WVC 2017: Managing Cats With Upper Respiratory Infection

If you see cats in your practice, you undoubtedly will 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 in large part because most adopted cats come from an animal shelters, which are an ideal environment for the spread of infectious organisms.

Dr. Lappin discussed 2 of the leading causes of respiratory infections in cats—bacterial and viral—in a presentation at the 2017 Western Veterinary Conference in Las Vegas. The International Society for Companion Animal Infectious Diseases (ISCAID) developed guidelines for the treatment of respiratory disease that are available at iscaid.org.¹ The guidelines are available to anyone, and Dr. Lappin encouraged all attendees to become familiar with them.

Bacterial Causes

Determining whether a patient has a bacterial component to its upper respiratory disease is difficult. The ISCAID guidelines state that all cats with signs of purulent to mucopurulent ocular discharge, nasal discharge, conjunctivitis, sneezing, and epistaxis may have a bacterial component to their disease. They also define acute infections as those lasting less than 10 days and chronic infections as lasting longer than 10 days.

Dr. Lappin reminded attendees that secondary bacterial infections associated with feline herpesvirus (FHV-1) or feline calicivirus (FCV) are more common than primary bacterial infection. Secondary bacterial organisms often include Pasteurella multocida, Staphylococcus spp, Streptococcus spp, Escherichia coli, and anaerobes. Primary causes of bacterial infection include Bordetella bronchiseptica, Chlamydia felis, Mycoplasma spp, Streptococcus spp, and P. multocida.

For cats with signs of upper respiratory tract disease of less than 10 days’ duration, taking a careful history is an important part of evaluating potential causes, which can include vaccination, exposure to other cats, foreign bodies, contact with a shelter or veterinary hospital, exposure to dogs, and stress. A thorough physical exam to check for lower respiratory issues and a feline leukemia virus/feline immunodeficiency virus test to check immune status are in order.

According to the ISCAID Working Group, there is limited benefit to performing cytology to ascertain an upper respiratory infection’s bacterial component. Culture and sensitivity testing is also not encouraged in acute cases because common bacterial pathogens are difficult to grow in standard cultures and a positive culture may be the result of commensal bacterial growth. In acute cases with no other identified problems, ISCAID recommends observation for 10 days because the cause may be an uncomplicated viral infection that should resolve on its own.

For suspected cases of secondary bacterial rhinitis, veterinarians are encouraged to do a workup if problems or clinical signs persist or worsen after 10 days. Dr. Lappin reminded the audience that rhinitis could be secondary to trauma, tooth problems, polyps, soft palate issues, cancer, foreign bodies, and viral-induced inflammation. Patients that present acutely and are not getting better on their own or with or antibiotics (in cases that originally presented with a fever) should be worked up for these other causes. If the workup yields no evidence of another disease in chronic cases, ISCAID recommends choosing an antibiotic based on culture and sensitivity results and continuing its use 1 week beyond the resolution of clinical signs.

Viral Causes

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

Viral rhinitis can recur several times with or without a bacterial component. Treatment with oral lysine at 250 to 500 mg twice daily may be helpful in the management of FHV-1—associated illness, but only at the full dose. Lysine, either alone or in fortified food, however, 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 is relatively safe in cats and can be used at a dose of 40 to 90 mg/kg orally every 8 to 12 hours. Cidofovir is a topical agent that can be used twice daily to treat ocular FHV-1; it is more convenient, appears to cause less irritation than other ocular therapies (eg, idoxuridine), and is available through some compounding pharmacies. Giving oral human interferon daily may help some cats chronically infected with FCV or FHV-1 through immunomodulation. Human interferon is available through specialty pharmacies.

The use of Nestlé Purina’s Fortiflora (Enterococcus faecium SF68) 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 1 study, a single-dose intranasal FHV-1/FCV modified-live vaccine given to shelter cats that failed to improve with supportive and antibiotic treatment had some benefit.⁴ The vaccine appeared to be more effective than repeated doses of alpha or beta interferons. 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. The results of another study of an intranasal modified-live vaccine showed a decrease in sickness compared with controls, perhaps indicating an increased local immune response 7 days after challenge with B. 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 animal shelters, and cats that spend 23 days in a shelterlike environment have a 98% chance of being exposed to FHV-1 or FCV. Exposure does not mean fulminant illness, however, and many clinical cases involve young, old, immunocompromised, or stressed cats. Adapting shelters and homes to the social and environmental needs of cats and using stress reducers, such as the synthetic feline pheromone 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 many 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.