Equine respiratory viruses in foals in New Zealand

AIMS: To identify the respiratory viruses that are present among foals in New Zealand and to establish the age at which foals first become infected with these viruses. METHODS: Foals were recruited to the study in October/ November 1995 at the age of 1 month (Group A) or in March/ April 1996 at the age of 4-6 months (Groups B and C). Nasal swabs and blood samples were collected at monthly intervals. Nasal swabs and peripheral blood leucocytes (PBL) harvested from heparinised blood samples were used for virus isolation; serum harvested from whole-blood samples was used for serological testing for the presence of antibodies against equine herpesvirus (EHV)-1 or -4, equine rhinitis-A virus (ERAV), equine rhinitis-B virus (ERBV), equine adenovirus 1 (EAdV-1), equine arteritis virus (EAV), reovirus 3 and parainfluenza virus type 3 (PIV3). Twelve foals were sampled until December 1996; the remaining 19 foals were lost from the study at various times prior to this date. RESULTS: The only viruses isolated were EHV 2 and EHV 5. EHV 2 was isolated from 155/157 PBL samples collected during the period of study and from 40/172 nasal swabs collected from 18 foals. All isolations from nasal swabs, except one, were made over a period of 2-4 months from January to April (Group A), March to April (Group B) or May, to July (Group C). EHV 5 was isolated from either PBL, nasal swabs, or both, from 15 foals on 32 occasions. All foals were positive for antibodies to EHV 1 or EHV 4, as tested by serum neutralisation (SN), on at least one sampling occasion and all but one were positive for EHV 1 antibodies measured by enzyme-linked immunosorbent assay (ELISA) on at least one sampling occasion. Recent EHV 1 infection was evident at least once during the period of study in 18/23 (78%) foals for which at least two samples were collected. SN antibodies to ERBV were evident in 19/23 (83%) foals on at least one sampling occasion and 15/23 foals showed evidence of seroconversion to ERBV Antibodies to ERAV were only detected in serum samples collected from foals in Group A and probably represented maternally-derived antibodies. Haemagglutination inhibition (HI) antibody titres greater than or equal to 1:10 to EAdV-1 were evident in 21/23 (91%) foals on at least one sampling occasion and 16/23 foals showed serological evidence of recent EAdV-1 infection. None of the 67 serum samples tested were positive for antibodies to EAV, reovirus 3 or PIV3. There was no clear association between infection with any of the viruses isolated or tested for and the presence of overt clinical signs of respiratory disease. CONCLUSIONS: There was serological and/or virological evidence that EHV-1, EHV-2, EHV-5, EAdV-1 and ERBV infections were present among foals in New Zealand. EHV-2 infection was first detected in foals as young as 3 months of age. The isolation of EHV-2 from nasal swabs preceded serological evidence of infection with other respiratory viruses, suggesting that EHV-2 may predispose foals to other viral infections.

Viruses associated with outbreaks of equine respiratory disease in New Zealand

AIM: To identify viruses associated with respiratory disease in young horses in New Zealand. METHODS: Nasal swabs and blood samples were collected from 45 foals or horses from five separate outbreaks of respiratory disease that occurred in New Zealand in 1996, and from 37 yearlings at the time of the annual yearling sales in January that same year. Virus isolation from nasal swabs and peripheral blood leukocytes (PBL) was undertaken and serum samples were tested for antibodies against equine herpesviruses (EHV-1, EHV-2, EHV-4 and EHV-5), equine rhinitis-A virus (ERAV), equine rhinitis-B virus (ERBV), equine adenovirus 1 (EAdV-1), equine arteritis virus (EAV), reovirus 3 and parainfluenza virus type 3 (PIV3). RESULTS: Viruses were isolated from 24/94 (26%) nasal swab samples and from 77/80 (96%) PBL samples collected from both healthy horses and horses showing clinical signs of respiratory disease. All isolates were identified as EHV-2, EHV-4, EHV-5 or untyped EHV Of the horses and foals tested, 59/82 (72%) were positive for EHV-1 and/or EHV-4 serum neutralising (SN) antibody on at least one sampling occasion, 52/82 (63%) for EHV-1-specific antibody tested by enzyme-linked immunosorbent assay (ELISA), 10/80 (13%) for ERAV SN antibody, 60/80 (75%) for ERBV SN antibody, and 42/80 (53%) for haemagglutination inhibition (HI) antibody to EAdV-1. None of the 64 serum samples tested were positive for antibodies to EAV, reovirus 3 or PIV3. Evidence of infection with all viruses tested was detected in both healthy horses and in horses showing clinical signs of respiratory disease. Recent EHV 2 infection was associated with the development of signs of respiratory disease among yearlings [relative risk (RR) = 2.67, 95% CI = 1.59-4.47, p = 0.0171]. CONCLUSIONS: Of the equine respiratory viruses detected in horses in New Zealand during this study, EHV 2 was most likely to be associated with respiratory disease. However, factors other than viral infection are probably important in the development of clinical signs of disease.

EMG activity of trunk muscles and torque output during isometric axial rotation exertion: a comparison between back pain patients and matched controls

Abnormal patterns of trunk muscle activity could affect the biomechanics of spinal movements and result in back pain. The present study aimed to examine electromyographic (EMG) activity of abdominal and back muscles as well as triaxial torque output during isometric axial rotation at different exertion levels in back pain patients and matched controls. Twelve back pain patients and 12 matched controls performed isometric right and left axial rotation at 100%, 70%, 50%, and 30% maximum voluntary contractions in a standing position. Surface EMG activity of rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum and multifidus were recorded bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were measured. Results showed that there was a trend (P = 0.08) of higher flexion coupling torque during left axial rotation exertion in back pain patients. Higher activity for external oblique and lower activity for multifidus was shown during left axial rotation exertion in back pain group when compared to the control group. In right axial rotation, back pain patients exhibited lesser activity of rectus abdominis at higher levels of exertion when compared with matched controls. These findings demonstrated that decreased activation of one muscle may be compensated by overactivity in other muscles. The reduced levels of activity of the multifidus muscle during axial rotation exertion in back pain patients may indicate that spinal stability could be compromised. Future studies should consider these alternations in recruitment patterns in terms of spinal stability and internal loading. The findings also indicate the importance of training for coordination besides the strengthening of trunk muscles during rehabilitation process. (C) 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.

EMG activity normalization for trunk muscles in subjects with and without back pain

Purpose: The aims of the present study were to examine electromyographic (EMG) activity of six bilateral trunk muscles during maximal contraction in three cardinal planes, and to determine the direction of contraction that gives maximal activation for each muscle. both for healthy subjects and back-pain patients. Methods: Twenty-eight healthy subjects and 15 back-pain patients performed maximum voluntary contractions in three cardinal planes, Surface EMG signals were recorded from rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum, and multifidus bilaterally. Root mean square values of the EMG data were calculated to quantify I the amplitude of EMG signals. Results: For both healthy subjects and back-pain patients. one single direction of contraction was found to give the maximum EMG signals for most muscles. Rectus abdominis demonstrated maximal activity in trunk flexion, external oblique in lateral flexion. internal oblique in axial rotation, and multifidus in extension. For the latissimus dorsi and iliocostalis lumborum. maximal activity was demonstrated in more than one cardinal plane. Conclusion: This study has implications for future research involving normalization of muscle activity to maximal levels required in many trunk EMG studies. As the latissimus dorsi and iliocostalis lumborum demonstrate individual differences in the plane that gives maximal activity, these muscles may require testing in more than one plane.

Polymerase chain reaction tests for the identification of Ross River, Kunjin and Murray Valley encephalitis virus infections in horses

Objective To develop and validate specific, sensitive and rapid diagnostic tests using RT-PCR for the detection of Ross River virus (RRV), Kunjin virus (KV) and Murray Valley encephalitis virus (MVEV) infections in horses. Methods Primer sets based on nucleotide sequence encoding the envelope glycoprotein E2 of RRV and on the nonstructural protein 5 (NS5) of KV and MVEV were designed and used in single round PCRs to test for the respective viruses in infected cell cultures and, in the case of RRV, in samples of horse blood and synovial fluid. Results The primer pairs designed for each of the three viruses amplified a product of expected size from prototype viruses that were grown in cell culture. The identity of each of the products was confirmed by nucleotide sequencing indicating that in the context used the RT-PCRs were specific. RRV was detected in serums from 8 horses for which there were clinical signs consistent with RRV infection such that an acute-phase serum sample was taken and submitted for RRV serology testing. The RRV RT-PCR was analytically sensitive in that it was estimated to detect as little as 50 TCID50 of RRV per mL of serum and was specific in that the primer pairs did not amplify other products from the 8 serum samples. The RRV primers also detected virus in three independent mosquito pools known to contain RRV by virus isolation in cell culture. Samples from horses suspected to be infected with KV and MVEV were not available. Conclusion Despite much anecdotal and serological evidence for infection of horses with RRV actual infection and associated clinical disease are infrequently confirmed. The availability of a specific and analytically sensitive RT-PCR for the detection of RRV provides additional opportunities to confirm the presence of this virus in clinical samples. The RTPCR primers for the diagnosis of KV and MVEV infections were shown to be specific for cell culture grown viruses but the further validation of these tests requires the availability of appropriate clinical samples from infected horses.

The Australian paralysis may be the missing link tick in the transmission of Hendra virus from bats to horses to humans

Hendra virus is a new virus of the family Paramyxoviridae. This virus was first detected in Queensland, Australia, in 1994; although, it seems that the virus has infected fruit-eating bats (flying-foxes) for a very long time. At least 2 humans and 15 horses have been killed by this virus since it first emerged as a virus that may infect mammals other than flying-foxes. Hendra virus is thought to have moved from flying-foxes to horses, and then from horses to people. There is a reasonably strong hypothesis for horse-to-human transmission: transmission of virus via nasal discharge, saliva and/or urine. In contrast, there is no strong hypothesis for flying-fox-to-human transmission. I present evidence that the Australian paralysis tick, Ixodes holocyclus, which has apparently only recently become a parasite of flying-foxes, may transmit Hendra virus and perhaps related viruses from flying-foxes to horses and other mammals. (C) 2003 Elsevier Science Ltd. All rights reserved.

Reliability of electromyographic and torque measures during isometric axial rotation exertions of the trunk

Objective: The aim of the present study was to investigate the between-days reliability of electromyographic (EMG) measurement of 6 bilateral trunk muscles and also the torque output in 3 planes during isometric right and left axial rotation at different exertion levels. Methods: Ten healthy subjects performed isometric right and left axial rotation at 100, 70, 50 and 30% maximum voluntary contractions in two testing sessions at least 7 days apart. EMG amplitude and frequency analyses of the recorded surface EMG signals were performed for rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum and multifidus bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were measured. Results: For both EMG amplitude and frequency values, good (intraclass correlation coefficient, ICC = 0.75-0.89) to excellent (ICC greater than or equal to 0.90) reliability was found in the 6 trunk muscles at different exertion levels during axial rotation. The reliability of both maximal isometric axial rotation torque and coupling torques in sagittal and coronal planes were found to be excellent (ICC greater than or equal to 0.93). Conclusions: Good to excellent reliability of EMG measures of trunk muscles and torque measurements during isometric axial rotation was demonstrated. This provides further confidence of using EMG and triaxial torque assessment as outcome measures in rehabilitation and in the evaluation of the human performance in the work place. (C) 2003 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.