Page 310 - Avian Virology: Current Research and Future Trends

Avian Adenovirus | 301

et al., 2012; Totsuka et al., 2015; Matczuk et al., 2017). Interest- necrotizing hepatitis is seen and inclusion bodies in the hepato-
ingly, AGE is generally reported from Europe and Asia. cytes are the hallmark of the disease (Grimes et al., 1977; Itakura
The characteristic clinical signs of EDS include the production et al., 1977; Shivaprasad et al., 2001) (Fig. 10.9). These inclu-
of thin-shelled, soft-shelled and/or shell-less eggs (McFerran et sion bodies can be eosinophilic or basophilic and usually they
al., 1978; Yamaguchi et al., 1981; Smyth, 2013). During a typical are large and round; virus particles can only be recovered from
4–10-week outbreak the egg production drops about 40%, but the basophilic inclusions (Itakura et al., 1974, 1977; Ojkic et al.,
later returns to normal. Some researchers observed changes in the 2008a). Other lesions such as atrophy of the bursa of Fabricius
quality of the albumen which depends on the age of the birds at and thymus, aplastic bone marrow and lymphoid depletion in the
the time of infection (van Eck et al., 1976; Cook and Darbyshire, spleen have also been reported (Macpherson et al., 1974; Steer et
1981). There are dissimilar results of the outcomes of experimen- al., 2015; Matos et al., 2016a). A study by Steer et al. (2015) sug-
tal infections of chickens with the duck origin EDSV (Villegas et gests a correlation between the severity of the clinical signs and
al., 1979; Brugh et al., 1984; Bartha and Mészáros, 1985). The the extent of lesions in the affected organs. Gross and histopatho-
results of a recent study suggest that EDSVs of duck origins have logical lesions of HPS are similar to IBH with a pathognomonic
varying pathogenicities that may be attributed to key amino acids feature of hydropericardium, accumulation of fluid in the peri-
(Kang et al., 2017). cardial sac (Khawaja et al., 1988; Toro et al., 1999; Dahiya et al.,
Clinical signs of HEV infection are generally seen in turkeys 2002; Kim et al., 2008; Zhao et al., 2015). The macroscopic giz-
of 6–11 weeks of age after a short incubation period and pro- zard lesions are described as areas of erosions of keratinoid layer
gress rapidly (Pierson and Fitzgerald, 2013). The clinical signs with inflammation and erosion of the underlying mucosa (Abe et
are depression, bloody droppings and blood around the vent, al., 2001; Ono et al., 2004; Gjevre et al., 2013; Schade et al., 2013;
and in about 10–15% mortality in natural cases, while mortality Matczuk et al., 2017).
could be a lot higher, up to 80% in experimentally infected birds The gross lesions in naturally occurring EDS outbreaks are
(Domermuth and Gross, 1984). The acute phase of the disease is atrophied oviducts and inactive ovaries. Mild splenomegaly and
followed by immunosuppression leading to secondary infections eggs of various stages in the abdominal cavity can also be present.
(Giovanardi et al., 2014). In experimentally infected chickens oedema of the uterine folds
and exudate in the pouch shell gland are observed (Smyth, 2013).
Pathology The microscopic lesions are elegantly described by Smyth in the
At necropsy the characteristic appearance of the liver, swollen, fri- appropriate chapter of Diseases of Poultry (2013).
able and pale yellow-white with haemorrhages is suggestive of IBH In birds that died due to HEV infection, macroscopic disten-
(Fig. 10.8) (Winterfield et al., 1973; Philippe et al., 2005; Hess, sion of the small intestine is seen, and the intestinal content is
2013; Schachner et al., 2018). Haemorrhages can also be seen mixed with blood. The intestinal mucosa could be congested. The
on the abdominal walls and muscles and on the swollen kidneys enlarged spleens are friable and mottled. Petechial haemorrhages
(Howell et al., 1970). Congestion of the ventriculus and spleen in different tissues have been described. The liver is enlarged, and
could be present (Saifuddin and Wilks, 1991). Histologically, the lungs are occasionally congested (Carlson et al., 1974; Saif,

Figure 10.8 Liver from chicken with inclusion body hepatitis (IBH). Courtesy of Dr Marina Brash, Animal Health Laboratory, University of
Guelph. Figure 8. Liver from chicken with inclusion body hepatitis (IBH)
Courtesy of Dr. Marina Brash, Animal Health Laboratory, University of Guelph.