Import Risk Analysis - Biosecurity New Zealand

Common agents that are universal in distribution and endemic throughout New Zealand have
been excluded from further consideration. Because more pathogenic exotic strain variations of
the major endemic diseases are known to exist overseas, these infectious agents are retained
as potential agents of concern. Apart from Mycobacterium bovis, no other endemic organism
that is subject to official control has been identified for retention.
Some organisms that appear in the preliminary hazard list are clearly not hazards. Brief
information indicating why these can be removed is given below.
Feline spongiform encephalopathy (FSE) belongs to the transmissible spongiform
encephalopathies (TSEs) and their aetiological agents are generally considered to be prions.
These are infectious protein agents that affect the central nervous system causing
neurodegenerative disease in humans and animals (European Commission 2000). FSE was
first recognised during the bovine spongiform encephalopathy (BSE) epidemic in Britain. The
first case in a felid was diagnosed in 1990 (Leggett et al 1990). There is no evidence that FSE
occurs in any manner other than through ingestion of contaminated food containing the BSE
agent. TSEs have long incubation periods and development of clinical signs in the cat takes
about five years. There is no evidence of vertical transmission of TSEs in the cat.
Approximately 90 cases of FSE were reported worldwide to 2004, predominantly from the UK
(Vandevelde & Greene 2006). FSE has probably now disappeared, since world-wide strict
measures are in place to exclude BSE infected cattle from entering the food chain. There have
been no reports from the UK since 2001. TSE has not been reported in the dog (Vandevelde &
Greene 2006). The likelihood of importing an infected cat is remote. In addition FSE is not
contagious and cats are extremely unlikely to end up in the food chain. Therefore the likelihood
that the agent could be imported and transmitted to other animals is negligible.
Coronaviridae can be removed from the initial hazard list. Feline coronaviruses associated with
feline infectious peritonitis are present in New Zealand. However the family Coronaviridae
contains the contagious exotic disease of pigs, transmissible gastroenteritis that is caused by the
transmissible gastroenteritis virus (TGEV). Pigs are the only animals for which TGEV is
pathogenic (Paton 2004). The cat and dog have been described as being able to be infected
experimentally but without clinical signs (Larson et al 1979). The possibility that any other
species than the pig could be a natural source of infection is considered negligible.
Acanthamoeba species are ubiquitous, omnipresent and abundant free-living amoebas found
in water, soil, and the atmosphere. Several Acanthamoeba spp. are rarely pathogenic to
animals and humans who are immunocompromised. No transmission of infection between
hosts is known and infections are thought to originate solely from environmental sources
(Greene & Howarth 2006). Acanthamoeba are therefore not considered to be potential
hazards.
The protozoal tick-borne organism Cytauxzoon felis was discarded from the preliminary
hazard list as it has no zoonotic potential and primarily affects American wild cats such as the
panther and bobcat (Rotstein et al 1999). Inadvertent infection in the domestic cat is thought
to be through the tick Dermacentor variabilis or from fighting with wild cats. The domestic
cat is regarded as a dead-end host, with rapid death resulting from infection (Greene et al
2006). The likelihood of importing an infected cat is low and establishment in New Zealand
would not be possible without the tick vector and wild cat reservoir hosts.
8 • Import risk analysis: Cats, dogs and canine semen MAF Biosecurity New Zealand