Detection and characterization of chicken astrovirus associated with hatchery disease in commercial day-old turkeys in southwestern Nigeria

Abstract

Infectious diseases are a major obstacle to profitable poultry production in Nigeria due to the mortality and severe economic losses they cause. In particular, they are a potent threat to attainment of the food security goals of government and national self-sufficiency in food production. Thus, there is a need for continuous monitoring of the nation's poultry population for these diseases. As part of an ongoing investigation of enteric viruses associated with poor performance or hatchery diseases in commercial poultry in southwestern Nigeria, intestinal contents from 97 condemned or runted day-old commercial turkey poults were examined for turkey astroviruses, infectious bronchitis virus, chicken astrovirus (CAstV), avian nephritis virus, avian rotavirus, avian reovirus, fowl adenovirus, and chicken parvovirus by virus isolation, electron microscopy (EM), polymerase chain reaction (PCR), and reverse transcription PCR. The samples were collected from five commercial hatcheries and five farms located in southwestern Nigeria. While all samples tested negative for other viruses, CAstV was detected in the majority (83.5%) of the birds, although some pleomorphic virus-like particles with surface projections that appeared fringed or fimbriated were observed in five of the cell culture samples by EM. Phylogenetic analysis revealed these CAstV strains belonged to the Bi clade. These findings not only implicate CAstV as the major cause of hatchery condemnations in commercial turkeys in southwestern Nigeria but also highlight the need for experimental studies to further establish its role in this disease condition.

An Insight into the Molecular Characteristics and Associated Pathology of Chicken Astroviruses

“…Like other known astroviruses, CAstV infects mostly young animals of commercially reared chickens and turkeys [4,54,55]. The virus primarily infects the broiler-type of chicken, which happens to be the type of bird the virus was first isolated from in [13].…”

Development of a fast and sensitive RT-qPCR assay based on SYBR® green for diagnostic and quantification of Avian Nephritis Virus (ANV) in chickens affected with enteric disease

“…Recent literature has proposed RT-qPCR as an alternative for diagnosing astroviruses such as ANV. However, hydrolysis probes' high cost and instability hinder their application and validation [ 34 ], and the use of NGS also demands high cost and in the country its use is limited. On the other hand, conventional PCR is a good tool for the detection of ANV [ 33 ], however, it requires more laboratory work and time for the release of the results, in addition to not allowing the quantification of viral particles.…”

Pathogenesis of Chicken Astrovirus Related Illnesses

“…Chicken astrovirus infections are of clinical and economic concern due to their negative impact on production, owing to the increased severity of clinical symptoms and extra-intestinal involvement. Although other viruses have been implicated in cases of RSS, underperformance, and growth checks, recent studies have identified CAstV as the sole etiologic pathogen responsible for the condition in chickens and turkeys (10,12,20,39). Similarly, DNA and RNA extracted from birds exhibiting underperformance, growth checks, and amplified using various enteric virus-specific primers were consistently positive for CAstV but negative for other enteric viruses (9,17,40).…”

“…Similarly, a serosurvey on poultry abattoir workers has shown that the antibodies against turkey astrovirus are three times higher in the turkey processing workers when compared to the workers not in contact with turkey (19). Recently, CAstV was detected in cases of runting in day-old commercial turkey poults in southwestern Nigeria (20), and conceivably, this finding evidenced the possibility of cross-species transmission of CAstV to other avian species.…”