Effect of larval diet on cat flea (Siphonaptera: Pulicidae) developmental times and adult emergence.

The natural diet of cat flea, Ctenocephalides felis (Bouche), larvae is primarily adult flea feces, but dried bovine blood may be substituted in the laboratory. Percentage adult emergence (79.4% on feces; 78.9% on blood) and developmental times (20.6 d on feces; 17.1 d on blood) did not significantly differ for the two diets. The drying temperature of blood determined its quality; blood dried at 120 degrees C was unsatisfactory for larval development. The dietary value of dried bovine blood was not enhanced when supplemented with brewer's yeast, rodent chow, or a combination of those constituents. Blood particle size ranging from less than 180 to greater than 500u did not affect the value of blood as a diet. Rodent chow, yeast, albumen, hemoglobin, and mixtures of these constituents were unsuitable as larval diets.     

Circadian rhythm of cat flea (Siphonaptera: Pulicidae) locomotion unaffected by ultrasound

Cat fleas, Ctenocephalides felis (Bouché), had a circadian rhythm of locomotion that peaked during the last 2 h of the photophase and declined to a lower level that was maintained throughout the scotophase. Activity was lowest during the first 8 h of photophase. The circadian rhythm of these fleas was not affected by an ultrasonic pest control device.     

Effect of methoprene and diflubenzuron on larval development of the cat flea (Siphonaptera: Pulicidae).

Cat flea larvae, Ctenocephalides felis Bouche, exposed to glass surfaces treated with methoprene concentrations from 0.127 to 1,270 ng/cm2 did not emerge as adults. Most larvae died in the third instar, but those exposed to the 0.127 ng/cm2 concentration formed larval-pupal intermediates. Larvae exposed to glass surface treated with diflubenzuron concentrations from 12.7 to 1,270 ng/cm2 died during the process of molting in all three instars. Exposure of larvae to 12.7 and 127 ng/cm2 diflubenzuron resulted in 15 and 5.2% adult emergence, respectively.     

Susceptibility of the cat flea (Siphonaptera: Pulicidae) to pyrethroids

Adult cat fleas, Ctenocephalides felis felis (Bouché), from two laboratory colonies (one originating in California and one from Florida) were exposed to residues of eight pyrethroids to compare their susceptibilities. The Florida strain was more tolerant than the California strain, with 6.8-, 5.2-, and 4.8-fold tolerance to cyfluthrin, cypermethrin, and fluvalinate, respectively. The Florida strain showed less than 3-fold tolerance to the other five insecticides (permethrin, tralomethrin, d-phenothrin, resmethrin, and fenvalerate). Overall, the pyrethroids were ineffective against the Florida strain.     

The longevity of Leptopsylla segnis fleas (Siphonaptera: Leptopsyllidae)

In experiments, the mean life duration of fleas Leptopsylla segnis on white mice (abundance of fleas within natural limits, up to 10 fleas per mouse) was 22.7 days in females and 18.8 day in males. Maximum life duration was 51 and 37 days respectively. In cases, when the initial numbers of fleas were 20 and 28-34 fleas, the duration of life was decreased. The maximum limit decreased greater than the mean duration of life. A survival dynamics of fleas depended upon the flea number. It was found out, that in cases of high abundance of fleas in the beginning of experiments, the mortality rate of males was lower than in females. During the stay on a host the fleas lost gradually an ability to endure a starvation. Possible mechanisms of the regulation of flea abundance are discussed.     

Pupation site selection of cat fleas (Siphonaptera: Pulicidae) in various carpet types and its influence on insecticide efficacy

Pupation sites of cat flea, Ctenocephalides felis (Bouché), larvae were determined in three styles of nylon and one style of wool carpet. Nylon saxony carpet had 59.3% of pupae at the top of the pile and 40% at the base of the pile. In nylon contract carpet, 55.2% of pupae were found at the top, 42.6% in the middle, and only 2.2% at the base of the pile. Nylon loop carpet contained 59.2% of pupae at the base, 25.5% in the middle, and 15.3% in the top of the pile. Wool loop carpet had 92.4% at the base and 3.8% both in the middle and top of the pile. Bioassays comparing the control of pupae manually placed at the base of carpets to that in carpets with natural pupation showed that control of pupae in the latter was 39-68% higher. Pupal control after natural pupation was greatest in nylon saxony and nylon contract carpets and lowest in nylon loop and wool loop carpets. Additional studies demonstrated that vacuuming provided the same level of pupal control on nylon saxony carpet as a spray application of permethrin to the carpet surface. Therefore, pupae that survived chemical and mechanical control treatments in nylon saxony carpet probably pupated away from the surface of the pile. Application of permethrin to the base of nylon saxony carpet did not significantly increase control. Future bioassays with cat flea pupae in carpet should be performed after natural pupation and consider carpet make and style.     

Investigation of Bartonella acquisition and transmission in Xenopsylla ramesis fleas (Siphonaptera: Pulicidae)

Bartonella are emerging and re-emerging pathogens affecting humans and a wide variety of animals including rodents. Horizontal transmission of Bartonella species by different hematophagous vectors is well acknowledged but vertical transmission (from mother to offspring) is questionable and was never explored in fleas. The aim of this study was to investigate whether the rodent flea, Xenopsylla ramesis, can acquire native Bartonella from wild rodents and transmit it transovarially. For this aim, Bartonella-free laboratory-reared X. ramesis fleas were placed on six naturally Bartonella-infected rodents and six species-matched Bartonella-negative rodents (three Meriones crassus jirds, two Gerbillus nanus gerbils and one Gerbillus dasyurus gerbil) for 7 days, 12-14h per day. The fleas that were placed on the Bartonella-positive rodents acquired four different Bartonella genotypes. Eggs and larvae laid and developed, respectively, by fleas from both rodent groups were collected daily for 7 days and molecularly screened for Bartonella. All eggs and larvae from both groups were found to be negative for Bartonella DNA. Interestingly, two of five gut voids regurgitated by Bartonella-positive fleas contained Bartonella DNA. The naturally infected rodents remained persistently infected with Bartonella for at least 89 days suggesting their capability to serve as competent reservoirs for Bartonella species. The findings in this study indicate that X. ramesis fleas can acquire several Bartonella strains from wild rodents but cannot transmit Bartonella transovarially.     

The effect of substrate on survival and development of two species of desert fleas (Siphonaptera: Pulicidae)

Fleas Xenopsylla conformis mycerini and Xenopsylla ramesis replace each other on the same rodent host (Meriones crassus) in two habitats that differ in substrate texture (sand and loess-like sediments, respectively). We hypothesized that the substrate is an important factor determining flea distribution and studied survival of larvae, pupae and newly emerged adults as well as the rate of pre-imaginal development of these flea species in sand and loess rearing medium (= substrate). Texture of rearing medium did not affect survival and development rate of eggs in either X. c. mycerini or X. ramesis. Larval survival and the rate of development were both affected by the factor of substrate. Survival of X. c. mycerini larvae was significantly higher in sand than in loess substrate, whereas survival of X. ramesis larvae did not differ in different substrates. Larvae of both species developed faster in sand substrate than in loess substrate. Maximal survival time of X. c. mycerini larvae that died before pupation did not depend on substrate, whereas X. ramesis larvae survived significantly longer in loess than in sand substrate. Most pupae of both species survived successfully on both substrates, but the duration of pupal stages in sand substrate was longer than that in loess substrate in both species. Newly emerged adults of both species survived similar time in both sand and loess substrate. Irrespective of substrate, adult X. c. mycerini survived for a shorter time than did adult X. ramesis. No between-sex within-species differences in survival time of newly emerged adults in sand versus loess substrate were found in X. c. mycerini. Survival time of males and females of X. ramesis differed in sand substrate but not in loess substrate.     

Cytogenetics of fleas (Siphonaptera: Pulicidae). 1. Rat fleas of the genus Xenopsylla

Five populations of Xenopsylla cheopis exhibit a chromosome complement of 2n = 17, X1X2Y (male), and 2n = 18, X1X1X2X2 (female). A detailed analysis of populations of X. astia from Bombay and Trivandrum led to the identification of two distinct cytotypes which hybridisation studies indicated were sibling species. These are referred to as X. astia with a diploid chromosome number of 2n = 18, X1X2X3Y (male), and 2n = 20, X1X1X2X2X3X3 (female) and X. prasadii with 2n = 10, X1X2Y1Y2 (male), and 2n = 10 X1X1X2X2 (female). It is proposed that X. prasadii is derived from X. astia through translocation/fusion events since the average total chromosome lengths are remarkably similar in all three species.     

Water uptake in the cat flea Ctenocephalides felis (Pulicidae: Siphonaptera)

To counteract water loss due to excretion, cuticular transpiration and respiration, various groups of arthropods have developed mechanisms for active uptake of water vapor from unsaturated air. In this study, active uptake capabilities and water loss rates were examined in the various developmental stages of the cat flea, Ctenocephalides felis. To determine critical equilibrium humidity, the lowest relative humidity at which active water uptake can occur, pre-desiccated immature and adult fleas were placed in a series of humidity regimes ranging from 44 to 93% RH. Active uptake occurred in larval stages at relative humidities above 53% and in pre-pupae at 75-93% RH. Pupae and adults did not demonstrate active uptake at any humidity. Optimal uptake for larvae occurred between 20 and 30 degrees C. When placed over Drierite (<10% RH), larval and adult stages demonstrated a higher rate of water loss than pre-pupal and pupal stages. Active water uptake is necessary to ensure proper development of the larvae of C. felis. Active uptake ceases after the larval-pupal ecdysis and it appears that adults have lost the ability to actively uptake water.     

Adaptations of fleas (Siphonaptera) to parasitism

The paper deals with peculiarities of flea structure determined by their parasitism on mammals and birds. On the basis of the data on diversity of morphological characters, the leading role of structures of the frontal and nototrochanteral complexes in the adaptive evolution of Siphonaptera is substantiated. Peculiarities of the pulicoid, ischnopsylloid, palaeopsylloid, and generalized morphological types are analyzed together with examples of narrow morphological specializations. Distribution of fleas of these morphological types over five groups of hosts differing in the degree of mobility and association with nests and burrows is also analyzed.     

Separation of cat flea (Siphonaptera: Pulicidae) instars by individual rearing and head width measurements

Two methods to verify whether head width measurements fit Dyar's rule were evaluated for the separation of instars of the cat flea, Ctenocephalides felis (Bouché). Individual rearing was a reliable method of determining larval instar but was labor-intensive. The mean observed head widths were significantly different for each instar (first instar, 0.164 mm; second instar, 0.201 mm; third instar, 0.260 mm) and showed no sexual dimorphism. Head capsule width increased roughly 25% from instar to instar with geometrically progressing growth in accordance with Dyar's rule. However, head capsule width cannot be used to determine the instar of randomly selected larvae because the measurements overlap broadly between instars.     

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.