Rat Flea Xenopsylla Cheopis Research Articles

First case of Ehrlichia canis infection in the common pipistrelle bat (Pipistrellus pipistrellus)

AbstractThe present case report investigates the infection of a common pipistrelle bat (Pipistrellus pipistrellus) with various vector‐borne bacteria in northern Tunisia. The examined bat was found to be infested with the rat flea Xenopsylla cheopis and the specific bat mites Macronyssus spp. Spleen, liver and heart samples and ectoparasites were tested by polymerase chain reaction (PCR) assays targeting major vector‐borne bacteria. Only DNA of Anaplasmataceae bacteria was detected in spleen, liver and flea samples. Phylogenetic analysis of the 16S rRNA sequence obtained in this study suggested that this bat was infected with a specific Ehrlichia canis strain previously detected in domestic and wild canids and their associated ticks. We reported here the first case of infection with Ehrlichia canis in a bat. Hence, further studies must be undertaken to elucidate the potential role of bats in the epidemiology of this vector‐borne bacteria.

Ectoparasites of some wild rodents /shrews captured from Scrub typhus reported areas in Tamil Nadu, India

ABSTRACT Scrub typhus cases have been reported in Madurai, but very little is known about the distributionpatterns of ectoparasites on rodents and shrews in the Madurai district. To determine the chigger vectors of scrub typhus, Rattus rattus, R. norvegicus, Mus musculus, and Suncus murinus were collected from these areas and the prevalence and mean intensity were calculated as 40% & 14.8 ± 3.9 for chiggers. Mites were collected from burrow soil samples. The chiggers Leptotrombidium deliense and Schoengastiella ligula, both known as vectors for the transmission of Orientia tsutsugamushi in India, were recorded in this study. In addition, Rhipicephalus sanguineus ticks, a putative vector of Indian tick typhus and canine ehrlichiosis, and the oriental rat flea Xenopsylla cheopis, a known vector of the plague pathogen Yersinia pestis, were also reported. They have high zoonotic potential and have been implicated in the transmission of the aforementioned emerging zoonotic diseases. Parapathi is a typical scrub typhus village with lots of rat burrows found around many houses and many reported scrub typhus cases. Rodents and shrews collected from these areas harboured vectors of medical and veterinary importance and act as endemic reservoir for transmitting zoonotic diseases which requires urgent attention for its control. http://www. zoobank.org/urn:lsid:zoobank.org:pub:5EFDD3BC-B9BA-4595-A02E-8AAEB4E7D755

Transcriptomic profiling of the digestive tract of the rat flea, Xenopsylla cheopis, following blood feeding and infection with Yersinia pestis.

Yersinia pestis, the causative agent of plague, is a highly lethal pathogen transmitted by the bite of infected fleas. Once ingested by a flea, Y. pestis establish a replicative niche in the gut and produce a biofilm that promotes foregut colonization and transmission. The rat flea Xenopsylla cheopis is an important vector to several zoonotic bacterial pathogens including Y. pestis. Some fleas naturally clear themselves of infection; however, the physiological and immunological mechanisms by which this occurs are largely uncharacterized. To address this, RNA was extracted, sequenced, and distinct transcript profiles were assembled de novo from X. cheopis digestive tracts isolated from fleas that were either: 1) not fed for 5 days; 2) fed sterile blood; or 3) fed blood containing ~5x108 CFU/ml Y. pestis KIM6+. Analysis and comparison of the transcript profiles resulted in identification of 23 annotated (and 11 unknown or uncharacterized) digestive tract transcripts that comprise the early transcriptional response of the rat flea gut to infection with Y. pestis. The data indicate that production of antimicrobial peptides regulated by the immune-deficiency pathway (IMD) is the primary flea immune response to infection with Y. pestis. The remaining infection-responsive transcripts, not obviously associated with the immune response, were involved in at least one of 3 physiological themes: 1) alterations to chemosensation and gut peristalsis; 2) modification of digestion and metabolism; and 3) production of chitin-binding proteins (peritrophins). Despite producing several peritrophin transcripts shortly after feeding, including a subset that were infection-responsive, no thick peritrophic membrane was detectable by histochemistry or electron microscopy of rat flea guts for the first 24 hours following blood-feeding. Here we discuss the physiological implications of rat flea infection-responsive transcripts, the function of X. cheopis peritrophins, and the mechanisms by which Y. pestis may be cleared from the flea gut.

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

Plague: The Disease,Yersinia pestisand its Genome

Plague is a highly virulent, vector-borne disease of ancient antecedents, transmitted from members of the family Rodentia, through the bites of infected fleas. The disease, caused by the bacterium Yersinia pestis, presents itself in septicaemic, bubonic and pneumonic forms. The rat flea Xenopsylla cheopis is most often implicated in transmission. The plague remains one of the most dreaded infectious diseases, which has raised its head in western, northern and southern regions in the last few decades, being a category ‘A’ critical agent with a significant threat to public health and national security. Rapid antigen detection or nucleic acid-based molecular tests for plague are not widely available. Modern immunoprophylactic regimes for pre- and postgeneration vaccination are needed. Complete genome sequences unveiled for all four biotypes and other strains/isolates recently will help scientists gain insights into the genomic rearrangement and pathogenicity of the organism.

Molecular detection of Rickettsia typhi and Rickettsia felis in fleas from Algeria

With the exception of the rat flea Xenopsylla cheopis and Yersinia pestis, the agent of plague, fleas and human flea-borne infections have been scarcely studied in Algeria [1]. Murine typhus, a typhus group rickettsiosis caused by Rickettsia typhi and transmitted by X. cheopis, is also known to occur in Algeria, but cases are poorly documented [2,3]. However, recently, fleas collected in Algeria, in the district of Oran, between July and September 2003 (Ctenocephalides canis from rodents, and Archeopsylla erinacei from hedgehogs) were tested by PCR for the presence of Rickettsia spp., and were shown to harbour an emerging pathogen, Rickettsia felis [4]. In this work, in an effort to identify the possible aetiological agents and vectors for rickettsiosis affecting humans in Algeria, we analysed more fleas collected from rodents trapped in peridomestic areas for evidence of rickettsial infection.

Studies of Vector Competency and Efficiency of North American Fleas for <I>Yersinia pestis</I>: State of the Field and Future Research Needs

The etiological agent of plague, Yersinia pestis, is most commonly transmitted by the bite of infectious fleas. To date, at least 28 flea species occurring in North America have been experimentally confirmed as vectors of Y. pestis. Transmission efficiency differs among species and also between different studies of a single species. These differences may, however, in large part reflect nonstandardized experimental conditions used during the first half of the 20th century when such studies were conducted in response to the rapid spread of Y. pestis across the western United States after its introduction at the beginning of this century. The majority of these early transmission studies focused on the blocked flea mechanism of transmission, which typically does not occur until > 2-3 wk after the flea becomes infected. Recent studies have challenged the paradigm that Y. pestis is usually spread by blocked fleas by demonstrating that numerous flea species, including the oriental rat flea Xenopsylla cheopis, which was the focus of the early classical studies on blocked flea transmission, are capable of"early-phase" transmission during the first few days after becoming infected and before a complete blockage can form. The aims of this review are to 1) summarize Y. pestis vector competency and efficiency studies for fleas occurring in North America, 2) discuss the implications of the results of these studies for our understanding of the dynamics of plague epizootics, 3) demonstrate why older transmission studies need to be repeated using a standardized experimental system, and 4) outline future directions for studies of fleas as vectors of Y. pestis.

Acute oral toxicity of Yersinia pseudotuberculosis to fleas: implications for the evolution of vector-borne transmission of plague

Yersinia pestis diverged from Yersinia pseudotuberculosis</= 20 000 years ago, during which time it evolved to be transmitted by fleas. In comparing the ability of these closely related species to infect the rat flea Xenopsylla cheopis, we found that Y. pseudotuberculosis, unlike Y. pestis, is orally toxic to fleas. Fleas showed signs of acute toxicity, including diarrhoea, immediately after feeding on blood containing Y. pseudotuberculosis in response to protein toxin(s) produced by the bacteria. Adherence of Y. pseudotuberculosis to the midgut and large intracellular vacuoles in midgut epithelial cells were detected during the first 24 h after infection. The insect pathogen Photorhabdus luminescens and its TcdA1 and TcdB1-TccC1 insecticidal toxin complexes were similarly toxic to fleas, implicating the toxin complex (tc) genes also present in Yersinia species. However, the Y. pestis and Y. pseudotuberculosis TcaAB and TcaC-TccC proteins were non-toxic to fleas, and Y. pseudotuberculosis mutants deleted of tc genes retained acute toxicity. Our results indicate that loss of one or more insect gut toxins was a critical step in the recent evolution of flea-borne transmission in the genus Yersinia. Changes in the tc insecticidal genes do not appear to have been responsible, but may have had other effects on Yersinia-flea interactions.

Poor Vector Competence of Fleas and the Evolution of Hypervirulence inYersinia pestis

Population genetics and comparative genomics analyses of the pathogenic Yersinia species have indicated that arthropodborne transmission is an evolutionarily recent adaptation in Yersinia pestis, the agent of plague. We show that the infectivity of Y. pestis to its most proficient vector, the rat flea Xenopsylla cheopis, and subsequent transmission efficiency are both low. The poor vector competence of fleas likely imposed selective pressure that favored the emergence and continued maintenance of a hypervirulent Y. pestis clone. In particular, the rapidly fatal gram-negative sepsis that typifies plague is a consequence of the high threshold bacteremia level that must be attained to complete the transmission cycle. Epidemiological modeling predicts that, to compensate for a relatively short period of infectivity of the mammalian host for the arthropod vector, plague epizootics require a high flea burden per host, even when the susceptible host population density is high.

Pharaonic Egypt and the origins of plague

AbstractAim This paper examines the possibility that bubonic plague was a disease endemic in the wild rodent population of Egypt and East Africa.Location The study focuses on Egypt and the Nile Valley during the Pharaonic period.Methods This paper presents a hypothesis based on archaeoentomological, archaeozoological and biogeographical information on the insect and small mammal species involved in the spread of plague, as well as relevant information from early literary sources.Results The primary host for the rat flea Xenopsylla cheopis is the Nile rat, Arvicanthis niloticus. Urbanization and the Nile floods brought into contact humans and the Nile rat and its ectoparasite, Xenopsylla cheopis, which was able to move to a newly introduced host the synanthropic Rattus rattus. The existence of large numbers of human fleas and squalid conditions from the Workmens’ Village at Amarna, evidence for nile rats and black rats from Pharaonic sites and descriptions of an epidemic disease in the Amarna letters, the Hittitic archives and the Ebers papyrus with references to swelling buboes, present a new scenario for the origins of the disease.Main conclusions Most modern researchers have regarded the origins of bubonic plague as a disease of Central Asiatic rodents. Here, I examine the evidence for plague in Egypt, and suggest that the bacillus Yersinia pestis was primarily a disease of the Nile rat, Arvicanthis niloticus, which only achieved epidemic proportions when its vector, the tropical rat flea, Xenopsylla cheopis, was able to make the jump to a new host, the black or ship rat, Rattus rattus, introduced from India or indirectly via Mesopotamia during the Pharaonic period. Synanthropy and a high death rate in the new host lead to frequent transfer to human populations and stochastic waves of pandemics.

Role of Yersinia murine toxin in survival of Yersinia pestis in the midgut of the flea vector.

Transmission by flea bite is a relatively recent adaptation that distinguishes Yersinia pestis, the plague bacillus, from closely related enteric bacteria. Here, a plasmid-encoded phospholipase D (PLD), previously characterized as Yersinia murine toxin (Ymt), was shown to be required for survival of Y. pestis in the midgut of its principal vector, the rat flea Xenopsylla cheopis. Intracellular PLD activity appeared to protect Y. pestis from a cytotoxic digestion product of blood plasma in the flea gut. By enabling colonization of the flea midgut, acquisition of this PLD may have precipitated the transition of Y. pestis to obligate arthropod-borne transmission.

Ultrastructure of the rectal sac, the site of water vapour uptake from the atmosphere in larvae of the oriental rat flea Xenopsylla cheopis

A portion of the hindgut of Xenopsylla cheopis larvae, the rectal sac, is extraordinarily enlarged and differentiated into a specialized organ displaying well-elaborated transporting epithelia. This organ is unique among insect recta because of gutter-like arrangement of two ultrastructurally distinct cell types with an asymmetrical position of the membranemitochondria complexes. The cells of the dorsal gutter have highly folded apical plasma membranes on the lumen side. The cells of the ventral gutter show deep infoldings of the basal plasma membrane on the haemolymph side. Less elaborate folds originate from the opposite sides of the cells. The nuclei of the dorsal epithelial cells are located in the basal part; those of the ventral cells in the apical portion of the cell. The ultrastructural features of the rectal sac, its ventilation synchronized with rhythmic opening of the anus during phases of active water vapour uptake, as well as the reversible arrest of uptake by experimental occlusion of the anus, reveal that condensation and uptake of atmospheric water take place in this organ.

Studies on host-flea relationship. IV. Progesterone and cortisone do not influence the reproductive potentials of rat fleas Xenopsylla cheopis (Rothschild) and X. astia (Rothschild).

Experiments carried out to study the influence of progesterone and cortisone on the initiation of ovarian maturation, fecundity rate and fertility of the two species of rat fleas Xenopsylla cheopis (Rothschild) and X. astia (Rothschild) indicated that these hormones do not exert any influence on their reproductive potentials. This along with earlier observations show that the factors which regulate ovarian maturation and fecundity in these rat fleas are different from those of the rabbit flea Spilopsyllus cuniculi (Dale).

The Experimental Transmission of Endemic Typhus Fever of the United States by the Rat Flea Xenopsylla cheopis

The Experimental Transmission of Endemic Typhus Fever of the United States by the Rat Flea Xenopsylla cheopis