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PubMed1998

Description of Songshupsylla, a new subgenus of Macrostylophora (Siphonaptera: Ceratophyllidae), with a discussion of its species groups.

The new subgenus Songshupsylla is erected to include certain species heretofore included in Macrostylophora s. lat. Ewing, 1929. The subgenus is further divided into 2 species groups according to their morphological characters and geographical distribution in the Paleartic and Oriental Regions. Brief descriptions of these species groups and the names of the Chinese taxa are given.

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PubMed1998

Quantitation of cat immunoglobulins in the hemolymph of cat fleas (Siphonaptera: Pulicidae) after feeding on blood.

Passage of ingested cat immunoglobulin G (IgG) into the hemocoel of cat fleas, Ctenocephalides felis (Bouché), was examined using antibody capture enzyme-linked immunosorbent assays (ELISA) and Western blotting. Fleas were fed heparinized cat blood via membrane feeders. Cat IgG was present in the hemolymph of engorged female fleas 1 h after ingestion at an estimated quantity of 35 +/- 14 micrograms/ml. The prevalence of fleas with demonstrable cat IgG in their hemolymph 1 h after feeding was 100% for both female and male fleas. Following a single blood meal, cat IgG was present in the hemolymph of all 15 fleas tested 1 h after ingestion but dissipated below detectable levels in 10 of 20 fleas examined 3 h after ingestion, and was detectable in only 1 of 10 fleas examined 18 h after ingestion. However, when fleas were provided with continual access to blood over a 72-h period, IgG content in hemolymph, as measured in excised, triturated legs of individual fleas, remained fairly constant (3-16 pg IgG per sample). Flea feeding studies using specific antisera indicated that IgG in flea hemolymph retained its binding activity, and that at least a portion of the IgG was intact. Passage of ingested host antibody from gut into hemocoel is a prerequisite for the possible development of antiflea vaccines that target antigens outside of the flea midgut lumen (e.g., key components of the flea endocrine system controlling oogenesis).

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PubMed1998

Molecular identification of Rickettsia typhi and R. felis in co-infected Ctenocephalides felis (Siphonaptera: Pulicidae).

Rickettsia typhi and R. felis, 2 closely related rickettsial species, often have been identified in cat fleas, Ctenocephalides felis (Bouché) from the same geographical location. However, no fleas have been found to be naturally infected concurrently with both rickettsial species. To examine whether one rickettsial species can develop simultaneously with another species in the same flea host, cat fleas, naturally infected with R. felis, were allowed to feed on blood containing R. typhi (Ethiopian strain, 10(7) PFU/ml). Experimental controls consisted of uninfected cat fleas, fleas infected with only R. typhi; and fleas naturally infected with only R. felis. After 9 d at 28 degrees C, the fleas were examined by PCR amplification and subsequent restriction digest analysis and dot blot hybridization of PCR products. Results from these studies demonstrated that R. felis and R. typhi are capable of co-existing in the same flea host. Subsequent isolation of R. typhi from dually infected fleas by tissue culture indicated that R. typhi was viable and capable of being maintained in fleas naturally infected with R. felis. As more studies confirm the presence of R. felis and R. typhi in domestic pets and peridomestic vertebrates in urban areas, the ability of the individual cat fleas, which live on these animals, to support both rickettsial species could be an epidemiologically important consideration.

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PubMed1998

Review of insecticide resistance in cat fleas (Siphonaptera: Pulicidae).

Insecticide resistance often is blamed for failures of insecticides to control cat fleas, Ctenocephalides felis (Bouché). Yet the genetics and adaptive advantage of resistance traits remain unexamined. Lethal doses of insecticides that kill 50% of the population fluctuate 7-fold within a cat flea strain. Many reports of flea resistance may be attributable to variable mortality from effects of solvents, substrates, humidities, temperatures, colonization, and ages of fleas. Resistance ratios (ratios of lethal doses of a resistant to a susceptible strain) are < 690-fold in fleas; lower than many other arthropods. This, plus strain variability, hinders resistance detection. Relationships between resistance levels, control failures, and health threats are unclear. Insensitive acetylcholinesterase, knockdown recovery, glutathione transferase conjugation, and mixed function oxidase/cytochrome P450 are demonstrated resistance mechanisms in cat fleas. Ecological genetics of resistance in cat fleas probably involves flea transfer among hosts, host movements, refugia, founder effects, and mortality from abiotic factors. Understanding cat flea resistance requires population monitoring before, during, and after insecticide treatments using conventional and rapid molecular bioassays. Sustained insecticide release devices such as flea collars and long-lived insecticide residues for premises possibly contribute to the development of resistance. New systemic and topical insecticides, especially when given prophylactically, may act similarly. Eliminating insecticides prevents insecticide resistance but necessitates application of biorational tactics incorporating mechanical, environmental, and cultural controls. Using high temperatures, low humidities, host grooming and such tactics as decreasing doses, increasing action thresholds, rotating insecticides, and leaving spatial and temporal refugia may suppress cat flea resistance.

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PubMed1998

Reproductive status of four species of fleas (Insecta: Siphonaptera) on Richardson's ground squirrels (Rodentia: Sciuridae) in Manitoba, Canada.

To test the hypothesis that oogenesis in 4 species of fleas is dependent on the reproductive cycle of their monoestrous host Spermophilus richardsonii, 6,416 Oropsylla (Oropsylla) rupestris (Baker), 5,893 Oropsylla (Opisocrostis) bruneri (Baker), 813 Neopsylla inopina (Rothschild), and 223 Rhadinopsylla (Actenophthalmus) fraterna (Baker) females were collected from active hosts at 3 locations in Manitoba during 1987, 1988, and 1989 and dissected. Based on morphological changes in the ovaries, female fleas were categorized as immature, nulliparous or parous. Nulliparous N. inopina predominated in April and early May. Immature and nulliparous O. bruneri predominated throughout April and May. Nulliparous O. rupestris were most prevalent in early June but occurred sporadically throughout the season. Nulliparous R. fraterna predominated only in April. The percentage of mated females was usually correlated with percentage parity for all species. Oogenesis in each of the 4 flea species was apparently independent of the reproductive cycle of their host. Female fleas of all reproductive categories were frequently collected before, during, and following reproduction in their hosts.

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PubMed1998

Hybridization in North American bird fleas of the genus Ceratophyllus (Siphonaptera: Ceratophyllidae).

Evidence is presented suggesting hybridization in several species in the genus Ceratophyllus. Suspected interbreeding is reported as follows: C. idius x C. niger; C. celsus x C. scopulorum; C. celsus x C. petrochelidoni. The 1st of these was described as C. niger inflexus (Jordan, 1929). The 2nd was described as C. calderwoodi Holland, 1979, and the 3rd has been considered a dimorphic form of C. celsus (Holland 1985).

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PubMed1998

Experimental infection of domestic cats with Bartonella henselae by inoculation of Ctenocephalides felis (Siphonaptera: Pulicidae) feces.

Caged cat fleas, Ctenocephalides felis (Bouché), were fed on 6 cats; 3 cats were injected with 5 x 10(7) colony forming units of Bartonella henselae intradermally and 3 cats were injected with an equal volume of saline. After the fleas fed for 4 d, 5 groups of 50 B. henselae-exposed fleas were caged and allowed to feed on 5 cats for 6 d. Five cats each were injected intradermally with 1 ml of saline containing 45 mg of feces from B. henselae-exposed fleas. Five cats were fed 50 B. henselae-exposed fleas and 45 mg of fresh feces from B. henselae-exposed fleas. Five cats received all 3 treatments by using fleas and feces collected from cats inoculated with saline (controls). Cats were bled weekly and tested by culture and serology. The cats that were injected with feces from infected fleas were positive by culture for B. henselae at 1 or 2 wk after exposure and were the only cats to become bacteremic or seropositive by week 20.

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PubMed1998

Mode of action of lufenuron on larval cat fleas (Siphonaptera: Pulicidae).

Adult cat fleas, Ctenocephalides felis (Bouché), were fed suboptimal in vitro concentrations of lufenuron in blood to allow hatching of flea larvae for cytological study. At concentrations of 0.125, 0.25, and 0.5 ppm, larval hatch was 64, 15, and 4%, respectively. Larvae hatching from eggs laid by adults fed lufenuron at concentrations of 0.025, 0.08, or 0.125 ppm did not differ significantly from the control. However, many larvae from the 0.08-ppm group and higher concentrations died during the 1st instar. Examination of these larvae revealed that they were dying from desiccation caused by bleeding from microscopic lesions in the cuticle or the inability to complete the molt to the next instar. Electron micrographs showed that lufenuron often disrupted formation of the endocuticle resulting in the deposition of an amorphous mass of randomly oriented chitin microfibrils. Other larvae formed normal endocuticle but were unable to digest the old endocuticle or produce new procuticle after apolysis. Failure of larvae to digest old cuticle or form new cuticle was caused by degeneration of the epidermal cells needed for the synthesis of molting fluid and chitin.

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PubMed1999

Effect of lufenuron on chorionic and cuticular structure of unhatched larval Ctenocephalides felis (Siphonaptera: Pulicidae).

When adult cat fleas, Ctenocephalides felis (Bouché), were fed concentrations of < or = 0.08 ppm lufenuron in cattle blood, egg hatch did not differ significantly from the controls. However, as the concentration of lufenuron in blood increased from 0.125 to 1.0 ppm egg hatch decreased to 64 and 2%, respectively. Most of these eggs contained fully developed larvae. Microscopic examination of unhatched larvae, revealed that the cuticle epidermal cells, chorion, and vitelline membrane all were affected by lufenuron treatment. Larvae often produced 2 separate cuticles in response to treatment. The 1st cuticle consisted of an indistinct layer of epicuticle and a procuticle composed of randomly deposited chitin microfibrils. After the 1st layer of procuticle separated from the epidermal cells, a 2nd layer of procuticle was deposited. It was not possible to determine whether the egg tooth was functional during larval hatch. The surface of the egg tooth appeared normal, but the cuticle may have had structural abnormalities similar to those seen in other areas of the exoskeleton. Structural defects appeared to be due to the cytotoxic effects of lufenuron. The epidermal cells of treated larvae showed evidence of disintegration (i.e., the nuclei and mitochondria appeared to be degenerating and the amount of endoplasmic reticulum and other cytoplasmic organelles was decreased). The chorion of lufenuron-treated larvae consisted of an outer layer, middle and inner layers that were thinner and less electron dense than those of controls, and lacked the innermost chorionic layer found in the control larvae. The vitelline membrane also was thinner than that of the controls. Larval hatching was prevented by ruptures in the cuticle, which opened during eclosion resulting in the loss of hemolymph and desiccation of the larva. Evidently, tearing of the cuticle was caused by abnormal formation of the procuticle that was not strong enough to withstand the cuticular expansion and muscular movement of the larva within the egg shell.

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PubMed1999

Chorion formation and ultrastructure of the egg of the cat flea (Siphonaptera: Pulicidae).

Oocyte development in adult female cat fleas, Ctenocephalides felis (Bouché), was studied by light and electron microscopy to determine the formation and ultrastructural morphology of the eggshell. As oocytes develop, somatic follicle cells from the lining of the ovariole migrate around the oocytes. The follicle cells produce electron-dense granules that form the vitelline membrane around the developing oocyte. Subsequently, electron-lucent granules containing an electron-dense core (precursors of the chorion) are produced from the rough endoplasmic reticulum that appear as dilated and clear linear clefts in the cytoplasm of the follicle cells. Exocytosis and coalescence of the granules around the oocyte as the follicle cells disintegrate give rise to the chorion. The chorion was found to consist of 4 distinct layers. The external surface of the egg shell consists of a particulate layer approximately 760 nm thick, composed of an electron-lucent layer of widely dispersed granules. Embedded in this layer are electron-dense spheres that project above the surface of this granular layer. Beneath this outermost layer is a band of electron-dense material, consisting of densely packed granules and is half as thick as the outer particulate layer. The 3rd layer consists of relatively thick, weakly laminated chorion, with a felt-like appearance due to a meshwork of microfibrils. Projections of this network of microfibrils form pillars that attach this layer to a thin relatively compact 4th or basal layer. The pillars and the air-filled cavities lying between the 3rd and 4th chorionic layers constitute the chorionic meshwork known as the palisades or trabecular layer that form the major respiratory organ of the eggshell. The trabecular layer is connected to the external environment by means of the lateral and anterior aeroplyes. The vitelline membrane lies between the chorion and oocyte and is a granular, uniform, moderately electron-dense layer measuring approximately 260 nm thick. The micropyle at the posterior of the flea egg consists of a rosette of 50-80 apertures and possesses an internal electron-dense plug between the chorion and the vitelline membrane. An aeropyle at the anterior end of the egg consists of a rosette of 40-50 apertures. An inconspicuous aeropyle appears as a cluster of hexagonal or polygonal-shaped plaques on the lateral surface of the chorion. Each plaque contains 3-8 pores.

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PubMed1999

Spray-dried bovine blood: an effective laboratory diet for Ctenocephalides felis felis (Siphonaptera: Pulicidae).

Commercially available spray-dried protein sources were evaluated as replacement laboratory cat flea, Ctenocephalides felis felis (Bouché), larval diets for slaughterhouse-collected heat-dried blood. Percentage of adult emergence of fleas reared on adult flea feces (87.7%) and spray-dried bovine blood (79%) did not significantly differ, and yeast supplementation did not significantly increase adult emergence for spray-dried diets. However, yeast supplementation of heat-dried blood increased percentage adult emergence from 0 to 41.7%. Spray-dried bovine blood was found to be a satisfactory laboratory diet for cat flea larvae.

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PubMed1999

Mode of action of lufenuron in adult Ctenocephalides felis (Siphonaptera: Pulicidae).

When cat fleas, Ctenocephalides felis (Bouché), were fed concentrations of lufenuron in cattle blood ranging from 0.5 to 4 ppm, adult mortality increased in a dose-dependent manner to a maximum of approximately 24% over a period of 10 d. Fleas treated with 0.5 ppm produced abnormal endocuticle consisting of protein globules embedded in an amorphous chitin matrix. At concentrations of 1.0 ppm or greater, endocuticle formation was inhibited. Ultrastructural studies demonstrated that inhibition of chitin synthesis was associated with degeneration of the epidermal cells. The amount of epidermal cytoplasm decreased and cytoplasmic organelles including mitochondria, ribosomes, and golgi showed lytic changes. At least some mortality of treated fleas was likely the result of a weakened endocuticle and the corresponding decrease in resiliency of the cuticle to expansion during blood-feeding and egg production. An unexpected result of lufenuron treatment was the inhibition of midgut epithelial cell differentiation. At concentrations of 0.5 and 1.0 ppm, partially differentiated epithelial cells were seen in the midgut of bloodfed fleas along with fully differentiated cells.

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PubMed1999

Emergence, survival, and fecundity of adult cat fleas (Siphonaptera: Pulicidae) exposed as pupae to juvenile hormone mimics.

Cat flea, Ctenocephalides felis felis (Bouché), adults exposed to sprays of methoprene, pyriproxyfen, or fenoxycarb as cocooned pupae emerged approximately 1 d earlier than adults from water-treated control pupae. Mortality of adult fleas, after exposure to juvenile hormone mimics as pupae, was increased over that of controls. Females had higher mortality than males within the first 48 h of feeding. Fecundity of females exposed as pupae to juvenile hormone mimics was not different from that of controls. Early emergence of preemerged adults from treated cocoons is discussed along with reasons for higher female susceptibility to juvenile hormone mimics.

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PubMed1999

Susceptibility to insect growth regulators and cuticle deposition of the cat flea (Siphonaptera: Pulicidae) as a function of age.

Wandering larval, pharate pupal, pupal, and pharate adult stages of the cat flea, Ctenocephalides felis (Bouché), were identified by examination of cuticular cross sections via scanning electron microscopy. Visible morphological characteristics of each stage were identified and described. Various stages of the flea throughout metamorphosis were exposed to juvenile hormone mimics and insect developmental inhibitors. Wandering larvae treated with juvenile hormone mimics were unable to pupate, whereas treated pharate pupae ecdysed to the pupal stage but were unable to enclose. Pupae and pharate adults did not succumb to juvenile hormone mimic exposure, even at concentrations 3 orders of magnitude greater than those that killed 100% of the wandering larvae and the pharate pupae. Adult females were more susceptible to juvenile hormone mimics than males. Possible explanations for the variation in tolerance to juvenile hormone mimics of the differing stadia are discussed. None of the stages were susceptible to insect developmental inhibitor exposure. Analysis of catecholamines that are precursors of cuticle sclerotization and melanization were measured in the wandering larval through the pharate adult stages of the cat flea. N-acetyldopamine concentration was highest in the pupa stage when the flea had a hard, clear cuticle; N-beta-alanyldopamine concentration was highest during the production of the hard, dark cuticle of the pharate adult; and dopamine fluctuated throughout development but was highest in the pupal stage.

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PubMed2000

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.

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