ABSTRACT
An epidemiological study in a mature oil palm estate in Peninsular Malaysia has demonstrated a low prevalence of R. tsutsugamushi infection in small mammals. The direct fluorescent antibody technique for assaying infections in chiggers proved more sensitive than mouse inoculation. Most infections in both chiggers and rodents were caused by the Karp strain.
Subject(s)
Animals , Animals, Wild/immunology , Antibodies, Bacterial/analysis , Disease Vectors , Fluorescent Antibody Technique , Malaysia , Mites/immunology , Orientia tsutsugamushi/immunology , Rodentia/immunology , Scrub Typhus/immunology , Serotyping , Trombiculidae/immunologyABSTRACT
Dog sera, collected from different communities throughout Selangor, Peninsular Malaysia, were investigated for the presence of antibodies to R. tsutsugamushi and R. typhi. Scrub typhus antibodies were present in animals from the rural areas only, whereas murine typhus antibodies were observed in equal numbers of dogs from both rural and metropolitan areas. Greater percentage of dogs from suburban areas had demonstrable antibody titers to murine typhus than from the urban area.
Subject(s)
Animals , Antibodies, Bacterial/analysis , Dog Diseases/epidemiology , Dogs , Fluorescent Antibody Technique/methods , Malaysia , Orientia tsutsugamushi/immunology , Rickettsia typhi/immunology , Scrub Typhus/diagnosis , Typhus, Endemic Flea-Borne/diagnosisABSTRACT
Over 1,200 isolations of R. tsutsugamushi were obtained over 7 generations of L. (L.) arenicola and no reproducible differences in virulence or antigenic markers could be detected among these isolations. The F8 generation yielded rickettsia with the same antigenic makeup and virulence properties as the original female parent mite. When these isolates were inoculated into mice they elicited the same predominant antibody specificities, i.e. they all produced antibody which reacted with the TA 763 and Karp strains. These were the same as the major antigens detected by direct fluorescent antibody staining of the isolates.
Subject(s)
Animals , Antibody Specificity , Antigens, Bacterial , Arachnid Vectors , Mites/microbiology , Orientia tsutsugamushi/immunology , Trombiculidae/microbiology , VirulenceABSTRACT
Numbers of L. (L.) deliense larvae were determined in adjacent habitats over a 16 month period. Both R. argentiventer and R. tiomanicus were highly efficient hosts for L. (L.) deliense. R. argentiventer was host to significantly greater numbers of chiggers per rat than was R. tiomanicus. The 2 habitats were similar in numbers of chiggers collected. No consistent correlation was apparent between numbers of chiggers and any single weather factor, but the chigger population seemed to be adversely affected by a 2 month period during which total evaporation greatly exceeded total rainfall. Direct fluorescent antibody examination of tissues from unfed L. (L.) deliense showed that 2 of 420 larvae (0.5%) contained organisms morphologically resembling R. tsutsugamushi. Considering the vector load and numbers of chiggers being returned to the ground by a given host, a rate of 0.5% appeared adequate to account for the prevalence rate of R. tsutsugamushi observed in the 2 host species.
Subject(s)
Animals , Arachnid Vectors , Ecology , Malaysia , Mites , Orientia tsutsugamushi/isolation & purification , Population Density , Rats/microbiology , Species Specificity , Trombiculidae/microbiology , WeatherABSTRACT
The passive transfer of convalescent sera did not protect the majority of mice against challenge with the homologous strain and was completely ineffective against challenge with strains unrelated by fluorescent antibody techniques. When the immune sera was incubated with the rickettsia in vitro and then inoculated into the mice a dramatic increase occurred in the number of surviving mice. The importance of these data in relation to published results with other species of rickettsia is discussed.