Objective—To develop partial budgets of the economic
costs of 2 test strategies for screening cattle for persistent
infection with bovine viral diarrhea virus (BVDV).
Design—Partial budget analysis.
Animals—938 calves arriving at 2 stocker operations.
Procedure—Calves were tested to determine prevalence
of persistent BVDV infection. Test strategies that
were evaluated included a single-test strategy consisting
of immunohistochemical staining of skin biopsy
specimens from all animals and a 2-test strategy consisting
of polymerase chain reaction (PCR) assaying of
pooled blood samples followed by immunohistochemical
staining of skin biopsy specimens from animals in
pools for which assay results were positive. Breakeven
costs (ie, cost of persistent BVDV infection per
animal necessary to justify whole-herd diagnostic testing)
associated with each test strategy were calculated
as a function of disease prevalence and test cost.
Results—Apparent prevalence of persistent BVDV
infection was 0.32%. Sensitivity and specificity of the
PCR assay for pooled samples were 100% and
89.7%, respectively. Regardless of the prevalence of
persistent BVDV infection, the break-even cost for the
2-test strategy was lower than the break-even cost for
the single-test strategy. However, the economic
advantage was greatest when prevalence was low.
Conclusions and Clinical Relevance—Results suggest
that using a 2-test strategy to screen cattle for persistent
BVDV infection, whereby the first test involves
PCR assaying of pooled samples and the second
involves immunohistochemical testing only of those animals
represented in pooled samples with positive assay
results, will reduce the cost of screening incoming feedlot
cattle, compared with immunohistochemical testing
of all animals. (J Am Vet Med Assoc 2005;226:249–254)
Objective—To determine the threshold for acute toxicosis of parenterally administered zinc phthalocyanine tetrasulfonate (ZnPcS4), a candidate second-generation photosensitizer, in mice and evaluate the compound's safety in a phase I clinical trial of ZnPcS4-based photodynamic therapy (PDT) in pet dogs with naturally occurring tumors.
Animals—Male Swiss-Webster mice and client-owned dogs with naturally occurring neoplasms.
Procedures—For the study of acute toxicosis, mice were given graded doses of ZnPcS4. To determine safety, a rapid-titration phase I clinical trial of ZnPcS4-based PDT in tumor-bearing dogs was conducted.
Results—In mice, administration of ≥ 100 mg of ZnPcS4/kg resulted in renal tubular necrosis 24 hours after IP injection. In tumor-bearing dogs, ZnPcS4 doses ≤ 4 mg/kg induced no signs of toxicosis and resulted in partial to complete tumor responses in 10 of 12 dogs 4 weeks after PDT. Tumor remission was observed with ZnPcS4 doses as low as 0.25 mg/kg.
Conclusions and Clinical Relevance—A conservative starting dose of ZnPcS4 was arrived at on the basis of mouse toxicosis findings. Zinc phthalocyanine tetrasulfonate–based PDT was tolerated well by all dogs and warrants further study. The identification of the maximum tolerated dose through traditional phase I clinical trials may be unnecessary for evaluating novel PDT protocols.