WVC 2017: Managing Cats with Upper Respiratory Infection - Viral Causes

March 10, 2017
Beth Thompson, VMD

At WVC 2017, Dr. Mike Lappin outlined best practices for managing viral upper respiratory infection in cats.

If cats are among your patient base, then you are undoubtedly going to see a significant number of upper respiratory infections, according to Mike Lappin, DVM, PhD, DACVIM, a professor in the Department of Clinical Sciences at Colorado State University. This is largely because most adopted cats or kittens come from shelters, which are an ideal environment for the spread of infectious organisms. In his presentation at the 2017 Western Veterinary Conference in Las Vegas, Nevada, Dr. Lappin discussed one of leading causes of respiratory infections in cats—viruses.

The International Society for Companion Animal Infectious Diseases (ISCAID) developed respiratory treatment guidelines that have been published in the Journal of Veterinary Internal Medicine and are also available at iscaid.org.1 The guidelines are open access, and Dr. Lappin encouraged everyone to become familiar with them.

Viral diseases are thought to be the most frequent cause of upper respiratory illness in cats. In the majority of cases, the cause is feline herpesvirus (FHV-1) or feline calicivirus (FCV). If ocular lesions are present, think herpesvirus. If you see oral ulcers, think FCV. Chronic stomatitis, uveitis, and facial dermatitis have also been associated with FHV-1.

Viral rhinitis can recur many times with or without a bacterial component. Treatment with oral lysine at 250 to 500 mg q12h may be helpful in the management of FHV-1—associated illness, but only at the full dose administered twice daily. Lysine, either alone or in fortified food, has not demonstrated any effectiveness in preventing recurrence of FHV-1. Acyclovir is an antiviral used for treating herpes outbreaks in humans. However, it is toxic to cats and should be avoided. Famciclovir or its generic equivalent is relatively safe in cats and can be used at a dose of 40 to 90 mg/kg PO q8-12h. Cidofovir is a topical agent, available through some compounding pharmacies, that can be used twice daily to treat ocular FHV-1. It is more convenient to use and appears to cause less irritation than other ocular therapies (eg, idoxuridine). Giving oral human interferon by mouth daily may help some cats chronically infected with FCV or FHV-1 through immunomodulation. Human interferon is available through specialty pharmacies like roadrunnerpharmacy.com.

The use of Nestlé Purina’s Fortiflora (Enterococcus faecium SF-68) in normal cats increases the percentage of T-helper cells in blood.2 The probiotic was also shown to decrease conjunctival scores in one group versus controls.3

In one study, a single-dose of intranasal FHV-1 and FCV modified-live vaccine had some benefit in shelter cats that failed to improve with supportive and antibiotic treatment.4 The vaccine appeared to be more effective than repeated doses of a/b interferon. Interestingly, some of the cats dropped out of the study, as moving them from the shelter into a fostering environment improved their clinical signs sufficiently to exclude them from the study. This indicates the role stress plays in recrudescence of viral illness and suggests that modulating stress may be a key treatment component with FHV-1— or FCV-infected cats. Another study of an intranasal modified-live vaccine showed a decrease in sickness compared with controls and perhaps indicates an increased local immune response 7 days after challenge with Bordetella bronchiseptica.5 In Dr. Lappin's patients that respond to intranasal vaccination, he will repeat the vaccine up to 3 times per year.

Dr. Lappin pointed out that respiratory viral pathogens are ubiquitous in shelters, and cats that spend 23 days in a shelter-like environment have a 98% chance of being exposed to FHV-1 or FCV. Exposure doesn’t mean fulminant illness, however, and many clinical cases involve young, old, immunocompromised, or stressed individuals. Adapting shelters and homes to the social and environmental needs of cats and using stress reducers such as Feliway can help reduce the number and severity of feline viral upper respiratory outbreaks.

Dr. Thompson is a small animal veterinarian, animal health executive, editor, and writer. She has held numerous positions with oversight responsibilities for editorial and business direction, including for Veterinary Learning Systems (publisher of Veterinary Technician and Compendium), Vetstreet.com, HealthyPet, and NAVC.


  • Lappin MR, Blondeau J, Boothe D, et al. Antimicrobial use guidelines for treatment of respiratory tract disease in dog and cats: Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases. J Vet Intern Med. 2017;Feb 10. doi: 10.1111/jvim.14627. [Epub ahead of print].
  • Veir JK, Knorr R, Cavadini C, et al. Effect of supplementation with Enterococcus faecium (SF68) on immune functions in cats. Vet Ther. 2007;8:229-238.
  • Lappin MR, Veir JK, et al. Pilot study to evaluate the effect of oral supplementation of Enterococcus faecium SF68 on cats with latent feline herpesvirus 1. J Feline Med Surg. 2009;11:650-654.
  • Fenimore A, Carter K, Fankhauser J, et al. Evaluation of intranasal vaccine administration and high-dose interferon-a2b therapy for treatment of chronic upper respiratory tract infections in shelter cats. J Feline Med Surg. 2016;18(8):603-611.
  • Bradley A, Kinyon J, Frana T, et al. Efficacy of intranasal administration of a modified live feline herpesvirus 1 and feline calicivirus vaccine against disease cause by Bordetella bronchiseptica after experimental challenge. J Vet Intern Med. 2012;26(5):1121-1125.