ISSN 2398-2993      

Diquat poisoning

obovis
Contributor(s):

Nicola Bates

Alan Murphy


Introduction

  • Cause: ingestion or dermal exposure to diquat.
  • Signs: milk drop, gastrointestinal and renal signs.
  • Diagnosis: based on history and clinical signs.
  • Treatment: supportive, with adsorbents and rehydration.
  • Prognosis: good in cattle with mild signs, but poor in those renal, pulmonary or neurological signs.

Pathogenesis

Etiology

  • Diquat (diquat dibromide) is a non-selective foliage-applied dipyridilium contact herbicide and desiccant.
  • It is used for control of annual and aquatic weeds and as a pre-harvest desiccant.
  • It is inactivated on contact with soil.

Predisposing factors

General

  • Cattle in poor health or with pre-existing renal impairment may be more susceptible.

Pathophysiology

  • Diquat poisoning is characterized by gastrointestinal, renal and cerebrovascular effects.
  • Diquat is a potent redox cycler. In the presence of NADPH and cytochrome P450 it undergoes addition of a single electron to form a free radical. This is highly unstable and forms a superoxide free radical, which is also highly reactive. The anions formed interact with each other to form hydrogen peroxide and oxygen. Protective mechanisms are overwhelmed, and the superoxide anion free radicals damage and ultimately kill cells.
  • Paralytic ileus can occur with diquat and it thought to be responsible of the accumulation or sequestration of large volumes of fluid in the gut which in turn leads to hypovolemic shock.
  • Renal insufficiency is probably due to fluid loss and dehydration. Elevated creatine kinase and AST are probably due to hypoxic myofiber injury, resulting from dehydration and hypoperfusion.
  • Unlike paraquat, diquat does not cause pulmonary fibrosis since diquat is not actively taken up by lung tissue.
  • The oral LD50 in cattle in approximately 30 mg/kg of diquat ion (equivalent to 43.9 mg/kg of diquat bromide).
  • Death occurred in cattle exposed dermally to an estimated dose of 50-100 mg/kg.
  • Diquat is poorly absorbed from the gastrointestinal tract and mainly eliminated via the feces (usually >90%) during the first 24 hours, the small quantity absorbed is principally eliminated via the urine (<10%) with very small amounts in the milk (<0.02%).
  • In cattle fed silage containing diquat, residues were not detected in meat or milk; 40-45% of the ingested diquat was excreted in the feces and less than 10% in the urine.

Timecourse

  • Onset is usually at least 12-24 hours after ingestion and may be several days.
  • Death can occur within 36-48 hours after onset of signs.
  • Recovery may take several weeks.

Epidemiology

  • Diquat poisoning is only reported occasionally in cattle and is usually the result of accidental exposure, eg contamination of land by crop spraying, drinking from an old pesticide container or mixing of an ectoparasiticide product with diquat residue in an old pesticide container.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Magalhães N, Carvalho F & Dinis-Oliveira R J (2018) Human and experimental toxicology of diquat poisoning: Toxicokinetics, mechanisms of toxicity, clinical features, and treatment. Hum Exp Toxicol 37 (11), 1131-1160 PubMed.
  • Whiting T L, Smyrl T, Spearman J G & Kernatz S (2001) Diquat poisoning of dairy cattle by topical application. Can Vet J 42 (10), 799-801 PubMed.
  • Balla, F & Békéssy G (1986) Szarvasmarhak es juhok felheveny Reglone- (diquat-) mergezesenek elofordulasa. Outbreaks of subacute poisoning of cattle and sheep with Reglone (diquat). Magyar Állatorvosok Lapja 41 (11), 675-677.
  • Jopek Z, Kostowska B, Bohosiewicz M & Kramer H (1980) Zatrucie krow preparatem "Reglone" (dikwat). Poisoning of cows by Reglone (diquat). Medycyna Weterynaryjna 36 (8), 479-481.
  • Clark D G & Hurst E W (1970) The toxicity of diquat. Br J Ind Med 27 (1), 51-5 PubMed.
  • Thomas P & Amor O F (1968) A case of diquat poisoning in cattle. Vet Rec 83 (26), 674-6 PubMed.
  • Stevens M A & Walley J K (1966) Tissue and milk residues arising from the ingestion of single doses of diquat and paraquat by cattle. J Sci Food Agric 17 (10), 472-5 PubMed.
  • Black W J, Calderbank A, Douglas G & McKenna R H (1966) Residues in herbage and silage and feeding experiments following the use of diquat as a desiccant. J Sci Food Agric 17 (10), 506-9 PubMed.

Other sources of information

  • World Health Organization (WHO) (2013) Diquat. In: Pesticide Residues in Food. Report Joint FAO/WHO Meeting on Pesticide Residues (JMPR), Food and Agriculture Organization (FAO) of the United Nations. FAO Plant Production and Protection Paper 219. Available at http://apps.who.int (accessed 6 September 2018).

Organisation(s)

  • ASPCA Animal Poison Control Center. Tel: (888) 426-4435; Website: www.aspca.org.
  • Veterinary Poisons Information Service (VPIS). Tel: + 44 (0) 2073 055 055; Website: www.vpisglobal.com.

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