# Molecular Characterisation, Tissue Distribution and Pathology of Circovirus parrot and Gammapolyomavirus avis in Naturally Coinfected Psittacine Birds in Bangladesh

## TL;DR

This study investigates the molecular characteristics, tissue distribution, and pathology of two viruses in parrots from Bangladesh, revealing insights into their effects and potential control measures.

## Contribution

The study provides new insights into the molecular and pathological effects of Circovirus parrot and Gammapolyomavirus avis coinfection in naturally infected birds.

## Key findings

- Circovirus parrot showed high detection rates in bone marrow, cloacal swab, feather, and oral swab tissues.
- Gammapolyomavirus avis was predominantly detected in bone marrow and feather tissues.
- Molecular analysis suggests a unique genotype of Circovirus parrot circulating in Bangladesh.

## Abstract

Circovirus parrot and Gammapolyomavirus avis are two clinically important viruses affecting psittacine birds. Although several studies have investigated their genomic variability, pathogenesis and associated pathological features individually, understanding of the effects and pathogenesis of Circovirus parrot and Gammapolyomavirus avis coinfection remains limited. This study was designed to investigate the molecular characteristics of Circovirus parrot and Gammapolyomavirus avis, tissue distribution of the viruses and histopathology during the course of the disease in naturally infected birds.

A total of 16 Circovirus parrot and Gammapolyomavirus avis polymerase chain reaction (PCR)–positive budgerigars (Melopsittacus undulatus) were euthanised, including six without clinical signs and 10 with clinical signs. Ten types of tissue samples were screened using real‐time PCR to detect viruses. Molecular characterisation of the viruses was determined using partial genome sequencing. Additionally, histopathological examination was performed to investigate cellular changes.

Viral distribution varied significantly between tissues (p < 0.001) with proportionately higher detection rates in bone marrow (16/16, 100%), cloacal swab (16/16, 100%), feather (15/16, 93.75%) and oral swab (16/16, 100%) for Circovirus parrot and in bone marrow (16/16, 100%) and feather (9/16, 56.25%) for Gammapolyomavirus avis, than in other tissue types. No significant variation was observed in detection rate between birds with and without clinical signs for both Circovirus parrot (p = 0.86) and Gammapolyomavirus avis (p = 0.55). Cellular necrosis and degenerative changes were observed in different tissues, with or without the presence of viral DNA. Molecular analysis suggests that the Circovirus parrot circulating in Bangladesh may represent a unique genotype and shares an ancestral relationship with currently circulating strains, whereas Gammapolyomavirus avis appears to be less diverse and shares an ancestral relationship with both local and global isolates.

Findings of this study will be useful in understanding the molecular aspects of pathogenesis and disease epidemiology, thus aiding in the design of effective control measures of these diseases.