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Processionary moth caterpillar toxicity

ISSN 2398-2942


Synonym(s): Thaumetopoea spp

Introduction

  • Venoms are poisonous substances that certain animals can inject by means of a bite, sting or other sharp body feature.
  • Many caterpillars have defensive venom glands, that are associated with specialized bristles, known as urticating hairs. Pets are most commonly exposed to processionary moth caterpillars (Thaumetopoea spp).
  • Cause: Exposure to processionary moth caterpillars.
  • Signs: depends on region of body affected, but most commonly severe oral pain, particularly the tongue.
  • Diagnosis: physical examination and history.
  • Treatment: copious irrigation, analgesia and supportive care.
  • Prognosis: usually good, but depends upon the degree of damage to the tongue and/or severe allergic response.

Presenting signs

  • Restlessness, pain, swelling, redness, pruritus, localized irritation.
  • Dyspnea and dysphagia may accompany stings to the face, mouth and oropharynx.
  • In cases of anaphylaxis, bronchospasm, pulmonary edema, hemorrhage, laryngeal edema, as well as ptyalism, pruritus, vomiting, incoordination, coma and death may all be seen.

Acute presentation

  • In cases of anaphylaxis Anaphylaxis, bronchospasm, pulmonary edema, hemorrhage, laryngeal edema, as well as ptyalism, pruritus, vomiting, incoordination, coma and death may all be seen.

Geographic incidence

  • The spread of processionary moth caterpillars across Western Europe has increased the incidence of reactions to their urticating hairs. They are found in South East England, continental Europe, North Africa and the Middle East.
  • The shed hairs can persist in the environment for years.

Public health considerations

  • Processionary caterpillars are a public health risk as the urticating hairs can become airborne and can cause dermal, ocular and respiratory signs in pets, people and livestock.
  • Fallen nests are also a risk.
  • Sightings of these caterpillars may require reporting to the appropriate authority, such as the local council.
  • The main risk period in the UK/Europe is June to August.

Cost considerations

  • Minimal in most cases, but hospitalisation may be prolonged in animals that develop severe signs following contact with the urticating hairs of processionary caterpillars.

Special risks

  • Oropharyngeal edema, where present, may compromise respiration and make intubation difficult.
  • Urticating hairs of the Oak Processionary caterpillar (Thaumetopoea processionea) and Pine Processionary caterpillar (Thaumetopoea pityocampa) can cause intense swelling of the tongue and oral tissues if licked from the hair coat. This can lead to severe tissue damage and necrosis of the lingual tissues.

Pathogenesis

Etiology

  • The larvae of processionary moths can possess thousands of pointed, barbed hairs (setae). The hairs break at the slightest touch and can be airborne .
  • The adults and other larval stages are not hazardous, but the nests and cocoons contain the hairs.

Predisposing factors

  • Contact with the nest, cocoons, urticating hairs or caterpillars of processionary moths.

Pathophysiology

  • The hairs contain the toxic compound (or compounds) thaumetopoein (or an immunologically-related protein).
  • This compound activates mast cells by a direct non-immunological effect (non-IgE mediated) and a type I allergic hypersensitivity (IgE mediated mechanism).
  • There is also mechanical injury from penetration of the hairs.

Timecourse

  • Irritating effects from caterpillar hairs is immediate in onset.

Epidemiology

  • Processionary moth caterpillar infestations are spreading northward due to trade in oak plants and due to warming climate.

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 VetMed Resource.
  • Stone K, Sullivan L, Korman R (2023) Suspect severe gastroenteritis associated with ingestion of caterpillar setae fragments in a cat. Aust Vet J 101, (8), 296-301 PubMed.
  • Pouzot-Nevoret C, Cambournac M, Violé A, Goy-Thollot I, Bourdoiseau G, Barthélemy A (2018) Pine processionary caterpillar Thaumetopoea pityocampa envenomation in 11 cats: a retrospective study. J Feline Med Surg 20, (8), 685-689 PubMed.
  • Pouzot-Nevoret C, Cambournac M, Violé A, Goy-Thollot I, Bourdoiseau G, Barthélemy A (2017) Pine processionary caterpillar Thaumetopoea pityocampa envenomation in 109 dogs: A retrospective study. Toxicon 132, 1-5 PubMed.
  • Costa D, Esteban J, Sanz F, Vergara J, Huguet E (2016) Ocular lesions produced by pine processionary caterpillar setae (Thaumetopoea pityocampa) in dogs: a descriptive study. Vet Ophthalmol 19, (6), 493-497 PubMed.
  • Niza M E, Ferreira R L, Coimbra I V et al (2012) Effects of Pine Processionary Caterpillar Thaumetopoea pityocampa Contact in Dogs: 41 cases (2002-2006). Zoonoses and Public Health 59 (1), 35-38 PubMed.
  • Bruchim Y, Ranen E, Saragusty J, Aroch I (2005) Severe tongue necrosis associated with pine processionary moth (Thaumetopoea wilkinsoni) ingestion in three dogs. Toxicon 45, (4), 443-447 PubMed.

Other sources of information

  • Cohen R (1995) Systemic anaphylaxis. In: Current Veterinary Therapy XII. Small Animal Practice. Ed: J Bonagura. W B Saunders, USA.
  • Forestry Commission. Oak Processionary Moth (OPM). Information for the Public. Website: www.gov.co.uk.

Organization(s)