Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil: I. Natural history of tungiasis in man

Tungiasis is an important health problem in poor communities in Brazil and is associated with severe morbidity, particularly in children. The causative agent, the female flea Tunga penetrans, burrows into the skin of its host, where it develops, produces eggs and eventually dies. From the beginning of the penetration to the elimination of the carcass of the ectoparasite by skin repair mechanisms, the whole process takes 4-6 weeks. The present study is based on specimens from 86 patients, for some of whom the exact time of penetration was known. Lesions were photographed, described in detail and biopsied. Biopsies were examined histologically and by means of scanning electron microscopy (SEM). Based on clinical, SEM and histological findings, the "Fortaleza classification" was elaborated. This allows the natural history of tungiasis to be divided into five stages: (1) the penetration phase, (2) the phase of beginning hypertrophy, (3) the white halo phase, (4) the involution phase and (5) residues in the host's skin. Based on morphological and functional criteria, stages 3 and 4 are divided into further substages. The proposed Fortaleza classification can be used for clinical and epidemiological purposes. It allows a more precise diagnosis, enables the assessment of chemotherapeutic approaches and helps to evaluate control measures at the community level.

Effect of air temperature and humidity on the survival of pre-imaginal stages of two flea species (Siphonaptera: Pulicidae)

The survival of immatture fleas at 25 and 28 degrees C and 40, 55, 75, and 92% RH was studied to test the hypothesis that the difference in microclimatic preferences determines habitat distribution of Xenopsylla conformis Wagner, 1903 and Xenopsylla ramesis Rothschild, 1904. Survival of X. conformis eggs did not depend on either temperature or humidity or both, whereas eggs of X. ramesis survived significantly less at 40% RH than at higher humidities. No larva of either species survived at 40% RH at either temperature. Larval survival of both species at both temperature regimes was significantly lower at 55% humidity than at higher humidities. Maximal survival time of larvae that died before pupation depended on both temperature and humidity in both species. Change of humidity during early stages of the life cycle (from egg to larva) increased the maximal survival time in X. conformis larvae but decreased that in X. ramesis larvae. Pupal survival was higher at higher humidities independent of temperature. Survival of X. conformis pupae was lower than that of X. ramesis pupae when the relative humidity was low. Humidity change on later stages (from larva to cocoon) decreased X. conformis pupal survival and had no effect on X. ramesis pupal survival. The sex ratio of emerged adults was not affected by either temperature or humidity in both species. Changes in humidity between egg and larval emvironments significantly decreased the percentage of females in X. conformis emergence at 28 degrees C.

Incidence of plague associated with increased winter-spring precipitation in New Mexico

Plague occurs episodically in many parts of the world, and some outbreaks appear to be related to increased abundance of rodents and other mammals that serve as hosts for vector fleas. Climate dynamics may influence the abundance of both fleas and mammals, thereby having an indirect effect on human plague incidence. An understanding of the relationship between climate and plague could be useful in predicting periods of increased risk of plague transmission. In this study, we used correlation analyses of 215 human cases of plague in relation to precipitation records from 1948 to 1996 in areas of New Mexico with history of human plague cases (38 cities, towns, and villages). We conducted analyses using 3 spatial scales: global (El Niño-Southern Oscillation Indices [SOI]); regional (pooled state-wide precipitation averages); and local (precipitation data from weather stations near plague case sites). We found that human plague cases in New Mexico occurred more frequently following winter-spring periods (October to May) with above-average precipitation (mean plague years = 113% of normal rain/ snowfall), resulting in 60% more cases of plague in humans following wet versus dry winter-spring periods. However, we obtained significant results at local level only; regional state-wide precipitation averages and SOI values exhibited no significant correlations to incidence of human plague cases. These results are consistent with our hypothesis of a trophic cascade in which increased winter-spring precipitation enhances small mammal food resource productivity (plants and insects), leading to an increase in the abundance of plague hosts. In addition, moister climate conditions may act to promote flea survival and reproduction, also enhancing plague transmission. Finally, the result that the number of human plague cases in New Mexico was positively associated with higher than normal winter-spring precipitation at a local scale can be used by physicians and public health personnel to identify and predict periods of increased risk of plague transmission to humans.

The cat flea: biology, ecology and control

Control failures and recurrences of infestation of dogs, cats and their home environment with the cat flea, Ctenocephalides felis felis are common. Attempts to control these infestations are often impaired by an inadequate understanding of the interaction of the cat flea with its hosts and environment. This review presents information on the medical and veterinary importance of the cat flea and discusses recent information on the environmental and host factors that affect its development and survival. Additionally, information is presented on the use and effectiveness of various insecticides and insect growth regulators against the four life stages.

Evaluation of the role of the Yersinia pestis plasminogen activator and other plasmid-encoded factors in temperature-dependent blockage of the flea

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.

Development rates of two Xenopsylla flea species in relation to air temperature and humidity

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.

Is sex-biased ectoparasitism related to sexual size dimorphism in small mammals of Central Europe?

Sexual size dimorphism (SSD) in mammals reveals the extent of sexual selection, which may in turn explain why males are often more infected by parasites than females and that parasites may contribute to the association between SSD and male-biased mortality. Here, we investigated the relationship between SSD in small mammals of Central Europe and the differences in sex infection by fleas. A comparative analysis was conducted for 10 species of rodents and insectivores. We found that males harbour higher flea species richness than females and that the abundance of fleas is higher in males than in females. This difference is not related to male-biased density. However, contrary to our hypothesis, we found that an increase in SSD is not related to an increase in male infection by fleas compared with female infection. We discuss our results in term of sex-differences in immunocompetence and/or sex-differences in behaviour.

Treatment of black-tailed prairie dog burrows with deltamethrin to control fleas (Insecta: Siphonaptera) and plague

Burrows within black-tailed prairie dog (Cynomys ludovicianus) colonies on the Rocky Mountain Arsenal National Wildlife Refuge, Colorado, were dusted with deltamethrin insecticide to reduce flea (Insecta: Siphonaptera) abundance. Flea populations were monitored pre- and posttreatment by combing prairie dogs and collecting fleas from burrows. A single application of deltamethrin significantly reduced populations of the plague vector Oropsylla hirsuta, and other flea species on prairie dogs and in prairie dog burrows for at least 84 d. A plague epizootic on the Rocky Mountain Arsenal National Wildlife Refuge caused high mortality of prairie dogs on some untreated colonies, but did not appear to affect nearby colonies dusted with deltamethrin.

Résumé of the Siphonaptera (Insecta) of the world

The world fauna of the order Siphonaptera is reviewed with respect to undescribed taxa, endangered species, taxonomic specialists, developmental stages, ultrastructure, taxonomic characters, host specificity, literature, fossil record, and the phylogenetic affinities of and within the order. The 15 currently recognized families are discussed with respect to their subfamilial, tribal, and generic classification. The numbers of species in these taxa are discussed and their general distribution and host preferences are briefly outlined. The current numbers of tribes, genera, and species, including invalid names, are listed.

Studies of vector competency and efficiency of North American fleas for Yersinia pestis: state of the field and future research needs

The etiological agent of plague, Yersinia pestis, is most commonly transmitted by the bite of infectious fleas. To date, at least 28 flea species occurring in North America have been experimentally confirmed as vectors of Y. pestis. Transmission efficiency differs among species and also between different studies of a single species. These differences may, however, in large part reflect nonstandardized experimental conditions used during the first half of the 20th century when such studies were conducted in response to the rapid spread of Y. pestis across the western United States after its introduction at the beginning of this century. The majority of these early transmission studies focused on the blocked flea mechanism of transmission, which typically does not occur until > 2-3 wk after the flea becomes infected. Recent studies have challenged the paradigm that Y. pestis is usually spread by blocked fleas by demonstrating that numerous flea species, including the oriental rat flea Xenopsylla cheopis, which was the focus of the early classical studies on blocked flea transmission, are capable of"early-phase" transmission during the first few days after becoming infected and before a complete blockage can form. The aims of this review are to 1) summarize Y. pestis vector competency and efficiency studies for fleas occurring in North America, 2) discuss the implications of the results of these studies for our understanding of the dynamics of plague epizootics, 3) demonstrate why older transmission studies need to be repeated using a standardized experimental system, and 4) outline future directions for studies of fleas as vectors of Y. pestis.

Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil: IV. Clinical and histopathology

Tungiasis is a parasitic skin disease caused by the sand flea Tunga penetrans. This ectoparasitosis is endemic in South America, the Caribbean and sub-Saharan Africa, where it is an important but neglected health problem in resource-poor communities. As part of a study of tungiasis-related morbidity in a typical slum in Fortaleza, Brazil, we identified 86 individuals with tungiasis. Lesions were counted, classified according to the stage of development, and clinical pathology was documented. One hundred and nine lesions were biopsied and examined by histological sectioning. The patients had between 1 and 145 lesions (median 14.5), the majority occurring in clusters. In all, 77% of patients reported severe pain at the site of the lesion, and 52% had one or more nails lost or severely deformed. Intense inflammation and/or fissures hindered 45% of the patients from walking normally. Signs of superinfection were observed in 29%, and signs of generalized inflammation in 2% of patients. Clinical pathology was significantly related to the number of lesions, and the total number of parasites present correlated with the number of fleas occurring in clusters. Clinical pathology was frequently accompanied by a pathological alteration of the epidermis (predominantly hyperplasia, parakeratosis, hyperkeratosis, and spongiosis) and the dermis. Tungiasis causes a broad spectrum of clinical histopathological alterations, and is a serious health threat in a typical, impoverished community in northeast Brazil. The clinical pathology is closely related to the parasite burden of an individual and the clustering of embedded fleas at certain predilection sites.

Host association, on-host longevity and egg production of Ctenocephalides felis felis

Host association, on-host longevity and egg production of Ctenocephalides felis felis (Bouché) were evaluated using fleas from a commercial laboratory colony and first generation, laboratory-reared, native Indiana fleas. Fleas were placed on cats that were declawed, fitted with Elizabethan collars and housed in specially designed metabolic cages. An average of 85% of the female and 58% of the male fleas stayed continuously on the cats for at least 50 days, indicating that the cat flea is a permanent ectoparasite. The maximum longevity of the cat flea was not determined, but it was shown that it can survive and reproduce on the cat for at least 113 days. A female cat flea may produce up to 1745 eggs during a 50-day period.

Density-dependent host selection in ectoparasites: an application of isodar theory to fleas parasitizing rodents

Parasites should make the same decisions that every animal makes regarding fitness reward. They can maximize reproductive success by selection of those habitats that guarantee the greatest fitness output. We consider the host population as a habitat of a parasite population. Consequently, hosts (=habitats) that differ quantitatively or qualitatively will support different numbers of parasites. The nature of habitat selection can be detected by isodars, lines along which habitat selection yields equivalent fitness reward. We applied this approach to study host selection of five fleas, each infesting two desert rodents. Xenopsylla conformis, Xenopsylla ramesis, Nosopsyllus iranus theodori and Stenoponia tripectinata medialis parasitize Gerbillus dasyurus and Meriones crassus. Synosternus cleopatrae pyramidis parasitizes Gerbillus andersoni allenbyi and Gerbillus pyramidum. Three fleas ( X. conformis, X. ramesis and S. c. pyramidis) were able to perceive quantitative (amount of the resource; e.g. organic matter in the nest for flea larvae) and/or qualitative (pattern of resource acquisition; e.g. host defensiveness) differences between hosts. Two other fleas did not perceive between-host differences. X. conformis was a density-dependent host selector that showed sharp selectivity at low density. X. ramesis and S. c. pyramidis were density-independent host selectors with a direct correspondence of density with habitat quality. N. i. theodori and S. t. medialis were non-selectors with no relationship at all between density and host quality. The results of the application of the isodar theory suggest that ectoparasites, like other animals, behave as if they are able to make choices and decisions that favour environments in which their reproductive benefit is maximized.

Epifaunistic arthropod parasites of the four-striped mouse, Rhabdomys pumilio, in the Western Cape Province, South Africa

Flea, lice, mite, and tick species associated with 510 Rhabdomys pumilio were collected at 9 localities in the Western Cape Province, South Africa. The aims of the study were first to quantify the species richness, prevalence, and relative mean intensity of infestation of epifaunistic arthropod species associated with R. pumilio, and second to determine temporal variations in the mean abundance of the parasitic arthropods. Each mouse was examined under a stereoscopic microscope and its parasites were removed, identified, and quantified. The epifaunal population was made up of more than 25,000 individuals and included 8 flea, 1 sucking louse, 11 mite, and 13 ixodid tick species. Female-biased sex ratios were noted for 9 (30%) of the ectoparasite species. Three undescribed mite and 1 undescribed tick species were recovered, and new locality records for 2 flea, the louse, and 2 mite species were documented. A phoretic host association between a nonparasitic mite species, Psylloglyphus uilenbergi kivuensis, and 3 flea species, Chiastopsylla rossi, Hypsophthalmus temporis, and Listropsylla agrippinae, was recorded. The mean abundance of the parasitic mite and insect species were higher during the cold wet season, whereas ticks were more numerous during the warm dry months. The large number of ectoparasite species on R. pumilio, a locally abundant and regionally widespread species, is of medical and veterinary importance particularly in relation to the transmission of pathogens such as Anaplasma marginale, Babesia caballi, and Babesia canis to domestic animals; Rickettsia conori; Yersinia pestis; and the viral disease Crimean-Congo hemorrhagic fever to humans.

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.

A plant-based repellent protects against Tunga penetrans infestation and sand flea disease

Tungiasis is a parasitic skin disease prevalent in impoverished populations in the tropics and associated with considerable morbidity. Treatment options are limited and prophylaxis has never been attempted. We assessed the effectiveness of a plant-based repellent to prevent infestation with Tunga penetrans and sand flea disease in an urban squatter settlement in Fortaleza, Northeast Brazil. Two cohorts were formed. One cohort started with the intervention while another served as control. The plant-based repellent Zanzarin was applied twice daily on the skin of the feet. After 4 weeks and a wash-out-phase of another 2 weeks, cross-over was performed. Study members were examined twice per week for the presence of newly embedded sand fleas. The number of viable and dead sand fleas and the total number of sand flea lesions were determined. Sentinel rats were used to assess local transmission dynamics. Outcome measures were the number of newly embedded sand fleas per individual per day, number of sand flea lesions per individual according to the stage, as well as type and degree of clinical pathology. Zanzarin applied twice daily on the feet reduced the number of newly embedded fleas by 92% (interquartile range 81-100%), the total number of lesions by 87% (81-98%) and reversed tungiasis-associated clinical pathology almost completely. In conclusion, in a setting in which tungiasis is an important health threat, the daily application of a plant-based repellent prevented the infestation with T. penetrans and sand flea disease.

Ectoparasite infestations of red foxes (Vulpes vulpes) in Hungary

A survey was carried out to investigate the ectoparasite infestations of 100 red foxes (Vulpes vulpes) in Hungary. The overall prevalence of flea and tick infestation was high (62 and 86% with the dominance of the anthropophil Pulex irritans and Ixodes ricinus), but the number of parasites was low to moderate. Felicola vulpis was not found in the present study, and the prevalence of Otodectes cynotis was only 2%. Based on prevalence (21%), mange lesion scores, and the negative correlation between lesion scores and condition of foxes, Sarcoptes infestation should be considered as the most important parasitosis of foxes in Hungary. Besides the ecological significance of these parasites, the high overall prevalence of mange and anthropophil flea and tick infestations of foxes and the appearance of these animals in the synanthropic environment as a result of the increasing population size, may result in the increasing incidence of flea, tick and accidental mite infestation of man and domestic animals, and may enhance the transmission rate of some vector-borne diseases.

Investigations on the life cycle and morphology of Tunga penetrans in Brazil

In the present study, the life cycle of Tunga penetrans was established in Wistar rats in the laboratory, and the morphology of the resulting developmental stages was studied by means of light and scanning electron microscopy. It was seen that the females enter at a nonfertilized stage through the skin of their hosts. Only there the copulation occurs, while females and males brought together in a Petri dish showed no interest in each other. In any way -- fertilized or not -- the females start about 6 days after penetration and hypertrophy with the ejection of eggs. While fertilized eggs proceed to development, the unfertilized ones remain arrested. The eggs are ovoid and measure about 600 x 320 mum. The larvae hatch from the eggs 1-6 days (mean 3-4) after ejection. Formation of larvae 2 took at least another day, while 4 up to 10 days more were needed until this larva starts pupation (mean 5-7 days). The formation of the adult fleas inside the puparium occurred within 9-15 days (with a maximum hatch at day 12). Adult female fleas having reached the skin of a host start blood sucking within 5 min and prepare to enter the skin. After 24 h, the flea stacked already with two thirds of its body inside the skin. After 40 h, the penetration was completed, and feeding and hypertrophical enlargement started, which was completed on day 6, when eggs became ejected. When studying the morphology of the fleas obtained from different hosts, slight variations were seen, which, however, are not significant for a species separation but may be an indication of the presence of different strains/races or the beginning of such a formation.

Ectoparasitic species from Canis familiaris (Linné) in Buenos Aires province, Argentina

Several arthropods that live as ectoparasites on domestic dogs can cause severe dermatitis or act as vectors of pathogenic agents, resulting in serious diseases not only in dogs, but also in humans. We studied ectoparasites found on Canis familiaris sampled in five areas in Buenos Aires province, Argentina. The prevalence of fleas, ticks and lice was analyzed, as well as their seasonal variations through the different sites studied. The kind of infestation found in each host was determined and the intensity of natural infestation was estimated. The study was carried out from October 2001 to July 2002, with 116 dogs that lived in rural areas and did not receive control treatments. In order to remove the ectoparasites, the dogs' skin was rubbed with a piece of cotton soaked in ether. All dogs had at least one species of ectoparasites. A total number of 5193 ectoparasites were found corresponding to four species, 15.7% Ctenocephalides canis, 73% Rhipicephalus sanguineus, 1.8 Linognathus setosus and 9.4% Heterodoxus spiniger. R. sanguineus was the most abundant species, and C. canis was the only flea species found. This may be due to the dogs being exclusively rural animals. Within the zones sampled, Magdalena showed the greatest prevalence, maybe as a consequence of having the highest relative humidity in relation to the other areas. Triple infestation (ticks-fleas-lice) was observed in 56.9% of the dogs; 39.6% presented double infestation, most being ticks-fleas, and only 3.4% showed simple infestation (lice). Female hosts were the most affected. Even though there were records of ectoparasites throughout all the year, a higher intensity was observed during the spring months, most likely as a result of the increase in temperature after the winter months.

Age, intensity of infestation by flea parasites and body mass loss in a rodent host

Parasitism by the flea Synosternus cleopatrae does not affect the body mass of its principal rodent host, Gerbillus andersoni under natural infestation levels. We hypothesized that the lack of negative effects of flea parasitism on rodent body mass could be related either to the low level of natural infestation or to the differential susceptibility of rodent age cohorts to flea parasitism. We tested these hypotheses by measuring body mass change under flea parasitism in (a) adult rodents infested with fleas above the natural infestation level (the first hypothesis) and (b) juvenile rodents infested with fleas at natural infestation levels (the second hypothesis). Adult individuals parasitized by a number of fleas higher than in nature lost body mass at higher rates than non-parasitized control individuals. Parasitism significantly affected daily body mass change of juvenile gerbils. Juvenile rodents parasitized by fleas at the natural level of infestation lost body mass faster and gained body mass slower than control animals. We suggest that some regulating mechanisms may limit natural flea densities at a point at which the negative effect on hosts is below the accuracy of our measurements. However, natural flea densities are sufficiently high to harm the more susceptible, juvenile cohort.

Efficacy of fipronil/(S)-methoprene combination spot-on for dogs against shed eggs, emerging and existing adult cat fleas (Ctenocephalides felis, Bouché)

The inhibitory activities of fipronil (10% (w/v) solution), (S)-methoprene (9% (w/v) solution), and fipronil/(S)-methoprene (10 and 9% (w/v) solution, respectively) combination against eggs and emerging adult cat fleas (Ctenocephalides felis) and adulticidal activity were tested on experimentally infested dogs. Thirty-two Beagle dogs were selected for this study and eight replicates of four animals were formed based on body weight within sex. One dog in each replicate was randomly allocated to treatment with: (1) untreated control; (2) fipronil 10% (w/v) solution, (3) (S)-methoprene 9% (w/v) solution, and (4) fipronil 10% (w/v) and (S)-methoprene 9% (w/v) combination solution. Treatments were applied once topically on Day 0 at the rate of 0.067 ml/kg. On Days -12, -1, 21, and weekly to Day 84 each dog was infested with approximately 200 fleas and comb counted approximately 24h later, or 2 days (our 48 h) after in the case of Day -1 infestation. On Days -11, 1, 22, and weekly to Day 85 each dog was again infested with approximately 200 fleas. Flea eggs were collected over approximately 24 h beginning 3 days after infestation. Fleas were combed off of the dogs and counted at the end of the egg collection period (approximately 96 h count). One aliquot of up to about 100 eggs, if available, from each animal at each infestation time was incubated for approximately 72 h to determine larval hatch and the other for 35 days to determine the number of adults that developed. The 10% (w/v) fipronil spot-on provided excellent control (>95%) of adult fleas on dogs for 5 weeks. Similarly, the combination spot-on of 10% (w/v) fipronil and 9% (w/v) (S)-methoprene provided excellent control of adult fleas, i.e., >95% for 5 weeks. From week 6 post-treatment onward, the relatively low inhibition of adult flea emergence substantiated the lack of significant ovicidal/larvicidal activity in the fipronil (10%, w/v) treatment group. However, the combination product provided excellent (>90%) ovicidal activity for 8 weeks and high (91.4%) inhibition of adult flea emergence for 12 weeks. In addition, a synergistic effect of the two compounds in combination was demonstrated with fipronil enhancing the ovicidal and inhibition of adult flea emergence activity of (S)-methoprene against cat flea eggs. When all stages of the life cycle of the cat flea are considered, the combination spot-on product provided a high level of total flea control yielding a curative effect against adult fleas and inhibition of flea development stages with little to no potential reinfestation pressure on the animal or in the environment for 12 weeks.

ECTOPARASITES IN AN URBAN POPULATION OF BIG BROWN BATS (EPTESICUS FUSCUS) IN COLORADO

Ectoparasites of an urban population of big brown bats (Eptesicus fuscus) in Fort Collins, Colorado, were investigated during summers 2002, 2003, and 2004. Eleven species of ectoparasites were found (the macronyssid mite Steatonyssus occidentalis, the wing mite Spinturnix bakeri, the myobiid mites Acanthophthirius caudata and Pteracarus aculeus, the chirodiscid mite Alabidocarpus eptesicus, the demodicid mite Demodex sp., the chigger Leptotrombidium myotis, the soft tick Carios kelleyi, the batfly Basilia forcipata, the batbug Cimex pilosellus, and the flea Myodopsylla borealis). Five species were analyzed by prevalence and intensity (C. pilosellus, M. borealis, L. myotis, S. bakeri, and S. occidentalis) based on 2161 counts of 1702 marked individual bats over the 3 summer study periods. We investigated 4 factors potentially influencing prevalence and intensity: age class of the host, reproductive status of adult female hosts, roosts in which the hosts were found, and abiotic conditions during the year sampled. The macronyssid mite, S. occidentalis, was the most prevalent and abundant ectoparasite. Adult big brown bats had more ectoparasites than volant juveniles for most of the species analyzed. In a sample of known age bats at 1 large colony, bats of 4 yr of age or greater had higher ectoparasite loads of S. occidentalis and S. bakeri when compared with younger bats. Lactating female bats had the highest prevalence and intensities of most ectoparasites. Annual differences in ectoparasite prevalence and intensity were related to temperature and humidity, which can affect the nidicolous species of ectoparasites. Residents of 2 buildings sprayed insecticides in response to Cimex sp., and this appeared to reduce ectoparasitism of S. occidentalis and C. pilosellus present at these buildings. Intensity of S. occidentalis had no influence on annual survival of big brown bats.

Fleas parasitizing domestic dogs in Georgia, USA: Species composition and seasonal abundance

Monthly flea collections were made from domestic dogs in Bulloch County, Georgia, USA from September 1996 to August 2004. A total of 2518 fleas belonging to 8 species were collected. The most common flea was the cat flea, Ctenocephalides felis (389 males and 1148 females), followed by the dog flea, Ctenocephalides canis (250 males and 285 females), a generalist/carnivore flea, Pulex simulans (106 males and 213 females), and a sticktight flea, Echidnophaga gallinacea (3 males and 89 females). Small numbers of rabbit-associated fleas (25 Cediopsylla simplex and 6 Odontopsyllus multispinosus) and rodent-associated fleas (3 Orchopeas howardi and 1 Polygenis gwyni), suggested that certain dogs had acquired these particular ectoparasites through hunting activities. Sex ratios of each of the five most frequently collected flea species were female-biased. Seasonally, C. felis, C. canis, and P. simulans, all showed distinct abundance peaks in late summer or autumn.