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PubMed1998

Feces, dead horses, and fleas. Evolution of the hostile use of biological agents.

Selected events in the history of biological weapons are highlighted to increase physicians' awareness of the threat of biological weapons. The hostile use of biological substances originated in antiquity and pervades the history of human conflict. Although difficult to verify at times, the use of such weaponry has not been limited to national militaries. Disgruntled civilians and even physicians have used biological weapons to promote their interests. Their potency, cost-effectiveness, and the ability to manufacture and deploy them with little sophistication, or under the semblance of legitimate commercial endeavors, will ensure that biological weapons remain a constant threat to public health.

Biological Warfare↗
PubMedDate not supplied

[Development of the preimaginal phases of the flea, Ctenophthalmus wladimiri Is.-Gurv., 1948].

The time required for the development and survival rate of preimaginal phases of C. wladimiri were studied. Experiments were conducted at a temperature from 0 degrees to 30 degrees C and relative air humidity from 60 to 100%. Temperatures between 18 degrees and 30 degrees C and humidity between 90 and 100% are most favourable for the complete developmental cycle of these insects; imagos hatched under these conditions accounted for 9 to 46% of eggs used in experiments.

Animals↗
PubMed2006

Relationship between host abundance and parasite distribution: inferring regulating mechanisms from census data.

1. We studied the effect of host abundance on parasite abundance and prevalence using data on 57 associations of fleas (Siphonaptera) and their mammalian hosts from Slovakia. 2. We assumed that flea-induced host mortality could be inferred from the relationship between flea aggregation and flea abundance, whereas host-induced flea mortality could be inferred from the relationship between flea abundance or aggregation and host abundance. 3. Relationships between flea abundance or prevalence and host abundance were either negative (in 23 flea-host associations) or absent (in 34 flea-host associations). Negative relationships between flea abundance and host abundance were always accompanied by negative relationships between flea prevalence and host abundance. 4. The link between flea abundance/prevalence and host abundance was evaluated as the coefficient of determination of the respective regressions. Across flea-host associations, this link decreased with an increase in the degree of flea aggregation (measured as a parameter b of Taylor's power law). 5. Mean crowding of fleas decreased with an increase of host abundance in eight flea-host associations, being asymptotic in four of them. On the other hand, mean crowding of fleas increased with an increase in flea abundance in 49 flea-host associations, being asymptotic in 15 of them. 6. Results of this study suggest that different flea-host associations are governed by different regulating mechanisms, but different regulation mechanisms may act simultaneously within the same flea-host associations.

Animals↗
PubMed2006

Biological, seasonal and environmental factors associated with Pulex irritans infestation of dairy goats in Greece.

The objectives of the present study were to study the fauna of fleas infesting dairy goats in Greece, the spectrum of hosts each flea species infests, identify risk factors in the environment, and goat management practices that favour flea infestation of goats, and describe the seasonal variation of infestation in goats. For this purpose, a total of 64 herds, with a history of flea infestation in goats, were visited during June and July of 2002 for data collection on flea burdens, species of fleas on goats, and other farm or pet animal species in the farm. Also data were collected on herd characteristics and management along with the flea infestation status of the village where it was located through a questionnaire survey. Data on elevation and climatic characteristics of the villages where the herds were located were also used in the study. All fleas collected from goats, sheep, pigs, and cattle were identified as being Pulex irritans. All fleas collected from cats were identified as being Ctenocephalides felis. Dogs were infested either with P. irritans, C. canis, or C. felis, or with both C. canis and C. felis. Kids had a significantly higher flea burden than goats and the Skopelos breed had the highest flea burden of all breeds followed in diminishing order by the breeds Capra prisca, Saanen cross mix, and Alpine cross mix (p < 0.05). The gender of the animal had no significant effect on flea burden. Factors significantly affecting the flea burden of goats were duration of flea infestation in the herd, type of flea control, and manure imported prior to the appearance of fleas in the herd (p < 0.05). The flea burden of goats was highest during summer and lowest during winter (p < 0.01), with complete an absence of infestation in January and February. Finally, a significant difference (p < 0.05) was found between the average annual temperature of villages with flea infestation (15.59 degrees C) and villages without flea infestation (17.14 degrees C). It was concluded that P. irritans was a true infestation of goats in Greece.

Age Factors↗
PubMed2006

Are ectoparasite communities structured? Species co-occurrence, temporal variation and null models.

1. We studied temporal variation in the structure of flea communities on small mammalian hosts from eastern Slovakia using null models. We asked (a) whether flea co-occurrences in infracommunities (in the individual hosts) in different hosts as well as in the component communities (in the host species) demonstrate a non-random pattern; (b) whether this pattern is indicative of either positive or negative flea species interactions; (c) whether this pattern varies temporally; and (d) whether the expression of this pattern is related to population size of either fleas or hosts or both. 2. We constructed a presence/absence matrix of flea species for each temporal sample of a host species and calculated four metrics of co-occurrence, namely the C-score, the number of checkerboard species pairs, the number of species combinations and the variance ratio (V-ratio). Then we compared these metrics with the respective indices calculated for 5000 null matrices that were assembled randomly using two algorithms, namely fixed-fixed (FF) and fixed-equiprobable (FE). 3. Most co-occurrence metrics calculated for real data did not differ significantly from the metrics calculated for simulated matrices using the FF algorithm. However, the indices observed for 42 of 75 presence/absence matrices differed significantly from the null expectations for the FE models. Non-randomness was detected mainly by the C-score and V-ratio metrics. In all cases, the direction of non-randomness was the same, namely the aggregation, not competition, of flea species in host individuals and host species. 4. The inclusion or exclusion of the uninfested hosts in the FE models did not affect the results for individual host species. However, exclusion of the uninfested host species led to the acceptance of the null hypothesis for only six of 13 temporal samples of the component flea communities for which non-randomness was detected when the uninfested hosts were included in the analysis. 5. In most host species, the absolute values of the standardized size effect of both the C-score and V-ratio increased with an increase in host density and a concomitant decrease in flea abundance and prevalence. 6. Results of this study demonstrated that (a) flea assemblages on small mammalian hosts were structured at some times, whereas they appeared to be randomly assembled at other times; (b) whenever non-randomness of flea co-occurrences was detected, it suggested aggregation but never segregation of flea species in host individuals or populations; and (c) the expression of structure in flea assemblages depended on the level of density of both fleas and hosts.

Animals↗
PubMed2006

Is abundance a species attribute? An example with haematophagous ectoparasites.

Population density is a fundamental property of a species and yet it varies among populations of the same species. The variation comes from the interplay between intrinsic features of a species that tend to produce repeatable density values across all populations of the same species and extrinsic environmental factors that differ among localities and thus tend to produce spatial variation in density. Is inter-population variation in density too large for density to be considered a true species character? We addressed this question using data on abundance (number of parasites per individual host, i.e. equivalent to density) of fleas ectoparasitic on small mammals. The data included samples of 548 flea populations, representing 145 flea species and obtained from 48 different geographical regions. Abundances of the same flea species on the same host species, but in different regions, were more similar to each other than expected by chance, and varied significantly among flea species, with 46% of the variation among samples accounted by differences between flea species. Thus, estimates of abundance are repeatable within the same flea species. The same repeatability was also observed, but to a lesser extent, across flea genera, tribes and subfamilies. Independently of the identity of the flea species, abundance values recorded on the same host species, or in the same geographical region, also showed significant statistical repeatability, though not nearly as strong as that associated with abundance values from the same flea species. There were also no strong indications that regional differences in abiotic variables were an important determinant of variation in abundance of a given flea species on a given host species. Abundance thus appears to be a true species trait in fleas, although it varies somewhat within bounds set by species-specific life history traits.

Animals↗
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.

Animals↗
PubMed2000

Evaluation of efficacy of selamectin and fipronil against Ctenocephalides felis in cats.

OBJECTIVE: To evaluate efficacy of monthly administration of selamectin and fipronil against Ctenocephalides felis in cats. DESIGN: Randomized controlled trial. ANIMALS: 36 healthy cats. PROCEDURE: Cats known to be free of fleas were infested with 100 unfed adult fleas on days -28 and -21. On days 0, 30, 60, 90, and 120, sixteen cats (8 pairs/treatment group) were treated by topical administration of selamectin (6 mg/kg [2.7 mg/lb] of body weight) or fipronil (7.5 mg/kg [3.4 mg/lb]). Four control cats (2 pairs) were not treated. On day -6 and every 2 weeks after initial treatment, comb counts were performed to detect fleas. Flea counts were recorded, and fleas (< or =50) that had been removed were replaced onto the cat. On day 89, fleas were not replaced. On day 91 and every 7 days until the end of the study (day 150), cats were challenged with 20 adult fleas. Flea counts were compared between and within treatments. RESULTS: 14 days after treatment, geometric mean flea counts were reduced by 71.2% by fipronil treatment and 35.3% by selamectin treatment. Both treatments resulted in 97 to 98% reduction in flea counts on day 29 and 99.8 to 100% reduction from day 44 to the end of the study. CONCLUSIONS AND CLINICAL RELEVANCE: Selamectin is as effective as fipronil in treating infestation in cats housed for 3 months in a flea-infested environment under conditions known to support the flea life cycle and in protecting against subsequent weekly challenges with C felis for an additional 2 months.

Administration, Topical↗
PubMed1994

Comparison of thumb-counting and comb-counting methods to determine Ctenocephalides felis infestation levels on dogs.

Comb-counting and thumb-counting were compared in a cross-over study to determine which was more accurate for quantifying flea infestation levels on dogs. Twenty beagle dogs were used in the study and infested with either 50 or 100 adult fleas (Ctenocephalides felis). Two groups of five dogs each were infested with either 50 or 100 fleas per dog, and then comb-counted with a fine-toothed flea comb for 8 min periods. An additional two groups of five dogs each were also given 50 or 100 fleas, and then thumb-counted. The counting time for this technique is both lower and more variable because the fleas are only observed and not captured; thus, the speed at which the dog is covered must be increased in order to prevent counting the same fleas more than once. The mean time of thumb-counting per dog was 3.2 min. Fleas removed during comb-counting were placed back on the dog they were taken from after the count was concluded. At the cross-over point, the ten dogs that had been comb-counted were then thumb-counted and the ten dogs that had been thumb-counted were comb-counted. The results showed that comb-counting recovered significantly (P < or = 0.05) more fleas than did thumb-counting. On dogs given 50 and 100 fleas, comb-counting gave mean percentage recoveries of 67.6% and 75.4%, respectively, whereas thumb-counting found means of 8.8% and 7.7%, respectively. The order in which the counting methods were employed produced no significant effect (P > 0.05) on the number of fleas counted.

Animals↗
PubMed1998

Effects of azadirachtin on Ctenocephalides felis in the dog and the cat.

Azadirachtin-containing neem seed extract is a powerful insect growth regulator, a feeding deterrent and repellent with low toxicity. Unfortunately, azadirachtin degrades rapidly in light, excessive heat or alkalinity. Evaluations of azadirachtin on ectoparasites on animals have been scarce. The purpose of this work was to describe the effects of normal and potentiated azadirachtin on Ctenocephalides felis in the dog or cat. Groups of kennelled greyhounds and domestic cats infested with C. felis were sprayed once with azadirachtin containing neem seed extract with or without diethyltoluamide (Deet) and/or citronella. Methanolic extracts with 200, 1000 or 2400 ppm azadirachtin reduced fleas in a dose-dependent manner. Compared with fleas counted on treated dogs just before treatment and untreated infested dogs, 1000-2400 ppm azadirachtin reduced fleas 93-53% for 19 days. However, combined with 500 ppm Deet and 33% w/v citronella, only 500 ppm azadirachtin reduced fleas 95-62% for 20 days. On cats inoculated with 50 fleas 2 days before treatment, the combination reduced fleas and eggs 100% to day 6 and 83-51% from day 7 to 9. On petri dishes, the combination achieved 100% egg mortality up to day 7 and 80% to day 14 and 48-52% to days 21-28. Deet, with or without neem seed extract or citronella, and citronella, with or without neem, did not reduce fleas significantly. The results show that azadirachtin reduced fleas in a dose-dependent manner in flea-contaminated environments. In cats, the combination killed most fleas within 24 h, providing effective flea control for 7 days. The results suggest that Deet with citronella potentiated the effect of azadirachtin on C. felis.

Animals↗
PubMed1997

Use of injectable lufenuron for treatment of infestations of Ctenocephalides felis in cats.

OBJECTIVE: To determine whether and for how long a single dose of a new injectable formulation of lufenuron would successfully control experimentally induced Ctenocephalides felis infestations in cats. ANIMALS: 15 cats (3 groups of 5). PROCEDURE: Each group of cats was housed in a separate room. Each cat was infested with 150 fleas, and flea counts were checked weekly. Once flea populations had stabilized, cats were treated with lufenuron at a dosage of 5 mg/kg of body weight, s.c. (group 1) or 10 mg/kg, s.c. (group 2). Group-3 cats were not treated. Flea counts were checked weekly for 18 weeks, and effectiveness was determined by comparing flea counts for treated cats with flea counts for control cats. Cats were reinfested with fleas during weeks 19, 26, 36, and 49, and flea counts were again determined weekly. RESULTS: Effectiveness for both dosages of lufenuron was > 90% by 5 weeks after treatment, > 95% by 9 weeks after treatment, and > 98% by 13 weeks after treatment. Reinfestations performed during weeks 19 and 26 were well controlled (ie, > 90% reduction in flea counts, compared with control group) in both groups of cats treated with lufenuron. Reinfestations performed during week 36 were well controlled only in cats treated with lufenuron at the higher dosage. Reinfestations performed during week 49 were not controlled in either group of treated cats. CONCLUSIONS: A single dose of the new injectable formulation of lufenuron should control flea populations in cats for up to 26 weeks, even among cats that are periodically reinfested with fleas.

Animals↗