scientific correspondence

by heat, desiccation and chemical agents, and Poultry virus infection in is contagious and highly infectious by the faecal-oral route11 . It is likely to remain an environmental contaminant of colonies Antarctic penguins between breeding seasons. The recent rapid spread of the new highly virulent strains ntarctic penguins appear to be relatively throughout most of the poultry industry in A free of infectious diseases, although the Northern Hemisphere is testament to its there is serological evidence of infection potential for widespread dissemination. A with a number of avian diseases found else­ potent source of environmental contamina­ where1-4. An infectious agent is suspected in tion in could be from careless or one case of mass mortality in Adelie pen­ inappropriate disposal of poultry products, guin chicks, Pygoscelis adeliae5 (Fig. 1), but allowing access by scavenging birds such as there have been no confirmed reports of any the south polar skua, Catharacta maccor­ major outbreaks of infectious disease. Here micki. Spread within Antarctica could be we report evidence for the occurrence of an facilitated through the movement of people avian pathogen, infectious bursa! disease carrying the virus on contaminated foot­ virus (IBDV), in wild Antarctic penguins. wear, clothing, equipment or vehicles. This raises concern for the conservation of Figure 1 Adelie penguin about to feed its chick. Although clinical disease was not appar­ avian wildlife in Antarctica. ent in either species of penguin, further IBDV is a pathogen of domestic chickens 1995 and February 1996 from 133 adult investigation is warranted. The presence of Gallus domesticus, but antibodies have been Adelie penguins from two colonies within 40 seroreactors near centres of human activity detected in a variety of wild aquatic bird km of Mawson (67° 31' S, 62° 48' E) (Fig. 2). raises the possibility that the virus may have species6• It affects lymphoid organs, primarily We used a standard virus neutralization test been introduced. The size of our chick the bursa of Fabricius in chicks, the main (VNT) to measure antibody titres8• Antibody sample at was sufficient to site for the development of antibody­ titres of 1 in 80 or greater were regarded as detect a prevalence of in excess of 20% producing B-lymphocyte populations. Sub­ positive9• Using this conservative criterion, seroreactors (P < 0.05) 12• If IBDV was clinical effects and immunosuppression, the prevalence of positive VNT reactors was present in this location, the seroprevalence caused by even the less virulent strains of 65.4% in chicks and 2.1 % would be expected to be similar to that IBDV, retard growth and development and and 2.6% in the two colonies of adult Adelie among the equivalent age group of emperor predispose the chick to opportunistic infec­ penguins. Infection with IBDV occurs prin­ chicks. Thus the absence of neutralizing tions7. Morbidity and mortality rates in cipally in young birds 10 and so prevalence of antibodies in the chicks from this remote young chickens vary but can be high, espe­ seroreactors would decline with age. colony of Edmonson Point suggests that this cially in a newly emerged, globally spreading, We found no antibodies in Adelie serum area is free from IBDV contamination. high-virulence strain. taken from either chicks ( n = 17) or adult At this time, it must be assumed that We inferred IBDV infection from the birds ( n = 26) in January 1996 from a IBDV may be pathogenic in Antarctic pen­ presence of specific antibodies in serum col­ remote and rarely visited colony at Edmon­ guins, and is likely to be spread by human lected from both emperor (Aptenodytes son Point (74° 21 ' S, 165° 03' E) in the Ross activity. The potential for expeditioners and forsteri) and Adelie penguins. We collected Sea (Fig. 2). In a retrospective analysis, the tourists to be vectors of disease as they move samples from 52 emperor penguin fledgling prevalence of antibodies in adult Adelie pen­ around Antarctica may pose the greatest chicks (four to five months of age) from guin serum collected at Mawson in January threat yet to its avian fauna. Auster Rookery (67° 23' S, 64° 02' E) in 1991 was 1.5% (n= 136). Heather Gardner, Knowles Kerry December 1995, and between September IBDV is relatively resistant to inactivation Martin Riddle Antarctic Division, Department of Environment, Sport and Territories, Channel Highway, Kingston 7050, Tasmania, Australia e-mail: [email protected] Sue Brouwer, Laurie Gleeson Australian Animal Health Laboratory, CS/RO, PO Bag 24, Geelong 3220, Australia

I. Clarke, J. R. & Kerry, K. R. Korean f. Polar Res. 4, 79- 96 ( 1993). 2. Morgan. I. R. & Westbury, H. A. Avian Dis. 25, IOI 9- 1027 (I 98 I). 3. Morgan, l. R. & VVcstbury, H. A. Hydrobiologica 165, 262- 269 (1988). 4. Austin, F. ). & Webster, R. G. /. Wildlife Dis. 29, 568- 571 ( 1993). 5. Kerry, K. R., Gardner, H. G. & Clarke, J. R. Microbial. A ust. 17, 16 ( 1996). 0 6. Wilcox, G. E. et al. Avian Pathol. 12, I 35- 139 (1 983). M~Ferran, J. B. in Virus Infections ofB irds (ed. Mcferran, J. 8. & km McNulty. M. S.) 2 13- 228 (Elsevier Science, I 993). Antarctic continent 8. Manual of Standards for Diagnostic Tests and Vaccines 496-503 (O ffice Internationales des Epizooties, 1996). 61 " 00'E 62" 00' E 63° 00' E 9 Giambrone, J. J. Avian Dis. 24, 284-287 (1980). 10. Hitchncr, S. B. Avian Dis. 2, 61 1-613 (1976). 11 . Fenner, F. et al. Veterinary Virology (Academic, London, 1987). Figure 2 Antibodies to IBDV were identified in adult Adelie penguins at three sites within 40 km of Mawson 12. Cannon, R. M. & Roe, R. T. Livestock Disease Surveys: A Field and in emperor penguin chicks at Auster Rookery, 50 km east of Mawson. No antibodies were found in Manual.for Veterinarians (Australian Gov. Publ. Service, chicks or adult Adelie penguins from the remote colony at Edmonson Point in the . Canberra, 1982).

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