Infection with IBV DMV/1639 at a Young Age Leads to Increased Incidence of Cystic Oviduct Formation Associated with False Layer Syndrome.

Infectious bronchitis virus (IBV) is an avian coronavirus that causes respiratory disease but can affect the reproductive tract of laying-type chickens. If infection occurs in pullets, false layer syndrome, which is characterized by the development of large, fluid-filled cystic oviducts, can occur. Recently, IBV strain DMV/1639 has been detected in parts of Canada and the U.S., where false layer syndrome has occurred, though it is not clear if IBV is the sole cause or if age at infection is an influencing variable. Our study investigates the role and timing of IBV infection on the development of false layer syndrome, using the IBV types DMV/1639 and Massachusetts (Mass). Six groups of 120 SPF chickens were challenged at either three, seven, or fourteen days of age, using either DMV/1639 or Mass IBV. Cystic oviducts were seen in all the challenged groups, and the pullets challenged at 14 days of age had fewer cystic oviducts than pullets challenged at 3 or 7 days of age. The highest percentage of severe histology lesion scores were seen in the 3-day challenge groups. The data collected in this experiment confirm that IBV DMV/1639 causes cystic oviducts and indicate that age at infection plays a role in the pathogenesis of false layer syndrome.

Pathogenicity comparison between QX-type and Mass-type infectious bronchitis virus to different segments of the oviducts in laying phase.

BACKGROUND: The QX-type infectious bronchitis virus (IBV) has become the predominant genotype worldwide in recent years and has caused serious economic losses to the chicken industry. The most significant feature of QX IBV is that its infection in the early growing stage can cause abnormal oviduct development, resulting in a high proportion of 'false layers' in poultry flocks of laying hens and breeders. However, few studies have evaluated whether infections of QX-type IBV in laying stages can also cause severe pathological changes in the oviduct. METHODS: In this study, 300-day-old specific-pathogen-free chickens were infected either with the QX-type strain QXL or Massachusetts (Mass)-type strain M41 to compare their pathogenicity on different segments of the oviduct. RESULTS: Both the QXL and M41 strains successfully replicated in all segments of the oviduct; however, the QXL strain was more highly distributed in mucosal layer and caused severe lesions in the lamina propria, including interstitial dilation, inflammatory cell infiltration, and distinct expansion of tubular glands. Moreover, the QXL strain induced high expression of proinflammatory cytokines and cytotoxic molecules in the majority of segments in the oviduct. Further research found that the QXL strain may affected the formation of shell membranes and eggshells by inhibiting the expression of type I collagen and CaBP-D28k. CONCLUSIONS: Our results indicate that the QX-type IBV is more pathogenic than Mass-type IBV to oviduct in laying phase. Collectively, these findings provide detailed information on the pathological changes in different segments of the oviduct in laying phase, which could offer a better understanding about the pathogenicity of IBV.

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

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.

Precisión diagnóstica de la ultrasonografía para detectar gallinas falsas ponedoras en una parvada comercial infectada por un virus de la bronquitis infecciosa genotipo Delmarva que causa oviductos quísticos. La infección del oviducto por el virus de bronquitis infecciosa (IBV) en gallinas de postura se ha asociado con el síndrome de la falsa ponedora. Debido a que el procedimiento de diagnóstico para la detección de oviductos quísticos mediante exámenes post mortem en parvadas de pollitas de reemplazo positivas para bronquitis infecciosa podría involucrar el sacrificio innecesario de numerosas pollitas sanas sin anomalías del tracto reproductivo, por lo tanto es deseable el desarrollo de un procedimiento de diagnóstico no invasivo y no letal. El primer objetivo del estudio fue evaluar la precisión diagnóstica de un método de ultrasonografía transcutánea para predecir la presencia de oviductos quísticos en comparación con los exámenes post mortem en un lote comercial de pollitas que resultó positivo para una variante del genotipo Delmarva (DMV) del virus de la bronquitos infecciosa. El segundo objetivo fue evaluar el desempeño del mismo método de ultrasonografía para detectar posteriormente gallinas falsas en la misma parvada en las gallinas sexualmente maduras mediante la identificación de la presencia de un huevo en el oviducto debido a la presencia de oviductos atrésicos indetectables por ultrasonografía y la ausencia de oviductos quísticos a esa edad. En las pollitas de reemplazo, la sensibilidad (Se) y la especificidad (Sp) de la ultrasonografía (prueba de índice) en comparación con el examen post mortem (prueba estándar de referencia) fueron de 73% y 91%, respectivamente. El valor predictivo positivo (VPP) y el valor predictivo negativo (VPN) fueron 67% y 93%. La técnica de ultrasonografía mostró una razón de probabilidad positiva (LR+) de 7.82 y una razón de probabilidad negativa (LR­) de 0.30. En las gallinas sexualmente maduras, la Se, Sp, PPV y NPV de la ultrasonografía en comparación con el estado de postura fueron del 98%. El LR + fue 49.00 y el LR­fue 0.02 en comparación con el estado de la postura. En conclusión, la ultrasonografía podría reemplazar los exámenes post mortem para detectar oviductos quísticos en parvadas comerciales de pollitas de reemplazo previamente infectadas con una variante DMV-1639 del virus de la bronquitis infecciosa. Aunque la precisión de la prueba de la ecografía fue excelente para las gallinas en el pico de producción para identificar gallinas ponedoras y no ponedoras en función de la presencia de un huevo en el tracto reproductivo, su funcionalidad fue limitada debido a que los oviductos atrésicos no fueron detectables.