Shrews as reservoir hosts of Borna disease virus.
Borna disease Borna disease
a geographically restricted virus disease of horses and occasionally sheep, characterized by a uniformly fatal encephalomyelitis. Clinically it is characterized by pharyngeal paralysis, muscle tremor, lethargy and flaccid paralysis. virus (BDV BDV
border disease virus. ) is the causative agent of severe T-cell-mediated meningoencephalitis meningoencephalitis /me·nin·go·en·ceph·a·li·tis/ (me-ning?go-en-sef?ah-li´tis) inflammation of the brain and meninges.
toxoplasmic meningoencephalitis in horses, sheep, and other animal species in central Europe. Here we report the first unequivocal detection of a BDV reservoir species, the bicolored bi·col·or or bi·col·ored
Having two colors, as an animal.
Adj. 1. bicolored - having two colors; "a bicolor flower"; "a bicolored postage stamp"
bichrome, bicolor, bicolour, bicoloured, dichromatic white-toothed shrew, Crocidura leucodon, in an area in Switzerland with endemic Borna disease.
Borna disease (BD) is a severe immunopathologic disorder of the central nervous system induced by infection with Borna disease virus (BDV), the prototype of a new virus family, Bornaviridae, within the order Mononegavirales. With 1 notable exception (strain No/98 [1,2]), all BDV isolates exhibit a highly conserved genome (3). BD primarily affects horses and sheep, although many animals can be infected experimentally (4-6). BD is restricted to well-defined disease-endemic regions in central Europe (7). The precise pathogenesis and epidemiology of natural BDV infections are unknown; however, several unique epidemiologic features point towards the existence of BDV reservoir populations other than the final hosts (4,8,9).
Laboratory diagnosis of BD relies on postmortem examination postmortem examination
See autopsy. of the brain by histologic techniques, immunohistologic (IHC IHC Immunohistochemistry
IHC Intermountain Health Care
IHC Inner Hair Cells
IHC International Harvester Company
IHC Internet Healthcare Coalition
IHC Indian Head Cent
IHC Interactive Health Communication
IHC International Hurricane Center ) testing, reverse transcription-polymerase chain reaction (RT-PCR RT-PCR
reverse transcriptase-polymerase chain reaction. See PCR1. ), and recently TaqMan real-time RT-PCR (5,7). Histologically, BD manifests as mononuclear mononuclear /mono·nu·cle·ar/ (-noo´kle-er)
1. having but one nucleus.
2. a cell having a single nucleus, especially a monocyte of the blood or tissues.
adj. inflammation (meningoencephalitis), especially in the hippocampal hip·po·cam·pus
n. pl. hip·po·cam·pi
A ridge in the floor of each lateral ventricle of the brain that consists mainly of gray matter and has a central role in memory processes. area, where frequently intranuclear in·tra·nu·cle·ar
Situated or occurring within the nucleus of an atom or cell. , eosinophilic eosinophilic /eo·sin·o·phil·ic/ (-fil´ik)
1. readily stainable with eosin.
2. pertaining to eosinophils.
3. pertaining to or characterized by eosinophilia. (so-called Joest-Degen) inclusion bodies can be observed (7,10). The nucleoprotein nucleoprotein
Macromolecular complex consisting of a protein linked to a nucleic acid, either DNA or RNA. The proteins that combine with DNA are generally of characteristic types called histones and protamines. (p38/40, open reading frame [ORF] I) and the phosphoprotein phosphoprotein /phos·pho·pro·tein/ (-pro´ten) a conjugated protein in which phosphoric acid is esterified with a hydroxy amino acid.
n. (p24, ORF II) are the 2 most important BDV target proteins and genes for IHC, RT-PCR, and TaqMan real-time RT-PCR, respectively (4,5,7,8,10-12).
The objective of this study was to search for the putative natural reservoir hosts or vectors of BDV in an environment in which BD is endemic in horses and sheep. Eight moles, 3 shrews, and 87 mice of different species were trapped between 1999 and 2003 in a small village near Chur, Switzerland (Malix, located 1130 m above sea level), an area in which BD is endemic in horses and sheep. The animals were euthanized and stored at -20[degrees]C for later examination. Their brains were divided into 2 equal parts, one half was fixed in 4% formaldehyde, cut transversally into several equal parts and embedded in paraffin for microscopic evaluation; the other half was stored in tubes at -20[degrees]C. IHC was performed as described previously (5, 7,10). A recently established TaqMan real-time RT-PCR system (Applied Biosystems, Rotkreuz, Switzerland) (5) was used to detect and quantify BDV nucleic acid nucleic acid, any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis. in all brain samples and selected heart samples from the mice, shrews, and moles.
Ali samples that were positive by TaqMan real-time RT-PCR in the Zurich laboratory as well as selected negative samples were reevaluated blind in the Vienna laboratory by conventional RT-PCR, beginning with frozen parallel samples that had been stored. RT-PCR and sequencing were carried out as described by Kolodziejek et al. (3). The resulting amplicons of 1 shrew shrew, common name for the small, insectivorous mammals of the family Soricidae, related to the moles. Shrews include the smallest mammals; the smallest shrews are under 2 in. (5.1 cm) long, excluding the tail, and the largest are about 6 in. (15 cm) long. (no. 144) were sequenced by employing the ABI Abi (ā`bī) [short for Abijah], in the Bible, King Hezekiah's mother.
(Application Binary Interface) A specification for a specific hardware platform combined with the operating system. PRISM BigDye Terminator Cycle Sequencing Ready Reaction Kit (PE Applied Biosystems, Foster City, CA, USA) and an ABI Prism 310 genetic analyzer (PE Applied Biosystems).
Histologic examination showed no inflammation or degenerative processes in any of the 98 brains. Three of the 98 brains, however, were positive for BDV antigen by IHC with both monoclonal antibodies. Labeling of inclusion bodies and some intracytoplasmic intracytoplasmic /in·tra·cy·to·plas·mic/ (-si?to-plaz´mik) within the cytoplasm of a cell. staining was notable from the forebrain forebrain: see brain. (prosencephalon prosencephalon /pros·en·ceph·a·lon/ (pros?en-sef´ah-lon) forebrain.
1. the part of the brain developed from the anterior of the three primary brain vesicles, comprising the diencephalon and telencephalon.
2. ) to the mesencephalon mesencephalon /mes·en·ceph·a·lon/ (mez?-en-sef´ah-lon) midbrain.
1. the part of the brain developed from the middle of the three primary vesicles of the embryonic neural tube, comprising the tectum and the cerebral peduncles. (Figure, panel A). The 3 BDV-antigen-positive brains originated from the 3 shrews investigated, while all samples from moles and different species of mice proved negative. Identical results were obtained by TaqMan real-time RT-PCR; all 95 mouse and mole brains were negative, while the brain samples of all 3 shrews were positive (Table).
In addition to brain tissues, the hearts of the 3 BDV-positive shrews and of 2 BDV-negative mice were examined. In the heart of shrew 144, BDV-positive labeling was found in a multifocal multifocal /mul·ti·fo·cal/ (mul?te-fo´k'l) arising from or pertaining to many foci.
Relating to or arising from many foci. pattern (Figure, panel B). The myocardiocytes showed intracytoplasmic and intranuclear labeling, but no inclusion bodies could be recognized. The hearts of the other 2 shrews and the 2 mice were negative by IHC. By TaqMan real-time RT-PCR, however, the hearts of all 3 shrews proved positive (Table), while the hearts of the mice were negative. The observed differences in the results obtained by the 2 methods can be explained by the higher sensitivity of the TaqMan method compared to IHC.
When the brains of the shrews were analyzed by conventional RT-PCR, all 6 assays yielded amplicons of the expected sizes in all 3 shrews, whereas mouse samples negative by TaqMan real-time RT-PCR were also negative by conventional RT-PCR. The compiled sequences of shrew 144 resulted in a stretch of 2,041 nucleotides (nt), composing the complete N, X, and P protein-encoding regions, as well as the 5'-untranslated region of the X/P transcript of the BDV genome. The shrew-derived sequence (GenBank accession no. DQ251041) was verified as the expected BDV sequence by BLAST (available from http://www.ncbi.nlm.nih.gov/blast/) search. The sequence showed 99.9% identity to a BDV sequence derived from a horse (GenBank accession no. DQ251042), which died of BD near the location where the shrews were trapped, and to a BDV sequence from another horse from this region (GenBank accession no. AY374547), which differed by only 1 nt and 2 nt, respectively), confirming the identity of BDVs in this area.
Bicolored white-toothed shrews (Crocidura leucodon) are insectivores that are distributed from central Europe eastward to the Caspian Sea. In Switzerland, these shrews are found in the same areas where BD is endemic in horses, sheep, and other animal species. Bicolored white-toothed shrews are 93-125 mm long and weigh 7-13 g. In northern regions, they often live in gardens, outhouses OUTHOUSES. Buildings adjoining to or belonging to dwelling-houses.
2. It is not easy to say what comes within and what is excluded from the meaning of out-house. , and farm buildings, and in the Alps, they can be found [less than or equal to] 1,600 m above sea level. Shrews are carnivores, and their diet consists of insects and snails, but they may also eat forage (13). They live on the ground and do not climb, which could explain why mainly horses (during the grazing season) or animals located in old-fashioned farmhouses without feeding troughs are affected by BD. BD shows an increased incidence in spring and (early) summer, when most shrews are found in pastures and in close contact with grazing animals. In winter, some species of the genus Crocidura show social acceptance and group together, which may be a possible source of infection between shrews (13). In an experimental study by Sauder and Staeheli (14), rats persistently infected with BDV and naive rats were put together, which led to infection of the naive rats after cohabitation A living arrangement in which an unmarried couple lives together in a long-term relationship that resembles a marriage.
Couples cohabit, rather than marry, for a variety of reasons. They may want to test their compatibility before they commit to a legal union. . Most animals showed signs of disease 5-6 weeks after first contact with carrier rats, and high virus titers were found in their urine.
In the case of the shrews, no other organs, urine, or body fluids were available. Nevertheless, the experimental results in rats led to the conclusion that persistently infected rodents, in this case, shrews, most likely transmit the virus by excretions such as saliva or urine deposited on forage for horses and sheep. This suggestion is supported by the observation that the bulbus olfactorius near the ethmoid ethmoid /eth·moid/ (eth´moid)
1. sievelike; cribriform.
2. the ethmoid bone; see Table of Bones. .ethmoi´dal
eth·moid or eth·moi·dal
adj. is heavily inflamed in cases of naturally occurring BD. Levels of viral antigen or viral RNA RNA: see nucleic acid.
in full ribonucleic acid
One of the two main types of nucleic acid (the other being DNA), which functions in cellular protein synthesis in all living cells and replaces DNA as the carrier of genetic are also high in this region of the brain.
In conclusion, we postulate that shrews are reservoir hosts of BDV. Shrews also meet the criteria established for potential BDV reservoir species in a recent review article (9). Our finding, however, does not exclude the possibility that other animal species living in this environment could also harbor BDV. In further studies, we will examine more shrews and additional organs, excretions, and secretions as well as other possible reservoir and vector species.
We thank Mr and Mrs Othmar Allenspach, Malix, for their help and cooperation in trapping mice, shrews, and moles, J.P. Muller for species identification of the mice and shrews, and L. Vaughan for critical revision of the manuscript.
Dr Hilbe is veterinary pathologist at the Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich History
The University of Zurich was founded in 1833 with existing colleges of theology (founded by Huldrych Zwingli in 1525), law and medicine merged together with a new faculty of Philosophy. . Her primary research interests are Borna disease, bovine viral diarrhea, and immunohistochemical techniques for diagnostic and research purposes.
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Monika Hilbe, * Romana Herrsche, * Jolanta Kolodziejek, ([dagger]) Norbert Nowotny, ([dagger]) ([double dagger]) Kati Zlinszky, * and Felix Ehrensperger *
* University of Zurich, Zurich, Switzerland; ([dagger]) University of Veterinary Medicine, Vienna, Austria; and ([double dagger]) United Arab Emirates University United Arab Emirates University (in Arabic:جامعة الإمارات العربية المتحدة) was established in 1976, and is the oldest , Al Ain, United Arab Emirates United Arab Emirates, federation of sheikhdoms (2005 est. pop. 2,563,000), c.30,000 sq mi (77,700 sq km), SE Arabia, on the Persian Gulf and the Gulf of Oman.
Address for correspondence: Monika Hilbe, Institute of Veterinary Pathology, Winterthurerstrasse 268, CH-8057 Zurich, Switzerland; fax: 41-1-635-8934; email: firstname.lastname@example.org.
Table. Summary of immunohistologic and real-time RT-PCR findings * Real-time RT-PCR Ct values ([dagger]) p24 and p40 (mean of 2 Case no. Organ Immunohistology analyses) 134 Brain p24 positive p24: 14.93 / 17.53 p40 positive p40: 15.87 / 19.35 Heart p24 negative p24: 28.07 / 29.54 p40 negative p40: 27.94 / 30.05 137 Brain p24 positive p24: 24.00 / 25.04 p40 positive p40: 25.50 / 26.95 Heart p24 negative p24: 33.88 / 38.07 p40 negative p40: 33.84 / 35.24 144 Brain p24 positive p24: 16.27 / 17.44 p40 positive p40: 17.09 / 18.88 Heart p24 positive p24: 32.32 / 33.92 p40 positive p40: 31.68 / 35.17 Calibrated values ([double dagger]) Real-time RT-PCR (virus copies; Ct values 18S rRNA mean of 2 Case no. Organ (mean value) analyses) 134 Brain 13.34 p24: 271.9 p40: 40.87 Heart 19.64 p24: 2.866 p40: 1.749 137 Brain 24.41 p24: 13,246 p40: 2,218.8 Heart 19.66 p24: 0.0204 p40: 0.0366 144 Brain 13.98 p24: 216.04 p40: 46.289 Heart 23.83 p24: 2.8235 p40: 1.3375 * Histologic findings: no lesions on brain or heart for all 3 cases. ([dagger]) RT-PCR, reverse transcription-polymerase chain reaction; Ct, threshold cycle no. ([double dagger]) The calibrated values were calculated by using the sum of both normalized Ct-values of Borna disease virus p24 and p40, respectively, and dividing it by the normalized value of the 18s rRNA (5). Each organ was analyzed twice, and the evaluation was performed in duplicate. Please note that the viral load in each animal can be quite variable.