Diseases of penguins Penguins are a significant component of New Zealand’s Thirteen of the world’s 16 penguin species (family Spheniscidae) biodiversity with 13 species, four of which are endemic. occur in New Zealand’s maritime territories(1). Four are either rare or Disease prevalence studies have been only locally common endemics and, of the remaining species, five limited to a few species and to a few breed here and four are non-breeding visitors(1). The endemic and disease agents. The published literature is endangered yellow-eyed penguin or hoiho (Megadyptes antipodes) is reviewed along with unpublished data from locally distributed on the South Island, Stewart Island, Codfish New Zealand’s diagnostic laboratories. Island, the Auckland Islands and Campbell Island. The rarest Padraig J Duignan penguin species in the world, its population has declined dramatically on the South Island(2). Fledglings go to sea in February In recent years there has been a dramatic decline in the number of and March and half die of malnutrition during their first five weeks erect-crested and rockhopper penguins. The former has decreased by at sea resulting in a peak of beach-cast mortality in May and 20% on the Antipodes since the mid 1990s and the latter by about June(3)(4)(5). The Fiordland crested penguin or tawaki (Eudyptes 90% over the past 50 years on Campbell Island(8). Although the pachyrhynchus) is also an endangered endemic that has a restricted factors responsible have yet to be established, the circumpolar breeding distribution from Westland to Stewart Island. Most beach- decline of rockhoppers suggests widespread environmental changes cast mortality occurs from October to February when fledglings go (D Thompson, ESR, personal communication). Declines of yellow- to sea and breeding adults begin to moult(5). Related endemic species eyed penguins have been attributed to disturbance, habitat loss, are the Snares crested penguin (E robustus) and the erect-crested introduced predators, periodic food shortages, and fluctuations in penguin (E sclateri). The former is locally abundant on the Snares climatic variables such as rainfall and sea surface temperatures(9)(10)(11). Islands where the only nesting sites occur. The latter breeds on In Antarctica, New Zealand’s Ross Dependency has three breeding subantarctic islands including the Antipodes, the Bounties, and on penguin species including the emperor (Aptenodytes forsteri), Adélie Disappointment Island in the Aucklands. Outside the breeding (Pygoscelis adeliae), and chinstrap (P antarctica)(1). Visitors and season individuals of both species disperse widely and have been vagrants to the New Zealand region include the two subspecies of E recorded regularly in Australia. Fledgling Snares crested penguins are chrysalophus (the royal and macaroni), king (A patagonicus), and occasionally found wrecked on Southland beaches in summer(5).Low gentoo penguin (P papua), whose closest breeding colonies are on numbers of erect-crested penguin fledglings are found beach-cast on Macquarie Island and Heard Island. The Magellanic penguin the southeast coast of the South Island during March and April(5). (Spheniscus magellanicus) is a rare vagrant from South America(1). The native species with the most northerly breeding distribution, The threats to the various species in New Zealand territories include extending from Northland to Stewart Island and the Chatham predation by introduced mammals, habitat alteration and Islands, is the blue penguin or korora (Eudyptula minor). At least five disturbance, competition for resources, and incidental mortality by phenotypic variants, or subspecies, occur around New Zealand; one commercial fisheries(12)(13). Infectious diseases and parasites may also is known as the white-flippered penguin. Blue penguins are common compromise the survival of individuals or relict populations and are and frequent the Hauraki Gulf, Cook Strait, Kapiti coast, Otago, the subject of this review. Foveaux Strait and the Chathams. Between1960 and1982 almost 16,000 were recorded in beach surveys for sea bird mortality(5). This Infectious diseases figure includes unusual mortalities (wrecks) such as the 3,729 blue The literature on infectious diseases of New Zealand’s penguins is penguins found dead on Auckland’s east coast beaches in 1974 and a patchy with few directed studies on endemic diseases. Several (5)(6) similar event in Northland in 1973-74 . Annual mortality peaks penguin species have received little attention apart from cataloguing from January to March, coinciding with fledging and the moulting parasites. With little information on endemic disease, the risks from (5)(7) period of breeding birds . potentially exotic diseases are largely unknown. The subantarctic islands (Aucklands, Campbell, Bounties, Antipodes, Viral infections Snares) are frequented by ten penguin species and four regularly A 1988 serological survey on a limited number of rockhopper and breed there. The yellow-eyed penguin is a solitary-nesting species yellow-eyed penguins on Campbell Island reported no antibodies while the other three species are colony-nesting crested penguins and against a panel of poultry viruses including the agents of infectious include the Snares crested and erect-crested penguins. The smallest bronchitis, reticuloendotheliosis, Newcastle disease, infectious of the group, the eastern rockhopper penguin (E chrysocome filholi), laryngotracheitis, avian encephalomyelitis, infectious bursal disease, occurs locally on New Zealand’s subantarctic islands and on Marek’s disease, and fowlpox(14). Macquarie Island in Australian territory. Two other rockhopper subspecies, E c chrysocome and E c moselyi, are vagrants. Crested Paramyxoviruses: Nine paramyxovirus isolates were recovered from penguins breed and moult ashore and then spend about four cloacal swabs collected between 1976 and 1979 from royal and king months foraging at sea over the winter(8). penguins on Macquarie and Heard Islands in Australia’s page 5 Surveillance 28(4) 2001 subantarctic(15)(16). One isolate was indistinguishable from viruses of Orthomyxoviruses: Avian influenza virus antibodies, but not PMV-1 serotype (lentogenic Newcastle disease virus, NDV). No clinical disease, were found in Adélie penguins from Casey Station viruses were isolated from either gentoo or rockhopper penguins(15). and the Ross Sea in Antarctica(18)(22). King, royal and rockhopper penguins sampled at several sites had Arboviruses: Antibodies against a Flavivirus have been found antibodies against one of the isolates and royal penguins were occasionally in sera from king, royal, Adélie, and rockhopper seropositive for NDV(15). Antibodies against the same viruses were penguins(15). A new Flavivirus, Bunyavirus, and Orbivirus were also detected in sera from a few blue penguins sampled along the isolated from ticks (Ixodes uriae) collected from penguins on Victorian coast of Australia(17). Macquarie Island, which suggests several possibilities for the low In Antarctica, paramyxoviruses were isolated from Adélie penguin prevalence of antibodies: transmission rates may be low, penguins cloacal swabs at several rookeries between 75°E (Davis Station) and may be a dead-end host, or disease may be fatal and few birds 170°E (the Ross Sea)(18)(19). A serological survey of seven colonies seroconvert and survive(23)(24)(25). Recently, a new arbovirus (Family Togaviridae, genus Alphavirus) was isolated from lice collected from elephant seals (Mirounga leonina) on Macquarie Island(26). Further characterisation is required for these novel wildlife viruses. Unclassified RNA virus: The significance of an uncharacterised RNA virus isolated from a pool of ticks (I uriae) from rockhopper penguins on Campbell Island(14) has not been established and antibodies were not present in rockhopper or yellow- eyed penguins. It is unlikely to be associated with the species’ decline. Birnaviruses: Infectious bursal disease virus (IBDV) occurs as avirulent strains Yellow-eyed penguins and a sealion on Enderby Island (photo Gareth W Jones) and a highly virulent strain. Even the avirulent strains can cause growth found that infection was widespread close to Casey Station in retardation and immunosuppression(27). Antibodies against IBDV (18) Australian territory and the French base of Dumont d’Urville . were detected in sera from emperor and Adélie penguins in However, no seropositive birds were detected at 13 sites near the Antarctica but there was no evidence of disease(28). Adélie chicks at a (19) Davis Station in Australian territory . It appears that titres may be colony remote from human activity were seronegative, suggesting elevated only transiently following infection and this may influence that the virus may have been introduced into Antarctica with seroprevalence data. contaminated poultry products. Based on antigenic and biochemical characteristics, the penguin Herpesviruses: A herpesvirus caused laryngotracheitis-like paramyxoviruses are distinct from those of other avian species but infection in African black-footed penguins (Spheniscus demersus) at some isolates share epitopes with PMV-1 isolates from the northern a zoo in North America(29). The disease has not been reported for (16) hemisphere . The significance of infection for free-living birds is any free-living penguin species. unknown but the isolates were not pathogenic for chickens or blue Suspected viral mortalities: In 1972, an unusual event killed 65% penguins(17). However, infection could predispose penguins