Livestock quarantine: A critical tool for biosecurity and animal health

Quarantine

It’s a word that was in the media a lot due to COVID, but it remains one of the simplest and most effective ways that you can prevent unwanted pests or diseases from making their way onto your property. It can be applied to all livestock species and to most pests or diseases from lice or resistant worms to avian influenza. Quarantine involves holding animals in a specific area where the pest or disease of interest cannot spread to other animals while a period of time passes – 3 weeks is a general rule of thumb but see below!

The quarantine area may be as simple as a dedicated paddock or it may require more stringent containment, especially if it can be spread via the air or by third parties – i.e. by ‘vectors’ such as insects or wild animals. You need to ensure that pathogens do not have a way to spread outside of the quarantine area. This might include indoor containment to prevent airborne spread, removal of ‘fomites’ (such as sheep fleece), secure disposal of faeces/ litter, or use of a securely-fenced dedicated paddock.

Quarantine may need to be applied in many circumstances, such as purchase of new stock, returning stock from a show, or returning them from agistment.

Obviously, the specific requirements vary a lot based on individual conditions, so the below is general advice. Please refer to your industry’s biosecurity manual or disease specific information for more specific details.

Infectious diseases

Infectious diseases are caused by a pathogen such as a virus which directly causes a disease. This includes well known ones like foot and mouth disease (FMD) and highly-pathogenic avian influenzas (HPAI). An infected animal will not show any clinical signs when recently infected, but as the virus multiplies within them, the animals will start to ‘shed’ virus in their bodily fluids. This may or may not be associated with the animal showing obvious clinical signs.

In some cases, particular species are known to be ‘Typhoid Marys’ who do not show many clinical signs at all but are still infectious (e.g. sheep with FMD). Quarantined animals therefore need regular health checks, with care taken for that person to not risk carrying infection away from them.

The time it takes for a newly-infected animal to show clinical signs and to shed virus is called the ‘incubation period’. Exactly how the infected animal sheds pathogen varies by disease (e.g. faeces, respiratory drops, semen).

The length of time animals should be kept in quarantine should be longer than the time it would take for a newly-infected animal to show clinical signs. This means that new ones would become visibly sick, and you can treat them accordingly, while avoiding introducing their infection to the rest of the herd or flock.

Some infectious diseases are such ‘slow burners’ that quarantine is of little use. For some of these, Market Assurance Programs or schemes help to fill this gap -e.g. Johne’s disease or for ovine brucellosis.

Problem parasites

Parasites, while an everyday part of managing livestock, can still cost your animals’ health. Examples could be cattle returning from agistment heavily infested with lice, sheep carrying chemical-resistant worms in their guts, or cattle with attached ticks. In such ways problem parasites can arrive on your property – such as resistant Barber’s pole worms – or undo any recent treatments that you’ve invested in.

Generally, animals in quarantine should be treated and kept separate from others until the last of the parasites of concern have died.

For lice, this will largely depend on the chemical used. Read the label carefully! You may need to quarantine them for weeks. For example, if the label says, “Do not mix treated with untreated animals” (which may include lambs, if ewes are due to lamb in a few weeks), this means that the product kills living lice but not their eggs, which will survive and hatch out to infest the untreated animals (including newly-born lambs). This is why missing treatment of just a few animals in a mob (or treating too close to lambing) can allow a louse problem to re-explode a few weeks after treatment and give the impression that it hadn’t worked.

For worms, administer a quarantine drench and hold the animals for several days to allow their faeces to become free of worm eggs. That ‘dirty’ paddock should then only be used by animals which don’t share worms (e.g. cattle could follow sheep quarantined while clearing out Barber’s pole).

ParaBoss has more detail on parasite quarantine periods for worms in cattle, sheep, and goats; and lice in cattle and sheep:

How Can Drench-Resistant Worms Be Kept Out of Your Property? – Sheep – WormBoss

Keep Lice Out of Cattle – LiceBoss

Feral / wild animals

A final note! One of the ways that feral and wild animals pose a threat is that they, by definition, are not quarantined and can carry disease anywhere that does not have appropriate barriers/fencing in place. It is good practice to ensure that feral animals cannot interact with your stock or their food or water supply. This will also set you in good stead to be safe should there ever be an emergency animal disease outbreak of something like African swine fever, FMD, or HPAI among the wild animals near your property.