Imagine this clinical scenario: you examine a cat presenting with gingivostomatitis and weight loss that has a history of getting into frequent cat fights. Due to the latter, you run a point-of-care feline immunodeficiency virus (FIV)/feline leukaemia virus (FeLV) test, which returns an antibody-positive result for FIV.
After you’ve recommended lifestyle changes and supportive therapy, the owner asks if there is any medication available to directly target the cat’s FIV infection. You have heard of the use of recombinant feline interferon omega (rFeIFN-ω) for treating cats with retroviral infections, but you are unsure how efficacious it is for improving clinical signs in symptomatic FIV patients. You decide to consult the evidence to learn more.
The evidence
Three studies were critically reviewed, including a randomised double-blinded placebo-controlled trial (de Mari et al., 2004), a non-randomised controlled trial (Doménech et al., 2011) and an uncontrolled clinical trial (Gil et al., 2013).
Three studies were critically reviewed, including a randomised double-blinded placebo-controlled trial, a non-randomised controlled trial and an uncontrolled clinical trial
De Mari et al. (2004) observed 81 cats that tested positive for FeLV or copositive for FeLV and FIV and were displaying symptoms. The cats were randomly assigned to two groups: one receiving rFeIFN-ω and the other receiving a placebo. The outcomes evaluated were rectal temperature, general behaviour, appetite, thirst, dehydration, mucous membrane appearance and stomatitis. Each outcome was scored from zero to three for severity to create an overall clinical score and was assessed five times over four months.
Doménech et al. (2011) observed 21 symptomatic and asymptomatic cats that had tested positive for FIV or FeLV. The treatment group was given rFeIFN-ω, while the control group was left untreated and not provided with a placebo. The outcomes evaluated were loss of appetite, weakness, dehydration, weight loss, lymphadenomegaly, pale mucous membranes, polyuria/polydipsia, conjunctivitis, keratitis, oral lesions, digestive disorders, cutaneous lesions, respiratory disorders, neurological disorders, lymphoma, myeloproliferative disorders and other neoplasia. Each outcome was scored from zero to two for severity to create an overall clinical score and was assessed once two weeks after treatment.
Gil et al. (2013) observed 16 cats that had tested positive for FIV or FeLV or were copositive for FIV/FeLV and showed at least one clinical sign potentially related to retroviral infection. All cats were treated with rFeIFN-ω, and were assessed for 11 clinical signs commonly associated with retroviral infection: oral ulcers/gingivitis, caudal stomatitis/palatitis, ophthalmic abnormalities, lymphadenopathy, ocular and nasal discharge, mucous membrane colour, coat appearance, body condition score, faecal appearance and concurrent diseases/co-morbidities. Each was scored from zero to two for severity and was assessed four times over 65 days.
Limitations of the evidence
Overall, the quality of evidence to support the PICO question is weak, and all three papers had limitations.
None of the papers focused solely on the clinical benefits of rFeIFN-ω in symptomatic FIV-positive cats, and all study populations also included FeLV-positive cats. In de Mari et al. (2004) and Doménech et al. (2011), the FeLV- and FIV-positive cats were not treated as distinct groups when the statistical analysis was conducted. Although de Mari et al. (2004) had the best study design as the only randomised controlled trial, all FIV-infected cats in this study were also coinfected with FeLV. All papers had a small sample size of FIV cats, lacked sample size calculations and did not consider whether the clinical signs experienced by each cat at the beginning of the study were truly due to FIV.
None of the papers focused solely on the clinical benefits of rFeIFN-ω in symptomatic FIV-positive cats, and all study populations also included FeLV-positive cats
Doménech et al. (2011) had additional limitations. These were:
- The method of FIV/FeLV diagnosis was not specified
- The study was not blinded or randomised
- No placebo was provided to the control group
Further, the control and treatment groups were exposed to different environmental factors.
Gil et al. (2013) had limitations in addition to the above. These were:
- The lack of a control group
- A lack of variety of clinical signs in the study population
- A potential conflict of interest
Summary of findings
All three papers found that cats treated with rFeIFN-ω experienced an improvement in clinical signs. However, this must be considered in the context of the limitations outlined above.
De Mari et al. (2004) found that both the treatment and control groups experienced rapid and general improvement in clinical signs. However, the cats in the rFeIFN-ω treatment group displayed a consistently lower clinical score than the placebo group, indicating a significant reduction in clinical signs compared to the placebo group.
Doménech et al. (2011) found that symptomatic cats in the treatment group displayed a statistically significant clinical improvement in comparison with the control group.
Gil et al. (2013) observed significant improvement in the overall clinical signs of the cats studied. Ten cats experienced a reduction in clinical signs, but six cats maintained the same clinical status. None experienced a worsening of their condition. In the FIV-positive group, 44 percent (7/16) showed a statistically significant clinical improvement after treatment.
Conclusion
There is weak evidence demonstrating that rFeIFN-ω administration leads to reduced clinical signs in FIV-positive cats. While all papers reported that rFeIFN-ω significantly reduced clinical signs, all papers had limitations that weakened the findings. More robust evidence is required to prove that rFeIFN-ω has a definitive therapeutic benefit in symptomatic cats with FIV.
More robust evidence is required to prove that rFeIFN-ω has a definitive therapeutic benefit in symptomatic cats with FIV
There is a lack of well-designed double-blinded randomised placebo-controlled clinical trials with an adequate sample size and that focus exclusively on cats with FIV.
| The full Knowledge Summary can be read in RCVS Knowledge’s open access journal Veterinary Evidence. |
Disclaimer
The application of evidence into practice should take into account multiple factors, not limited to individual clinical expertise, patient’s circumstances, owner’s values, the individual case in front of you, the availability of therapies and resources, and the country, location or clinic where you work.
Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.
