Oriental Rat Flea Xenopsylla Cheopis Research Articles

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

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

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.

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.