Emergence of Usutu virus in Hungary.

In 2001, Usutu virus (USUV), a mosquito-borne flavivirus of the Japanese encephalitis virus serogroup related to West Nile virus and previously restricted to sub-Saharan Africa, emerged in wild and zoo birds in and around Vienna, Austria. In order to monitor the spread of the infection, a dead bird surveillance program was established in Austria and in neighboring Hungary. In Hungary, 332 dead birds belonging to 52 species were tested for USUV infection between 2003 and 2006. In the first 2 years, all birds investigated were negative. In August 2005, however, USUV was detected in organ samples of a blackbird (Turdus merula), which was found dead in Budapest, Hungary, by reverse transcription-PCR, immunohistochemistry, and in situ hybridization. In July and August 2006, a further six dead blackbirds tested positive for USUV, and the virus was isolated from organ samples of one bird. These birds were also found in urban areas of Budapest. The nearly complete genomic sequence of one Hungarian USUV strain was determined; it was found to share 99.9% identity with the strain that has been circulating in Austria since 2001. This result indicates that the USUV strain responsible for the blackbird die-off in Budapest most likely spread from Austria to Hungary instead of being independently introduced from Africa.

Experimental Usutu virus infection of suckling mice causes neuronal and glial cell apoptosis and demyelination.

Usutu virus (USUV), a mosquito-borne flavivirus of the Japanese encephalitis virus group has been responsible for avian mortality in Austria since 2001. In the present study, the neuropathogenicity and neuroinvasiveness of USUV for 1-week-old suckling mice was investigated. After intraperitoneal inoculation, clinical signs like depression, disorientation, paraplegia, paralysis and coma were observed between 6 and 11 days post infection. Histologically, there was widespread neuronal apoptosis especially in the brain stem. Inflammatory infiltrates were scarce. Apoptosis was also present in white matter of cerebellum, medulla and spinal cord, and was frequently accompanied by primary demyelination. While apoptosis of neurons was clearly associated with presence of viral signals, the cause of apoptosis of white matter cells was more ambiguous. However, focal immunostaining was found in the white matter, especially in the spinal cord. As with all flaviviruses, USUV proved to be neuropathogenic for mice. In contrast to other flaviviruses, neuroinvasion occurred only in animals that were not older than 1 week at the time of inoculation. While neuronal apoptosis is a general aspect of flavivirus pathogenicity, demyelination seems to be a unique feature of USUV infection.

Use of the meridian test for the detection of equine herpesvirus type 1 infection in horses with decreased performance.

OBJECTIVE: To evaluate use of the acupuncture meridian test for detection of recent or recently reactivated equine herpesvirus type 1 (EHV-1) infection in horses with decreased performance. DESIGN: Case-control study. ANIMALS: 40 horses. PROCEDURE: Physical and neurologic examinations were performed, and acupuncture points on the bladder meridian were tested for sensitivity reactions in case and control horses. Polymerase chain reaction assays were performed to determine whether EHV-1 or equine herpesvirus type 4 (EHV-4) DNA could be detected in peripheral blood mononuclear cells. Complement fixation (CF) tests for detection of antibodies against EHV-1 and EHV-4 and virus neutralization (VN) tests for detection of antibodies against EHV-1 were performed on paired serum samples obtained 3 weeks apart. RESULTS: There was a significant difference in skin sensitivity in the cervical, sacral, and gluteal regions and flank between case and control horses. By use of the meridian test, all case horses were sensitive to manipulation of all acupuncture points believed to be associated with EHV infections, whereas only a few control horses were sensitive at an occasional point. Equine herpesvirus type 1 or EHV-4 viremia was not detected in any horses. Mean +/- SDVN antibody titers against EHV-1 were not significantly different between the 2 groups. Mean +/- SD CF antibody titers against EHV-1 obtained 3 weeks after the initial samples were higher in case horses than control horses; however, unequivocal seroconversion was not detected. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the meridian test in case horses were associated with sensitivity reactions similar to those detected by physical and neurologic examinations; however, an unequivocal association with EHV-1 or EHV-4 infection was not detected.