Epizootological role of fleas in the Gorno-Altai natural plague focus (a review)

Epizootological role of fleas in the Gorno-Altai natural plague focus (Sailugemsk focus) and numerous data on the flea viability are analyzed and generalized. Information concerning the flea natural infectivity with Yersinia pestis altaica is represented. Ecological peculiarities of some flea species parasitizing the main host, Mongolian pika Ochotona pallasi, and nature of their interrelations with Y. pestis are investigated. It is shown that the flea taxocenosis provides the permanent all year-round circulation of Y. pestis in the Gorno-Altai natural focus. Certain combinations of structural elements of the flea taxocenosis have a dominant significance in determination the circulation process at different phases of the annual epizootic cycle.     

The role of fleas (Siphonaptera) in the epizootiology of plague

This review concerns the role of the fleas in survival and spread of the plague, their influence on the seasonal dynamics of the epizootics, and infection rates of these insects in different natural foci. The critical evaluation is given to the data which are used to calculate the flea transmission probability for mathematical simulation of plague epizootics.     

Paradoxopsyllus scorodumovi (Aphaniptera) flea, an effective vector of plague in a Gorno-Altai natural focus

A study was conducted on the fleas of P. scorodumovi and five local strains of the plague microbe, one of which is typical of the strains of the Altai subspecies and four are non-typical of this nidus. The fleas of this species are capable to transmit not only the plague agent of the strains typical of this nidus but also non-typical ones which differ in some biological properties and are avirulent for most carriers but Pallas's pika. Biological peculiarities of fleas of P. scorodumovi in addition to their high efficiency as vectors of the plague microbe enable us to associate the more active autumn epizooty with fleas of this species.     

Notes on fleas (Siphonaptera) in plague foci on the Tay Nguyen plateau (Vietnam)]

The fleas of wild and commensal small mammals, domestic animals (dogs, cats) and free-living flea forms in houses have been collected in plague nidi of Tay Nguyen plate, Dak-Lak province, Vietnam. Pulex irritans, Ctenocephalides felis felis, Ct. felis orientis were found in the houses on dogs, cats and on the ground floor. Commensal rats in populated areas were infested by Xenopsylla cheopis and rarely by Lentistivalius klossi. The agricultural zone was inhabited by both home and wild animals such as commensal, savannah and forest-dwelling small mammals. The flea fauna of this zone is presented by X. cheopis and L. klossi. In the tropical forest surrounding villages four of the flea species were found: X. vexabilis, a specific parasite of the forest-dwelling rat Berylmys berdmorei, L. klossi found on six species of forest small mammals, Acropsylla girshami from Berylmys bowersii and Pariodontis subjugis from Hystrix brachyura. The agricultural zone is the most possible place of commensal and forest-dwelling small mammals contact, where the latter can get plague microbe.     

Wolbachia endosymbionts in fleas (Siphonaptera)

Intracellular endosymbionts, Wolbachia spp., have been reported in many different orders of insects and in nematodes but not previously in fleas. This is the first conclusive report of Wolbachia spp. within members of the Siphonaptera. Using nested polymerase chain reaction (PCR) targeting of the 16S ribosomal RNA gene, we screened for Wolbachia spp. in fleas collected from 3 counties in Georgia and 1 in New York. The prevalence of Wolbachia spp. detected varied among the 6 different species screened: 21% in the cat flea Ctenocephalides felis (n = 604), 7% in the dog flea C. canis (n = 28), 25% in Polygenus gwyni (n = 8), 80% in Orchopeas howardi (n = 15), 94% in Pulex simulans (n = 255), and 24% in the sticktight flea Echidnophaga gallinacea (n = 101). Wolbachia spp. infection in fleas was confirmed by sequencing positive PCR products, comparing sequenced 16S ribosomal DNA (rDNA) with Wolbachia spp. sequences in GenBank using BLAST search, and subjecting sequence data to phylogenetic analysis. For further confirmation, 16S rDNA-positive samples were reamplified using the wsp gene.     

Adaptations of fleas (Siphonaptera) to parasitism

The paper deals with peculiarities of flea structure determined by their parasitism on mammals and birds. On the basis of the data on diversity of morphological characters, the leading role of structures of the frontal and nototrochanteral complexes in the adaptive evolution of Siphonaptera is substantiated. Peculiarities of the pulicoid, ischnopsylloid, palaeopsylloid, and generalized morphological types are analyzed together with examples of narrow morphological specializations. Distribution of fleas of these morphological types over five groups of hosts differing in the degree of mobility and association with nests and burrows is also analyzed.     

窄板额蚤华北亚种幼虫形态研究（蚤目：细蚤科）

描述了窄板额蚤华北亚种的幼虫形态,并和同属幼虫进行比较。窄板额蚤华北亚种幼虫的形态和棕形额蚤指名亚种幼虫的形态比较相似,但肛梳刚毛数量可以区分,前者总数超过24根,后者总数不超过20根。再通过与其它5种(亚种)额蚤幼虫的形态比较,发现属于额蚤亚属5种幼虫的大颚齿数一般为5个齿,一龄幼虫的破卵器正面为鞋形;而属于鸟额蚤亚属前额蚤灰獭亚种的幼虫的大颚齿数达9个,一龄幼虫的破卵器正面为球拍形。这些差异可能是亚属间的形态差异。     

The plague in Vietnam: history and inventory of collected fleas (insecta, Siphonaptera) in the inhabited zones

Ten flea species are reported in anthropic zones of Vietnam. Xenopsylla vexabilis is also here included because of it has been involved in others plague's countries. Lentistivalius klossi is the only selvatic flea known as parasite of synanthropic rats. L. klossi bispiniformis (Li and Wang, 1958), first describe from Chinese specimens, is here synonymized (syn. nov.) with the nominal subspecies.     

Ways of the fleas (Siphonaptera) fauna formation in the Caucasus

Fleas fauna of the Caucasus is considered, possible ways of its formation are discussed. Caucasian fleas belong to 155 species and 40 genera; 23 species are endemics. Hypothesis on Western Palearctic and Eastern Palearctic sources of the Caucasian fleas' fauna formation are proposed.     

Facultative imaginal diapause in Xenopsylla conformis (Siphonaptera) fleas

The factors favouring the cessation of reproduction in X. conformis are laid in the preimaginal state. The drop in temperature during the formation of imago at the pupal stage is a signal for the cessation of reproduction. Imagos hatched at a temperature lower than that of developmental conditions of preimaginal stages do not start reproduction and enter facultative imaginal diapause state. With further decrease in temperature the state of fleas intensifies. With the rise of temperature fleas come out of diapause. In autumn coming out of diapause begins at a temperature higher than 20 degrees, on the 8th--9th day. The lower air temperature the more rapid is coming out of diapause, at a rise of temperature of 3 to 5 degrees.     

Peculiarities of thoracic and abdominal combs of fleas (Siphonaptera)

The structure of pseudosetae, spinelets, and spines of combs (ctenidia) was studied by means of light and SE microscopy in 80% of genera and subgenera of the World fauna. It is found out that peculiarities of ctenidiae in the prothorax and in tergites of the abdomen are characteristics of families and infraorders of fleas. Some characters of ctenidiae found in certain flea genera are reductions and apparently caused by habitation in some extremal conditions. An absence of ctenidiae in the unfraorder Pulicomorpha is compensated by more developed posterior margin of prothorax and general abbreviation of all thoracal segments. Reasons of ctenidiae absence, which is observed in certain genera of the infraorders Ceratophyllomorpha, Pygiopsyllomorpha and Hystricopsillomorpha associated with the same hosts, is not clear. It is confirmed, that distance between ctenidiae in different flea species associated with the same species host species, however it is recovered, that this distance correlates with the diameter of most thin hair of host. In some flea species the distance between ctenidia spices in females is larger, than in males. It is found, that sexual dimorphism by this character may not be expressed in certain species of closely related species group of fleas. It is suggested that ctenidiae were present even in the common ancestor of fleas. The hypothesis on origin of spines and pseudosetae from setae of the posterior walls of toracal and abdominal segments in the common ancestor of fleas is proposed.     

The Palaearctic centers of taxonomic diversity of fleas (Siphonaptera)

The Palaearctic flea fauna includes 921 species and 479 subspecies from 96 genera of 10 families. Of them, 858 species (94%) from 43 genera are endemic to the Palaearctic; they comprise 40% of the Palaearctic Hystrichopsyllidae, 24% of Ceratophyllidae, and 20% of Leptopsyllidae. Ranges of 581 species (63% of the Palaearctic fauna) are situated within one province or subregion of the Palaearctic. Species with ranges including a part of Asia (592) comprise 87% of the total fauna; 72% of the species (517) are endemic to the Palaearctic. The largest centers of taxonomic diversity of Palaearctic fleas are situated in the East Asian, Central Asian, and Turano-Iranian Subregions: 320 species of fleas (214 of them endemic) from 59 genera (8 endemic) are known from the East Asian Subregion; 270 species (over 120 endemic) from 54 genera (5 endemic) are distributed in the Central Asian Subregion. The Turano-Iranian fauna comprises 213 species (103 endemic) from 47 genera (3 endemic); about 160 species occur in the Turanian Subprovince closest to the Russian borders, one-third of them (52 species, or 33%) are endemic; 69 species more are endemic to the entire Asian part of the Palaearctic. Extra-Asian and extra-Siberian ranges are known in 190 flea species. In the western Palaearctic, 76 species are endemic to the European Province, and 57 species, to the Mediterranean Province; 36 species have Euro-Mediterranean distribution. The fauna of the Saharo-Arabian Subregion comprises 30 species (12 endemic), 6 species have ranges of the Mediterranean-Saharo-Arabian type. Scenarios of the origin of the Siphonaptera at the Triassic-Jurassic boundary are hypothesized. Formation of the Palaearctic flea fauna was mostly supported by the Asian-Indo-Malayan and East Asian-Western American palaeofaunal centers of taxonomic diversity. The long history of faunal exchange between the east Palaearctic and the west Nearctic is manifested by the distribution of the parasites of rodents and insectivores, fleas of the genera Stenoponia, Rhadinopsylla, Nearctopsylla, and Catallagia, belonging to several subfamilies of the Hystrichopsyllidae, as well as members of a number of other flea families. A great number of endemic species in the genera Palaeopsylla and Ctenophthalmus (Hystrichopsyllidae), both in the European and Asian parts of the Palaearctic, can be explained by the junction of the European and Asian continental platforms in the late Cretaceous and their subsequent isolation during the Paleocene. A considerable contribution to the flea fauna in the Russian territory was made by the East Asian-Nearctic center of taxonomic diversity, with a smaller role of the European palaeofauna. Immigration of species of the family Pulicidae from the Afrotropical Region is restricted to the southern territories of Russia.     

The longevity of Leptopsylla segnis fleas (Siphonaptera: Leptopsyllidae)

In experiments, the mean life duration of fleas Leptopsylla segnis on white mice (abundance of fleas within natural limits, up to 10 fleas per mouse) was 22.7 days in females and 18.8 day in males. Maximum life duration was 51 and 37 days respectively. In cases, when the initial numbers of fleas were 20 and 28-34 fleas, the duration of life was decreased. The maximum limit decreased greater than the mean duration of life. A survival dynamics of fleas depended upon the flea number. It was found out, that in cases of high abundance of fleas in the beginning of experiments, the mortality rate of males was lower than in females. During the stay on a host the fleas lost gradually an ability to endure a starvation. Possible mechanisms of the regulation of flea abundance are discussed.     

New Wolbachia endosymbionts from Nearctic and Neotropical fleas (Siphonaptera)

Several species of fleas (Siphonaptera), ectoparasites of mammals and birds, have recently been shown to harbor species of Wolbachia. Here, we extend this data set to 20 more species of Siphonaptera (Rhopalopsyllidae, Stephanocircidae, Pulicidae, Ceratophyllidae, Ctenophthalmidae, Ischnopsyllidae, Leptopsyllidae, and Malacopsyllidae) from sylvatic populations throughout the Nearctic and Neotropical regions. Using polymerase chain reaction, we targeted the Wolbachia 16S ribosomal DNA (rDNA) gene. Applying maximum parsimony- and maximum likelihood-based algorithms, as well as statistical parsimony, we conducted a phylogenetic analysis of Wolbachia 16S rDNA to evaluate its position within the known Wolbachia spp. The analysis recovered the siphonapteran Wolbachia 16S rDNA sequences as a monophyletic group and shows multiple haplotype connections between the Neotropical and Nearctic Wolbachia strains of fleas.     

Number of generations of Xenopsylla gerbilli minax fleas in the Muyunkum (Siphonaptera)

By means of radioactive labelling and mechanical marking of fleas of X. g. minax it was established that they have four generations a year.