Isolation and characterization of 11 microsatellite loci from Oropsylla hirsuta, a vector of sylvatic plague

The flea (Oropsylla hirsuta) is an important vector of the plague bacterium, Yersinia pestis, in black-tailed prairie dog (Cynomys ludovicianus) colonies. We developed 11 anonymous microsatellite primers for O. hirsuta using a subtractive hybridization procedure. All primers were polymorphic exhibiting 4-12 alleles.     

Field evaluation of imidacloprid as a systemic approach to flea control in black‐tailed prairie dogs,Cynomys ludovicianus

Epizootic outbreaks of sylvatic plague have dramatically influenced prairie dog (Cynomys sp.) populations across North America. While a great deal of debate surrounds the cause and persistence of plague, flea control can stop the spread of plague epizootic outbreaks and even increase prairie dog survival under non‐epizootic conditions. We investigated a newly‐developed imidacloprid‐treated grain bait that could potentially reduce flea infestations and mitigate the effects of plague on black‐tailed prairie dogs (C. ludovicianus). We used a study design involving randomly assigned experimental and control study plots to assess the effectiveness of the systemic flea control product. We observed a significant difference in flea prevalence and abundance between experimental and control sites on three of the four sites treated with a single application of imidacloprid‐treated grain bait for up to 90 days post‐treatment. We observed an even greater reduction in flea infestations following the double application of treatment bait on two of three additional experimental sites. While we were unable to reduce flea infestations to the extent reported for more commonly used topical insecticides containing deltamethrin, imidacloprid might still be effective at reducing the risk of plague and halting epizootics. In addition, this systemic product can be more rapidly applied than topical insecticides, providing managers with a tool to quickly reduce flea infestations. Future research is needed to evaluate the effectiveness of different application timing and rates, the utility of the product in limiting plague, and the potential effects on non‐target species that might also consume the treated bait.     

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.     

Phyllotreta cruciferae and Phyllotreta striolata responses to insecticidal seed treatments with different modes of action

The strategy used most commonly in western North America to protect seedlings of canola (Brassica rapa L. and Brassica napus L.) from attack by adults of the flea beetles Phyllotreta cruciferae (Goeze) and Phyllotreta striolata (Fabricius) (Coleoptera: Chrysomelidae) involves planting seed coated with insecticide for systemic activity. Previous research determined that the two beetle species responded differently to the most commonly used neonicotinoid seed dressings. However, other insecticides that exploit different modes of action have commercial potential for managing infestations of these pests, but no information exists on their efficacies for these flea beetle species. Studies were conducted to compare effects of the neonicotinoid compounds, thiamethoxam and imidacloprid, to spinosyn and fipronil as systemic seed treatments for reducing feeding damage to canola seedlings and increasing mortality of P. cruciferae and P. striolata. Phyllotreta cruciferae experienced greater mortality and caused less feeding damage than P. striolata to seedlings treated with the neonicotinoid compounds. Mortality increased and feeding damage decreased significantly when beetles fed upon seedlings treated with fipronil, indicating its potential usefulness for control of these pests. However, spinosyn seed treatment was relatively ineffective against either beetle species. Higher rates of P. striolata mortality with fipronil than thiamethoxam suggest that fipronil may provide improved flea beetle control over hundreds of thousands of hectares in western North America where flea beetle populations are dominated by P. striolata, and control with thiamethoxam has been suboptimal.     

Transmission Efficiency of Two Flea Species (<Emphasis Type="Italic">Oropsylla tuberculata cynomuris</Emphasis> and <Emphasis Type="Italic">Oropsylla hirsuta</Emphasis>) Involved in Plague Epizootics among Prairie Dogs

Plague, caused by Yersinia pestis, is an exotic disease in North America circulating predominantly in wild populations of rodents and their fleas. Black-tailed prairie dogs (Cynomys ludovicianus) are highly susceptible to infection, often experiencing mortality of nearly all individuals in a town as a result of plague. The fleas of black-tailed prairie dogs are Oropsylla tuberculata cynomuris and Oropsylla hirsuta. We tested the efficiency of O. tuberculata cynomuris to transmit Y. pestis daily from 24 to 96 h postinfection and compared it to previously collected data for O. hirsuta. We found that O. tuberculata cynomuris has over threefold greater transmission efficiency (0.18 infected fleas transmit Y. pestis at 24 h postinfection) than O. hirsuta (0.05 fleas transmit). Using a simple model of flea-borne transmission, we combine these laboratory measurements with field data on monthly flea loads to compare the seasonal vectorial capacity of these two flea species. Coinciding with seasonal patterns of flea abundance, we find a peak in potential for flea-borne transmission in March, during high O. tuberculata cynomuris abundance, and in September–October when O. hirsuta is common. Our findings may be useful in determining the timing of insecticidal dusting to slow plague transmission in black-tailed prairie dogs.     

Does Bdellodes lapidaria (Acari: Bdellidae) have a role in biological control of the springtail pest, Sminthurus viridis (Collembola: Sminthuridae) in south-eastern Australia?

Throughout southern Australia, the lucerne flea, Sminthurus viridis (Collembola: Sminthuridae), is an important pest of a variety of winter grain crops and pastures. The predatory mite, Bdellodes lapidaria (Acari: Bdellidae), co-occurs with S. viridis and is reported to be a biological control agent of this pest. Using laboratory bioassays and field experiments, we assessed the susceptibility of B. lapidaria to several pesticides and investigated its impact in controlling S. viridis. In the laboratory, B. lapidaria was found to be susceptible to the synthetic pyrethroids, α-cypermethrin and bifenthrin, but relatively tolerant to the avermectin, abamectin, and organophosphorous chemicals, omethoate and chlorpyrifos. In field experiments, B. lapidaria was not adversely affected by applications of either bifenthrin or omethoate. Despite strong intraspecific interactions, we found no detectable impact of B. lapidaria on S. viridis numbers in the field. These results indicate that B. lapidaria has a relatively high tolerance to several pesticides, perhaps partly through behavioural avoidance, but little impact as a biological control agent on S. viridis in south-eastern Australia.     

The absence of concordant population genetic structure in the black‐tailed prairie dog and the flea,Oropsylla hirsuta,with implications for the spread of Yersinia pestis

The black‐tailed prairie dog (Cynomys ludovicianus) is a keystone species on the mid‐ and short‐grass prairies of North America. The species has suffered extensive colony extirpations and isolation as a result of human activity including the introduction of an exotic pathogen, Yersinia pestis, the causative agent of sylvatic plague. The prairie dog flea, Oropsylla hirsuta, is the most common flea on our study colonies in north‐central Montana and it has been shown to carry Y. pestis. We used microsatellite markers to estimate the level of population genetic concordance between black‐tailed prairie dogs and O. hirsuta in order to determine the extent to which prairie dogs are responsible for dispersing this potential plague vector among prairie dog colonies. We sampled fleas and prairie dogs from six prairie dog colonies in two regions separated by about 46 km. These colonies were extirpated by a plague epizootic that began months after our sampling was completed in 2005. Prairie dogs showed significant isolation‐by‐distance and a tendency toward genetic structure on the regional scale that the fleas did not. Fleas exhibited higher estimated rates of gene flow among prairie dog colonies than the prairie dogs sampled from the same colonies. While the findings suggested black‐tailed prairie dogs may have contributed to flea dispersal, we attributed the lack of concordance between the population genetic structures of host and ectoparasite to additional flea dispersal that was mediated by mammals other than prairie dogs that were present in the prairie system.     

Spotted fever rickettsioses in southern and eastern Europe

Mediterranean spotted fever due to Rickettsia conorii conorii was thought, for many years, to be the only tick-borne rickettsial disease prevalent in southern and eastern Europe. However, in recent years, six more species or subspecies within the spotted fever group of the genus Rickettsia have been described as emerging pathogens in this part of the world. Tick-borne agents include Rickettsia conorii israelensis, Rickettsia conorii caspia, Rickettsia aeschlimannii, Rickettsia slovaca, Rickettsia sibirica mongolitimonae and Rickettsia massiliae. Many Rickettsia of unknown pathogenicity have also been detected from ticks and could represent potential emerging pathogens to be discovered in the future. Furthermore, a new spotted fever rickettsia, Rickettsia felis, was found to be associated with cat fleas and is an emerging human pathogen. Finally, the mite-transmitted Rickettsia akari, the agent of rickettsialpox, is also known to be prevalent in Europe. We present here an overview of these rickettsioses, focusing on emerging diseases.     

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。     

HOST-SPECIFICITY AND HOST-SELECTION OF FLEAS IN FOCI OF HUMAN PLAGUE IN YUNNAN CHINA*

Abstract The host-specificity and the host-selection of 11 species of fleas collected from 47 species of small mammals in foci of human plague in Yunnan, China, were studied by using methods in the evaluation of ecological niche breadth and overlap. Levins' niche breadth was used for the host-specificity. while clip angle niche overlap and a fuzzy clustering analysis were used for host-selection. Of the 11 species of fleas, the host-specificity of Nosopsyllus elongatus puerensis and Xenopsylla cheopis are the highest (narrow niche breadth), and those of Aviostivalis klossi bispiniformis and Neopsylla stevensi sichuanyunnana the lowest (wide niche breadth). Of 11 species of fleas, the dominant host of X. cheopis (a very high effective vector of plague in the foci of human plague in Yunnan Province. China) is Rattw flavipectus (the main animal host and infectious source of plague in the foci). A high host-specificity of X. cheopis implies that X. cheopis mainly maintains or transmits the pathogen of plague among the individuals of its dominant species of host, R. flavipectus. The result of niche overlap analysis reveals that Ctenophthalrnus In-evipre jiciens and Ctenophthaltnus parcus have a similar host-selection while other species of fleas are quite different in their host selection.     

Control of flea populations in a simulated home environment model using lufenuron, imidacloprid or fipronil

Control strategies were evaluated over a 6-month period in a home simulation model comprising a series of similar carpeted pens, housing matched groups of six cats, in which the life-cycle of the flea Ctenocephalides felis felis Bouche (Siphonaptera: Pulicidae) had been established. Additional adult fleas were placed on the cats at intervals to mimic acquisition of extraneous fleas from outside the home. Treatment strategies included a single subcutaneous deposition of injectable lufenuron supported by initial treatments with a short-acting insecticidal spray, or monthly topical applications of imidacloprid or fipronil. An untreated control group indicated that conditions were suitable for flea replication and development. Controls had to be combed on 18 occasions to remove excessive flea burdens and two developed allergic reactions. Lufenuron cats were combed once and required two insecticidal treatments in the first month to achieve control. Even so, small flea burdens were constantly present thereafter. Imidacloprid and fipronil treatments appeared to give virtually complete control throughout. Single fleas were found on imidacloprid cats on two occasions, whereas none were recovered from fipronil cats at any time after the first treatment. Tracer cats were used to monitor re-infestation rates at the end of the trial period. Small numbers of host-seeking fleas were demonstrated in all treatment pens, indicating that total eradication had not been accomplished. It is concluded that the home environment simulation model incorporating tracer animals could provide a powerful tool for studying flea population dynamics under controlled conditions but improved techniques are needed for quantifying other off-host life-cycle stages.     

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