AIDS in cats and kidney disease
Feline immunodeficiency virus (FIV) infection affects a large number of cats, mainly those who live in the wild, with a prevalence of 9.4% in healthy cats and 16.4% in their sick counterparts, according to a study by the Universidad Complutense de Madrid1. This retrovirus from the genus Lentivirus is responsible for the onset of AIDS (acquired immunodeficiency syndrome).
During the course of the infection, FIV produces immunological abnormalities characterised by the death of CD4 T lymphocytes and an inversion of the CD4/CD8 T cell ratio, which results in a greater vulnerability to contracting opportunistic infections and developing various clinical/pathological conditions.
Lower urinary tract infections are one of the problems associated with feline AIDS, although human HIV has also been associated with various renal syndromes, including acute and chronic kidney failure, as indicated in a study by the George Washington University Medical Center2, although the underlying pathogenic mechanisms are yet to be clarified. Given that HIV and FIV share numerous biological and pathological characteristics, it is important to explore the link between feline AIDS and kidney disease.
Illness in cats infected with FIV
A study carried out at the University of Florida 3 analysed 153 FIV-infected and 306 FIV-noninfected client-owned cats and compared them with 95 FIV-infected and 98 FIV-noninfected research colony cats. The investigators found that there was no relationship between FIV and renal azotaemia in the population of client-owned cats.
However, the FIV-infected cats from the colony presented proteinuria. The protein/creatinine ratio in urine was also positively correlated with the CD4/CD8 lymphocytes ratio. Factors such as health status and sterilisation were not determinant, therefore the study concluded that “proteinuria, but not azotaemia, is associated with natural FIV infection”.
It should be noted that the presence of proteins in urine, although transitory, is also an early marker for chronic disease, a sign of systemic disease or an indicator for the onset of worsening kidney function. Indeed, a previous study4 carried out in Australia with 326 FIV-infected cats found a significant association between AIDS, azotaemia and smaller kidneys on palpation.
Morphological changes to kidney tissue associated with feline AIDS
A more recent study carried out at the University of Pisa5 compared 51 cats infected experimentally with FIV and 21 cats infected naturally, finding morphological changes to kidney tissue.
These investigators found that the main alterations in cats infected experimentally with FIV, which were kept in isolation units and were free from specific pathogens, and were monitored regularly for different clinical/pathological conditions, were mesangial expansion, with or without segmental glomerulosclerosis and immune-mediated GNS (N-acetylglucosamine-6-sulfatase). These renal changes were also observed in cats infected naturally with FIV, although renal amyloidosis and the presence of interstitial infiltrates were exclusive to the latter group.
In light of these findings, it can be concluded that a large number of FIV-infected cats present kidney problems. It is likely that the renal cell response triggered by FIV proteins and an immune-activated microenvironment play a key role in the onset of these problems. As such, it is essential to perform renal follow-up and care in FIV-infected cats, including a renal diet such as Advance Veterinary Diets Renal, with its limited supply of high-quality proteins.
