No abstract

SummaryTwelve nasal swabs were collected from yearling horses with respiratory distress and tested for Equid herpesvirus 1 (EHV-1) and Equid herpesvirus 4 (EHV-4) by realtime PCR targeting the glycoprotein B gene. All samples were negative for EHV-1; however 3 were positive for EHV-4. When these samples were tested for EHV-2 and EHV-5 by PCR all samples were negative for EHV-2 and 11 were positive for EHV-5. All three samples that were positive for EHV-4 were also positive for EHV-5.These three samples gave a limited CPE in ED cells reminiscent of EHV-4 CPE.EHV-4 CPE was obvious after 3 days and was characterised by syncytia. None of the samples produced cytopathic effect (CPE) on African green monkey kidney (Vero) cells or hamster kidney (BSR) cells. Four of the samples, which were positive in the EHV-5 PCR, produced CPE on rabbit kidney (RK13) cells and equine dermis (ED) cells. EHV-5 CPE on both cell lines was slow and was apparent after four 7-day passages. On RK13 cells the CPE was characteristic of equid herpesvirus with the formation of syncytia. However in ED cells, the CPE was characterised by ringshaped syncytia.For the first time a case of equine respiratory disease involving dual infection with EHV-4 and EHV-5 has been reported in Queensland. This was shown by simultaneously isolating EHV-4 and EHV-5 from clinical samples. EHV5 was recovered from all samples except one, suggesting that EHV5 was more prevalent in young horses than EHV2.

Beef and dairy cattle from four different herds in southern and central Queensland fed hydroponically-produced sprouted barley or wheat grain heavily infested with Aspergillus clavatus developed posterior ataxia with knuckling of fetlocks, muscular tremors and recumbency, but maintained appetite. A few animals variously had reduced milk production, hyperaesthesia, drooling of saliva, hypermetria of hind limbs or muscle spasms. Degeneration of large neurones was seen in the brain stem and spinal cord grey matter. The syndrome was consistent with A clavatus tremorgenic mycotoxicosis of ruminants. The cases are the earliest known to be associated with this fungus in Australia. They highlight a potential hazard of hydroponic fodder production systems, which appear to favour A clavatus growth on sprouted grain, exacerbated in some cases by equipment malfunctions that increase operating temperatures.

An Australian bovine herpesvirus 1 (BHV1) isolate with a defined (427 base pair) deletion in the protein coding region of the thymidine kinase gene was obtained by standard marker rescue procedures. After selection in the presence of the nucleotide analogue 5'-iodo-deoxy-uridine the virus was analysed by hybridisation with three differential oligonucleotide probes, restriction endonuclease profile studies and DNA sequence analysis. The virus elicited an immune response in recipient animals after either intramuscular or intravenous administration and produced no significant deleterious side-effects when administered at a dose sufficient to stimulate the host immune response. The safety and immunogenicity of the recombinant BHV1 virus 39B1 were similar to those reported for other registered BHV1 vaccines and the virus would appear to be suitable for the production of a vaccine seed lot and more exhaustive field trials as a prelude to commercial vaccine production and registration.