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 25-28 September, 2018 | Singapore
M. Lappin1
1The Kenneth W. Smith Professor in Small Animal Clinical Vet- erinary Medicine, College of Veterinary Medicine and Biomed- ical Sciences, Colorado State University, Fort Collins Colorado, USA
The primary objectives of this session are to review the known bacterial and viral causes of the feline upper respiratory disease complex followed by a discussion
of optimal diagnostic tests, treatments and preventions. Please see the ISCAID respiratory treatment guidelines for further information on this very important topic (Lappin et al, 2017).
Bacterial causes. Almost all cats with mucopurulent or purulent nasal discharge have a bacterial component to their disease. Primary bacterial disease is rare but may be associated with Bordetella bronchiseptica, Mycoplasma spp. and Chlamydia felis. Streptococcus equi var. zooepidemicus may also be associated
with clinical illness in some cats. In one Morris Animal Foundation sponsored study, we showed Mycoplasmas to be more common that FHV-1 and were associated with illness. Recently it was shown that Bartonella spp. are not causes of rhinitis in cats. Both B. bronchiseptica and Mycoplasma spp. can be associated with bronchitis in cats. Chlamydiosis in general, is a mild infection resulting only in conjunctivitis.
If primary infections are suspected, doxycycline 10 mg/kg, PO, once daily (or divided BID) or topical administration of tetracyclines (conjunctivitis) are usually effective. Amoxicillin is the other empirical treatment recommended for management of bacterial rhinitis
of < 10 days duration (Lappin et al, 2017). Cats with
acute disease only need to be treated for 7 to 10 days. Most cases of bacterial rhinitis are secondary to other diseases including trauma, neoplasia, inflammation induced by viral infection, foreign bodies, inflammatory polyps, and tooth root abscessation. Thus, if routine antibiotic therapy fails, a diagnostic workup should be performed. After other primary causes are excluded, rescue drugs like quinolones, azithromycin, potentiated penicillins, or cephalosporins can be considered. Pradofloxacin has been shown to be a good choice as
a rescue drug for treatment of chronic bacterial rhinitis as this quinolone is effective against anaerobes and aerobes and enhanced activity against Mycoplasma spp. (Spindel et al, 2008).
Since bacterial rhinitis leads to chondritis and osteomyelitis, antibiotic therapy may be required for
days to wee should be continued for weeks in cats with chronic disease.
Viral diseases. Herpesvirus 1 (rhinotracheitis; FHV-1) and calicivirus (FCV) are the most common viral causes of sneezing and nasal discharge in the cat. If oral ulcers are present, calicivirus is most likely. If corneal ulcers are present, herpesvirus 1 is most likely. FHV-1 has now also been associated with chronic stomatitis, facial dermatitis, and endogenous uveitis. Viral rhinitis with or without secondary bacterial infection can be recurrent. FHV-1 can be documented by direct fluorescent staining of conjunctival scrapings, virus isolation, or polymerase chain reaction. Since FHV-1 DNA can be detected in conjunctival cells of approximately 25% of healthy cats, the positive predictive value of these tests in diseased cats is low. Quantitative PCR may ultimately prove
to correlate to the presence or absence of disease. Currently used PCR assays also detect vaccine strains of FHV-1. RT-PCR assays can be used to amplify the RNA of FCV. However, these assays have the same problems with predictive value as those to detect DNA of FHV-1. In one of recent publications, we showed that PCR assay results for FHV-1 or Mycoplasma failed to correlate to treatment responses to either an anti-viral drug or an antibiotic (Zirofsky et al, 2018). Thus, performance of these PCR assays have low positive predictive value.
Feline viral rhinitis with or without secondary bacterial infection can be recurrent. There are no consistently effective primary therapies. For FHV-1, lysine at 250-500 mg, PO, once or twice daily may be helpful in some cats and has been shown to be safe but should be given
as a dose, not fed with food. Lysine has been shown to be ineffective for prevention of upper respiratory tract infections in 2 separate shelter studies and so should probably not be used for this purpose.
Administration of human alpha 2b interferon at 50 U,
PO, daily may help some cats with suspected chronic calicivirus or FHV-1 infection. This can now be formulated for practitioners by prescription at some pharmacies ( in the USA. Topical administration of alpha interferon in saline to the eyes
of cats with conjunctivitis or the nose may aid in the management of some cats but has not been proven in a controlled study. Lysine and alpha interferon are unlikely to lead to a cure, but hopefully will lessen clinical signs of disease. Intranasal administration of modified live, intranasal FHV-1 and FCV vaccines may lessen disease in some chronically infected cats. If there is a positive response to intranasal vaccination in a cat with chronic disease, I will use this form of immunotherapy up to 3 times per year (Fenimore et al, 2015). The intranasal vaccine has been shown to potentiate cell-mediated immunity to FHV-1 better than parenteral vaccination.
Acyclovir is an anti-herpesvirus drug for use in people but can be toxic to cats and so should not be used.

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