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PubMed1978

Fleabite allergic dermatitis: a review and survey of 330 cases.

Clinical signs of acute fleabite allergic dermatitis (FAD) in dogs included intense pruritus and erythema. Dogs with chronic FAD had diminished pruritus. The primary lesion of FAD was a papule. Secondary lesions (hyperkeratosis and hyerpigmentation) were common. Diagnosis of FAD was based on history of flea infestation and on type and location of lesions. Intradermal testing with glycerinated flea antigen was of little diagnostic value. Treatment of FAD included (1) breaking the flea life cycle in the indoor and kennel environment by vacuuming and washing bedding as well as by the use of aerosol insecticides for fumigation, (2) minimizing flea infestation on the dogs by using insecticidal dips, baths, and flea collars, and (3) hyposensitization with flea antigen.

Animals↗
PubMed1993

[Epidemiology of the plague. Changes in the concept in research of infection chains since the discovery of the plague pathogen in 1894].

Three major plague epidemics have been recorded worldwide up to this day: the Justinian plague in the 6th century, the Black Death in the 14th century and the recent 20th century pandemic. The latter occurred at a time of advanced microbiological knowledge which permitted the etiology and the modes of transmission and spread of this bacterial infectious disease to be clarified. The present thesis is an attempt to describe the changes in plague research that occurred during that period of time. While the German, Austrian, British, Russian and Egyptian plague Commissions studying the Indian plague outbreak after 1896 contributed only little to the fundamental epidemiological knowledge on plague, several individual researchers succeeded in discovering some of the key facts in the etiology and transmission of the disease. Alexandre Yersin discovered the pathogenic agent of plague (Hongkong 1894), E.H. Hankin, P.L. Simond (Bombay 1898) and J.A. Thompson (Sydney 1900) recognized the role of rat plague, M. Ogata (Formosa 1897) and P.L. Simond (Bombay 1898) observed the transmission of the disease by fleas, and A.W. Bacot and C.J. Martin (1914) described the specific mechanism of transmission of plague. Accordingly, fleas transmit plague from rat to man, the efficiency of the flea as a vector depending on a blocking phenomenon specific of each flea species. The Indian rat flea (Xenopsylla cheopis) has been recognized the most efficient vector. Although the involvement of wild rodents was already known shortly after the turn of this century, the concept of sylvatic plague (the plague of wild rodents) as opposed to murine plague (the plague of commensal rodents) only emerged between 1920 and 1950. It led to taking stock of all hosts and vectors of the disease and thereby defining the natural foci of plague. According to this concept plague is primarily a disease of wild rodents which have been carrying it together with their fleas since ever. As man and urban rats only become infected occasionally, they do not constitute chronic foci. The occurrence of persistent foci rather depends on the interaction of resistant and sensitive wild rodents (burrowing animals) as was discovered by French researchers in the Middle East as late as the 1950s and 1960s. The concept of rodent-dependent transmission was somewhat attenuated by the discovery of direct interhuman transmission by French researchers between 1930 and 1965.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

[An experimental study of the possibility for the preservation of the causative agent of plague in the nest substrate of the long-tailed suslik].

How long Yersinia pestis can preserve in the nest substrate of Spermophililus undulatus and whether it can infect the animals contacting with the substrate infected with flea feces and carcasses were studied in a Tuva natural focus. The infected material was kept in special niches of a bunkering laboratory, which imitated a souslik nest. Biological, serological, and bacteriological studies were conducted after different storage periods. The experiment used 25 sousliks, 56 albino mice, and 3256 fleas. Two hundred and ninety flea carcasses were individually explored. Y.pestis was ascertained to survive in the nest substrate infected with flea feces and carcasses. The pathogen may be preserved as a mutant in the flea carcasses, as evidenced by the isolation of 6 Y. pestis cultures from flea carcasses as a L-form. There is evidence for the fact that healthy animals may be infected on their contact with the contaminated substrate.

Animals↗
PubMedDate not supplied

Plague in Lushoto district, Tanzania, 1980-1988.

Rodents were live-trapped in selected plague-inflicted villages from June 1980 to March 1988. Flea infestation rates were determined and the animals were serologically tested for plague. Clinically suspected and clinically healthy people in the affected areas were similarly tested for plague antibodies. Of 1596 rodent sera tested, 91 (5.7%) were positive for plague. These were mostly from Rattus rattus, Mastomys natalensis, Otomys spp. and Pelomys fallax. A total of 1772 fleas, of which Dinopsyllus lypusus, Xenopsylla brasiliensis and Ctenophthalmus calceatus comprised the largest proportion, was collected from the captured rodents. Total flea indices ranged from 0.67 to 1.12 fleas per rodent. A total of 2809 human cases and a mortality rate of 10.2% were recorded in 1980-1988. It was concluded that most rodent species in the area were suitable reservoirs of plague and that D. lypusus, X. brasiliensis and C. calceatus were probably responsible for transmitting the pathogen. Lack of effective quarantine measures during outbreaks was partly responsible for the spread of the disease to many villages, while inadequate rodent and flea control and poor sanitary measures could be responsible for continued outbreaks of plague in the area.

Animals↗
PubMed2006

Temporal dynamics of a T-cell mediated immune response in desert rodents.

Immunocompetence, the general capacity of an individual host to mount an immune response against pathogens, is commonly assessed by the response to a challenge of the immune system by injection of phytohaemagglutinin (PHA). The response to PHA is commonly considered a reliable estimate of the T-cell mediated immune response. We investigated the temporal pattern of the PHA response in 10 rodent species from the Negev desert, Israel. We hypothesized that the temporal dynamics of the PHA response would differ among species with different natural patterns of flea parasitism. We injected PHA subcutaneously in the footpad of each rodent and measured its PHA response 6, 24 and 48 h after injection. Rodent species showed two types of PHA response. One type was rapid and characteristic of rodents that had either species-poor flea assemblages, or that are rarely attacked by fleas. This response peaked approximately 6 h after PHA injection. The second type of response was delayed and was typical of rodents that have either species-rich flea assemblages or high abundance and prevalence of fleas or both. Their response to PHA peaked 24 h after injection. Furthermore, rodents that responded promptly had a lower maximum response than rodents with a delayed response. Our results suggest the occurrence of a trade-off between intensity and latency of the PHA response and, therefore, the necessity to account for the relationship between maximum PHA response and time after injection when making interspecific comparisons of immunocompetence.

Animals↗
PubMed2006

A role for vector-independent transmission in rodent trypanosome infection?

Within host-pathogen systems where vector-borne transmission is the primary route of infection, little or no attention has been paid to the relative importance of secondary or alternative routes of transmission. Here, by contrast, we report the results from a controlled longitudinal field-scale experiment in which the prevalence of fleas (Siphonaptera) was manipulated and the occurrence and distribution of a flea-borne protozoan (Trypanosoma (Herpetosoma) microti) in a natural field vole (Microtus agrestis) population was monitored over a 2-year period. A non-systemic insecticide was applied to individual voles within two treatment grids and the prevalences of fleas and of T. microti were monitored on these and on two control grids. Blood samples were taken from all voles and PCR-based methods used to determine infection status. Insecticidal treatment was highly effective at reducing overall flea prevalence and recaptured animals (treated ca. 4 weeks previously) were very rarely infested (ca. 3%, compared with 50-70+% normally). On the other hand, the probability of trypanosome infection was reduced in treated animals on experimental grids to only around one-third of that normally observed. This suggests that direct, as opposed to flea-borne, transmission may not only occur, it may also be of epidemiological importance. The possibility that the importance of such transmission routes may have been underestimated in 'vector-borne' infections more generally is discussed.

Animals↗
PubMed1993

Mode of action of pyriproxyfen and methoprene on eggs of Ctenocephalides felis (Siphonaptera: Pulicidae).

Adult cat fleas were exposed to residues of pyriproxyfen and methoprene in glass vials, then fed on a cat 24 h later to investigate the mode of action of juvenoid growth regulators on embryonic development in flea eggs. Eggs laid by pyriproxyfen-treated fleas within 70 h after exposure to this juvenoid were often devoid of yolk and frequently collapsed after oviposition. Minimal amounts of yolk were deposited in eggs laid after 70 h, and no blastoderm was formed. These results are significant because both modes of action were different than those observed earlier by investigators studying ovicidal effects in adult insects treated with juvenile hormone. In contrast to the pyriproxyfen results, eggs laid by methoprene-treated fleas showed no gross morphological effects, and these eggs remained turgid during embryogenesis. However, the eggs either did not hatch or the larvae died within hours after hatching. Histological examination of the eggs revealed that most of the eggs contained segmented embryos which had apparently died during blastokinesis. Although eggs of some insects exposed to juvenile hormone during oogenesis fail to undergo germ band formation, there was no evidence of this effect in methoprene-treated cat fleas.

Animals↗
PubMed2006

Characterization of late acyltransferase genes of Yersinia pestis and their role in temperature-dependent lipid A variation.

Yersinia pestis is an important human pathogen that is maintained in flea-rodent enzootic cycles in many parts of the world. During its life cycle, Y. pestis senses host-specific environmental cues such as temperature and regulates gene expression appropriately to adapt to the insect or mammalian host. For example, Y. pestis synthesizes different forms of lipid A when grown at temperatures corresponding to the in vivo environments of the mammalian host and the flea vector. At 37 degrees C, tetra-acylated lipid A is the major form; but at 26 degrees C or below, hexa-acylated lipid A predominates. In this study, we show that the Y. pestis msbB (lpxM) and lpxP homologs encode the acyltransferases that add C12 and C(16:1) groups, respectively, to lipid IV(A) to generate the hexa-acylated form, and that their expression is upregulated at 21 degrees C in vitro and in the flea midgut. A Y. pestis deltamsbB deltalpxP double mutant that did not produce hexa-acylated lipid A was more sensitive to cecropin A, but not to polymyxin B. This mutant was able to infect and block fleas as well as the parental wild-type strain, indicating that the low-temperature-dependent change to hexa-acylated lipid A synthesis is not required for survival in the flea gut.

Acyltransferases↗
PubMed2006

Population survey of Egyptian arthropods for rickettsial agents.

Between June 2002 and July 2003, 987 fleas, representing four species, and 1019 ticks, representing one argasid and eight ixodid species, were collected from Egyptian animals. These arthropods were tested for rickettsial agents using polymerase chain reaction. DNAs from Anaplasma and Ehrlichia spp. were detected in 13 ticks. Previously undescribed Bartonella spp. were detected in 21 fleas. Coxiella burnetii was detected in two fleas and 20 ticks. Rickettsia typhi was detected in 27 fleas from 10 cities. Spotted fever group rickettsiae were detected in both fleas and ticks and included Rickettsia aeschlimanii and an unnamed Rickettsia sp.

Anaplasma↗
PubMedDate not supplied

Tungiasis.

Tungiasis is a neglected parasitic skin disease caused by the permanent penetration of the female sand flea (also called jigger flea) Tunga penetrans into the skin of its host. After penetration, most commonly on the feet, the flea undergoes an impressing hypertrophy, and some days later the abdominal segments of the flea have enlarged up to the size of about 1 cm. The flea infestation is associated with poverty and occurs in many resource-poor communities in the Caribbean, South America and Africa. In this review, a historical overview on tungiasis is given. The natural history, pathology, epidemiology, diagnosis, therapy and control of the parasitic skin disease are discussed. It is concluded that tungiasis is an important parasitosis causing considerable morbidity in affected populations. Future studies are needed to increase the knowledge on the biology, pathophysiology, epidemiology, therapy and control of the ectoparasite.

Animals↗
PubMed2006

Alternative management tactics for control of Phyllotreta cruciferae and Phyllotreta striolata (Coleoptera: Chrysomelidae) on Brassica rapa in Massachusetts.

The flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (F.) (Coleoptera: Chrysomelidae: Alticinae) are significant pests of crops in the Brassicaceae family. From 2001 to 2003, the efficacy of both new and commonly used treatments for the control of flea beetles in brassicas, Brassica rapa L., were evaluated in three small plot, randomized complete block design trials. Row cover and carbaryl (applied as a weekly foliar spray) were found to be the most consistent at reducing damage in comparison with untreated controls in all trials. Two new products that may provide adequate flea beetle control are spinosad (in either conventional or organic formulations) and thiamethoxam. The plant-derived compounds azidiractin and pyrethrin did not protect treated plants from flea beetle feeding. Treatment of plants with kaolin, or removal of the beetles with a vacuum, also did not reduce the level of crop damage. The level of damage at harvest was found to be correlated with population size of flea beetles in each plot, as measured by captures on yellow sticky traps and direct visual counts. Removal of the outer two leaves of individual B. rapa plants reduced the total number of holes per plant by 40%, while only removing 15% of the leaf area.

Agriculture↗
PubMed2001

Seasonal studies on commensal rats and their ectoparasites in a rural area of Egypt: the relationship of ectoparasites to the species, locality, and relative abundance of the host.

The present study was carried out in 3 villages, namely Kafr Ayoub Soliman, Kafr Ibrahim El-Aidi, and El-Sa'adat, Sharqiya Governorate, Egypt. A total of 519 rats was collected from the 3 study sites: 46.6% Rattus rattus, and 53.4% Rattus norvegicus. A total of 20,643 ectoparasites was recovered from R. rattus: 33.3% mites, 33.8% fleas, and 32.9% lice. From R. norvegicus a total of 40,997 ectoparasites was recovered: 28.9% mites, 31% fleas, and 40.1% lice. Three common mite species were recovered from both rat hosts, i.e., Ornithonyssus bacoti, Radfordia ensifera, and Laelaps nuttalli. Three common flea species were also recovered from both rat hosts, i.e., Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis. Polyplax spinulosa was the only dominant louse species that infested both rat hosts. Rats did not show a definite breeding season, and the seasonal rat indices were generally low in different study sites. There were no significant differences between the prevalence of each of mites, fleas, and lice in both rat species. The total general indices of mites and fleas, on the other hand, was significantly higher in R. norvegicus. The general index of X. cheopis was high and ranged between 5.9 in R. rattus and 14.5 in R. norvegicus. Season-related changes were observed in the general index of each of L. segnis infesting both rat species and R. ensifera and O. bacoti infesting R. norvegicus. The prevalence and general indices of some ectoparasites showed differences related to the locality of their rat hosts. Seasonal changes in the general indices of some ectoparasites paralleled seasonal changes in the relative abundance of their rat hosts.

Animals↗
PubMed2002

Comparison of nodulisporic acid analogs in a Lucilia sericata in vitro assay and a Ctenocephalides felis membrane feeding system.

A medicinal chemistry program on the nodulisporic acid chemical class, guided by an artificial membrane flea-feeding assay, has recently identified permissive and nonpermissive regions of the pharmacophore for exploitation against fleas. This pathway was validated when several promising compounds from this program were administered orally to dogs at 15.0 mg/kg and found to have >90% flea activity for 2 wk. To determine if a surrogate insect assay would have provided the same guidance, a nodulisporic acid analog series was examined in both a Lucilia sericata larval assay and an artificial membrane flea-feeding assay using Ctenocephalides felis. Results from both insect assays were concordant in that even subtle chemical modification or substitution to the left-hand side of the nodulisporic acid pharmacophore resulted in substantial loss of insecticidal activity. Both assays were also in general agreement that the only modifications to the pharmacophore that did not result in loss of activity occurred to the C-8 side chain on the right-hand side of the molecule. Although there was good agreement between the 2 assays on the general regions of the pharmacophore, there was variance on individual compounds in the mono- and disubstituted amide series from the C-8 side chain. For example, the L. sericata assay showed several analogs from this subclass to possess similar activity to the parent acid, whereas the membrane assay indicated superior activity against fleas relative to the same parent. Consequently, although there was substantial general agreement between the assays, it was concluded that finer optimization of a lead compound should be done against the target parasite, even if it is ex vivo, as early as possible in a medicinal chemistry program.

Animals↗
PubMed2002

Nodulisporic acid: its chemistry and biology.

The discovery of the natural product nodulisporic acid A (NsA A) and its potent, systemic insecticidal activity at Merck Research Laboratories in 1992 stimulated intense scientific scrutiny. Interest in this new class of indole diterpenes led to extensive delineation of its properties, both chemical and biological. Synthetic modification of NsA A served to identify its pharmacologically permissive and non-permissive regions, produced semisynthetic derivatives with enhanced adulticidal flea efficacy (both in vitro and in vivo), and provided useful tools to support biological studies. Early observations in rodent models showed a wide therapeutic index for NsA A and detailed mechanism of action investigations demonstrated that it selectively modulated an invertebrate specific glutamate-gated ion channel for which no mammalian homolog exists. Consistent with these mechanistic conclusions, dogs treated orally with either NsA A or closely related amide analogs (15 mg/kg dosages) showed no apparent toxicity, and measurement of systemic flea efficacy in these animals demonstrated that prolonged antiparasitic activity was attained, up to 14 days subsequent to treatment with a single p.o. dose for fleas or up to 4 weeks for ticks. The extended flea efficacy was correlated to both the in vivo pharmacokinetic profile of a given analog and its intrinsic in vitro potency against fleas. In addition, studies directed towards the total synthesis of NsA A have been reported.

Animals↗
PubMed2005

Evaluation of experimental transmission of Candidatus Mycoplasma haemominutum and Mycoplasma haemofelis by Ctenocephalides felis to cats.

OBJECTIVE: To determine whether Ctenocephalides felis can transmit Mycoplasma haemofelis (Mhf) and Candidatus Mycoplasma haemominutum (Mhm) through hematophagous activity between cats. ANIMALS: 11 cats. PROCEDURE: 2 cats were carriers of either Mhf or Mhm. Nine cats had negative results via polymerase chain reaction (PCR) assay for Mhf and Mhm DNA; 3 of those cats were infected from the chronic carriers via i.v. inoculation of blood. At the time of maximum organism count for each of the Mycoplasma spp, 1 chamber containing 100 C felis was bandaged to the amplifier cats. Five days later, fleas, feces, larvae, or eggs from each chamber were analyzed for Mycoplasma spp DNA. Viable fleas from the chambers were allocated into new chambers (3 Mhm and 6 Mhf) and attached to naïve cats for 5 days. Cats were monitored daily for clinical signs and weekly via CBC and PCR assay for infection with Mhf or Mhm for a minimum of 8 weeks. RESULTS: Uptake of Mhf and Mhm DNA into fleas, feces, and, potentially, eggs and larvae was detected. Of the naïve cats fed on by Mhf-infected fleas, 1 cat transiently yielded positive PCR assay results for Mhf on 1 sampling date without clinical or hematologic changes consistent with Mhf infection. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that hematophagous transfer of Mhm and Mhf into fleas occurred and that C felis is a possible vector for Mhf via hematophagous activity.

Animals↗
PubMed1978

Epizootiology of epidemic typhus (Rickettsia prowazekii) in flying squirrels.

Vector transmission of Rickettsia prowazekii among wild flying squirrels, Glaucomys volans, was suggested by the occurrence of natural infection of squirrel lice and fleas. Lice, mostly Neohaematopinus sciuropteri Osburn, were found infected in the fall in each of 2 consecutive years; 4 of the 8 pools of this insect tested were infected. Fleas, Orchopeas howardii (Baker), were found infected on two occasions in 1 of the 2 consecutive years. However, only 2 of 14 flea pools were infected. No evidence of infection was found in mites, Haemogamasus reidi Ewing and Androlaelaps fahrenholzi (Berlese). These findings implicate the flying squirrel louse and flea as possible vectors in nature. Serologic tests of flying squirrel sera revealed a maximum incidence of seroconversions in the fall and early winter months, coincident with the maximum increase in abundance of the suspected arthropod vectors. The infection was found to persist form year to year in the same enzootic foci. Infection appeared to spread most rapidly in young, non-immune animals born in the preceding spring and summer after congregating in dense aggregations in the fall. No other animals in the same habitat were found to have been infected. Aspects of the ecology of the ectoparasites associated with the flying squirrels are described, especially seasonal activity and abundance in nests. The potential public health importance of this sylvan disease in flying squirrels and in its ectoparasites, particularly the non-host specific, wide ranging squirrel flea, is noted.

Animals↗
PubMed2006

Possible vector dissemination by swift foxes following a plague epizootic in black-tailed prairie dogs in northwestern Texas.

To determine whether swift foxes (Vulpes velox) could facilitate transmission of Yersinia pestis to uninfected black-tailed prairie dog (Cynomys ludovicianus) colonies by acquiring infected fleas, ectoparasite and serologic samples were collected from swift foxes living adjacent to prairie dog towns during a 2004 plague epizootic in northwestern Texas, USA. A previous study (1999-2001) indicated that these swift foxes were infested almost exclusively with the flea Pulex irritans. Black-tailed prairie dogs examined from the study area harbored only Pulex simulans and Oropsylla hirsuta. Although P. irritans was most common, P. simulans and O. hirsuta were collected from six swift foxes and a single coyote (Canis latrans) following the plague epizootic. Thus, both of these canids could act as transport hosts (at least temporarily) of prairie dog fleas following the loss of their normal hosts during a plague die-off. All six adult swift foxes tested positive for antibodies to Y. pestis. All 107 fleas from swift foxes tested negative for Y. pestis by mouse inoculation. Although swift foxes could potentially carry Y. pestis to un-infected prairie dog colonies, we believe they play only a minor role in plague epidemiology, considering that they harbored just a few uninfected prairie dog fleas (P. simulans and O. hirsuta).

Animals↗
PubMed2001

[Resurgence of the plague in the Ikongo district of Madagascar in 1998. 2. Reservoirs and vectors implicated].

Our survey of mammals and fleas arose as a result of an outbreak of bubonic plague at an usually low altitude in the Ikongo district (Madagascar), while a previous study had found anti-F1 antibodies in an endemic hedgehog. Animals were sampled with live traps in two hamlets (Antanambao-Vohidrotra, 540 m alt. and Ambalagoavy, 265 m alt.) and with pitfall traps in a neighbouring forest (750 m alt.). Rat fleas were collected by brushing the fur and free-living fleas by use of light traps. The introduced shrew Suncus murinus was found only in the village of Ambalagoavy while the black rat (Rattus rattus) was found in all three sites and the only seropositive rat was caught at Antanambao-Vohidrotra. In contrast, among the Tenrecidae (endemic shrews and hedgehogs) found in the forest near the first village, four animals were found seropositive for anti-F1 antibodies. One of them was carrying the endemic flea Paractenopsyllus pauliani, not yet reported as a vector of plague. The endemic vector of plague, Synopsyllus fonquerniei, was found only in the first village of Antanambao-Vohidrotra, and the cosmopolite flea Xenopsylla cheopis only in Ambalagoavy. Although no Yersinia pestis could be isolated and no F1-antigen could be detected in these animals, we found evidence of the recent transmission of plague in Antanambao-Vohidrotra and the nearby forest, but not in Ambalagoavy. These data corroborate with the sylvatic plague cycle hypothesis in Madagascar and its involvement in the outcome of the bubonic plague outbreak in this district.

Animals↗