Article

Reproducibility of swollen sinuses in broilers by experimental infection with avian metapneumovirus subtypes A and B of turkey origin and their comparative pathogenesis

Clinic for Poultry, University of Veterinary Medicine, Hannover, Germany.
Avian Pathology (Impact Factor: 1.64). 03/2008; 37(1):65-74. DOI: 10.1080/03079450701802222
Source: PubMed

ABSTRACT

Swollen head syndrome (SHS) associated with avian metapneumovirus (aMPV) subtype A or subtype B in broilers and broiler breeders has been reported worldwide. Data about pathogenesis of aMPV subtypes A and B in broilers are scarce. It has been difficult to reproduce swollen sinuses in chickens with aMPV under experimental conditions. In the field, SHS in broilers is suspected to be induced by combined infections with different respiratory pathogens. The objectives of the present study were to compare the pathogenesis of subtypes A and B aMPV in commercial broilers and to investigate the reproducibility of clinical disease. In two repeat experiments, commercial broilers free of aMPV maternal antibodies were inoculated with aMPV subtypes A and B of turkey origin. The clinical signs such as depression, coughing, nasal exudates, and frothy eyes appeared at 4 days post inoculation, followed by swelling of periorbital sinuses at 5 days post inoculation. Higher numbers of broilers showed clinical signs in subtype-B-inoculated compared with subtype-A-inoculated groups. Seroconversion to aMPV was detectable from 10 to 11 days post inoculation. The appearance of serum aMPV enzyme-linked immunosorbent assay antibodies and the clearance of the aMPV genome coincided. Subtype B aMPV showed a broader tissue distribution and longer persistence than subtype A. Histopathological changes were observed in the respiratory tract tissues of aMPV-inoculated broilers, and also in paraocular glands, such as the Harderian and lachrymal glands. Overall, our study shows that representative strains of both aMPV turkey isolates induced lesions in the respiratory tract, accompanied by swelling of infraorbital sinuses, indicating the role of aMPV as a primary pathogen for broilers.

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    • "IBV M41 and E. coli were isolated from a broiler flock in the USA that experienced SHS (Droual and Woolcock, 1994). aMPV (Picault et al., 1987;Aung et al., 2008), FAdV (Droual and Woolcock, 1994;Georgiades et al., 2001) and secondary infection (such as E. coli) have been implicated as the cause of SHS in chickens (Nakamura et al., 1997;Nakamura et al., 1998). In the IS/885-infected SPF chicks, necropsy examination at 28 dpi revealed dilation of the oviduct with fluid content (cystic oviduct) in two female chicks. "
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    ABSTRACT: Groups of one-day-old broiler chicks were vaccinated via oculo-nasal route with different live infectious bronchitis virus (IBV) vaccines; Massachusetts (Mass), 793B, D274, or Arkansas (Ark). Clinical signs and gross lesions were evaluated. Five chicks from each group were humanely killed at intervals and their trachea collected for ciliary activity assessment and for the detection of CD4+, CD8+ and IgA-bearing B cells by immunohistochemistry (IHC). Blood samples were collected at intervals for the detection of anti-IBV antibodies. At 21 days post vaccination (dpv), protection conferred by different vaccination regimes against virulent M41, QX and 793B was assessed. All vaccination programmes were able to induce high levels of CD4+, CD8+ and IgA-bearing B cells in the trachea. Significantly higher levels of CD4+ and CD8+ expression were observed in the Mass2+793B2-vaccinated group compared to the other groups. Protection studies showed that the group of chicks vaccinated with Mass2 +793B2 produced 92% ciliary protection against QX challenge; compared to 53%, 68% and 73% ciliary protection against the same challenge virus by Mass1+D274, Mass1+793B1 and Mass3+Ark respectively. All vaccination programmes produced more than 85% ciliary protection against M41 and 793B challenges. It appears that the variable levels of protection provided by different heterologous live IBV vaccinations are dependent on the levels of local tracheal immunity induced by the respective vaccine combination. The Mass2+793B2 group showed the worst clinical signs, higher mortality, and severe lesions following vaccination, but had the highest tracheal immune responses and demonstrated the best protection against all three challenge viruses.
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    • "IBV M41 and E. coli were isolated from a broiler flock in the USA that experienced SHS (Droual and Woolcock, 1994). aMPV (Picault et al., 1987;Aung et al., 2008), FAdV (Droual and Woolcock, 1994;Georgiades et al., 2001) and secondary infection (such as E. coli) have been implicated as the cause of SHS in chickens (Nakamura et al., 1997;Nakamura et al., 1998). In the IS/885-infected SPF chicks, necropsy examination at 28 dpi revealed dilation of the oviduct with fluid content (cystic oviduct) in two female chicks. "
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