Method of pest control and article useful therefor

Details Method of pest control and article useful therefor Method of pest control and article useful therefor

1999-05-24

2001-04-10

Salimi, Ali R. (Department: 1648)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Biocides; animal or insect repellents or attractants

C424S403000, C008S115700, C008S532000, C008S922000

Reexamination Certificate

active

06214365

ABSTRACT:

FIELD OF THE INVENTION
The present invention related to the use of pesticide-impregnated linings and/or coverings to control house dust mite populations. In particular, the invention relates to pyrethroid-impregnated netting for use in covering, e.g. a mattress.
BACKGROUND TO THE INVENTION
The reported growth in house dust mite populations associated with domestic environments in Europe, the Americas, China and elsewhere is causing increasing concern. With the rising number of homes remaining at a constant favourable temperature and humidity, together with changes in house cleaning methods and types of bedding over the years, the numbers and survival of such creatures have risen sharply. House dust mites are scavengers on dead organic matter found in abundance in the home, feeding principally on the shed skin scales of humans. The mites, their faeces and products, are highly antigenic as contact or aero allergens in atopic diseases, e.g. eczema, asthma and allergic rhinitis. Mite allergy may trigger severe exacerbation that can be life-threatening in extrinsic asthma.
In addition, house dust mites have, in recent years, become an increased focus of concern as many experts consider them to be instrumental in initiating primary sensitisation leading to clinical asthma in very young children. It is believed that repeated exposure to the allergens produced by the mites can trigger early stages of asthma which will then become established as a chronic disease affected by a large range of different allergens in the environment.
There is also an overwhelming body of evidence that the presence of house dust mite faeces is instrumental in provoking asthma attacks in those with asthma or specific allergies, which cause immeasurable suffering, or even death.
House dust mites are to be found concentrated in many parts of the home, particularly soft furnishing, which provide them with a highly suitable environment. When they live in bedding, however, this brings them into the closest and most prolonged contact with humans. Pillows, duvets and mattresses have been found not only to house large populations of house dust mites, but also copious amounts of their faeces. The infestation cannot generally be removed by standard cleaning methods. The faecal pellets are particularly stable and resistant to removal from the fabric.
House dust mites are members of the family acaria, and one approach which could be contemplated to reduce the population of house dust mite would clearly be the use of an acaricide. However, in a domestic environment, this would cause many problems. For example, a well-known and highly effective acaricide is benzyl benzoate, but this is known to be very toxic to cats.
An alternative acaricide would be an organophosphate compound, some of which are well-know to be highly effective in eradicating mite infestation, particularly in farm animals. However, many such organophosphate compounds are toxic to humans and suspected, even at small exposures, to promote nervous system damage over the long term. Their use in domestic situations is accordingly not recommended.
In terms of the physical means used to reduce dust mite populations, one approach which has been suggested as acceptable in a domestic environment is that of using a dusting power containing suitable acaricide, and preparations have been made available commercially for this purpose, including some containing, as the acaricidal agent, pyrethroid compounds. These are know to be relatively non-toxic to humans, and have been much promoted, especially in domestic horticulture, as “natural insecticides”. some (not all) display acaricidal properties as well as insecticidal ones. However, the use of dusting powder does not provide prolonged protection against infestation, and depends particularly on the efficiency of “dusting”. In addition, the powder particles themselves may aggravate any asthmatic conditions which people coming into contact with them may have.
Control of insects in domestic environments has long been practised using impregnated textiles. Insecticide-impregnated netting has been used for decades as “mosquito netting”, with a view of preventing the spread of malaria and other insect vector borne diseases, not only by denying the insect physical access to the human body, but additionally by killing insects on contact with the insecticide in the netting. Such an approach clearly does nothing to reduce infestation already present in beds and soft furnishings.
A suggestion has been made to incorporate into the fibres used to make synthetic fibre netting a mite-proofing component (Fumiyasu, Japanese Patent Publication 3-220102 published Sep. 27, 1991). However, this approach traps the component within the body of each fibre and although it will have an effect, it will be attenuated, not least because the active acaricidal component will only be released by slow vaporisation, and at very low (and thus ineffective) concentration.
GENERAL DESCRIPTION OF THE INVENTION
We have now found that effective control of house dust mite populations can be actioned by using an acaricide-impregnated netting, for example in the form of a net cover fitted around a mattress, pillow or like article of bedding or upholstery, and wherein the acaricide is present attached to the exterior surfaces of the fibres of the yarn making up the net.
Thus, in a first aspect, the present invention provides, for use in the control of house dust mites using a pyrethroid insecticide, a pre-formed netting structure wherein the netting structure is formed of yarns formed of a plurality of fibres, and wherein, attached to the exterior surfaces of the fibres, are particles of a pyrethroid acaricide. The netting structure is used by located it adjacent a surface, and preferably enclosing, a house dust mite habitat such as an article of bedding or upholstery.
When so constructed and used, any house dust mites emerging from the habitat can come into contact with the acaricide particles, with consequent lethal effect. In addition, as the netting is moved adjacent the habitat—e.g. by sitting on a cushion or getting into a bed—particles of the acaricide become detached from the fibres of the yarns forming the netting and permeate into the habitat, there to exert their lethal properties.
The netting structure of the invention may be made simply by impregnating preformed netting with a liquid formulation containing a pyrethroid acaricide, and drying the netting appropriately. It may then be applied around e.g. a pillow, mattress, duvet, cushion, bean bag or domestic pet bed, preferably by being first formed using conventional garment manufacturing techniques, into a close-fitting cover which covers at least a part, but preferably substantially the entire surface of the article.
A wide variety of pyrethroid compounds may be used in practising the present invention, including both natural and synthetic ones. The choice of which to use is conditioned, apart from the usual considerations of availability and price, by two main factors, effectiveness and toxicity. The effectiveness of pyrethroid compounds as acaricides varies; one with high effectiveness against mites should be chosen in preference to others. Since the compounds are to be used in situations where there will inevitably be human contact, ones with lower mammalian toxicity are preferably selected, provided they are adequately effective. Two particular pyrethroid compounds meet these criteria well, viz permethrin and deltamethrin, both of which are widely available.
The netting used may be made of any suitable fibre yarn, in particular nature fibres such as cotton or linen, or of synthetic yarns such as nylon or polyester. Mixed fibre yarns, including mixtures of natural and synthetic fibres may be used. The netting may be made by conventional textile manufacturing processes such as weaving or knitting.
the netting is impregnated, as indicated above, by using a liquid formulation containing the pyrethroid acaricide at a suitable concentration, and with the particles of the pyrethroid acaricide suitably

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