PMID- 26113349 OWN - NLM STAT- MEDLINE DCOM- 20160630 LR - 20150626 IS - 1751-0813 (Electronic) IS - 0005-0423 (Linking) VI - 93 IP - 7 DP - 2015 Jul TI - In vivo characterisation of two Australian isolates of Marek's disease virus including pathology, viral load and neuropathotyping based on clinical signs. PG - 240-7 LID - 10.1111/avj.12342 [doi] AB - OBJECTIVE: To evaluate the pathogenicity of Australian Marek's disease virus (MDV) isolate MPF23 (1985) against the reference strain MPF57 based on pathology, viral load and neuropathotyping on the basis of clinical signs. PROCEDURE: Two MDV challenge isolates (MPF57 or MPF23) were administered to unvaccinated specific-pathogen free (SPF) layer chicks on day 5 after hatch at three challenge doses (500, 2000 or 8000 plaque-forming units (pfu)/chick). Mortality, body weight, immune organ weights, MDV load in peripheral blood lymphocytes (PBL) and clinical signs were measured to 56 days post challenge (dpc). RESULTS: MPF23 was the more pathogenic of the two viruses, inducing higher mortality (81% vs 62%) and incidence of MD lesions (100% vs 76%). MPF23 induced earlier, more sustained and more severe neurological signs in the period 26-56 dpc. However, there were few differences during the 0-23 dpc used in the neuropathotyping classification under test. The observed pattern during this earlier period classified both viruses as neuropathotype B, consistent with a very virulent pathotype. MDV load in PBL at 7 and 44 dpc did not differ between virus isolates, but the load at 7 dpc was significantly and negatively associated with time to euthanasia or death. CONCLUSION: MPF23 appears to be as, or more, virulent than the MDV strains isolated over the subsequent two decades. The neuropathotyping system developed in the USA did not clearly differentiate between the two isolates under test; however, extension of the period of assessment of clinical signs beyond 26 dpc did reveal clear differences. CI - (c) 2015 Australian Veterinary Association. FAU - Wajid, S J AU - Wajid SJ AD - Animal Science, School of Environmental and Rural Science, University of New England, Armidale, NSW, 2351, Australia. FAU - Walkden-Brown, S W AU - Walkden-Brown SW AD - Animal Science, School of Environmental and Rural Science, University of New England, Armidale, NSW, 2351, Australia. FAU - Vanselow, B A AU - Vanselow BA AD - NSW Department of Primary Industries, Beef Industry Centre, University of New England, Armidale, NSW, Australia. FAU - Islam, A F M F AU - Islam AF AD - Animal Science, School of Environmental and Rural Science, University of New England, Armidale, NSW, 2351, Australia. FAU - Renz, K G AU - Renz KG AD - Animal Science, School of Environmental and Rural Science, University of New England, Armidale, NSW, 2351, Australia. LA - eng PT - Comparative Study PT - Journal Article PT - Research Support, Non-U.S. Gov't PL - England TA - Aust Vet J JT - Australian veterinary journal JID - 0370616 SB - IM MH - Animals MH - Australia MH - Chickens/virology MH - Disease Models, Animal MH - Kaplan-Meier Estimate MH - Mardivirus/classification/isolation & purification/*pathogenicity MH - Marek Disease/blood/mortality/pathology/*physiopathology/*virology MH - Polymerase Chain Reaction/veterinary MH - Poultry Diseases/blood/mortality/pathology/physiopathology/*virology MH - Viral Load OTO - NOTNLM OT - Marek's disease virus OT - immunosuppression OT - neuropathotyping OT - pathotyping OT - viral quantification virulence EDAT- 2015/06/27 06:00 MHDA- 2016/07/01 06:00 CRDT- 2015/06/27 06:00 PHST- 2013/05/28 00:00 [received] PHST- 2014/12/03 00:00 [revised] PHST- 2014/12/16 00:00 [accepted] PHST- 2015/06/27 06:00 [entrez] PHST- 2015/06/27 06:00 [pubmed] PHST- 2016/07/01 06:00 [medline] AID - 10.1111/avj.12342 [doi] PST - ppublish SO - Aust Vet J. 2015 Jul;93(7):240-7. doi: 10.1111/avj.12342.