Age-related cognitive impairments in domestic cats naturally infected with feline immunodeficiency virus

Investigations into disease associations with feline immunodeficiency virus (FIV) infection in lions (Panthera leo) in Australia: a case-control study

BACKGROUND

Feline immunodeficiency virus (FIV) is a highly mutable retrovirus with numerous species-specific strains, such as those infecting domestic cats (Felis catus, FIVFca) and wild populations of nondomestic cats including lions (Panthera leo, FIVPle). When FIVFca infection manifests as disease in domestic cats, common presentations include lymphadenopathy, lymphoid malignancies, oral cavity disease, immunological dysfunctions and neurological abnormalities. In contrast to domestic cats, there has been little published evidence of direct FIVPle disease associations in lions. The objective of the study, therefore, was to conduct a longitudinal case-control comparison of clinical findings and survival analysis of FIVPle-infected and FIVPle-uninfected captive lions to investigate possible FIVPle disease associations in nondomestic felids in Australia.

METHODS

Between 2005 and 2023, 38 lions were recruited from zoos across Australia. Lions had been FIV tested as part of a routine diagnostic service. The 38 lions included in the study comprised 15 FIV-infected (9 males, 6 females) and 23 FIV-uninfected (9 males, 14 females) animals. Lifetime longitudinal clinical histories and clinicopathological data collected by zoos for these lions were interrogated, including survival data.

RESULTS

FIV-infected lions were more likely to be reported with lower mean corpuscular volume (MCV) (fL) (P = 0.015), monocytes (%) (P = 0.023), chloride (mmol/L) (P = 0.016) and phosphate (mmol/L) (P = 0.029), but with a higher mean corpuscular hemoglobin concentration (MCHC) (g/L) (P = 0.001) and bicarbonate (mmol/L) (P = 0.035), than FIV-uninfected lions. The disease associations usually seen in domestic cats with FIV infection were not observed in lions, and there was no difference in survival between FIV-infected and FIV-uninfected lions. The main limitation of the study was a small sample size dictated by the number of lions able to be recruited from zoos in Australia over an 18-year period.

CONCLUSION

Few differences were found between case and control groups, suggesting that FIV-infected lions did not experience clinicopathological changes that predisposed them to future disease compared with FIV-uninfected lions. Further research will help to determine whether these results are indicative of a general absence of FIV-associated disease in captive lions, or the result of nonpathogenic FIVPle subtype(s) present in Australia.

Feline Cognition and the Role of Nutrition: An Evolutionary Perspective and Historical Review

Research into cognition in cats and the impact of nutrition on cat cognitive health lags behind that in dogs but is receiving increased attention. In this review, we discuss the evolutionary history of the domesticated cat, describe possible drivers of domestication, and explore the interrelationships between nutrition and cat cognition. While most cat species are solitary, domesticated cats can live in social groups, engage in complex social encounters, and form strong attachments to humans. Researchers have recently started to study cat cognition using similar methods as those developed for dogs, with an initial primary focus on perception and social cognition. Similar to dogs, cats also show cognitive and behavioral changes associated with stress and aging, but these signs are often gradual and often considered a consequence of natural aging. Despite the fundamental role of nutrition in cognitive development, function, and maintenance, research into the association between nutrition and cognition in cats is only preliminary. Ultimately, additional research is needed to gain a full understanding of cat cognition and to explore the role of nutrition in the cognitive health of cats to help improve their welfare.

Clinicopathological and Epidemiological Findings in Pet Cats Naturally Infected with Feline Immunodeficiency Virus (FIV) in Australia

Feline immunodeficiency virus (FIV) infection in experimentally infected domestic cats produces characteristic clinical manifestations including hematological changes, neurological disease, neoplasia (most notably lymphoma) and lymphopenia-mediated immunodeficiency predisposing cats to a range of secondary infections. Conflicting reports exist, however, with regard to disease associations and survival time in naturally FIV-infected cats. The purpose of this retrospective case−control study was to investigate the effect of natural FIV infection on hematological, blood biochemical and urinalysis parameters and survival time in three cohorts of pet cats in Australia. Cohorts 1 and 2 were recruited from a large veterinary hospital in Melbourne, Victoria (n = 525 and 282), while a third cohort consisted of cats recruited from around Australia as part of a FIV field vaccine efficacy trial (n = 425). FIV-infected cats in cohorts 1, 2 and 3 were found to have 15/37 (41%), 13/39 (33%) and 2/13 (15%) clinicopathological parameters significantly different to FIV-uninfected cats, respectively. Two changes in FIV-infected cats in cohort 1, hypochromia (low hemoglobin) and hyperglobulinemia, were outside the supplied reference intervals and should serve as diagnostic triggers for FIV testing. Kaplan−Meier survival analysis of cats in cohorts 1 and 2 combined did not find any difference between FIV-infected and FIV-uninfected cats, however a confounding factor was a large euthanasia rate within the first 12 months in both groups. Three significant (p < 0.05) spatial clusters of FIV infection were identified in Melbourne. A possible relationship between FIV infection status and socioeconomic disadvantage was discovered, based on three government indices of socioeconomic status (p < 0.001). Until longitudinal field studies are performed in Australia to further investigate the long-term effects of natural FIV infection, Australian veterinarians should consider FIV to be an important infection of pet cats, and recommend measures to prevent FIV infection.