Bordetella pneumonia in a person from dog vaccine
An article in an upcoming edition of Transplant Infectious Disease (Gisel et al) describes a case of Bordetella bronchiseptica pneumonia in a person who had received a kidney and pancreas transplant. This person had to board her dogs at a veterinary clinic while she was hospitalized for a bowel obstruction that occurred after surgery. The clinic required her dogs to be vaccinated against Bordetella bronchiseptica, a cause of canine "kennel cough." They were vaccinated intranasally (i.e. up the nose) with a modified live vaccine comprised of live B. bronchiseptica that is modified so it is unlikely to cause disease but can still induce a good immune response. The owner developed pneumonia after returning home and B. bronchiseptica was isolated. Specific testing was not performed to confirm that the vaccine strain caused disease, so it's possible that she was infected by the normal (i.e. "wild type") B. bronchiseptica (which still would have presumably come from the dogs).
Immunosuppressed individuals are at high risk for infection by microorganisms that usually don't cause disease in otherwise healthy people. Bordetella bronchiseptica is a good example of this. Care should be taken around pets by anyone whose immune system is compromised. Here are some recommendations pertaining to kennel cough vaccination:
- Immunosuppressed individuals should not receive modified live vaccines themselves, and it is probably prudent to extend this recommendation to avoid modified live vaccination of their pets with vaccines like the Bordetella (kennel cough) vaccine.
- If vaccination for kennel cough is required for entering a kennel or vet clinic, an exemption should be sought because of the potential risk to the immunocompromised person.
- If vaccination must be performed, injectable vaccination is preferred. It doesn't produce as good immunity in the dog compared with intranasal vaccination but the risks to the immunocompromised owner would be much less.
- If intranasal vaccination with modified live kennel cough vaccine is used, immunocompromised owners should not be in the same room during vaccination. They should avoid contact with the dog's mouth, nose and face for at least a few days after vaccination and should wash their hands (or use a hand sanitizer) regularly after contact with the dog.
- If respiratory disease develops in someone exposed to a dog recently vaccinated against kennel cough, the potential for vaccine-associated disease should be mentioned to the physician.
Can I get kennel cough from my dog?
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Kennel cough is a highly infectious respiratory disease in dogs. The disease got its name because infection and outbreaks often occur in kennels, where many dogs from various backgrounds are mixed together. Some of the dogs in kennels may be carrying infectious diseases, and other dogs may be very susceptible these diseases - putting them all together in what can be a stressful environment for any dog creates a recipe for infection.
Kennel cough itself is more of a syndrome than a specific disease. It can be caused by a few different bacteria and viruses (and combinations thereof) that produce the same type of clinical signs. These pathogens include Bordetella bronchiseptica, Mycoplasma, canine parainfluenza virus, canine adenovirus-2, canine distemper virus and canine herpesvirus. Of these, only Bordetella bronchiseptica is a potential concern in terms of transmission to humans. Bordetella bronchiseptica can cause respiratory infections in people, but this is probalby quite rare and largely confined to high-risk individuals, like those with a weakened immune system, who have had their spleen removed, who already have underlying respiratory disease of another kind, and pregnant women. The evidence of transmission of B. bronchiseptica from pets to people is relatively weak and circumstantial - it is not clear whether the human Bordetella infections in these cases were truly due to contact with a pet.
In households with individuals with a weakened immune system (e.g. HIV/AIDS, transplant or cancer patients), some measures that can be taken to help reduce the risk of transmission of Bordetella from pets include:
- Avoid boarding dogs at kennels or veterinary clinics. If boarding cannot be avoided, ensure that dogs have been properly vaccinated against Bordetella bronchiseptica, and that the kennel or clinic requires all other dogs boarding there to be vaccinated as well.
- Avoid obtaining a dog directly from from an animal shelter.
- Wash your hands regularly after handling any dog, particularly if you've touched the dog's nose or mouth.
- Don't allow dogs to lick your face or hands.
The Bordetella vaccine for dogs is a modified live vaccine, meaning that a live but less virulent (pathogenic) form of the bacterium is administered to "prime" the immune system against regular Bordetella. Concern has been raised by some people that exposure to the vaccine strain could actually cause disease in high-risk individuals, whose immune systems might be unable to fight off even this "weaker" version of the bacteria. It is unclear whether exposure to the vaccine strain actually poses any risk. Nonetheless, it is reasonable to pay extra attention to avoiding contact with the dog's face for a day or two after vaccination. Also, it is probably wise for immunocompromised owners to not hold the dog when it is being vaccinated, in order to reduce the risk of exposure to the vaccine.
