Establishment of Full-Length cDNA Clones and an Efficient Oral Infection Model for Feline Coronavirus in Cats.

Feline infectious peritonitis virus (FIPV) is the etiologic agent of feline infectious peritonitis (FIP) and causes fatal disease in cats of almost all ages. Currently, there are no clinically approved drugs or effective vaccines for FIP. Furthermore, the pathogenesis of FIP is still not fully understood. There is an urgent need for an effective infection model of feline infectious peritonitis induced by FIPV. Here, we constructed a field type I FIPV full-length cDNA clone, pBAC-QS, corresponding to the isolated FIPV QS. By replacing the FIPV QS spike gene with the commercially available type II FIPV 79-1146 (79-1146_CA) spike gene, we established and rescued a recombinant virus, designated rQS-79. Moreover, we constructed 79-1146_CA infectious full-length cDNA pBAC-79-1146_CA, corresponding to recombinant feline coronavirus (FCoV) 79-1146_CA (r79-1146_CA). In animal experiments with 1- to 2-year-old adult cats orally infected with the recombinant virus, rQS-79 induced typical FIP signs and 100% mortality. In contrast to cats infected with rQS-79, cats infected with 79-1146_CA did not show obvious signs. Furthermore, by rechallenging rQS-79 in surviving cats previously infected with 79-1146_CA, we found that there was no protection against rQS-79 with different titers of neutralizing antibodies. However, high titers of neutralizing antibodies may help prolong the cat survival time. Overall, we report the first reverse genetics of virulent recombinant FCoV (causing 100% mortality in adult cats) and attenuated FCoV (causing no mortality in adult cats), which will be powerful tools to study pathogenesis, antiviral drugs, and vaccines for FCoV. IMPORTANCE Tissue- or cell culture-adapted feline infectious peritonitis virus (FIPV) usually loses pathogenicity. To develop a highly virulent FIPV, we constructed a field isolate type I FIPV full-length clone with the spike gene replaced by the 79-1146 spike gene, corresponding to a virus named rQS-79, which induces high mortality in adult cats. rQS-79 represents the first described reverse genetics system for highly pathogenic FCoV. By further constructing the cell culture-adapted FCoV 79-1146_CA, we obtained infectious clones of virulent and attenuated FCoV. By in vitro and in vivo experiments, we established a model that can serve to study the pathogenic mechanisms of FIPV. Importantly, the wild-type FIPV replicase skeleton of serotype I will greatly facilitate the screening of antiviral drugs, both in vivo and in vitro.

Prevalence and risk factors for canine obesity surveyed in veterinary practices in Beijing, China.

An epidemiological survey of canine obesity was carried out in Beijing, China. Cases (n=2391, 7 districts) were collected at 14 animal hospitals between April 2008 and April 2011. The body condition score (scales of 1-5) was used to assess obesity of the dogs (Burkholder and Toll, 2000; Laflamme, 1997). Obesity rates were analyzed with respect to breed, age, sex, neutering, food control, feeding frequency, reproduction status, food type, nutritional supplements, living environment, feeding time, number of pets per household, feeding purpose, activity control, exercise duration, exercise status and exercise type. The overall canine obesity rate was 44.4% in this survey. The risk factors for dog obesity were food type (non-commercial food, OR=1.377, p<0.05), age (1-2 y, OR=0.044, p<0.001), activity control (free activity, OR=0.685, p<0.05), neutering (intact, OR=0.629, p<0.01), sex (male, OR=0.628, p<0.001), feeding frequency (Once per day, OR=0.521, p<0.01). By dog breed, prevalence of obesity was high in pugs (70.7%), Cocker Spaniel (69.4%), Pekingese (51.9%), Pomeranian (54.6%) and Golden Retriever (51.9%). This is the first report of the epidemiology of canine obesity in China.