As we see the final parting shots of a tepid winter, the warmer weather brings a couple of common dangers to parks, gardens and the countryside.
The oak processionary moth (Thaumetopoea processionea) is a native of southern Europe that was accidentally introduced into the Britain in 2005 on oak trees imported from continental Europe. The first outbreak was identified formally in west London in 2006 and the latest data on its presence are available here. As with many invasive species, it is not a problem in its native environment because predators and other environmental factors have evolved to keep populations in check. It has now become a major pest in London where they not only threaten the health of many oak species but pose a danger to human and animal health too. The caterpillars are covered in thousands of tiny hairs which contain the urticating substance thaumetopoein as a defence mechanism to prevent the caterpillars form beaing eaten. Contact with the hairs can cause itching skin rashes, sore throat, breathing difficulties and eye problems in humans and animals that come into contact with the caterpillars or their nests or if the hairs are blown by the wind.
White, silken webbing nests are built in early summer on the trunks and branches of oak trees and white, silken trails can be seen on the trunks and branches, although they blend into the tree after time. Nests are hemispherical, tear-drop shaped, bag-like or like a blanket stretched around part of a trunk or branch and range in size from and inch and a half across to several feet from ground level to high in the oak tree. They can also fall onto the ground. The caterpillar gets its name from the nose-to-tail processions that they make, often in an arrow formation, with a single leader and subsequent rows of several caterpillars abreast.
The Forestry Commission and Defra are working with entomologists from the Forest Research agency and local authorities to eradicate popoulations and many parks spray annually. However, the Veterinary Poisons Information Service has advised on a case of a dog that mouthed plant material from a nest of processionary moth caterpillars and developed tongue necrosis. The damage to her tongue was caused by thousands of hairs penetrating the tissue and by a reaction to the toxic compound thaumetopoein. Signs after exposure in the mouth include hypersalivation, pain, dysphagia, oedema (lips, facial, sublingual, submandibular, tongue), facial pruritis, blisters and necrosis of the tongue, submandibular lymphadenomegaly, pyrexia, vomiting, laryngeal oedema, respiratory distress and cyanosis. There may also be a reaction in the skin and eyes. Prompt treatment is essential.
All cases or sightings of these caterpillars should be reported to the Forestry Commission (or 0300 067 4442) or the relevant local authority.
The adder (Vipera berus) is the UK’s only venemous snake and lives in woodland, heathland and moorland and is a grey/brown colour with a distinctive zig-zag pattern down its back and a red eye. Like most snakes, it mostly avoids people but dogs (and people) can be at risk from being bitten when they tread on snakes hidden in undergrowth or surprise one at close quarters. Although they usually hibernate between October to March, the recent unseasonally warm weather has resulted in four requests for assistance from the VPIS in the last week alone and other reports state that adders can be seen all year round in some parts of the UK. Bites generally happen around the legs, feet or face of a dog that may then exhibit rapid and painful swelling localised around two small puncture marks. Fang marks may not be visible under the swelling. This may progress to pale gums, salivating, lethargy and vomiting or diarrhoea. Bites can be fatal. the VPIS received notification of 101 cases of adder bites in dogs in 2015, five of which resulted in death.
If you suspect that your dog has been bitten, keep him calm and as quiet as possible to prevent the venom from circulating quickly in the bloodstream and get veterinary help immediately. Bites can be treated with just painkillers and anti-inflammatories but anti-venom is also available. This is a preparation designed for humans and may not be in stock in most vets, although they may be able to request a dose from another practice.