Xenopsylla Cheopis Research Articles

KEBERHASILAN PENANGKAPAN TIKUS (TRAP SUCCESS) DAN INDEKS PINJAL DI DESA KAYUKEBEK KABUPATEN PASURUAN TAHUN 2016

Plague suspect and high flea index is potential transmission of pes. Therefore, it is necessary to conduct rodent and flea observation as an attempt of awareness early occurrence of Extraordinary Events. The purpose of this study was to determine the trap success of flea index. This is a descriptive study by using survey method with cross sectional approach. The study was conducted in Surorowo hamlet, Kayukebek village, Tutur sub district, Pasuruan in February to June 2016. The result showed 29 rats were trapped. The rats found were 17 Rattus tanezumi, 11 Rattus Rattus exulans and one niviventer.The fleas trapped were 17 Xenopsylla cheopis and 3 Stivalius cognatus. 5.67% trap success was carried out in homes, 3.67% in gardens and 0.25% in jungles. Public fleasindex was 0.68; Special flea index of Xenopsylla cheopis was 0.58. From the results above, most of the rats trapped was from Rattus tanezumi type, most trapped fleas was from Xenopsylla cheopis type. Trap success inside and outside homes was categorized as low. Common fleas Index and specific flea index of Xenopsylla cheopis was below standard. There is a need for the provision of number on the trap, increasing the number of traps and training rats catchers. The community is expected to perform trapping independently by providing mousetrap on their own, saving crops in a closed place and providing a closed trash can. Further research on various types of bait can be carried out to know the type of bait rats like. Keywords : trap success and flea index

Opossums and Cat Fleas: New Insights in the Ecology of Murine Typhus in Galveston, Texas.

Murine typhus is an acute undifferentiated febrile illness caused by Rickettsia typhi The classic reservoir (Rattus spp.) and flea vector (Xenopsylla cheopis) were once culprits of murine typhus in the United States. Vector and rodent control efforts have drastically decreased the prevalence of disease, except in a few endemic foci where opossums and cat fleas play a role in transmission. Since 2012, there has been a reemergence of murine typhus in Galveston, TX. We hypothesize that opossums and cat fleas are involved in the transmission of R. typhi in Galveston. To explore this, we sought to find the seroprevalence of typhus group antibodies from opossums. We also sought to find the prevalence of R. typhi in fleas parasitizing these animals. We collected blood from 12 opossums and found that eight (66.7%) had the presence of anti-R. typhi antibodies. All opossums were infested with fleas; a total of 250 Ctenocephalides felis fleas were collected from these animals. Seven opossums (53.8%) were infested with fleas that had molecular evidence of R. typhi infection, while six (46.2%) were infested with fleas that contained Candidatus Rickettsia senegalensis, an organism closely related to R. felis The minimum flea infection rate for R. typhi was 7.0%. The minimum infection rate for Candidatus R. senegalensis was 6.1%. Our study demonstrates that fleas infected with R. typhi parasitize opossums in Galveston. It is therefore likely that opossums and their fleas play a role in the city's recent reemergence of murine typhus.

EFFICACY OF THREE INSECTICIDES ON RAT FLEA (XENOPSYLLA CHEOPIS) INFESTING RODENTS IN GIZA GOVERNORATE, EGYPT.

The extensive use of insecticides in public health and agriculture sectors is the main reason for development of resistance in fleas associated in domestic rodents. The present work was planned to investigate the insecticidal efficacy of Lambda-cyhalothrin, Chlorpyrifos and Fenitrothion against rat flea (Xenopsylla cheopis) infesting rodent species in Giza Governorate, Egypt. The lethal concentration Lc₅₀ and Lc₉₀ of population percent were obtained from the established regression log concentrate-response lines. Data indicated that the values of lethal concentration (Lc₅₀) were 0.293, 1.725 & 2.328% for Lambda-cyhalothrin, chlorpyrifos and Fenitrothion, respectively. The values of lethal concentration (Lc₉₀) were 0.467, 2.839 & 5.197% for Lambda-cyhalothrin, chlorpyrifos and Fenitrothion, respectively.

Surveillance of Trypanosoma Spp of Rodents and Studies in Their Transmission Probability by Fleas in Some Rural Egyptian Areas

A new public health problem arises from animal trypanosomes that afflict human by a disease called atypical human trypanosomiasis. Although humans have an innate protection against most Trypanosoma species, nineteen cases of atypical human trypanosomiasis caused by the animal trypanosome as T. b. brucei, T. vivax, T. congolense, T. evansi and T. lewisi have been recorded. Some of theserecorded cases were transient, six required trypanocidal treatments however two patients died. Rodent trypanosome, T. lewisi is transmitted via ingestion of fleas or their feces containing the infective stage, the metacyclic trypomastigote. Because of the high densities of various species of rodents and their distribution all over the country especially in rural areas, the present work aimed to evaluate the trypanosomiasis among rodents collected from November to March 2016 and study transmission probability by their fleas in some rural areas in Abu Alnomros Center, Giza. The overall trypanosomiasis prevalence among the different rodent species was (21 rats) 24.7%. All the infected rats belonged to Rattus r. spp where the prevalence of infection with Trypanosoma lewisi among that species was very high 51.2% while none of rats belonged to Rattus norvegicus were infected. That may be attributed to the solid immunity gained by the R. norvegicus where most of the collected norvegicus were aged and weighed more than 200 grams. There was an inverse significant correlation between the densities of parasites and the weights of the losts. The rat which recorded the highest parasite density (60,000 parasites/microliter) was a female Rattus r. captured indoor (inside house). As to sex of Rattus rattus spp no significant difference was found between males and females in trypanosomiasis. Also there was no significant correlation between the densities of parasites and the number of white blood cells among Rattus rattus spp. All positive rats were collected indoors (from houses) and all the rats which were captured from outdoors (farms) were negative for T. lewisi. The difference between infections with trypanosomiasis among rats inhabited the houses and that found in farms was highly significant. Only two species of fleas were found on rats, Xenopsylla cheopis and Leptopsylla segnis. The oriental fleas, X cheopis, were found mainly on R. norvegicus where 57.5% of R. norvegicus were positive for X cheopis while only one rat was positive for L. segnis. On other hand the rat fleas, L. segnis, were found mainly on Rattus rattus spp where 39% of these rats were positive for L. segnis. The present work revealed a significant correlation between the infection with T. lewisi, and the presence of L. segnis on the rats however that correlation regarding X. cheopis was not significant.

Effect of temperature and relative humidity on the development times and survival of Synopsyllus fonquerniei and Xenopsylla cheopis, the flea vectors of plague in Madagascar.

BackgroundPlague, a zoonosis caused by Yersinia pestis, is found in Asia, the Americas but mainly in Africa, with the island of Madagascar reporting almost one third of human cases worldwide. In the highlands of Madagascar, plague is transmitted predominantly by two flea species which coexist on the island, but differ in their distribution. The endemic flea, Synopsyllus fonquerniei, dominates flea communities on rats caught outdoors, while the cosmopolitan flea, Xenopsylla cheopis, is found mostly on rats caught in houses. Additionally S. fonquerniei seems restricted to areas above 800 m. Climatic constraints on the development of the two main vectors of plague could explain the differences in their distribution and the seasonal changes in their abundance. Here we present the first study on effects of temperature and relative humidity on the immature stages of both vector species.MethodsWe examined the two species’ temperature and humidity requirements under experimental conditions at five different temperatures and two relative humidities. By employing multivariate and survival analysis we established the impact of temperature and relative humidity on development times and survival for both species. Using degree-day analysis we then predicted the average developmental threshold for larvae to reach pupation and for pupae to complete development under each treatment. This analysis was undertaken separately for the two relative humidities and for the two species.ResultsDevelopment times and time to death differed significantly, with the endemic S. fonquerniei taking on average 1.79 times longer to complete development and having a shorter time to death than X. cheopis under adverse conditions with high temperature and low humidity. Temperature had a significant effect on the development times of flea larvae and pupae. While humidity did not affect the development times of either species, it did influence the time of death of S. fonquerniei. Using degree-day analysis we estimated an average developmental threshold of 9 °C for S. fonquerniei, and 12.5 °C for X. cheopis.ConclusionsWhile many vector-borne diseases are limited to warm, low-lying regions, plague in Madagascar is unusual in being most prevalent in the cool, highland regions of the country. Our results point towards the possibility that this is because the endemic flea vector, S. fonquerniei, is better adapted to cool temperatures than the exotic flea vector, X. cheopis. Future warming caused by climate change might reduce the area suitable for S. fonquerniei and may thus reduce the incidence of plague in Madagascar.

Plague-Carrying Fleas Resist Insecticides

Despite decades of work trying to control plague, the illness is still a major health concern in Madagascar. A 2014 outbreak in that country infected more than 335 people at its peak and claimed at least 79 lives, according to the World Health Organization. Plague is primarily transmitted to people from rats via the Oriental rat flea Xenopsylla cheopis. Efforts to keep the disease in check focus on controlling the flea population with insecticides. But a study by Adélaïde Miarinjara and Sébastien Boyer, of the Pasteur Institute of Madagascar, reveals that of 12 standard insecticides, six—including the most commonly used insecticide deltamethrin—are ineffective against local fleas (PLOS Neglected Trop. Dis. 2016, DOI: 10.1371/journal.pntd.0004414). Miarinjara and Boyer studied eight flea populations from around the island and found that only one insecticide—dieldrin—was 100% effective on all populations. Dieldrin is an organochlorine compound that’s toxic to mammals and known to accumulate in the

Feeding Behavior Modulates Biofilm-Mediated Transmission of Yersinia pestis by the Cat Flea, Ctenocephalides felis.

BackgroundThe cat flea, Ctenocephalides felis, is prevalent worldwide, will parasitize animal reservoirs of plague, and is associated with human habitations in known plague foci. Despite its pervasiveness, limited information is available about the cat flea’s competence as a vector for Yersinia pestis. It is generally considered to be a poor vector, based on studies examining early-phase transmission during the first week after infection, but transmission potential by the biofilm-dependent proventricular-blocking mechanism has never been systematically evaluated. In this study, we assessed the vector competence of cat fleas by both mechanisms. Because the feeding behavior of cat fleas differs markedly from important rat flea vectors, we also examined the influence of feeding behavior on transmission dynamics.Methodology/Principal FindingsGroups of cat fleas were infected with Y. pestis and subsequently provided access to sterile blood meals twice-weekly, 5 times per week, or daily for 4 weeks and monitored for infection, the development of proventricular biofilm and blockage, mortality, and the ability to transmit. In cat fleas allowed prolonged, daily access to blood meals, mimicking their natural feeding behavior, Y. pestis did not efficiently colonize the digestive tract and could only be transmitted during the first week after infection. In contrast, cat fleas that were fed intermittently, mimicking the feeding behavior of the efficient vector Xenopsylla cheopis, could become blocked and regularly transmitted Y. pestis for 3–4 weeks by the biofilm-mediated mechanism, but early-phase transmission was not detected.ConclusionsThe normal feeding behavior of C. felis, more than an intrinsic resistance to infection or blockage by Y. pestis, limits its vector competence. Rapid turnover of midgut contents results in bacterial clearance and disruption of biofilm accumulation in the proventriculus. Anatomical features of the cat flea foregut may also restrict transmission by both early-phase and proventricular biofilm-dependent mechanisms.

Orange County Vector Control and the County’s Feral Cat TNR Program: Ne’er the Twain Shall Meet?

In 2006, flea-borne rickettsiosis (flea-borne typhus), a zoonotic disease caused by either Rickettsia typhi or R. felis and transmitted primarily by two flea species, the Oriental rat flea and the cat flea, re-emerged as an important vector-borne disease in Orange County, California. The Orange County Mosquito and Vector Control District (OC Vector Control) has investigated 142 human cases of flea-borne rickettsiosis. Results of these investigations have established a link with Rickettsia-infected cat fleas, opossums, feral cats, and disease transmission to humans; no cases have been associated with rats and their fleas. Since initiation of a Trap-Neuter-Return (TNR) Program by Orange County (OC) Animal Care in 2009, OC Vector Control has been working with OC Animal Care to minimize the potential public health risks associated with the TNR Program. Interagency discussions have led OC Animal Care to prohibit the release of TNR cats at locations with a high risk for zoonotic disease transmission to humans, such as schools, parks, and health care facilities, and also to disclose the release sites to OC Vector Control. OC Animal Care has not agreed to OC Vector Control’s request for a zoonotic disease review of its TNR Program, nor has it provided a procedural manual to verify the verbal agreements reached by the two agencies. In agreement with OC Vector Control’s concerns, an investigation in 2015 by the Orange County Grand Jury of OC Animal Care’s TNR Program recognized the Program’s potential to increase zoonotic disease transmission to the public and other wildlife. We discuss the conflicting views arising from two governmental agencies, which perceive the zoonotic diseases risk associated with a TNR program at significantly different thresholds of concern.

Cofeeding intra- and interspecific transmission of an emerging insect-borne rickettsial pathogen.

Cat fleas (Ctenocephalides felis) are known as the primary vector and reservoir of Rickettsia felis, the causative agent of flea‐borne spotted fever; however, field surveys regularly report molecular detection of this infectious agent from other blood‐feeding arthropods. The presence of R. felis in additional arthropods may be the result of chance consumption of an infectious bloodmeal, but isolation of viable rickettsiae circulating in the blood of suspected vertebrate reservoirs has not been demonstrated. Successful transmission of pathogens between actively blood‐feeding arthropods in the absence of a disseminated vertebrate infection has been verified, referred to as cofeeding transmission. Therefore, the principal route from systemically infected vertebrates to uninfected arthropods may not be applicable to the R. felis transmission cycle. Here, we show both intra‐ and interspecific transmission of R. felis between cofeeding arthropods on a vertebrate host. Analyses revealed that infected cat fleas transmitted R. felis to naïve cat fleas and rat fleas (Xenopsylla cheopis) via fleabite on a nonrickettsemic vertebrate host. Also, cat fleas infected by cofeeding were infectious to newly emerged uninfected cat fleas in an artificial system. Furthermore, we utilized a stochastic model to demonstrate that cofeeding is sufficient to explain the enzootic spread of R. felis amongst populations of the biological vector. Our results implicate cat fleas in the spread of R. felis amongst different vectors, and the demonstration of cofeeding transmission of R. felis through a vertebrate host represents a novel transmission paradigm for insect‐borne Rickettsia and furthers our understanding of this emerging rickettsiosis.

The Distribution and Diversity of Bartonella Species in Rodents and Their Ectoparasites across Thailand.

Our study highlights the surveillance of Bartonella species among rodents and their associated ectoparasites (ticks, fleas, lice, and mites) in several regions across Thailand. A total of 619 rodents and 554 pooled ectoparasites (287 mite pools, 62 flea pools, 35 louse pools, and 170 tick pools) were collected from 8 provinces within 4 regions of Thailand. Bandicota indica (279), Rattus rattus (163), and R. exulans (96) were the most prevalent species of rats collected in this study. Real-time PCR assay targeting Bartonella-specific ssrA gene was used for screening and each positive sample was confirmed by PCR using nuoG gene. The prevalence of Bartonella DNA in rodent (around 17%) was recorded in all regions. The highest prevalence of Bartonella species was found in B. savilei and R. rattus with the rate of 35.7% (5/14) and 32.5% (53/163), respectively. High prevalence of Bartonella-positive rodent was also found in B. indica (15.1%, 42/279), and R. norvegicus (12.5%, 5/40). In contrast, the prevalence of Bartonella species in ectoparasites collected from the rats varied significantly according to types of ectoparasites. A high prevalence of Bartonella DNA was found in louse pools (Polyplax spp. and Hoplopleura spp., 57.1%) and flea pools (Xenopsylla cheopis, 25.8%), while a low prevalence was found in pools of mites (Leptotrombidium spp. and Ascoschoengastia spp., 1.7%) and ticks (Haemaphysalis spp., 3.5%). Prevalence of Bartonella DNA in ectoparasites collected from Bartonella-positive rodents (19.4%) was significantly higher comparing to ectoparasites from Bartonella-negative rodents (8.7%). The phylogenetic analysis of 41 gltA sequences of 16 Bartonella isolates from rodent blood and 25 Bartonella-positive ectoparasites revealed a wide range of diversity among Bartonella species with a majority of sequences (61.0%) belonging to Bartonella elizabethae complex (11 rodents, 1 mite pool, and 5 louse pools), while the remaining sequences were identical to B. phoceensis (17.1%, 1 mite pool, 5 louse pools, and 1 tick pool), B. coopersplainensis (19.5%, 5 rodents, 1 louse pool, and 2 tick pools), and one previously unidentified Bartonella species (2.4%, 1 louse pool).

Risk assessments and control strategies of plague in five key surveillance counties, Zhejiang province

To analyze the epidemiology data on plague in five counties in Zhejiang province and to evaluate the risk of plague in theses areas. We selected five monitoring stations as a risk assessment (Qingyuan county, Longquan city, Yiwu city, Wencheng county, and Ruian city) in Zhejiang province where the plague epidemic more serious in the history. At least one constant site and 1-4 variable sites where plague occurred in history were selected for monitoring. We collected the five counties (cities) surveillance data of indoor rat density, indoor Rattus flavipectus density, the Xenopsylla cheopis index of rat, the Xenopsylla cheopis index of Rattus flavipectus in 1995-2014. Isolation of Yersinia pestis was conducted among 171,201 liver samples and F1 antibody were detected among 228,775 serum samples. Risk matrix, Borda count method, and Delphi approach were conducted to assess risk of the plague of five counties (cities) in Zhejiang province. Indoor rat density in Qingyuan county, Longquan city, Yiwu city, Wencheng county, Ruian city was 1.58%-5.50%, 1.13%-9.76%, 0.56%-3.67%, 2.83%-16.08%, 7.16%-15.96%, respectively; Indoor Rattus flavipectus density of five counties (cities) was 0.08%-2.23%, 0-2.02%, 0-0.54%, 0.71%-5.58%, 0.55%-4.92%, respectively. The Xenopsylla cheopis index of rat in Qingyuan county and Wencheng county was 0.011-0.500 and 0.015-0.227, respectively; The Xenopsylla cheopis index of Rattus flavipectus of Qingyuan county and Wencheng county was 0.119-3.412 and 0.100-1.430, respectively; Ruian City and Yiwu city cannot collected Xenopsylla cheopis, Long quan city only collected the Xenopsylla cheopis index of rat in the five years. Yersinia pestis were not isolated in five counties (cities).There were 3 Apodemus agrarius samples positive of plague F1 antibody test, in Longquan city and Yiwu city in 2005. Borda count method to assess the Longquan city, Yiwu (Borda point were both 321) plague risk was higher than three other regions; Delphi approach to evaluation five counties (cities) belong to the plague had a lower risk areas, according to the level of risk score (Pf) Longquan city and Yiwu (Pf was 0.314, 0.292, respectively) plague risk were higher than three other regions (Pf were all 0.292). The main host and media were lower in five key plague surveillance counties (cities) of Zhejiang province; The result of Borda count method and Delphi approach for risk assessment indicated that endogenous plague recrudescence was at lower level, but Longquan city and Yiwu city risk were higher than other counties (cities).

Evaluation of the Role of the opgGH Operon in Yersinia pseudotuberculosis and Its Deletion during the Emergence of Yersinia pestis.

The opgGH operon encodes glucosyltransferases that synthesize osmoregulated periplasmic glucans (OPGs) from UDP-glucose, using acyl carrier protein (ACP) as a cofactor. OPGs are required for motility, biofilm formation, and virulence in various bacteria. OpgH also sequesters FtsZ in order to regulate cell size according to nutrient availability. Yersinia pestis (the agent of flea-borne plague) lost the opgGH operon during its emergence from the enteropathogen Yersinia pseudotuberculosis. When expressed in OPG-negative strains of Escherichia coli and Dickeya dadantii, opgGH from Y. pseudotuberculosis restored OPGs synthesis, motility, and virulence. However, Y. pseudotuberculosis did not produce OPGs (i) under various growth conditions or (ii) when overexpressing its opgGH operon, its galUF operon (governing UDP-glucose), or the opgGH operon or Acp from E. coli. A ΔopgGH Y. pseudotuberculosis strain showed normal motility, biofilm formation, resistance to polymyxin and macrophages, and virulence but was smaller. Consistently, Y. pestis was smaller than Y. pseudotuberculosis when cultured at ≥ 37°C, except when the plague bacillus expressed opgGH. Y. pestis expressing opgGH grew normally in serum and within macrophages and was fully virulent in mice, suggesting that small cell size was not advantageous in the mammalian host. Lastly, Y. pestis expressing opgGH was able to infect Xenopsylla cheopis fleas normally. Our results suggest an evolutionary scenario whereby an ancestral Yersinia strain lost a factor required for OPG biosynthesis but kept opgGH (to regulate cell size). The opgGH operon was presumably then lost because OpgH-dependent cell size control became unnecessary.

A new cellular target for Yersinia pestis.

Yersinia pestis is a Gram-negative, facultative anaerobic, rod-shaped and non-spore-forming coccobacillus, which is better known as the causative agent of the bubonic plague. Although this deadly disease is better known to the general public through history books, Y. pestis is still endemic in many areas of the world, and concerns exist about its potential use as a bioterrorism agent. The cycle of transmission of Y. pestis involves several species of rodents and an arthropod vector (the flea Xenopsylla cheopis), which transmits the bacteria to humans during feeding. In the flea midgut, Y. pestis grows in the form of a biofilm that blocks the gastrointestinal system of the arthropod,1 causing the flea to regurgitate and transfer the bacteria into the host. At this point, the bacteria are carried from the skin to the lymph nodes where they multiply extraordinarily fast and, within 1–3 days, lead to the formation of buboes. Buboes are the clinical hallmark of the disease and are basically swollen, edematous, hemorrhagic and necrotic lymph nodes resulting from uncontrolled bacterial proliferation.2

Molecular detection of zoonotic bartonellae (B. henselae, B. elizabethae and B. rochalimae) in fleas collected from dogs in Israel.

Fleas represent an acknowledged burden on dogs worldwide. The characterization of flea species infesting kennel dogs from two localities in Israel (Rehovot and Jerusalem) and their molecular screening for Bartonella species (Rhizobiales: Bartonellaceae) was investigated. A total of 355 fleas were collected from 107 dogs. The fleas were morphologically classified and molecularly screened targeting the Bartonella 16S-23S internal transcribed spacer (ITS). Of the 107 dogs examined, 80 (74.8%) were infested with Ctenocephalides canis (Siphonaptera: Pulicidae), 68 (63.6%) with Ctenocephalides felis, 15 (14.0%) with Pulex irritans (Siphonaptera: Pulicidae) and one (0.9%) with Xenopsylla cheopis (Siphonaptera: Pulicidae). Fleas were grouped into 166 pools (one to nine fleas per pool) according to species and host. Thirteen of the 166 flea pools (7.8%) were found to be positive for Bartonella DNA. Detected ITS sequences were 99-100% similar to those of four Bartonella species: Bartonella henselae (six pools); Bartonella elizabethae (five pools); Bartonella rochalimae (one pool), and Bartonella bovis (one pool). The present study indicates the occurrence of a variety of flea species in dogs in Israel; these flea species are, in turn, carriers of several zoonotic Bartonella species. Physicians, veterinarians and public health workers should be aware of the presence of these pathogens in dog fleas in Israel and preventive measures should be implemented.

Efficacy of certain insecticides against rat flea (Xenopsylla cheopis) among rodent species in Cairo Governorate, Egypt.

The efficacy of malathion, chlorpyrifos and deltamethrine to oriental rat flea, Xenopsylla cheopis associated different rodent species was carried out in Cairo Governorates. The results indicated that the LC50 values were 1.972, 1.023 and 0.185 % for Malathion, Chlorpyrifos and Deltamethrine, respectively. The values of Lc90 were 4.452, 2.269 & 0.456% for the three insecticides respectively. Data also indicated that deltamethrine was effective on fleas than malathion and chlorpyrifos. The slope function was 3.625, 3.70 & 3.267, respectively.

Preliminary Survey of Ectoparasites and Associated Pathogens from Norway Rats in New York City.

The Norway rat (Rattus norvegicus) is a reservoir of many zoonotic pathogens and lives in close proximity to humans in urban environments. Human infection with rodent-borne disease occurs either directly through contact with a rat or its excreta, or indirectly via arthropod vectors such as fleas and ticks. Here, we report on the diversity and abundance of ectoparasitic arthropod species and associated pathogenic bacteria from 133 Norway rats trapped over a 10-mo period in Manhattan, New York, NY. Norway rats were host to the tropical rat mite [Ornithonyssus bacoti (Hirst)], the spiny rat mite (Laelaps echidnina Berlese), Laelaps nuttalli Hirst, the spined rat louse [Polyplax spinulosa (Burmeister)], and the Oriental rat flea [(Xenopsylla cheopis) (Rothschild)], with an average of 1.7 species per individual. A flea index of 4.1 X. cheopis was determined, whereas previous studies in New York City reported 0.22 fleas per rat. Multiple species of pathogenic Bartonella were identified from Oriental rat fleas that were related to Bartonella tribocorum, Bartonella rochalimae, and Bartonella elizabethae. However, no evidence of Yersinia pestis or Rickettsia spp. infection was detected in fleas. The identification of multiple medically important ectoparasite species in New York City underscores the need for future efforts to fully characterize the diversity and distribution of ectoparasites on Norway rats, and assess the risk to humans of vector-borne disease transmission.

We are connected: flea–host association networks in the plague outbreak focus in the Rift Valley, northern Tanzania

Context Plague is a serious health problem in northern Tanzania, with outbreaks since 2008 in two districts located in Rift Valley. There is dearth of knowledge on diversity of small mammal and flea fauna occurring in this plague focus. Knowledge on interactions between fleas and rodent species that harbour the plague bacterium, Yersinia pestis, is important for developing strategies for control and prevention of plague. Aims This study aims to show how rodents and fleas are associated with each other in the plague focus. Methods Animals were trapped bimonthly from 2009 to 2012 in different habitats. The fur of animals was brushed to collect fleas, which were identified and quantified. Network analysis methods, randomisation and rarefaction curves were used to show how hosts and fleas are associated. Key results Thirteen species of rodents were associated with 26 species of fleas of which Dinopsyllus lypusus, Xenopsylla brasiliensis and X. cheopis are confirmed efficient vectors of Y. pestis. Randomisation and rarefaction curves established that Lophuromys flavopunctatus had significantly higher flea species richness (n = 9) than did all other hosts, whereas Xenopsylla cheopis and Dinopsyllus spp. showed greater host species richness than did other species of fleas. There was no significant correlation between host sex and flea abundance (χ2 = 0.8, d.f. = 6, P = 0.371), but significant differences between reproductive states (adults had more fleas than did subadults) were observed, which probably reflected typical positive correlation between size and flea abundance (χ2 = 4.1955, d.f. = 1, P = 0.040). Conclusions The plague outbreak focus in northern Tanzania has a diverse fauna of rodents and fleas with multiple patterns of association and connectivity. Implications Existence of diverse populations of rodents associated with a large number of flea species, some of which are efficient plague vectors, increases the potential for persistence and transmission of plague to humans in northern Tanzania.

LPS modification promotes maintenance of Yersinia pestis in fleas.

Yersinia pestis, the causative agent of plague, can be transmitted by fleas by two different mechanisms: by early-phase transmission (EPT), which occurs shortly after flea infection, or by blocked fleas following long-term infection. Efficient flea-borne transmission is predicated upon the ability of Y. pestis to be maintained within the flea. Signature-tagged mutagenesis (STM) was used to identify genes required for Y. pestis maintenance in a genuine plague vector, Xenopsylla cheopis. The STM screen identified seven mutants that displayed markedly reduced fitness in fleas after 4 days, the time during which EPT occurs. Two of the mutants contained insertions in genes encoding glucose 1-phosphate uridylyltransferase (galU) and UDP-4-amino-4-deoxy-l-arabinose-oxoglutarate aminotransferase (arnB), which are involved in the modification of lipid A with 4-amino-4-deoxy-l-arabinose (Ara4N) and resistance to cationic antimicrobial peptides (CAMPs). These Y. pestis mutants were more susceptible to the CAMPs cecropin A and polymyxin B, and produced lipid A lacking Ara4N modifications. Surprisingly, an in-frame deletion of arnB retained modest levels of CAMP resistance and Ara4N modification, indicating the presence of compensatory factors. It was determined that WecE, an aminotransferase involved in biosynthesis of enterobacterial common antigen, plays a novel role in Y. pestis Ara4N modification by partially offsetting the loss of arnB. These results indicated that mechanisms of Ara4N modification of lipid A are more complex than previously thought, and these modifications, as well as several factors yet to be elucidated, play an important role in early survival and transmission of Y. pestis in the flea vector.

Xenopsylla cheopis (Siphonaptera: Pulicidae) susceptibility to Deltamethrin in Madagascar.

The incidence of bubonic plague in Madagascar is high. This study reports the susceptibility of 32 different populations of a vector, the flea Xenopsylla cheopis (Siphonaptera: Pulicidae), to the insecticide Deltamethrin. Despite the use of Deltamethrin against fleas, plague epidemics have re-emerged in Madagascar. The majority of the study sites were located in the Malagasy highlands where most plague cases have occurred over the last 10 years. X. cheopis fleas were tested for susceptibility to Deltamethrin (0.05%): only two populations were susceptible to Deltamethrin, four populations were tolerant and 26 populations were resistant. KD50 (50% Knock-Down) and KD90 (90% Knock-Down) times were determined, and differed substantially from 9.4 to 592.4 minutes for KD50 and 10.4 min to 854.3 minutes for KD90. Susceptibility was correlated with latitude, but not with longitude, history of insecticide use nor date of sampling. Combined with the number of bubonic plague cases, our results suggest that an immediate switch to an insecticide other than Deltamethrin is required for plague vector control in Madagascar.

Spatiotemporal variations of the incidence of the fleas (Siphonaptera) on domestic small mammals in the city of Cotonou, Benin.

Objectives : A survey of domestic small mammals and their associated fleas was conducted in Cotonou during the years 2008, 2009 and 2010. The objective of this study was to evaluate the potential role of small mammals in the transmission of anthropozoonosis. Methodology and Results: A total of 1,402 domestic small mammals were captured in 54 stations using methods following Houemenou (2006). The most abundant small mammals were, Rattus rattus (black rat) (63.7%), Mastomys sp. (multimammate rat) (11.84%) , Rattus norvegicus (brown rat) (11.48%) and Crocidura olivieri (7.85%). Among these rodents, 364 individuals were found with ectoparasites, and 886 fleas were collected (flea index 0.63), the most common flea being Xenopsylla cheopis (rat flea) (97.2%). This species was found in all areas of the city and infested all small mammal species. The Pulicidae prevalence (26%) showed important variations, with relatively low and significantly higher prevalence during the rainy and dry seasons, respectively. Conclusions and application of findings: Small mammal community in Cotonou was dominated by Rattus rattus and fleas by Xenopsylla cheopis . Due to the presence of a seaport of paramount importance, Cotonou town was not away from importation by sea transport of zoonotic rats (shelter ships calling at the port of Cotonou, from all continents). To date, in Cotonou there is lacking information on pathogenic agents hosted by the small mammals and their ectoparasites. Therefore, awareness of the authorities on the zoonotic risk of small mammals for the human population is necessary. The authorities of the Port Autonome de Cotonou must increase the screening of ships, which arrive at Cotonou to avoid zoonotic rodent importation. The Ministry of Human Health in Benin must sensitize the populations at high risk of the rodent transmitted diseases. Further studies are needed to detect the different animal reservoirs of these pathogenic agents.