Australian Quarantine Review Secretariat Australian Quarantine a shared responsibility

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2 ANIMAL PESTS AND DISEASES

The report on animals was completed by Dr A.J. Foreman, a consultant veterinary virologist who is the former head of the diagnostic program at the Australian Animal Health Laboratory. The report examined recent incursions of pests and diseases of animals, including farmed domestic animals (including poultry and bees), pet and recreational animals, free-living and wild animals, zoo animals, and finfish and other aquatic animals.

Although the commissioned report considered incursions of aquatic animals, the lack of readily available and documented information on such incursions has led to an underestimate of numbers of incursions leading to establishment of newly recognised endemic pests and pathogens affecting aquatic animals. Thus no attempt was made to discuss ectoparasites or endoparasites (i.e. external and internal helminths, arthropods and protozoa) of aquatic animals. Similarly, the report noted that there had been a number of such incursions of pathogens of finfish, most of which were discussed under a single heading (on 'agents found in imported ornamental fish'). The report specifically mentions seven species of pathogens and one pest (a snail, Lymnea columella) believed to have been introduced with imported ornamental finfish during the study period. In addition, it includes one recently identified disease of shellfish (i.e. bonamiasis) that has probably been present for many years and may be an endemic Australasian species (or even a new endemic genus). The report also included two other recently identified endemic pathogens of finfish (i.e. epizootic haemorrhagic disease and 'red spot disease'). However, it did not consider other pathogens of aquatic animals, including several recently identified viruses of crustaceans (e.g. viruses of prawns) that are probably also endemic species. The report thus underestimates the total number of incursions leading to establishment and newly recognised endemic pests and pathogens affecting aquatic animals. Similarly, the report underestimates the total number of incursions leading to establishment of pathogens of bees by counting several bee viruses as a single incident (on the grounds that not all are known to have significant pathogenic effects).

2.1 Recent Incursions and Other Detections

The report divided the pests and pathogens of animals into six groups:

· recently introduced pests and pathogens;
· pests and pathogens established but not detected before 1971;
· agents associated with human disease;
· pests and pathogens detected in post-entry quarantine;
· recently recognised endemic pests and pathogens; and
· incompletely defined incidents.

2.1.1 Recently introduced pests and pathogens

The report identified 11 incursions of pests and pathogens that have occurred over the past 25 years. Two (Asian honeybee and varroa mite) were the result of natural migration. One (contagious equine metritis) has since been eradicated. One introduction (rabbit calicivirus disease) was deliberate in intent although not in the timing or method of its establishment. In three cases (contagious equine metritis, canine parvovirus and moxidectin-resistant Ostertagia spp.) the pests or diseases were new or not anticipated, so that import protocols had not accounted for them. The aquatic incursions (goldfish ulcer disease and Northern Pacific seastar) illustrate two areas that have received much recent attention ¾ imports of ornamental fish and the discharge of ships' ballast water. The method of entry of chalkbrood has not been established definitively. The import of toxigenic Pasteurella multocida, resulting in severe atrophic rhinitis, was arguably avoidable — although, at the time, the complex aetiology of atrophic rhinitis was not completely defined nor was the status of Australian pigs with respect to the contributing pathogens. A similar situation existed with equine herpesvirus 1.

2.1.2 Pests and pathogens established but not detected before 1971

The report identified 13 pests or pathogens that have been detected in Australia over the past 25 years but have almost certainly been present for much longer — either continuously or intermittently — but not previously detected. Five of the agents (bluetongue viruses, bovine lentivirus, Trichinella pseudospiralis, equine arteritis virus and reticuloendotheliosis virus) do not normally cause disease in Australia, although they are still of importance, particularly with respect to international trade. One of the agents (Babesia equi) has probably since disappeared.

2.1.3 Agents associated with human disease

In recent years, a number humans infested or infected with animal pests or pathogens have been detected entering Australia. All but one case involved people transporting an agent from overseas in circumstances that would be difficult or impossible to prevent. The one exception (Japanese encephalitis) is an insect-borne virus that may not have been detected quickly had it not been for the occurrence of human cases of disease. The report did not attempt to identify other human cases of imported pests or diseases that could affect animals (e.g. Brucella melitensis, the cause of Malta or Mediterranean fever, and Taenia saginata, the pork tapeworm).

2.1.4 Pests and pathogens detected in post-entry quarantine

The report identified 14 incidents with animals in offshore or post-arrival quarantine stations in Australia, or in extended on-farm or zoo post-entry quarantine. Three incidents involved detection of antibody against an exotic disease— and not the presence of disease itself. However, these three incidents had repercussions for trade and illustrate the effectiveness of pre-import testing and the need to review protocol conditions continually. Some findings were fortuitous (e.g. the discovery of ear mites in alpacas and leishmaniasis in a dog in post-entry quarantine), resulting from examination by an alert veterinarian with particular expertise in the condition concerned. Other findings (e.g. African honeybee and screw-worm fly) are examples of border detection by alert quarantine staff.

2.1.5 Recently recognised endemic pests and pathogens

The report identified five diseases that do not represent recent incursions from overseas — equine morbillivirus pneumonia, kangaroo blindness, epizootic haemorrhagic necrosis, 'red spot disease' and chicken anaemia agent (of which the first three have been described only in Australia). They were included because two of them attracted considerable media attention, and at least two of them (equine morbillivirus pneumonia and epizootic haemorrhagic necrosis) had trade implications.

2.1.6 Incompletely defined incidents

The commissioned report identified seven incidents that involved suspected or actual disease that was initially thought to be possibly associated with an incursion of a previously exotic pathogen. It is still not definitely established whether Potomac fever or Lyme disease occur in animals in Australia or whether the serological reactions that have been recorded represent cross-reactions to related agents, possibly of low or no virulence. Viruses have been isolated from cases of ostrich fading syndrome and pilchard deaths, but their role in causing disease has not been established and there was no indication that these agents had been recently imported.

2.1.7 Summary

Table 1 summarises incidents relating to exotic or new pests and diseases of animals between 1971 and 1995. The report identified 64 such incidents and noted trends need to be interpreted with care. Several factors need to be considered in attempting to determine both the number of incursions (and establishments) and any trends during the study period:

· what constitutes an incursion (e.g. whether or not detection of a new serotype of bluetongue virus counts, given that other serotypes are already present in Australia; or whether four imported cases of human infestations with exotic flies counts as one or four incursions);
· which of the report's six categories are included in the total (e.g. including the 11 recently introduced pests and pathogens, or including these and the five agents associated with human disease, or including both of these categories plus the five recently recognised pests and diseases gives a 'total' of 11, 16 or 21, respectively); and
· the effect of recent improvements in diagnostic methods (e.g. allowing for the first time the detection and identification of pests or pathogens already present in Australia, so that apparent trends in 'incursions' over time need to be interpreted with some care).
Table 1: Summary of exotic or new pest and disease incidents affecting animals from 1971 to 1995

	Category
Period	RE	H	N	ND	ID	Q	Total
1971–75	2	–	1	3	–	1	7
1976–80	2	–	1	6	–	2	11
1981–85	–	–	–	1	–	1	2
1986–90	2	2	2	3	3	5	17
1991–95	5	3	1	5	4	9	27
Total	11	5	5	18	7	18	64

Key:
RE Recent establishments: pests and pathogens established after recent incursions

H Human agents: pests and pathogens associated with human infection or infestation

N Newly recognised endemic organisms: endemic pests and pathogens described since 1971

ND* New detections: pests and pathogens established but not detected before 1971

ID Incompletely defined incidents

Q Incursions detected in post-entry quarantine
* Note that ND includes repeat incursions of some agents (18 incursions involving 15 different agents)

2.2 Economic Effects

The report identified little documented information on the cost of recent incursions of pests and diseases of animals. Despite the lack of definitive studies, the report indicates that very few incursions have had significant economic effect — in part because of rapid control and eradication of those that might have had the greatest effect if unchecked (e.g. avian influenza, Japanese encephalitis). Some of the more significant costs identified are:

· avian influenza
Four outbreaks of avian influenza occurred in the period under study. The first outbreak was near Melbourne in 1976 and eradication costs amounted to at least $554 000. The next two outbreaks both occurred near Bendigo. The 1985 outbreak resulted in the slaughter of 111 000 birds and eradication costs of about $2 200 000. The 1992 outbreak resulted in the destruction of 128 000 birds and 540 000 eggs on four properties, with an estimated cost of about $1 340 000. The last outbreaks occurred near Lowood in south-eastern Queensland in 1994, and resulted in the slaughter of 20 000 birds and eradication costs of about $420 000.
· rabies, equine morbillivirus and Japanese encephalitis
Rabies, equine morbillivirus and Japanese encephalitis have each caused the deaths of two people in Australia during the period under study. For equine morbillivirus pneumonia, direct control costs for the initial Brisbane and subsequent Mackay incidents were about $450 000. Costs were associated with the initial identification and subsequent characterisation of the virus, and further ongoing research to determine the epidemiology of this disease. In addition, significant costs resulted from movement control on horses and consequent suspension of racing programs. For Japanese encephalitis, control costs have included vector control programs and vaccination of people in high risk areas in the Torres Strait region.
· bluetongue
The identification of the presence of bluetongue viruses in Australia led to significant effort to investigate the pathogenicity and epidemiology of each serotype. These investigations were needed to assess risks to Australian livestock and to minimise effects on export trade. Ongoing monitoring and research continues to ensure Australia's preparedness for any outbreak of bluetongue disease and provide certification required to ensure continued access to overseas markets. The commissioned report noted that the cost of such monitoring and research is significant, amounting to almost $9 million between 1989 and 1991 alone.

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