Risk factors of spp. infection and the association between spp. and T-lymphocyte subset alteration in asymptomatic retrovirus-infected cats in Bangkok Metropolitan, Thailand.

Background And Aim: Cats are a reservoir for spp. infection in humans. Human bartonellosis causes disseminated inflammation to develop in immunocompromised patients, such as those infected with human immunodeficiency virus. However, the associated risks of spp. infection in immunocompromised retroviral-infected cats have been inconclusive. This study aimed to evaluate the associated risks of spp. infection with the alteration of T-lymphocyte subsets of retroviral-infected cats.

Materials And Methods: We collected blood samples from 161 client-owned cats at veterinary clinics and hospitals throughout the Bangkok Metropolitan area from 2017 to 2020. The samples underwent hematological biochemical tests, feline retroviral status evaluation, spp. polymerase chain reaction assay, immunofluorescence assay, and CD4 and CD8 lymphocyte counts. Risk factors associated with spp. infection were determined by odds ratio (OR). Hematological and biochemical parameters were compared using independent t-tests. CD4 and CD8 lymphocyte counts and the CD4/CD8 ratio were compared among groups classified according to their retroviral and spp. infection status.

Results: The prevalence of spp. in our study cohort was 16.1%, and the seroprevalence was 94.9%. Cats aged >1 year were at a higher risk of seropositivity than cats aged <1 year (OR: 4.296, 95% confidence interval: 1.010-18.275). The CD8 percentage was significantly higher in seropositive cats (p = 0.026). There was a significant reduction in the CD4/CD8 ratio between cats negative for both retrovirus and spp. infection and cats with concurrent retrovirus and spp. infection (p = 0.041).

Conclusion: In endemic countries or areas, cat owners must be made aware of the risk of exposure to spp. due to the high rate of bacteremia and seroprevalence. Retrovirus-infected cats with concurrent spp. infection also showed a significant, inverted CD4/CD8 ratio, which may be used as a novel marker in bartonellosis. Similar studies focusing on the different stages of retrovirus infection should be undertaken further to elucidate the effect of retrovirus infection on spp. infection.