Runny eyes. Sneezing. Nasal discharge. Loss of appetite. Shelter workers all know the signs.
Upper respiratory infections (URI for short) are probably the most commonly encountered disease problem for cats in animal shelters. Some shelters have cases all the time. Others have epidemics so serious that they result in the suspension of feline adoptions and depopulation of the shelter. Even the most conscientiously run shelter will suffer from occasional outbreaks.
These outbreaks should not be taken as an automatic sign that the shelter's health care system has failed. A careful evaluation of the health care program should be undertaken to determine what corrective measures are needed to minimize the impact of the disease on the shelter's feline population.
In most instances, elimination of the virus is impossible and so minimization of the impact of the disease is the goal. Upper respiratory infections frequently cause mild symptoms that can be prevented or resolved if the shelter has the resources to reduce crowding, isolate the sick animals, provide nursing care and treatment or place the cats in foster care until they are cured of clinical signs. The reluctance to euthanize animals with mild symptoms when isolation or foster care is not an option will contribute to the longevity and severity of the problem and the inability to rid the shelter of infection.
Whichever goal is chosen, an understanding of the diseases and disease transmission is essential to start.
One of the most important contributory factors to disease outbreaks is crowding, which leads to stress that lowers resistance, increased and prolonged close contact between diseased and susceptible animals, and greater probability that disease will be transmitted via fomites.
Herpes virus (rhinotracheitis) and calici virus are the two pathogens that account for the vast majority of cases seen, but disease can also be caused by Chlamydophila felis, a bacteria, as well as by Mycoplasma, an intracellular bacteria. There have been reports of cases of feline upper respiratory infections being caused by Bordetella bronchiseptica, the same bacterial organism that is responsible for infectious tracheobronchitis, or kennel cough, in dogs. There is evidence that Bordetella and Chlamydophila both cause disease in humans.
These diseases have an incubation period of between 2-14 days, referring to the time between exposure and the appearance of clinical signs. The pathogens are shed in various body fluids such as ocular, nasal and oral secretions and discharges. They are then spread by three mechanisms:
Aerosolization and airborne transmission of the viruses are no longer thought to be a primary means of spread of infection. They are mainly spread by fomites, which are inanimate objects. In fact, fomite transmission of disease is believed to be the most significant method of spread of any disease through a shelter. Viral particles that are found in ocular, oral and nasal secretions can contaminate clothing, hands, bedding, toys, food dishes, litter boxes, water bowls, cage floors, stethoscopes, etc.
Disease is spread when susceptible animals have contact with these contaminated objects, so isolation of sick animals alone is not a sufficient control mechanism. While neither virus lives for very long in the environment, calici can be difficult to kill. But since the viruses survive long term in the animal and not the environment, this renders environmental decontamination less critical for disease control than proper management of the population.
The existence of the carrier state is particularly important for shelters that do not euthanize for crowding or disease control. Animals that have recovered from acute infections will continue to shed virus and therefore remain infectious for the duration of their stay in the shelter.
The incubation period of herpes is 2-6 days. Most cats that have recovered from herpes will be carriers of the virus for life. They shed it intermittently under normal conditions and during times of stress. This shedding can begin a week after the stressful incident and continue for 3 weeks afterward. They may shed virus after recovery from illness for 3 weeks.
The incubation period of calici virus is 1-5 days. Some cats that have recovered from infection will shed the virus continuously for the rest of their lives without regard to stress. 50% shed at least 75 days post-recovery regardless of stress. Fortunately most cats do eliminate calici virus from their bodies eventually.
It is believed that there is a carrier state with bordetella, but the mechanisms are not entirely clear yet. Bordetella has an incubation period of 3-10 days and can be shed for 3 months post recovery. Transmission is via direct contact, fomites and aerosol. It is zoonotic but human cases are believed to be rare.
The incubation period of chlamydophila is 3-14 days and post recovery shedding can last as long as 18 months. Transmission of the organism is either through direct contact or fomites. It is zoonotic.
This intracellular bacteria is commonly isolated from the oropharynx of normal cats. The role that Mycoplasma plays in feline URI has not been fully established. Mycoplasma is passed from cat to cat via direct transmission, with minimal transmission via fomites. It does not survive well in the environment and it is killed by routine disinfection. Routine disinfection and timely isolation of symptomatic cats is best to control this disease in the shelter.
Most cats with signs of upper respiratory disease suffer from bouts of sneezing and runny eyes. In most cases, shelters do not bother to distinguish between the different disease causing agents. However, it is important to make the distinction in order to design effective control measures, such as vaccination or treatment protocols.
Diagnostic testing should be undertaken under the following circumstances: when signs persist for over a month; signs are unusually severe or frequent; prior to treatment with steroids; and for liability issues.
The lethargy, sneezing, ocular and nasal discharges may be worse with herpes than the other diseases. Herpes is also accompanied by fever, depression, loss of appetite, eye ulcers and drooling.
Calici virus produces oral ulcers and lameness. These may be the only signs or they may be seen in combination with the same signs as herpes, only milder. There is a virulent systemic calici virus syndrome that causes sudden death in vaccinated adult cats as well as kittens and other animals that would ordinarily be considered protected. A description of the syndrome can be found at the website managed by the University of California Koret Shelter Medicine Program.
Chlamydophila produces a serious conjunctivitis (eye infection), accompanied by mild sneezing. This same organism may cause conjunctivitis in humans.
Bordetella is still being researched. It is believed to cause fever, sneezing, nasal discharge, enlargement of the lymph nodes found under the throat and loud, harsh lung sounds. Coughing may also be observed.
This bacteria most commonly causes ocular signs including ocular discharge and swelling of the conjunctiva.
Diagnosis is generally made based on the clinical signs. Cultures from the mouth, throat, eyes or nose may be sent to the laboratory for confirmation. There are PCR diagnostic kits available from Idexx and Zoologix that provide a feline upper respiratory diagnostic panel.
Treatment for the viral diseases is symptomatic. Isolation is essential if cats with URI are to be treated in the shelter, but placing infected animals in foster care is a better management strategy. Good nursing care (wiping away ocular and nasal discharges, force-feeding, keeping warm, etc.) is essential for the comfort of these animals.
Broad-spectrum systemic antibiotics to protect against secondary bacterial infections may be necessary because of the increased risk of exposure in shelters, but they should generally be reserved for animals with purulent ocular and nasal discharges, anorexia, depression, dehydration, etc. Tetracycline, doxycycline or Clavamox are the drugs of choice to use against secondary bacterial invasions as well as against bordetella, chlamydophila and mycoplasma. Doxycycline is less likely than tetracycline to cause yellow staining of the teeth in younger animals. However, doxycycline can result in esophageal stricture, so it must be used with caution.
Ophthalmic ointment may be needed in some cases. The ophthalmic ointment should contain an antibiotic but NOT a steroid (as a cat may have a corneal ulcer which can be made worse by the use of a steroid ointment in the eye). Examples of ophthalmic ointments recommended include Terramycin, Chloramphenicol, and triple antibiotic ophthalmic ointment.
Fluid therapy may be necessary in severe cases. Antiviral drugs may be necessary in the form of eye drops for herpes viral-induced eye lesions. Cats who are unable to smell their food as a result of the infection may lose their appetite and refuse to eat, so they must be encouraged by offering foods with strong aromas, baby foods or other soft and blended foods. It may be necessary to place a nasogastric tube to force feed them if they continue to refuse to eat. L-lysine can also be used as a nutritional supplement to decrease the severity of symptoms of feline URI. Steam inhalation or nebulizers may also be helpful.
Shelters must consider carefully the resources they have available and the risk to healthy cats when undertaking treatment. A cat who needs only minimal treatment to recover from an upper respiratory infection may pass it on to another cat who requires intensive care therapy. Once the shelter has run out of space to isolate sick animals or place them in foster care, it may be necessary to consider euthanasia to protect the lives of the rest of the animals.
It is critical to disinfect the environment to control any disease outbreak even if the pathogen does not survive long term outside the hostís body. Except for calici virus, the respiratory pathogens are all fairly susceptible to chemical destruction:
Cleaning protocols for cats have changed dramatically over the past few years. Because it is well known that herpes virus reactivates with stress, any cleaning protocol must strive to minimize stress to cats. Studies have shown that the stress to cats that results from simply moving them from cage to cage can result in herpes reactivation.
New recommendations are to leave cats in their enclosures for the duration of their stay, and spot clean their cages, reserving disinfection for when a new animal is placed in the cage. Alternatively each cat can be assigned an adjoining cage and they can just move from one cage to the other while their cage is cleaned. The least desirable but still acceptable option is to assign each animal a carrier and place the cat in the same carrier each time she is removed from her cage while it is cleaned. No other cat may be placed in that carrier. For spot cleaning, the water bowls, food dishes, and litter boxes are removed from the cage and replaced with disinfected items. The cage is simply wiped down only in areas of visible soiling.
The entire cage is cleaned with soap and hot water, including the bars in the front, sides, bottoms and tops and disinfected whenever a new resident is introduced. The disinfectant should be applied and allowed contact with the surface according to the manufacturer's recommendations, and then rinsed. The cage should be completely dry before the cat is placed in it.
Sodium hypochlorite, or household bleach, is one of the most effective and inexpensive disinfectants available for shelters to use to kill calici virus as well as the other respiratory pathogens. If diluted 1:32 with warm water, it is less likely to be corrosive to the cage surfaces or act as an irritant to the cat's mucus membranes. Trifectant or potassium peroxymonosulfate is another excellent product to use for cleaning cat cages. It reliably kills parvo and calici virus, is easy to mix and use, and has the advantage of having some detergent properties and of being less irritating to mucus membranes and less corrosive to metal.
Staff, volunteers and the public should be instructed to avoid handling or touching animals during outbreaks especially. They should wash their hands thoroughly after each contact and wear protective garments.
Cage placement and ventilation have a lot to do with the spread of disease. A cat's sneeze can travel about 3-4 feet, so it is important to have cat cages at least 4 feet apart if they are facing each other. Shelter traffic patterns should place as much distance as possible between sick wards and healthy ones. Staff who clean and work in several areas should start in the areas with healthy juvenile and susceptible animals and end in the areas with diseased animals.
Lack of adequate ventilation also plays a key part in disease spread. If an air exchange system is employed, there should be a minimum of 12-15 air changes per hour, preferably with outside air. If not, circulation patterns should go from healthy areas and kitten areas to sick areas. HEPA filters may be helpful in refreshing the air, but should not be relied on to counter inadequate ventilation systems. Avoid ozone and ion generators.
Fresh air is also extremely valuable in reducing incidence and severity of feline URI in shelters. Ideally, isolation areas as well as cat holding areas should have windows with screens that open to the outside, and these windows should be open when weather permits.
Disease Outbreak Management
The following other measures should help prevent and minimize the impact of upper respiratory infections:
Lila Miller, DVM, is Vice President of ASPCA Veterinary Outreach.Photo Credit: Dr. Kate Hurley