Abstract
Enteric viruses are known to have significant economic impact on poultry, especially broiler chicken flocks, because of production losses attributable to poor feed conversion and weight gain. To sustain the Nigerian poultry industry that contributes significantly to the livestock sector of the economy, there is a need to investigate commercial broiler flocks in the country for the presence of enteric viruses causing runting and stunting, growth retardation, and hatchery diseases. Gut contents were collected from 158 day-old and six 14-week old runted/stunted broiler chickens in commercial farms (ten) and hatcheries (six) located in Southwest Nigeria. The samples were examined for the presence of chicken astrovirus (CAstV), avian nephritis virus (ANV), avian rotavirus (AvRV), chicken parvovirus (ChPV), and turkey astroviruses (TAstV-1 and−2) by polymerase chain reaction (PCR) and reverse transcriptase-PCR (RT-PCR) whereas avian reovirus (ARV) and fowl adenovirus (FAdV) by virus isolation (VI), RT-PCR, and PCR. While CAstV was detected in all the birds (100%), sporadic detection of ANV (5%), and ChPV (5%) was observed in day-old and/or older birds. Four isolates were obtained by VI with one isolate being ARV positive and other three FAdV positive by RT-PCR and PCR, respectively. These findings strongly suggest CAstV as a major cause of runting and stunting as well as hatchery condemnations in commercial broilers in Southwest Nigeria, although co-infections with ANV, FAdV, ARV, and ChPV cannot be ruled out. In addition, the possible vertical and horizontal transmissions of these viruses are discussed.
Highlights
Poultry have gradually assumed a very important role in the economy of many industrialized and developing countries as they are a major source of animal protein worldwide
Pool VF18-p17 was positive for chicken astrovirus (CAstV) and avian nephritis virus (ANV) (RNA log10 value of 2.8); VF18-p19 was positive for CAstV and chicken parvovirus (ChPV) (DNA log10 value of 2.59); pool VF18-p18 was positive for CAstV, ANV (RNA log10 value of 4.88), and ChPV (DNA log10 value of 3.23)
Earlier studies in Nigeria reported the detection of CAstV and ANV genome, and CAstV antibodies in indigenous chickens [28, 29]
Summary
Poultry have gradually assumed a very important role in the economy of many industrialized and developing countries as they are a major source of animal protein worldwide. Enteric viruses cause severe disease conditions such as runting-stunting syndrome (RSS) and White Chick Syndrome (WCS) considered as sources of huge economic losses in poultry production due to culls of stunted, undersized birds that fail to thrive or are too small to pass through the processing plant, increased susceptibility to other diseases, decreased feed conversion efficiency, and prolonged time to market of affected birds [1, 5, 6]. Reports have shown severe economic impacts of these diseases with financial losses to affected hatching egg producers and hatcheries estimated at 105,000 US dollars or 68,000 US dollars per 10,000 hens, respectively [2] These enteric viruses of which several RNA and DNA viruses have been implicated, pre-dominantly affect young birds they may occur in all age groups of poultry. Chickens without symptoms of enteric disease have tested positive for these viruses [9, 10], indicating that they could serve as asymptomatic carriers or reservoirs shedding the virus via the enteric route and representing a potential source of infection to clean birds
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