Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These zoonoses are among the oldest known vector-borne diseases. However, in the past 25 years, the scope and importance of the recognized tick-associated rickettsial pathogens have increased dramatically, making this complex of diseases an ideal paradigm for the understanding of emerging and reemerging infections. Several species of tick-borne rickettsiae that were considered nonpathogenic for decades are now associated with human infections, and novel Rickettsia species of undetermined pathogenicity continue to be detected in or isolated from ticks around the world. This remarkable expansion of information has been driven largely by the use of molecular techniques that have facilitated the identification of novel and previously recognized rickettsiae in ticks. New approaches, such as swabbing of eschars to obtain material to be tested by PCR, have emerged in recent years and have played a role in describing emerging tick-borne rickettsioses. Here, we present the current knowledge on tick-borne rickettsiae and rickettsioses using a geographic approach toward the epidemiology of these diseases.

Update on Tick-Borne Rickettsioses around the World: a Geographic Approach

Rodents are the most abundant and diversified order of living mammals in the world. Already since the Middle Ages we know that they can contribute to human disease, as black rats were associated with distribution of plague. However, also in modern times rodents form a threat for public health. In this review article a large number of pathogens that are directly or indirectly transmitted by rodents are described. Moreover, a simplified rodent disease model is discussed.

Rodent-borne diseases and their risks for public health

Hantaviruses are enveloped RNA viruses each carried by a specific rodent species. Three hantaviruses, Puumala, Dobrava, and Saaremaa viruses, are known to cause haemorrhagic fever with renal syndrome. In Europe. Puumala causes a generally mild disease, nephropathia epidemica, which presents most commonly with fever, headache, gastrointestinal symptoms, impaired renal function, and blurred vision, whereas Dobrava infections often also have haemorrhagic complications. There are few available data about the clinical picture of confirmed Saaremaa infections, but epidemiological evidence suggests that it is less pathogenic than Dobrava, and that Saaremaa infections are more similar to nephropathia epidemica caused by Puumala. Along with its rodent host, the bank vole (Clethrionomys glareolus), Puumala is reported throughout most of Europe (excluding the Mediterranean region), whereas Dobrava, carried by the yellow-necked mouse (Apodemus flavicollis), and Saaremaa, carried by the striped field mouse (Apodemus agrarius), are reported mainly in eastern and central Europe. The diagnosis of acute hantavirus infection is based on the detection of virus-specific IgM. Whereas Puumala is distinct, Dobrava and Saaremaa are genetically and antigenically very closely related and were previously thought to be variants of the same virus. Typing of a specific hantavirus infection requires neutralisation antibody assays or reverse transcriptase PCR and sequencing.

Hantavirus infections in Europe.

In 1977, microbiologists and clinicians were awakened to the importance of the genus Campylobacter when it was learned that one species, Campylobacter jejuni, was a major cause of human enteritis. In the following decade substantial advances were made in diagnosis, isolation technology, identification, classification, serotyping, and epidemiology. The genus has undergone rapid expansion as advantage was taken of the deoxyribonucleic acid-deoxyribonucleic acid hybridization technique in defining new species. The 14 species now included in the genus, however, constitute a widely diverse group, and one species, C. pylori, which is associated with human gastroduodenitis, is under consideration for reassignment to another genus. The nomenclature of the subspecies of C. fetus has been resolved and the role of C. fetus subsp. fetus as an agent of human infections has been more clearly defined. The thermophilic campylobacteria that are etiological agents of human enteritis now include three species, C. jejuni, C. coli, and C. laridis. Recently defined species that have also been implicated as enteritis-causing agents include C. hyointestinalis, "C. upsaliensis," "C. cinaedi," and "C. fennelliae." The aerotolerant campylobacteria are now included in the species C. cryaerophila, and the campylobacteria isolated from salt marshes are included in C. nitrofigilis. The taxonomy and nomenclature of C. sputorum have been revised. C. sputorum now consists of three biovars (biotypes). Two of these, biovar sputorum and biovar bubulus, were previously considered to be separate subspecies and the third, biovar fecalis, was previously regarded as a separate species and known as "C. fecalis." The former subspecies C. sputorum subsp. mucosalis has been elevated to the rank of species. C. mucosalis is metabolically closely related to C. consisus. Human pathogens have not been identified among C. sputorum, C. mucosalis, or C. concisus. The goal of this article is to review developments during the last 10 years with emphasis on changes in taxonomy that are important from the perspective of the clinical microbiologist.

The genus Campylobacter: a decade of progress.

Culture media for the isolation of campylobacters.

Lymphocytic choriomeningitis virus (LCMV) is a rodent-borne virus belonging to the family Arenaviridae, genus Arenavirus, which causes a wide spectrum of human disease. However, data on LCMV infection in Spain is scant. To investigate whether this virus causes infection in Spain, 400 serum samples from the general population (191 males, 209 females) and 100 from wild rodents were studied by immunofluorescence assay (IFA) using L-929 cells infected with LCMV. The study was performed in the "Community of Madrid," a region with both rural and urban areas in different ecological settings. Of the 400 human serum samples tested, antibodies against LCMV were detected in 7 (1.7%). No statistical differences in prevalence were found with respect to either age or rural or urban residence, but differences were seen with respect to sex. Nine (9%) of the rodent serum samples were positive. These results confirm the occurrence of LCMV infections in Man and rodents in Spain.

Lymphocytic choriomeningitis virus infection in a province of Spain: analysis of sera from the general population and wild rodents.

From the point of view of the human disease, dogs are the most important animal reservoir of Lyme borreliosis; therefore, they are used as ‘sentinel animals’. In order to know the epidemiological characteristics of dogs with antibodies against Borrelia burgdorferi, 146 canine sera samples collected during 1993–94 have been studied. The antibody detection was made by an indirect immunofluorescence method and confirmed by a haemagglutination test. Seventeen dogs (11.6%) were seropositive, of which seven were hunting dogs, three were shepherd dogs, five were domestic pets, one was a watchdog and one was a stray dog. Seven dogs had longhair phenotype, 2 medium length type, 4 hard-hair and the other 4 were short-haired. Twelve seropositive dogs were males and five were females. All seropositive dogs were more than 1 year old. The dogs with greater seroprevalence were those that harboured ticks more often than the rest. Spring and summer were the seasons when more ticks were observed. The seroprevalence found in dogs was similar to that previously obtained in humans in this area. This finding gave evidence to an intimate association between human and canine seroprevalence.

Epidemiological characteristics of dogs with Lyme borreliosis in the province of Soria (Spain).

To clarify the presence of lymphocytic choriomeningitis virus (LCMV) in Spain, we examined blood and tissue specimens from 866 small mammals. LCMV RNA was detected in 3 of 694 wood mice (Apodemus sylvaticus). Phylogenetic analyses suggest that the strains constitute a new evolutionary lineage. LCMV antibodies were detected in 4 of 10 rodent species tested.

Independent lineage of lymphocytic choriomeningitis virus in wood mice (Apodemus sylvaticus), Spain.

Diarrheal stools from 263 patients were inoculated on seven selective media: Butzler selective medium, Blaser medium, Skirrow blood agar, Preston campylobacter selective medium, Preston campylobacter blood-free medium, Butzler Virion medium, and modified Preston medium (with amphotericin B [2 mg/liter]) A similar number of Campylobacter jejuni strains were isolated from all the media studied; nevertheless, the presence of competing fecal flora (FF) made the detection of suspect colonies difficult Preston campylobacter blood-free medium with cefoperazone yielded the greatest number of C jejuni isolations, and contaminating FF grew in only 9% of the plates showing C jejuni growth; all the other media allowed the abundant growth of other FF, regardless of whether C jejuni was isolated from them or not

Comparative efficacy of seven selective media for isolating Campylobacter jejuni.

The performance of an ELISA for detection of total antibodies to
Bruceila
spp. was compared with that of the Rose Bengal, standard agglutination and Coombs test in the diagnosis of brucellosis. Sera tested were from 208 patients from whom
Brucella melitensis
had been isolated, 177 patients with significant results in at least two conventional tests, and 107 patients with fever from whom no
Brucella
spp. had been isolated and in whom all conventional tests were negative. ELISA was the most sensitive test (97 %), showing greater specificity (96 %) and good predictive positive and negative values (98 % and 94 % respecitvely). ELISA was the only positive test in 6 % of patients in whom brucellosis had been confirmed by culture.

Saz Jv

Papers

Lymphocytic choriomeningitis virus infection in a province of Spain: analysis of sera from the general population and wild rodents.

Epidemiological characteristics of dogs with Lyme borreliosis in the province of Soria (Spain).

Independent lineage of lymphocytic choriomeningitis virus in wood mice (Apodemus sylvaticus), Spain.

Comparative efficacy of seven selective media for isolating Campylobacter jejuni.

Enzyme-linked immunosorbent assay for diagnosis of brucellosis.