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Permethrin

Permethrin belongs to the family of pyrethroids which are synthetic compounds similar to the natural pyrethrins produced by Chrysanthemums and daisies. It is an odorless neurotoxin that is used in veterinary spot-on formulations and topical applications as well as the primary prescribed treatment for humans with lice or scabies. In numerous studies permethrin has been found to kill a wide variety of insects and it is described as the most effective clothing fabric impregnate available.

Also studies have been performed on the use of permethrin on dogs. Research mainly focused on the topical application of permethrin whereby the insecticide was applied directly on the coat of the animals. Reports have shown that permethrin sprays protect dogs against ticks and fleas (Endris et al 2003). Spot-on formulations containing permethrin have been evaluated in dogs and were shown to be effective for the control of fleas (Boushira et al, 2012).

Da Chrysanthmum

Chrysanthemum Flower

Although effective, the disadvantage of topical application of permethrin is the relatively short efficacy period. That’s why the concept of the Dog Armor long-lasting impregnated insecticidal Knockdown dog bed and coat were developed: dog beds and coats on which the repellent and insecticidal effect lasts as long as the average useful life of that gear even when it is used, exposed to adverse weather and washed regularly. It will reduce or eliminate the need of frequently repeated topical application of permethrin. The permethrin is applied to the Dog Armor dog bed and fly coats along with a binding substance that makes the insecticides stick to the fabric but also available to repel and knock down insects. It will remain effective for a sufficiently long period without being washed out. In fact, it is withstanding a large number of up to 70 washings.

In the past, numerous scientific researches have been carried out on the use of insecticide treated fabrics in the fight against insect born diseases. Applications of permethrin impregnated clothes have successfully been tested for malaria prevention in humans (Kinmani EW et al, 2006). Also permethrin impregnated uniforms have shown to provide significant protection of soldiers against malaria and sandfly fever (leishmaniasis) (Soto, J et al, 1995).

Permethrin is generally considered to be of low toxicity to dogs and other mammals (Richardson, 1999). When used as a directed by the manufacturer permethrin products are considered safe and effective, with a low risk of adverse reactions. Nevertheless, cats are highly sensitive to permethrin and clinical signs may develop after exposure to permethrin (SuttonNM et al, 2007).

The concentration of permethrin that is used on Dog Armor Knockdown gear is 0.5% w/w. This dosage is exactly the same as the dosage that is considered safe for insecticide treated uniforms for humans.

In short, the permethrin impregnation of Dog Armor Knockdown gear provides:

  • Invisible protection
  • Odorless insect control
  • Long-lasting (up to 70 washes) efficacy
  • Safe and highly effective option when used as a directed

Summaries of important related scientific articles are listed below.

Efficacy of permethrin, dinotefuran and pyriproxyfen on adult fleas, flea eggs collection, and flea egg development following transplantation of mature female fleas (Ctenocephalides felis felis) from cats to dogs

Bouhsiraa, E, E Lienarda, P Jacquieta, S Warinb, V Kaltsatosb, L Baduelb, M Franca. Veterinary Parasitology, Volume 190, Issues 3–4, 21 December 2012, Pages 541–546.

A novel spot-on formulation combining permethrin, pyriproxifen and dinotefuran (Vectra 3D™ spot-on solution for dogs) was evaluated in adult Beagle dogs in a study to determine adulticidal efficacy, egg laying inhibition and viability of Ctenocephalides felis felis eggs (development and emergence of fleas from the collected eggs). Prior to treatment sixteen dogs were checked for their ability to keep fleas 24 hours after infestation and were allocated to treatment groups: 8 dogs served as untreated controls, and 8 dogs were treated once with the tested formulation. The spot on was administered respecting the laboratory recommendations at a dosage of 65–126 mg/kg of permethrin; 8.9–17.4 mg/kg of dinotefuran and 0.8–1.5 mg/kg of pyriproxyfen. Each dog was infested with 100 adult cat fleas ready to lay eggs after 72 hours spent feeding on cats. Dogs were infested 24 hours after treatment and then weekly during 63 days. Eggs were collected and counted 24 hours after each infestation and dogs were combed 48 hours after each infestation. Fleas were counted and removed. Collected eggs were placed in incubator to study their development in larvae and into newly emerged adults. A single treatment provided 99.7% adulticidal efficacy on fleas within 48 hours after treatment and controlled re-infestations for up to 30 days (efficacy >96.20%, p < 0.05). The egg laying inhibition was over 92.3% for up to 29 days (p < 0.05). The adult emergence inhibition remained 100% during 8 weeks after treatment and was 99.8% nine weeks after treatment (p < 0.001).

Efficacy of two 65% permethrin spot-on formulations against induced infestations of Ctenocephalides felis (Insecta: Siphonaptera) and Amblyomma americanum (Acari: Ixodidae) on beagles.

Endris RG, Hair JA, Anderson G, Rose WB, Disch D, Meyer JA. Veterinary Therapeutics. 2003 Spring; 4(1):47-55.

The efficacy of two formulations of a topically applied 65% permethrin spot-on (Defend Exspot Treatment for Dogs, Schering-Plough Animal Health) was evaluated against experimental infestations of the cat flea Ctenocephalides felis and the lone star tick Amblyomma americanum in dogs. Eighteen dogs were randomly assigned to treatment with 65% permethrin in either diethylene glycol monomethyl ether (DGME; original formulation) or propylene glycol monomethyl ether (PGME) or to be untreated as a control. Treated dogs received either 1 (body weight < 15 kg) or 2 ml (body weight > or =15 kg) of the assigned formulation on Day 0. One hundred unfed, adult C. felis were placed on each dog on Days -6, -1, 4, 11, 18, 25, and 32. Fifty unfed, adult ticks were placed on each dog on Days -1, 3, 9, 16, 23, and 30. Live fleas and ticks were counted and removed on Days 3, 7, 14, 21, and 28. Treatment of dogs with the 65% permethrin in DGME reduced flea numbers by 90.4% to 99.9% from Days 3 through 21 (P < or =.05) and by 48.2% 28 days after treatment. Treatment of dogs with 65% permethrin in PGME reduced flea numbers by 93.7% to 99.7% from Days 3 through 28 and by 78.4% 35 days after treatment (P < or =.05). Treatment with 65% permethrin in DGME reduced tick numbers by 90% or more only on Day 7, whereas treatment with 65% permethrin in PGME reduced the number of live ticks by 90%or more on Days 7 and 14 and approached 90%(87.9%) on Day 21. Efficacy against fleas and ticks for the PGME formulation was significantly better (P < or =.05) than for the DGME formulation on Day 28. Findings in this study indicate that both the DGME and PGME formulations of 65% permethrin performed well in reducing numbers of live C. felis and A. americanum on laboratory beagles; however, the PGME formulation was effective approximately 1 to 2 weeks longer than the DGME formulation.

Use of insecticide-treated clothes for personal protection against malaria: a community trial

Kimani EW, JM Vulule, IW Kuria, and F Mugisha. Malaria Journal. 2006; 5: 63.

Background:  The study sought to determine the effect of using insecticide-treated clothes (ITCs) on personal protection against malaria infection. The specific objectives were to determine the effect of using ITCs on the rate of infection with malaria parasites and the effect on indoor mosquito density.

Methods: This study was done in Dadaab refugee camps, North Eastern Province Kenya between April and August 2002, and involved a total of 198 participants, all refugees of Somali origin. The participants were selected through multi-stage cluster sampling. Half of the participants (treatment group) had their personal clothes worn on a daily basis (Diras, Saris, Jalbaabs, Ma’awis and shirts) and their bedding (sheets and blankets) treated with insecticide (permethrin). The other half (comparison group) had their clothes treated with placebo (plain water). Indoor mosquito density was determined from twelve households belonging to the participants; six in the treatment block and six in the comparison block. During pre-test and post-test, laboratory analysis of blood samples was done, indoor mosquito density determined and questionnaires administered. Using STATA statistical package, tests for significant difference between the two groups were conducted.

Results: Use of ITCs reduced both malaria infection rates and indoor mosquito density significantly. The odds of malaria infection in the intervention group were reduced by about 70 percent. The idea of using ITCs for malaria infection control was easily accepted among the refugees and they considered it beneficial. No side effects related to use of the ITCs were observed from the participants.

Conclusion: The use of ITCs reduces malaria infection rate and has potential as an appropriate method of malaria control. It is recommended, therefore, that this strategy be considered for use among poor communities like slum dwellers and other underprivileged communities, such as street children and refugees, especially during an influx to malaria-prone regions. Further research on cost-effectiveness and sustainability of this strategy is worthwhile.

Permethrin Spot-On Toxicoses in Cats

Richardson, JA. Journal of Veterinary Emergency and Critical Care, Volume 10, Issue 2, pages 103–106, June 2000.

Spot-on insecticides are becoming a popular type of flea control for pets. Spot-on products available include those containing fipronil, imidicloprid, methoprene, and permethrin. Currently, over 15 brands of permethrin spot-on products are labeled for “use in dogs only.” These products contain high concentrations (45–65%) of permethrin insecticide and are becoming a very popular choice for flea and tick control for dogs. Cats are highly sensitive to permethrin and inappropriate or accidental application of these products would be fatal. Though they have a wise margin of safety when used appropriately on dogs, even small amount of permethrin spot-on products can cause severe clinical signs in cats. Indications of this species sensitivity have been documented by the National Animal Poison Control Center (NAPCC). In most cases, the owner applied the concentrated permethrin-containing poduct to cats accidentally or intentionally. In some situations, the exposure seems to have resulted when the product was used on the dog and cats were playing with dog. (ASPCA, NAPCC, Unpublished data, 1995–1997).

Efficacy of permethrin-impregnated uniforms in the prevention of malaria and leishmaniasis in Colombian soldiers.

Soto J, F Medina, N Dember, J Berman. Clinical Infectious Diseases. 1995 Sep;21(3):599-602.

We determined the efficacy of the use of permethrin-impregnated uniforms for prevention of malaria and leishmaniasis in a double-blind, randomized study of Colombian soldiers on patrol. In the study of malaria, soldiers were issued impregnated uniforms (i.e., a shirt, an undershirt, pants, socks, and a hat) or uniforms washed in water; the soldiers wore the uniforms day and night for a mean of 4.2 weeks and were observed for an additional 4 weeks. Three (3%) of 86 soldiers wearing impregnated uniforms contracted malaria, whereas 12 (14%) of 86 soldiers wearing control uniforms contracted malaria (P = .015). In the study of leishmaniasis (soldiers were in the area of endemicity for 6.6 weeks and were observed for 12 weeks thereafter), 4 (3%) of 143 soldiers wearing impregnated uniforms and 18 (12%) of 143 soldiers wearing control uniforms acquired disease (P = .002). In the leishmaniasis study, and presumably in the malaria study, breakthrough infections in the treated group were primarily due to bites in unclothed regions of the body (face and hands). Permethrin-treated uniforms were virtually nontoxic (there were only two cases of mild skin irritation among 229 subjects), and impregnation is quick and inexpensive. Impregnation of clothing with permethrin is suggested for non-immune populations who are likely to be exposed to malaria or leishmaniasis over a period of 1-2 months.

Clinical effects and outcome of feline permethrin spot-on poisonings reported to the Veterinary Poisons Information Service (VPIS), London

SuttonNM, N Bates, A Campbell. Journal of Feline Medicine & Surgery. Volume 9, Issue 4, August 2007, Pages 335–339.

Permethrin is a pyrethroid insecticide used in dermally applied spot-on flea treatments for dogs. Permethrin-based spot-on preparations are contraindicated in cats because of the high risk of toxicosis. The Veterinary Poisons Information Service (VPIS) is a 24-h access telephone service that provides veterinary professionals in the United Kingdom with information on the management of poisoned animals. In a review of 286 cases reported to the VPIS regarding inappropriate feline exposure to permethrin spot-on (PSO) preparations, 96.9% were symptomatic. Increased muscular activity (as evidenced by twitching, tremor, muscle fasciculations or convulsions) was common and occurred in 87.8% of cases. The duration of increased muscle activity was long, with convulsions lasting on average 38.9 h and tremors 32 h. Recovery typically occurred within 2 to 3 days but in some cases took 5 to 7 days. Death occurred in 10.5% of cases.

Pilot Study Assessing the Effectiveness of Long-Lasting Permethrin-Impregnated Clothing for the Prevention of Tick Bites.

Vaughn MF and SR Meshnick, 2011. Vector Borne and Zoonotic Diseases. 2011 Jul;11(7):869-75.

Introduction: Tick-borne diseases such as Lyme disease, Rocky Mountain spotted fever, and ehrlichiosis are a significant concern for many thousands of workers who have frequent and unavoidable exposure to tick-infested habitats. Many North Carolina state employees with outdoor occupations report multiple tick bites each year, indicating that existing tick preventive strategies may be underutilized or ineffective. Treatment of clothing with permethrin, a nontoxic chemical with insecticidal, knockdown, and repellent properties, is highly effective against ticks. However, most permethrin products must be reapplied after several washings to maintain insecticidal activity. Recently, a factory-based method for long-lasting permethrin impregnation of clothing has been developed by Insect Shield, Inc., that allows clothing to retain insecticidal activity for over 70 washes.

Methods: A non-randomized open label pilot study was conducted to determine the effectiveness of Insect Shield-treated clothing for the prevention of tick bites among 16 outdoor workers from the North Carolina Division of Water Quality under actual field conditions. Participants completed questionnaires at the start of follow-up (March, 2008) and at the end of follow-up (September, 2008), and tick bites and outdoor work hours were reported on weekly tick bite logs for the entire follow-up period.

Results: Subjects wearing Insect Shield-treated clothing had a 93% reduction (p < 0.0001) in the total incidence of tick bites compared to subjects using standard tick bite prevention measures.

Conclusion: This study provides preliminary evidence that long-lasting permethrin-impregnated clothing may be highly effective against tick bites.