Effect of coronavirus infection on reproductive performance of turkey hens.

Turkey coronavirus (TCoV) infection causes enteritis in turkeys of varying ages with high mortality in young birds. In older birds, field evidence indicates the possible involvement of TCoV in egg-production drops in turkey hens. However, no experimental studies have been conducted to demonstrate TCoV pathogenesis in turkey hens and its effect on reproductive performance. In the present study, we assessed the possible effect of TCoV on the reproductive performance of experimentally infected turkey hens. In two separate trials, 29- to 30-wk-old turkey hens in peak egg production were either mock-infected or inoculated orally with TCoV (Indiana strain). Cloacal swabs and intestinal and reproductive tissues were collected and standard reverse-transcription PCR was conducted to detect TCoV RNA. In the cloacal swabs, TCoV was detected consistently at 3, 5, 7, and 12 days postinoculation (DPI) with higher rates of detection after 5 DPI (> 90%). All intestinal samples were also positive for TCoV at 7 DPI, and microscopic lesions consisting of severe enteritis with villous atrophy were observed in the duodenum and jejunum of TCoV-infected hens. In one of the trials TCoV was detected from the oviduct of two birds at 7 DPI; however, no or mild microscopic lesions were present. In both experimental trials an average of 28%-29% drop in egg production was observed in TCoV-infected turkey hens between 4 and 7 DPI. In a separate trial we also confirmed that TCoV can efficiently transmit from infected to contact control hens. Our results show that TCoV infection can affect the reproductive performance in turkey hens, causing a transient drop in egg production. This drop in egg production most likely occurred as consequence of the severe enteritis produced by the TCoV. However, the potential replication of TCoV in the oviduct and its effect on pathogenesis should be considered and further investigated.

Mechanical transmission of turkey coronavirus by domestic houseflies (Musca domestica Linnaeaus).

Domestic houseflies (Musca domestica Linnaeaus) were examined for their ability to harbor and transmit turkey coronavirus (TCV). Laboratory-reared flies were experimentally exposed to TCV by allowing flies to imbibe an inoculum comprised of turkey embryo-propagated virus (NC95 strain). TCV was detected in dissected crops from exposed flies for up to 9 hr postexposure; no virus was detected in crops of sham-exposed flies. TCV was not detected in dissected intestinal tissues collected from exposed or sham-exposed flies at any time postexposure. The potential of the housefly to directly transmit TCV to live turkey poults was examined by placing 7-day-old turkey poults in contact with TCV-exposed houseflies 3 hr after flies consumed TCV inoculum. TCV infection was detected in turkeys placed in contact with TCV-exposed flies at densities as low as one fly/bird (TCV antigens detected at 3 days post fly contact in tissues of 3/12 turkeys); however, increased rates of infection were observed with higher fly densities (TCV antigens detected in 9/12 turkeys after contact with 10 flies/bird). This study demonstrates the potential of the housefly to serve as a mechanical vector of TCV.

Identifying agent(s) associated with poult enteritis mortality syndrome: importance of the thymus.

Poult enteritis mortality syndrome (PEMS), a highly infectious disease of young turkeys, causes serious financial losses to the turkey industry. Clinically, PEMS is defined by mortality profiles, diarrhea, growth depression, and immunosuppression. Although many viruses, bacteria, and parasites are found in PEMS-infected birds, the inciting agent remains unknown. Experimentally, PEMS can be reproduced by exposing naïve poults to the intestinal contents from infected birds. Previous reports suggest that extraintestinal tissues fail to reproduce the disease. Histopathologic examination of tissues from PEMS-infected poults suggested that the thymus exhibited the earliest signs of pathology. On the basis of these observations, we hypothesized that the thymus harbors an agent(s) involved in PEMS. In these studies, naïve turkey poults were orally inoculated with a bacteria-free filtrate composed of either the intestines and feces or the thymus from PEMS-infected birds and were monitored for clinical signs of PEMS. Poults exposed to a filtrate composed solely of the thymus from PEMS-infected birds exhibited diarrhea, growth depression, mortality, pathology, and, most importantly, immunosuppression similar to poults exposed to the intestinal filtrate. The results of this study suggest that the thymus of infected birds harbors the agent(s) that can reproduce a PEMS-like disease in turkey poults.

Lack of evidence of avian adenovirus infection among turkey workers.

Zoonotic infections constitute a major public health concern. Outbreaks of the SARS (severe acute respiratory syndrome) and avian influenza viruses are but recent examples. Although there are many animal-specific adenoviruses and occasionally they have been noted to infect man, rarely have they been studied as potential zoonotic pathogens. In this study, the authors hypothesized that the hemorrhagic enteritis virus (HEV), an avian adenovirus that causes illness among turkeys, might infect humans. Using an enzyme immunosorbent assay, the authors compared sera from 95 turkey-exposed individuals with sera from 82 nonexposed controls for serologic evidence of infection with HEV. Multivariate modeling revealed no statistical difference in elevated antibody titers against HEV between the two groups. These data do not support the hypothesis that avian adenoviruses cross the species barrier to infect humans.