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Fleas on roof rats in six areas of Los Angeles County, California: their potential role in the transmission of plague and murine typhus to humans.

Roof rats (Rattus rattus) in southern California are rarely involved with plague epizootics and murine typhus. Little evidence exists implicating these rodents as sources of human infection. This might be explained by the absence of fleas capable of transmitting these 2 diseases. From February 1981 through January 1982, roof rats were live-trapped and examined for fleas each month in 4 areas of Los Angeles County. Two other areas were trapped for 9 and 3 months respectively. Areas sampled were in or near the suburban-wilderness fringe where plague and murine typhus occur, and where roof rats coexist with a variety of wild and domestic mammals and humans. From 1,206 roof rats, 827 fleas belonging to eight species were collected. Leptopsylla segnis (54%) and Nosopsyllus fasciatus (39%) were the most abundant and together comprised 93% of all fleas. Xenopsylla cheopis was not found. The relative abundance and diversity of fleas on roof rats varied considerably between areas, making it difficult to predict flea diversity and abundance in unsurveyed areas where similar conditions exist. However, the overall low flea indices and the absence of X. cheopis help to explain why roof rats in Los Angeles County are rarely involved with plague and murine typhus.

Animals↗

Genotypic identification of murine typhus Rickettsia in rats and their fleas in an endemic area of Greece by the polymerase chain reaction and restriction fragment length polymorphism.

Forty-nine cases of murine typhus were diagnosed in recent years in residents of several communities around the city of Chalkis, the capital of the Prefecture of Evia. (Euboea) Evia is an island connected to central mainland Greece by a bridge. To investigate the endemicity of murine typhus in this area, 226 fleas (Xenopsylla cheopis) and blood samples were collected from 53 rats (Rattus norvegicus) trapped in this area. The polymerase chain reaction followed by restriction fragment length polymorphism analysis (PCR-RFLP) was used to detect and identify Rickettsia typhi, the etiologic agent murine typhus, in the rat blood samples (buffy coat cells) as well as in their fleas. An indirect immunofluorescent antibody (IFA) assay was performed to detect antibodies against R. typhi in rat serum samples. The presence of R. typhi in both fleas and rat blood samples was demonstrated. The frequency of infection for X. cheopis was 4%, while 18% of the rats had buffy coat cells infected, and 92% of the rat sera tested by IFA were positive for anti-R. typhi antibodies. The present work is the first successful application of PCR-RFLP in a field study of naturally infected rats and their fleas in Europe.

Animals↗

Evidence of Rickettsia typhi and the potential for murine typhus in Jayapura, Irian Jaya, Indonesia.

Murine typhus (etiologic agent: Rickettsia typhi) is endemic to Indonesia, especially on the highly populated island of Java. A survey of rodents from Irian Jaya, the eastern-most province of Indonesia, indicated striking geographic variation in risk factors associated with murine typhus. Murid rodents (n = 112) collected from two villages in the Arso district of northeastern Irian Jaya, were found to be free of ectoparasites normally associated with transmission of R. typhi (i.e., Xenopsylla cheopis). All rodents (n = 72) tested by enzyme-linked immunosorbent assay were negative for antibodies to R. typhi, whereas 12.5% (9/72) were positive for antibodies to Orienta tsutsugamushi. In contrast, both Rattus norvegicus and R. rattles (combined n = 87) from the harbor area of the provincial capital, Jayapura, were infested with flea ectoparasites. X. cheopis was found on 31 (35.6%) of the live-captured rodents. Serum samples from nine of 82 rodents contained antibodies reactive to R. typhi (11.0%). These data show for the first time that rodents exposed to R. typhi are well established in Jayapura, and that some of these rodents harbor fleas potentially capable of transmitting murine typhus and plague.

Animals↗

Scrub typhus in Japan: epidemiology and clinical features of cases reported in 1998.

Surveillance for scrub typhus was conducted in Japan in 1998 using a questionnaire. A total of 462 cases were reported. Scrub typhus occurred in both the fall and spring in the northern part of Honshu (the main island), and in the fall in the central part of Honshu and on the island of Kyushu. The occurrence of the disease varied with age, gender, and activity. Seventy-six percent of the patients were more than 51 years old, and 36% and 16% of the patients were engaged in farm work and forestry, respectively. Fever, rash, and eschar were detected in 98%, 93%, and 97% of the patients, respectively. Elevated levels of C-reactive protein, aspartate transaminase, and alanine transaminase were detected in 96%, 87%, and 77% of the patients, respectively. Disseminated intravascular coagulation developed in 34 cases and had a unique regional distribution. This study shows the status of scrub typhus in Japan in 1998 and provides important information for diagnosis and prevention.

Adolescent↗

Scrub typhus in north Queensland.

Scrub typhus was once common in north Queensland, but no reports from this region have been published for nearly 30 years, and the focus has turned to cases from the Northern Territory and Western Australia. In 1996, diagnosis of scrub typhus in a Queensland soldier led to recognition of an earlier outbreak with up to 17 cases. Another outbreak occurred a year later with 11 confirmed cases. All cases were in soldiers who had visited a training area near Innisfail. Review of other laboratory diagnoses of scrub typhus shows it is still prevalent in north Queensland, with several "hot spots".

Adult↗

Evaluation of the whole blood lymphocyte transformation assay for scrub typhus exposure: adaptability to field sample collection.

The optimal conditions for the determination of exposure to scrub typhus by the whole blood lymphocyte transformation assay was 7 days culture of 10% blood in RPMI 1640 medium supplemented with 10% human AB-negative serum and L-glutamine with 50-200 micrograms protein/ml of Karp, Kato, or Gilliam strain membrane antigen. A simple exponentially decaying linear model shows the decrease in lymphocyte viability, the ability of sensitized cells to be stimulated with PHA mitogen, and the corresponding decrease in stimulation by scrub typhus antigens with increasing time of preincubation on ice. The lower limit of stimulation index for the detection of scrub typhus by whole blood lymphocyte transformation assay was 4.0 with a type I error of 1%.

Antigens, Bacterial↗

Clinical and epidemiological observations regarding the 1998 Kauai murine typhus outbreak.

Five cases of murine typhus occurring on southwestern Kauai in 1998 are described, following an investigation by the Department of Health. Two cases also had concurrent leptospirosis. Recent habitat changes of peridomestic animals and their fleas may have increased the risk for developing murine typhus. Increased suspicion of typhus by island physicians and more aggressive rodent control activities are recommended.

Adult↗

A returned traveller with persistent fever due to murine typhus.

Murine (endemic) typhus is a notifiable disease in Hong Kong, but its diagnosis can be difficult. We report a case of murine typhus in a middle-aged man who presented with persistent fever, headache, and skin rash 2 weeks after returning from a visit to China. The diagnosis of murine typhus requires a high index of suspicion for a febrile patient with a history of potential exposure to the disease vector (rat flea) in an endemic area. The importance of early recognition lies in the potential for early therapeutic intervention, leading to decreases in morbidity and duration of stay in hospital.

Anti-Bacterial Agents↗

Murine typhus--Hawaii, 2002.

Murine typhus, a zoonotic disease caused by Rickettsia typhi, is uncommon in the United States. Hawaii typically reports five or six cases annually; however, 47 cases were reported in 2002. This report summarizes clinical data for three of these cases and describes murine typhus activity in Hawaii during 2002 and control efforts of the Hawaii Department of Health (HDH). The high number of reported cases in 2002 underscores the need for community education to prevent murine typhus and an assessment of environmental factors that might contribute to local disease transmission.

Adolescent↗

Epidemiological studies on host animals of scrub typhus of the autumn-winter type in Shandong Province, China.

In order to elucidate the host animals of scrub typhus in Shandong Province, epidemiological studies on host rodents of the autumn-winter type scrub typhus were carried out from 1995 to 2002 at four localities in the Shandong Province. Based upon ecological observations of the composition, seasonal fluctuation of animal hosts, isolation of Orientia tsutsugamushi, detection and identification of serotypes of antibodies to O. tsutsugamushi were conducted. Two thousand eight hundred and eighty-four rodents and insectivores were captured, including 2,055 Apodemus agrarius (71.26%), 408 Cricetulus triton (14.15%), 64 C. barabensis (2.22%), 12 Crocidura suaveolens (0.42%), 313 Rattus (R.) norvegicus (10.85%), 32 Mus (M.) musculus (1.11%). A. agrarius was predominant in the field and the seasonal fluctuation was correlated significantly to that of scrub typhus (r=0.810, p<0.005). R. norvegicus was predominant indoors. The average capture rate per year in the field was 12.76% from 1995 to 1997. Of the total 2,884 rodents and insectivores captured out- and in-doors, 527 were living rodents (including 335 A. agrarius, 119 C. triton, 6 C. barabensis, 2 C. suaveolens, 63 R. norvegicus and 2 M. musculus, and 15,467 chigger mites were collected from them. Two hundred and fifty-three of 335 A. agrarius were parasitized by chiggers, showing 75.52% (253/335) of the infestation rate and 17.53 of the chigger index; 106 C. triton were parasitized by chiggers, showing 89.08% (106/119) infestation rate and 75.93 of the chigger index. The average antibody positive rate of rodents was 14.78%. The seasonal change of the antibody positive rate was higher during December-February (the second year), and varied from 20% to 28%, but the level of antibodies remained relatively low (5.26-16.67%) during March-November. The results of serotyping with 47 antibody-positive sera were as followings: 39 sera were Gilliam types, 7 sera were Karp types, 1 serum was Kato type. Twelve strains of O. tsutsugamushi were isolated from A. agrarius (8 strains), C. triton (3 strains) and R. norvegicus (1 strain), out of the isolated 12 strains, 10 were Gilliam strains, 2 were Karp strains. A. agrarius and R. norvegicus were the main host animals in out- and indoors respectively.

Animals↗

Scrub typhus during pregnancy: a case report and review of the literature.

Scrub typhus is a rickettsial disease that is uncommon during pregnancy. We report a case of a 33-year-old woman, G1P0, 29 weeks pregnancy who presented to hospital with high fever, chill and headache for two weeks. Her diagnosis of scrub typhus was confirmed by serum immunofluorescent assay. She was successfully treated with chloramphenicol, but preterm delivery occurred. Her infant died from respiratory distress syndrome. No vertical transmission was demonstrated in this case. Scrub typhus should be listed in the differential diagnosis of acute febrile illness in pregnant women, who either live in, or return from, endemic areas. Chloramphenicol can be used safely during pregnancy if it is not circulating at the time of delivery.

Adult↗

Induction of protective immunity against scrub typhus with a 56-kilodalton recombinant antigen fused with a 47-kilodalton antigen of Orientia tsutsugamushi Karp.

A partial gene sequence encoding the 56-kD scrub typhus antigen (Sta56) was amplified from genomic DNA of the Orientia tsutsugamushi Karp strain by a polymerase chain reaction (PCR). The PCR product was ligated with the 47-kD scrub typhus antigen (Sta47) gene in the pQE30/47 expression vector, and the resulting recombinant expression vector was designated pQE30/56-47. A fusion antigen (Sta56-47) was expressed in Escherichia coli cells transformed with pQE30/56-47 after induction with isopropyl-beta-d-thiogalactopyranoside. The Sta56-47 antigen was recognized by both Sta47 and Sta56 immune sera and by immune serum to Sta56-47 in an immunoblot assay. This antigen was purified and used to immunize BALB/c mice. The animals immunized with Sta56-47 exhibited profound humoral and cellular immune responses, as well as increased resistance to O. tsutsugamushi Karp compared with mice immunized with Sta56 or Sta47. These results strongly suggest that Sta56-47 contains antigenic epitopes of the Sta56 and Sta47 antigens of O. tsutsugamushi Karp, and is a more suitable candidate for replacing whole-cell antigen of O. tsutsugamushi Karp to induce protective immunity against scrub typhus.

Animals↗

Development and evaluation of a latex agglutination test for the rapid diagnosis of scrub typhus.

The purpose of this research was to develop a simple and rapid diagnostic test for scrub typhus using a latex agglutination test (LAT) to detect antibodies against Orientia tsutsugamushi. Five strains of O. tsutsugamushi were propagated in L929 cells. The rickettsiae were purified and concentrated with percoll density gradient centrifugation. A suitable concentration of O. tsutsugamushi soluble antigen was used to sensitize latex to prepare the latex antigen. The specificity, sensitivity, and accuracy of the latex antigen were assessed. The LAT, indirect immunofluorescent antibody test (IFA), and Weil-Felix agglutination test (WF) were compared by testing 109 acute febrile illness cases and 100 confirmed non-scrub typhus cases (50 other febrile disease cases and 50 healthy controls). By using the IFA as the standard reference method, the overall sensitivity, specificity, and accuracy of the LAT were 89.1, 98.2, and 93.6%, respectively. By contrast, the sensitivity of the WF, compared with the IFA, was only 47.3%, while the specificity and accuracy were 92.6 and 69.7%, respectively. Thus, the LAT described here is another important alternative test for the diagnosis of scrub typhus.

Antibodies, Bacterial↗

Scrub typhus.

Scrub typhus, a dreaded disease in pre-antibiotic era, is an important military disease which caused thousands of cases in the Far East during Second World War. It is a zoonosis and is a widespread disease in Asia and Pacific Islands. Scrub typhus is an acute febrile illness which generally causes non-specific symptoms and signs. The clinical manifestations of this disease range from sub-clinical disease to organ failure to fatal disease. Deaths are attributable to late presentation, delayed diagnosis, and drug resistance. The public health importance of this disease is underestimated because of difficulties with clinical diagnosis and lack of laboratory methods in many geographical areas. Scrub typhus is known to occur all over India and physicians should be aware of this potentially serious but easily treatable disease.

Acute Disease↗

[Struggle against typhus in the Caucasian front during the 1st World War].

As an infectious disease, typhus has triggered many epidemics during the course of wars and caused thousands of death all through the ages. The French physician Charles Nicolle (1886-1936) defined its agent as a louse transferring the disease from man to man in 1909 and was awarded the Nobel Prize in 1928. Many cases were reported during the 1st World War both in the European and the Ottoman armies; and one of the most severe epidemics broke in the Caucasian front; a great number of civilians and soldiers died at winter in 1914 and 1915. Lice had to be destroyed in order to prevent the epidemic, but etuves in the Caucasian front was too few to achieve it. Clothes were cleansed in ovens by means of a method proposed by Dr. Abdülkadir Noyan (1886-1977). On March 28, 1915 the first typhus vaccination, obtained from the infected blood of the patients, was applied by Dr. Tevfik Salim (Saklam) (1882-1963). In 1916 Dr. Ahmet Fikri Tüzer discovered a disinfection apparatus called "buğu sandiği" (vapour box) which was widely used in the Caucasian front after 1917. This apparatus was highly useful in controlling the typhus epidemics. 164 health officers lost their lifes in the Caucasian front between 1914-1918, in addition, 7310 military casualties were recorded from 1915 to the end of the war.

Disease Outbreaks↗

Rapid diagnosis of scrub typhus in rural Thailand using polymerase chain reaction.

The aim of this study was to evaluate the use of polymerase chain reaction (PCR) amplification of the O. tsutsugamushi 16S rRNA gene for the diagnosis of scrub typhus in rural Thailand. A prospective study of acute febrile illness in Udon Thani, northeast Thailand, identified 183 patients as having scrub typhus on the basis of immunofluorescent antibody testing (IFA) of paired sera. A further 366 febrile patients admitted concurrently with a range of other diagnoses acted as negative controls. Diagnostic sensitivity and specificity of 16S rRNA PCR was 44.8% and 99.7%, respectively, compared with IFA. PCR positivity was related to duration of symptoms and presence of eschar (P < 0.001, both cases). PCR using primers to amplify a fragment of the 56-kd gene had a sensitivity and specificity of 29.0% and 99.2%, respectively. PCR has a high specificity but low sensitivity for the rapid diagnosis of scrub typhus in this endemic setting.

Humans↗

Scrub typhus in suburban Bangkok: first cases.

Three patients, two of whom had eschars, were admitted with fulminant febrile disease suggestive of scrub typhus. Elevated IgG and IgM to Rickettsia tsutsugamushi were detected in all three by IFA. The cases lived in widely separated areas of western Bangkok where fruit trees are grown and claimed not to have left the areas of their homes during the estimated incubation periods. A field survey collected rodents, treeshrews, and mites fro around the homes of each case. R. tsutsugamushi was isolated from one rat and known vector species of mites were found. These are the first confirmed cases of scrub typhus transmission in Metropolitan Bangkok. It is suggested that typhus incidence around Bangkok may be substantial but has been unreported because of widespread self-medication with antibiotics and the difficulties of laboratory diagnosis.

Adult↗

Laboratory animal models for human scrub typhus.

A wide variety of animals have been utilized in an attempt to provide the information necessary to bring scrub typhus to the point where it is no longer a threat to man. The laboratory mouse is usually the animal of choice for the study of this disease. The discovery that certain strains of inbred mice are genetically resistant to Rickettsia tsutsugamushi, the agent of scrub typhus, has opened new avenues in the study of the immune response to the disease. The cynomolgus monkey, Macaca fascicularis, appears to be the best animal model for the study of scrub typhus as it occurs in humans and should be useful in the development of an efficacious vaccine.

Animals↗