Rickettsia conorii Israeli tick typhus strain isolated from Rhipicephalus sanguineus ticks in Portugal

This report describes the first establishment of five isolates of R. conorii Israeli tick typhus (ITT) strain from Rhipicephalus sanguineus ticks in different regions of Portugal. Ticks were collected on two separate expeditions that took place in Bragan?a, Montesinho Natural Park, and Portalegre City.     

Ultrastructural study of the infection process of Rickettsia conorii in the salivary glands of the vector tick Rhipicephalus sanguineus

This work was designed to study the infection process of Rickettsia conorii in the salivary glands of experimentally infected Rhipicephalus sanguineus ticks. One hundred six uninfected engorged nymphs were intracelomically inoculated with approximately 2 x 10(3) plaque-forming units of a rickettsial suspension. After the molt, unfed and fed adults were dissected, and the salivary glands were extracted and processed for transmission electron microscopy observation. Three different uninfected control groups were used for (1) evaluating the impact of the inoculation procedure, (2) establishing the feeding period of infected ticks, and (3) ultrastructural characterization of the salivary glands. Overall, 75.5% (80 of 106) of the nymphs inoculated with rickettsiae died during the molt or soon after hatching into adult instars; 50% (12 of 24) of the remaining infected adults showed severe malformations compromising their viability. In apparently healthy specimens, time of engorgement was longer. The contrast with the negative control groups was statistically significant, suggesting that R. conorii exerts a strong negative effect on the vector ticks. The ultrastructural study showed that in the salivary glands of infected ticks, rickettsial growth occurs preferentially in central, peripheral, and interstitial acini cells.     

Experimental infection of dogs with a Zimbabwean strain of Rickettsia conorii.

Seroconversion was demonstrated in dogs artificially infected with a Zimbabwean strain of Rickettsia conorii. No haematological or biochemical abnormalities were found and the only clinical signs observed were pain, erythema and oedema at the inoculation site and regional lymphadenopathy. Intermittent rickettsaemia was detected using the centrifugation shell vial technique up to 10 days post inoculation.     

Ehrlichia species in Rhipicephalus sanguineus ticks in Cameroon

Ehrlichia and Anaplasma species are tick-transmitted obligately intracellular bacteria that commonly cause disease in dogs worldwide. In addition to causing disease in canines, Ehrlichia chaffeensis, Ehrlichia ewingii, and Anaplasma phagocytophilum are responsible for emerging and life-threatening human zoonoses in the United States. We previously reported a high prevalence of E. canis infection in Cameroonian dogs based on serologic and molecular evidence. This study was undertaken to determine the Ehrlichia species (E. canis, E. chaffeensis, E. ewingii) present in Rhipicephalus sanguineus ticks (n = 92) collected from those dogs (n = 51). Ehrlichial DNA was detected by real-time polymerase chain reaction (PCR) in 28 (30%) unengorged R. sanguineus ticks attached to dogs. E. canis, the causative agent of canine monocytic ehrlichiosis, was detected in 19 (21%) ticks from 15 dogs, E. ewingii was detected in six (6%) ticks from 6 dogs, and E. chaffeensis, the etiologic agent of human monocytotropic ehrlichiosis, was detected in 4 (4%) ticks. Notably, 2 ticks were coinfected with E. chaffeensis and E. canis, one tick with E. canis and E. ewingii, and one tick with E. chaffeensis and E. ewingii. These findings further support our previous conclusion that multiple Ehrlichia species are present in Cameroon and identify R. sanguineus ticks primarily infected with E. canis, but suggest that they may be infected with and transmit other ehrlichial agents in Cameroon, potentially to humans.     

A focus of dogs and Rickettsia massiliae-infected Rhipicephalus sanguineus in California

A recurrent focus of Rhipicephalus sanguineus infestation was investigated in a suburban area of southern California after reports of suspected Rocky Mountain spotted fever in two dogs on the same property. Abundant quantities of Rh. sanguineus were collected on the property and repeatedly from each dog, and Rickettsia massiliae DNA was detected by polymerase chain reaction (PCR). Whole blood and serum samples from four dogs were tested by using PCR and microimmunofluorescent assay for antibodies against spotted fever group rickettsiae. Serum samples from all four dogs contained antibodies reactive with R. massiliae, R. rhipicephali, R. rickettsii, and 364D Rickettsia but no rickettsial DNA was detected by PCR of blood samples. Serum cross-absorption and Western blot assays implicated R. massiliae as the most likely spotted fever group rickettsiae responsible for seropositivity. To our knowledge, this is the first detection of R. massiliae in ticks in California.     

Atypical papulovesicular rash due to infection with Rickettsia conorii.

We present an unusual case of Rickettsia conorii infection that was associated with cutaneous papulovesicular lesions on a patient who had returned from the bushveld of South Africa. The lesions were diffusely scattered across the trunk, extremities, and both palms. Several recent reports have documented similar papulovesicular or pustulovesicular rashes that occurred on travelers returning from southern Africa. These rashes resemble the lesions of rickettsialpox. Evidence suggests that these atypical exanthems may be due to variant strains of R. conorii or to an unusual host response to infection with this organism; thus, infection with R. conorii should be included in the list of diseases that cause poxlike lesions.     

Seroprevalence of Rickettsia typhi and Rickettsia conorii infection among rodents and dogs in Egypt

A serological survey of 1813 rodent and 549 dog sera, collected from 1979 to 1986 from animals in 16 Egyptian Governorates were tested for antibody to Rickettsia typhi and Rickettsia conorii by the indirect fluorescent antibody test. Only three of 82 (4%) sera from Rattus rattus collected near Aswan had antibody to R. conorii. The prevalence of R. typhi antibody in dog sera was only 0.4% (n = 549) while 25% (n = 547) of Rattus norvegicus and 11% (n = 1138) of R. rattus had measurable antibodies. Among the other rodents, antibody was demonstrated in only 2% (n = 45) of Arvicanthis spp., and 1% (n = 83) of Acomys spp. Collectively, rodents captured in the Nile Delta had a higher prevalence (mean 24% (n = 787] than those captured in the Nile Valley (mean 4% (n = 650]. Antibody to R. typhi was detected in rodents collected in all port cities: ismailiya, 13%; Port Said, 9%; Suez, 9%; Safaga, 16%; Quseir, 32% and Alexandria, 34%. These data showed evidence of R. typhi infection among rodents in widespread geographic localities of Egypt and suggested that infected rodents may be a source of human infections.     

Antigenic diversity of Rickettsia conorii.

Analysis of seven strains designated as Rickettsia conorii for reactivity with a panel of 12 monoclonal antibodies to surface-protein epitopes of spotted fever group rickettsiae and by Western immunoblotting with standard serotyping sera revealed remarkable antigenic diversity. Rickettsial strains from France, Morocco, Ethiopia, Kenya, South Africa, India, and the USSR differed from one another in reactivity with at least one and as many as five monoclonal antibodies. Simko and Indian strains were similar to one another and differed substantially from other R. conorii strains. All seven strains reacted with three R. conorii-specific monoclonal antibodies. Western immunoblotting demonstrated a major 120-kD protein and a major 135-kD protein in all strains. The principal differences were the presence of a major undenatured 130-kD protein in all strains except Indian and Simko, which had an analogous protein of 124 kD. Immunodominant antigenically related, heat-denatured protein bands of 170 kD (Malish 7 strain), 175 kD (Manuel strain), and 190 kD (Kenya tick typhus, Indian, and Simko strains) were not detected in the M-1 and Moroccan strains. This antigenic diversity is greater than that previously reported for other spotted fever group rickettsial species, suggesting that R. conorrii is an older species than R. rickettsii with a longer period of time for evolutionary divergence.     

Experimental infection of opossums Didelphis aurita by Rickettsia rickettsii and evaluation of the transmission of the infection to ticks Amblyomma cajennense

The present study evaluated the infection of opossums (Didelphis aurita) by Rickettsia rickettsii and their role as amplifier hosts for horizontal transmission of R. rickettsii to Amblyomma cajennense ticks. Three groups of opossums were evaluated: on day 0, group 1 (G1) was inoculated intraperitoneally with R. rickettsii; group 2 (G2) was infested by R. rickettsii-infected ticks; and group 3 (G3) was the uninfected control group. Opossum rectal temperature was measured daily. Blood samples were collected every 2 to 4 days during 30 days, and used to (1) inoculate guinea pigs intraperitoneally; (2) extract DNA followed by real-time polymerase chain reaction (PCR) targeting the rickettsial gene gltA; (3) study hematology; (4) detect R. rickettsii-reactive antibodies by indirect immunofluorescence assay (IFA). Blood was also collected every 10 days from days 30 to 180, to be tested by serology. Opossums were infested by uninfected A. cajennense larvae and nymphs from days 3 to 15. Engorged ticks were collected and allowed to molt in an incubator. Thereafter, the subsequent flat ticks were allowed to feed on uninfected rabbits, which were tested for seroconversion by IFA. Samples of flat ticks were also tested by real-time PCR. All G1 and G2 opossums became infected by R. rickettsii, as demonstrated by realtime PCR or/and guinea pig inoculation, but they showed no clinical abnormality. Rickettsemia was first detected at days 2 to 8, lasting intermittently till days 1 to 30. Approximately 18% and 5% of the flat ticks previously fed on G1 and G2 opossums, respectively, became infected by R. rickettsii, but only the rabbits infested with G1-derived ticks seroconverted. The study demonstrated that R. rickettsii was capable of infecting opossums without causing illness and developing rickettsemia capable of causing infection in guinea pigs and ticks, although the infection rate in ticks was low.     

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.     

Detection of Rickettsia africae in Rhipicephalus (Boophilus) decoloratus ticks from the Republic of Botswana, South Africa

A total of 53 engorged adult ticks belonging to the species Rhipicephalus (Boophilus) decoloratus (N = 9), Rhipicephalus evertsi evertsi (N = 27), Rhipicephalus appendiculatus (N = 9), Amblyomma hebraeum (N = 5), and Hyalomma marginatum turanicum (N = 3), were removed from oryx in Botswana (South Africa). They were tested for the presence of spotted fever group (SFG) Rickettsia and Anaplasma phagocytophilum using polymerase chain reaction (PCR). Seventy-seven percent of R. decoloratus as well as twenty percent of A. hebraeum were positive for ompA, gltA and 16S rRNA SFG Rickettsia PCR assays. All nucleotide sequences were homologous to Rickettsia africae, the agent of African tick-bite fever (ATBF). None of the tested ticks was positive for 16S rRNA A. phagocytophilum PCR assays. These results suggest for the first time that R. decoloratus ticks may be reservoirs of R. africae, and support the ATBF risk in this area.     

Host- and microbe-related risk factors for and pathophysiology of fatal Rickettsia conorii infection in Portuguese patients

BACKGROUND: The pathophysiologic mechanisms that determine the severity of Mediterranean spotted fever (MSF) and the host-related and microbe-related risk factors for a fatal outcome are incompletely understood. METHODS: This prospective study used univariate and multivariate analyses to determine the risk factors for a fatal outcome for 140 patients with Rickettsia conorii infection admitted to 13 Portuguese hospitals during 1994-2006 with documented identification of the rickettsial strain causing their infection. RESULTS: A total of 71 patients (51%) were infected with the Malish strain of Rickettsia conorii, and 69 (49%) were infected with the Israeli spotted fever (ISF) strain. Patients were admitted to the intensive care unit (40 [29%]), hospitalized as routine inpatients (95[67%]), or managed as outpatients (5[4%]). Death occurred in 29 adults (21%). A fatal outcome was significantly more likely for patients infected with the ISF strain, and alcoholism was a risk factor. The pathophysiology of a fatal outcome involved significantly greater incidence of petechial rash, gastrointestinal symptoms, obtundation and/or confusion, dehydration, tachypnea, hepatomegaly, leukocytosis, coagulopathy, azotemia, hyperbilirubinemia, and elevated levels of hepatic enzymes and creatine kinase. Some, but not all, of these findings were observed more often in ISF strain-infected patients. CONCLUSIONS: Although fatalities and similar clinical manifestations occurred among both groups of patients, the ISF strain was more virulent than the Malish strain. Multivariate analysis revealed that acute renal failure and hyperbilirubinemia were most strongly associated with a fatal outcome.