Host location,survival and fecundity of the Oriental rat flea Xenopsylla cheopis (Siphonaptera: Pulicidae) in relation to black rat Rattus rattus (Rodentia: Muridae) host age and sex

Host choice and fecundity are two factors that may contribute to the variation in flea counts observed when assessing the potential risk of flea-borne transmission of pathogens from rodents to humans. Using the black rat, Rattus rattus Linnaeus, as host the effects of age and sex on host choice and fecundity of the Oriental rat flea, Xenopsylla cheopis Rothschild, were examined experimentally at 25 degrees C and 80% rh. During the first two days of emergence from cocoons, female fleas dominated the sex ratio by 4:1 but from the third day onwards this switched to a male-dominated sex ratio of 4:1. The sex of the flea did not influence their host-seeking behaviour. Newly emerged fleas of both sexes were not influenced by the rat's presence and at seven days old both sexes demonstrated similar levels of attraction toward the rat host. The sex of the rat did not affect flea host-seeking behaviour. There was a 50-70% decline in the initial number of adult fleas during the first week after their release onto a rat host, and this decline was greatest on juvenile rats. Flea fecundity was also significantly lower on juvenile rat hosts but no differences due to the sex of the rat were observed. This experimental study supports the hypothesis that differences in flea count due to host sex, reported in field surveys, result from sexual differences in host behaviour and not from discriminatory host-seeking behaviour by X. cheopis. Differences in flea count due to host age may be affected by differences in X. cheopis fecundity, which may itself be mediated by host behaviour such as grooming.     

印鼠客蚤侵袭与离开宿主习性的观察

印鼠客蚤的跳跃高度,攻击宿主距离,侵袭宿主蚤数,吸血率和离开宿主时间均远超过二齿新蚤。印鼠客蚤滞留于活宿主时间明显长于死宿主。     

Palatability and toxicity of fipronil as a systemic insecticide in a bromadiolone rodenticide bait for rat and flea control

Vector control in plague-infested areas requires a simultaneous killing of rodents and their fleas. We investigated the efficacy of a combination of a systemic insecticide, fipronil, in a rodenticide bait formulation under laboratory conditions. Four different concentrations of fipronil (0.05%, 0.005%, 0.0005% with acetone as a solvent, and 0.05% with propylene glycol as a solvent) and two controls (solvents only) were combined with the rodenticide bait (crushed organically grown wheat with 0.005% bromadiolone). Each concentration was offered together with an untreated non-poisonous challenge bait to 10 singly caged Rattus rattus L., each with 100 rat fleas Xenopsylla cheopis Rothschild (Siphonaptera: Pulicidae) in the nest. Treated bait consumption was relatively low and an unsatisfactory rat mortality of around 50% only was obtained in all tests. The palatability of the bait, however, was not affected by the fipronil concentration. Even at the lowest fipronil concentration, average flea mortality was still above 95%, and doses of more than I mg fipronil per kg rat body weight gave a nearly complete kill of fleas. Fipronil can be highly effective as a systemic insecticide to for flea control, provided that a more attractive bait base for roof rats is used.     

中国云南部分人间鼠疫流行区蚤类区系调查(英文)

归纳了中国云南 13个人间鼠疫流行区的调查资料 ,对调查疫区的蚤类区系进行了研究。总计捕获12 0 77只小兽 ,隶属啮齿目、食虫目及攀目 3个目中的 9科、2 9属、4 7种。从小兽体表共采获 9369只蚤 ,经分类鉴定 ,隶属 5科、18属、33种。 33种蚤及 4 7种小兽宿主均按其分类阶元详细列于文末。结果表明 ,山区蚤及小兽宿主的种数明显多于坝区。坝区农耕地的优势种相对简单 ,优势种地位突出 ,黄胸鼠及印鼠客蚤分别是最重要的宿主及蚤种 (构成比分别为 83 2 7%和 75 32 % )。山区的优势种相对较复杂 ,优势种的种类较多 ,但其构成比较低 ( 10 96%～ 4 7 95% )。黄胸鼠及绒鼠为山区地带的两种优势宿主 ,缓慢细蚤、端凹栉眼蚤、印鼠客蚤、偏远古蚤及短突栉眼蚤为山区地带的 5种优势蚤种。多数蚤种可寄生两种以上的小兽宿主 ,但其所寄生的主要宿主并不多。结果提示 ,作为疫区主要媒介的印鼠客蚤及其所对应的主要寄生宿主 (黄胸鼠 )在坝区突出的优势种地位 ,似可解释近年疫区的鼠疫病人主要出现在坝区的原因     

中国云南人间鼠疫流行区蚤类宿主特异性及宿主选择(英文)

应用生态学中的生态位宽度及生态位重叠研究方法,对中国云南人间鼠疫流行区１１种蚤的宿主特异性及宿主选择进行了研究。宿主特异性用Ｌｅｖｉｎｓ生态位宽度进行测定。宿主选择用夹角余弦生态位重叠进行测定。结果表明：长形病蚤普洱亚种及印鼠客蚤的生态位宽度最窄、宿主特异性最高,近端远棒蚤二刺亚种及斯氏新蚤滇川亚种的生态位最宽、宿主特异性最低。印鼠客蚤（云南人间鼠疫流行区的主要鼠疫媒介）的优势宿主是黄胸鼠。印鼠客蚤较高的宿主特异性意味着该蚤可能主要在其优势宿主的不同个体间保存或传播鼠疫病原体。短突栉眼蚤及端凹栉眼蚤在宿主选择上较接近,而其它蚤种在宿主选择上差异较大。     

苯醚威作用于印鼠客蚤的组织学研究

【目的】通过研究苯醚威对印鼠客蚤 Xenopsylla cheopis (Rothschild,1903)的早 3 龄幼虫和未吸血新羽化成虫的组织学变化,探讨其灭蚤机理,为鼠疫媒介蚤种的防治提供基础资料。【方法】以微量点滴法将苯醚威施药于印鼠客蚤早3龄幼虫和未吸血新羽化成虫,采用组织学、显微摄影及统计学方法观察组织变化。【结果】经苯醚威作用后,印鼠客蚤的早 3 龄幼虫的表皮增厚、卵巢芽生殖细胞萎缩、睾丸芽精原细胞间质减少;未吸血新羽化成虫的睾丸塞消失快、唾液腺细胞破坏严重、中肠上皮细胞萎缩。【结论】(1)苯醚威通过干扰印鼠客蚤幼虫的变态,引起幼虫表皮、生殖芽异常改变,不能发育为成虫而死亡;(2)苯醚威可加速印鼠客蚤新羽化雄性成虫的睾丸塞吸收;(3)苯醚威可破坏印鼠客蚤新羽化成虫的唾液腺细胞,并引起中肠上皮细胞萎缩。     

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.     

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.     

Ectoparasites in rodents of the urban region of Belo Horizonte, MG. III. Fleas, Anoplura and Acari indices in Rattus norvegicus norvegicus

The total and specific indices of fleas, lice and mites were determined for ectoparasites on Rattus norvegicus norvegicus capture in urban areas of Belo Horizonte, Minas state, Brazil, from June 1980 to September 1982. In view of the limiting or critical values attributed to flea indices above all the "cheopis" index, proposed by several authors as a complementary measure for bubonic plague surveillance, the community of Belo Horizonte would have been exposed to this infection. The annual total indices ranged from 0.3 to 2.4 and the prevalent flea was Xenopsylla cheopis (99.2%), with the highest indices coinciding with the late dry-cool season. On two occasions, in this period, the community would have remained highly exposed to infection, since the index-limits were superseded: 8.8 (October 1980) and 6.2 (September 1982). It is suggested that preventive measures, such as protection against rat insecticide treatment may be efficiently applied in the late dry-cool season, or previous to the rainy season, before the elimination of rats. Reports on indices of lice and mites are important as they may establish index-limits for certain infections exclusive to rodents.     

Experimental transmission of murine typhus by Xenopsylla cheopis flea bites

Transmission of Rickettsia typhi to rats by the bites of Xenopsylla cheopis (Rothschild) fleas was investigated. Procedures rigorously excluded the possibility of contamination of the host skin by flea faeces. Fleas with R. typhi infection (21-25 days post-infection) which fed through bolting cloth (45 min exposure to ten fleas) transmitted rickettsiae with a success rate of 20%. Infective fleas allowed free access to their host for 8 h (10-15 fleas/rat) gave transmission rates of 45-68%. They were also capable of inoculating R. typhi through a membrane of rat skin on a feeder. Only fleas which had been infected for 21 days or longer transmitted R. typhi orally. Oral transmission appeared to be the result of regurgitation of rickettsiae present in the foregut lumen rather than through salivary secretions.     

Ectoparasites of rodents of the urban region of Belo Horizonte, MG. II. Variations of the infestation indices in Rattus norvegicus norvegicus

The indices of infestation by the mites Echinolaelaps echidninus and Laelaps nuttalli, the louse Popyplax spinulosa and the flea Xenopsylla cheopis, obtained monthly, from June 1980 to September 1982, on Rattus norvegicus norvegicus in the city of Belo Horizonte, Minas Gerais state, Brazil were related to seasonal period, sex of the host and area of capture. Mites and insects showed different behaviour in relation to these factors. Only the fleas and lice exhibit significant association between the rodents' infestation and the seasonal period, or between the infestation and the rodents' sex or else a variation of the distribution by the three main areas of capture. The fleas showed the highest indices of infestation in the warm-rainy season (October to March) while the infestation by the lice was more prevalent in the dry-cool season. The climatic factors most related with the hosts' infestation were, in decreasing order, rainfall, temperature and relative humidity. Fleas and lice preferentially infested male rodents, being infestation by X. cheopis highly significant.     

Monospecific helminth and arthropod infections in an urban population of brown rats from Doha, Qatar

Parasitic infections were studied for the first time in an urban population of brown rats (Rattus norvegicus) from Doha. Only one species of helminth was found, the cestode Hymenolepis diminuta, and one ectoparasite, the flea Xenopsylla astia, from a sample size of 136 rats (52 males and 84 females). The prevalence of H. diminuta was 17.6%, increasing with host age but not in relation to host sex nor season of capture. Host age was a key factor in influencing abundance of infection, although there was a significant three-way interaction with season and host sex arising through heavy infections in juvenile male rats in the summer. The prevalence of X. astia was 45.6%, although both prevalence and abundance of infestations were season and host age dependent. In the winter prevalence and abundance were similar in both host age and sex groups, but in the summer both parameters of infestation were markedly higher among juveniles compared with adults. We found evidence for some association between these two species: H. diminuta was more prevalent among rats with fleas than among those without, although this association was season-, and independently sex- and age-dependent. There were no quantitative interactions and reasons for this are discussed in relation to the foraging and breeding behaviour of the brown rat in Qatar.     

Notes on the fleas Xenopsylla vexabilis Jordan, 1925 (Pulicidae: Siphonaptera) in Vietnam as related to the problem of anthropogenic plague foci

In the first half of the XX century, the flea Xenopsylla vexabilis, the main vector of the plague agent in the “natural plague foci” of the Hawaii, was shown to be a specific parasite of the small white-toothed rat Berylmys berdmorei, inhabiting the tropical forests and grasslands of Indochina, including Vietnam. X. vexabilis was not recorded in Vietnamese settlements. This flea was found in the fields bordering natural landscapes and agricultural areas as a parasite of the greater bandicoot rat Bandicota indica, Savile’s bandicoot rat B. savilei, and the rat Rattus koratensis. It was assumed that bandicoot rats may have played an important role in the introduction of the flea to the Pacific islands where X. vexabilis was then established on synanthropic rats. The new data do not support the concept of coevolution of the recent epizootic association Rattus exulans-Xenopsylla vexabilis-Yersinia pestis.     

Ectoparasites of commensal rodents in Sulawesi Utara, Indonesia, with notes on species of medical importance

Ectoparasite records are presented for four species of commensal murid rodents (Rattus rattus palelae Miller & Hollister, R. argentiventer (Robinson & Kloss), R. exulans (Peale) and Mus musculus castaneus Waterhouse) in Sulawesi Utara, with particular reference to the potential for these arthropods to bite and transmit pathogens to humans. The flea, Xenopsylla cheopis (Rothschild), was most common on R.r. palelae and is capable of transmitting plague and other pathogens to humans although no current foci for these diseases are known in Sulawesi. Hoplopleura pacifica Ewing and Polyplax spinulosa (Burmeister) sucking lice parasitized all three Rattus species although H. pacifica was mainly associated with R. exulans and P. spinulosa with R.r. palelae. These lice do not bite humans but may be intramurid vectors of murine typhus and other zoonoses. The mites Laelaps echidnina Berlese and L. nuttalli Hirst were both collected; the latter was recorded from all four murid species, mainly R. exulans. The mite Ornithonyssus bacoti Hirst was rare. Only one chigger mite, Walchiella oudemansi (Walch), was retrieved from murids (from R. exulans) and a single Leptotrombidium deliense (Walch) chigger was taken from a human subject. Although L. deliense is a significant vector of scrub typhus, a disease known from Sulawesi, the L. deliense-R. argentiventer relationship frequently noted in the ecology of this rickettsial disease, was not evident in this survey. Other ectoparasites collected from murids were the ticks, Ixodes granulatus Supino (first record for Sulawesi), Haemaphysalis sp. and Dermacentor sp., the mites Myocoptes musculinus (Koch) and Listrophoroides cucullatus (Trouessart), acarids and a uropodid.(ABSTRACT TRUNCATED AT 250 WORDS)     

The flea genus Sigmactenus (Siphonaptera: Leptopsyllidae): a new species from timor and new material from New Guinea and the Philippines

Both sexes of Sigmactenus timorensis n. sp. are described from Rattus tanezumi and Rattus exulans collected in West Timor, Indonesia. The true host presumably is a native murine rat such as the extant, endemic Rattus timorensis or 1 of several extinct, endemic Timorese rats. Analyses of new collections of Sigmactenus cavifrons and Sigmactenus toxopeusi from New Guinea demonstrate that these fleas show considerable morphological variation. We propose that they represent a single species with the name S. toxopeusi having priority. New collections of Sigmactenus werneri from the Philippines expand the known hosts and geographical distribution of this flea.     

Evidence for a negative fitness-density relationship between parent density and offspring quality for two Xenopsylla spp. parasitic on desert mammals

We tested the hypothesis of negative fitness-density relationships and predicted that an increase in the density of parent fleas would result in lower survival rates and longer development time of pre-imagoes as well as shorter time to death from starvation of newly emerged imagoes. These predictions were experimentally tested on Xenopsylla conformis Wagner and Xenopsylla ramesis Rothschild feeding on two rodent species, Meriones crassus Sundevall or Dipodillus dasyurus Wagner. Survival of larvae and pupae, but not eggs, was negatively affected by parent density. An increase in parent density led to a decrease in the number of imagoes of the next generation. Eggs of both species developed faster when the parents were at low densities on either host. The same was true for larval X. ramesis, but not larval X. conformis. The negative effects of parent density on the duration of pupal development were evident in X. conformis, parents of which fed on both hosts, and X. ramesis from parents fed on M. crassus, whereas X. ramesis from parents fed on D. dasyurus developed faster at low densities. A negative effect of density on the development of offspring from egg to imago in X. conformis was manifested mainly when parent fleas fed on D. dasyurus, whereas the negative effect of density on offspring development in X. ramesis was manifested mainly when parent fleas fed on M. crassus. Although there was no general effect of parent density on the resistance of imago offspring to starvation, male X. ramesis from parents fed at the highest density survived starvation for significantly shorter times compared with those from parents fed at lower densities. Manifestation of the negative effect of parent density on offspring quality appears to vary with flea species and may be affected by host species.     

Effect of sex, size, and age of commensal rat hosts on the infestation parameters of their ectoparasites in a rural area of Egypt.

The present study was carried out in the Bilbeis area, Sharqiya Governorate, Egypt. A total of 127 male and 115 female black rats Rattus rattus and 124 male and 153 female Norway rats R. norvegicus was collected during the study period. A total of 20,643 and 40,997 ectoparasites was recovered from R. rattus and R. norvegicus, respectively. Three common mite species were recovered from both rat hosts: Ornithonyssus bacoti, Radfordia ensifera, and Laelaps nuttalli. Three common flea species were also recovered from both rat hosts: Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis. Polyplax spinulosa was the only louse species that infested both rat hosts. Rats that lived more than 12 mo formed about 24 and 14% of the populations of the black and Norway rats, respectively. The prevalences and general indices of many ectoparasites were significantly higher on males than on females of both rat hosts. Seasonal differences in prevalences and general indices of many ectoparasites were recorded between the 2 sexes of both rat species. Prevalences and general indices of most ectoparasites on both rat species showed a tendency to increase with increasing size and age of rat hosts. The type and degree of correlation between prevalences and general indices on the one hand and each of body size and age on the other hand differed among the species of ectoparasites.     

SPATIAL PATTERN ANALYSIS OF XENOPSYLLA CHEOPIS (SIPHONAPTERA:PULICIDAE) ON ITS DOMINANT RAT HOST,RATTUS FLAVIPECTUS IN THE FOCI OF HUMAN PLAGUE IN YUNNAN,CHINA*

Abstract Xenopsylla chewpis is the main transmitting vector of plague in the foci of human plague in Yunnan China, where its dominant rat host is Rattus flavipectus Spatial distribution pattern of X. cheopis among the individuals of R fluvipectus is studied. Iwao's linear regression method and a significance test of random deviation for the method were used. in the light of Iwao's method, a regression model was established. The model is M =α+βM = 4.0064 + 2.0153M where both α and β are considerably higher than 0 and 1 respectively, the border values for determining spatial pattern of populations. The calculated F value is 4, 5892 (P<0.05) in the significance test of random deviation. The spatial pattern of X. cheopis among the individuals of its dominant host R flavipectus is of an aggregate distribution. The aggregated distribution pattern means that the flea individuals do not evenly distribute on rat host but gather as different size groups on rat individuals. This uneven distribution further suggests that the transmitting opportunity is not always the same even if the frequency of contacting the same species of infected rat, R flavipectus is the same.     

Fleas of Small Mammals on Reunion Island: Diversity,Distribution and Epidemiological Consequences

The diversity and geographical distribution of fleas parasitizing small mammals have been poorly investigated on Indian Ocean islands with the exception of Madagascar where endemic plague has stimulated extensive research on these arthropod vectors. In the context of an emerging flea-borne murine typhus outbreak that occurred recently in Reunion Island, we explored fleas'' diversity, distribution and host specificity on Reunion Island. Small mammal hosts belonging to five introduced species were trapped from November 2012 to November 2013 along two altitudinal transects, one on the windward eastern and one on the leeward western sides of the island. A total of 960 animals were trapped, and 286 fleas were morphologically and molecularly identified. Four species were reported: (i) two cosmopolitan Xenopsylla species which appeared by far as the prominent species, X. cheopis and X. brasiliensis; (ii) fewer fleas belonging to Echidnophaga gallinacea and Leptopsylla segnis. Rattus rattus was found to be the most abundant host species in our sample, and also the most parasitized host, predominantly by X. cheopis. A marked decrease in flea abundance was observed during the cool-dry season, which indicates seasonal fluctuation in infestation. Importantly, our data reveal that flea abundance was strongly biased on the island, with 81% of all collected fleas coming from the western dry side and no Xenopsylla flea collected on almost four hundred rodents trapped along the windward humid eastern side. The possible consequences of this sharp spatio-temporal pattern are discussed in terms of flea-borne disease risks in Reunion Island, particularly with regard to plague and the currently emerging murine typhus outbreak.