SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Recent advances in our knowledge of cat flea biology and the discovery of new nontoxic control methods have greatly simplified and improved flea control. Instead of relying on adulticides for the bulk of flea control, the veterinarian now focuses on the immature stages, particularly the larvae and the eggs. By doing this, environmentally "friendly" flea control methods are employed that are much safer for the veterinarian, the pet owner, and the cat.
The efficacy of selamectin in the treatment and prevention of naturally acquired Toxocara canis infections and experimentally induced flea (Ctenocephalides felis felis) infestations in dams and their suckling pups was evaluated by administering selamectin to the adult females only, approximately 40 and 10 days before parturition and 10 and 40 days after parturition. Unit doses of the commercial formulation of selamectin were administered to the dams to provide at least the minimum recommended dosage of 6mgkg(-1) (range, 6-12mgkg(-1)). Dams and their pups were housed in carpeted environments able to support the flea life cycle. Flea infestations were established initially by experimental infestation before treatment administration and by repeated re-infestation of dams at approximately weekly intervals throughout the study, which was completed 45 days after parturition. There were no adverse drug experiences related to treatment with selamectin and no treatment-related mortalities. Percentage reductions in geometric mean T. canis faecal egg counts for the selamectin-treated dams, compared with those receiving the negative-control treatment (vehicle only) were 99.7% at the end of the study (P=0.0001). Geometric mean faecal egg counts in pups from selamectin-treated females were reduced by > or =96% on the 24th and 34th days after birth (P=0.0001), and the number of adult worms recovered from the gastrointestinal tract of pups from selamectin-treated dams was reduced by 98.2% (P=0.0001), compared with that for pups from dams treated with the vehicle only. Percentage reductions in geometric mean flea counts for selamectin-treated dams and their pups, compared with vehicle-treated dams and their pups, were > or =99.8% (P=0.0001) and 100% (P=0.0001), respectively, throughout the study. Thus, selamectin administered topically at a minimum unit dosage of 6mgkg(-1) to dams with naturally acquired T. canis infections and experimentally induced C. felis infestations was safe and highly effective in the treatment, control, and prevention of adult T. canis infection and C. felis infestation affecting both the dams and their pups.
An investigation was conducted into a severe flea infestation on dairy calves. Inspection of the dairy revealed a high infestation of Ctenocephalides felis felis on four calves and thousands of fleas in the stable where cows and calves were brought in for milking. A 3-month-old female calf was highly infested with fleas. The animal showed an evident lethargy, weight loss, as well as pale mucous membranes and dehydration. Hematological analysis revealed anemia, with 10% packed cell volume and a 1.72 x 10(6) microl(-1) erythrocyte count. Blood transfusions were performed and the flea infestation was controlled with 1% fipronil pour-on (1 ml/10 kg). The farmer was advised to treat the other calves with fipronil, remove the manure from the stable and spread 1% propoxur powder (100 g/m2) onto the floor of the stable.
BACKGROUND: Papular urticaria caused by flea bite presents clinical symptoms of hypersensitive reaction accompanied by skin lesions. Diagnostic and therapeutic approaches to the disease often go unrewarded, partly because of our incomplete understanding of the underlying immunopathogenesis. OBJECTIVE: To characterize the immune response to the flea bite in patients with papular urticaria. METHODS: This study included 45 randomly selected patients and 17 controls. Cutaneous allergy tests were performed. The histopathologic and immunohistochemical characteristics of cellular infiltrate in skin lesions were established. Immunoblot analysis was used to describe the specific characteristics of flea proteins recognized by IgE and IgG in patients' serum samples. RESULTS: Cutaneous allergy test results were negative in 87% to 98% of patients and in 88% to 100% of controls. Histopathologic and immunohistochemical studies revealed a predominance of eosinophils and CD4+ T lymphocytes. Immunoblotting did not show significant differences in IgG response between patients and controls. IgE recognition of flea proteins appears to decrease as the disease progresses. CONCLUSIONS: Our results suggest that the clinical manifestations of papular urticaria are mediated by a complex immune response involving more than one mechanism, with evidence forboth an IgE response and a cell-mediated type IV response.
Hosts exert selection pressures on their parasites and it is often assumed that host-parasite coevolution with each host is less intense in a generalist parasite than for a parasite with a narrow host range. Selection pressure on the parasite, however, is rather determined by host specificity, i.e. the relative importance of each host, than simply by the range of hosts. The determination of host specificity requires an assessment of the prevalence and intensity of parasite infestation within each host's nests, as well as the local abundance of each host species. Since the hen flea, Ceratophyllus gallinae, is a rather generalist parasite of birds it could be concluded that there has been weak coevolution with each of its hosts. By reviewing the literature on the prevalence and intensity of hen flea infestations in bird nests we estimated the number of individuals produced in the nest of each host species. The comparative analysis shows (1) that the prevalence of infestation is highest in hole-nesting avian families, (2) that prevalence and intensity of infestation among bird families are highly correlated, and (3) that hole-nesting Paridae have the highest intensities of infestation and harbour the majority of the flea population. These results underline the fleas' potential for coevolution with Paridae despite their extensive host range.
We studied the interaction between plants (horsenettle; Solanum carolinense) and herbivorous insects (flea beetles; Epitrix spp., and tobacco hornworm; Manduca sexta) by focusing on three questions: (1) Does variation in nitrogen availability affect leaf chemistry as predicted by the carbon-nutrient balance (CNB) hypothesis? (2) Does variation in plant treatment and leaf chemistry affect insect feeding? (3) Is there an interaction between the insect herbivores that is mediated by variation in leaf chemistry? For three successive years (1998-2001), we grew a set of clones of 10 maternal plants under two nitrogen treatments and two water treatments. For each plant in the summer of 2000, we assayed herbivory by hornworms in both indoor (detached leaf) and outdoor (attached leaf) assays, as well as ambient flea beetle damage. Estimates of leaf material consumed were made via analysis of digitized leaf images. We also assayed leaves for total protein, phenolic, and glycoalkaloid content, and for trypsin inhibitor, polyphenol oxidase, and peroxidase activity. Despite strong effects of nitrogen treatment on growth and reproduction, only total protein responded as predicted by CNB. Leaf phenolic levels were increased by nitrogen treatment, polyphenol oxidase activity was decreased, and other leaf parameters were unaffected. Neither hornworm nor flea beetle herbivory could be related to plant treatment or genotype or to variation in any of the six leaf chemical parameters. A negative relationship between flea beetle and hornworm herbivory was found, but was not apparently mediated by any of the measured leaf chemicals. Because leaf resistance was maintained in low nitrogen plants at the apparent expense of growth and reproduction, our results support the concept of a fitness cost of defense, as predicted by the optimal defense hypothesis.
The rate of development of immature fleas, Xenopsylla conformis Wagner and Xenopsylla ramesis Rothschild (Siphonaptera: Xenopsyllidae) was studied in the laboratory at 25 degrees C and 28 degrees C with 40, 55, 75 and 92% relative humidity (RH). These fleas are separately associated with the host jird Meriones crassus Sundevall in different microhabitats of the Ramon erosion cirque, Negev Highlands, Israel. This study of basic climatic factors in relation to flea bionomics provides the basis for ecological investigations to interpret reasons for paratopic local distributions of these two species of congeneric fleas on the same host. Both air temperature and RH were positively correlated with duration of egg and larval stages in both species. Change of humidity between egg and larval environments did not affect duration of larval development at any temperature. At each temperature and RH, the eggs and larvae of X. ramesis did not differ between males and females in the duration of their development, whereas female eggs and larvae of X. conformis usually developed significantly faster than those of males. For both species, male pupae developed slower than female pupae at the same air temperature and RH. Air temperature, but not RH, affected the duration of pupal development. At each humidity, duration of the pupal stage was significantly longer at 25 degrees C than at 28 degrees C: 15.3+/-1.7 vs. 11.7+/-1.2 days in X. conformis; 14.1+/-2.0 vs. 11.5+/-1.7 days in X. ramesis, with a significantly shorter pupal period of the latter species at 25 degrees C. These limited interspecific bionomic contrasts in relation to basic climatic factors appear insufficient to explain the differential habitat distributions of X. conformis and X. ramesis.
To investigate the persistence of flea larvicidal activity in the immediate environment of cats treated with imidacloprid, eggs of the cat flea Ctenocephalides felis felis Bouché (Siphonaptera: Pulicidae), from untreated donor cats, were incubated on samples of fleece blanket taken from the floor of cages used by treated or untreated cats for a total of 10 or 20 6-h periods over 2-4 weeks, respectively. Sufficient imidacloprid accumulated during these periods to reduce the emergence of adult fleas by 94.7-97.6% when the blankets were tested after 18 weeks' storage at room temperature. A typical laundry procedure (washing with detergent at 50 degrees C and low temperature tumble drying) removed this biological activity. Unwashed control blankets did not support the flea life-cycle as effectively as washed blankets or a sand substrate.
Yersinia pestis is transmitted by fleas and causes bubonic plague, characterized by severe local lymphadenitis that progresses rapidly to systemic infection and life-threatening septicemia. Here, we show that although flea-borne transmission usually leads to bubonic plague in mice, it can also lead to primary septicemic plague. However, intradermal injection of Y. pestis, commonly used to mimic transmission by fleabite, leads only to bubonic plague. A Y. pestis strain lacking the plasmid-encoded cell-surface plasminogen activator, which is avirulent by intradermal or s.c. injection, was able to cause fatal primary septicemic plague at low incidence, but not bubonic plague, when transmitted by fleas. The results clarify a long-standing uncertainty about the etiology of primary septicemic plague and support an evolutionary scenario in which plague first emerged as a flea-borne septicemic disease of limited transmissibility. Subsequent acquisition of the plasminogen activator gene by horizontal transfer enabled the bubonic form of disease and increased the potential for epidemic spread.
A statewide telephone survey of health symptoms associated with occupational exposure to flea control products among California pet handlers was conducted in 1987 following several reports of ill workers. The 696 employees interviewed worked at veterinary clinics, pet stores, pet boarding kennels, pet grooming shops, and animal control facilities. Symptom incidence and frequency and flea control product use were reported for the 3 months prior to interview. Eye and skin symptoms and unusual tiredness were elevated among workers who applied flea control products to animals or facilities. After adjustment for potential confounders, these symptoms were elevated 64% to 258% among applicators as compared to nonapplicators who worked in the same facilities. Workers who used protective clothing and equipment and followed some protective work practices were not at increased symptom risk. Some specific flea control active ingredients and application procedures were associated with respiratory effects and with symptoms suggesting systemic pesticide poisoning.
Yersinia pestis, the plague bacillus, has a plasminogen activator (pla) gene on the 9.5-kb plasmid pPla that is hypothesized to play a role in producing the foregut blockage in the flea vector that precedes transmission. In this study, however, Y. pestis that lacked pPla, the 70-kb virulence plasmid, or both plasmids, proved able to block Xenopsylla cheopis fleas normally. Blockage rates decreased with increasing environmental temperature for fleas infected with either wild type or pPla- Y. pestis. Thus, procoagulant ability of the Y. pestis pla gene product does not mediate blockage, nor does its ability to induce fibrinolysis at>28 degreesC account for failure to block at elevated temperatures. A Y. pestis strain that lacked all or part of the third plasmid of 110 kb, however, failed to colonize the flea midgut normally, indicating that one or more genes on the large plasmid may be required for vectorborne transmission.
Transmission of plague by fleas depends on infection of the proventricular valve in the insect's foregut by a dense aggregate of Yersinia pestis. Proventricular infection requires the Y. pestis hemin storage (hms) genes; here, we show that the hms genes are also required to produce an extracellular matrix and a biofilm in vitro, supporting the hypothesis that a transmissible infection in the flea depends on the development of a biofilm on the hydrophobic, acellular surface of spines that line the interior of the proventriculus. The development of biofilm and proventricular infection did not depend on the 3 Y. pestis quorum-sensing systems. The extracellular matrix enveloping the Y. pestis biofilm in the flea appeared to incorporate components from the flea's blood meal, and bacteria released from the biofilm were more resistant to human polymorphonuclear leukocytes than were in vitro-grown Y. pestis. Enabling arthropod-borne transmission represents a novel function of a bacterial biofilm.
Adult cat fleas, Ctenocephalides felis felis (Bouché), on cats (Felis catus) were exposed to emissions from an ultrasonic flea collar worn by the cat. No significant differences were found in total numbers of eggs produced per day (mean = 524 control, 614 treatment), in length of larval development time (mean = 7.7 d control, 7.7 d treatment), or in total daily pupal production (mean = 485 control, 445 treatment) between the treatment and the control groups. Tests off the host were conducted to determine whether ultrasonic exposure caused mortality in adult fleas; no significant differences were found in daily mortality between the treated and control fleas during 1 wk of exposure.
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.
The experimental drug CGA-184699 (N-[2,5-dichloro-4-(1,1,2,3,3,3-hexafluoropropoxy)-phenylaminoc arbonyl]-2,6-difluorobenzamide) was evaluated for efficacy against cat fleas, Ctenocephalides felis (Bouché), held in flea cages on cats. When administered orally, the compound acts systemically and prevents development of the next generation of fleas. There was no effect on adults, but eggs from adults that fed on treated cats had reduced viability. Most larvae that emerged from surviving eggs died. Within the first 2 wk after treatment of cats with CGA-184699, most death of progeny occurred in the egg stage, but as time passed, more eggs hatched but larval mortality prevented development to adults. A single oral dose of CGA-184699 virtually eliminated the next generation of adult fleas for a period of 44 d.
From April to October 1990, white-footed mice, Peromyscus leucopus (Rafinesque), were examined for ectoparasites on Long Point, Ontario, the only endemic area for Ixodes dammini Clifford, Spielman, Piesman & Corwin and Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner known in Canada. Larval and nymphal I. dammini and Dermacentor variabilis (Packard), and adult fleas Orchopeas leucopus (Baker), Epitedia wenmanni (Rothschild), and Ctenophthalamus pseudagrytes Baker were common on trapped mice. Questing ticks were collected by dragging, near the sites of mouse trapping, from April to November 1990. Indirect immunofluorescent assay established that 58.3% of adult, 17.3% of nymphal, and 0.15% of larval I. dammini questing at Long Point were infected with B. burgdorferi, indicating that infected mammalian reservoir hosts are common. None of 593 adult, 2 nymphal, and 4 larval D. variabilis collected while questing were infected; and only 1 of 322 fleas (O. leucopus) removed from white-footed mice was infected. The fact that no unfed adult D. variabilis and only one flea were infected, in a situation where the probability of exposure of hematophagous ectoparasites is moderately high, suggests that this species of tick and the fleas examined are poor vectors for the Lyme disease spirochete.
Previous laboratory studies have shown that inoculation of bacterial endotoxin into the hemocoel of some arthropods, or natural infection by a number of pathogens, causes them to seek out a higher ambient temperature. This phenomenon has been called behavioral fever. Yersinia pestis is an endotoxin-producing bacterium that relies on infection of fleas for transmission. Behavioral fever in fleas might enhance the transmission of plague if infected fleas were induced to seek out a warm-bodied host after the death of an infected host. Our study indicates that in thermal gradient Y. pestis infected Oriental rat fleas (Xenopsylla cheopis) do not exhibit behavioral fever and in one experiment sought out a significantly lower temperature.
Eight hundred and forty-nine and 1,503 Opisocrostis bruneri (Baker) were removed from Spermophilus franklinii (Sabine) in 1982 and 1983, respectively. Two discrete peaks in mean intensity of infestation were observed, one in early May and one in late August to early September. Overall prevalence of O. bruneri on S. franlinii was > or = 0.75. The observed biweekly prevalence on adult male and female squirrels was always > or = 0.73 and > or = 0.67, respectively. All juvenile squirrels were infested. Female fleas with undeveloped ovarioles, and with or without sperm in the spermatheca, were predominant during the first 6 wk that squirrels appeared above ground after hibernation. Parous females predominated thereafter. Peaks of nulliparous female fleas were observed in early May and early July. Female fleas were favored in each trapping period except during a 2-wk period from the beginning of May to the end of June. The mean biweekly sex ratio (male/female) of fleas removed from S. franklinii was 0.70 and 0.72 in 1982 and 1983, respectively. Oogenesis in O. bruneri was not dependent upon the estrous cycle of female S. franklinii. It appeared that O. bruneri completed at least two generations per year in Manitoba.