Characterisation of the cerebrospinal fluid of horses with West Nile virus neuroinvasive disease.

West Nile virus (WNV) is a zoonotic arbovirus transmitted by mosquitoes between wild birds (natural hosts) and other vertebrates. Horses and humans are incidental, dead-end hosts, but can develop severe neurological disorders. Owing to the close contact of cerebrospinal fluid (CSF) with the extracellular fluid of the brain, the analysis of CSF composition can reflect central nervous system (CNS) impairments enabling the diagnosis and understanding of various neurodegenerative CNS disorders. Our objective was to compare the findings from the CSF samples of horses with neuroinvasive WNV infection with those of healthy controls. We compared findings from fifteen CSF samples of 13 horses with acute WNV encephalomyelitis with those of 20 healthy controls. Protein, particular enzymes and ions, glucose and lactate showed abnormal levels in a significant number of WNV cases. None of the six horses with elevated glucose concentrations survived. Rather neutrophilic than mononuclear pleocytosis was identified with WNV infection. Neutrophils probably play a role in the development of inflammatory response and brain damage. Although elevated glucose levels reliably predicted the outcome, they might be the consequence of increased plasma levels and reflect general stress rather than CNS pathophysiology. The CSF findings of WNV encephalomyelitis patients are non-specific and variable but facilitate the differential diagnosis.

Serum neutralising antibody titres against a lineage 2 neuroinvasive West Nile Virus strain in response to vaccination with an inactivated lineage 1 vaccine in a European endemic area.

In the last decade in Hungary and the neighbouring countries, West Nile Neuroinvasive Disease (WNND) has been caused in dramatically increasing numbers by lineage 2 West Nile Virus (WNV) strains both in horses and in humans. The disease in this geographical region is seasonal, so vaccination of horses should be carefully scheduled to maintain the highest antibody titres during outbreak periods. The objective of this study was to characterise the serum neutralising (SN) antibody titres against a lineage 2 WNV strain in response to vaccination with an inactivated lineage 1 vaccine (Equip® WNV). Thirty-two seronegative horses were enrolled in the study, 22 horses were allocated to the vaccinated group and 10 retained as unvaccinated controls. Horses were vaccinated according to the product's vaccination guidelines. A primary vaccination of two doses administered 28 days apart was initiated approximately 5 months before the WNV outbreak season, followed by a booster vaccination one year later. Blood samples were collected during a 2-year period to monitor production of SN antibodies against lineage 1 and the enzootic lineage 2 WNV strain. Mean antibody titres against lineage 1 WNV were significantly higher (P ≤ 0.05) in the vaccinated group compared to the control group at all-time points after the primary dose of vaccination. Similarly, mean antibody titres against lineage 2 WNV were significantly higher (P ≤ 0.05) in the vaccinated group compared to the control group at all time-points except at 6 months after the primary vaccination. SN antibody titres were significantly higher against lineage 1 than lineage 2 at all-time points. According to the results, vaccination with an inactivated lineage 1 vaccine induces antibodies against both WNV lineages 1 and 2 strains up to 2 years after booster vaccination, but in those geographical regions where lineage 2 strains are responsible for seasonal outbreaks, a booster vaccination should be considered earlier than 12 months after primary vaccination.

Comparison of assays for the detection of West Nile virus antibodies in equine serum after natural infection or vaccination.

West Nile virus (WNV) mainly infects birds, horses and humans. Outcomes of the infection range from mild uncharacteristic signs to fatal neurologic disease. The main objectives of the present study were to measure serum IgG and IgM antibodies in naturally exposed and vaccinated horses and to compare results of haemagglutination inhibition test (HIT), enzyme-linked immunosorbent assay (ELISA) and plaque reduction neutralisation test (PRNT). Altogether 224 animals were tested by HIT for WNV antibodies and 41 horses were simultaneously examined by ELISA and PRNT. After primary screening for WNV antibodies, horses were vaccinated. Samples were taken immediately before and 3-5 weeks after each vaccination. McNemar's chi-squared and percent agreement tests were used to detect concordance between HIT, ELISA and PRNT. Analyses by HIT confirmed the presence of WNV antibodies in 27/105 (26%) naturally exposed horses. Sera from 57/66 (86%) vaccinated animals were positive before the first booster and from 11/11 (100%) before the second booster. HIT was less sensitive for detecting IgG antibodies. We could detect postvaccination IgM in 13 cases with IgM antibody capture ELISA (MAC-ELISA) and in 7 cases with HIT. WNV is endemic in Hungary and regularly causes natural infections. Protective antibodies could not be measured in some of the cases 12 months after primary vaccinations; protection is more reliable after the first yearly booster. Based on our findings it was not possible to differentiate infected from recently vaccinated horses using MAC-ELISA. HIT cannot be used as a substitute for ELISA or PRNT when detecting IgG, but it proved to be a useful tool in this study to gain statistical information about the tendencies within a fixed population of horses.

Equine multinodular pulmonary fibrosis (EMPF): Five case reports.

Equine multinodular pulmonary fibrosis (EMPF), a progressive fibrosing interstitial lung disease has been associated with gammaherpesviruses. This case series describes five horses with EMPF. Three of the horses (two in Hungary, one in the Czech Republic) were diagnosed with EMPF ante mortem. They presented with typical clinical signs of EMPF including dyspnoea and weight loss. Arterial blood gas analysis revealed hypoxaemia. Blood work showed signs of inflammation like neutrophilia and hyperfibrinogenaemia. An endoscopic examination of the respiratory tract including cytology and culture of tracheobronchial secretion and bronchoalveolar lavage were performed, revealing secondary bacterial infection in one case. A suspected diagnosis of EMPF was made on the basis of a positive EHV-5 PCR from bronchoalveolar lavage and the findings of thoracic radiographs and ultrasound examination. In one case the diagnosis was confirmed by lung biopsy. All horses died or had to be euthanised despite treatment. Two horses (from Austria) were diagnosed with EMPF post mortem. They not only had EMPF but also concurrent other diseases which seemed to be associated with immunosuppression. Three horses showed the discrete form and two horses the diffuse form of EMPF. EHV-5 DNA was identified in lung tissue of all horses by PCR.