Vertical transmission and clinical signs in broiler breeders and broilers experiencing adenoviral gizzard erosion

Abstract

The present report documents an outbreak of adenoviral gizzard erosion in 22 broiler flocks in Germany. The clinical picture was characterized by uneven growth of affected broilers that resulted in considerably lower than average weight at slaughtering. Fowl adenovirus serotype 1 (FAdV-1) was isolated from gizzard lesions and histological examinations demonstrated FAdV-1-positive intranuclear inclusion bodies in gizzard epithelial cells of affected broilers by in-situ hybridization. Birds from all affected flocks originated from one broiler breeder farm. During production of affected birds, broiler breeders were between 27 and 32 weeks old. Enzyme-linked immunosorbent assay and specific virus neutralization assay of sera from parent birds demonstrated an acute FAdV-1 infection within the first 5 weeks of the production cycle. Clinically, broiler breeders exhibited a moderate fall in the hatchability of their chicks, while egg production remained normal. No further clinical signs could be observed. Genetically identical FAdV-1 strains were isolated from gizzards of embryos at the lowest point of hatchability and from affected broiler flocks raised on independent farms. For the first time, direct detection of viable FAdV-1 from gizzards of embryos and progenies of one FAdV-1-seropositive broiler breeder farm in the course of an outbreak of adenoviral gizzard erosion could be demonstrated, highlighting the importance of vertical transmission of this disease. Additionally, growth retardation and subsequent reduced average weight at the time of slaughter of broiler chickens underline the economic impact of adenoviral gizzard erosion for poultry production.

Chronological analysis of gross and histological lesions induced by field strains of fowl adenovirus serotypes 1, 8b and 11 in one-day-old chickens

“…During the last 15 years some FAdV-1 strains have been shown to cause gizzard erosions in broiler chickens in Japan (Abe et al, 2001;Okuda et al, 2001;Nakamura et al, 2002;Ono et al, 2003), several European countries (Manarolla et al, 2009;Marek et al, 2010;Domanska-Blicharz et al, 2011;Grafl et al, 2012;Kaján et al, 2013;Schade et al, 2013) and in Korea (Lim et al, 2012). The FAdV-1 field isolate used in this study was isolated from the bursa of a healthy broiler chicken, as in other studies in which serotype 1 isolates were obtained from healthy birds Nakamura et al, 2002).…”

Quantity of virulent fowl adenovirus serotype 1 correlates with clinical signs, macroscopical and pathohistological lesions in gizzards following experimental induction of gizzard erosion in broilers

“…The FAdV-1 strain used in the experiment was isolated from a pool of gizzards collected from an outbreak of gizzard erosion in Germany [8]. The virus was identified as a European “pathogenic” FAdV-1, by comparing nucleic acid sequences of long and short fiber genes according to a method described by Marek et al [5].…”

“…In order to demonstrate FAdV-1 DNA in paraffin-embedded tissue samples in-situ hybridization was performed according to a protocol described earlier [8], using a DNA probe based on the FAdV-1 long fiber gene.…”

Commensal or pathogen – a challenge to fulfil Koch’s Postulates

“…Since the first description by Yates and Fry (1957), vertical transmission of FAdV from breeders to progeny is of special importance for spreading FAdV and the induction of disease in progenies (Toro et al ., 2001; Grgic et al ., 2006; Grafl et al ., 2012). An impact on breeder performance with reduced egg production and hatchability was reported in cases of vertical transmission or due to infection with virulent FAdV-4 (Christensen and Saifuddin, 1989; Abe et al ., 1998; Kim et al ., 2008; Grafl et al ., 2012). Introduction of FAdVs into a flock can also occur via horizontal transmission, but very often the source of entrance could not be resolved due to the fact that no accurate samples were available.…”

“…Clinically, AGE can already be differentiated from HHS and IBH due to the somewhat lower mortality. A slightly elevated mortality with higher selection rate was reported but the disease might go unnoticed, despite the fact that 50% of the birds can have lesions at the slaughterhouse leading to a higher condemnation rate (Ono et al ., 2001, 2003; Grafl et al ., 2012). The disease has so far been reported from Europe and Asia, with the majority of reports identifying FAdV-1 as etiological agent.…”