Foot And Mouth Disease: Risks Posed By Imported Horses

Concern has been expressed about the possibility that horses imported from countries infected with foot and mouth disease (FMD) may carry the disease into New Zealand. MAF has considered this possibility and has used the following information in support of the actions taken to date regarding horses from such countries.

Currently, horses can come directly to New Zealand only from Australia, Canada, United States, New Caledonia, Cook Islands and the United Kingdom/Republic of Ireland (UK/ROI). Horses from any other country must come via one of the above countries before entering New Zealand. Of these countries, only the United Kingdom and the Republic of Ireland are affected by FMD.

Horses are not susceptible to FMD, i.e. they do not suffer from the disease themselves. The concern that MAF has set out to address is that horses might carry the FMD virus on their bodies, including in their nasal passages, or on gear that arrives with them. There have never been reported cases of international transmission of this virus by horses or their gear, nevertheless, the possibility is sufficient to warrant investigation.

All horses imported from or via the UK/ROI are subject to pre-export requirements, including the following:

• Application must be made to MAF for an import permit to allow horses into New Zealand. This ensures that MAF are aware of any horses coming and can advise the importers of any additional requirements they may need to meet prior to export.
• The horses are kept in isolation for at least 30 days immediately prior to shipment to New Zealand in premises which must comply with the MAF standard for pre-export quarantine premises of livestock. The aim of this isolation is to prevent direct and indirect contact between animals for export and any animals that are not of equivalent health status. These facilities are fenced so that no livestock can approach to within 20 metres of the perimeter and they are cleaned and disinfected prior to each new consignment of animals arriving.
• Transport of horses to the port of departure must be in cleaned and disinfected trucks and, during transport, the horses must not come into contact with animals not similarly certified for export to New Zealand.
• The crates or pens used for transporting the horses to New Zealand must be either new or cleaned and disinfected.
• The horses are subject to inspection by a veterinary officer at the port of arrival.

There has been no scientific work published on the carriage of the FMD virus in the nasal passages of horses, but it is reasonable to extrapolate from work done on humans. Contamination of the nasal passages of humans has been shown to occur in only one set of experiments (carried out in 1970) and that contamination required very heavy exposure to the virus, e.g. examining the head area of pigs clinically affected with FMD. Virus was recovered from the nasal passages of a human 28 hours after exposure. For humans to infect susceptible animals, in the only experiment published, they were required to spend 30 seconds "sneezing, snorting, coughing and breathing" directly into the mouths of susceptible cattle within 20 minutes of initial exposure. Infection did not occur after that time.

Horses are extremely unlikely to come into contact with infected animals as properties containing such animals will be under movement control. Horses for export to New Zealand are held in pre-export quarantine for at least 30 days. Any wind-borne virus that may have been inhaled by the horse in quarantine would be in insufficient concentrations to be infective to other animals.

It should be noted that replication of this virus has never been reported in horses. This means that any virus that might remain in a horse's nasal passages will eventually lose the ability to infect other animals. Survival times for FMD virus in the nasal passage of a horse have not been published, but it is reasonable to assume that it would not be longer than in humans, thus, even if the horse were to inhale the virus prior to leaving the UK/ROI, any virus would lose infectivity in the time taken to fly to New Zealand (about 30 hours). The risk from nasal carriage of FMD by horses is, therefore, considered to be covered by precautions already taken.

Carriage of this virus on various objects, including hair and manure has been studied, although no particular studies relate to horses. MAF considers that the points of concern would be contamination of horses' hooves, hair and gear. MAF now requires that horses and gear accompanying them are cleaned and disinfected, with particular attention being paid to hooves, both before leaving the UK/ROI and upon arrival in New Zealand. All feed and bedding accompanying the horses must be incinerated.

MAF considers that the quarantine and disinfection measures now in place are sufficient to prevent the introduction of FMD into New Zealand by horses. These precautions are very similar to those undertaken by the authorities in the United States and Canada.

Page last updated: 7 August 2008