External parasite treatment: the 21-day rule and how the days are counted

Last verified: 2026-08-25

The answer

A government approved veterinarian must treat your pet with a product that kills ticks and fleas on contact, and the treatment must remain effective against new infestations until the date of export, repeated as the manufacturer’s directions require.

The window is not the same for both species:

If you are moving a dog and a cat together, the dog’s window governs the pair.

How the days are counted

The department states its convention, and it applies to every preparation, not only this one:

All preparations are calculated from the date of export, local time in the country of export. For calculating timeframes, the date of the treatment or preparation counts as day 0.

So the counting is exclusive of the treatment day. If you have been assuming day 1 is the treatment day, every date you have calculated is one day optimistic — and if your export and your veterinarian are in different time zones, the export country’s local time is the one that counts.

The re-treatment trap

The treatment has to stay effective until departure, so the product’s own interval can create a second deadline. The department’s example:

If the manufacturer specifies a 28-day re-treatment interval, an animal treated on 1 January must either be re-treated by the vet on 29 January, or be exported before 29 January.

So a product with a short interval and a travel date that slips by a few days means another veterinary visit — not a rescheduling inconvenience, a compliance requirement. Ask your veterinarian for the re-treatment interval at the first appointment, and write both dates in your plan: earliest export, and the date protection lapses.

Which products count

Acceptable: a product that kills ticks and fleas on contact.

Not acceptable:

• Oral products such as NexGard and Bravecto — they require the tick or flea to bite the animal before taking effect, which is not “on contact”;
• Tick collars — they can be removed, and their effectiveness is reduced in some weather conditions.

These are widely used, effective products that many owners already have at home, and they do not satisfy this requirement. Confirm the product with your approved veterinarian rather than continuing whatever your pet is already on.

Finding a parasite restarts the treatment

At every visit after treatment has started, the veterinarian must examine the animal for external parasites. If fleas or ticks are found, they must be removed and the treatment restarted.

A restart means the whole window runs again from the new day 0 — 30 days for a dog, 21 for a cat — so a single tick found at a late appointment can push your export date back by a month. Between visits, keep the animal away from the environments that make that likely.

What this page does not tell you

• Which specific products are approved in your country. The department publishes a list of acceptable treatments; your approved veterinarian applies it.
• Dosage or application method — the manufacturer’s directions and your veterinarian govern.
• What happens if parasites are found at the border, which can lead to treatment, additional testing or an extended quarantine stay at your cost.