Distribution of cat fleas (Siphonaptera: Pulicidae) on the cat

A total of 3,382 cat fleas, Ctenocephalidesfelis (Bouche), was taken from 164 of the 200 stray cats examined. It was observed that cat fleas preferred specific areas on the cat. A significantly higher mean number of fleas was found on the area of head plus neck than on the ventral part of the body. More specifically, the mean number of fleas was highest on both of the neck and dorsal areas. However, in terms of the density of fleas, the neck had more fleas than the dorsal area did. The fewest fleas were found infesting the legs and tail. Distribution of fleas on the cat may well be explained by the various grooming patterns of the cat, and the knowledge of flea distribution may be valuable for application of on-animal flea control procedures.     

Use of DNA hybridizations probes for detection of the plague bacillus (Yersinia pestis) in fleas (Siphonaptera: Pulicidae and Ceratophyllidae)

The detection of active plaque in nature relies primarily on demonstration of the etiologic agent of the disease. Yersinia pestis, in the flea vectors and susceptible mammalian hosts. A live animal assay is currently used for identification of a Y. pestis virulence antigen that is not expressed in the flea. We have found that DNA hybridization probes specific for Y. pestis, used in very simple sample preparation schemes, allow detection of Y. pestis in three species of fleas as well as tissues of experimentally infected mice at minimum concentrations of 1 x 10(6) bacilli/ml. We detected Y. pestis in 22 of 90 (24%) experimentally infected Xenopsylla cheopis (Rothschild), 13 of 25 (52%) Thrassis bacchi (Rothschild), and 9 of 25 (36%) Diamanus montanus (Baker), but no hybridization signals were observed from fleas that had fed on normal mice. The probe technique indicated infection in 9 of 10 potentially infected liver and spleen samples and none of the 5 control samples. Our techniques permit definitive diagnosis in 48 h.     

Quantities of Yersinia pestis in fleas (Siphonaptera: Pulicidae, Ceratophyllidae, and Hystrichopsyllidae) collected from areas of known or suspected plague activity

We used a quantitative competitive polymerase chain reaction (PCR) (QC-PCR) to determine bacterial loads in 669 fleas collected in areas of confirmed and suspected plague epizootics. Fleas were collected out of rodent burrows (67.9%) and off of captured animals (24.1%) and rodent carcasses (8.1%). An initial PCR screening assay indicated that 12.1% (81/669) of all fleas were positive for Yersinia pestis. Fleas collected from burrows had significantly lower (chi2 = 264.9, P < 0.0001) infection rates (6.8%) but significantly higher (Student t-test, P < 0.0001) bacterial loads (mean = 10(5.6) Y. pestis per flea) than fleas collected off of rodent carcasses (infection rate = 92.6%; mean bacterial load = 10(4.8) Y. pestis per flea). None of the fleas collected off of captured animals were positive for Y. pestis by PCR, although seven of the 176 captured animals were serologically positive for Y. pestis.     

Laboratory techniques for rearing the fleas (Siphonaptera: Ceratophyllidae and Pulicidae) of California ground squirrels (Rodentia: Sciuridae) using a novel nest box

Three species of fleas, Oropsylla montana (Baker), Hoplopsyllus anomalus (Baker), and Echidnophaga gallinacea (Westwood), occur seasonally on the California ground squirrel, Spermophilus beecheyi (Richardson). Few studies have focused on the biology and ecology of these fleas despite their importance in the epidemiology of sylvatic plague. To best duplicate a natural parasite-host relationship in the laboratory, a novel nest box was developed that facilitated housing wild-caught S. beecheyi, was conducive to rearing fleas, and met modern standards for laboratory animal hygiene. This flexible system allowed adult fleas with different feeding strategies to be colonized successfully while providing sufficient flea eggs for both colony maintenance and biological research. The techniques described could be adapted to work with other species of rodents and their fleas.     

Rat leucocyte response to the bites of rat fleas (Siphonaptera: Pulicidae)

The host response to bites of the oriental rat flea, Xenopyslla cheopis Rothschild, was investigated by examining rat blood leucocyte kinetics, histopathology, and the effect that the host response had upon subsequent flea feeding and longevity. Test rats were subjected to controlled exposures of fleas, and leucocyte data from test rats were compared to those of unexposed controls. Of the five leucocyte types examined, only the basophil appeared to play a role in the host blood response to flea bites. Significant increases in blood basophil levels occurred 2-3 d after exposure but subsided to control levels within a week. However, flea feeding did not produce histopathology at the flea feeding sites nor did the basophilic blood response of rats affect subsequent feeding or longevity of the fleas.     

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.     

Outdoor survival and development of immature cat fleas (Siphonaptera: Pulicidae) in Florida

In north-central Florida, cat flea, Ctenocephalides felis felis Bouché, larvae survived outdoors year round. Their survival was greatest (up to 84.6%) outdoors in the fall, from September to November, when both temperatures and relative humidities were moderate. Female cat fleas developed faster than males. Development times for flea larvae were shortest (20-24 d) in June and July. From January to March, flea larval mortality was highest (91.7-100%) and development times the longest (36-50 d) outdoors. This was the result of low temperatures and low relative humidities associated with the passage of cold fronts during this time of year. Flea larvae survived light frosts in protected microhabitats such as inside a doghouse and under a mobile home.     

Detection of novel Bartonella strains and Yersinia pestis in prairie dogs and their fleas (Siphonaptera: Ceratophyllidae and Pulicidae) using multiplex polymerase chain reaction

We developed a multiplex polymerase chain reaction (PCR) assay that simultaneously detects three types of flea-associated microorganisms. Targets for the assay were sequences encoding portions of the gltA, a 17-kDa antigen, and pla genes of Bartonella spp. Strong et al., Rickettsia spp. da Rocha-Lima, and Yersinia pestis Yersin, respectively. A total of 260 flea samples containing bloodmeal remnants were analyzed from fleas collected from abandoned prairie dog (Cynomys ludovicianus) burrows at the site of an active plague epizootic in Jefferson County, CO. Results indicated that 34 (13.1%) fleas were positive for Bartonella spp., 0 (0%) were positive for Rickettsia spp., and 120 (46.2%) were positive for Y. pestis. Twenty-three (8.8%) of these fleas were coinfected with Bartonella spp. and Y. pestis. A second group of 295 bloodmeal-containing fleas was collected and analyzed from abandoned burrows in Logan County, CO, where a prairie dog die-off had occurred 2-4 mo before the time of sampling. Of these 295 fleas, 7 (2.4%) were positive for Bartonella spp., 0 (0%) were positive for Rickettsia spp., and 46 (15.6%) were positive for Y. pestis. Coinfections were not observed in fleas from the Logan County epizootic site. The multiplex PCR also was used to identify Y. pestis and Bartonella in prairie dog blood and tissues. This report represents the first identification of Bartonella from prairie dogs and their fleas. Prairie dog fleas were tested with PCR, and the Bartonella PCR amplicons produced were sequenced and found to be closely related to similar sequences amplified from Bartonella that had been isolated from prairie dog blood samples. Phylogenetic analyses indicate that the sequences of bartonellae from prairie dogs and prairie dog fleas cluster tightly within a clade that is distinct from those containing other known Bartonella genotypes.     

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.     

Comparative evaluation of juvenoids for control of cat fleas (Siphonaptera: Pulicidae) in topsoil

The efficacy of a photostable formulation of methoprene and two photostable juvenoids, fenoxycarb and pyriproxyfen, and their residual activity in inhibiting the emergence of adult cat fleas, Ctenocephalides felis (Bouché), was studied in topsoil. Nursery pots composed of clay, peat, and plastic, and wooden flats were used to hold soil samples. Treated soil samples were exposed to sunlight during the 63-d study period. Methoprene was as effective as fenoxycarb and pyriproxyfen against cat fleas for up to 42 d in clay, peat, and plastic pots at a concentration of 64.56 mg (AI)/m2 (6 mg [AI]/ft2), but its activity declined significantly thereafter. In contrast, fenoxycarb and pyriproxyfen showed strong residual activity for the entire 63 d. The activity of methoprene declined even more rapidly over time in wooden flats, while at the same concentrations the other two juvenoids showed significant residual activity for 63 d. Clay, peat, and plastic pots were therefore considered to be equally effective for evaluating the outdoor efficacy of juvenoids in comparison to the wooden flats. However, results obtained with wooden flats may be more realistic when testing residual activity of volatile chemicals such as methoprene. Fenoxycarb and pyriproxyfen showed strong efficacy and residual activity at concentrations of 8.07, 16.14, and 32.28 mg (AI)/m2, whereas methoprene did not cause a significant reduction of adult emergence at levels below 64.56 mg (AI)/m2. LC50 values for methoprene, fenoxycarb, and pyriproxyfen needed for preventing flea emergence when applied to topsoil were estimated to be 0.643, 0.031, and 0.028 ppm, respectively.     

Influence of photoperiod on egg production of cat fleas (Siphonaptera: Pulicidae) infesting cats.

Photoperiod affected the production of cat flea eggs by cats infested with cat flea, Ctenocephalides felis (Bouché). Cat flea eggs have a smooth chorion and do not adhere to the host. About 60% of fluorescing eggs placed in the pelage were recovered in collecting trays underneath the host in 2 h. An average of 87.7 eggs per cat was laid during the last 8 h of the scotophase compared with 49.9 and 59.1 eggs during the other 8-h periods. Significant variation in the number of eggs collected daily existed among the six cats. The activity budgets were similar for all the cats with the maximum sleep period during the photophase. The possible adaptive advantages of synchronizing egg production with photoperiod are discussed.     

Field evaluation of Nylar for control of cat fleas (Siphonaptera: Pulicidae) in home yards

Procedures were developed to evaluate juvenoid insect growth regulators in home yards as part of an ongoing program to identify photostable insecticides for control of the cat flea, Ctenocephalides felis (Bouché). Nylar, an emulsifiable concentrate formulation of pyriproxyfen, was selected as the experimental insect growth regulator. Efficacy studies, yard survey, and pretreatment sampling techniques are described. Soil samples collected from the yards at intervals after treatment were taken to the laboratory, infested with flea larvae, and tested for juvenoid activity. Results indicated that Nylar applied at a concentration of 32 mg/m2 in 0.82 liter of water/m2 (20 gal/1,000 ft2) prevented development of approximately 80% of the fleas for a period of 3 wk.     

Effects of pyriproxyfen spray, powder, and oral bait treatments on the relative abundance of fleas (Siphonaptera: Ceratophyllidae) in black-tailed prairie dog (Rodentia: Sciuridae) towns

Separate black-tailed prairie dog, Cynomys ludovicianus (Ord), towns on the Rocky Mountain Arsenal National Wildlife Refuge, Colorado, were treated with technical pyriproxyfen (Nylar) using spray, powder, and oral bait carriers. Direct combing methods (1997 and 1998) and burrow flagging (1998) were used to estimate relative abundance of the plague vector Oropsylla hirsuta (Baker). Pyriproxyfen spray (0.05%) and powder (0.05%) did not significantly reduce (P > 0.05) O. hirsuta abundance. Pyriproxyfen bait, when applied every 4 wk at a concentration of 286 mg/50 g bait, significantly reduced (P < or = 0.05) O. hirsuta infesting prairie dogs, 4 mo after initial treatment. However, flea populations had recovered to pretreatment levels by the following summer (July 1999).     

Presence in France of a selvatic Xenopsylla: X. cunicularis Smit, 1957 (Siphonaptera, Pulicidae), a parasite of wild rabbits

The authors point out, for the first time in France, a selvatic Xenopsylla: X. cunicularis Smit, 1957, parasite on the European rabbit, well-known in Morocco and Spain until today. The paleogeographical, ecological, and epidemiological interest of this parasite is laid stress on. The other fleas linked to the European rabbit are evoked, and the acclimatization of Euphoplopsyllus glacialis affinis (Baker, 1904), in France and Italy, introduced with its host Sylvilagus? floridanus is related.     

Determining a diagnostic dose for imidacloprid susceptibility testing of field-collected isolates of cat fleas (Siphonaptera: Pulicidae)

The susceptibility of four laboratory strains of cat fleas, Ctenocephalides felis (Bouche), to imidacloprid was determined by three different laboratories, by using a standardized bioassay protocol. The probit lines generated by the different laboratories were very similar, with LC50 values ranging from 0.32 to 0.81 ppm. Based on these data, a diagnostic dose (DD) of 3 ppm imidacloprid in larval rearing media was provisionally identified for detecting shifts in tolerance, possibly as a consequence of incipient imidacloprid resistance. None of the larvae from the susceptible laboratory strains survived the DD. Eighteen field-collected isolates were evaluated for their susceptibility to imidacloprid and to validate a DD of 3 ppm. Probit lines from 18 field-collected isolates were very similar, with LC50 values ranging from 0.14 to 1.52 ppm. When exposed to the DD, between 3 and 10% of the exposed larvae emerged as adults from only three of the 18 isolates. All other field isolates gave 100% mortality at the DD. Under the criteria established (>5% survivorship at 3 ppm), two isolates would be established on mammalian hosts and more extensive tests conducted to exclude or confirm the presence of resistance. The DD of 3 ppm is robust enough to eliminate most of the susceptible isolates collected until today, yet low enough to identify possible isolates for further testing.     

Insecticide susceptibilities of cat fleas (Siphonaptera: Pulicidae) from several regions of the United States

Eleven cat flea, Ctenocephalides felis (Bouchè), strains, seven field-collected and four laboratory-colonized, were assayed for susceptibilities to five insecticides (carbaryl, chlorpyrifos, malathion, permethrin, and pyrethrin) with an insecticide-treated, horizontally-oriented, Nylon 6,6 disk in a test tube. The pyrethrin was synergized using piperonyl butoxide (PBO). Flea mortality at two doses was recorded after 4 and 24 h exposures. The field strains from Texas and Florida tolerated carbaryl, chlorpyrifos, and malathion; and carbaryl and PBO-synergized pyrethrin, respectively. Tolerance was observed in a field strain from Kansas against malathion. Colonies from California and North Carolina were susceptible to malathion and PBO-synergized pyrethrin, and chlorpyrifos and permethrin, respectively, but three colonies showed tolerance. The insecticidal response of the California colony varied; when exposed to a chlorpyrifos dose of 10 mg (AI)/m2 for 24 h, at various times had mortality of 3-100%. With a PBO-synergized pyrethrin dose of 396 mg (AI)/ m2 for 4 h, the mortality ranged between 4.2 and 97%. Colonized strains were more susceptible than field strains at 4 h exposure to all insecticides except PBO-synergized pyrethrin. Colonized strains survived better in control tubes. The colony strains' susceptibility and variability are of considerable importance because these strains are used for flea product efficacy evaluations and bioassays. The differences in susceptibility between laboratory colonies and the field strains suggested development of both adaptation to colonization, and extensive, multiple cross-resistance to insecticides in field strains. Varying susceptibility of cat fleas may affect control success.     

Prevalence and biology of endosymbionts of fleas (Siphonaptera: Pulicidae) from dogs and cats in Alachua County, Florida

A study was conducted to determine the prevalence and biology of endosymbionts in local populations of fleas collected from dogs and cats in Alachua Co., Florida. Four hundred three Ctenocephalides felis (Bouché), 194 Pulex simulans Baker, and 44 Echidnophaga gallinacea (Westwood) were examined. Fleas were collected from 52 dogs and 51 cats. From 1 to 20 fleas were dissected from each host. A variety of microorganisms and metazoa was observed, including a baculovirus, gram-negative bacteria, rickettsia-like organisms, amoebae, trypanosomatid flagellates, cephaline gregarines, and microsporidia. Microfilariae of the dog heartworm, Dirofilaria immitis, entomophilic nematodes, and metacestodes of the tapeworm Dipylidium caninum were also observed.     

Water balance in two species of desert fleas,Xenopsylla ramesis and X. conformis (Siphonaptera: Pulicidae)

The role of water balance capabilities of fleas was examined in desert habitats. The fleas studied were Xenopsylla ramesis Rothschild and Xenopsylla conformis Wagner. Both fleas occur on Sundevall's jird, Meriones crassus, in the Negev Highlands of Israel but in different macro- and microhabitats. Because M. crassus occurs in several habitats of the highlands, it was used as a model for investigating the effect of habitat parameters on species composition of fleas within a host species. Water balance parameters investigated were the range of humidities over which active water uptake occurs in the larvae and prepupae of X. ramesis and X. conformis. Critical equilibrium humidity estimates were close to 65% RH for larvae and prepupae of both species. Water loss rates were determined for each life stage, except eggs, and represented water loss from cuticular, respiratory, and other body openings) under conditions of little or no bulk air movement. When converted to a proportional rate (1.44 -2.37% mass loss h(-1)) water loss rates did not differ significantly between stages or species. Thus, geographic separation of X. ramesis and X. conformis could not be explained by any difference in water uptake capabilities or water loss rates. Other factors that may be important include interspecific competition for resource availability among larval fleas and effect of soil texture on cocoon construction.