Wildlife Research Wildlife Research Society
Ecology, management and conservation in natural and modified habitats

Additional toxins for feral pig (Sus scrofa) control: identifying and testing Achilles’ heels

Brendan D. Cowled A B , Peter Elsworth C and Steven J. Lapidge A D

A Invasive Animals Cooperative Research Centre, University of Canberra, ACT 2601, Australia.

B The University of Sydney, School of Veterinary Science, Sydney, NSW 2001, Australia.

C Biosecurity Queensland, Robert Wicks Pest Animal Research Centre, Inglewood, Qld 4387, Australia.

D Corresponding author. Email: steven.lapidge@invasiveanimals.com

Wildlife Research 35(7) 651-662 http://dx.doi.org/10.1071/WR07072
Submitted: 22 June 2007  Accepted: 28 April 2008   Published: 17 November 2008


A literature review was conducted in order to identify unique weaknesses in the physiology or metabolism of pigs that could be targeted with specific chemicals (i.e. an ‘Achilles’ heel’ search). A promising weakness identified was the species’ susceptibility to methaemoglobin-forming compounds, most likely related to their uniquely low levels of methaemoglobin reductase. Further examination revealed that sodium nitrite is a cost-effective, readily available methaemoglobin-forming compound that is highly toxic to domestic pigs, which has caused numerous accidental poisonings. Pen trials on pigs showed that sodium nitrite delivered by gavage (>90 mg kg-1) and freely consumed in bait (>400 mg kg-1) caused rapid and lethal rises in methaemoglobin. Sodium nitrite appeared to be more humane than currently used toxins, with deaths following bait consumption being considerably quicker and with fewer symptoms (within 80 min of clinical signs beginning; clinical signs including infrequent vomiting, lethargy, ataxia and dyspnoea). The review also identified a second deficiency in the metabolism of pigs, namely high sensitivity to selective inhibition of cytochrome P450 liver enzymes. This leads to potentially lethal interactions between various drugs, such as two antibiotics, monensin and tiamulin. A pen trial confirmed that the antibiotic combination in a single gavage dose was reliably and rapidly lethal to pigs. However, its utility as a pig toxin is low, because it was unpalatable to pigs when delivered in bait and appeared to cause pain and suffering (leading to the early termination of pen trials). The findings presented here demonstrate the potential of sodium nitrite as an additional feral pig toxin.


Agar N. S. Harley D. 1972 Erythrocytic methaemoglobin reductases of various animal species. Experientia 28 1248 1249 doi:10.1007/BF01946202

Bartik M. , and Piskac A. (1981). ‘Veterinary Toxicology.’ (Elsevier: New York.)

Beutler E. Mikus B. J. 1961 The effect of sodium nitrite and para-aminopropriophenone abministration on blood methemoglobin levels and red blood cell survival. Blood 18 455 467

Bodansky O. 1951 Methemoglobinemia and methemoglobin-producing compounds. Pharmacological Reviews 3 144 196

Boink A. Speijers G. 2001 Health effects of nitrates and nitrites, a review. Acta Horticulturae 563 29 36

Bouchet G. Bouchet A. 1938 Toxicity of sodium nitrite (translated abstract from the Veterinary Bulletin). Bulletin of the Academy of Veterinarians France 11 433 435

Bourque J. G. Smart M. Wobeser G. 1986 Monensis toxicity in lambs. The Canadian Veterinary Journal. La Revue Veterinaire Canadienne 27 397 399

Buddle R. J. (2000). Differential diagnosis of diseases of pigs. The University of Sydney Post Graduate Foundation in Veterinary Science, University of Sydney, Sydney.

Calabrese E. J. Gareffl J. A. Stanek E. J. 1992 The effects of joint exposures to environmental oxidants on methaemoglobin formation: Copper/nitrite and copper/chlorite. Journal of Environmental Science and Health. Part A, Environmental Science and Engineering & Toxic and Hazardous Substance Control 27 629 642

Choquenot D. , McIlroy J. , and Korn T. (1996). ‘Managing Vertebrate Pests: Feral Pigs.’ (Ed. M. Bomford.) (Bureau of Resource Sciences & Australian Government Publishing Service: Canberra.)

Clarke E. G. C. 1976 Species differences in toxicology. The Veterinary Record 98 215 218

Counter D. E. Giles N. Redmond R. 1975 Stored rainwater as a cause of nitrite poisoning in pigs. The Veterinary Record 96 412

Cowled B. , and O’Connor C. (2004). A project that investigates current options for managing feral pigs in Australia and assesses the need for the development of more effective and humane techniques and strategies – Stage 3 Report. Pest Animal Control Cooperative Research Centre, Canberra, Australia. Available from

Cowled B. D. Gifford E. Smith M. Staples L. Lapidge S. J. 2006 a Efficacy of manufactured PIGOUT® baits for localised control of feral pigs in the semiarid Queensland rangelands. Wildlife Research 33 427 437 doi:10.1071/WR05083

Cowled B. D. Lapidge S. J. Smith M. Staples L. 2006 b Attractiveness of a novel omnivore bait, PIGOUT®, to feral pigs (Sus scrofa) and assessment of risks of bait uptake by non-target species. Wildlife Research 33 651 660 doi:10.1071/WR06054

Cowled B. D. Lapidge S. J. Hampton J. O. Spencer P. B. S. 2007 Measuring the demographic and genetic effects of pest control in a highly persecuted feral pig population. Journal of Wildlife Management 70 1690 1697

Dollahite J. W. Rowe L. D. 1974 Nitrate and nitrite intoxication in rabbits and cattle. The Southwestern Veterinarian 27 246 248

Drake J. N. 1981 Monensin–tiamulin interaction risk to pigs. The Veterinary Record 108 219 220

Druckery V. H. Steinhoff D. Beuthner H. Schneider H. Klärner P. 1963 Screening of nitrite for chronic toxicity in rats. Arzneimittel-Forschung 13 320 323

Egyed M. N. Hanji V. 1987 Factors contributing to recent outbreaks of acute nitrate poisoning in farm ruminants. Israel Journal of Veterinary Medicine 43 50 55

Fink J. 1981 Drug interactions: adverse effects on fowls of monensin and tiamulin in combination. [Translation] Deutsche Tierarztliche Wochenschrift 88 228 231

Fitzpatrick R. J. 1952 The toxicity of red squill to domesticated animals. The Journal of Comparative Pathology and Therapeutics 62 23 40

Fleming P. J. S. Choquenot D. Mason R. J. 2000 Aerial baiting of feral pigs (Sus scrofa) for the control of exotic disease in the semiarid rangelends of New South Wales. Wildlife Research 27 531 537

Fleming P. J. S. Allen L. R. Lapidge S. J. Robley A. Saunders G. R. Thomson P. C. 2006 A strategic approach to mitigating the impacts of wild canids: proposed activities of the Invasive Animals Cooperative Research Centre. Australian Journal of Experimental Agriculture 46 753 762 doi:10.1071/EA06009

Fisher P. O’Connor C. 2007 Oral toxicity of p-aminopropiophenone to ferrets. Wildlife Research 34 19 24 doi:10.1071/WR06125

Gibson R. 1975 An outbreak of nitrite poisoning in sows. The Veterinary Record 96 270

Gwatkin R. Plummer P. J. G. 1946 Toxicity of certain salts of sodium and potassium for swine. Canadian Journal of Comparative Medicine 10 188 190

Hone J. 1983 A short-term evaluation of feral pig eradication at Willandra in western New South Wales. Australian Wildlife Research 10 269 275

Hone J. Kleba R. 1984 The toxicity and acceptability of warfarin and 1080 poison to penned feral pigs. Australian Wildlife Research 11 103 111 doi:10.1071/WR9840103

Hone J. Pedersen H. 1980 Changes in a feral pig population after poisoning. Vertebrate Pest Conference 9 176 182

Imaizumi K. Tyuma I. Imai K. Kosaka H. Ueda Y. 1980 In vivo studies on methemoglobin formation by sodium nitrite. International Archives of Occupational and Environmental Health 45 97 104 doi:10.1007/BF01274129

Kovacs J. Balintffy I. Schink Z. 1960 Aetiology and treatment of methaemoglobinaemia in pigs. [Translated abstract from the Veterinary Bulletin] Magyar Allatorvosok Lapja 15 216 222

Kozma A. Szilagyi M. 1967 Plant, drinking water, and soil examinations in relation to methaemoglobinaemia of swine. [Translated abstract from the Veterinary Bulletin] Magyar Allatorvosok Lapja 22 257 261

Lewis D. 1950 The metabolism of nitrate and nitrite in the sheep. 1. The reduction of nitrate in the rumen of the sheep. Biochemical Journal 48 175 180

Lin J. H. 1995 Species similarities and differences in pharmocokinetics. Drug Metabolism and Disposition 23 1008 1021

Littin K. E. , and O’Connor C. E. (2002). Guidelines for assessing the welfare impacts of vertebrate poisons. Landcare Research Contract Report: LC0203/006. Landcare Research, Lincoln, New Zealand.

London W. T. Henderson W. Cross R. F. 1967 An attempt to produce chronic nitrite toxicosis in swine. Journal of the American Veterinary Medical Association 150 398 402

Luke D. 1954 Liver dystrophy associated with coal tar pitch poisoning in the pig. The Veterinary Record 66 643 645

Marks C. 2001 The Achilles’ heel principle. Australasian Vertebrate Pest Conference 12 330 335

Martin G. R. Twigg L. E. 2002 Sensitivity to sodium fluroacetate (1080) of native animals from north-western Australia. Wildlife Research 29 75 83

McIlroy J. C. 1983 The sensitivity of Australian animals to 1080 poison. V. The sensitivity of feral pigs, Sus scrofa, to 1080 and its implications for poisoning campaigns. Australian Wildlife Research 10 139 148 doi:10.1071/WR9830139

McIlroy J. C. 1986 The sensitivity of Australian animals to 1080 poison. IX. Comparisons between the major groups of animals, and the potential danger non-target species face from 1080-poisoning campaigns. Australian Wildlife Research 13 39 48 doi:10.1071/WR9860039

McParland P. J. McRory F. J. Bell N. Walls T. J. R. Manson W. H. S. 1980 Nitrite poisoning in pigs. The Veterinary Record 106 201

Miller D. J. S. O’Connor J. J. Roberts N. L. 1986 Tiamulin/salinomycin interactions in pigs. The Veterinary Record 118 73 75

Mitchell J. (2003). Alternative baiting strategies for feral pig control and disease monitoring, final report to the Bureau of Rural Sciences National Feral Animal Control Program. Unpublished report.

Nebbia C. Ceppa L. Dacasto M. Nachtmann C. Carletti M. 2001 Oxidative monensin metabolism and cytochrome P450 3A content and functions in liver microsomes from horses, pigs, broiler chicks, cattle and rats. Journal of Veterinary Pharmacology and Therapeutics 24 399 403

O’Brien P. 1986 An approach to the design of target-specific vertebrate pest control systems. Vertebrate Pest Conference 12 247 252

O’Brien P. H. 1988 The toxicity of sodium monofluoroacetate (compound 1080) to captive feral pigs. Australian Wildlife Research 15 163 170 doi:10.1071/WR9880163

O’Brien P. H. Lukins B. S. 1990 Comparative dose–response relationships and acceptability of warfarin, brodifacoum and phosphorus to feral pigs. Australian Wildlife Research 17 101 112 doi:10.1071/WR9900101

O’Brien P. H. Kleba R. E. Beck J. A. Baker P. J. 1986 Vomiting by feral pigs after 1080 intoxication: non-target hazard and influence of anti-emetics. Wildlife Society Bulletin 14 425 432

Bartik M. , and Piskac A. (1981). ‘Veterinary Toxicology.’ (Elsevier: Amsterdam.)

Plumlee K. H. Johnson B. Galey F. D. 1995 Acute salinomycin toxicosis of pigs. Journal of Veterinary Diagnostic Investigation 7 419 420

Pott J. M. Skov B. 1981 Monensin–tiamulin interactions in pigs. The Veterinary Record 109 545

Prescott J. F. (2000). Miscellaneous antibiotics: ionophores, nitrofurans, nitroimidazoles, rifamycins and others. In ‘Antimicrobial Therapy in Veterinary Medicine’. 3rd edn. (Eds J. F. Prescott, J. D. Baggot and R. D. Walker.) pp. 339–366. (Iowa State University Press: Ames, IA.)

Radostits O. M. , Gay C. C. , Blood D. C. , and Hinchcliff K. W. (2000). ‘Veterinary Medicine: A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses.’ 9th edn. (W.B. Saunders Co.: Philadelphia, PA.)

Ratz V. Laczay P. Mora Z. Csiko G. Monostori K. Vereczkey L. Lehel J. Semjen G. 1997 Recent studies on the effects of tiamulin and monensin on hepatic cytochrome P450 activities in chickens and turkeys. Journal of Veterinary Pharmacology and Therapeutics 20 415 418

Riemann H. 1950 On the toxicity of hydroxylamine. Acta Pharmacologica Sinica 6 285 292

Robin H. Harley J. D. 1966 Factors influencing response of mammalian species to the methaemoglobin reduction test. The Australian Journal of Experimental Biology and Medical Science 44 519 526

Robinson W. D. 1942 Mangel poisoning in pigs. New Zealand Journal of Agriculture Research 65 199 202

Rockwood G. A. Armstrong K. R. Baskin S. I. 2003 Species comparison of methemoglobin reductase. Experimental Biology and Medicine 228 79 83

Savarie P. J. Ping P. H. Hayes D. J. Roberts J. D. Dasch G. L. Felton R. Schafer E. W. Jr. 1983 Comparative acute oral toxicity of para-aminopropiophenone. Bulletin of Environmental Contamination and Toxicology 30 122 126

Sharp T. , and Saunders G. (2004). Model code of practice for the humane control of feral pigs. NSW Department of Primary Industries, Orange.

Shimada T. Mimura M. Inoue K. Nakamura S. Oda H. Ohmori S. Yamazaki H. 1997 Cytochrome P450-dependent drug oxidation activities in liver microsomes of various animal species including rats, guinea pigs, dogs, monkeys, and humans. Archives of Toxicology 71 401 408 doi:10.1007/s002040050403

Sisk D. B. Carlton W. W. 1972 Effect of dietary protein concentration on response of miniature swine to afla toxins. American Journal of Veterinary Research 33 107 114

Smith J. E. Beutler E. 1966 Methemoglobin formation and reduction in man and various animal species. The American Journal of Physiology 210 347 350

Sofia A. Liu W. T. Ong S. L. Ng W. J. 2004 In-situ characterization of microbial community in an A/O submerged membrane bioreactor with nitrogen removal. Water Science and Technology 50 41 48

StatsDirect Ltd (2005). StatsDirect Statistical Software. Accessed online 21 June 2007 at
http://www.statsdirect.com England: StatsDirect Ltd. 2005.

Twigg E. L. Lowe T. Martin G. Everett M. 2005 Feral pigs in north-western Australia: basic biology, bait consumption, and the efficacy of 1080 baits. Wildlife Research 32 281 296 doi:10.1071/WR04110

Umemura T. Kawaminami K. Goryo M. Itakura C. 1985 Enhanced myotoxicity and involvement of both type I and II fibers in monensin–tiamulin toxicosis in pigs. Veterinary Pathology 22 409 414

Wanntorp H. , and Swahn O. (1953). The toxicity of whey for swine in conjunction with bacterial reduction of nitrate to nitrite. In ‘Proceedings of the XVth International Veterinary Congress, Stockholm. Part 1’. pp. 496–501.

Wickstrom M. L. Eason C. T. 1999 Literature search for mustelid-specific toxicants. Science for Conservation 127 57 65

Witkamp R. F. Nijmeijer S. M. Csiko G. Van Miert A. S. J. P. A. M. 1994 Tiamulin selectively inhibits oxidative hepatic steroid and drug metabolism in vitro in the pig. Journal of Veterinary Pharmacology and Therapeutics 17 317 322

Williams A. T. (1948). Sodium fluoracetate poisoning. Hospital Corps Quarterly. United States Government Printing Office, Navy Department, Washington, DC.

Winks W. R. Sutherland A. K. Salisbury R. M. 1950 Nitrite poisoning of pigs. The Queensland Journal of Agricultural Science 7 1 14

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