (A92-27/4 and A92-6) revealed up to 10% amino acid changes including up to four additional potential N-linked glycosylation sites in the extracytoplasmic domain as compared to CDV vaccine strains. Phylogenetic analysis was performed using the entire coding region of the H gene and a 388 bp fragment of the P gene of several morbillivirus species. Evidence was obtained that recent CDV isolates from different species in the United States (including isolates from large felids), Europe and Africa are significantly distinct from CDV vaccine strains. All wild-type CDV isolates analysed clustered according to geographical distribution rather than to host species origin. By sequence analysis a CDV epizootic among large felids in a Californian safari park was linked to a virus which most likely originated from feral non-felid carnivores.
* Author for correspondence. Fax +31 10 436 5145. e-mail osterhaus@viro.fgg.eur.nl