Tularemia outbreak, Bulgaria, 1997-2005.The 1997-2005 tularemia tularemia (tlərē`mēə) or rabbit fever, acute, infectious disease caused by Francisella tularensis (Pasteurella tularensis). outbreak in Bulgaria affected 285 people. Ten strains were isolated from humans, a tick, a hare, and water. Amplified fragment length polymorphism Amplified fragment length polymorphism PCR, or "AFLP-PCR" (often AFLP), is a tool used in the study of genetics and in the practice of genetic engineering.
Amplified Fragment Length Polymorphism (AFLP typing of the present isolates and of the strain isolated in 1962 suggests that a new genetic variant caused the outbreak.
Tularemia is a zoonotic disease caused by the gram-negative bacterium Francisella tularensis (1). During the last 10 years, several outbreaks occurred in different countries, causing tularemia to become a major problem on the Balkan Peninsula (2-5).
The first Bulgarian F. tularensis strain, isolated in 1962 from a muskrat muskrat, North American aquatic rodent. The common muskrats, species of the genus Ondatra, are sometimes called by their Native American name, musquash. (Ondatra zibethica) found in the lake of Srebarna reserve near the Danube River, was designated Srebarna19 (6). The first 4 tularemia cases in Bulgaria were reported in 1963 (6, 7) after a small epidemic involving mostly employees in the Srebarna reserve. After 35 years of tularemia surveillance with no cases reported, a focal epidemic was detected near the end of 1997 (2,8). New cases appeared, and strains were isolated and characterized. A total of 285 cases of tularemia were reported and registered at the Bulgarian Ministry of Health in the period 1997-2004 and the first quarter of 2005. The outbreak areas in 1962 and 1997-2005 in Bulgaria are shown on Figure 1. The first case of tularemia was reported in November 1997 in a patient from a small town in the Slivnitsa region. From 1998 to 2000, 171 cases were reported (8). The outbreak seemed to abate during 2001 and 2002, when only 16 cases were documented. The incidence increased again in 2003 when 76 new cases were reported. An area [approximately equal to] 4,000 [km.sup.2] near the western border with Serbia and Montenegro Serbia and Montenegro (sûr`bēə, mŏn'tənē`grō), Serbian Srbija i Crna Gora, former country of SE Europe, in the Balkan Peninsula, a short-lived union (2003–6) of the republics of Serbia and the much was the epidemic focus of the outbreak.
All the patients exhibited the typical clinical picture of oropharyngeal oropharyngeal /oro·pha·ryn·ge·al/ (-fah-rin´je-al)
1. pertaining to the mouth and pharynx.
2. pertaining to the oropharynx. , oculoglandular, or ulceroglandular tularemia. Four (1.4%) of the 285 patients had the oculoglandular form, 6 (2.1%) had the ulceroglandular form, and 275 (96.5%) had the oropharyngeal form. No deaths, complications, or relapses were observed.
Except for 1 seronegative seronegative /se·ro·neg·a·tive/ (-neg´ah-tiv) showing negative results on serological examination; showing a lack of antibody.
adj. patient, tularemia cases were diagnosed according to the confirmed case definition of the Centers for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. (9). Clinically relevant information was gathered by interviews, referral to hospitals, and questionnaires sent to general practitioners in the region and submitted to the reference centers for epidemiologic analysis. Three serum samples (acute phase, convalescent con·va·les·cent
Relating to convalescence.
A person who is recovering from an illness, an injury, or a surgical operation.
1. pertaining to or characterized by convalescence.
2. phrase, and 1 collected 3 months [+ or -] 15 days after the end of therapy) were collected from all patients (online Appendix; available from http://www.cdc.gov/ncidod/EID/vol12no04/050709_app.htm). All samples were tested with hemagglutination hemagglutination /he·mag·glu·ti·na·tion/ (he?mah-gloo-ti-na´shun) agglutination of erythrocytes.
n. and tube-agglutination assays (BulBio-NCIPD, Sofia, Bulgaria) for anti-Francisella antibodies.
Fine needle biopsy specimens from enlarged lymph nodes enlarged lymph nodes Lymphadenopathy, see there were processed from 20 patients. Half of the volume from each specimen was cultured on modified Thayer-Martin agar Thayer Martin culture medium is used for culturing Neisseria bacteria. It is a chocolate agar with antibiotics included to kill competing bacteria. Both N. gonorrhoeae and N. meningitidis grow on this medium, but when growing N. (10), and the other half was processed for polymerase chain reaction polymerase chain reaction (pŏl`ĭmərās') (PCR), laboratory process in which a particular DNA segment from a mixture of DNA chains is rapidly replicated, producing a large, readily analyzed sample of a piece of DNA; the process is (PCR PCR polymerase chain reaction.
polymerase chain reaction
Polymerase chain reaction (PCR) ). Water samples, collected from 41 wells, were also cultured through passage in guinea pigs (Appendix). Ten strains were isolated, 4 from patients, 4 from water, 1 from a hare, and 1 from a tick (Appendix). One of the human isolates (isolate Las) was from a seronegative patient. Identification of the strains was performed according to their microbiologic and antigenic properties by using standard methods (10). Direct immunofluorescence assay (IFA Immunofluorescent assay (IFA)
A blood test sometimes used to confirm ELISA results instead of using the Western blotting. In an IFA test, HIV antigen is mixed with a fluorescent compound and then with a sample of the patient's blood. ) with fluorescein fluorescein /flu·o·res·ce·in/ (fldbobr-res´en) a fluorescing dye; its sodium salt is used as a tracer in retinal angiography and as a diagnostic aid for revealing corneal trauma and fitting contact lenses. isothiocyanate-conjugated anti-Francisella serum (BulBioNCIPD) was used to detect F. tularensis antigens. DNA DNA: see nucleic acid.
or deoxyribonucleic acid
One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. from biopsy specimens and strains was subjected to PCR with tul4 and RD1 primers (11). All investigated biopsy specimens and strains were PCR and IFA positive.
16S-PCR restriction fragment length polymorphisms (RFLP RFLP
restriction fragment length polymorphism
restriction fragment length polymorphism.
RFLP ) and amplified fragment length polymorphism (AFLP) methods were used for molecular typing. For 16SPCR SPCR Spacer
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SPCR Single-Plane Collimating Range
SPCR Serial Peripheral Control Register RFLP, the genomic DNA was amplified by 16S rRNA universal primers (12). The 948-bp PCR product was digested with MboI, RsaI, and HaeIII enzymes. All strains exhibited a characteristic F. tularensis fingerprinting pattern, and no variations were found. For AFLP, DNA was digested with HindIII and MboI enzymes, adaptors were ligated, and selective PCR was carried out with Hind+0 and Mbo+C primers. Pearson correlation and unweighted pair group method with arithmetic averages (UPGMA UPGMA Unweighted Pair Group Method, Arithmetic Mean ) algorithms were applied for generating dendrogram A dendrogram is a tree diagram frequently used to illustrate the arrangement of the clusters produced by a clustering algorithm (see cluster analysis). Dendrograms are often used in computational biology to illustrate the clustering of genes. (Figure 2). Three of the water isolates showed 100% similarity, and only 1 (Aqua D) was included in the dendrogram (Figure 2). A set of DNA samples from 27 F. tularensis strains originating from Asia, Europe, America, and Bulgaria were also typed. The AFLP method clearly discriminated the representatives of different phylogenetic F. tularensis groups. Although the 27 AFLP patterns show little variability ([less than or equal to] 25%, Figure 2), distinctive clusters are seen. All of the subspecies holarctica cluster away from the subspecies tularensis. The fingerprinting pattern of a strain Srebarna19, isolated in 1962 during an outbreak near the Lake of Srebarna, shows high similarity with fingerprints of strains isolated in Europe (e.g., the 335-64, Italy 1964, Figure 2). The dendrogram clearly shows divergence between the 1962 Srebarna19 strain and the organisms associated with the current outbreak. The human, water, and animal isolates from the current outbreak have [approximately equal to] 95% similarity. The human isolates are closely related to isolates recovered from well water but are more distantly related to isolates from the hare and tick. The AFLP data of isolates from the current outbreak support the hypothesis of a new genotype emerging in Bulgaria. AFLP also shows the emerging isolates to be genetically distinct from the European, Asian, and American isolates evaluated in this study.
[FIGURE 2 OMITTED]
Several publications describe outbreaks in the Balkan Peninsula with healthcare importance (3-5). Ten F. tularensis strains were isolated in Turkey (3). However, they were not genetically characterized. No isolation was attempted during the Kosovo outbreak in 1999 (5).
The origin of the 10 strains from the current outbreak is controversial, but they are clearly distinct from the other worldwide isolates included in our study. The new outbreak may be a result of the agricultural reorganizations in Bulgaria in 1990s. These changes affected the way in which the arable soil was ploughed, leaving rodent holes intact. As a result, the populations of rodents, considered the main reservoir of the infection, increased substantially (13).
Francisella organisms can survive in water for prolonged periods, probably by interaction with protozoa (14). The isolation of bacteria from 4 private wells in the affected area points to ingestion of contaminated food or drinking water as the probable route of infection. This finding is further supported by the observation that most of the cases represent the oropharyngeal form. Rodents (or their excrement) could be the source for water contamination, but this hypothesis is not confirmable because of the lack of later rodent isolates for comparison.
The organism might have been introduced by means of rodents and hares through the border with Serbia and Montenegro. Agricultural practices are alike in the neighboring countries, and a similar boom in the rodent population might also have occurred there. Such a migration is bidirectional, but a future collaborative study with colleagues from Serbia and Macedonia, where tularemia is also problematic, is necessary to answer this question. Typing isolates originating from different Balkan countries will show the genetic relatedness and biodiversity among resident F. tularensis populations.
The cases reported in 2004 and 2005 suggest that the outbreak is still in progress. These are the first data for genetic identification and typing of isolates from the Balkan region, and they show a new genotype of E tularensis emerging as a cause of human disease in Bulgaria.
Dr Kantardjiev is professor of medicine, microbiology, and epidemiology at the National Center of Infectious and Parasitic Diseases, Sofia, Bulgaria. His research interests are in the field of clinical microbiology, high-risk infections, and management of immunocompromised immunocompromised /im·mu·no·com·pro·mised/ (-kom´pro-mizd) having the immune response attenuated by administration of immunosuppressive drugs, by irradiation, by malnutrition, or by certain disease processes (e.g., cancer). patients.
(1.) Sjostedt A. Family XVII. Francisellaceae, genus I. Francisella. In: Brenner DJ, editor. Bergey's manual of systematic bacteriology bacteriology
Study of bacteria. Modern understanding of bacterial forms dates from Ferdinand Cohn's classifications. Other researchers, such as Louis Pasteur, established the connection between bacteria and fermentation and disease. . Springer: New York; 2003. p. 111-35.
(2.) Christova I., Velinov T, Kantardjiev T, Galev A. Tularaemia Noun 1. tularaemia - a highly infectious disease of rodents (especially rabbits and squirrels) and sometimes transmitted to humans by ticks or flies or by handling infected animals
deer fly fever, rabbit fever, tularemia, yatobyo outbreak in Bulgaria. Scand J Infect Dis. 2004;36:785-9.
(3.) Helvac S, Gediko?lu S, Akalin H, Oral HB. Tularemia in Bursa, Turkey: 205 cases in ten years. Eur J Epidemiol. 2000;16:271-6.
(4.) Gurcan S, Otkun MT, Otkun M, Arikan OK, Ozer B. An outbreak of tularemia in Western Black Sea region of Turkey. Yonsei Med J. 2004;45:17-22.
(5.) Reintjes R, Dedushaj I, Gjini A, Jorgensen TR, Cotter B, Lieftucht A, et al. Tularemia outbreak investigation in Kosovo: case control and environmental studies. Emerg Infect Dis. 2002;8:69-73.
(6.) Dinev T, Zlatanov Z. Bacteriological study of a natural focus of tularemia in the Lake Reserve of Srebrna, the Silistra region, Bulgaria. J Hyg Epidemiol Microbiol Immunol. 1972;16:341-5.
(7.) Gotev N, Sumnaliev M, Zhecheva M. A case of the pulmonary form of tularemia. [Article in Bulgarian]. Suvr Med (Sofiia). 1963; 14:42-5.
(8.) Velinov T, Kantardjiev T, Kouzmanov A. An outbreak of tularemia in Bulgaria--January, 1998 2000. Problems of Infectious Diseases. 2001 ;29:13-4.
(9.) Centers for Disease Control and Prevention, Division of Public Health Surveillance and Informatics. Tularemia (Francisella tularensis). 1999 case definition. [cited 20 Feb 2000]. Available from: http://www.cdc.gov/epo/dphsi/casedef/tularemia_current.htm
(10.) Wong J, Shapiro D. Francisella. In: Murray P, editor. Manual of clinical microbiology, 7th ed. Washington: American Society for Microbiology The American Society for Microbiology (ASM) is a scientific organization, based in the United States although with over 43,000 members throughout the world. It is the largest single life science professional organization and its members include those whose interests encompass basic Press; 1999. p. 647-51.
(11.) Johansson A, Forsman M, Sjostedt A. The development of tools for diagnosis of tularemia and typing of Francisella tularensis. APMIS APMIS Acta Pathologica, Microbiologica et Immunologica Scandinavica
APMIS Automated Project Management Information System
APMIS Automated Project Management System . 2004;112:898-907.
(12.) Forsman M, Nyren A, Sjostedt A, Sjokvist L, Sandstrom G. Identification of Francisella tularensis in natural water samples by PCR. FEMS Microbiol Ecol. 1995;16:83-92.
(13.) Christova I, Gladnishka T. Prevalence of infection with Francisella tularensis, Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum in rodents from an endemic focus of tularemia in Bulgaria. Ann Agric Environ Med. 2005;12:149-52.
(14.) Kantardjicv T, Velinov T. Interaction between protozoa and microorganisms of the genus Francisella. Problems of Infectious Diseases. 1995;22:34-5.
Todor Kantardjiev, * Ivan Ivanov, * Tzvetan Velinov, * Plamen Padeshki, * Boris Popov, * Roumiana Nenova, * and Milcho Mincheff ([dagger])
* National Center for Infectious and Parasitic Diseases, Sofia, Bulgaria; and ([dagger]) The George Washington University George Washington University, at Washington, D.C.; coeducational; chartered 1821 as Columbian College (one of the first nonsectarian colleges), opened 1822, became a university in 1873, renamed 1904. Medical Center, Washington, DC, USA
Address for correspondence: Todor Kantardjiev, National Center for Infectious and Parasitic Diseases, Microbiology Department, 26 Yanko Sakazov, 1504 Sofia, Bulgaria; fax: 359-2-846-5520; email: email@example.com