Elsevier

Toxicon

Volume 40, Issue 8, 1 August 2002, Pages 1095-1100
Toxicon

Ant sting mortality in Australia

https://doi.org/10.1016/S0041-0101(02)00097-1Get rights and content

Abstract

We investigated ant sting related fatalities in Australia over the period 1980–1999. Data was obtained from the Australian Bureau of Statistics and state coronial authorities. Six ant sting-related fatalities were identified, five in Tasmania and one in New South Wales. All were males aged between 40 and 80-years-of-age and most (5/6) had prior histories of jumper or bull ant (Myrmecia spp.) venom allergy. However, none of the deceased carried injectable adrenaline and most died within 20 min of a single sting. Significant cardiopulmonary co-morbidities were identified in all cases and, in addition, moderate–severe laryngeal oedema and coronary atherosclerosis was observed in most (4/6) cases at autopsy. Where ascertained, Myrmecia ant venom specific immunoglobulin E antibodies levels were always elevated and fell into two distinct patterns of immunoreactivity. Adult Tasmanian males with a prior history of ant venom allergy and cardiopulmonary co-morbidities are therefore at highest risk of a fatal outcome from ant stings. Deaths may be avoided by the early recognition of anaphylaxis and self-treatment with adrenaline as well as by the development of purified Myrmecia ant venom immunotherapy.

Introduction

Ants are widespread Hymenopteran insects of the family Formicidae with approximately 8800 species described worldwide. Australia is richly endowed with 2750 known species and subspecies (Shattuck, 1999). However, despite this diversity there are relatively few species of medical importance and those can be divided into two major groups, distinguished by the extent of development of a venom injection apparatus. The first type has no effective apparatus while the second group has a clearly recognisable sting.

The former type, exemplified by the ‘meat’ ant, Iridomyrmex spp., can cause irritating bites that they spray with secretions from their abdominal glands (Southcott, 1988). The second group, typified by the Myrmecia ants, subfamily Myrmeciinae, are notable for their painful true stings and allergenic venom. Known as ‘jumper’ or ‘bulldog’ ants they are widely distributed in, and virtually endemic to, Australia. Amongst the at least 89 Myrmecia species identified so far, only two are well known; the small (10 mm long), jack jumper (Myrmecia pilosula), which is black with yellow mandibles, and the larger (15–20 mm long), bull ant (Myrmecia pyriformis) that is a duller brown in colour.

Both species are widely found throughout much of south-east Australia, including Tasmania. M. pilosula is also found in the south-west tip of Western Australia and much of South Australia (Sutherland and Tibballs, 2001). Other stinging ants, such as the IFA (Solenopsis spp.) and the primitive genus Rhytidoponera, are also found in Australia (Southcott, 1988). However, to date only four minimally documented ant sting fatalities are recorded in the Australian medical literature. In 1931, Cleland recorded three ant sting related fatalities, two adults and an infant, all from NSW. One fatality, a middle aged woman, was recorded from Tasmania in 1963 (Trinca, 1964, Lee, 1975).

Detailed analysis of fatalities can provide an important source of information on the determinants of severe morbidity for the purposes of injury prevention. Therefore, as part of a study of Hymenopteran fatalities in Australia (Levick et al., 1997, Levick et al., 2000, McGain et al., 2000, McGain et al., 2001), we undertook an analysis of ant sting related fatalities that occurred in Australia over the last two decades. We discuss the cases identified and make prevention and treatment recommendations.

Section snippets

Methods

In the absence of national coronial data for the study period, we proceeded through the national statistical database through to individual state-based coronial systems and, where necessary, individual clinicians. Specifically we searched, with their approval, the Australian Bureau of Statistics (ABS) mortality dataset for ant sting related fatalities that occurred during the period 1 January 1980–31 December 1999. With the consent of the relevant state and territory registrar—generals of

Results

We identified six fatalities that equates to a mean national annual incidence rate of 0.02 deaths per million population per year during the 20-year period. The fatalities were marked temporally skewed such that most (5/6) occurred in the second 10-year period and all of the cases occurred within an 11-year period. All of the deceased were men living in either NSW (1/6) or Tasmania (5/6). The average age of death was 58 years, with the range being from 40 to 80 years. All fatalities occurred

Discussion

This study confirms the lesser importance of ant stings, compared with snakebite, and bee and wasp sting fatalities, in Australia (Harvey et al., 1984, Sutherland, 1992, Sutherland and Leonard, 1995, Levick et al., 2000, McGain et al., 2000, McGain et al., 2001). This national mortality ranking is similar to that recorded in the USA (Barnard, 1973, Langley and Morrow, 1997, Prahlow and Barnard, 1998) with both countries reporting a near-identical fatality rate for ant stings (Langley and

Acknowledgements

This study was supported by grants from the Victorian Department of Human Services and Bayer Healthcare Limited. It could not have proceeded without the assistance of Mr Peter Burke, Ms Muriel Meyer and Mr David Jayne at the Australian Bureau of Statistics, Brisbane, as well as the various state and regional coronial authorities, hospitals and individual clinicians. We also thank Ms Gail Knowland and Dr Brian Baldo, Kolling Institute of Medical Research for provision of post-mortem assay

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