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Clinical findings and survival in cats with FIV | VETgirl Veterinary Continuing Education Podcasts

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In today’s VETgirl online veterinary continuing education podcast, we discuss clinical findings and survival in cats with feline immunodeficiency virus (FIV). Is it a death sentence?

When it comes to infectious feline diseases that we often see in small animal practice, feline leukemia (FELV) and FIV are two that we commonly worry about and thus, test for. Studies have found that FIV is reportedly highest in the Asia Pacific region of the world (1, 2). Here in the United States, the incidence of FIV-positive cats is high, with a gross number of FIV-infected pet cats estimated to exceed 2.5 million. But, just because your feline patient was just diagnosed with FIV, does it mean that it has a poorer prognosis?

First, let’s talk a little bit about FIV. We know FIV is closely related to human immunodeficiency virus (HIV). In the absence of anti-retroviral treatment, humans with HIV experience predictable disease progression and well-defined clinical stages. By contrast, the clinical course of cats with FIV is not well characterized. Although many clinical signs have been reported in cats naturally infected with FIV – including oral lesions, immune-mediated diseases, -cytopenias, unusual or repeated infections, neurological signs, and renal disease – these clinical signs are present in comparable frequency to control populations of uninfected cats. We should mention one noted exception to the list of problems seen with FIV-infected cats is that they have a higher rate of lymphoma as compared to control populations (3). Given this, it may be difficult for a clinician to determine if a sick, FIV-infected cat is showing clinical signs and laboratory abnormalities secondary to FIV infection or not.

In order to evaluate if the diagnosis of FIV condemned a cat or not, Liem et al (4) out of University of Sydney wanted to evaluate the clinical findings and survival in cats naturally infected with FIV. They also wanted to compare clinicopathologic changes (such as hematological and biochemical changes), major clinical problems, and the overall survival between two groups of cats: those that were client-owned uninfected cats and a group of client-owned FIV-infected cats.

In this retrospective, case-controlled study, they evaluated 520 cats (in an Australian University setting). Overall, they found that the prevalence of FIV infection was 14.6%. Cats were tested for FIV using a commercially available serology kit for FIV and FELV; additional PCR testing was performed for FIV at a commercial Australian laboratory. Cats were defined as FIV-infected if they were seropositive and had not previously been vaccinated for FIV. Cats were defined as FIV-uninfected if they were seronegative or if they were seropositive with a prior history of FIV vaccination but were concurrently negative for FIV on PCR.

All cats also had a complete blood count and chemistry panel performed. Likewise, each cat was categorized into different body systems based on the major clinical presenting problem. This included categories such as: healthy, not determined, cardiorespiratory, endocrine, gastrointestinal, genitourinary, immune-mediated, infectious, neurologic, neoplasia. Among those cats with neoplasia, the prevalence of lymphoid vs. other types of neoplasia was noted.

So, what’d they find in this study?

Overall, the mean age of FIV infected cats was 9.8 years of age, while for FIV uninfected was 7.8 years. Certain risk factors such older age (>5 yrs), being of the male sex, and being a mixed breed cat were more associated with the incidence of FIV infection. Clinicopathologic testing abnormalities were identified in both FIV-infected and FIV-uninfected cats; only sodium and monocyte counts differed significantly after adjusting for age and sex. FIV-infected cats were more likely to be hypernatremic and have a decreased monocyte count as compared to FIV-uninfected cats. (Whether or not this is clinical significant is debatable but hey, we’re just reporting the data!).

Approximately 95% of all cats presented with one or more clinical problems in the categories noted above. Most noteable, there was not a significant difference between the FIV-infected and FIV-uninfected groups with regard to clinical problems. Neoplasia and gastrointestinal diseases were the most common presenting problem in both groups, with lymphoid neoplasia being slightly more common in the FIV-infected group. Overall, there was no significant difference in survival age or survival time between the FIV-infected and FIV-uninfected groups.

Overall, this was a good study, but there were several limitations. First, the authors note that the FIV-uninfected group may not represent the total population of FIV-uninfected cats. After all, this was based on an academic setting, so it’s a skewed population (versus what you might see in private practice). Also, many of the FIV-infected cats were censored from the survival analysis since they were still alive at the end of the study. Finally, one key note to observe is that – since this study took place in Australia – it’s possible that the natural course of FIV infection could differ between the Asia Pacific strains of virus versus strains of virus in other geographical locales.

So, what can we take away from this VETgirl podcast?

Don’t condemn cats that are FIV positive. They often represent with abnormalities on their blood work, consistent with findings in older, sick, cats that are FIV-negative. These changes may not result from FIV disease progression. So, despite the limitations noted in this study, the prognosis for each FIV-infected cat should be made on an individual basis – assessing all clinical problems rather than just their FIV status. Don’t give up on them!

References:
1. Norris, JM, Bell ET, Hales L et al. Prevalence of immunodeficiency virus infection in domesticated and feral cats in eastern Australia. J Feline Med Surg 2007;9:300-308.
2. Nakamura Y, Ura A, Hirata M, et al. An updated nation-wide epidemiological survey of feline immunodeficiency virus (FIV) in Japan. J Vet Med Sci 2010;72:1051.
3. Magden E, Quackenbush SL, VandeWoude S. FIV associated neoplasms—A mini-review. Vet Immunol Immunopathol 2011;143:227-234.
4. Liem BP, Dhand NJ, Pepper AE, et al. Clinical Findings and Survival in Cats Naturally Infected with Feline Immunodeficiency Virus. J Vet Intern Med 2013:27:798-805.

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