Review of the epidemiological basis of animal quarantine, the three main regulatory models (Australia/NZ, EU/UK, USA), the technical causes that trigger or prolong it, and the current CDC Dog Import Rule framework.
The terms quarantine and isolation are often used interchangeably in everyday animal transport language, but they designate distinct epidemiological realities.
Isolation: the separation of an individual with confirmed or highly probable disease from the rest of the susceptible population. Its purpose is to interrupt active transmission of an already identified infectious agent. Isolation is a response measure to a known event.
Quarantine: the restriction of movement of individuals who have been exposed to an infectious agent, or who come from an environment where that agent circulates, but who do not have confirmed disease at the time of the measure. Its purpose is to create an observation period that allows detection of the development of clinical signs before the individual comes into contact with a susceptible population. Quarantine is a precautionary measure against a probable, not confirmed, risk.
In the context of international companion animal movement, destination quarantine has an additional function: it is the period during which health authorities can verify documentation, carry out complementary diagnostic tests, and execute preventive treatments that could not be sufficiently verified at the point of origin.
Quarantine in companion animal importation does not exist because dogs and cats individually represent an elevated health risk. It exists because mass and continuous movement of animals across borders creates, in statistical terms, a non-negligible probability of introduction of infectious agents into territories where those agents are not present or have been eradicated.
The central concept is that of population risk threshold: the level of probability of introduction of a pathogen that a State considers acceptable. Countries with greater vulnerable endemic biodiversity, with more exposed agricultural economies, or with a history of costly eradication of diseases such as rabies, set lower thresholds and apply stricter quarantine measures.
Of all the infectious agents whose introduction quarantine systems seek to prevent, rabies occupies a central position. Dog-Mediated Rabies Virus Variant (DMRVV) is the variant that regulatory systems identify as the primary risk in dog importation from certain geographic origins. A country’s risk classification is inherently unstable: a territory can be reclassified following an outbreak. For this reason, no reference document can assert the current risk status of a specific country: this information can only be obtained at the official primary source at the time of use.
The Department of Agriculture, Fisheries and Forestry (DAFF) applies a biosecurity protocol for dog and cat importation that is, by design, the most demanding among developed countries. In the Australian model, Post-Entry Quarantine (PEQ) is a structural component of the import system in force at the date of consultation, regardless of documentation quality or country of origin. It is not a consequence of non-compliance: it is a structural requirement. The difference between a perfect file and one with errors is not whether the animal passes through quarantine — it always does — but the duration of that quarantine and the complexity of the protocol applied.
Australia classifies countries of origin into groups according to their health risk profile. Countries not included in any approved group cannot export animals directly to Australia: the animal must have resided for a minimum established period in an approved country before being able to start the protocol. Verification of which group the country of origin belongs to must be done on the official DAFF website, as the classification can change.
The Ministry for Primary Industries (MPI) applies the Import Health Standard (IHS) for dogs and cats, a protocol that in several respects exceeds Australian requirements. Post-entry quarantine is mandatory and structural, not conditional.
One particularity of the New Zealand system: the microchip must be implanted before the sample for RNATT is taken, not only before rabies vaccination, as per the Import Health Standard in force at the date of consultation. This requirement is a documented source of error in files prepared without verifying the current IHS. Quarantine duration can be extended if clinical signs are detected during the stay, if diagnostic test results are inconclusive, or if antiparasitic treatments were not executed within the exact time windows specified by the IHS.
The EU framework does not contemplate routine quarantine: an animal that meets all requirements enters without a mandatory observation period. However, Article 35 establishes the measures when an animal arrives without meeting the requirements:
Quarantine in the EU is the consequence of error, not the standard procedure.
The Pet Travel Scheme allows entry without quarantine when the requirements of the Animal Health Certificate (AHC) are met. When an animal arrives without meeting them, the authority may impose quarantine of up to four months in approved facilities. The full cost is the owner’s responsibility.
Since August 2024, the current CDC regulations state that all dogs entering the USA must comply: be over six months of age, be microchipped (chip implanted before any rabies vaccine to be relied upon in the process), and complete the CDC Dog Import Form online before arrival. This last condition — the mandatory digital form for all dogs — is the most frequently ignored by owners who incorrectly assume that animals from low-risk countries are exempt.
The CDC establishes a distinction between countries with high DMRVV risk and countries without that classification. This distinction determines whether a dog can enter with standard documentation or must do so under additional conditions including specific supervision facilities (CDC Animal Care Facility, ACF).
For dogs from high-risk countries without a “U.S.-issued” rabies vaccine — administered in US territory by a US-licensed veterinarian, with a USDA-approved biologic, certified before the dog leaves US soil — the animal must enter through an airport that has a registered ACF. The number of airports with ACF is limited; route planning must verify that the entry airport has an active ACF at the time of travel.
Compliance with federal requirements does not exempt compliance with state-level requirements in the destination state.
Domestic cats entering the United States are subject to a different federal regulatory framework. At the federal level, CDC does not require a rabies certificate or form equivalent to the Dog Import Form for cats. However, there are specific requirements of destination states and transport operators, which can be more stringent. Verification of destination state and operator requirements is mandatory.
In all regulatory models there is a common denominator: error at origin. The most frequent causes are:
Inability to read the microchip, or discrepancy between the number in documents and that read on the animal — even by a single digit — triggers an “identity not verified” status. The consequence is retention of the animal until identification is resolved.
RNATT must be performed from a sample taken at least 30 days after vaccination. A sample taken before produces a non-recognised result, requiring repetition of the entire process. In destinations requiring a post-RNATT waiting period, a chronological error can delay travel by three to six months.
Australia, New Zealand and the UK require treatments in precise time windows. A treatment correct in substance but outside the window is not recognised as valid.
Detection of ticks or ectoparasites on the arrival examination frequently extends quarantine in Australia and New Zealand. Biosecurity at origin — environmental isolation of the animal in the weeks before travel — is the most effective preventive measure.
As analysed in the health certificate (Article 10) of this series, internal inconsistencies in the file are the most frequent cause of avoidable quarantine in Models B and C.
Presence of signs compatible with active infectious disease triggers retention protocols in all systems, regardless of file quality. The pre-travel veterinary examination has among its functions the detection of these situations before the animal is in transit.
Quarantine facilities are not environments designed to maximise individual welfare but to guarantee health control. Prolonged confinement activates stress mechanisms described in Articles 7 and 8 of this series: elevated cortisol, altered circadian rhythms, disturbance of appetite and sleep.
Operational quality varies with each country’s regulatory standard and is not uniform globally.
An animal in optimal body condition, with vaccinations up to date and without active chronic pathology, tolerates a quarantine period better than an animal in suboptimal condition. Attention to physical condition, progressive adaptation to the carrier and absence of active pathologies reduce the clinical impact of quarantine.
Approved quarantine facilities are subject to official supervision and must meet minimum standards. Prior communication with the facility, detailed identification of the animal and provision of information on specific needs contribute to a quarantine period with less impact.
5.1 The Australian and New Zealand model is exceptional; most developed destinations (EU, UK, Canada, Japan) do not apply routine quarantine to animals with a complete dossier. Assuming quarantine is universal leads to underestimating the importance of documentation.
5.2 Not every retention is formal quarantine. A certificate with an incorrect field can generate administrative retention of hours, without that constituting quarantine in the technical sense.
5.3 Not every delay is health-related. Delays can have administrative, logistical or operational capacity causes.
5.4 In systems where quarantine is routine, it cannot be avoided; it can be minimised in duration with correct preparation. In systems where it is conditional, it can be prevented almost entirely with a technically correct file.
The veterinarian is responsible for three things: