NAca Section 2.pmd - Maryland Department of Natural Resources

10
Examples of TAAPs/TAADs Affecting Asian Aquaculture
Viral nervous necrosis (VNN) is a serious disease of larval and juvenile marine fish. It has been reported
from at least 22 fish species from 11 families, with greatest impact among sea bass, grouper, parrotfish,
puffer and flatfish (OIE 2002). First described in Japanese parrotfish (Oplegnathus fasciatus) in Japan
(Yoshikoshi and Inoue 1990) and barramundi (Lates calcarifer) in Australia (Glazebrook et al. 1990),
VNN has since been recorded in the Asia-Pacific Region in Indonesia, Korea RO, Philippines, Singapore,
Chinese Taipei and Thailand (APEC/AAHRI/FHS-AFS/NACA 2001). Its world-wide distribution also
includes the Mediterranean, Scandinavia and North America (Nakai et al. 2001).
Epizootic ulcerative syndrome (EUS), defined as “a seasonal epizootic condition of freshwater and estuarine
warm water fish of complex infectious aetiology characterized by the presence of invasive Aphanomyces
infection and necrotising ulcerative lesions typically leading to a granulomatous response” (Roberts et al.
1994), remains an international problem. EUS is known by a number of names, such as mycotic granulomatosis
(MG) in Japan (Egusa and Masuda 1971, Hatai 1980), red spot disease (RSD) in Australia
(McKenzie and Hall 1976, Callinan and Keep 1989, Callinan et al. 1989, Fraser et al. 1992), and ulcerative
mycosis (UM) in the United States (Noga and Dykstra 1986). However, the syndrome is now
believed to have a single causative agent - the putative Aphanomyces (Aphanomyces invadans/piscicida)
(Callinan et al. 1995; Lilley and Roberts 1997; Lilley et al. 1997a,b, 1998; Chinabut 1998; Blazer et al.
2002). Despite almost three decades of scientific research, much controversy still exists regarding the
infectivity of the fungal pathogen, the involvement of various bacterial and viral agents, it’s epidemiology
and the proper name of the organism. Lilley et al. (1998) confirmed histologically that more than 50
species of fish are affected by EUS. A number of important cultured species (e.g., tilapia (Oreochromis
niloticus), milkfish (Chanos chanos), common carp (Cyprinus carpio), silver carp (Hypophthalmichthys
molitrix) and Japanese eel (Anguila japonica) appear to be resistant (Kumamaru 1973, Bondad-Reantaso
et al. 1992, Wada et al 1996, Khan et al. 1998).
Suspected koi herpes virus (KHV) is a newly emerging finfish disease in the region, causing large-scale
mortalities of koi and common carp in Indonesia in 2002 (NACA 2002). At the request of the Government
of Indonesia, an International Emergency Task Force was formed by NACA in June 2002. The Task Force
recognized the important role that KHV played in the outbreak (based on analogy with other KHV outbreaks
elsewhere and positive detection by polymerase chain reaction (PCR) from all case samples);
however, due to an absence of typical KHV pathology, failed viral isolation and non-observance by electron
microscopy of typical virions, it was not confirmed that the agent responsible was KHV. This suspected
introduction of KHV to Indonesia could have a major impact on trade, as it will affect the international
and domestic movements of high-value ornamental koi carp and of common carp, which is a regionally
important food fish. KHV has been reported in many countries, such as Israel (Ariav et al. 1999), the
United Kingdom, Germany, the Netherlands, Belgium, Denmark (OATA 2001, Ariel 2002) and the United
States (Hedrick et al. 2002). The principal mode of transfer is the through the ornamental fish trade.
Shrimp aquaculture has its share of newly emerging diseases. These include the spawner mortality virus
(SMV) in Australia reported and described by Fraser and Owens (1996) and Owens et al. (1998) and the
Mourilyan virus (MoV), a new bunya-related virus affecting penaeid prawns in Australia and possibly
elsewhere in the region (Cowley et al. 2002). White spot disease (WSD) remains the most serious disease
of cultivated shrimp in the world (Flegel 1998), affecting 13 countries in the Asia-Pacific Region and ten
countries in the Americas. The major mode of transfer is through the movement of live animals (postlarvae,
fry and broodstock). Taura syndrome virus (TSV), an OIE “notifiable disease”, was previously known
only from the Western Hemisphere, however it now also occurs in Asia, where it was most recently
reported from Indonesia in 2002 (NACA/FAO 2003). Importation of Penaeus vannamei to Asia for
aquaculture, along with several misconceptions among aquaculturists on the utilization of specific pathogen
free (SPF) and high health shrimp lead to the introduction of TSV to the region. Penaeus vannamei
has been illegally imported to several countries in the region.