Feline Upper Respiratory Infections
Viruses are spread by the wet sneezes of infected or carrier individuals. The herpesvirus is very fragile, surviving only 18 hours outside its host; caliciviris is tougher, lasting up to 30 days. Bleach will readily inactivate either virus but calici is able to withstand unbleached laundry detergents.
COURSE OF INFECTION
To some extent, the combinations of symptoms and course of infection is determined by which of numerous infectious agents is responsible. Ninety percent of feline upper respiratory infections are caused by either feline herpes (also called the “rhinotracheitis” virus) or feline calicivirus. Neither of these infections is transmissible to humans or to other animals.
Most feline colds run a course of 7 to10 days regardless of treatment but it is important to realize that these infections are permanent and that herpesvirus infections are recurring (a property of all types of herpes infections). In kittens herpes infections are notorious for dragging out. Stresses such as surgery (usually neutering/spaying), boarding, or introduction of a new feline companion commonly induce a fresh herpes upper respiratory episode about a week following the stressful event with active virus shedding for another couple of weeks. These episodes may recur for the life of the cat though as the cat matures, symptoms become less and less severe and ultimately may not be noticeable to the owner. Cats infected with calici may shed virus continuously, not just in times of stress, and may do so for life, though about 50% of infected cats seem to stop shedding virus at some point.
A cat with herpes is contagious to other cats for a couple of weeks after a stressful event. Cats infected with calici are contagious for several months after infection but do not appear to have recurrences the same way cats with herpes do.
WHEN TO BE CONCERNED: SIGNS A CAT REQUIRES HOSPITALIZATION
A cold for a cat is usually just a nuisance as a cold usually is for one of us. Sometimes though an upper respiratory infection can be serious. If a cat is sick enough to stop eating or drinking, hospitalization may be needed to support him or her through the brunt of the infection. A cat (usually a kitten) can actually get dehydrated from the fluid lost in nasal discharge. Painful ulcers can form on the eyes, nose or in the mouth. Sometimes fever is high enough to warrant monitoring. In young kittens, pneumonia may result from what started as an upper respiratory infection.
If you think your cat or kitten is significantly uncomfortable with a cold you should seek veterinary assistance with an office visit.
HOW IS THIS USUALLY TREATED?
How an upper respiratory infection is treated depends on how severe it is and whether or not there seems to be a bacterial infection complicating the viral infection. A mildly symptomatic adult cat might need no treatment at all as the symptoms should naturally wane over 1-2 weeks. A heavily congested kitten is likely to need antibiotics and possibly even hospitalization. Antibiotics act not only on bacteria that complicate viral infection but some upper respiratory infections are bacterial and not viral at all. The next most common infectious agents (after herpes and calici) are Chlamydophila felis (formerly known as Chlamydia psittaci) and Bordetella bronchiseptica, both organisms being sensitive to the tetracycline family (such as doxycycline). For this reason, when antibiotics are selected, tetracyclines and their relatives are frequently chosen. Other commonly used antibiotics are: Clavamox®, azithromycin, cephalexin, and clindamycin. Oral medications, and/or eye ointments are commonly prescribed. Severely affected cats may need to have inhalational antibiotics, fluids administered intravenously or under the skin to maintain hydration, and/or some sort of assisted feeding.
Some cats are severely affected and addressing the secondary bacterial infection is simply not enough to achieve comfort. For these situations, antiviral medications such as famciclovir can be used to address the actual viral infection and often even chronic symptoms can be controlled at least temporarily.
Cats are too small to be able to meaningfully blow their noses or sneeze out very dry or thick sinus secretions. Oral supplementation with N-Acetylcysteine can be very helpful in breaking down this material.
Oral lysine supplements are frequently used to suppress the replication of the herpesvirus and are available in powders, gels, and treats.
Polyprenyl immunostimulant is a biological product made by Vetimmune® presently licensed conditionally by the USDA for the treatment of feline herpes infection. This product is given orally once a day for 2 weeks and reportedly stimulates cellular immunity (as opposed to antibody-related immunity). Conditional licensing means that there is enough evidence of safety and efficacy for the product to be made available commercially but investigation is still on-going as to how well it works.
More chronically infected cats with severely blocked sinuses can have their sinuses flushed out under anesthesia. This can clear a great deal of materials out of the nasal passages but how long results persist is variable.
Consult your veterinarian before attempting any sort of home treatment.
WHAT ARE THE VACCINATION OPTIONS?
A FEW WORDS ABOUT “HEMORRHAGIC CALICIVIRUS”
A particularly virulent strain of calicivirus, commonly referred to as “hemorrhagic calici,” has appeared to “pop up” out of nowhere. While few outbreaks have been reported, it is possible more have occurred and gone unrecognized. Hemorrhagic calici is highly contagious and rapidly fatal. A special vaccine, called “Calicivax,” has become available from Boehringer Ingelheim just for this special form of calici. While the infection is very rare, you may wish to vaccinate your cat for it and/or may wish to discuss this option for completely with your veterinarian.
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Page last updated: 6/11/2018