Outbreak of Chlamydia psittaci Infection in a Commercial Psittacine Breeding Aviary in Argentina

Abstract

Chlamydiosis, caused by Chlamydia psittaci is a bacterial infection found in at least 465 species of birds worldwide. It is highly contagious among birds and can spread to humans. In birds, the disease can manifest itself in acute, subacute, and chronic forms with signs including anorexia, diarrhea, lethargy, weight loss, or, occasionally, mucopurulent or serous oculonasal discharge. This article describes an outbreak of chlamydiosis that occurred in a commercial psittacine breeding aviary in 2021 in Buenos Aires province, Argentina. In total, 16 juvenile blue-fronted parrots, more than 60 blue-fronted parrot chicks, and 2 adult macaws died during the outbreak. In all cases, clinical signs were weight loss, diarrhea, yellowish green excrement, and respiratory distress. The necropsy of four juvenile blue-fronted parrots, two blue-fronted parrot chicks, and two adult macaws revealed cachexia, hepatomegaly, splenomegaly, splenic petechial hemorrhages, ascites, pulmonary edema, and hydropericardium. Histologically, multifocal lymphoplasmacytic and heterophilic airsaculitis, multifocal lymphoplasmacytic and necrotizing hepatitis with intracytoplasmic elementary bodies, multifocal necro-heterophilic hepatitis, multifocal lymphoplasmacytic nephritis, and diffuse heterophilic pneumonia were found. A presumptive diagnosis was established based on gross and microscopic lesions, and it was confirmed using immunohistochemistry and polymerase chain reactions. The sequencing and phylogenetic analysis of the ompA gene revealed genotype A and B of Chlamydia psittaci.

Keywords: Argentina; Chlamydia psittaci; chlamydiosis; outbreak; psittacine breeding aviary.

Figure 1

Post-mortem lesions of organs collected from birds affected by Chlamydia psittaci in a commercial psittacine breeding aviary in Argentina. (A) Marbled surface of the liver with white, irregular, yellowish flat spots of variable size. Juvenile blue-fronted parrot. (B) Marbled cross section of the liver from a red-and-green macaw. (C) Enlarged, pale, and mottled spleen from scarlet macaw. (D) The lung is edematous and moderately congested.

Figure 2

Microscopic lesions of organs collected from birds affected by Chlamydia psittaci in a commercial psittacine breeding aviary in Argentina (A) Air sac: Lymphoplasmacytic and necrotizing multifocal airsacculitis 20X H&E. (B) Liver: Intracytoplasmic elementary bodies in the cytoplasm of hepatocytes and mononuclear cells (black arrows) 40X H&E. (C) Liver: elementary bodies in the cytoplasm of hepatocytes, Gimenez stain (Black arrows). (D) Positive Chlamydia spp. IHC on liver.

Figure 3

Neighbor-joining dendrogram based on comparison of the ompA gene fragment (about 1030 bp) of Chlamydia psittaci. Representative sequences from the different C. psittaci genotypes were included. Samples belonging to this study were pooled organs from juvenile blue-fronted parrots (P2, P3, and P4), pooled trimucosal swabs from blue-fronted parrot chicks (C1 and C2), pooled trimucosal swabs from juvenile blue-fronted parrots (P2 and P3), pooled organs from blue-fronted parrot chicks (C1 and C2), and pooled organs from a scarlet macaw. The GenBank accession numbers were PP751030, PP751031, PP751032, PP751033, and PP706175, respectively. The evolutionary distances were computed using the Kimura 2-parameter method and are in the units of the number of base substitutions per site. Numbers above branches are Bootstrap values as a percentage of 1000 pseudo replicates. C. caviae GPIC was used as an outgroup. The scale bar shows the sequence diversity percentage [32].