| a new ecology for scrub typhus associated with a focus of antibiotic resistance in rice farmers in thailand. | following the documentation of chloramphenicol-resistant and doxycycline-resistant strains of orientia tsutsugamushi (hyashi) in northern thailand, we conducted ecological and epidemiological studies near the houses of patients hospitalized with antibiotic-resistant infections. new associations between chiggers, rodents, and o. tsutsugamushi in active rice agriculture areas, an ecological habitat not described previously, are reported. rattus rattus (l.) was the most common species (representing ... | 1998 | 9701943 |
| immunocytochemical methods to study the distribution of orientia tsutsugamushi in leptotrombidium (acari: trombiculidae) chiggers. | immunocytochemical methods were developed and tested for their ability to detect the distribution of orientia tsutsugamushi in paraffin sections of adult chiggers (leptotrombidium imphalum vercammen-grandjean & langston). rickettsial antigen was detected by application of a simple direct or amplified immunocytochemistry procedure and an indirect immunofluorescent procedure. in the direct procedure alkaline phosphatase conjugation to the mouse polyclonal antibody to the karp strain was followed b ... | 1998 | 9701944 |
| redescription of leptotrombidium (leptotrombidium) imphalum (acari: trombiculidae), with observations on bionomics and medical importance in northern thailand. | leptotrombidium (leptotrombidium) imphalum vercammen-grandjean & langston is redescribed and illustrated. specimens were collected from the rodents rattus rattus, rattus losea, and bandicota indica in chiangrai province, northern thailand. the species was found on hosts collected on dikes at the margins of rice fields and in adjacent fruit plantations and along irrigation canals, especially in areas covered with the grasses imperata cylindrica (lalang grass) and saccharum arudinaceum. the etiolo ... | 1999 | 10071498 |
| temporal changes in prevalence of scrub typhus rickettsia (orientia tsutsugamushi) infecting the eggs of leptotrombidium imphalum (acari: trombiculidae). | eggs from seven colony lines of the chigger mite leptotrombidium imphalum (vercammen-grandjean & langston) were examined for infection with orientia tsutsugamushi (hyashi), the etiologic agent of scrub typhus. the polymerase chain reaction (pcr) using primers otp 56.809 and otm 56.1221, which amplify a 291 bp region of the p56 gene of o. tsutsugamushi, was used to detect scrub typhus within single eggs. all seven chigger mite lines produced infected eggs with varying rates of infection (li1 = 8. ... | 2001 | 11268679 |
| development of an in vitro method for the evaluation of candidate repellents against leptotrombidium (acari: trombiculidae) chiggers. | we developed a rapid and economical in vitro procedure with which to evaluate the efficacy of candidate repellents against chiggers. the procedure requires only 5 min and a small number of chiggers to obtain a valid estimate of the median effective dose. we used this procedure to evaluate the repellent activity of 11 compounds against the chigger, leptotrombidium imphalum vercammen-grandjean and langston. median effective doses were determined for 10 of the 11 compounds. dm-165-2 (n,n-diethyl-3- ... | 2003 | 12597654 |
| laboratory evaluation of aromatic essential oils from thirteen plant species as candidate repellents against leptotrombidium chiggers (acari: trombiculidae), the vector of scrub typhus. | scrub typhus, a rickettsial disease transmitted by several species of leptotrombidium chiggers (larvae), is endemic in many areas of asia. the disease is best prevented by the use of personal protective measures, including repellents. in this study commercially produced aromatic, essential oils of 13 plant species and ethanol (control) were tested in the laboratory for repellency against host-seeking chiggers of leptotrombidium imphalum vercammen-grandjean and langston (acari: trombiculidae). a ... | 2009 | 19009361 |
| transstadial and transovarial transmission of orientia tsutsugamushi in leptotrombidium imphalum and leptotrombidium chiangraiensis (acari: trombiculidae). | transovarial transmission of orientia tsutsugamushi (hayashi) in laboratory colonies of leptotrombidium chiangraiensis tanskul & linthicum and leptotrombidium imphalum (vercammen-grandjean & langston) (acari: trombiculidae) was studied for two generations. in l. chiangraiensis, the transovarial and filial infection rate was 100% in each generation. only infected females were produced. in l. imphalum, the transovarial infection rate of the parental generation was 100% but declined to 93.3% in the ... | 2009 | 19960694 |
| variation within and among host species in engorgement of larval trombiculid mites. | we recovered larval trombiculid mites (i.e. chiggers), vectors of scrub typhus, from small mammal hosts in taiwan, and compared the relative degree of engorgement (rde) of the dominant chigger (leptotrombidium imphalum) from different hosts. naturally occurring chiggers recovered from rattus losea and bandicota indica were 1·4x and 1·3x as engorged as those from apodemus agrarius. within each host species, rde was negatively related to chigger loads, but was mostly unrelated to gender or to body ... | 2010 | 20946695 |
| identification of potential hosts and vectors of scrub typhus and tick-borne spotted fever group rickettsiae in eastern taiwan. | scrub typhus and tick-borne spotted fever group (sfg) rickettsioses are transmitted by chiggers (larval trombiculid mites) and hard ticks, respectively. we assessed exposure to these disease vectors by extensively sampling both chiggers and ticks and their small mammal hosts in eastern taiwan during 2007 and 2008. the striped field mouse apodemus agrarius pallas (rodentia: muridae) was the most common of the small mammals (36.1% of 1393 captures) and presented the highest rate of infestation wit ... | 2011 | 21223345 |
| influence of orientia tsutsugamushi infection on the developmental biology of leptotrombidium imphalum and leptotrombidium chiangraiensis (acari: trombiculidae). | leptotrombidium chiangraiensis tanskul & linthicum, and leptotrombidium imphalum vercammen-grandjean are important vectors of scrub typhus in rice field habitats in northern thailand. the developmental biology of all stages of the life cycle of two generations of these species of mites infected with orientia tsutsugamushi (hayashi) and uninfected mites is reported. the development of the infected lines of both f1 and f2 l. chiangraiensis were significantly longer than their respective uninfected ... | 2012 | 23270154 |
| transovarial transmission of co-existing orientia tsutsugamushi genotypes in laboratory-reared leptotrombidium imphalum. | the co-evolution of orientia tsutsugamushi and its vector/host leptotrombidium mites is important for this bacterium to survive and exist in its environment. the data in this study demonstrated that o. tsutsugamushi has adapted to take advantage of the parasitic nature of the host's larval stage and thus increase its chance of transmission to a vertebrate host and potentially to other vector mites by increasing its density at the time of transmission. our data demonstrated that during the larval ... | 2016 | 26771218 |
| characterization based on the 56-kda type-specific antigen gene of orientia tsutsugamushi genotypes isolated from leptotrombidium mites and the rodent host post-infection. | abstract. characterization of the 56-kda type-specific antigen (tsa) genes of orientia tsutsugamushi (ot) from three naturally infected, laboratory-reared mite colonies comprising three species (leptotrombidium deliense [ld], leptotrombidium imphalum [li], and leptotrombidium chiangraiensis [lc]) has revealed the presence of single and coexisting ot genotypes found in individual chiggers. the karp genotype was found in all of the chiggers examined, whereas gilliam and ut302 genotypes were only o ... | 2014 | 24297814 |
| efficacy of plant essential oils for the repellents against chiggers (leptotrombidium imphalum) vector of scrub typhus. | scrub typhus caused by the orientia tsutsugamushi. rodents, particularly rats, serve as principal reservoir hosts. infection in man is transmitted by the, chigger bite. repellents provide an effective agent of protecting individuals from chigger. in the present study 6 plant essential oils were tested for evaluation of their repellent activity against the chigger, leptotrombidium imphalum. the results showed that clove oil was significantly more effective than others with ed50 and ec50 of 0.420 ... | 2012 | 22934454 |