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| Journal of the New Zealand Medical Association,
25-July-2008, Vol 121 No 1278
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The potential direct impacts on human health
resulting from the establishment of the painted apple moth (Teia
anartoides) in New Zealand
José G B Derraik
The painted apple moth (Figure 1) Teia anartoides
(Lepidoptera: Lymantriidae) was discovered in West Auckland in
1999.1 An aerial spraying programme was
subsequently carried out, which seems to have led to the eradication of this
moth from New Zealand.1,2
The MAF Biosecurity New Zealand (this country’s lead
biosecurity agency and a division of the Ministry of Agriculture and
Forestry—MAF) website states in regards to human exposure to T.
anartoides caterpillars that “some people may also be allergic to the
hairs on the caterpillars”.2 However, in
contrast, in a recent radio interview regarding the eradication campaign, Jim
Anderton (New Zealand’s current Minister for Biosecurity) stated that the
painted apple moth “caterpillar has a very toxic effect on human
beings” and “if you have contact with it, it has a toxic reaction
[sic], quite a serious
one”.3
A MAF report from 2000 stated that “both the number of
people likely to be affected [by exposure to T. anartoides] and the
probability of severe reaction are low”
(p.5).28 Interestingly, a different view, but
similar to that expressed by the current minister, was given by MAF to the
public at the time of the eradication programme. What could be seen as
scare-tactics were employed to gain public support for the controversial aerial
spraying. This included the broadcast of 30-second radio advertisements
portraying the moth as a dangerous and scary creature, and media releases
stating for example “we [MAF] strongly advise anyone who thinks
they have come in contact with a Painted Apple Moth [sic] to seek
medical attention”.4
Figure 1. Painted apple moth caterpillar
(Teia anartoides)
 Source: Alan Flynn (MAF), www.forestryimages.org
A media release from Jim Sutton (Biosecurity Minister at the
time) also stated that “it was clear from overseas experience that about
95% of the population was allergic to the hairs on the painted apple
moth”.5
It seemed important, therefore, to examine the issues.
Evidence for adverse reactionsSuch claims of human health effects associated with exposure
to T. anartoides might have originated from a MAF commissioned health
impact assessment report. The document contained a section entitled Risk
Assessment of Exposure to the Painted Apple Moth, which examines “the
potential for adverse health effects resulting from establishment of the painted
apple moth in Auckland, should eradication efforts fail”
(p.50).6 The report
states that:
Contact with larval stages
of the painted apple moth is known to cause adverse health effects, including
skin lesions, eye irritation, and respiratory reactions. In extreme situations,
surface water can be so contaminated with frass (larval excrement) that it
affects water quality. This may be enhanced by degradation of the vegetative
canopy leading to an increase in water runoff.
The above claims however, were not substantiated, and the
only reference provided refers to an impact assessment on gypsy moth
(Lymantria dispar) prepared by the United States Department of
Agriculture (USDA).7 The gypsy moth is a member
of the same Lepidoptera family (Lymantriidae), but no other connections to
Teia anartoides seem to exist.
The document states that “adverse effects on human
health from contact with moth larvae or their hairs entrapped in shed pupa have
been reported in the following literature” (p.51). The literature referred
to encompasses 10 references, 8 of which were articles from peer-reviewed
journals. An examination of these references shows that the human health effects
discussed were associated with Douglas fir tussock moth (Orgyia
pseudotsugata),8,9 gypsy
moth,10–12 and tussock moth
(Euproctis bipunctapex).13,14 Another
reference refers to unidentified species of Australian
caterpillars,15 while a USDA report cited
refers to gypsy moth.16 These, or the text in
pages 51 and 52, make no direct references to Teia anartoides.
Nonetheless, the report discusses further potential impacts such as the effects
of heavy infestation on water quality, but it mentions neither the source of the
claim nor the species involved.
Although unpublished, there seems to have been adverse human
health reactions to exposure to T. anartoides in the laboratory in New
Zealand.4 The same media release also states
that “the hairs cause a nasty reaction resulting in painful and itchy
rashes in the majority of the human population”. However, since T.
anartoides seems to be a common pest in suburban orchards and on urban
garden plants,17–19 if the claims of
widespread human susceptibility and consequent adverse reactions were indeed
accurate, one would expect case reports of human exposure in Australia.
A 86-page monograph written by Southcott is probably the
most complete work available on the human health effects associated with
exposure to Lepidoptera in the Australian-New Zealand
region.20 However, this report contains only a
brief reference (two paragraphs) to T. anartoides (referred to by its
synonym Orgyia anartoides), which states that (p.149):
Mr ED Edwards,
Division of Entomology, CSIRO, has advised (pers. comm., 1978) that the cast
final instar larval skins of this species [Orgyia anartoides]
“have caused mild skin irritation on soft skin of wrists and between
fingers in the laboratory here. I have not heard of it causing irritation in the
field”.
Southcott makes no other references to any adverse human
health impacts associated with exposure to T.
anartoides.20 In comparison, the section
concerning another Australian moth species introduced to New Zealand (Uraba
lugens, gum leaf skeletoniser) and its associated human health effects is
approximately 9 pages long. In a later publication, Southcott re-emphasised the
issue regarding exposure to T. anartoides, stating that “contact
with this larva [Orgyia anartoides] in the laboratory has resulted in
mild skin irritation” (p.251),21 with no
mention of adverse consequences to human health having been observed in the
field. Such a lack of evidence was also supported by an extensive search of
online databases (CAB Abstracts, Current Contents, PubMed, and Web of Science)
and search engines (Google, Scirus, and Yahoo), all of which failed to yield
published accounts on this matter.
There are anecdotal reports of T. anartoides
affecting the health of forestry workers in Pinus radiata plantations
in South Australia, but there is however no confirmation of the species involved
(Charlma Phillips, pers. comm. 2008). Southcott described outbreaks of another
lymantriid Acyphas leucomelas in P. radiata plantations in the
region, whose health effects on forestry workers meant that many were
“unable to work due to [the adverse]
reactions”.20 Therefore, although it is
possible that the south Australian cases might have been a result of exposure to
T. anartoides, the involvement of other lymantriids cannot be
disregarded. Especially since T. anartoides appears to be rare in those
plantations, and it seems difficult to distinguish its larvae from those of
A. leucomelas and Orgyia australis in the field (Charlma
Phillips, pers. comm. 2008).
It is worth mentioning that the extent of the possible
physiological differences between apparently closely related Lepidoptera taxa
may be inferred for example, from studies on insecticide susceptibility. The
lethal concentration values as a result of caterpillar exposure to insecticides
may vary over 100-fold between genera22 or even
strains of the same species.23 In the same way
biochemical differences seem to account for such different caterpillar
susceptibility to exposure to foreign
compounds,23 extensive antigenic differences
may occur between moth species, leading to contrasting effects on human health.
Therefore, based on the available evidence, it appears that
the human health impacts associated with exposure to T. anartoides were
mistakenly estimated to be equivalent to those resulting from exposure to gypsy
moth and other lymantriids. Although these moth species are systematically
allocated to the same Lepidoptera family, there seems to be no evidence that
their biochemical profiles are similar to an extent so as to cause equivalent
adverse reactions in humans. The published evidence indicates the
opposite.
ConclusionAllergic and toxic reactions following exposure to
non-stinging arthropods are common
occurrences.24 Exposure to any insect setae may
cause adverse reactions in susceptible
people.25 Therefore, it is likely that some
people would experience adverse reactions following exposure to the setae of
Teia anartoides caterpillars. As with any human exposure to arthropods,
the possibility that some people may be more sensitive and experience severe
reactions cannot be discarded.
However, the direct consequences to human health resulting
from the establishment of the painted apple moth in New Zealand would likely be
minor, and lesser than for example the likely impacts resulting from exposure to
Uraba lugens (recently discussed in this
journal,26,27 and widely established in the
Auckland region). This is likely to be the case, as there seems to be no
published evidence of adverse reactions to human health as a result of field
exposure to Teia anartoides in Australia, despite, as already stated,
its apparently common presence in urban and suburban gardens in that country.
Competing interests: The author worked
for two and a half years for MAF Biosecurity New Zealand, having recently
resigned from his position as Human Health Senior Advisor.
Author information: Dr José G. B.
Derraik, Research Associate, Ecology and Health Research Group,
Wellington School of Medicine and Health Sciences, University of Otago,
Wellington, New Zealand
Acknowledgements: I thank Assoc Prof Ted
Nye (University of Otago, Dunedin, New Zealand) for comments on a previous
version of this manuscript, and Dr Charlma Phillips (PIRSA Forestry, Australia)
for valuable input.
Correspondence: Dr José Derraik.
Email: derraik@gmail.com
References:
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