Flea Eggs Research Articles

Age at weaning, immunocompetence and ectoparasite performance in a precocial desert rodent.

We studied the effects of early weaning on immunocompetence and parasite resistance in a precocial rodent Acomys cahirinus. We hypothesized that if parasite resistance is energetically expensive and nutritional and immunological support from mothers are necessary for the long-term health of offspring, then early weaned animals would be immunologically weaker and less able to defend themselves against parasites than later weaned animals. We weaned pups at 14, 21 or 28 days after birth and assessed their immunocompetence and resistance against fleas Parapulex chephrenis when they attained adulthood. Immunocompetence was assessed using leukocyte concentration (LC) and a phytohaemagglutinin injection assay (PHA test). To estimate resistance against fleas, we measured performance of fleas via the number of produced eggs and duration of development and resistance to starvation of the flea offspring. We found a significant positive effect of weaning age on the PHA response but not on LC. The effect of age at weaning on flea egg production was manifested in male but not female hosts, with egg production being higher if a host was weaned at 14 than at 28 days. Weaning age of the host did not affect either duration of development or resistance to starvation of fleas produced by mothers fed on these hosts. We conclude that even in relatively precocial mammals, weaning age is an important indicator of future immunological responses and the ability of an animal to resist parasite infestations. Hosts weaned at an earlier age make easier, less-resistant targets for parasite infestations than hosts weaned later in life.

0.4% Dimeticone spray, a novel physically acting household treatment for control of cat fleas

The cat flea, Ctenocephalides felis, is the most important ectoparasite of cats and dogs worldwide as a cause of irritation and health problems. Most products to control these pests in the household environment rely upon a combination of neurotoxic insecticides and insect growth regulators to inhibit development of flea eggs and larvae into adults. However, some of these are affected by problems of insecticide resistance as well as public concerns about their potential for toxicity in domestic use. Heavy synthetic oils, like the siloxane dimeticone, are currently widely used to treat human ectoparasite infestations, acting by a physical mode of action, and have been used in a variety of presentations for killing all life stages of fleas. We have investigated the activity of low concentrations of high molecular weight dimeticone in a volatile silicone base for ability to immobilise flea life stages without asphyxiating them. We found that cat flea adults and larvae were immobilised by a surface film of dimeticone that inhibited movement of cuticular joints, apparently forming an effective sticky trap. When cocoons were treated the fleas continued to develop within the pupae but failed to emerge. An aerosol spray incorporating 0.4% concentration of dimeticone, for use as a residual household treatment, showed no significant difference in knock down capability compared with that of a widely used pyriproxifen/permethrin spray in a repeat challenge test, with effects persisting to inhibit adult flea emergence in the test arena area for more than 3 weeks after application.

Efficacy of indoxacarb applied to cats against the adult cat flea, Ctenocephalides felis, flea eggs and adult flea emergence

BackgroundA study was conducted to evaluate the effect of indoxacarb applied to cats on adult cat fleas, Ctenocephalides felis, flea egg production and adult flea emergence.MethodsSixteen cats were selected for the study and allocated to two treatment groups. Eight cats were treated with a 19.5% w/v topical spot-on solution of indoxacarb on day 0 and eight cats served as untreated controls. Each cat was infested with 50 fleas on Days -2, 7, 14, 21, 28, 35 and 42. On Days 1, 2, and 3, and at 2 and 3 days after each post treatment reinfestation flea eggs were collected from the pan under each cat cage. Eggs were counted and viability assessed by evaluating adult flea emergence 28 days after egg collection. Three days after treatment or infestation, each cat was combed to remove and count live fleas.ResultsTreatment with indoxacarb provided 100% efficacy following infestations on day -2, 7, 14, 21 and 28 and efficacy was 99.6% following infestations on days 35 and 42. Egg production from indoxacarb treated cats was reduced by 99.9% within 72 hours of treatment. For subsequent infestations no eggs were produced from treated cats from day 8 through day 30. Egg production was still reduced by ≥95.8% through day 45. Indoxacarb treatment also reduced adult flea emergence from eggs for 5 weeks after treatment. The combination of reduction in egg numbers and egg viability from indoxacarb treated cats reduced predicted flea emergence by 100% from days 2 – 31 and 99.9%, 100%, 96.4% and 99.0% on days 37, 38, 44 and 45, respectively.ConclusionsA topical spot-on formulation of indoxacarb provided ≥99.6% efficacy against flea infestations on cats for 6 weeks following a single treatment. Indoxacarb also eliminated or markedly reduced egg production for the entire evaluation period and reduced the viability of the few eggs that were produced from Day 1 through Day 38. Given indoxacarb’s effect on adult fleas, egg production and egg viability; this formulation can interrupt flea reproduction on treated cats for at least 6 weeks after treatment.

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

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 24hours 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 65–126mg/kg of permethrin; 8.9–17.4mg/kg of dinotefuran and 0.8–1.5mg/kg of pyriproxyfen. Each dog was infested with 100 adult cat fleas ready to lay eggs after 72hours spent feeding on cats. Dogs were infested 24hours after treatment and then weekly during 63 days. Eggs were collected and counted 24hours after each infestation and dogs were combed 48hours 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 48hours 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 an imidacloprid/flumethrin collar against fleas, ticks, mites and lice on dogs

BackgroundThe studies reported here were conducted to ascertain the efficacy of imidacloprid/flumethrin incorporated in a slow-release matrix collar, against infestations of dogs by fleas, ticks, mites and lice. Efficacy was evaluated against the flea Ctenocephalides felis felis, the ticks Rhipicephalus sanguineus, Ixodes ricinus, Ixodes scapularis, Dermacentor reticulatus and Dermacentor variabilis, the mite Sarcoptes scabiei and the biting louse Trichodectes canis.MethodsGroups of collar-treated dogs (n = 7–10) were infested with fleas and/or ticks at monthly intervals at least, over a period of up to 8 months. Efficacy against fleas was evaluated 24 to 48 h after treatment and 24 h after each re-infestation. Efficacy against ticks was evaluated at 48 h (acaricidal), 6 h (repellent) and 48 h (sustained) after infestation. The effect of regular shampooing or immersion in water on the efficacy of the collars was also tested. Efficacy against flea larvae was assessed by incubating blanket samples after dog contact with viable flea eggs. Effectiveness against lice and mites was evaluated after treatment of naturally infested animals. With the exception of the mites, efficacy was calculated by comparison with untreated negative control groups.ResultsEfficacy against fleas (24 h) generally exceeded 95%, and against flea larvae it exceeded 99% for 8 months. Sustained acaricidal (48 h) efficacy, covering a period of 8 months was 100% against I. ricinus, starting 2 days after treatment (in vivo), and 100% against I. scapularis (in vitro), above 97% against R. sanguineus, generally above 97% against D. reticulatus and above 90% for D. variabilis.Repellent (6 h) efficacy 2 days after treatment and continuing for 8 months was consistently 100% against I. ricinus, and above 90% against R. sanguineus.Regular shampooing affected efficacy against fleas and ticks to a lesser extent than regular immersion in water.The collars eliminated Trichodectes canis within 2 days and Sarcoptes scabiei within 3 months.ConclusionThe rapid insecticidal and acaricidal properties of the medicated collars against newly-acquired infestations of fleas and ticks and their sustained high levels of preventive efficacy have been clearly shown. Consequently they have the potential to prevent the transmission of vector-borne diseases and other conditions directly associated with infestation throughout an entire season of parasite abundance.

Efficacy of an imidacloprid/flumethrin collar against fleas and ticks on cats

BackgroundThe objectives of the studies listed here were to ascertain the therapeutic and sustained efficacy of 10% imidacloprid (w/w) and 4.5% flumethrin (w/w) incorporated in a slow-release matrix collar, against laboratory-infestations of fleas and ticks on cats. Efficacy was evaluated against the flea Ctenocephalides felis felis, and the ticks Ixodes ricinus, Amblyomma americanum and Rhipicephalus turanicus. The number of studies was so large that only a general overview can be presented in this abstract.MethodsPreventive efficacy was evaluated by infesting groups of cats (n = 8-10) with C. felis felis and/or I. ricinus, A. americanum or R. turanicus at monthly intervals at least, for a period of up to 8 months. Efficacy against fleas was evaluated 24 to 48 h after treatment and 24 h after infestation, and against ticks at 6 h (repellent) or 48 h (acaricidal) after infestation. Efficacy against flea larvae was evaluated over a period of 8 months by incubating viable flea eggs on blanket samples after cat contact. In all cases efficacy was calculated by comparison with untreated negative control groups.ResultsEfficacy against fleas (24 h) generally exceeded 95% until study termination. In vitro efficacy against flea larvae exceeded 92% until Day 90 and then declined to 67% at the conclusion of the study on Day 230.Sustained acaricidal (48 h) efficacy over a period of eight months was consistently 100% against I. ricinus from Day 2 after treatment, 100% against A. americanum, except for 98.5% and 97.7% at two time-points, and between 94% and 100% against R. turanicus.From Day 2 until 8 months after treatment the repellent (6 h), efficacy was consistently 100% against I. ricinus, and between 54.8% and 85.4% against R. turanicus.ConclusionThe rapid insecticidal and acaricidal properties of the medicated collars against newly- acquired infestations of fleas and ticks and their sustained high levels of preventive efficacy have been clearly demonstrated. Taking into account the seasonality of fleas and ticks, the collars have the potential to prevent the transmission of vector-borne diseases and other conditions directly associated with infestation throughout the season of parasite abundance.

Surface Ultrastructure of the Eggs of Malacopsylla grossiventris and Phthiropsylla agenoris (Siphonaptera: Malacopsyllidae)

The fleas of the Malacopsyllidae are known only by their adults. In this study, we describe the eggs of Malacopsylla grossiventris and Phthiropsylla agenoris and compare their surface ultrastructure using scanning electron microscopy. Eggs of both flea species are similar in their general appearance, i.e., the presence of disks and absence of lateral aeropyles, but they differ in size, texture of the surface, and number of micropyles and aeropyles. In addition, the eggs of M. grossiventris and P. agenoris are larger (719-800 µm) than most of the flea eggs known (<600 µm), and the length/width ratio is 2.0, while it varies between 1.6 and 1.8 in other species. As opposed to other large species, malacopsyllids have expandable (telescoping) abdomens that display growth. It is possible that a clutch of eggs has more than 2 eggs. Females of M. grossiventris were observed fixed with their mouthparts to the skin of their hosts. Indeed, some of these specimens were observed copulating on the venter of their hosts. These results contribute to the knowledge about the biology of malacopsyllids.

Dose confirmation and non-interference evaluations of the oral efficacy of a combination of milbemycin oxime and spinosad against the dose limiting parasites, adult cat flea (Ctenocephalides felis) and hookworm (Ancylostoma caninum), in dogs

Two separate controlled and blinded studies were conducted to confirm the dose and non-interference of spinosad and milbemycin oxime (MO) administered orally in combination or alone to dogs for the treatment and control of experimentally induced flea infestations (Ctenocephalides felis) and adult hookworm infections (Ancylostoma caninum). For each study, dogs were allocated randomly based on pre-treatment adult flea and hookworm egg counts to one of four treatment groups of 10 animals each. In each study, spinosad and MO in combination, using the lower half (30–45mg/kg spinosad; 0.5–0.75mg/kg MO) of the US commercial dose band (30–60mg/kg spinosad; 0.5–1.0mg/kg MO) of each active ingredient, or individually alone using the full dose range, were given orally to dogs on Day 0 using a tablet formulation. A placebo control was treated similarly. In one study, on Days −1, 5, 12, 19, 28 and 35 each dog was infested with approximately 100 unfed adult C. felis obtained from the investigator's established flea colony. All dogs were infested via the same method. Forty-eight hour post-infestation flea comb counts were conducted on Days 1, 7, 14, 21, 30 and 37 and were used to determine the knockdown and residual flea activity. In the second study, on Day −27 each of 48 dogs were experimentally inoculated with 100 third-stage infective larvae of the hookworm, A. caninum. Dogs were treated on Day 0 and necropsied on Day 7 or Day 8. All nematodes in the intestinal tract were collected on Day 7 or Day 8, identified and counted by species and stage. Post-treatment, the geometric mean live flea counts were significantly different (p-value<0.0001) between the spinosad/MO combination and the spinosad only treatment groups as compared to the vehicle control group. The flea counts in the MO only group and the control group were not statistically different. The spinosad and MO combination group and the spinosad only treatment group demonstrated significantly different knockdown (100%) and post-treatment residual flea efficacy at Day 30 was 100% for both groups as compared to the vehicle control. The presence of MO in combination with spinosad did not interfere with the flea efficacy of spinosad as compared to the spinosad only group. MO alone did not demonstrate any flea efficacy. Post-treatment, the geometric mean A. caninum worm counts were significantly different (p-value<0.0001) between the spinosad and MO combination group as compared to the vehicle control group. The worm counts in the MO only group and the combination group were not statistically different. The spinosad and MO combination group (99.8% reduction) and the MO only treatment group (99.5% reduction) both demonstrated significantly different hookworm efficacy as compared to the vehicle control group. The presence of spinosad in combination with MO did not interfere with the hookworm efficacy of MO as compared to the MO only group. Spinosad alone did not demonstrate any hookworm efficacy. In summary, flavored spinosad and MO combination tablets administered orally to dogs at the lower end (30–45mg/kg spinosad; 0.5–0.75mg/kg MO) of the US commercial tablet unit dose range (30–60mg/kg spinosad; 0.5–1.0mg/kg MO) were both safe and highly efficacious delivering 100% knockdown and 30 days of residual adult flea control on experimentally infested dogs as well as >99% adult hookworm efficacy evaluated under laboratory conditions. Interference between either drugs was not demonstrated for both of these dose limiting parasites.

Large-scale monitoring of imidacloprid susceptibility in the cat flea, Ctenocephalides felis

Although on-animal topical treatment with compounds such as imidacloprid has revolutionized the control of the cat flea, Ctenocephalides felis (Bouché) (Siphonaptera: Pulicidae), the development of insecticide resistance is a continuing threat. As part of a highly co-ordinated and unprecedented resistance monitoring programme for C. felis, 1437 flea isolates were collected by veterinary clinics in Australia, Germany, France, the U.K. and 29 states in the U.S.A. from 2002 to 2009. About 65% of the collections were made from June to October each year and 71% of the collections were from cats. Collections of flea eggs were sent to one of five different laboratories, where they were tested with a diagnostic dose of imidacloprid (3 p.p.m.) applied to larval flea-rearing medium. Of the 1437 collections received, 1064 contained adequate numbers of eggs for testing. Of these isolates, untreated eggs failed to hatch in 22.7% and were not considered valid bioassays. Survival rates >5% and development of adult fleas (a threshold for further testing) occurred in only 22 isolates. They were re-tested with the same diagnostic dose and none produced >5% adult emergence. Complete dose-response bioassays were performed on three of the isolates that had triggered a second test and produced slopes, intercepts and LC(50) values similar to those for existing susceptible laboratory strains. Results confirmed sustained susceptibility of C. felis to imidacloprid, despite its widespread use for over a decade.

Effects of orally administered spinosad (Comfortis ®) in dogs on adult and immature stages of the cat flea ( Ctenocephalides felis)

The efficacy of spinosad against adult fleas ( Ctenocephalides felis) on dogs was evaluated in three controlled, blinded studies. One study was conducted to determine speed of kill on experimentally infested dogs. Two additional studies were designed to assess the efficacy of spinosad in preventing environmental contamination with flea eggs (USA study and EU study). An additional objective of the USA study was to assess the effects of skin and hair-coat debris from spinosad-treated dogs on eggs and larvae of C. felis. Dogs were randomly allocated to treatment with beef-flavored spinosad tablets, administered orally at a minimum dosage of 30 mg/kg, or placebo. In the first study, speed of kill was determined by flea comb counts performed at 0.5, 1, 2, 4, 8, 12, 24 and 48 h after spinosad treatment. Reductions in geometric mean flea counts for spinosad-treated dogs, compared to placebo were 53.7% at 0.5 h, 64.2% at 1 h, 85.8% at 2 h and 100% at 4 through 48 h post-treatment ( p < 0.05 at 1 h and beyond). In the 2 flea egg production studies, dogs were treated (spinosad or placebo) once on day 0, infested with 600 fleas approximately 3 h post-treatment and reinfested with approximately 600 fleas at intervals over 1 month. Flea eggs were collected starting at approximately 72 h after each infestation. Eggs were examined for any effects of spinosad on egg viability. Efficacy of spinosad was also evaluated against environmental eggs and larvae exposed to canine hair-coat debris collected on days 3, 7, 14, 21, and 30. Spinosad was highly effective in reducing flea egg production (>99.8% across the entire study period) compared to control dogs in both egg collection studies. Insufficient numbers of eggs were recovered from spinosad-treated dogs to determine the viability of those eggs. There was no evidence of any effect on environmental flea stages, indicating that spinosad was not present in the skin debris of spinosad-treated dogs. The capability of spinosad to quickly kill adult fleas, and to greatly reduce egg production following challenge with high numbers of adult fleas is important in breaking the flea life cycle and preventing the introduction and establishment of new flea infestations in the household.

Seasonal Adjustments in Nest Cup Lining in Blue TitsCyanistes caeruleus

Nest building requires parental investment and we should expect to find trade-offs between building and other behaviours or demands. For example, species breeding in temperate zones face the seasonal shift from spring to summer and might alter their nest construction in relation to environmental conditions as the season progresses. We quantified seasonal variation in the length of the nest building period, nest mass, composition, Hen Flea Ceratophyllus gallinae abundance and egg production in nestbox breeding Blue Tits Cyanistes caeruleus. The nest building period decreased seasonally, possibly indicating individual adjustment of optimal time of reproduction. Despite this, there was no seasonal trend in overall nest mass, although nest composition did change. The mass of the nests' moss base and Hen Flea abundance showed no seasonal variation, but there was a seasonal decline in the mass of the cup lining material, suggesting that female Blue Tits selectively adjust the cup lining component of their nests to reflect increasing ambient temperatures in order to create an optimal microclimate for the developing embryos and nestlings.

Efficacy of a topically applied formulation of metaflumizone on cats against the adult cat flea, flea egg production and hatch, and adult flea emergence

A spot-on metaflumizone formulation was evaluated to determine its adulticidal efficacy, effect upon egg production, and ovicidal activity when applied to flea infested cats. Eight male and eight female adult domestic shorthair cats were randomly assigned to either serve as non-treated controls or were treated topically with a minimum of 40 mg/kg metaflumizone in single spot-on Day 0. On Days −2, 7, 14, 21, 28, 35, 42, 49, and 56, each cat was infested with approximately 100 unfed cat fleas, Ctenocephalides felis felis. On Days 1, 2, and 3, and at 48 and 72 h after each post-treatment reinfestation, flea eggs were collected and counted. At approximately 72 h after treatment or infestation, each cat was combed to remove and count live fleas. Egg viability was determined by examining hatched eggs after 5 days and adult emergence was determined 28 days after egg collection. Metaflumizone provided ≥99.6% efficacy against adult fleas from Days 3 to 45 following a single application. Following treatment, egg production fell by 51.6% within 24 h and 99.2% within 48 h. Following subsequent weekly infestations egg production from treated cats was negligible out to Day 38, with ≥99.5% reduction relative to non-treated cats. Where there were eggs to evaluate, metaflumizone treatment did not have any apparent effect on the hatching of eggs or on the development and emergence of adult fleas from the eggs produced by fleas from treated animals.

Immunocompetence and flea parasitism of a desert rodent

Summary Immunocompetence is the general capacity of an organism to mount an immune response against pathogens and parasites. We studied the relationship between the immunocompetence of a rodent host, Meriones crassus (Sundevall's Jird) and parasitism by the flea Xenopsylla ramesis. We hypothesized that flea parasitism affects physiological and immunological variables of the host, and that the host's level of immunocompetence affects fitness components in the flea parasite. We wanted to find out (a) the effect of flea parasitism on the haematocrit (Hct), leucocyte concentration (LC) and response to phytohaemagglutinin (PHA) of the host; (b) if and how the level of immunocompetence of the host is related to the fitness of fleas exploiting it; and (c) the relationship between the immunological and behavioural defences of the host. We measured Hct and LC and response to PHA before and after 16 days of flea infestation in Sundevall's Jird and compared these variables between jirds subjected to flea parasitism and non‐parasitized (control) animals. We evaluated egg production and hatching success in fleas exploiting hosts with different levels of immunocompetence. The effect of flea parasitism on Hct and LC of rodents was manifested by an increase in among‐host variation in the temporal changes of these variables. Response to PHA injection was significantly lower in parasitized than in control animals. Flea egg production and hatching success were not related to either LC, prior to experimental treatments, or to the PHA response of rodents. However, both of these flea fitness traits were negatively correlated with changes in LC between the 1st and the 16th days of infestation. At the end of the experiment, blood consumption of fleas was measured in jirds of both treatment groups. Fleas consumed significantly more blood when they fed on previously parasitized than on non‐parasitized animals. Among fleas that fed on previously parasitized animals, blood consumption was positively correlated with the initial LC of the hosts, and negatively correlated with differences in LC between the 1st and the 16th days of flea infestation. We found no correlation between blood consumption in fleas that fed on control animals and either immunological variable of the hosts. No trade‐off was found between behavioural and immune defences of the rodent hosts.

Field trial of the efficacy of a combination of imidacloprid and permethrin against Tunga penetrans (sand flea, jigger flea) in dogs in Brazil

In a field trial in Brazil 17 dogs penetrated by females of the jigger flea, Tunga penetrans, were topically treated with a combination of 10% imidacloprid and 50% permethrin (Advantix), while 17 dogs remained untreated. The follow-up controls on days 7, 14, 21 and 28 post-treatment clearly showed that, beginning from day 7, the flea load in treated dogs decreased, so that most of the dogs became free of tungiasis lesions, while in the untreated group the flea load remained high. Since the dogs distribute the flea eggs throughout the village, leading to a high incidence of tungiasis in humans, treatment of dogs probably also decreases the number of cases of tungiasis in the latter.

Human Exposure to Selamectin from Dogs Treated with Revolution™: Methodological Consideration for Selamectin Isolation

This study was undertaken to determine selamectin residue in dog's blood and in gloves worn while petting dogs after Revolution™ application. Revolution™ contains the active ingredient selamectin (a semisynthetic avermectin), which controls endoparasites and ectoparasites, including adult fleas, flea eggs, ticks, heartworms, ear mites, and sarcoptic mange in dogs, for 30 days. Revolution™ was applied topically on a group of six adult house hold dogs (240 mg selamectin/dog). The gloves worn for 5 min while petting the dogs were collected in glass jars and the blood samples (5 mL/dog) were collected in EDTA tubes at 0 h, 24 h, and 72 h, and at 1, 2, 3, 4, and 5 weeks post-Revolution™ application for selamectin residue determination. At no time during the study did the dogs show any signs of toxicity, weight loss, or change in body temperature. Extracts of the blood and the gloves were analyzed for selamectin residue using RP-HPLC coupled with a UV detector (246 nm). Selamectin standard used for peak identification and quantitation was purified from Revolution™. Selamectin residue was detected in the blood (10.26 ± 1.06 ng/mL) only at 72 h post-Revolution™ application, probably due to its poor dermal absorption and rapid elimination from the circulation. In the glove extracts, the highest concentration of selamectin (518.90 ± 66.80 ppm) was detected 24 h after Revolution™ application. Transferable residue of selamectin in gloves from dog's coat was detected at a lesser magnitude after 1 week of Revolution™ application, and that was followed by a further descending trend during the second, third, and fourth weeks. No selamectin residue was detected in the glove extracts after the fifth week. In spite of selamectin's binding to the sebaceous glands of the skin, gloves contained significant transferable residue. Thus, these findings suggest that repeated exposure to selamectin can pose potential health risks, especially to veterinarians, veterinary technologists, dog trainers/handlers, and pet owners.

Efficacy of fipronil/( S)-methoprene combination spot-on for dogs against shed eggs, emerging and existing adult cat fleas ( Ctenocephalides felis, Bouché)

The inhibitory activities of fipronil (10% (w/v) solution), ( S)-methoprene (9% (w/v) solution), and fipronil/( S)-methoprene (10 and 9% (w/v) solution, respectively) combination against eggs and emerging adult cat fleas ( Ctenocephalides felis) and adulticidal activity were tested on experimentally infested dogs. Thirty-two Beagle dogs were selected for this study and eight replicates of four animals were formed based on body weight within sex. One dog in each replicate was randomly allocated to treatment with: (1) untreated control; (2) fipronil 10% (w/v) solution, (3) ( S)-methoprene 9% (w/v) solution, and (4) fipronil 10% (w/v) and ( S)-methoprene 9% (w/v) combination solution. Treatments were applied once topically on Day 0 at the rate of 0.067 ml/kg. On Days −12, −1, 21, and weekly to Day 84 each dog was infested with ∼200 fleas and comb counted ∼24 h later, or 2 days (our 48 h) after in the case of Day −1 infestation. On Days −11, 1, 22, and weekly to Day 85 each dog was again infested with ∼200 fleas. Flea eggs were collected over ∼24 h beginning 3 days after infestation. Fleas were combed off of the dogs and counted at the end of the egg collection period (∼96 h count). One aliquot of up to about 100 eggs, if available, from each animal at each infestation time was incubated for ∼72 h to determine larval hatch and the other for 35 days to determine the number of adults that developed. The 10% (w/v) fipronil spot-on provided excellent control (>95%) of adult fleas on dogs for 5 weeks. Similarly, the combination spot-on of 10% (w/v) fipronil and 9% (w/v) ( S)-methoprene provided excellent control of adult fleas, i.e., >95% for 5 weeks. From week 6 post-treatment onward, the relatively low inhibition of adult flea emergence substantiated the lack of significant ovicidal/larvicidal activity in the fipronil (10%, w/v) treatment group. However, the combination product provided excellent (>90%) ovicidal activity for 8 weeks and high (91.4%) inhibition of adult flea emergence for 12 weeks. In addition, a synergistic effect of the two compounds in combination was demonstrated with fipronil enhancing the ovicidal and inhibition of adult flea emergence activity of ( S)-methoprene against cat flea eggs. When all stages of the life cycle of the cat flea are considered, the combination spot-on product provided a high level of total flea control yielding a curative effect against adult fleas and inhibition of flea development stages with little to no potential reinfestation pressure on the animal or in the environment for 12 weeks.

High infection rate of Wolbachia endobacteria in the sand flea Tunga penetrans from Brazil

Tunga penetrans is an ectoparasite causing considerable morbidity in endemic communities. Recently, endobacteria of the genus Wolbachia were identified also in T. penetrans. Since Wolbachia were suggested as targets for intervention of insect pests and human filariasis, sand fleas were collected from infested humans, dogs and rats in a hyperendemic area in northeastern Brazil, and screened for Wolbachia infections. Twenty-one adult fleas and four batches of flea eggs were examined by PCR using primers targeting the 16S rDNA, the DNA coding for FtsZ cell-cycle protein or a Wolbachia surface protein (WSP-1). Wolbachia were detected in all examined samples from eggs, free-living male and female fleas and from neosomic female fleas. No Wolbachia DNA was detected in two samples containing flea faeces. In addition, Wolbachia were labelled by immunohistology in the ovaries of 37 female fleas using antisera raised against WSP-1 of Wolbachia the filarial parasite Dirofilaria immitis. In the vicinity of the embedded fleas containing the Wolbachia, infiltrations of neutrophils and macrophages were observed. This study showed that Wolbachia endobacteria are abundant in T. penetrans and that all examined fleas were infected by these endobacteria. Our findings may have important implications for the future development of control strategies for human tungiasis.

Efficacy and longevity of nitenpyram against adult cat fleas (Siphonaptera: Pulicidae).

Nitenpyram (Capstar) is a fast acting, orally administered flea treatment that is absorbed into the blood of the host animal and is readily available for uptake by feeding fleas. We examined the efficacy of a single dose of nitenpyram against adult cat fleas, Ctenocephalides felis (Bouché), over several days. We recorded adult flea mortality and flea egg production on treated and untreated cats. Nitenpyram provided 100% kill of all fleas on the host at the time of treatment and for up to 24 h after treatment. Between 24 and 48 h after treatment, there was a 98.6% reduction in adult flea numbers. From 48 to 72 h, there was a 5% reduction in adult fleas. There was a 97% reduction and 95.2% reduction in the number of flea eggs collected from treated versus untreated animals during the first 48 h and from 48 to 72 h, respectively. In addition, we quantified three distinct behavioral responses of infested adult cats treated with nitenpyram to determine the extent of any immediate, overt behavioral responses in treated animals. A significant increase in scratching, biting, licking, and twitching occurred for 5 h. The biting and licking continued for 7 h after treatment. Administration of nitenpyram provides an effective mechanism to eliminate adult fleas from hosts for up to 48 h after treatment.

Consumption of flea faeces and eggs by larvae of the cat flea, Ctenocephalides felis.

The effects of the consumption of flea faeces and non-viable eggs on larval development in the cat flea Ctenocephalides felis (Bouché) (Siphonaptera: Pulicidae) were investigated. Only 13.3% of larvae developed into adults when fed a diet of male or female flea faeces alone; however, 90% of larvae developed into adults when fed on flea faeces supplemented with non-viable flea eggs. When fed with non-viable eggs alone, larvae did not develop into adults. Nevertheless, non-viable eggs may provide critical supplemental nutrients, lacking in flea faeces and required for larval development. None of the larvae fed on flea faeces or non-viable eggs alone formed a cocoon. A diet of flea faeces alone significantly extended the second as well as third larval stadia compared to larvae fed on diets containing non-viable eggs. It is suggested that the cannibalism of fertile eggs may limit population growth in the cat flea.

Development of a larval bioassay for susceptibility of cat fleas (Siphonaptera: Pulicidae) to imidacloprid.

Strategies for controlling cat fleas, Ctenocephalidesfelisfelis (Bouché), have undergone dramatic changes in the past 5 yr. With the advent of on-animal treatments with residual activity the potential for the development of insecticide resistance increases. A larval bioassay was developed to determine the baseline susceptibility of field-collected strains of cat fleas to imidacloprid. All four laboratory strains tested showed a similar level of susceptibility to imidacloprid. Advantages of this bioassay are that smaller numbers of fleas are required because flea eggs are collected for the test. Insect growth regulators and other novel insecticides can also be evaluated. Using a discriminating dose, the detection of reduced susceptibility in field strains can be determined with as few as 40 eggs.