Vaccination, Zoonoses and Public Health

Community-Based Solutions to Managing Companion Animal Populations

Dog or cat populations that are allowed to roam and reproduce freely have a significant human health component. Zoonoses are diseases that are transmissible from animals to humans, such as Rabies. Roaming, unvaccinated animals are at the highest risk of infection.

It is necessary to reduce the risk a particular animal population presents to human health and to the health of other animals. Zoonotic diseases are often the primary cause for concern with regard to roaming animal populations, particularly with local governments who have a responsibility for public health. Because rabies is a fatal disease, with dogs being the most common vector for transmission to humans, rabies control is often a major motive for dog population management.

Several issues need to be considered when exploring these factors. The importance of zoonotic control should not be played down to relevant stakeholders, such as public health officials. It is important to explore ways that effective zoonotic control can be achieved while remaining neutral, or even positive, towards animal welfare. Zoonoses are a concern for the general public. Controlling zoonoses and providing tangible evidence of this control to the public may help to increase confidence in a management plan. In some situations it may be advisable to introduce improved zoonotic control to restore public confidence first and then follow with other elements of companion animal population management, such as sterilization or improved health care. However, a comprehensive program of population management including simultaneous zoonotic control is the ideal option.

Preventative veterinary treatments should be provided to protect the health and welfare of companion animals and to reduce the incidence of zoonotic diseases. These treatments should be offered in conjunction with education about the other aspects of responsible ownership. Local veterinary communities should be consulted regarding the prevalence and distribution of infectious diseases and parasite infestations, so that a preventative treatment protocol can be tailored to a particular area, local circumstance and level of need.

Regular vaccination and parasite control is likely to improve the health of animals, and can lead to increased reproductive success. Therefore, a sterilization intervention must be offered in conjunction with any preventative treatment provision. As with sterilization, preventative treatments can be used to encourage owners to accept the value of general veterinary treatment and population management tools. Wherever possible, the local veterinary infrastructure should be involved in providing preventative treatments, to ensure ease of access and continuity of treatment in the long term.

In any location where expert opinion advises rabies control is necessary or desirable, healthy animals should be vaccinated at least once. A booster at one year followed by boosters every one to three years or as required by local ordinance and the vaccine manufacturer, is indicated.

Healthy cats are commonly vaccinated against five commonly encountered diseases:

  1. Feline Herpes Virus (Rhinotracheitis)
  2. Feline Calicivirus
  3. Feline Parvoviral Enteritis (Feline Panleukopenia or feline distemper)
  4. Feline Leukemia
  5. Rabies

Healthy dogs are commonly vaccinated against six commonly encountered diseases:

  1. Canine Distemper
  2. Canine Parvovirus
  3. Canine Adenovirus Type 2
  4. Canine Parainfluenza Virus
  5. Bordetella Bronchiseptica
  6. Rabies

Animals managed by TNR or similar interventions may not receive more than one vaccination, due to the logistical problems of retrapping at a later date, but this may be sufficient to provide immunity for their lifespan, assuming a shorter lifespan and if a vaccine providing several years of immunity is available and used.

It is important to remember that vaccination results in a herd immunity effect, which is the point at which the proportion of immune individuals in the group is so high that the disease cannot spread through the population.

Parasite control

Parasitism is the most common transmissible problem of companion animals. Common parasites include fleas, ear mites, ticks, intestinal ascarids (roundworm such as Toxocara cati), cestodes (tapeworms such as Dipylidium caninum and Taenia taeniaeformis) and hookworms (Ancylostoma and Uncinaria spp).

The choice of anti-parasitic product will depend on the parasites to be treated, the route of administration that is possible, the availability and cost of the product and the characteristics of the local population.

Public Health and “One Health”

One Health is the integrative effort of multiple disciplines working locally, nationally, and globally to attain optimal health for people, animals, and the environment. Together, the three make up the One Health triad, and the health of each is inextricably connected to the others in the triad. Understanding and addressing the health issues created at this intersection is the foundation for the concept of One Health. Veterinary medicine, public health and local government all play a critical role in the health of animals, humans, and the environment.

As the human population continues to increase and expand across our world, the interconnection of people, animals, and our environment becomes more significant and impactful. The importance of One Health is highlighted by many factors in our world today:

  • The world’s total population exceeded 7.7 billion people in 2019, and it continues to climb.
  • As our population expands geographically, the contact between human and animal habitats increases, introducing the risk of exposure to new viruses, bacteria and other disease-causing pathogens.
  • Advancing technologies and science-based evidence is increasing the awareness, knowledge, and understanding of the interdependency of the health of humans, animals, and the environment.
  • The human-animal bond continues to grow throughout societies.
  • It is estimated that at least 75% of emerging and re-emerging diseases are either zoonotic (spread between humans and animals) or vector-borne (carried from infected animals to others through insects).
  • Vigilant protection of our water sources, food and feed supplies from food-borne diseases and contamination is critical for human and animal health.​​


Rabies from (2018).

Community Cats and Public Health from (2017).

Webinar: Shelter Vaccination Protocols from (2014).

Zoonoses-Shared Disease Agents of People and Pets from (2016).