Diagnostic Accuracy of Ultrasonography to Detect False Layers in a Commercial Laying Flock Infected by an Infectious Bronchitis Virus Delmarva Genotype Causing Cystic Oviducts

摘要

Infection of the oviduct by an infectious bronchitis virus (IBV) in laying hens has been associated with the false layer syndrome. Because the diagnostic procedure for the detection of cystic oviducts by postmortem examinations in IBV-positive replacement pullet flocks could involve the unnecessary sacrifice of numerous healthy pullets without reproductive tract anomalies, the development of a noninvasive and nonlethal diagnostic procedure would be desirable. The first objective of the study was to evaluate the diagnostic accuracy of a transcutaneous ultrasonography method to predict the presence of cystic oviducts compared to postmortem examinations in a commercial pullet flock positive for an IBV genotype Delmarva (DMV) variant. The second objective was to evaluate the performance of the same ultrasonography method to later detect false layers in the same flock in sexually mature hens by identifying the presence of an egg in the oviduct due to the presence of atretic oviducts undetectable by ultrasonography and the absence of cystic oviducts at that age. In replacement pullets, the sensitivity (Se) and specificity (Sp) of the ultrasonography (index test) compared to the postmortem examination (reference standard test) were 73% and 91%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 67% and 93%. The ultrasonography technique showed a positive likelihood ratio (LR+) of 7.82 and a negative likelihood ratio (LR-) of 0.30. In sexually mature hens, the Se, Sp, PPV, and NPV of the ultrasonography compared to the laying status were 98%. The LR+ was 49.00 and the LR- was 0.02 when compared to the laying status. In conclusion, the ultrasonography could replace postmortem examinations to detect cystic oviducts in commercial flocks of replacement pullets previously infected with an IBV-DMV 1639 variant. Although the test accuracy of ultrasonography was excellent for the hens at production peak to identify laying and nonlaying hens based on the presence of an egg in the reproductive tract, its practicality was limited due to atretic oviducts being not detectable.