Theiler's disease associated with administration of tetanus antitoxin contaminated with nonprimate (equine) hepacivirus and equine parvovirus-hepatitis virus

An 11-year-old Trakehner gelding was presented for evaluation of lethargy, decreased appetite, mild icterus, and elevated hepatic enzyme activities. Physical examination, serum chemistry results, and liver biopsy histopathologic findings were supportive of Theiler's disease. Polymerase chain reaction (PCR) testing results of serum and liver tissue were positive for nonprimate (equine) hepacivirus (NPHV) and a novel equine parvovirus-hepatitis virus (EqPV-H). PCR testing of the lot of tetanus antitoxin administered to the gelding 3 months previously also yielded positive results for NPHV and EqPV-H. Treatment included supportive care and clinical signs resolved within 1 week, although hepatic enzyme activities remained elevated for several months. The horse successfully returned to work as a hunter/jumper for about 1 year until it developed a forelimb lameness and progressive atrophy of shoulder musculature (sweeney), prompting a decision for euthanasia 20 months after initial evaluation. Serial PCR testing of serum revealed persistent infection with both NPHV and EqPV-H and necropsy examination revealed chronic active hepatitis, mild liver atrophy, and positive PCR results for NPHV and EqPV-H in liver tissue. This case highlights the possible risk of administering potentially contaminated biologics of equine origin and the importance of screening for recently identified hepatic viruses in donors from which blood products are prepared.     

Maximum likelihood and Bayesian approaches to stock assessment when data are questionable

This study examines the use of age-structured maximum likelihood and Bayesian approaches for stock assessment of the Namibian monkfish, Lophius vomerinus, resource with questionable data, in which time series are short, abundance indices are variable, and research data conflict with commercial data. Bayesian approaches with both noninformative and informative priors are investigated to determine if they enhance estimation stability. Three data scenarios are assessed: commercial and research survey data, research survey data only, and commercial data only. Both statistical approaches show that resource abundance has decreased with exploitable biomass estimated at approximately 44% of pristine levels. The maximum likelihood and the Bayesian approach with noninformative priors result in similar estimates. As the abundance data contained little information pertaining to possible density dependence within the stock–recruit relationship, only a Bayesian approach with informative priors reduces uncertainty in the steepness parameter h. Estimated management quantities are sensitive both to the set of data sources and whether prior information was informative or not. The strengths of the Bayesian approach include the integration of prior information with uncertain data, the exploration of data conflicts, and the ability to show the uncertainty in estimates of management parameters. Its weakness is that estimation stability is dependent on the choice of priors, which alters some posterior distributions of management quantities.