Richard B. Ford, DVM, MS, Dipl ACVIM
In December of 2000, the American Association of Feline Practitioners and the Academy of Feline Medicine Advisory Panel on Feline Vaccines published the 2nd version of vaccination guidelines for cats. Recommendations of a panel of selected experts in the field of immunology, feline medicine and veterinary law contributed to the development of this document. The current panel report updates information, addresses questions, and speaks to concerns raised by the 1998 report. In addition, it reviews vaccine licensing, labeling, and liability issues and suggests ways to successfully incorporate vaccination protocol change into a private practice setting. Of particular concern to veterinarians are the recommendations for an extended booster vaccination interval (to 3 years) for feline panleukopenia, herpesvirus-1, and calicivirus in adult cats. Furthermore, several recommendations are included in this document based on new information on vaccine efficacy and safety. Principle recommendations on feline vaccination will be reviewed in this presentation.
The overall objectives of vaccination are to vaccinate the largest possible number of individuals in the population at risk, vaccinate each individual no more frequently than necessary, and vaccinate only against infectious agents to which individuals have a realistic risk of exposure and subsequent development of disease. Kittens younger than 16 weeks of age are generally more susceptible to infection than are adult cats and typically develop more severe disease. Thus, they represent the principal target population for vaccination. Maternal antibody interference is the most common reason why some animals are not immunized following vaccination, and is the reason why a series of vaccinations is necessary for kittens younger than 12 weeks of age. Vaccination needs of adult cats should be assessed at least once yearly, and if necessary, modified on the basis of an assessment of their risk.
Feline panleukopenia. Feline panleukopenia is caused by feline parvovirus (FPV). Vaccination against FPV is highly recommended for all cats. Maternal antibody may interfere with immunization when antibody titers are high during the neonatal period. Maternal antibody titers generally wane sufficiently to allow immunization by 12 weeks of age. Immunity conferred by feline panleukopenia vaccines is considered to be excellent, and most vaccinated animals are completely protected from infection and clinical disease. Both serologic and challenge exposure data indicate that a parenteral FPV vaccine induces immunity that is sustained for at least 7 years. Following the initial series of vaccinations and revaccination 1 year later, cats should be vaccinated no more frequently than once every 3 years.
Feline viral rhinotracheitis and feline calicivirus. Feline viral rhinotracheitis, caused by feline herpesvirus-1 (FHV-1), and feline calicivirus (FCV) infection account for up to 90% of all cases of infectious upper respiratory tract disease in cats. Vaccination against FHV-1 and FCV is highly recommended for all cats. Maternal antibody may interfere with induction of a systemic immune response; however, by 12 weeks of age, maternal antibody titers wane sufficiently to allow parenteral immunization. Topically administered (intranasal, conjunctival) vaccines are capable of inducing a local immune response in the face of high maternal antibody titers. Serologic and challenge exposure data indicate that a parenteral FHV-1 and FCV vaccine induces protection that lasts at least 3 years.8,9 Therefore, following the initial series of vaccinations and revaccination 1 year later, cats should be vaccinated once every 3 years. Regardless of the route of administration, FHV-1 and FCV vaccines induce only relative, not complete, protection. At best, these vaccines induce an immune response that lessens the severity of disease; vaccinates are not immune to infection, nor are they protected from all signs of disease.
Rabies. Rabies is transmitted mainly through bite wounds of infected mammals. More cats than dogs develop rabies in the United States. Although vaccine-associated sarcomas have been reported to develop in association with administration of a variety of vaccines, current data suggests they are more frequently associated with administration of adjuvanted vaccines.Inflammatory reactions are commonly observed at sites where adjuvanted rabies virus vaccines have been administered, and concern has arisen regarding the possible association between these reactions and vaccine-associated sarcomas in some cats that may be genetically predisposed to tumor development. With the exception of a recently approved canarypox virus-vectored recombinant feline rabies virus vaccine (PureVax Feline Rabies Vaccine, Merial Ltd), all rabies virus vaccines currently on the market contain adjuvants.
Rabies virus vaccination is highly recommended for all cats. Laws governing the administration of rabies virus vaccines vary considerably throughout the world.
Feline leukemia virus. Feline leukemia virus (FeLV) infects domestic cats throughout the world. Kittens are the most susceptible to infection; resistance increases with maturity. Experimental data demonstrate that kittens younger than 16 weeks of age are most susceptible to infection, with cats older than this being relatively resistant.30 Cats at greatest risk include outdoor cats (free-roaming pets, stray cats, and feral cats). Also at risk are cats residing in open, multiple-cat environments, cats living with FeLV-infected cats, and cats residing in households with unknown FeLV status.
The decision to vaccinate an individual cat against FeLV infection should be based on the cat's age and its risk of exposure. Vaccination against FeLV is recommended for cats at risk of exposure (i.e., cats not restricted to a closed, FeLV-negative, indoor environment), especially those younger than 4 months of age. Vaccination is not recommended for cats with minimal to no risk of exposure, especially those older than 4 months of age.
Chlamydiosis. Chlamydia psittaci is an intracellular bacterial pathogen of the conjunctiva and respiratory tract of cats. The frequency of adverse systemic events associated with C. psittaci vaccines is higher than that associated with other commonly used vaccines. Because signs of disease associated with C. psittaci infection are comparatively mild and respond favorably to treatment and because adverse events associated with use of C. psittaci vaccines are of greater concern than adverse events associated with use of many other products, routine vaccination against C. psittaci infection is not recommended.
Feline infectious peritonitis. Considerable controversy surrounds the ability of the only FIP vaccine to prevent disease. Some studies demonstrate protection from disease while others show little benefit from vaccination. At this time, there is no evidence that the vaccine induces clinically relevant protection, and its use is not recommended.
Dermatophytosis-Dermatophytosis in cats is primarily caused by infection with Microsporum canis. An M. canis vaccine is currently licensed in the US for use as an aid in the prevention and treatment of clinical signs associated with M. canis infection. Vaccination has not been demonstrated to prevent infection or to eliminate M. canis organisms from infected cats. Therefore, routine vaccination against M. canis infection is not recommended.
Bordetella bronchiseptica infection. Bordetella bronchiseptica is a small, aerobic, gram-negative coccobacillus long recognized as a respiratory tract pathogen of several species of animals. A topically administered vaccine to prevent disease caused by infection with B. bronchiseptica has recently been licensed. Efficacy of the vaccine has not been independently evaluated, but in studies conducted by the manufacturer to gain vaccine licensure, vaccinated 4-week-old SPF cats experienced less severe signs of disease than did unvaccinated controls when challenge exposed 3 weeks after vaccination. Routine use of this vaccine is not recommended.
Giardiasis. Infection of cats with the protozoan Giardia lamblia is associated with acute or chronic gastrointestinal disease ranging in severity from subclinical to severe. A licensed vaccine is available in the US as an aid in the prevention of disease associated with G. lamblia infection and reduction in the severity of shedding of cysts. The vaccine is approved for use in cats 8 weeks of age and older. Routine use of this vaccine is not recommended, but because vaccinates had less severe clinical disease and shed cysts for a shorter time, it is reasonable to consider vaccination as part of a comprehensive control program in environments where exposure to G. lamblia is clinically significant.
1. 2000 Report of the American Association of Feline Practitioners and the Academy of Feline Medicine Advisory Panel on Feline Vaccines. (74 References) May be obtained by writing: AAFP/AFM, 530 Church Street, Suite 700, Nashville, TN 37219, USA