Download Diseases of penguins

Diseases of penguins
Thirteen of the world’s 16 penguin species (family Spheniscidae)
occur in New Zealand’s maritime territories(1). Four are either rare or
only locally common endemics and, of the remaining species, five
breed here and four are non-breeding visitors(1). The endemic and
endangered yellow-eyed penguin or hoiho (Megadyptes antipodes) is
locally distributed on the South Island, Stewart Island, Codfish
Island, the Auckland Islands and Campbell Island. The rarest
Penguins are a significant component of New Zealand’s
biodiversity with 13 species, four of which are endemic.
Disease prevalence studies have been
limited to a few species and to a few
disease agents. The published literature is
reviewed along with unpublished data from
New Zealand’s diagnostic laboratories.
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
subantarctic islands including the Antipodes, the Bounties, and on
Disappointment Island in the Aucklands. Outside the breeding
season individuals of both species disperse widely and have been
recorded regularly in Australia. Fledgling Snares crested penguins are
occasionally found wrecked on Southland beaches in summer(5). Low
numbers of erect-crested penguin fledglings are found beach-cast on
the southeast coast of the South Island during March and April(5).
The native species with the most northerly breeding distribution,
extending from Northland to Stewart Island and the Chatham
Islands, is the blue penguin or korora (Eudyptula minor). At least five
phenotypic variants, or subspecies, occur around New Zealand; one
is known as the white-flippered penguin. Blue penguins are common
and frequent the Hauraki Gulf, Cook Strait, Kapiti coast, Otago,
Foveaux Strait and the Chathams. Between1960 and1982 almost
In Antarctica, New Zealand’s Ross Dependency has three breeding
penguin species including the emperor (Aptenodytes forsteri), Adélie
(Pygoscelis adeliae), and chinstrap (P antarctica)(1). Visitors and
vagrants to the New Zealand region include the two subspecies of E
chrysalophus (the royal and macaroni), king (A patagonicus), and
gentoo penguin (P papua), whose closest breeding colonies are on
Macquarie Island and Heard Island. The Magellanic penguin
(Spheniscus magellanicus) is a rare vagrant from South America(1).
The threats to the various species in New Zealand territories include
predation by introduced mammals, habitat alteration and
disturbance, competition for resources, and incidental mortality by
commercial fisheries(12)(13). Infectious diseases and parasites may also
compromise the survival of individuals or relict populations and are
the subject of this review.
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
similar event in Northland in 1973-74(5)(6). 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
period of breeding birds(5)(7).
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
breed there. The yellow-eyed penguin is a solitary-nesting species
while the other three species are colony-nesting crested penguins and
include the Snares crested and erect-crested penguins. The smallest
of the group, the eastern rockhopper penguin (E chrysocome filholi),
occurs locally on New Zealand’s subantarctic islands and on
Macquarie Island in Australian territory. Two other rockhopper
A 1988 serological survey on a limited number of rockhopper and
yellow-eyed penguins on Campbell Island reported no antibodies
against a panel of poultry viruses including the agents of infectious
bronchitis, reticuloendotheliosis, Newcastle disease, infectious
laryngotracheitis, avian encephalomyelitis, infectious bursal disease,
Marek’s disease, and fowlpox(14).
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 .
penguins on Macquarie and Heard Islands in Australia’s
(8)
Surveillance 28(4) 2001
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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)
King, royal and rockhopper penguins sampled at several sites had
antibodies against one of the isolates and royal penguins were
seropositive for NDV(15). Antibodies against the same viruses were
also detected in sera from a few blue penguins sampled along the
Victorian coast of Australia(17).
and the Ross Sea in Antarctica(18)(22).
Arboviruses: Antibodies against a Flavivirus have been found
occasionally in sera from king, royal, Adélie, and rockhopper
penguins(15). A new Flavivirus, Bunyavirus, and Orbivirus were
isolated from ticks (Ixodes uriae) collected from penguins on
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 yelloweyed 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
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
(18)
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
hemisphere . The significance of infection for free-living birds is
any free-living penguin species.
(19)
(16)
unknown but the isolates were not pathogenic for chickens or blue
penguins(17). However, infection could predispose penguins to
opportunistic infections or confer immunity against pathogenic
viruses such as NDV. Antibodies against the latter were detected in
the serum of Adélie and royal penguins(15)(18). The significance of
NDV for free-living birds is unknown but mortalities have occurred
Suspected viral mortalities: In 1972, an unusual event killed 65%
of Adélie penguin chicks near Mawson Station, Antarctica(29).
Moribund chicks were in good body condition but were recumbent
and would stagger and fall forward when righted. The cause was not
established but it was not starvation as occurred in 1995(30).
among Adélie penguins(20) and in a captive king penguin(21). The
A mass mortality among gentoo penguins at Signey Island involved
Adélies were captured in 1973 near Scott Base in the Ross Sea and
several hundred birds that were in good body condition, but each
shipped to the United States where several birds died from an
had focal ulcers on the dorsal surface of the feet(31). No aetiology was
infection characterised as velogenic neurotropic in chickens . It
established.
(20)
was believed that infection was contracted in the wild because the
birds were maintained in quarantine.
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6
In 1981, an unusual number of four- to five-week-old Adélie chicks
died on Petersen Island (near Casey Station). No clinical signs were
Surveillance 28(4) 2001
observed and no necropsies conducted. However, five of 55 adult
birds were seropositive for influenza antibodies(18). Although
unlikely, the virus may have been implicated.
Bacterial and fungal diseases
Enteric bacteria: Many bacteria have been isolated from free-living
penguins but only a few are pathogens(32)(33)(34). Five Salmonella
serotypes were isolated from Adélie penguins on Ross Island,
Antarctica, but were not associated with disease(35). Campylobacter
spp, with only minor sequence difference in 16sRNA from C jejuni
and C lari, were isolated from marine birds including apparently
healthy gentoo and macaroni penguins sampled on Bird Island,
South Georgia(36). Whether these enteric bacteria are normal flora of
penguins is not known. It is possible that bacteria were brought to
Antarctica or subantarctic islands on contaminated poultry
products and disseminated through penguin rookeries by scavengers
such as skuas and giant petrels. Migratory sea birds may also act as
vectors of infection to penguin species that are restricted to the
subantarctic or Antarctic(37).
Cause of mortality and incidental findings for
penguins in New Zealand, based on records on the
Wildlife Mortality Database (Huia) and from Hocken(13)
Diagnosis
Blue penguin
Yellow-eyed
penguin
Starvation
34 (13%)
15 (6%)
2
Starvation and parasitism1
Starvation and trauma
1 (0.004%)
1 (0.004%)
Starvation and neurological signs2
Trauma
Dogs
35 (14%)
Mustelids (ferrets)
20 (8%)
8 (3%)
Shark3
Vehicles
32 (13%)
1
Vandalism
10 (4%)
Traps
3 (1%)
Undetermined
27 (11%)
Wrecks (multiple starvation mortalities)4 8 (3%)
5 (2%)
Bacterial infection5
1
Plasmodium-like infection6
8 (3%)
Aspergillosis7
10 (4%)
Drowning8
Undetermined
36 (14%)
One blue penguin was under rehabilitation for seven days and at necropsy also
had mycotic pneumonia (Aspergillosis). The parasite burdens included some or
all of the following: Contracaecum sp nematodes in the proventriculus,
Tetrabothroid cestodes in the intestine, Renicola trematodiasis of the kidney,
intestinal and renal coccidiosis. One bird had haemorrhage from a
proventricular ulcer that was probably parasite-induced.
2
One blue penguin was reported to display neurological impairment but no
histological lesions were detected. The signs were possibly biotoxin-induced.
3
Inferred from linear lacerations in skin and shorn feathers(13).
4
The eight birds in this submission were juveniles found wrecked at the same
time on the Coromandel Peninsula.
5
Presumptive diagnosis based on gross and histological lesions.
6
Acute multifocal necrotising hepatitis, splenitis and myocarditis associated with
intracellular protozoa, species not determined.
7
Aspergillosis was the only significant finding reported.
8
Drowning diagnosed from the location of the carcass and postmortem finding
of fluid in lungs and air sacs(13).
1
Psittacosis: Antibodies against Chlamydiophila psittaci, the cause of
avian psittacosis, were found in emperor, rockhopper, royal, gentoo
and Adélie penguins(38)(39). There was no evidence of disease and the
origin and significance of infection are unknown.
Pasteurellosis: Pasteurella multocida of similar serotype to that
which causes avian cholera epidemics among North American
waterfowl was isolated from several septicaemic rockhopper
penguins on Campbell Island(14). Norway rats (Rattus norvegicus)
appear to be associated with the disease. The eradication of rats
from Campbell Island over the winter of 2001 may reduce the
prevalence of infection and establish whether it is implicated in the
rockhopper decline on the island.
Borreliosis: Antibodies against Borrelia burgdorferi, the cause of
Lyme disease in mammals, were detected in king penguins on the
Crozet Archipelago, French subantarctic(40). The bacteria were also
isolated from I uriae, a likely vector. Infection rarely results in
disease in birds but it is a potential zoonosis.
Aspergillosis: Caused by Aspergillus fumigatus, and rarely A flavus,
A niger or A terreus, aspergillosis is commonly diagnosed in captive
penguins but is rare in free-living birds. However, pulmonary
infection has been recorded in emaciated beach-cast juvenile little
blue penguins(15)(41). Lesions have also been reported in wrecked blue
penguins in New Zealand (see table) and in a yellow-eyed penguin
juvenile(42).
Metazoan and protozoan parasites
Helminths, ectoparasites, and protozoa of penguins have been
comprehensively reviewed and catalogued(45)(46)(47)(48).
Ectoparasites: Fleas, ticks, mites and biting lice occur on most
penguin species. The tick Ixodes uriae has a wide distribution on
seabirds in both hemispheres. Three other species have also been
recorded on blue penguins: I kohlsi, I auritulus and I eudyptidus.
Colony-nesting species have the highest parasite burdens and ticks
are most commonly found on chicks around the face, ear canals,
cloaca and feet. Species affected include emperor, Adélie, gentoo,
royal, rockhopper, blue and Snares crested penguins. Heavy
infestation may cause death of chicks and occasionally adults. Of
Aspergillus spp are ubiquitous and even found in soils and skua
greater significance may be the potential for transmission of viral
nests in Antarctica(43). A serological survey of penguins from New
infections. Paramyxoviruses and arboviruses were isolated from
Zealand (yellow-eyed and blue), the subantarctic (yellow-eyed and
I uriae from royal and king penguins on Macquarie Island(15)(23)(24).
rockhopper), and Antarctica (Adélie), found an inverse relationship
An uncharacterised enveloped RNA virus, morphologically but not
between seroprevalence and latitude; all blue penguins from Napier
antigenically similar to infectious bronchitis virus of chickens, was
were seropositive but none of the Adélies(44).
isolated from I uriae from Campbell Island rockhopper penguins(14).
Surveillance 28(4) 2001
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Biting lice (Austrogoniodes sp) have been recorded on all species of
described from blood smears from free-living Fiordland crested
Antarctic and subantarctic penguins except gentoo and chinstrap
penguins(53), is transmitted by blackflies (Austrosimulium spp) and is
penguins(45)(46). Fleas (Parapsyllus sp) are also common in the
probably not pathogenic. It was not found in blood smears from 25
subantarctic and temperate zones and have been found on blue,
Snares crested penguins and one erect-crested penguin on the
rockhopper, gentoo, macaroni, Magellanic, and yellow-eyed
Snares(53). Trypanosoma eudyptulae was described from smears from
penguins. Fleas need a suitable nest environment and spend only
blue penguins in southeastern Tasmania(54). The intermediate host
part of their life on the birds. Lice and fleas are of little pathogenic
was not identified but ticks were proposed. Infection appears to
importance but numbers may be increased on birds that are
cause no disease in penguins.
debilitated and not preening properly . They may also transmit
(41)
viruses.
Malaria: Avian malaria caused by Plasmodium relictum is an
important cause of mortality among captive penguins in North
Helminths: Cestodes, nematodes, trematodes, and acanthocephalans
America and Europe(55), and also among free-living blue penguins in
are common in most penguin species. Blue penguins in North
Australia(56) and African black-footed penguins(57)(58). Infection in the
Otago had lower than expected burdens . Four species of
latter lasts for life and stress such as oiling or transportation may
Contracaecum (gastric nematodes) have been recorded, and may be
induce recrudescence(59)(60). Parasitaemia underestimates infection
associated with erosion and ulceration leading to haemorrhage.
but an enzyme-immunoassay detected a high seroprevalence (up to
Infection rates in South Island yellow-eyed penguins were high for
100%) in yellow-eyed penguins on Banks Peninsula, Otago
chicks and moderate for adults but parasite burdens were low and
Peninsula, Catlins, Codfish Island, Enderby Island (the Aucklands),
no pathology was observed(13)(45). Although nematodes probably do
and Campbell Island(61)(62). Only 10% of yellow-eyed penguins
not directly contribute to the population declines observed for
sampled on Stewart Island had P r spheniscidae parasitaemia(57) and
several New Zealand penguin species, they may be a factor(6)(41)(49)(50).
none of 189 blood smears from 83 free-living yellow-eyed penguins
(13)
Cestodes of the genus Tetrabothrius occur in the intestines of blue,
emperor, king, gentoo, Adélie, rockhopper and Magellanic penguins.
Their life cycle is unknown but it may involve euphausiid
on Banks Peninsula had demonstrable haemoparasites (S
McDonald, personal communication).
Despite the apparently high level of exposure of yellow-eyed
crustaceans as intermediate hosts . Acanthocephalans are rarely
penguins to Plasmodium sp, the incidence of clinical disease appears
reported from marine birds but comprised 1.3% of helminths in a
to be low. The cause of the deaths of 150 adult penguins on Banks
sample of 20 yellow-eyed penguin chicks(49). Corynosoma sp has also
Peninsula during the summer of 1989-90 was not established(42).
been reported for gentoo penguins(48). Both are an unlikely cause of
Avian malaria was suggested as the aetiology based on elevated
significant disease among penguins.
antibody titres in plasma from dead birds(61). However, the
(51)
investigators found no histological lesions characteristic of malaria
Several trematode species reside in the liver, gall bladder, and
intestines of penguins(46). Most are probably well tolerated but the
hepatic fluke Mawsonotrema eudyptulae contributes to the mortality
of juvenile blue penguins periodically wrecked in Victoria and New
and proposed that acute intoxication by a marine algal neurotoxin
was more likely, based on clinical signs, pathology and
environmental conditions (J Gill, personal communication).
Zealand(5)(6)(41)(50)(52). Trematodes may exacerbate the effects of
Whatever the cause of that event, a recent case on Otago Peninsula
starvation in recently fledged birds. Heavy burdens of flukes were
shows that avian malaria has the potential to cause mortality among
noted in the kidneys of wrecked blue penguins in Northland, but
yellow-eyed penguins. In February 2001, a juvenile in good body
with minimal pathology(6). The species was not identified but it is
condition was found dead without gross lesions. On histology, there
probably of the family Echinostomatidae.
was extensive acute necrosis and inflammation of the myocardium,
Coccidiosis: Oocysts were detected in the faeces of free-living
yellow-eyed penguins in Otago but the species was not determined
because they could not be sporulated(49). The low prevalence of
liver and spleen associated with intracytoplasmic Plasmodium-like
parasites(63). Similar pathology was also described for a captive
Fiordland crested penguin in Australia(56).
infection suggests that it is not significant. Both intestinal and renal
No haematozoa have been detected in blood smears from king,
coccidiosis have been recorded in wrecked blue penguins in
royal, and gentoo penguins on Macquarie Island, king and macaroni
Victoria(41)(52). Oocysts were found in faeces of five of 48 birds but on
penguins from Heard Island, and Adélie and emperor penguins
histology, schizonts were detected in the intestinal mucosa of only
from Antarctica(64)(51)(65). Serology confirmed the absence of infection
one . By contrast, 64% of birds had chronic interstitial nephritis
from Adélie penguins on Ross Island, Antarctica, suggesting that a
and ureteritis associated with coccidia. However, the lesions were
suitable vector is absent from polar latitudes(61). However, at least
mild and focal and probably of little pathological significance .
some penguins that inhabit the subantarctic islands appear to be
Intestinal coccidiosis was reported for wrecked blue penguins in
exposed. King and gentoo penguins on the Kerguelen and Crozet
Northland but lesions were not described(6).
Islands in the subantarctic had antibodies as did yellow-eyed
(41)
(52)
Haematozoa: A novel blood parasite, Leucocytozoon tawaki,
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penguins on the Aucklands and Campbell Island, but rockhoppers
Surveillance 28(4) 2001
on Campbell Island did not(61)(62). Suitable vectors are probably
Mortality in New Zealand
absent from Antarctica but may be present in the subantarctic.
Since 1991, diagnostic laboratories have received, and entered on
Alternatively, penguins that breed on subantarctic islands may be
the wildlife pathology database (Huia), 34 submissions of blue
exposed to vectors if they migrate to lower latitudes outside the
penguins and four of yellow-eyed penguins. Each case was re-
breeding season.
evaluated for this review. An additional 213 blue penguins from
High seroprevalence of malaria was reported in captive blue
northern Otago were examined between 1994 and 1998(13). The
penguins in Napier(61) and in free-living birds from Codfish Island,
diagnoses from both sources are summarised in the table.
to the west of Stewart Island(62). Mortality has not been reported in
New Zealand but does occur among blue penguins in Australia(56).
Other protozoa: A blue penguin that died of toxoplasmosis while
under rehabilitation in Tasmania had been fed on uncooked meat
and held in a household with several cats(66). A tick-borne
piroplasmid, presumed to be Babesia sp, has also been found in blue
penguins in Australia where it causes mild regenerative anaemia in
juveniles (Cunningham cited by Clark and Kerry(46)).
Non-infectious causes of mortality
Starvation
Juvenile blue penguins appear susceptible to periodic mass
mortalities that may reflect fluctuations in prey availability.
Rockhopper penguins may also be susceptible to fluctuations in
prey availability that are influenced by the El Niño-Southern
Oscillation(67). Blue penguin wrecks have been recorded in New
Zealand since the early 1940s(68). During two large wrecks in
Northland in July-August 1973 and April-May 1974, there was a
hundredfold increase in the number of beach-cast birds(6). Most
were immature females in poor body condition with an empty
gastrointestinal tract, depleted fat reserves, muscle atrophy, and
moderate parasite burdens. It was concluded that death resulted
from starvation exacerbated by parasitism and bad weather, as was
proposed for a wreck of mixed-age blue penguins on the Victorian
coast between December 1977 and June 1978(41). A wreck of blue
penguins in South Australia and Victoria in March-April 1986 also
involved emaciated and parasitised juvenile birds that washed
ashore following southerly storms(50).
Conclusions
Most of the disease surveillance on penguins has occurred in the
Antarctic and subantarctic. The focus has been on potentially exotic
diseases that may have been introduced through human traffic to
these once remote regions. The risk has been minimised by a
protocol on Environmental Protection (Madrid, 1998) as part of the
Antarctic Treaty, 1991. This banned the importation of live poultry
During the summer of 1989-90 a catastrophic event claimed at least
and other birds into the Antarctic and requires the inspection of
half of the adult breeding population of yellow-eyed penguins on
dressed poultry for Newcastle disease and tuberculosis. However,
the Otago Peninsula(42). Moribund birds were neurologically
the international regulations are less strict than national quarantine
impaired and dead birds were in good body condition with no
measures and there are no protocols to control outbreaks of disease
evidence of infectious disease, suggesting that marine algal
should they occur in Antarctica(74). In New Zealand, the Department
biotoxins may have been implicated (J Gill, personal
of Conservation bans the transportation of poultry or poultry
communication). Over the past two decades marine dinoflagellate
products, apart from eggs, to the subantarctic islands. Tourist vessels
blooms have claimed a variety of marine vertebrates worldwide
do carry such products but are not permitted to discharge organic
ranging from fish and sea birds(69), to pinnipeds(70), sirenians(71), and
waste in the vicinity of islands. However, the risks posed by tourist
cetaceans(72). Blooms of neurotoxin-producing diatoms occur
and fishing vessel traffic are largely unknown.
frequently in New Zealand waters and have the potential to cause
neurological signs and death in penguins eating prey that has
accumulated the toxin(73). Laboratory assays to detect these biotoxins
are now available in New Zealand.
Clearly more surveillance is required for penguins in New Zealand
territories. Of the four endemic species, two are endangered
(yellow-eyed and Fiordland) and a third (erect-crested) is in
decline. There have been no studies on disease or mortality factors
among Snares crested penguins, Fiordland crested penguins, or
Surveillance 28(4) 2001
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erect-crested penguins, apart from scattered records of parasite
occurrence. Studies on yellow-eyed penguins have also been limited
(15)
to serology for avian malaria and aspergillosis, and opportunistic
sampling of wrecked birds. The alarming decline of rockhopper
penguins on Campbell Island prompted a limited disease
(16)
investigation in the mid 1980s(14). No firm conclusions could be
drawn other than the suggestion that avian cholera was probably
(17)
not implicated. A novel enveloped RNA virus was isolated but not
fully characterised and its pathogenicity not established. Research is
(18)
continuing into the associated environmental factors but disease is
(19)
not included (D Thompson, personal communication).
(20)
At the least, baseline serology should be conducted on all endemic
and native species breeding in New Zealand territories. A serum
bank should also be established to facilitate retrospective studies if
(21)
(22)
an outbreak of a suspected exotic disease occurs in future. Without
establishing what diseases may be endemic, it is not possible to
(23)
speculate further on the disease risks from introduction of exotic
birds or vectors or even from domestic avian species.
(24)
Acknowledgements
S McDonald, Otago University, provided unpublished data on avian
malaria seroprevalence in yellow-eyed penguins. J Gill, LABNET
(25)
Invermay Ltd; D Thompson, NIWA; D Wharton, Otago University;
and A Hocken, Oamaru, for personal communications. Cases on
Huia were contributed by M Alley, C Twentyman, R Norman, S
(26)
Cork, and P Duignan. Thanks to R Norman, J Cockrem and R
Pilgrim for reprints and copies of publications.
References
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(2) Darby JT, Seddon PJ. Breeding biology of yellow-eyed penguins (Megadyptes
antipodes). In: Davis LS, Darby JT (eds), Penguin Biology, Pp 45-62. Academic
Press, San Diego, 1990.
(3) Richdale LE. A brief study of the history of the yellow-eyed penguin. Emu 40,
265-87, 1941.
(4) Richdale LE. Yellow-eyed penguin. In: Robertson CJR (ed), Readers Digest
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Padraig J Duignan
New Zealand Wildlife Health Centre
Institute of Veterinary, Animal and Biological Sciences
Massey University
Private Bag 11 222, Palmerston North
Email: [email protected]
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