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PubMed1979

Demographic study of head lice infestations in Sacramento County school children.

Head lice infestations have become a problem in school children in Sacramento County. An open study was conducted to determine how widespread head lice infestations were among preschool and elementary school children in Sacramento County and to see how effective a newly marked ever-the-counter pediculicide containing 0.3% pyrethrins synergized by 3.0% piperonyl butoxide was. The public health nurse for this study visited the homes of all reported patients infested with head lice. She verified and provided the pyrethrins-based treatment for 248 children, aged 6 months to 12 years. The children were Caucasian, Mexican-American, black and other ethnic backgrounds and from low, middle and upper income levels. All the patients were successfully treated, and the school children were able to return to their classs in a short time.

California↗

PubMed1980

Pyrethrum flowers and pyrethroid insecticides.

The natural pyrethrins from the daisy-like flower, Tanacetum or Chrysanthemum cinerariifolium, are nonpersistent insecticides of low toxicity to mammals. Synthetic analogs or pyrethroids, evolved from the natural compounds by successive isosteric modifications, are more potent and stable and are the newest important class of crop protection chemicals. They retain many of the favorable properties of the pyrethrins.

Agriculture↗

PubMed1962

Studies on aircraft disinsection at "blocks away".

With a view to expediting as much as possible the disinsection of aircraft required under the International Sanitary Convention for Aerial Navigation, experiments were performed under operating conditions on the disinsection of passenger cabins after the closing of the aircraft doors following embarkation but before take-off (designated "blocks away" disinsection) with single-use, disposable aerosol dispensers. A formulation containing 1.6% by weight pyrethrum extract (25% pyrethrins) and 3% DDT at a dosage of 10 g per 1000 cubic feet (35 g/100 m(3)) gave satisfactory control of non-resistant mosquitos and created no passenger reaction. A formulation containing 3.40% pyrethrum extract (20% pyrethrins) and 1.17% DDT at a dosage of 14-19 g per 1000 cubic feet (48-64 g/100 m(3)) was biologically effective for both resistant and non-resistant mosquitos but was markedly irritant to some passengers. The authors suggest lines along which further research might be conducted.

Aerosols↗

PubMed2005

Ornithonyssus bacoti infestation and elimination from a mouse colony.

Skin lesions, consisting of nonspecific bites with intense pruritus and excoriation of the skin, were found on personnel working in an animal colony primarily housing mice. The tropical rat mite, Ornithonyssus bacoti, was diagnosed from mites trapped on insect-monitoring sticky traps and collected from mouse cages in the colony. Because these mites do not live on mice but only come to feed when the animals are in their nest, an initial attempt was made to eliminate the mites with a thorough cleaning of the facility. Clidox foam was applied to the entire room with a foaming machine. Then the mice were transferred into the sanitized cages in the cleaned room. The numbers of mites were reduced to the point that they were no longer noticed in the colony, but the mites returned within 2 weeks. The mites were successfully eliminated with the use of permethrin-impregnated cotton balls in the mouse cages for 8 weeks and treatment of the premises. Treatment of the premises included spraying floors and walls of all rooms housing mice and adjacent hallways in the colony with pyrethrin spray by a commercial pest control company. To prevent one room of rabbits from maintaining the infestation, they were treated weekly with an organic pyrethrin dust. Insect sticky traps have remained negative for mites for more than 3 years after treatment.

Animals↗

PubMed1981

Pyriderm shampoo in the treatment of Pediculosis capitis.

112 patients with head lice were treated with a shampoo containing pyrethrins. All were treated twice with an interval of one week. At examination immediately before the second treatment, 6 patients had small, newly hatched lice, and one patient had both small and mature lice--probably due to reinfestation. This patient was lice-free after the third treatment, the other patients after the second treatment. It is concluded that pyrethrins are highly effective against head lice and have the advantages of a low toxicity to mammals and a short contact time.

Humans↗

PubMed2000

Efficacy and safety of selamectin against fleas and heartworms in dogs and cats presented as veterinary patients in North America.

A series of randomized, controlled, masked field studies was conducted to assess the efficacy and safety of selamectin in the treatment of flea infestations on dogs and cats, and in the prevention of heartworm infection in dogs. In addition, observations were made on the beneficial effect of selamectin treatment on dogs and cats showing signs of flea allergy dermatitis (FAD). In all studies selamectin was applied topically, once per month, in unit doses providing a minimum dosage of 6mgkg(-1). Dogs and cats with naturally occurring flea infestations, some of which also had signs associated with FAD, were assigned randomly to receive three months of topical treatment with selamectin (220 dogs, 189 cats) or a positive-control product (dogs: fenthion, n=81; cats: pyrethrins, n=66). Selamectin was administered on days 0, 30, and 60. Day 0 was defined as the day that the animal first received treatment. Flea burdens were assessed by flea comb counts and clinical evaluations of FAD were performed before treatment, and on days 14, 30, 60, and 90. On days 30, 60, and 90, mean flea counts in selamectin-treated dogs were reduced by 92.1, 99.0, and 99.8%, and mean flea counts in fenthion-treated dogs were reduced by 81.5, 86.8, and 86.1%, respectively, compared with day 0 counts. Also, on days 30, 60, and 90, mean flea counts in selamectin-treated cats were reduced by 92.5, 98.3, and 99.3%, and mean flea counts in pyrethrin-treated cats were reduced by 66.4, 73.9, and 81.3%, respectively, compared with day 0 counts. Selamectin also was beneficial in alleviating signs in dogs and cats diagnosed clinically with FAD. A total of 397 dogs free of adult heartworm infection from four heartworm-endemic areas of the USA were allocated randomly to six months of treatment with selamectin (n=298) or ivermectin (n=99). Selamectin achieved a heartworm prevention rate of 100%, with all dogs testing negative for microfilariae and adult heartworm antigen on days 180 and 300. Selamectin was administered to a total of 673 dogs and 347 cats having an age range of 6 weeks to 19 years (3954 doses). The animals included 19 purebred or crossbred Collies (Bearded, Border, and unspecified). There were no serious adverse events. Results of these studies indicated that selamectin was highly effective in the control of flea infestations in dogs and cats without the need for simultaneous treatment of the environment or of in-contact animals and also was beneficial in alleviating signs associated with FAD. Selamectin also was 100% effective in preventing the development of canine heartworms and was safe for topical use in dogs and cats.

Animals↗

PubMed2002

Impact of an insecticide resistance strategy for house fly (Diptera: Muscidae) control in intensive animal units in the United Kingdom.

A strategy for house fly (Musca domestica L.) control in intensive animal units in the United Kingdom was proposed by the Pesticide Safety Directorate (PSD) of the Ministry of Agriculture, Fisheries and Food in 1993. An advice leaflet was circulated to farmers, and label recommendations for insecticides used to control house flies were altered to prevent their long-term and frequent use. A study was carried out between 1996 and 1998 to gather data on insecticide use and resistance in house fly populations and compared with results from a study carried out in 1990-1992 to assess the impact of the 1993 label recommendations. As in the 1990-1992 study, resistance to methomyl, azamethiphos and pyrethrins + piperonyl butoxide was assessed. Larvicide tests with cyromazine, which had recently been released in the United Kingdom, were also included in this study. Most of the farmers claimed to have received and read the PSD insecticide advice leaflet, and half claimed to have altered insecticide treatments as a result. Comparing results for insecticides used before and after 1993, the proportion of farmers claiming to have used each of the insecticides had decreased. However, there had been no amelioration in resistance to synergised pyrethrins, and the number of house fly populations with reduced response to the insecticide baits had increased between 1990-1992 and 1996-1998. All the house fly populations tested were fully susceptible to cyromazine. There is an urgent need, therefore, to devise new strategies and particularly to minimize the risk of selecting for resistance to cyromazine.

Animals↗

PubMed2004

Clinical update on resistance and treatment of Pediculosis capitis.

The anatomy and physiology of head lice make them extremely adaptable to their human hosts but also difficult to eradicate. Their coloring and small size make them difficult to see, and the larvae, or nymphs, have multiple exoskeletons for protection. When exposed to pediculicides, a nymph can shed its outer exoskeleton and receive only a sublethal dose. Through natural selection, head lice have developed resistance to commonly used pediculicides, making it increasingly difficult to eliminate infestations. Other contributors to resistance include changes in formulations of pediculicides and improper use. Over the last 20 years, the efficacy of pyrethrins has declined because of necessary safety changes in formulations and unintentional effects of new packaging on chemical components of these products. Pediculicides designed to be applied to wet hair may become too diluted to produce the desired effect. Patients also may use too little product to conserve costs. The combination of decreased product efficacy and exposure of head lice to diluted or insufficient amounts of pediculicides has reduced their effectiveness substantially. Studies comparing the current efficacy of several over-the-counter and prescription pediculicides with effectiveness in the 1980s has shown that OVIDE (malathion) Lotion, 0.5% is the only product that has retained its efficacy over time. The efficacy of over-the-counter pyrethrin products had declined significantly, and lindane, another prescription product, was least effective of all products tested both in the 1980s and in more recent studies. In addition to retaining its efficacy, malathion 0.5% also is effective when applied for only 20 minutes. The shorter application time is safer for children and also decreases the likelihood that residual product remains in the hair, further contributing to resistance.

Animals↗

PubMed1987

Treatment of pediculosis pubis. Clinical comparison of efficacy and tolerance of 1% lindane shampoo vs 1% permethrin creme rinse.

Pediculosis pubis (PP) is a common sexually transmitted disease. Current therapy with 1% lindane or various synergized pyrethrins as a single dose has been accepted as adequate by the medical community. We treated 53 men with the diagnosis of PP with either 1% lindane (Kwell) shampoo for four minutes or 1% permethrin (Nix) creme rinse for ten minutes, according to random assignment. All patients combed with fine-toothed combs immediately after therapy. They were examined for tolerance and efficacy at 24 to 48 hours and again at ten days (eight- to 12-day range). In the lindane group, ten (40%) of 25 subjects were infested at the final assessment. In the permethrin group, 12 (43%) of 28 subjects were infested at the final assessment. The difference was not statistically significant. Both treatments were well tolerated, with one mild adverse reaction in each group. We concluded that both agents were equivalent in the treatment of PP. On the basis of the high failure rate, we propose that the therapy of PP with any agent should include a second treatment at ten days.

Adult↗

PubMed2002

Toxicity of biorational insecticides: activity against the green peach aphid, Myzus persicae (Sulzer).

The relationship between dose for each of four biorational insecticides (pyrethrins, neem extract, capsiacin extract, insecticidal soap) and mortality of the green peach aphid (Myzus persicae) was determined using a laboratory bioassay. These insecticides were toxic to aphids and paired mixtures of the insecticides provided synergistic activity as measured by aphid mortality under the laboratory bioassay conditions. Capsiacin extracts were found to provide low levels of mortality alone but acted synergistically in mixtures with the other insecticides and provided higher than expected levels of mortality. Activity as determined in the laboratory for each insecticide was not evident under field-use conditions in five separate experiments. Under field conditions and using common application methods, these insecticides did not provide significant levels of control of aphids.

Agriculture↗

PubMed1996

Handwipe sampling and analysis procedure for the measurement of dermal contact with pesticides.

A handwipe sampling and analysis procedure was developed for the measurement of dermal contact to pesticides. This procedure utilizes cellulose dressing sponges wetted with 2-propanol. A two-step wiping procedure is described that ensures that the entire hand is sampled. Removal efficiency experiments show that dry residues of the pesticides chlorpyrifos and pyrethrin I are quantitatively removed from hands immediately following contact. Results suggest that the procedure may remove pesticide residues that are deeply embedded in the skin and not removed by soap-and-water washing. Extraction efficiency studies for 29 other pesticides show that the proposed extraction method may be applicable for a wide range of pesticides including phenoxy-acid herbicides. Field testing of the procedure indicates that it is easily implemented by sampling personnel and readily accepted by children.

Child↗

PubMed1995

Pyrethroids, nerve poisons: how their risks to human health should be assessed.

The extensive worldwide efforts of structural modification of natural pyrethrins for better performances have resulted in successful development of a wide variety of synthetic pyrethroids with tremendously high efficacy, knock-down activity or vapor action, and/or with acceptable environmental stability and safety. Currently these pyrethroids including their preferentially manufactured stereoisomers are widely used in agriculture, and for public health as well as household insect control. The detailed toxicology and metabolism studies intended to attain human risk assessment have revealed that with voltage-dependent sodium channel as target site pyrethroids induce pronounced repetitive activity characterized grossly by tremor, hypersensitivity, choleoathetosis, and salivation. In addition, so-called cyano-pyrethroids cause transient skin paresthesia in workers. With regard to tumorigenicity, mutagenicity, teratogenicity and developmental toxicity, no significant findings have been reported. Pyrethroids are eliminated from the animals quite rapidly and completely, undergoing oxidation and ester hydrolysis followed by various conjugations, with low tissue residues. Thus, overall, sound scientific bases exist for human risk assessment under the present usage conditions.

Animals↗

PubMed2005

Biomarker of pyrethrum exposure.

Pyrethrum as well as synthetic pyrethroids like allethrin, resmethrin, phenothrin, tetramethrin, cyfluthrin, cypermethrin, deltamethrin or permethrin are among the insecticides most often used worldwide. With a sensitive and valid gas-chromatographic-high resolution mass spectrometric method, it is possible to detect all pyrethrum and pyrethroid metabolites in one analytical run. Thus, for the first time a background level of trans-chrysanthemumdicarboxylic acid (CDCA) in urine (95th percentile: 0.15 microg/l) as a characteristic, e.g. for a pyrethrum exposure was found. Following a pyrethrum exposure lasting 1 day, CDCA was found in 27 out of 30 subjects with concentrations going up to 54 microg/l urine (mean: 1.1+/-4.4 microg/l). To obtain information about the elimination kinetics of pyrethrum in humans, urinary excretion of CDCA was investigated in three volunteers after oral intake of 0.3mg pyrethrin I. CDCA was detected during the first 36 h after intake with elimination being most rapid during the first 4h (mean elimination half-life: 4.2h).

Administration, Oral↗

PubMed2001

Conventional inner diameter short capillary columns: an approach to speeding up gas chromatographic analysis of medium complexity samples.

Short capillary columns (5 m) with 0.25 mm inner diameter (I.D.) are applied to the GC analysis of medium complexity samples (up to 30 components) with the aim of shortening analysis time. This approach is complementary to fast GC with narrow-bore columns and is based on compensating the lower efficiency of short columns with conventional I.D.'s (0.25-0.32 mm) by using a stationary phase selectivity suitable to separate the components of the sample under investigation, so that the required resolution power is achieved but, at the same time, the analysis time is shortened. The qualitative and quantitative effectiveness of this approach is demonstrated through the analysis of: essential oils with different compositions (chamomile and rosemary), low-volatility triterpenes in a plant extract (Maytenus aquifolium and M. ilicfolium), thermolabile pyrethrins in a Pyrethrum extract, and a mixture of pesticides applied to protect medicinal plant crops. In all examples, GC analysis was five to ten times faster than with conventional columns.

Chromatography, Gas↗

PubMed1999

Chronic sequelae and irreversible injuries following acute pyrethroid intoxication.

For patients the author has observed, the majority of complaints following an acute pyrethroid intoxication disappeared after the end of exposure. Residuals frequently observed after more than 2 years were: (1) cerebro-organic disorders (reduced intellectual performance with 20-30% reduction of endurance during mental work, personality disorder), visual disturbances, dysacousia, tinnitus; (2) sensomotor-polyneuropathy most frequently in the lower legs; (3) vegetative nervous disorders (paroxysmal tachycardia, pollakisuria, increased heat-sensitivity, orthostatic hypotonia and reduced exercise tolerance due to circulatory disorder). Non-neurological symptoms include deficiency of cellular and humoral immune system established by laboratory findings: opportunistic infections, especially Candida-infections of the gastro-intestinal tract, relapsing infections of the urinary and respiratory tract, the latter often aggravating to respiratory obstruction. Most of the patients exhibit positive epi- or intracutantest against pyrethroids or pyrethrines, and acquainted sensitivity also to other antigens. Many of these patients exhibit pathological autoimmune diagnostical findings and developed autoimmune diseases as for instance scleroderma-like syndrome, myasthenia-like syndrome with progredient muscle atrophy, autoimmun-hemolysis and autoimmun-thrombocytopenic purpura.

Acute Disease↗

PubMed2006

Aquatic effects of aerial spraying for mosquito control over an urban area.

In an effort to combat West Nile Virus, planes dispersed insecticide over Sacramento, CA, treating nearly 50,000 hectares with pyrethrins and the synergist piperonyl butoxide (PBO). Widespread dispersal of insecticide over a metropolitan area, coupled with extensive pretreatment data on the area's urban creeks, provided a unique opportunity to study effects of mosquito control agents on aquatic habitats within an urban setting. There was no evidence of aquatic toxicity from the two active ingredients in the product applied. However, PBO concentrations were high enough to enhance toxicity of pyrethroids already existing in creek sediments from general urban pesticide use. PBO concentrations of 2-4 microg/L were high enough to nearly double the toxicity of sediments to the amphipod Hyalella azteca. Though the increase in toxicity was modest, it was unexpected to find environmental synergy at all. Risk assessments for mosquito control agents have focused on the active ingredients but have failed to recognize the potential for interactions with pesticides previously existing in the environment, which in this case appeared to represent a risk to aquatic life greater than that of the active ingredients themselves.

Amphipoda↗

PubMed2005

Fast and versatile multiresidue method for the analysis of botanical insecticides on fruits and vegetables by HPLC/DAD/MS.

A simple multiresidue method for screening analysis of 12 botanical insecticides used by organic farmers has been developed. The method involves a rapid and small-scale extraction procedure with acetonitrile. For all fruit and vegetable samples, there was no need for clean up. Rotenone, azadirachtin, ryanodines, and pyrethrins can be separated by high-performance liquid chromatography, quantified, and confirmed with a diode array detector (DAD) and atmospheric pressure chemical ionization mass spectrometry (APCI-MS) in the select ion-monitoring mode (SIM). The majority of pesticide recoveries for various fruits and vegetables were >70% in the concentration range from 0.01 to 5 mg/kg. The limit of quantitation for most of the pesticides was 0.01 mg/kg, with the majority of relative standard deviations (RSD) mostly below 10%.

Chromatography, High Pressure Liquid↗

PubMed1983

Neurotransmitter receptors as targets for pesticides.

Nicotinic and muscarinic acetylcholine (ACh) receptors have been identified biochemically by means of their specific binding of [3H] alpha-bungarotoxin ([3H]alpha-BGT) and [3H]quinuclidinyl benzilate, respectively. There are some differences in the drug specificities, and sensitivities to active group reagents, of these receptors in insects when compared to those in vertebrates. Also, insect brain contains more nicotinic than muscarinic receptors, while the reverse is found in mammalian brain. Insect brain contains a third kind of putative ACh-receptor that is relatively soluble and is both nicotinic and muscarinic in its pharmacology but does not bind alpha-BGT. Toxic nicotine and analogs bind to it with high affinities. Several organophosphorus and carbamate insecticides and nereistoxin bind with high affinities to the nicotinic ACh-receptor of the electric organ of Torpedo. A few chlorinated hydrocarbon insecticides and derivatives interact with Torpedo nicotinic ACh-receptors, not at their 'receptor' sites but at their allosteric or 'channel' sites (which are identified by their specific binding of [3H]perhydrohistrionicotoxin). A few also bind to mammalian brain muscarinic receptors. The most potent on both receptors is the acaricide chlorobenzilate. Pyrethrins and synthetic pyrethroids also bind with high affinities to the channel sites of the Torpedo nicotinic ACh-receptor, though not to its receptor sites. Another group that binds to ACh-receptors is the organic and inorganic mercury compounds, which interact with both the Torpedo nicotinic and rat brain muscarinic receptors. Thus, neurotransmitter receptors act as molecular targets, primary or secondary for different pesticides.

Acetylcholinesterase↗