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PubMed1996

A novel approach to flea control on cats, using pyriproxyfen.

Pyriproxyfen is a new insect growth regulator with potent activity against developing stages of the cat flea, Ctenocephalides felis. To determine its duration of action after application as a spot-on topical treatment, 20 cats were allocated to two groups. One group acted as untreated controls, and each cat in the other was given a single dose of 1 mg/kg pyriproxyfen. Each cat was infected with fleas at weekly intervals and caged. Eggs were collected and their viability determined as a measure of the effect of the agent on adult fleas. The effect of the transfer of pyriproxyfen from each cat to its immediate surroundings was monitored by observing the development of fertile flea eggs placed on samples of blanket taken from each cage. Results from untreated control cats showed that the experimental conditions were favourable for the lifecycle of the flea. Flea reproduction on treated cats was inhibited completely for seven weeks and substantially for at least a further two weeks. Blankets used by cats treated up to two weeks previously prevented flea development entirely and substantial control was still achieved up to four weeks after treatment.

Animals↗
PubMed1997

The fleas (Siphonaptera) of Tennessee.

Thirty-three species of fleas are recorded from the state of Tennessee. New state records are reported for two species, the pulicid fleas Euhoplopsyllus glacialis affinis and Pulex simulans. Two species of fleas with catholic feeding habits appear to be especially widespread and abundant in Tennessee. These are the pulicid Ctenocephalides felis which parasitizes cats, dogs, humans, opossums, and other medium to large sized mammals, and the hystrichopsyllid Ctenophthalmus pseudagyrtes which is associated with several species of small mammals, particularly shrews, moles, voles, and native mice. For a southeastern state, Tennessee has a relatively rich flea fauna. The figure of 33 flea species recorded here for Tennessee is higher than documented figures for other southeastern states (17 species for Alabama, 19 for Florida, 20 for Georgia, 12 for Mississippi, 18 for North Carolina, 19 for South Carolina). This is largely because several species with boreal origins inhabit the higher elevations characteristic of the Appalachian Mountains in the eastern part of the state. Although plague is not enzootic as far east as Tennessee, and murine typhus is rare of absent, suitable flea vectors inhabit the state and one abundant flea species, C. felis, is a pest because it feeds on companion animals and humans.

Animals↗
PubMed1997

Ranging of male Oropsylla montana fleas via male California ground squirrel (Spermophilus beecheyi) juveniles.

We asked if fleas more frequently remain on those California ground squirrels (Spermophilus beecheyi) that are likely to emigrate from their natal nest. In Camp Ohlone, Alameda County, California, juvenile male squirrels were infested with more fleas (Oropsylla montana) than were juvenile females, and juveniles of both sexes were infested with more fleas (O. montana and Hoplopsyllus anomalus) than adults. There was no difference between the adult sexes in the number of fleas. The disproportionate infestation of male juveniles was accounted for almost exclusively by male O. montana. Greater activity on the part of juvenile males did not account for this difference; the activity of male and female juveniles was very similar. As yearlings, male squirrels established home ranges at greater distances from the natal burrow than did females. Remaining on ranging male squirrels might help male fleas find nonsibling mates in new nests, whereas female fleas might tend to stay in the natal nest in order to assure their progeny of its resources. Flea behavior, modified by characteristics of the host that are sex-specific and predictive of future traits, such as the tendency to range, may thus determine the nature and extent of infestations in juvenile squirrels.

Age Factors↗
PubMed1989

Experimental transmission of murine typhus by Xenopsylla cheopis flea bites.

Transmission of Rickettsia typhi to rats by the bites of Xenopsylla cheopis (Rothschild) fleas was investigated. Procedures rigorously excluded the possibility of contamination of the host skin by flea faeces. Fleas with R. typhi infection (21-25 days post-infection) which fed through bolting cloth (45 min exposure to ten fleas) transmitted rickettsiae with a success rate of 20%. Infective fleas allowed free access to their host for 8 h (10-15 fleas/rat) gave transmission rates of 45-68%. They were also capable of inoculating R. typhi through a membrane of rat skin on a feeder. Only fleas which had been infected for 21 days or longer transmitted R. typhi orally. Oral transmission appeared to be the result of regurgitation of rickettsiae present in the foregut lumen rather than through salivary secretions.

Animals↗
PubMedDate not supplied

Flea-borne rickettsioses: ecologic considerations.

Ecologic and economic factors, as well as changes in human behavior, have resulted in the emergence of new and the reemergence of existing but forgotten infectious diseases during the past 20 years. Flea-borne disease organisms (e.g., Yersinia pestis, Rickettsia typhi, R. felis, and Bartonella henselae) are widely distributed throughout the world in endemic-disease foci, where components of the enzootic cycle are present. However, flea-borne diseases could reemerge in epidemic form because of changes in vector-host ecology due to environmental and human behavior modification. The changing ecology of murine typhus in southern California and Texas over the past 30 years is a good example of urban and suburban expansion affecting infectious disease outbreaks. In these areas, the classic rat-flea-rat cycle of R. typhi has been replaced by a peridomestic animal cycle involving, e.g., free-ranging cats, dogs, and opossums and their fleas. In addition to the vector-host components of the murine typhus cycle, we have uncovered a second typhuslike rickettsia, R. felis. This agent was identified from the blood of a hospitalized febrile patient and from opossums and their fleas. We reviewed the ecology of R. typhi and R. felis and present recent data relevant to the vector biology, immunology, and molecular characterization and phylogeny of flea-borne rickettsioses.

Animals↗
PubMed1987

Suppression of Rickettsia typhi transmission in fleas maintained on murine typhus-immune rats.

The presence of host antibodies against Rickettsia typhi in the hemolymph of Xenopsylla cheopis fed on immune rats was studied using an indirect immunofluorescent antibody (IFA) test and enzyme-linked immunosorbent assay (ELISA). The time course experiment revealed that antibody to R. typhi appears in the flea hemolymph after 18 hr exposure to host and persists for 24 hr. IFA tests utilizing specific antisera to rat IgG (Fc) and rat IgG (Fab) fragments, indicate that some unaltered rat IgG to R. typhi were present in the hemolymph of immune fed fleas. Host antibody to R. typhi was detected on the surface of the rickettsiae in the flea hemolymph and gut contents by IFA. Maintenance of infected fleas on immune host had no significant effect on the establishment and subsequent growth of rickettsiae within the fleas. However, 19-22 day infected fleas maintained on immune hosts failed to transmit R. typhi to baby rats.

Animals↗
PubMed1987

Effects on the development of Dipylidium caninum and on the host reaction to this parasite in the adult flea (Ctenocephalides felis felis).

Temperature was found to be a major factor affecting the development of Dipylidium caninum and the presence of a host reaction of adult Ctenocephalides felis felis to D. caninum. Adult fleas reared at 30-32 degrees C contained fully developed metacestodes when they emerged from their cocoons. However at lower temperatures, D. caninum could not complete development until the flea hosts had spent some time on their mammalian hosts. It was the surface temperature of the mammals (31-36 degrees C) and not the fleas' blood meals which resulted in the metacestodes completing their development. This development of D. caninum was therefore independent of the flea development. At 20 degrees C, a larger and more prolonged host reaction was mounted than at higher temperatures. The larval flea diet had a small effect on the subsequent cestode development and the adult fleas' reaction to it.

Animals↗
PubMed1982

[Histological studies of the gamogony and sporogony of Hepatozoon erhardovae in experimentally infected rat fleas (Xenopsylla cheopis)].

We studied, under experimental conditions, the life cycle of Hepatozoon erhardovae in the tropical rat flea, Xenopsylla cheopis, light microscopically on coloured semi-thin sections. Fleas killed and prepared on the day of infection show stomachs filled with mice erythrocytes. Some monocytes are parasitized or show empty envelopes of gametocytes. The latter perforate the wall of the stomach, leaving behind empty parasitophorous vacuoles, and they migrate to the fat-body cells of the flea where they differentiate sexually and where they stay during the whole of their further sexual development. On days 2 and 3 post infection (p.i.) microgametes were observed with one flagellum each, as well as macrogametes in one and the same host cell. Fertilization is induced by gametogamy. During the various divisions of the nuclei on the days 8-12 p.i. droplet-like evaginations are formed on the pellicle of the oocyst from the peripherical chromatin condensations. Between days 12 and 14 p.i. the sporoblasts develop while the oocysts diminish in size. Between days 18 and 20 p.i. 16 sporozoites and a large residual body are differentiated in each sporoblast and surrounded by the sporocyst wall. The oocyst wall is preserved and forms sporocyst balls that are set free when the flea abdomen is pressed. The flea thus presents a highly infective vector; the intermediate host is infected after eating the flea.

Animals↗
PubMed2003

Host specificity and foraging efficiency in blood-sucking parasite: feeding patterns of the flea Parapulex chephrenis on two species of desert rodents.

Parasite species can adapt to ecological, behavioral, physiological and biochemical traits of a particular host species. The flea Parapulex chephrenis occurs on the spiny mouse Acomys cahirinus, but does not occur on a co-existing gerbil, Gerbillus dasyurus. To test the hypothesis that the host species affects feeding parameters of a host-specific flea, we studied the feeding rate, rate of blood digestion and resistance to starvation of P. chephrenis when feeding on A. cahirinus and G. dasyurus. We predicted that P. chephrenis would: (1) fill its gut with blood faster, (2) digest blood for a shorter time, and (3) survive longer when starved while feeding on its specific host, A. cahirinus, than on a non-specific host, G. dasyurus. These three responses were observed when P. chephrenis fed on the different hosts and, consequently, our predictions were supported. Twenty percent of fleas filled their midgut after feeding for 10 min on A. cahirinus but this occurred only after 25 min on G. dasyurus. The middle stage of blood digestion was significantly shorter in all fleas feeding on A. cahirinus than in fleas feeding on G. dasyurus. Flea survival was shorter when feeding on G. dasyurus than when feeding on A. cahirinus at 25 degrees C, but no difference in survival time was found at 15 or 20 degrees C. Both A. cahirinus, the specific host, and G. dasyurus, the non-specific host, co-exist in rocky habitats, yet P. chephrenis occurs on one rodent and not the other. The absence of P. chephrenis on G. dasyurus in nature and the decreased foraging efficiency when feeding on this species in the laboratory suggests that some physiological and biochemical differences between hosts can lead to sharp ecological differences in host-parasite relationships.

Animals↗
PubMed1995

Flea species from dogs and cats in northern Greece: environmental and clinical implications.

Fleas were identified after being collected from 129 dogs and 38 cats of random breed, sex and age. All these animals, infested with fleas and admitted to the Clinic of Medicine of the Veterinary Faculty in Thessaloniki for routine procedures, were from different habitats and originated from various parts of northern Greece. Ctenocephalides canis was the most common species found on the dogs (71.3%). Conversely, its prevalence in the 14 cats was substantially lower (5.3%). Ctenocephalides felis was found on 97.4% of the cats and 40.3% of the dogs surveyed. Of the other flea species, with much lower prevalence, Pulex irritans (0.8%) and Xenopsylla cheopis (0.8%) were observed only on the dogs. Seventeen dogs (13.2%) and one cat (2.6%) had mixed infestations. Flea-associated dermatoses were observed in 26 dogs (20.2%) and four cats (10.5%). Flea-allergic dermatitis, with its typical manifestations, was seen in ten of the dogs (38.5%) with skin lesions. Three out of four flea-allergic cats presented miliary dermatitis and one symmetrical hypotrichosis.

Animals↗
PubMed2005

Molecular characterisation of nicotinic acetylcholine receptor subunits from the cat flea, Ctenocephalides felis (Siphonaptera: Pulicidae).

As part of a program to monitor the susceptibility of cat flea populations to the insecticide imidacloprid we have examined the cat flea nicotinic acetylcholine receptor, the target site protein of the neonicotinoid group of insecticides. Seven nAChR subunits (six alpha-type and one beta-type) were identified in cat flea using a degenerate PCR-based strategy. Five of these were expressed in vitro by creating chimeras containing the N-terminal ligand-binding domain of the cat flea subunits and the C-terminal region of the Drosophila Dalpha2 (SAD) subunit. Two of the five chimeric subunits, Cfalpha1/Dalpha2 and Cfalpha3/Dalpha2, when co-expressed with rat beta2 in Drosophila S2 cells, showed high-affinity binding of both epibatidine (Kd=1.6+/-0.6 and 0.13+/-0.06nM, respectively), and imidacloprid (Ki=142+/-34 and 28.7+/-2.4nM, respectively). It is likely therefore that Cfalpha1 and Cfalpha3 contribute to nAChR populations in vivo that are sensitive to imidacloprid. The identification of cat flea nAChR subunits that have a high affinity for imidacloprid presents candidate genes in which to look for resistance-associated mutations if target-site resistance to imidacloprid arises in domestic pet flea populations.

Amino Acid Sequence↗
PubMed2006

A rodent model for allergic dermatitis induced by flea antigens.

There have been very few reports of experimentally induced animal models of allergic dermatitis, an immunologic disorder. This report describes the induction of histopathology confirmed allergic dermatitis in C57BL/6 mice along with the consistent clinical sign of alopecia following the administration of flea antigens emulsified in complete Freund's adjuvant (CFA). By comparing different strains of mice, routes of injection, types of adjuvants and different dosages of flea antigens, C57BL/6 mice were found to be most susceptible to flea antigens administered intramuscularly (i.m.) and subsequently developed dermatologic excoriations and local alopecia. The level of specific IgE reactive to flea antigens in C57BL/6 mice after the onset of clinical signs was significantly higher than such levels in mice without clinical signs, suggesting that flea antigen-specific IgE level can be correlated to the severity of allergic hyper-reaction. CD4(+) T lymphocytes and IL-4 rather than IL-10, or IFN-gamma were found to be the predominant cytokines associated with the clinical onset of allergic symptoms in C57BL/6 mice. Further, histopathologic analysis indicated that not only mast cells had infiltrated into the area of the skin lesion, but the damage was found to be at a stage where mast cells were degranulating causing considerable exacerbation of the local injury. In conclusion, this murine allergic dermatitis model induced by flea antigens may provide a useful means to evaluate vaccines or immunodulatory drugs; thus providing researchers with a tool to study allergy-related disorders and other parameters needed in the area of allergic investigations.

Alopecia↗
PubMed2002

Water flea Moina macrocopa as a novel biocarrier of norfloxacin in aquaculture.

The potential of using water flea Moina macrocopa as a novel live drug carrier to freshwater aquatic animals has been evaluated. The incorporation of antibacterial, norfloxacin into Moina and subsequently into fish was quantified. The efficiency of drug incorporation into water flea depends on both drug concentration in enrichment medium and incubation time. The maximum drug level in Moina following bioencapsulation technique was reached at 4 h of exposure at drug concentrations of 10-20% (w/w) (0.70-0.90 mg/g dry weight of water flea). Significant higher drug uptake was obtained (1.902+/-0.228 mg/g dry weight of water flea) in 2 h at the drug concentration of 40%. A marked decrease of norfloxacin percentage level upon storage of the Moina in water was observed and the survival of the Moina up to 2 h was satisfactory. It was suggested that medicated water flea should be either administered freshly enriched to fish or after short duration of storage. Following oral administration of medicated water flea to fish, the level of drug in fish body tissue increased as the number of doses increased, and the drug level was highest after a three-dose feeding. This primary food source appears to be a promising drug delivery system to aquatic animals.

Animals↗
PubMed2000

Efficacy and safety of selamectin against fleas on dogs and cats presented as veterinary patients in Europe.

Two controlled and masked multi-centre studies were conducted to examine the efficacy of a novel topical avermectin, selamectin, against natural flea infestations on 418 dogs and 345 cats. Veterinary patients with viable flea infestations were enrolled in the studies, which were conducted in United Kingdom, France, Germany, and Italy. Animals were allocated randomly in a 2:1 ratio to one of two treatments: either selamectin alone at a minimum dosage of 6mgkg(-1) or fenthion at recommended dose rates. Concurrent use of an environmental spray (containing methoprene and either pyrethrins or permethrin) was permitted only for fenthion-treated animals. In-contact cats and dogs (animals living in the same home) received the same treatment as the first animal enrolled from the household, if recommended by the veterinarian. Study day 0 was defined as the day of first treatment. Animals were treated on days 0, 30, and 60, and flea comb counts and clinical evaluations were conducted on days 0, 14, 30, 60, and 90. Analysis of variance of ln(flea count+1) showed that values were significantly lower for selamectin alone compared with fenthion (with or without the concurrent use of an environmental spray) in dogs on days 30, 60, and 90 (P<0.05) and in cats on days 14, 30, 60, and 90 (P<0.01). For selamectin, the reductions in geometric mean flea counts on days 14, 30, 60, and 90, compared with day 0, were 92.5, 90.7, 98.1, and 99.1%, respectively, for dogs and 92.8, 92.7, 97.7, and 98.4%, respectively, for cats. Selamectin was shown to be safe and highly effective in the control of naturally acquired flea infestations on dogs and cats presented as veterinary patients in Europe.

Animals↗
PubMed2002

Development of a mouse model to determine the systemic activity of potential flea-control compounds.

Probe studies were performed to determine if the cat flea (Ctenocephalides felis), the most common ectoparasite of companion animals, will feed on laboratory mice and, if so, to incorporate this into a small animal assay to detect systemically active compounds. Consequently, a protocol was developed which incorporated acepromazine maleate to temporarily sedate various strains of mice and allow fleas a window of time to feed undisturbed. For validation of the model, CD-1 mice were dosed per os with seven known insecticides at 30, 10 and 1mg/kg. Mice were sedated with 0.0125 ml acepromazine maleate intraperitoneally, and infested with fleas. After 2h, fleas were removed, one-third were examined immediately to confirm the occurrence of feeding, and 77% were found to have ingested a blood meal. The remaining fleas were incubated for 24h to determine mortality. Nitenpyram, the active ingredient in Capstar, was highly active (>94%) at 1mg/kg. Selamectin, the active ingredient in Revolution, was very active (86%) at 10mg/kg, but inactive at 1mg/kg. Fipronil, the active ingredient of Frontline Topspot, was very active (83%) at 30 mg/kg, moderately active (54%) at 10mg/kg and inactive at 1mg/kg. Cythioate, the active ingredient in Proban, and nodulisporic acid, a recently discovered oral insecticide, were moderately active (64 and 55%, respectively) at 10mg/kg, but both were inactive at 1mg/kg. Lufenuron and ivermectin exhibited no efficacy at any level tested. These findings suggest that this mouse model can effectively identify systemic flea-control leads and, subsequently, reduce the use of large animals in research.

Animals↗
PubMed2002

Evaluation of the comparative efficacy of selamectin against flea (Ctenocephalides felis felis) infestations on dogs and cats in simulated home environments.

The comparative efficacy of monthly administration of selamectin or lufenuron against Ctenocephalides felis felis on dogs and cats was evaluated over a 5-month period in flea-infested environments. Twenty-four dogs and 32 cats were randomly allocated to receiving a topical treatment with selamectin or an oral administration of tablets containing lufenuron/milbemycin oxime (for dogs) or lufenuron only (for cats). Each product was administered in accordance with the manufacturer's label recommendations. Eight dogs and four cats served as untreated sentinels. Treatments were administered on days 0, 30, 60, 90, and 120. Each animal received an application of 100 fleas on days -28 and -21, and then weekly applications of 20 fleas from days 91 through 147. Flea comb counts were performed on day -6, and every 2 weeks after day 0. From day 29 (dogs) or day 44 (cats) to day 150, geometric mean flea counts for selamectin were < or =0.4. Mean flea counts for animals assigned to treatment with selamectin were significantly lower (P=0.0001) than for animals assigned to treatment with lufenuron at all assessments after day 0.

Animals↗
PubMed2005

Trypanosomes, fleas and field voles: ecological dynamics of a host-vector--parasite interaction.

To investigate the prevalence of a flea-borne protozoan (Trypanosoma (Herpetosoma) microti) in its field vole (Microtus agrestis) host, we monitored over a 2-year period a range of intrinsic and extrinsic parameters pertaining to host demographics, infection status and vector (flea) prevalence. Generalized Linear Mixed Modelling was used to analyse patterns of both flea and trypanosome occurrence. Overall, males of all sizes and ages were more likely to be infested with fleas than their female counterparts. Flea prevalence also showed direct density dependence during the winter, but patterns of density dependence varied amongst body mass (age) classes during the summer. Trypanosome prevalence did not vary between the sexes but was positively related to past flea prevalence with a lag of 3 months, with the highest levels occurring during the autumn season. A convex age-prevalence distribution was observed, suggesting that individuals develop a degree of immunity to trypanosome infection with age and exposure. An interaction between age and whether the individual was new or recaptured suggested that infected animals are less likely to become territory holders than their uninfected counterparts.

Animals↗
PubMed2002

High-frequency conjugative transfer of antibiotic resistance genes to Yersinia pestis in the flea midgut.

The acquisition of foreign DNA by horizontal transfer from unrelated organisms is a major source of variation leading to new strains of bacterial pathogens. The extent to which this occurs varies widely, due in part to lifestyle factors that determine exposure to potential donors. Yersinia pestis, the plague bacillus, infects normally sterile sites in its mammalian host, but forms dense aggregates in the non-sterile digestive tract of its flea vector to produce a transmissible infection. Here we show that unrelated co-infecting bacteria in the flea midgut are readily incorporated into these aggregates, and that this close physical contact leads to high-frequency conjugative genetic exchange. Transfer of an antibiotic resistance plasmid from an Escherichia coli donor to Y. pestis occurred in the flea midgut at a frequency of 10-3 after only 3 days of co-infection, and after 4 weeks 95% of co-infected fleas contained an average of 103 antibiotic-resistant Y. pestis transconjugants. Thus, transit in its arthropod vector exposes Y. pestis to favourable conditions for efficient genetic exchange with microbial flora of the flea gut. Horizontal gene transfer in the flea may be the source of antibiotic-resistant Y. pestis strains recently isolated from plague patients in Madagascar.

Animals↗