猫栉首蚤产卵与血便量的关系研究

在实验室控制条件下,分别以雌、雄大白鼠为供血动物饲养猫栉首蚤,收集并记录猫栉首蚤每日产卵量,同时用分光光度计测定血便排放量,分析产卵量与排血便量的关系。结果表明,猫栉首蚤的产卵历期平均57天,其中,雌鼠供血组每蚤平均一生产卵量为51．34-11粒,平均每天产卵0．94-0．2粒;雄鼠供血组每蚤平均一生产卵量为57．64-29粒,平均每天产卵1．04-0．5粒,两者产卵量无明显差异;同时猫栉首蚤的产卵量与产卵时间之间呈负相关,其中雌性大白鼠供血的决定系数为0．8002,雄性大白鼠供血的决定系数为0．5835。在一次大白鼠供血周期内,不同性别大白鼠供血时猫栉首蚤的产卵量和排血便量都呈现规律性变化,雌鼠供血组蚤的产卵量与产血便量呈双峰曲线,雄鼠供血组蚤的产卵量为单峰曲线。可见,在实验室控制条件下,猫栉首蚤产卵量与供血大白鼠的性别无关,不存在宿主性别依赖性。产卵量与血便量的变化呈正相关,反映了猫栉首蚤对宿主的适应性及选择宿主的特异性。     

Host specificity and foraging efficiency in blood-sucking parasite: feeding patterns of the flea<Emphasis Type="Italic"> Parapulex chephrenis</Emphasis> 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.     

Between-host phylogenetic distance and feeding efficiency in hematophagous ectoparasites: rodent fleas and a bat host

We hypothesized that a parasite exploits most effectively its principal host, less effectively a host that is phylogenetically close to its principal host, and least effectively a host that is phylogenetically distant from its principal host. We tested this hypothesis by quantifying the feeding efficiency of two flea species (Parapulex chephrenis and Xenopsylla ramesis) on two rodents, Acomys cahirinus, the specific host of P. chephrenis, and Meriones crassus, a preferred host of X. ramesis, and one bat, Rousettus aegyptiacus, an alien host to both flea species. In both fleas, fewer individuals succeed in feeding when offered with their nonspecific or nonpreferred rodent host to feed on compared with those allowed to feed on their preferred or specific rodent host or, surprisingly, on a bat. The proportion of P. chephrenis that fed was higher on A. cahirinus than on R. aegyptiacus. In contrast, similar proportions of X. ramesis took blood from M. crassus and R. aegyptiacus. The mass-independent size of the blood meal taken by the fleas differed significantly between species, being higher in X. ramesis than in P. chephrenis. However, each flea species took similar amounts of blood from any of the three host species. The duration of early, middle, and late digestion stages differed significantly between P. chephrenis and Xenopsylla conformis, all being shorter in the former, independent of the source of blood. Both fleas digested bat blood significantly faster than the blood of either rodent host. The time of survival after a single blood meal differed significantly between flea species, with X. ramesis surviving significantly longer than P. chephrenis, although no effect of host species on flea survival was found. In terms of the evaluation criteria that we used, we concluded that (a) the alien bat host appeared not to be inferior as a source of food to a rodent host phylogenetically close to the flea’s principal host and (b) that the rarity of finding rodent fleas on bats is not related to the feeding efficiency of the fleas.     

方形黄鼠蚤松江亚种和二齿新蚤存活力的对数线性回归模型

利用生存分析方法 ,建立了方形黄鼠蚤松江亚种和二齿新蚤新羽化蚤未吸血的雄蚤和雌蚤 ,吸 1次血的雄蚤和雌蚤 ,每日喂血 1h的雄蚤 ,每日喂血 1h的雌蚤的对数线性回归模型和危险率模型 ,得到如下结论。温度对两种蚤的生存影响大于湿度。危险率随着温度的增高而增大 ,随着湿度的增高而减小。在相同的温度湿度下 ,生存到某天的危险率随着吸血条件的改善而降低     

Effect of host gender on blood digestion in fleas: mediating role of environment

We investigated mechanisms of male-biased parasitism by studying the rate of digestion and survival time after a single blood meal in fleas Xenopsylla ramesis parasitizing males and females of the rodent Meriones crassus. Assuming that male hosts represent better patches for fleas than female hosts, we predicted that fleas (1) will digest blood of a male host faster than blood of a female host and (2) will survive longer after a single blood meal taken from a male host. To understand the possible role of environmental factors in mediation of the relationship between flea performance and host gender, we tested our predictions in male and female fleas under low (75%) and high (95%) relative humidity (RH). Host gender affected duration of digestion only at the middle and late stages of digestion and only interacting with either flea gender or RH or both. At the early stage of digestion, fleas of the same gender at the same RH digested blood at similar rates, independent of host gender. The rate of digestion did not differ between male and female fleas at 75% RH, but the duration of early stage was significantly shorter in female than in male fleas at 95% RH. At the middle stage of digestion, male fleas at both RH digested blood of male and female hosts at similar rates, but at lower RH, female fleas digested blood from male hosts at a significantly faster rate than blood from female hosts. At the late stage of digestion, both male and female fleas digested blood faster from male hosts than from female hosts at 75% RH, but the opposite was true at 95% RH. Survival time of fleas after completion of digestion was affected by RH, being longer at 95%, and flea gender, being longer in females. Fleas fed on female hosts died faster than fleas fed on male hosts, but this was found only at 95% humidity. We concluded that the relationship between flea performance and host gender was mediated by external conditions.     

Source of host blood affects prevalence of infection and bacterial loads of Yersinia pestis in fleas

Yersinia pestis, the etiological agent of plague, is transmitted by multiple flea species. Previous studies have reported wide variability in transmission efficiency among competent vectors. However, it is unclear to what extent such variation is explained by methodological differences among studies. To optimize an artificial feeding system where fleas are infected with controlled numbers of Y. pestis under standardized laboratory conditions that could be used to systematically compare vector efficiency, we sought to test the effect of host bloodmeal source on (1) the flea's ability to remain infected with Y. pestis and (2) bacterial loads in fleas. Here, we demonstrate that both prevalence of infection with a virulent strain of Y. pestis (CO96-3188) and bacterial loads in rock squirrel fleas (Oropsylla montana) are affected by host-associated blood factors. The generality of this observation was confirmed by repeating the study using the rat flea (Xenopsylla cheopis) and a commonly used avirulent laboratory strain of Y. pestis (A1122). Implications of the results for rate of spread of Y. pestis in naturally infected host populations are discussed.     

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.     

Early-phase transmission of Yersinia pestis by unblocked Xenopsylla cheopis (Siphonaptera: Pulicidae) is as efficient as transmission by blocked fleas

For almost a century, the oriental rat flea, Xenopsylla cheopis (Rothschild) (Siphonaptera: Pulicidae), was thought to be the most efficient vector of the plague bacterium Yersinia pestis (Yersin). Approximately 2 wk after consuming an infectious bloodmeal, a blockage often forms in the flea's proventriculus, which forces the flea to increase its biting frequency and consequently increases the likelihood of transmission. However, if fleas remain blocked and continue to feed, they usually die within 5 d of blocking, resulting in a short infectious window. Despite observations of X. cheopis transmitting Y. pestis shortly after pathogen acquisition, early-phase transmission (e.g., transmission 1-4 d postinfection [ p.i.]) by unblocked fleas was viewed as anomalous and thought to occur only by mass action. We used an artificial feeding system to infect colony-reared X. cheopis with a fully virulent strain of Y. pestis, and we evaluated transmission efficiency 1- 4 d p.i. We demonstrate 1) that a single infected and unblocked X. cheopis can infect a susceptible host as early as 1 d p.i., 2) the number of fleas per host required for unblocked fleas to drive a plague epizootic by early-phase transmission is within the flea infestation range observed in nature, and 3) early-phase transmission by unblocked fleas in the current study was at least as efficient as transmission by blocked fleas in a previously published study using the same colony of fleas and same bacterial strain. Furthermore, transmission efficiency seemed to remain constant until block formation, resulting in an infectious period considerably longer than previously thought.     

Evidence of horizontal transmission of feline leukemia virus by the cat flea (<Emphasis Type="Italic">Ctenocephalides felis</Emphasis>)

The feline leukemia virus (FeLV) is a naturally occurring and widespread retrovirus among domestic cats. The virus is mainly transmitted horizontally through saliva, blood and other body fluids by close contact between cats. Vectors other than cats, e.g. blood-sucking parasites, have not been reported. This study tested the vector potential of the cat flea (Ctenocephalides felis) for FeLV. In a first feeding, fleas were fed for 24 h with blood from a FeLV-infected cat with persistent viremia. FeLV could be detected in the fleas, as well as in their feces. Fleas were then divided in two populations and fed in a second feeding for 5 h or 24 h with non-infected non-viremic blood. FeLV was again detected in the fleas and their feces. In addition, the two resulting blood samples of the second feeding were subsequently tested for FeLV and both samples were positive for FeLV RNA. The cat flea transmitted the FeLV from one blood sample to another. In a third feeding, the same populations of fleas were fed again with non-infected blood for 5 h or 24 h. This time FeLV was not detected in the fleas, or in the feces or blood samples . Results show that cat fleas are potential vectors for FeLV RNA in vitro and probably also in vivo.     

Development of microsatellites for genetic analyses and population assignment of the cat flea (Siphonaptera: Pulicidae)

Cat fleas, Ctenocephalidesfelis (Bouché) (Siphonaptera: Pulicidae), are common ectoparasites of companion animals that negatively impact their hosts directly by causing dermatitis and blood loss during feeding and indirectly through the potential transmission of disease causing agents. We isolated and characterized seven novel microsatellite loci from a partial genomic library of the cat flea enriched for di-, tri-, and tetranucleotide repeats. We screened these loci in cat fleas from two laboratory colonies and one wild-caught population collected at a temporary animal shelter (Parker coliseum) in Baton Rouge, LA. Six loci were polymorphic, with two to 15 alleles per locus and an average observed heterozygosity of 0.21 across populations. Although the two laboratory cat flea colonies were isolated from each other for many years, they did not significantly differ in their genotypic composition. The cat flea population from Parker coliseum was genetically different from the laboratory colonies, but also showed high degrees of inbreeding. Multilocus genotypes of the polymorphic loci were sufficient to assign over 85% of cat fleas to their population of origin. Genetic markers for flea population identity will allow further studies to examine the origins and movement of cat fleas with important genetic traits such as insecticide resistance or pathogen susceptibility. The use of microsatellites also could determine if there are host-specific strains of cat fleas and add insight into the development of the different subspecies of C. felis.     

Effects of temperature on early-phase transmission of Yersina pestis by the flea, Xenopsylla cheopis

Sharp declines in human and animal cases of plague, caused by the bacterium Yersinia pestis (Yersin), have been observed when outbreaks coincide with hot weather. Failure of biofilm production, or blockage, to occur in the flea, as temperatures reach 30 degrees C has been suggested as an explanation for these declines. Recent work demonstrating efficient flea transmission during the first few days after fleas have taken an infectious blood meal, in the absence of blockage (e.g., early-phase transmission), however, has called this hypothesis into question. To explore the potential effects of temperature on early-phase transmission, we infected colony-reared Xenopsylla cheopis (Rothchild) fleas with a wild-type strain of plague bacteria using an artificial feeding system, and held groups of fleas at 10, 23, 27, and 30 degrees C. Naive Swiss Webster mice were exposed to fleas from each of these temperatures on days 1-4 postinfection, and monitored for signs of infection for 21 d. Temperature did not significantly influence the rates of transmission observed for fleas held at 23, 27, and 30 degrees C. Estimated per flea transmission efficiencies for these higher temperatures ranged from 2.32 to 4.96% (95% confidence interval [CI]: 0.96-8.74). In contrast, no transmission was observed in mice challenged by fleas held at 10 degrees C (per flea transmission efficiency estimates, 0-1.68%). These results suggest that declines in human and animal cases during hot weather are not related to changes in the abilities of X. cheopis fleas to transmit Y. pestis infections during the early-phase period. By contrast, transmission may be delayed or inhibited at low temperatures, indicating that epizootic spread of Y. pestis by X. cheopis via early-phase transmission is unlikely during colder periods of the year.     

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.     

Ectoparasite reproductive performance when host condition varies

Host condition can influence both the nutritive resources available to parasites and the strength of host defences. Since these factors are likely to be correlated, it is unclear whether parasites would be more successful on hosts in good, intermediate or poor conditions. For more complex parasites, like fleas, where larvae depend on adults to extract and make available some essential host resources, host condition can act at two levels. First, it can affect the investment of females into eggs, and second, it can influence offspring growth. In a two-step experiment, we first let female hen fleas Ceratophyllus gallinae feed on nestlings of reduced, control or enlarged great tit Parus major broods and secondly used the blood from these nestlings as a food source for flea larvae reared in the laboratory. We then assessed the effect of brood size manipulation on reproductive investment and survival of female fleas, and on survival, developmental time, mass and size of pre-imago larvae and adults of the first generation. Although host condition, measured as body mass controlled for body size, was significantly influenced by brood size manipulation, it did not affect the female fleas' reproductive investment and survival. Larvae fed with blood from nestlings of reduced broods lived longer, however, than larvae fed on blood from enlarged or control broods. Additionally, F1 adults grew shorter tibiae when their mother had fed on hosts of reduced broods. The finding that brood size manipulation influenced parasite reproduction suggests that it affected nutritive resources and/or host defence, but the precise mechanism or balance between the two requires further investigation.     

Monitoring of basophil sensitization to antigens of the cat flea (Ctenocephalides felis felis): a new tool for the diagnosis of feline flea bite hypersensitivity?

Suitability of blood basophils for in vitro diagnosis of flea allergy dermatitis (FAD) or flea bite hypersensitivity was studied in cats. A functional in vitro test (FIT) for sensitized type I allergic effector cells was used to evaluate the degree and kinetics of in vivo basophil sensitization against flea antigens in cats under long-term flea exposure. FIT results were compared with intradermal (IDT) and serological testing. Before, during, and after weekly repeated exposure to Ctenocephalides felis; 14 cats were repetitively FIT-assessed for general and flea-specific sensitization. In three cats, flea-specific sensitization was seen before and throughout flea exposure. Five cats, although generally sensitized, never developed a flea-specific sensitization. Six cats initially FIT-negative became sensitized for flea antigen during flea infestation. Induction, upregulation, and binding of C. felis-specific sensitizing antibodies to basophils during flea challenge may explain the developing sensitization in these cats. Strong discrepancies between the levels of flea-specific circulating IgE and basophil sensitization contrasted comparable results for basophil and mast cell sensitization using FIT and IDT, respectively. Hence, the FIT might provide an immunological supplement to the clinical diagnosis of FAD in cats by elucidating the state of basophil-sensitization to flea antigens. And it may be a comfortable alternative to IDT.     

Transmission of <Emphasis Type="Italic">Yersinia pestis</Emphasis> cultures with different plasmid content from <Emphasis Type="Italic">Xenopsylla cheopis</Emphasis> to <Emphasis Type="Italic">Calomys callosus</Emphasis>

Most Brazilian Yersinia pestis isolates display a typical plasmid profile composed of the three classical plasmids: pYV, pPst and pFra. However, some cultures lack at least one of these plasmids, while a few of them harbour atypical DNA bands of molecular weight ranging from 147 to 11.5 kb. To investigate whether Y. pestis displaying atypical plasmid content could be propagated among rodents in nature through flea bites, we carried out studies with fleas ( Xenopsylla cheopis) and rodents ( Calomys callosus) reared in the laboratory and five Y. pestis cultures differing in plasmid content. The results suggest that: (1) the single presence of pYV is not sufficient for the transmission of Y. pestis by fleas, (2) pPst is not essential for transmission, (3) two atypical DNA bands of molecular weight of 30 kb and >90 kb have no biological role, and (4) pFra is required for the transmission of Y. pestis by flea bites. Other studies are needed to determine whether this plasmid alone is sufficient for transmission.     

Population dynamics of adult fleas (Siphonaptera) on hosts and in nests of the California vole

Microtus californicus (Peale, 1848) were live trapped or retrapped 887 times, and fleas were collected over a 2.5-yr period in the San Francisco Watershed and Wildlife Refuge. Also, 179 M. californicus nests were collected monthly with observations to identify the environment of fleas. The ratio of the mean number of fleas per nest to the mean number collected on voles was 4.7:1 for Malaraeus telchinus (Rothschild, 1905), 13:1 for Hystrichopsylla occidentalis linsdalei Holland, 1957,9:1 for Atyphloceras multidentatus multidentatus (C. Fox, 1909), and 76:1 for Catallagia wymani (C. Fox, 1909). The proportion of each flea species per nest to those per host was not closely associated seasonally or spatially. The average nest contained 37.5% moisture content in relation to its total weight and ranged between 3 and 92%. No relationship was observed between relative humidity of air within nests and flea number, but a significant relationship existed between the moisture of nesting materials and flea number. Malaraeus telchinus and A. m. multidentatus were collected in greatest numbers from nests having 30-39% moisture content by weight, and H. o. linsdalei and C. wymani were most numerous in nests that had 40-49% moisture content. Catallagia wymani had the greatest tolerance for high moisture and was severely affected by lack of moisture and nearly absent in drier nests. No ectoparasites were collected from nests that had <12% moisture content, and nests with >50% moisture content had few fleas. A static concept of nest fleas and host fleas as suggested by averages and often used in literature is questionable. In seasonal comparison of populations of fleas on hosts and in nests, M. telchinus and H. o. linsdalei reversed so that more of the flea population was on the host than in the nest for a short time during fall.     

Studies on the growth of Bartonella henselae in the cat flea (Siphonaptera: Pulicidae)

Two out of three pools of cat fleas, Ctenocephalides felis (Bouche), that were fed Bartonella henselae-positive cat blood for 3 d and then bovine blood for 3 d, were polymerase chain reaction (PCR) positive for B. henselae. In a second experiment, three cats were inoculated with a streptomycin-resistant strain of B. henselae. After the cats were inoculated, caged cat fleas were fed on the cats during three different periods, and then pooled and transferred to noninfected recipient cats. In the first trial, the bacteria in the flea feces were below level of detection when the fleas were transferred from the infected cats to the recipient cat. After the fleas had fed on the recipient cat for 6 d, a bacteria level of 4.00 x 10(3) CFU/ mg was detected in the flea feces. Subsequently, the bacteria level increased for 4 d and then declined. In another experiment, the bacteria level in the flea feces was 1.80 x 10(3) CFU/mg at 2 h after collection and 3.33 x 10(2) CFU/mg at 72 h after collection. These data indicated that this strain of B. henselae can persist in flea feces in the environment for at least 3 d, and that B. henselae can multiply in the cat flea.     

Oral low-carbohydrate alcohol liquid diet induces experimental steatohepatitis in the rat

The intragastric tube feeding model of alcoholic liver disease in the rat induces significant liver histopathology, including steatohepatitis and fibrosis. The question is, if the same low-carbohydrate diet is fed ad lib, will the same pathology develop? Rats were fed a liquid diet with ethanol ad lib that was low in calories derived from carbohydrates for 2 months. The urinary ethanol levels (UALs) were monitored at hourly, daily, and weekly intervals, and the growth of the rats was charted. The liver histopathology and blood transaminase levels were determined. Rats fed ethanol grew 1 g/day, which was 2 g/day less than when they were fed the same diet intragastrically. UALs varied hourly between 150 and 500 mg%, daily between 120 and 360 mg%, and weekly between 0 and 500 mg%. Individual rat UALs showed no predictable pattern. The pair-fed controls ate all of their daily ration within 12 h, then fasted until the next day. The histopathology and blood alanine aminotransferase were similar to those seen with the intragastric tube feeding of the same diet, except that necrosis, inflammation, and fibrosis did not develop. The conclusion was that the oral feeding of a low-carbohydrate diet produces less liver injury than that produced by the same diet fed intragastrically. The UALs varied hourly, daily, and weekly in individual rats, making it difficult to synchronize UALs at the time of sacrifice.     

The Bartonella henselae SitABCD transporter is required for confronting oxidative stress during cell and flea invasion

Bartonella henselae is a zoonotic pathogen that possesses a flea–cat–flea transmission cycle and causes cat scratch disease in humans via cat scratches and bites. In order to establish infection, B. henselae must overcome oxidative stress damage produced by the mammalian host and arthropod vector. B. henselae encodes for putative Fe²⁺ and Mn²⁺ transporter SitABCD. In B. henselae, SitAB knockdown increases sensitivity to hydrogen peroxide. We consistently show that SitAB knockdown decreases the ability of B. henselae to survive in both human endothelial cells and cat fleas, thus demonstrating that the SitABCD transporter plays an important role during the B. henselae infection cycle.