Vet. Res. 37 (2006) 745-755
DOI: 10.1051/vetres:2006033

Exacerbation of Chlamydophila psittaci pathogenicity in turkeys superinfected by Escherichia coli

Marnix Van Loock^a, Karolien Loots^a, Marjolein Van Heerden^b, Daisy Vanrompay^c and Bruno Maria Goddeeris<sup>a, d

a</sup>  Department of Biosystems, Division of Gene Technology, Catholic University of Leuven, Kasteelpark Arenberg 30, 3001 Leuven, Belgium
^b  Department of Pathology, Bacteriology and Poultry Disease, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
^c  Department of Molecular Biotechnology, Ghent University, Coupure Links 653, 9000 Gent, Belgium
^d  Department of Virology, Parasitology, Immunology, Salisburylaan 133, 9820 Merelbeke, Belgium

(Received 4 September 2005; accepted 10 April 2006; published online 15 September 2006)

Abstract - Both Chlamydophila psittaci and Escherichia coli infections are highly prevalent in Belgian turkeys and therefore they both might contribute to the respiratory disease complex observed in turkeys. C. psittaci can infect turkeys within the first week of age, even in the presence of maternal antibodies. However, the first C. psittaci outbreaks occur mostly at the age of 3 to 6 weeks, the period when also E. coli infections appear on the farms. Therefore, we examined in this study the pathogenicity of an E. coli superinfection on C. psittaci predisposed turkeys. Turkeys were infected with C. psittaci, E. coli or with C. psittaci followed by E. coli. Simulating the impact of an E. coli infection during the acute phase or the latent phase of a C. psittaci infection, turkeys received E. coli at 1 or 5 weeks post C. psittaci infection, respectively. E. coli superinfection during the acute phase of C. psittaci infection increased C. psittaci excretion and stimulated chlamydial replication in the respiratory tract resulting in exacerbated clinical disease. Interestingly, E. coli superinfection during the latent phase of C. psittaci infection induced chlamydial replication, leading to increased C. psittaci-specific antibody titres. In addition, chlamydial predisposition gave higher E. coli excretion compared with turkeys that had only been infected with E. coli. Overall, the present study clearly demonstrates the pathogenic interplay between C. psittaci and E. coli resulting in more severe respiratory disease.

Key words: Chlamydophila psittaci / Escherichia coli / turkeys

Corresponding author: Bruno.Goddeeris@biw.kuleuven.be

© INRA, EDP Sciences 2006