Page 24 - JSOM Winter 2021

An Introduction to the Processionary Caterpillar,

An Underrecognized Threat to US Military Personnel in Australia

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Michael A. Washington *; Julianne Farrell ;
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Julianne Meany ; Weng Chow 4

ABSTRACT
Processionary caterpillars are well-described threats to human (Ochrogaster lunifer). This caterpillar is the larval form of the
and animal health. They are found throughout Central Asia, Bag-shelter moth that is ubiquitous in the coastal and inland
Northern Africa, and Southern Europe. However, US military regions of Australia, where it tends to nest in the canopies or
personnel may not be familiar with the threat that these organ- at the base of Acacia and Eucalyptus trees (Figure 1). The
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isms pose in Australia. The larval form of the bag-shelter moth ground-nesting form is more common in coastal areas while
(Ochrogaster lunifer) is a processionary caterpillar that has the canopy-nesting form is more common in inland regions.
been found throughout inland and coastal Australia. These or- However, there are areas between coastal and inland regions
ganisms are habitually associated with Acacia and Eucalyptus where both forms have been noted.
trees and they tend to form long chains known as “proces-
sions” as they travel between nesting and pupating sites. They
are covered with numerous hairs that can detach, become air-
borne, and cause potentially life-threatening inflammatory re-
actions and ocular trauma in susceptible personnel. They can
also cause severe inflammatory reactions in military working
animals. It is important that military and preventive medical
personnel become aware of the presence of processionary
caterpillars in Australia, and that they can identify aerial or FIGURE 1
ground-based nests so that these dangerous organisms can be Processionary
avoided by both humans and animals. Early identification is caterpillars on tree
branches near their nest.
important so that prompt medical treatment can be rendered
in the event of an accidental exposure.
Keywords: entomology; military animals; bag-shelter moth; Photo courtesy of Julianne Farrell.
Ochro gaster lunifer; processionary caterpillar

Introduction
Processionary caterpillars have been described throughout
Most discussions of medical entomology (the study of the med- Central Asia, Northern Africa, and Central Europe. They
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ical impact of insects, spiders, ticks, and mites) in the military have been associated with at least one outbreak of dermatitis
environment tend to focus on members of the order Diptera among military personnel in Australia and a related species
(true flies, mosquitoes, and sandflies) and the order Arachnida of caterpillar has been associated with at least one outbreak
(spiders, mites, and ticks). These discussions tend to ignore among US military personnel in Europe. These outbreaks
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members of the order Lepidoptera (butterflies and moths). demonstrate that caterpillar exposure is a real threat to mili-
This omission is a mistake, given that there are several mem- tary personnel operating in the field environment. For several
bers of this group that can elicit a negative impact on human years, the United States has been sending thousands of troops
and animal health. Consequently, frontline military medical to Australia to participate in training rotations and bilateral
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providers may not be aware of the significance of these organ- military exercises. If this trend continues, it is possible that
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isms when it comes to planning medical support for troops there will be one or more US casualties due to processionary
serving in endemic regions. While the medical impact of the caterpillar exposure in the near future. An understanding of
Lepidoptera is often negligible within the continental United the biology of these insects, the most likely mechanisms of ex-
States, they can be a significant threat to military personnel posure, and the symptoms of exposure will be necessary to
in the Asia-Pacific region. This may be particularly true ensure that appropriate precautions are taken and that proper
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in regions that are endemic for the processionary caterpillar care is rendered.
*Correspondence to Michael.a.washington120.mil@mail.mil
1 LTC Michael A. Washington is affiliated with the Department of Clinical Investigation, Dwight D. Eisenhower Army Medical Center, Fort
Gordon, GA. Julianne Farrell is affiliated with the School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Aus-
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tralia. 2LT Julianne Meany is affiliated with the Department of Chemistry and Life Science, United States Military Academy, West Point, NY.
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4 MAJ Weng Chow is affiliated with the Australian Defence Force Malaria & Infectious Disease Institute, Enoggera, Queensland, Australia.
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