GroEL is an immunodominant surface-exposed antigen of Rickettsia typhi

Rickettsioses are neglected and emerging potentially fatal febrile diseases that are caused by obligate intracellular bacteria, rickettsiae. Rickettsia (R.) typhi and R. prowazekii constitute the typhus group (TG) of rickettsiae and are the causative agents of endemic and epidemic typhus, respectively. We recently generated a monoclonal antibody (BNI52) against R. typhi. Characterization of BNI52 revealed that it specifically recognizes TG rickettsiae but not the members of the spotted fever group (SFG) rickettsiae. We further show that BNI52 binds to protein fragments of ±30 kDa that are exposed on the bacterial surface and also present in the periplasmic space. These protein fragments apparently derive from the cytosolic GroEL protein of R. typhi and are also recognized by antibodies in the sera from patients and infected mice. Furthermore, BNI52 opsonizes the bacteria for the uptake by antigen presenting cells (APC), indicating a contribution of GroEL-specific antibodies to protective immunity. Finally, it is interesting that the GroEL protein belongs to 32 proteins that are differentially downregulated by R. typhi after passage through immunodeficient BALB/c CB17 SCID mice. This could be a hint that the rickettsia GroEL protein may have immunomodulatory properties as shown for the homologous protein from several other bacteria, too. Overall, the results of this study provide evidence that GroEL represents an immunodominant antigen of TG rickettsiae that is recognized by the humoral immune response against these pathogens and that may be interesting as a vaccine candidate. Apart from that, the BNI52 antibody represents a new tool for specific detection of TG rickettsiae in various diagnostic and experimental setups.

COYOTES (CANIS LATRANS) IN ARIZONA, USA, EXHIBIT IMMUNE AND GENETIC EVIDENCE OF RICKETTSIAL INFECTIONS

Rocky Mountain spotted fever (RMSF), caused by the bacterium Rickettsia rickettsii, was recognized as endemic in Arizona, US after a 2002 outbreak and has since been a public health concern. The brown dog tick (Rhipicephalus sanguineus sensu lato) is the principal vector of this pathogen in Arizona. Domesticated dogs (Canis lupus familiaris) are the tick's main host, so free-roaming dogs in peridomestic areas have been named the primary risk factor for human cases of RMSF. However, the sudden emergence and long-distance dispersal of the pathogen have not been adequately explained, and one possible mechanism could include wildlife. Coyotes (Canis latrans) are wide ranging in Arizona and closely related to dogs, so it is possible that brown dog ticks parasitize coyotes and infect them. Although R. rickettsii is the most severe spotted fever group (SFG) rickettsial pathogen in humans, others occur in Arizona, and antibodies raised against them are cross-reactive, so we more-broadly hypothesized that coyotes in Arizona are exposed to SFG rickettsiae. We collected coyote tissues in spring 2016 and 2017. We tested sera for antibodies to R. rickettsii and found 9% (8/94) of samples were antibody-positive with titers of ≥256. Subsequent quantitative PCR analyses of skin showed evidence for Rickettsia spp. in 2.9% (4/138) of samples. These data suggest that coyotes have a role in the maintenance of SFG rickettsiae in Arizona. Further investigation is warranted to reveal which specific pathogen-vector complexes act on coyotes in the region and whether they represent a risk to human health.

Discrepancies between self-reported tick bites and evidence of tick-borne disease exposure among nomadic Mongolian herders

Twenty-six per cent of Mongolians live pastoral lifestyles, increasing their likelihood of exposure to ticks and placing them at a higher risk for contracting tick-borne diseases (TBDs). Anaplasma spp. and Rickettsia spp. have been identified in ticks, livestock and humans in Mongolia, but no known qualitative research has been conducted investigating the association between nomadic herder characteristics, tick bite history and exposure to TBDs. To better understand the association between self-reported tick bites and symptoms versus actual exposure to TBDs, this study paired serological data with 335 surveys administered to Mongolian herders, ages 12-69, from 2014 to 2015. Logistic regression results identified no significant associations between reported tick bites or symptoms with serological evidence of Anaplasma spp. and Rickettsia spp. controlling for age, gender and aimag. Among the 335 respondents who were seropositive to either Anaplasma spp. or Rickettsia spp., 32.9% self-reported experiencing abnormal symptoms such as redness, inflammation, headache, arthritis or fever after being bitten. Alternatively, 17.3% (58/335) of individuals reported experiencing symptoms following a tick bite in instances where serological results indicated no exposure to Anaplasma spp. or Rickettsia spp. Results also identified inconsistencies in reporting and seroprevalence among different age groups, with children having the highest reporting and treatment seeking rates but low levels of exposure in comparison with other groups. While survey results showed that individuals were aware of peak tick seasons and tick species that inhabit specific areas, 58% of heads of households (49/84) were unaware that ticks can cause disease in livestock or dogs. This study suggests that herders are an at-risk population in Mongolia with gaps in awareness of TBD risk. Increased surveillance paired with focused outreach to prevent TBDs targeted to the herder population is encouraged.

Ticks and serosurvey of anti-Rickettsia spp. antibodies in wild boars (Sus scrofa), hunting dogs and hunters of Brazil

Background

Rickettsia bacteria are responsible for diseases in humans and animals around the world, however few details are available regarding its ecology and circulation among wild animals and human populations at high transmission risk in Brazil. The aim of this study was to investigate the occurrence of ticks and Rickettsia spp. in wild boars, corresponding hunting dogs and hunters.

Methods

Serum samples and ticks were collected from 80 free-range wild boars, 170 hunting dogs and 34 hunters from southern and central-western Brazil, from the Atlantic Forest and Cerrado biomes, respectively, between 2016 and 2018. Serum samples were tested by indirect immunofluorescent-antibody assay (IFA) to detect IgG antibodies against Rickettsia rickettsii, Rickettsia parkeri, Rickettsia bellii, Rickettsia rhipicephali and Rickettsia amblyommatis. Tick species were identified by morphological taxonomic keys, as previously described. A total of 164 ticks including A. sculptum, A. brasiliense and A. aureolatum were tested in PCR assays for Spotted Fever Group (SFG) Rickettsia spp.

Results

A total of 58/80 (72.5%) wild boars, 24/170 (14.1%) hunting dogs and 5/34 (14.7%) hunters were positive (titers ≥ 64) to at least one Rickettsia species. A total of 669/1,584 (42.2%) ticks from wild boars were identified as Amblyomma sculptum, 910/1,584 (57.4%) as Amblyomma brasiliense, 4/1,584(0.24%) larvae of Amblyomma spp. and 1/1,584 (0.06%) nymph as Amblyolmma dubitatum. All 9 ticks found on hunting dogs were identified as Amblyomma aureolatum and all 22 ticks on hunters as A. sculptum. No tested tick was positive by standard PCR to SFG Rickettsia spp.

Conclusions

The present study was the concomitant report of wild boar, hunting dog and hunter exposure to SFG rickettsiae agents, performed in two different Brazilian biomes. Wild boar hunting may increase the risk of human exposure and consequently tick-borne disease Wild boars may be carrying and spreading capybara ticks from their original habitats to other ecosystems. Further studies can be required to explore the ability of wild boars to infecting ticks and be part of transmission cycle of Rickettsia spp.

The present study reported serological findings and molecular assays of Rickettsia spp and ticks of wild boars, simultaneous to their correspondent hunting dogs and hunters. Seropositivity for Rickettsia spp. was higher in wild boars when compared to dogs and humans but was similar between dogs and humans. Despite Rickettsia spp. prevalence was statistically higher in southern than central-western Brazil for wild boars, no significance was observed in hunting dogs and hunters. For the first time, A. sculptum ticks were founded in wild boars from the subtropical climate of southern Brazil. Despite human beings have been considered less exposed to ticks (and therefore rickettsiae) than animals, specific human activities such as wild boar hunting may increase the risk of exposure and consequently tick-borne disease. Wild boars may be carrying and spreading capybara ticks from their original habitats to other ecosystems. These results may provide important findings for public action planning to prevent neglected vector-borne diseases in overlapping areas of wild boars, hunting dogs and hunters. Further studies can be required to explore the ability of wild boars to infecting ticks and be part of transmission cycle of Rickettsia spp.

Human-pathogenic Anaplasma spp., and Rickettsia spp. in animals in Xi'an, China

In China, thirteen species of tick-borne rickettsiales bacteria pathogenic to human have been reported in ticks and host animals, and human patients caused by them also has been identified. However, investigation for rickettsiales bacteria circulating in Xi'an wasn't performed although diseases resembling human diseases caused by these organisms have been found. In this study, domestic animals and ticks in Xi'an, China, were tested for the presence of rickettsiales bacteria pathogenic to humans. Besides A. ovis, a high prevalence of A. capra was observed suggesting a high public health risk exists. In addition, two novel Anaplasma species closely related to A. phagocytophilum were identified and formed distinct lineages in the phylogenetic trees, with more than 98.3% identities for rrs gene, while divergences up to 20.2% and 37.0% for groEL and gltA genes, respectively. Both of these two novel Anaplasma species were found to circulate in goats and further assessment of their pathogenicity is needed. Ca. R. jingxinensis, with potential pathogenicity, was also detected in H. longicomis ticks with high prevalence. However, other causative agents were not identified although they were distributed in other areas of China.

A 2015 outbreak of flea-borne rickettsiosis in San Gabriel Valley, Los Angeles County, California

Although flea-borne rickettsiosis is endemic in Los Angeles County, outbreaks are rare. In the spring of 2015 three human cases of flea-borne rickettsiosis among residents of a mobile home community (MHC) prompted an investigation. Fleas were ubiquitous in common areas due to presence of flea-infested opossums and overabundant outdoor cats and dogs. The MHC was summarily abated in June 2015, and within five months, flea control and removal of animals significantly reduced the flea population. Two additional epidemiologically-linked human cases of flea-borne rickettsiosis detected at the MHC were suspected to have occurred before control efforts began. Molecular testing of 106 individual and 85 pooled cat fleas, blood and ear tissue samples from three opossums and thirteen feral cats using PCR amplification and DNA sequencing detected rickettsial DNA in 18.8% of the fleas. Seventeen percent of these cat fleas tested positive for R. felis-specific DNA compared to under two (<2) percent for Candidatus R. senegalensis-specific DNA. In addition, serological testing of 13 cats using a group-specific IgG-ELISA detected antibodies against typhus group rickettsiae and spotted fever group rickettsiae in six (46.2%) and one (7.7%) cat, respectively. These results indicate that cats and their fleas may have played an active role in the epidemiology of the typhus group and/or spotted fever group rickettsial disease(s) in this outbreak.

Outbreaks of flea-borne rickettsiosis are rare despite the endemic status in Los Angeles County. In the spring of 2015 three human cases of flea-borne rickettsiosis among residents of a mobile home community (MHC) prompted an investigation. Fleas were found in all common areas at the MHC due to presence of flea-infested opossums and overabundant outdoor cats and dogs. The MHC was summarily abated in June 2015, and within five months, flea control and removal of animals significantly reduced the flea population. Two additional epidemiologically-linked human cases detected at the MHC were considered to have occurred before control efforts began. Molecular testing of cat fleas, immunological testing of opossums and feral cats collected at the site indicated active transmission of flea-borne rickettsiosis. This study represents the first flea-borne rickettsial outbreak that summary abatement approach was used to reduce its intensity.

Rickettsial Infections among Ctenocephalides felis and Host Animals during a Flea-Borne Rickettsioses Outbreak in Orange County, California

Due to a resurgence of flea-borne rickettsioses in Orange County, California, we investigated the etiologies of rickettsial infections of Ctenocephalides felis, the predominant fleas species obtained from opossums (Didelphis virginiana) and domestic cats (Felis catus), collected from case exposure sites and other areas in Orange County. In addition, we assessed the prevalence of IgG antibodies against spotted fever group (SFGR) and typhus group (TGR) rickettsiae in opossum sera. Of the 597 flea specimens collected from opossums and cats, 37.2% tested positive for Rickettsia. PCR and sequencing of rickettsial genes obtained from C. felis flea DNA preparations revealed the presence of R. typhi (1.3%), R. felis (28.0%) and R. felis-like organisms (7.5%). Sera from opossums contained TGR-specific (40.84%), but not SFGR-specific antibodies. The detection of R. felis and R. typhi in the C. felis fleas in Orange County highlights the potential risk for human infection with either of these pathogens, and underscores the need for further investigations incorporating specimens from humans, animal hosts, and invertebrate vectors in endemic areas. Such studies will be essential for establishing a link in the ongoing flea-borne rickettsioses outbreaks.

Seroconversions for Coxiella and Rickettsial Pathogens among US Marines Deployed to Afghanistan, 2001-2010

We assessed serum samples from 1,000 US Marines deployed to Afghanistan during 2001-2010 to find evidence of 4 rickettsial pathogens. Analysis of predeployment and postdeployment samples showed that 3.4% and 0.5% of the Marines seroconverted for the causative agents of Q fever and spotted fever group rickettsiosis, respectively.

Rickettsial Disease in the Peruvian Amazon Basin

Using a large, passive, clinic-based surveillance program in Iquitos, Peru, we characterized the prevalence of rickettsial infections among undifferentiated febrile cases and obtained evidence of pathogen transmission in potential domestic reservoir contacts and their ectoparasites. Blood specimens from humans and animals were assayed for spotted fever group rickettsiae (SFGR) and typhus group rickettsiae (TGR) by ELISA and/or PCR; ectoparasites were screened by PCR. Logistic regression was used to determine associations between patient history, demographic characteristics of participants and symptoms, clinical findings and outcome of rickettsial infection. Of the 2,054 enrolled participants, almost 2% showed evidence of seroconversion or a 4-fold rise in antibody titers specific for rickettsiae between acute and convalescent blood samples. Of 190 fleas (Ctenocephalides felis) and 60 ticks (Rhipicephalus sanguineus) tested, 185 (97.4%) and 3 (5%), respectively, were positive for Rickettsia spp. Candidatus Rickettsia asemboensis was identified in 100% and 33% of the fleas and ticks tested, respectively. Collectively, our serologic data indicates that human pathogenic SFGR are present in the Peruvian Amazon and pose a significant risk of infection to individuals exposed to wild, domestic and peri-domestic animals and their ectoparasites.

Rickettsial infection remains relatively unexplored in South America compared to other regions of the world. For most regions of Peru (including the Amazon Basin), nothing more than broad serological characterization is available about circulating rickettsiae. Even less is known about the animal reservoirs and insect vectors involved in disease transmission. With this study we aimed to better characterize the circulating species of Rickettsia in humans in the Amazon Basin, as well as investigate their domestic animal reservoir and arthropod vectors. Out of 2054 fever patients enrolled we identified 38 individuals with serologic evidence for acute rickettsial infection. Their homes were visited in order to draw blood samples and collect ectoparasites from their domestic animals. Serology and molecular methods were used to test the animal blood samples as well as the ectoparasites. The information collected contributes to the understanding of the transmission dynamics of rickettsial diseases in Iquitos and leads to a better understanding of the exposure risk to rickettsial infection and it will guide approaches for prevention.

Dynamics of Exposure to Rickettsia parkeri in Cattle in the Paraná River Delta, Argentina

Several cases of human rickettsiosis caused by Rickettsia parkeri were recently documented in the Paraná River delta of Argentina, where the tick vector is Amblyomma triste Koch. As cattle suffer recurrent A. triste infestations, they are at risk of becoming infected with R. parkeri Herein we investigated the dynamics of R. parkeri and its A. triste vector in a herd of beef cattle. Cattle were followed for 18 mo and samples were analyzed for the presence of antibodies against four Rickettsia species (R. parkeri, Rickettsia bellii, Rickettsia amblyommii, and Rickettsia felis) and also for the presence of rickettsial DNA. Additionally, cattle were examined for attached ticks and questing adult ticks were collected. All ticks were analyzed for the presence of rickettsial DNA. No evidence of rickettsemia was found in any cow, but the high R. parkeri infection rate documented in A. triste both questing in the study area (13.9%) and feeding on cattle (19.8%) and the identification of antibodies against R. parkeri antigen in 90% of cattle are evidence that infection is taking place. Altogether, our data suggest that A. triste ticks are capable of naturally exposing cattle to R. parkeri However, the progress of R. parkeri infection and its impact on bovine health and production remain to be established.

[Etiology and epidemiological characterization of non-malarial febrile syndrome in three municipalities of Urabá (Antioquia), Colombia]

INTRODUCTION

Urabá, a region on the northern coast of Colombia, is endemic to several acute febrile illnesses of infectious origin; however, only patients with malaria may have access to quick and effective diagnosis. For this reason, many non-malarial febrile patients go without a clear etiologic diagnosis.

AIM

To establish the etiology and clinical signs of acute febrile non-malaria syndromes and explore some of the likely risk factors in patients originating in the municipalities of Necocli, Turbo and Apartado who exhibit these symptoms.

MATERIALS AND METHODS

We obtained acute and convalescent sera from 220 non-malarial febrile patients from the rural and urban zones of Necocli, Turbo and Apartado during 2007 and 2008. Serologic tests for dengue (IgM by ELISA), leptospirosis (IgM and IgG by IFA), rickettsiosis (IgG by IFI), hanta and arenavirus (IgG by ELISA) were performed.

RESULTS

We found that the frequency of infection for dengue, leptospirosis, rickettsiosis and arenavirus, was 37.3%; 14.1%; 2.7% and 0.5%, respectively. There were 12 co-infection cases of leptospirosis-dengue and one of leptospirosis-rickettsiosis-dengue. Male gender and relative humidity were considered risk factors for dengue, and the beginning of clinical signs in February of 2008 was associated with the infection of dengue and leptospirosis.

CONCLUSION

This study confirms previous records that underline the importance of Rickettsia spp, dengue virus and Leptospira spp as causal agents of febrile syndrome in this region of Colombia.

[Ecoepidemiology of rickettsial infection in rodents, ectoparasites and humans in northeastern Antioquia, Colombia]

INTRODUCTION

Rickettsia spp. are tick, flea or lice-borne pathogenic bacterium, usually carried by rodents. In the last decade three outbreaks of rickettsial disease including fatalities, occurred in the provinces of Antioquia and Córdoba in northwestern Colombia.

OBJECTIVE

The purpose of this study was to perform an ecological and epidemiological description of the Rickettsia spp infection in the recently affected region of Colombia.

MATERIALS AND METHODS

Samples were obtained from 354 rodents and their parasites captured in the municipalities of Apartadó, Turbo and Necoclí. Likewise, 220 human sera were also collected, for detection of infection by Rickettsia spp.

RESULTS

Indirect immunofluorescence assay (IFA) revealed that 130 (43%) of the rodents and 53 (24%) of the humans produced antibodies to Rickettsia spp. Additionally, rickettsial DNA was amplified by PCR from 23 (6.8%) rodent liver samples using primers directed to the genus specific gltA gene. While gltA sequences from rodent samples exhibited a 98.7% similitude with R . prowazekii, a sequence amplified from larvae of Amblyomma sp exhibited identities of >99% similarity with R. tamurae .

CONCLUSION

These results demonstrate the presence of rickettsia in rodents, ectoparasites and humans throughout the municipalities studied.

[Probable case of flea-borne spotted fever (Rickettsia felis)]

Rickettsia felis is the etiologic agent of flea-borne spotted fever, with Ctenocephalides felis as its main vector and reservoir. Typically, the disease presents as acute fever associated with headache, asthenia, generalized maculo-papular rash, and in some cases, an inoculation eschar. In recent years, R. felis has acquired an important role in the etiology of the acute febrile syndrome; it is indeed an emerging infectious disease, albeit underdiagnosed. Indirect immunofluorescence assay (IFA) is currently the reference diagnostic method. However, this technique has limitations related to the cross reactivity among different species of rickettsiae. Herein, we describe a case of a 16 year-old patient with an acute febrile syndrome secondary to probable infection with R. felis.

The seroprevalence of human infection withRickettsia slovaca, in an area of northern Spain

An epidemiological survey was undertaken to explore human exposure to Rickettsia slovaca in two provinces of northern Spain. When IFAT were used to test 200 members of the general population for antibodies to rickettsiae of the spotted-fever group, six (3.3%) were found positive, presumably, since Dermacentor is one of the most common genera of human-biting tick in the study area, for antibodies to R. slovaca. Thirty-one (16.9%) of an additional 183 subjects who presented shortly after being bitten by ticks were also found seropositive. The difference in seroprevalence between the general and the tick-bitten populations was significant. Subject gender had no influence on seroprevalence in either population, although, in the tick-bitten group, age and occupation did have a significant influence on the prevalence recorded. Immunoblotting was used to confirm the presence of antibodies in the five subjects, all from the tick-bitten group, found to have acute infections. Three D. marginatus ticks obtained from three of these acute cases were found PCR-positive for R. slovaca DNA.

[The immune structure against q fever and tick-bite spotted fever group rickettsioses in the population and domestic animals of the Republic of Guinea]

The circulation of the rickettsiae R.africae and C.brunetii, the causative agents of African tick-bite spotted fever and Q fever, was first ascertained throughout the territory of the Republic of Guinea. The immune stratum against R.africae among the population varied 1.1 to 25.4% or 10.6+/-0.7% on average and that among the livestock did 0.6 to 18.8% or 7.6+/-0.6% on average. The proportion of sera to C,brunettii in the population was in the rage from 0.8 to 10.5% or 2.4+/-0.3% on average; that in livestock was 3.2 to 18.7% or 8.0+/-0.6% on average. However, many aspects of the circulation of rickettsiae, the pathology and importance of these fevers in the structure of morbidity in Guinea remain still unclarified and call for further investigations, by applying the current laboratory diagnostic tests for rickettsiosial diseases.

Detection of Rickettsia spp. and host and habitat associations of fleas (Siphonaptera) in eastern Taiwan

Rickettsia typhi and Rickettsia felis (Rickettsiales: Rickettsiaceae) are two rickettsiae principally transmitted by fleas, but the detection of either pathogen has rarely been attempted in Taiwan. Of 2048 small mammals trapped in eastern Taiwan, Apodemus agrarius Pallas (24.5%) and Mus caroli Bonhote (24.4%) (both: Rodentia: Muridae) were the most abundant, and M. caroli hosted the highest proportion of fleas (63.9% of 330 fleas). Two flea species were identified: Stivalius aporus Jordan and Rothschild (Siphonaptera: Stivaliidae), and Acropsylla episema Rothschild (Siphonaptera: Leptopsyllidae). Nested polymerase chain reaction targeting parts of the ompB and gltA genes showed six fleas to be positive for Rickettsia spp. (3.8% of 160 samples), which showed the greatest similarity to R. felis, Rickettsia japonica, Rickettsia conorii or Rickettsia sp. TwKM01. Rickettsia typhi was not detected in the fleas and Rickettsia co-infection did not occur. Both flea species were more abundant during months with lower temperatures and less rainfall, and flea abundance on M. caroli was not related to soil hardness, vegetative height, ground cover by litter or by understory layer, or the abundance of M. caroli. Our study reveals the potential circulation of R. felis and other rickettsiae in eastern Taiwan, necessitating further surveillance of rickettsial diseases in this region. This is especially important because many novel rickettsioses are emerging worldwide.

[Rickettsiosis is a neglected cause of fever in returned travellers]

We present two cases of rickettsial infections in travellers caused by Rickettsia typhi and R. africae respectively. The two cases illustrate the widely varying symptomatology and aetiology. Incidence and treatment of the disease are discussed. The diagnosis is complex, and we believe that rickettsiosis is an underestimated cause of fever in returned travellers from the tropics. In the past two years only 26 cases have been diagnosed in Denmark. Whenever rickettsiosis is clinically suspected, empiric treatment with doxycycline should be initiated.

[Evaluation of safety and pharmacotherapeutic efficacy of cycloferon in treatment of Astrakhan rickettsial fever]

Clinicopathogenetic impact of cycloferon, an endogenous interferon inductor, on the process of Astrakhan rikettsial fever, its complications and outcomes was analysed. The treatment scheme with addition of cycloferon to the complex therapy was optimized. The specificity of the disease clinical process and the level of the interferon status in the patients treated with cycloferon alone or with combination of the standard therapy and cycloferon was shown. It was observed that in the patients with moderate severity of the disease the combined use of the standard therapy and cycloferon was in favour of arresting the disease clinical signs (fever, headache, weakness, eruption, hepatomegaly, arthralgia and myalgia, lymphatic gland inflammation, primary affect) and lowered the hospitalization term vs. the standard therapy alone. In the patients with moderate severity of the disease the levels of the serous interferon-alpha before the treatment were found lower, while those of interferon-gamma were higher. The use of cycloferon in the treatment scheme resulted in increase of the interferon-alpha levels and decrease of the higher levels of interferon-gamma. The standard therapy in combination with cycloferon in the patients with moderate severity of the disease provided changes in the immune status: increase of the relative content of T- and B-lymphocytes and normalization of their absolute number. Normalization of the phagocytic activity and the coefficient of the active phagocytes, as well as increase of the phagocytic index, the levels of immunoglobulins G, A and M and the number of the circulating immune cells were stated. The standard therapy with addition of cycloferon resulted in normalization of the levels not only of succinic denydrogenase, lactate dehydrogenase and glucose-6-dehydrogenase but also of alpha-naphthylacetate esterase and alpha-naphthylbutirate esterase in the neutrophils, as well as of the whole spectrum of the monocyte enzymes, except NAD-diaphorase. The adverse reactions were observed in 2.5% of the cases (9 subjects). All of them were mild and did not require discontinuation of the drugs use.

Serological study of rickettsial diseases in human and rodent population in Chittoor dist. (A.P.)

In India the presence of Rickettsial disease in human is documented in many states however, the data on presence of Rickettsial infection in Andhra Pradesh is very scare. Therefore, a study was undertaken in Chittoor district (A.P.) to see the prevalence of Rickettsial infection in human and rodent population. 3-5 ml of human blood samples were collected from the patients attending the nearest hospitals of Tirumala, Tirupathi, Palmner and Chittoor areas. Live rodents were trapped and blood samples were collected from them during January and February 2008. Sera was separated and tested by Weil Felix test. Two hundred human sera samples were tested. Of these 39 samples were found reactive with Weil Felix antigen. Of the 39 reactive, 31 were male and 8 female. All the human samples were showing reactivity at 1:20 dilution. Out of the 343 rodents samples tested, only 24 samples were showing reactivity. These were reactive at 1:20, 1:40 and 1:80 dilutions with different types of Weil Felix antigens. Eight rodent sera samples were having titer 1:80 with Proteus OXK which is suggestive of presence of Scrub typhus in this region.

[Hemostatic disorders and their implication in the pathogenesis of Astrakhan rickettsial fever]

AIM

to define a role of hemostatic disorders in the pathogenesis of Astrakhan rickettsial fever (ARL).

SUBJECTS AND METHODS

Platelet functional activity and plasma hemostatic parameters were studied in 89 patients of moderate ARL.

RESULTS

The clinical manifestations of hemostatic disorders at the height of ARL were characterized by the appearance of typhoid maculopapular rashes in 91.4% of the patients, solitary elements of which were transformed to petechiae in 20% of cases. At convalescence (on day 10.2 +/- 1.3 of the disease), all eruptions regressed via pigmentation. At the peak of the fever, there were nasal hemorrhages and bleedings from the sites of injections; lowered platelet aggregation was detectable in the presence of thrombocytopenia at the height. Coagulation hemostasis changes were characterized only by elevated fibrinogen levels. Increased platelet functional activity and decreased fibrinogen concentrations were observed at convalescence.

CONCLUSION

The basis of the clinical manifestations of ARL is hemostatic disorders due to thrombocytopenia and diminished platelet functional activity. In early convalescence, there was improved platelet aggregatability; however, the increasing trend for the rate of aggregation and the radius of aggregates suggests a risk of thrombogenesis in convalescents, which requires their follow-up with obligatory hemostatic monitoring.

Short report: Rickettsia felis outer membrane protein A: a potential tool for diagnosis of patients with flea-borne spotted fever

Rickettsia felis infection in humans has been detected worldwide, causing an illness that could be confused with other viral and bacterial infections such as dengue fever. Despite the high incidence of infection in humans, reservoirs, and vectors, the definitive diagnosis of R. felis infection currently requires polymerase chain reaction and sequencing because its antigens are closely related to other rickettsiae, making serologic diagnosis problematic. In this work, we report the immune reactivity of sera from four patients infected with R. felis with recombinant peptides representing regions of outer membrane protein A of R. felis.

Rickettsial infections and their clinical presentations in the Western Province of Sri Lanka: a hospital-based study

BACKGROUND

Rickettsial infections are re-emerging. A study of the geographical distribution of rickettsial infections, their clinical manifestations, and their complications would facilitate early diagnosis.

METHODS

Thirty-one selected patients from the Western Province of Sri Lanka were studied for rickettsial species, clinical manifestations, and complications.

RESULTS

Of 31 patients with possible rickettsioses, 29 (94%) fell into the categories of confirmed, presumptive, or exposed cases of acute rickettsial infections (scrub typhus was diagnosed in 19 (66%), spotted fever group in eight (28%)). Early acute infection or past exposure was suggested in two (7%) cases; cross-reactivity of antigens or past exposure to one or more species was suggested in nine (31%). Seventeen out of 19 (89%) patients with scrub typhus had eschars. Nine out of 29 (32%) patients had a discrete erythematous papular rash: seven caused by spotted fever group, two by scrub typhus. Severe complications were pneumonitis in eight (28%), myocarditis in five (17%), deafness in four (14%), and tinnitus in two (7%). The mean duration of illness before onset of complications was 12.0 (SD 1.4) days. All patients except one made a good clinical recovery with doxycycline or a combination of doxycycline and chloramphenicol.

CONCLUSIONS

In a region representing the low country wet zone of Sri Lanka, the main rickettsial agent seems to be Orientia tsutsugamushi. Delay in diagnosis may result in complications. All species responded well to current treatment.

Serologic evidence of a Rickettsia akari-like infection among wild-caught rodents in Orange County and humans in Los Angeles County, California

We detected antibodies reactive with Rickettsia akari, the etiologic agent of rickettsialpox in humans and in 83 of 359 (23%) rodents belonging to several species, collected in Orange County, CA. Reciprocal antibody titers >1:16 to R. akari were detected in native mice and rats (Peromyscus maniculatus, P. eremicus, and Neotoma fuscipes) and in Old World mice and rats (Mus musculus, Rattus rattus, and R. norvegicus), representing the first time that antibodies reactive with this agent have been detected in four of these species and the first report of these antibodies in rodents and humans west of the Mississippi River. We then tested serum samples from individuals who used a free clinic in downtown Los Angeles and found that 25 of 299 (8%) of these individuals had antibody titers >1:64 to R. akari. Serologic evidence suggested that R. akari or a closely related rickettsia is prevalent among several rodent species at these localities and that infection spills over into certain segments of the human population. Isolation or molecular confirmation of the agent is needed to conclusively state that R. akari is the etiologic agent infecting these rodents.

Description of the first reported human case of spotted fever group rickettsiosis in urban Bangkok

Described herein is the clinical presentation of a patient from Bangkok, with fever, petechial rash, history of a tick bite, and a diagnosis of spotted fever rickettsiosis.

Rickettsial infection in capybaras (Hydrochoerus hydrochaeris) from São Paulo, Brazil: serological evidence for infection by Rickettsia bellii and Rickettsia parkeri

INTRODUCTION

In Brazil, capybaras (Hydrochoerus hydrochaeris) are important hosts for Amblyomma ticks, which in turn can transmit rickettsiae to humans and animals. Therefore, capybaras are potential sentinels for rickettsial infection.

OBJECTIVE

The present study evaluated rickettsial infection in capybaras in different areas of the state of São Paulo, where rickettsiosis has never been reported. Materials and methods. Blood sera from 73 capybaras from six localities in São Paulo were tested by indirect immunofluorescence assay using Rickettsia rickettsii, Rickettsia parkeri, and Rickettsia bellii antigens. Capybara spleens were tested by PCR, targeting a fragment of the rickettsial gltA gene. Ticks were collected from each capybara sample and taxonomically identified to species.

RESULTS

A total of 94 positively reacting capybara samples, 19 (26.0%), 25 (34.2%), and 50 (68.5%) capybara sera reacted to R. rickettsii, R. parkeri, and R. bellii, respectively. Twenty-five capybara sera showed titers to R. bellii at least four-fold higher than to any of the other two antigens. These sera were considered homologous to R. bellii. Using the same criteria, 3 capybara sera were considered homologous to R. parkeri. No sera were be considered homologous to R. rickettsii. No rickettsial DNA was detected in capybara spleen samples. Ticks collected on capybaras were Amblyomma dubitatum and Amblyomma cajennense.

CONCLUSIONS

The first evidence is reported of R. bellii natural infection in vertebrate hosts, and the first evidence of R. parkeri infection in capybaras. While R. parkeri is known to infect and cause disease in humans, no similar evidence for human infection has been indicated by R. bellii.

Prevalence of Rickettsia felis DNA in the blood of cats and their fleas in the United States

Rickettsia felis is associated with fever, headache, myalgia, and macular rash in some infected humans and has been detected in the cat flea (Ctenocephalides felis) in many countries around the world. While some naturally exposed cats have been assessed for antibodies against R felis, to our knowledge, no one has reported use of polymerase chain reaction (PCR) to attempt to amplify R felis DNA from client-owned cats and the fleas collected from them. In this study, we assayed 92 pairs of cat blood and flea extracts from Alabama, Maryland and Texas, using PCR assays that amplify a region of the citrate synthase gene (gltA) and the outer membrane protein B gene (ompB). Of the 92 pairs, 62 of 92 (67.4%) flea extracts and none of the cat blood samples were positive for R felis DNA.

Detection of Rickettsia rickettsii and Rickettsia sp. in blood clots in 24 patients from different municipalities of the State of Sao Paulo, Brazil

The authors detected Rickettsia genus organisms using shell vial and polymerase chain reaction (PCR)/sequencing analysis in blood clots in patients suspected of having Brazilian spotted fever (BSF). DNA was detected using PCR with three sets of primers to access the gltA, ompA, and ompB genes. Sequence analysis was carried out using an automatic sequencer with Bioedit software. Seventy-five percent of the culture samples were positive and all samples amplified rickettsial gene fragments. To date, 46% of the samples have been sequenced.

Low Incidence of Tick-Borne Rickettsiosis in a Spanish Mediterranean Area

The aim of this study was to know the incidence of tick-borne rickettsial disease in a Mediterranean area. The incidence in 5 years for 100,000 inhabitants was 1.7 for tick-borne-lymphadenopathy (TIBOLA) and 0.4 for Mediterranean spotted fever (MSF). MSH incidence during the last few years has been lower than expected; in contrast TIBOLA seems to be an emerging disease. At the present time our data suggest a low tick-borne rickettsiosis incidence of MSF and a superior incidence of TIBOLA than MSF in the Spanish Mediterranean area.

Reemergence of Rickettsiosis in Oran, Algeria

The presumptive cases of Mediterranean spotted fever have been identified in 1993 and since that time, its frequency has steadily increased. The prospective study, in summer 2004, was conducted in order to present the descriptive clinic and epidemiology, to identify more severe forms, the presence of the multiple eschars, and different rickettsial strains caused the disease in our region. In Oran, the cases were diagnosed clinically. In Marseille, serum specimens were tested by IFA using the panel of eight rickettsial antigen; Western blot and cross-adsorption studies were also performed in order to confirm the diagnosis. Ninety-three patients clinically diagnosed were recorded from July 3 to October 28, 2004. Eighty percent were male, the mean age was 44.3 years, 90% were exposed to dog and 32% reported tick bites. Clinical signs were as follow: presence of underlying disease (44%), sudden onset (78%), fever (100%), loss of weight (63%), conjunctivitis (43%), and a tache noire was noticed in 70%. Interestingly, two patients had two and three eschars, respectively. The rash was maculopapular (palm and sole) and purpuric in nine cases. Doxycycline was the most antibiotic (91%) with favourable outcome in 91% of the cases. Malignant form with death is reported for three patients (3.2%). Among the 93 patients, 104 serum from 65 patients were tested (serums of others patients were lost or ticket not found on tube. Sixty-three patients out of 65 had a positive serology by IFA with cross-reactive antibodies especially between R. conorii, R. felis and/or R. typhi. Two others negative serology were: one precocious serum and second from the patient, which presented symptoms of MSF and tested two serums, Western blot and cross-adsorption.

Proposal to Create Subspecies of Rickettsia sibirica and an Emended Description of Rickettsia sibirica

The Rickettsia sibirica species is composed of isolates that are genotypically close but can be classified within two distinct serotypes, that is, R. sibirica sensu stricto and R. sibirica mongolitimonae (incorrectly named R. mongolotimonae). We investigated the possibility of classifying rickettsiae closely related to R. sibirica as R. sibirica subspecies, as proposed by the ad hoc Committee on Reconciliation of Approaches to Bacterial Systematics. For this, we first estimated the genotypic variability by using multilocus sequence typing (MLST), including the sequencing of five genes, and multispacer typing (MST) using three intergenic spacers, of five isolates and three tick amplicons of R. sibirica sensu stricto and six isolates of R. sibirica mongolotimonae. Then, we selected a representative of each MLST genotype and used mouse serotyping to estimate their degree of taxonomic relatedness. Among the 14 isolates or tick amplicons studied, 2 MLST genotypes were identified: (i) the R. sibirica sensu stricto type; and (ii) the R. sibirica mongolitimonae type. Representatives of the two MLST types were classified within three MST types and into two serotypes. Therefore, as isolates within the R. sibirica species are genotypically homogeneous but show MST genotypic, serotypic, and epidemio-clinical dissimilarities, we propose to modify the nomenclature of the R. sibirica species through the creation of subspecies. We propose the names R. sibirica subsp. sibirica subsp. nov. (type strain = 2-4-6, ATCC VR-541(T)), and R. sibirica subsp. mongolitimonae subsp. nov. (type strain = HA-91, ATCC VR-1526(T)). The description of R. sibirica is emended to accommodate the two subspecies.

Human Infection with Rickettsia honei, Thailand

Human spotted fever rickettsiosis was detected molecularly by 2 real-time polymerase chain reaction (PCR) assays performed on DNA extracted from a Thai patient's serum sample. Sequences of PCR amplicons from 5 rickettsial genes used for multilocus sequence typing were 100% identical with those deposited with GenBank for Rickettsia honei TT-118.

Serological evidence of Rickettsia infections in forestry rangers in north-eastern Italy

The prevalence of antibodies to Rickettsiae and other tick-borne microrganisms in the sera of 181 forestry rangers from Friuli-Venezia-Giulia, Italy, was examined. Seven (3.9%) sera were positive for Rickettsia conorii and Rickettsia helvetica, as single or dual infections; four of these sera had been found previously to be positive for Borrelia burgdorferi. Antibodies to Coxiella burnetii were detected in five (2.8%) sera, four of which were also positive for B. burgdorferi. These findings indicate that patients in this north-eastern Italian region with fever subsequent to tick-bite should be investigated for Rickettsia and Coxiella infections.

Serological evidence of infection with Rickettsia typhi and Rickettsia felis among the human population of Catalonia, in the northeast of Spain

Murine typhus (MT) is a cause of fever of intermediate duration in the south of Spain. Rickettsia typhi has been described as the MT etiological agent. Rickettsia felis produces an infection similar to MT. The aim of the study is to determine their seroprevalence in humans in Catalonia. Antibodies to Rickettsia typhi and Rickettsia felis from 217 serum samples were examined by indirect immunofluorescence assay (IFA). Age, gender, residence area, contact with animals, and occupation were surveyed. Rickettsia typhi and Rickettsia felis seroprevalences were 8.8% and 3.2%, respectively. Rickettsia typhi was present in 7.6% of the samples in urban, 8.5% in semirural, and in 21.4% in rural areas, whereas Rickettsia felis was present in 3.5% in urban, 1.7% in semirural, and 7.1% in rural area. The only statistically significant association observed was that between Rickettsia felis seropositivity and age. Our data seem to indicate the presence of Rickettsia typhi and Rickettsia felis in humans in Catalonia.

Spotted fever group and typhus group rickettsioses in humans, South Korea

Multiplex-nested PCR and sequencing analysis indicated rickettsialike agents in serum specimens from febrile patients.

The presence of the nucleic acid of the spotted fever group (SPG) and typhus group (TG) rickettsiae was investigated in 200 serum specimens seropositive for SFG rickettsiae by multiplex-nested polymerase chain reaction with primers derived from the rickettsial outer membrane protein B gene. The DNA of SFG, TG, or both rickettsiae was amplified in the 24 serum specimens, and sequence analysis showed Rickettsia conorii, R. japonica, and R. felis in the specimens. R. conorii and R. typhi were found in 7 serum specimens, which indicated the possibility of dual infection in these patients. These findings suggest that several kinds of rickettsial diseases, including boutonneuse fever, rickettsialpox, R. felis infection, and Japanese spotted fever, as well as scrub typhus and murine typhus, are occurring in Korea.

Tropenr�ckkehrerin mit papulovesikul�rem Exanthem und grippe�hnlichen Beschwerden

African tick bite fever (ATBF) is an infectious disease commonly observed in travelers to sub-Saharan Africa. Because the presentation of the disease is often not specific, ATBF is frequently not diagnosed or confused with Mediterranean spotted fever. We present the case of a 63-year-old woman with typical history and symptoms. The diagnosis of ATBF was serologically confirmed by immunofluoroscence. ATBF is an important differential diagnosis of fever in patients returning from sub-Saharan Africa.

A study of'febrile illnesses on the Thai-Myanmar border: predictive factors of rickettsioses

We have performed a case-control analysis to determine the significance of clinical, laboratory and epidemiological features as predictive factors of rickettsioses among patients in Sangkhla Buri, Thailand (Thai-Myanmar border). Fifteen serologically-confirmed rickettsiosis patients including Spotted Fever Group (SFG) rickettsioses, scrub typhus, and murine typhus were classified as 'cases'; one hundred and sixty-three acutely febrile patients presenting to the same hospital during the same time period, who had no serological evidence of acute rickettsiosis, were classified as 'controls'. Patients' report of rash/arthropod bite [Odds ratio (OR) 22.90, 95% CI (confidence interval) 6.23, 84.13] and history of jungle trips (OR 5.30, 95% CI 1.69-16.62) were significant risk factors. Elevated ALT (OR 3.04, 95% CI 1.04, 8.88) and depressed platelet count (OR 3.38, 95% CI 1.13, 10.10) were also useful differentiating markers of rickettsioses in this population. Definitive diagnosis of rickettsioses is difficult without specialized diagnostic capabilities that are rarely available in remote areas such as Sangkhla Buri, where other acute febrile illnesses with similar presentation are commonly found. The relative importance of predictive factors presented here may provide clinicians with some useful guidance in distinguishing rickettsioses from other acute febrile illnesses. Timely administration of empiric treatment in highly suspicious cases can deter potential morbidity from these arthropod-borne infections.

Aneruptive fever associated with antibodies to Rickettsia helvetica in Europe and Thailand

We report that eight patients from France, Italy, and Thailand had serological evidence of Rickettsia helvetica infection. The infection presented as a mild disease in the warm season and was associated with fever, headache, and myalgia but not with a cutaneous rash. R. helvetica should be suspected in patients with unexplained fever, especially following a bite from an Ixodes sp. tick.

Sequential changes in hematologic and biochemical parameters in African tick bite fever

OBJECTIVE

To evaluate the sequential changes and to estimate the frequencies of abnormalities in some commonly measured biological variables in patients with African tick bite fever (ATBF), an emerging spotted fever group (SFG) rickettsiosis in international travelers to rural sub-Saharan Africa.

METHODS

A study was done of hemoglobin, total leukocyte count, absolute lymphocyte count, blood platelet count and serum levels of C-reactive protein (S-CRP), alanine aminotransferase (S-ALAT), aspartate aminotransferase, lactic dehydrogenase, gamma-glutamyl transferase, alkaline phosphatase, bilirubin, sodium and creatinine during the first two weeks of illness and prior to the institution of antirickettsial therapy in 108 patients with travel-associated ATBF.

RESULTS

There were significant falls in mean total leukocyte count, mean absolute lymphocyte count, and mean platelet count, and significant increases in mean S-CRP and S-ALAT. During the first ten days of illness, elevated S-CRP, lymphopenia and elevated S-ALAT were detected in 91.7%, 73.3% and 40.7% of patients, respectively. Most abnormalities were mild. For 55 patients who underwent both S-CRP and absolute lymphocyte count determination, at least one parameter was abnormal in 52 (94.5%) patients.

CONCLUSIONS

The sequential changes in many biological parameters during the acute phase of ATBF mimic those reported in other SFG rickettsioses. Mild abnormalities are frequent, with increased S-CRP and lymphopenia being the two most consistent findings.

Systemic inflammatory responses in African tick-bite fever

Information regarding the inflammatory response in African tick-bite fever (ATBF), an emerging spotted-fever-group rickettsiosis, in international travelers to sub-Saharan Africa, is scarce. Plasma/serum levels of von Willebrand factor (vWF), soluble (s) E-selectin, tumor necrosis factor-alpha, interleukin (IL)-6, interferon-gamma, IL-10, IL-13, IL-8, RANTES, macrophage inflammatory protein-1alpha, and C-reactive protein were studied, at both first presentation and follow-up, in 15 patients with travel-associated ATBF and in 14 healthy travelers who served as control subjects. Our main and novel findings are the following: (1) patients with ATBF had increased levels of vWF and sE-selectin, with a subsequent decrease at follow-up; (2) with the exception of IFN-gamma, levels of cytokines and chemokines were also increased in these patients at the first presentation; and (3) IL-10 and IL-13 tended to increase during follow-up, whereas most of the inflammatory cytokines decreased. The induction of these mediators and the balance between them may be critical both for the regulation of inflammation and for protective immunity in ATBF.

Characterization of spotted fever group rickettsiae detected in dogs and ticks in Okinawa, Japan

Spotted fever group (SFG) rickettsial DNAs were detected in 2.4% of 340 canine blood samples and a pool of 84 tick pool samples (229 ticks) collected in Okinawa, Japan by PCR using a citrate synthase and an SFG rickettsial 190-kDa surface antigen gene primer pair. The sequences of both genes from canine blood and tick samples showed high levels of similarity with those of Rickettsiajaponica and several SFG rickettsiae (R. aeschlimannii, R. massiliae, R. rhipicephali and Bar-29 strain). Phylogenesis of canine blood and tick samples was closely related to that of reference SFG rickettsiae. Serological evidence of SFG rickettsial infection in dogs and humans in Okinawa, where no clinical human cases have been reported, has been obtained. In this study, genetical characterization of SFG rickettsia in Okinawa was investigated phylogenetically.

Isolation and PCR detection of rickettsiae from clinical and rodent samples in Malaysia

Isolation of rickettsiae from patients' blood samples and organ samples of wild rodents from areas with high seroprevalence of rickettsial infections was attempted using cell culture assay and animal passages. L929 mouse fibroblast cells grown in 24 well tissue culture plate were inoculated with buffy coat of febrile patients and examined for the growth of rickettsiae by Giemsa, Gimenez staining and direct immunofluorescence assay. No rickettsiae were isolated from 48 patients' blood samples. No symptomatic infections were noted in mice or guinea pigs infected with 50 organ samples of wild rodents. There was no rickettsial DNA amplified from these samples using various PCR detection systems for Orientia tsutsugamushi, typhus and spotted fever group rickettsiae.

Prevalence of Rickettsia conorii and Rickettsia typhi infections in the population of northern Greece

Seroepidemical surveys concerning the prevalence of Rickettsia conorii and Rickettsia typhi have never been studied in northern Greece. We examined 1,584 sera samples from residents of northern Greece for the detection of antibodies to R. conorii and to R. typhi by means of immunofluorescence assay. In addition, we compared the prevalence of rickettsial infections among the demographic variables of sex, age, occupation, and area of residence. Antibodies to R. conorii and R. typhi were found in 125 (7.9%) and 31 (2.0%) of the examined subjects, respectively. The prevalence of antibodies to R. conorii correlated with increasing age and was statistically higher in men. Farmers had significantly higher prevalence of antibodies to both species of rickettsiae studied versus other professions. Residents of rural areas showed a statistically higher prevalence for R. conorii versus urban residents, although this difference was not demonstrated for R. typhi. We also detected differences in the prevalence of rickettsial infections among the different prefectures. Our data show the wide distribution of R. conorii in northern Greece and indicate the presence of R. typhi.

Epidemiological, clinical and laboratory characteristics of 19 serologically confirmed rickettsial disease in Singapore

AIM

To identify epidemiological, clinical and laboratory features of serologically-proven typhus in the local setting.

METHOD & RESULTS

Retrospective study looking at rickettsial serologies done over a six-month period and collection of the epidemological, clinical, laboratory and treatment response data from the case notes of the patients with an ordered rickettsial serology. Twenty of the 35 cases had a positive serology. Of these 20 patients, 18 were already clinically diagnosed as having murine typhus. All except one were males and all were migrant workers. Majority of the patients were construction workers staying in containers where rats abound. The most consistent clinical features were high fever (100%) for a median period of seven days, headache (94%) and cough (47%). The white cell count was usually normal (74%) but thrombocytopenia was common (68%). Transaminitis was also common (90%) with the AST component higher than the ALT in half of the cases. Response to doxycycline therapy was rapid and most (88%) were afebrile by 72 hours.

CONCLUSION

Typhus (notably murine type) can be confidently diagnosed from consistent clinical features supported by epidemiological and laboratory clues. Early recognition with the prompt treatment response will result in shorter hospital stay with decreased cost. Serological testing may only prove useful in difficult situations when the clinical diagnosis is less clear.

Detection of serum IgG antibodies specific for Wolbachia surface protein in rhesus monkeys infected with Brugia malayi

The mechanism of lymphedema development in individuals with lymphatic filariasis is presently poorly understood. To investigate whether Wolbachia, symbiotic bacteria living within filarial nematodes, may be involved in disease progression, Wolbachia-specific immune responses were assayed in a group of Brugia malayi-infected rhesus monkeys. Serum IgG antibodies specific for a major Wolbachia surface protein (WSP) were detected in 2 of 12 infected monkeys. It is interesting that both of these monkeys developed lymphedema after becoming amicrofilaremic. WSP-specific antibody responses were temporally associated with increases in antifilarial IgG1 antibodies as well as lymphedema development. These findings suggest that Wolbachia may be important in understanding disease caused by filarial worms.

Rickettsial infection in murine models activates an early anti-rickettsial effect mediated by NK cells and associated with production of gamma interferon

Natural killer (NK) cell activity was significantly increased on days 2-6 of infection in the Rickettsia conorii-infected C3H/HeN mice and on day 2 in the Rickettsia typhi-infected C57BL/6 mice. Depletion of NK cell activity utilizing anti-NK1.1 monoclonal antibody enhanced the susceptibility of normally resistant C57BL/6 mice to infection with R. typhi, and depletion of NK cell activity with antibody to asialo GM1 enhanced the susceptibility of C3H/HeN mice to infection with R. conorii. Serum gamma interferon was increased in R. conorii-infected C3H/HeN mice compared with NK cell-depleted, infected mice during the early course of infection. Additionally, the NK cell activating cytokine IL-12 was elevated in the sera of infected mice during the time period representing enhanced NK cell activity compared with uninfected mice. Thus, it appears that NK cells contribute to the early anti-rickettsial immune response, likely via a mechanism involving gamma interferon.