Goose Parvovirus and Circovirus Coinfections in Ornamental Ducks

First report of goose circovirus identified in ducks from China

Goose circovirus (GoCV) is a common pathogen that causes immunosuppression and promotes secondary infections with other infectious agents in geese worldwide. In the present study, we identified GoCV in 2 out of 93 duck flocks from China and successfully sequenced the complete genomes of 2 strains (AH22du and HN20du). The whole genome of the two strains shared a high identity of 90.5 to 98.63% with China GoCV reference, and low identity of 58.98% with DuCV reference, respectively. Phylogenetic tree constructed on the two and other genome sequences of GoCV revealed three main branches. Both strains sequenced in this study were distributed on different sub-branches with most other Chinese GoCV strains, and AH22du clustered into an independent sub-branch within the cluster. Recombination analysis predicted that HN20du might potentially recombine from the major parent of yk4 (Zhejiang Province, China, 2007) and minor parent of GD/YJ/g2 (Guangdong Province, China, 2020). To the best of our knowledge, this is the first report of GoCV in ducks from China. This broadened host spectrum of GoCVs requires attention from the waterfowl industry and researchers.

Advances in research on genetic relationships of waterfowl parvoviruses

Derzsy’s disease and Muscovy duck parvovirus disease have become common diseases in waterfowl culture in the world and their potential to cause harm has risen. The causative agents are goose parvovirus (GPV) and Muscovy duck parvovirus (MDPV), which can provoke similar clinical symptoms and high mortality and morbidity rates. In recent years, duck short beak and dwarfism syndrome has been prevalent in the Cherry Valley duck population in eastern China. It is characterised by the physical signs for which it is named. Although the mortality rate is low, it causes stunting and weight loss, which have caused serious economic losses to the waterfowl industry. The virus that causes this disease was named novel goose parvovirus (NGPV). This article summarises the latest research on the genetic relationships of the three parvoviruses, and reviews the aetiology, epidemiology, and necropsy characteristics in infected ducks, in order to facilitate further study.

Normal Electrocardiographic Pattern in Conscious Healthy Domestic Geese (Anser anser)

The aim of this study was to describe the reference intervals of electrocardiographic patterns and values in conscious healthy domestic geese (Anser anser). Standard bipolar and augmented unipolar limb lead electrocardiograms with a direct writing electrocardiograph were recorded in 14 domestic geese. The durations of PR interval, QRS complex, ST and QT intervals, the net of the QRS complex, and the P and T amplitudes were determined at 50 mm/s and at 1 cm = 1 mV. The polarity waveform was examined. The mean electrical axis in the frontal plane was determined in leads II and III. Data are expressed as means and standard deviations. The mean (SD) heart rate was 153.8 (22.4) beats/min. The QRS complex was mainly negative in leads II and III; it was positive in the augmented vector right, augmented vector left, and augmented vector foot leads. The T wave was positive in leads II, III, and the augmented vector foot lead and was negative in the augmented vector right and left leads. The mean electrical axis ranged between -30° to -140°. Electrocardiogram recordings were well tolerated by the geese. The reference intervals provided here can be used to assist in the interpretation of electrocardiographic patterns in geese.

Molecular analysis of goose parvovirus field strains from a Derzsy's disease outbreak reveals local European-associated variants

Since its first recognition in the early 1960s, Derzsy's disease has caused significant economic losses in the goose meat industry through the world. Today, Derzsy's disease still maintains its importance for small-scale waterfowl farming, despite not having a significant impact on public health. In the present study, we investigated the distribution of goose parvovirus (GPV) and its potential variants from a 2019 outbreak in Turkey. Tissue samples were obtained from infected eggs and goslings that were raised in distinct farming areas of the various provinces. For this purpose, a novel primer set for amplification of a 630-bp region of VP3 was designed to confirm GPV infection by conventional PCR method. A 4709-base nucleotide sequence including the structural, non-structural, and 5' inverted terminal repeat regions was obtained from three samples from the Central Anatolian region. Multiple sequence comparisons and phylogenetic analysis demonstrated that the field strains clustered with European group 2 and contained a series of unique amino acid substitutions that might affect the virulence of the virus. These results confirmed that European-related field strains caused the outbreak in Asia Minor, and this might assist in understanding the circulation of GPV in Asia and Europe.

The differences in intestinal growth and microorganisms between male and female ducks

There are great differences in physiological and biological functions between animals of different sexes. However, whether there is a consensus between sexes in duck intestinal development and microorganisms is still unknown. The current study used Nonghua ducks to estimate the effect of sex on the intestine by evaluating differences in intestinal growth indexes and microorganisms. The intestines of male and female ducks were sampled at 2, 5, and 10 wk from the duodenum, jejunum, ileum, and cecum. Then, the intestinal length and weight were measured, the morphology was observed with HE staining, and the intestinal content was analyzed by 16S rRNA sequencing. The results showed that male ducks have shorter intestinal lengths with higher relative weights/relative lengths. The values of jejunal villus height (VH)/crypt depth (CD) of female ducks were significantly higher at 2 wk, whereas the jejunal VH/CD was significantly lower at 10 wk. There was obvious separation of microorganisms in each intestinal segment of ducks of different sexes at the 3 time periods. The dominant phyla at different stages were Firmicutea, Proteobacteria, Bacteroidetes, and Actinobacteria. The duodenal Chao index at the genus level of male ducks was significantly higher at 10 wk than that of female ducks. Significantly different genera were found only in the jejunum, and the abundances of Escherichia_Shigella, Pseudomonas, Clostridium_sensu_stricto_1, Sphingomonas, and Desulfovibrio in male ducks were higher than those in female ducks, whereas the abundance of Rothia was lower, and the abundance of viral infectious diseases, lipid metabolism, metabolism of terpenoids and polyketides, parasitic infectious diseases, xenobiotic biodegradation and metabolism, cardiovascular disease, and metabolism of other amino acids in male ducks were higher than that in female ducks, whereas gene folding, sorting and degradation pathways, and nucleotide metabolism were lower. This study provides a basic reference for the intestinal development and microbial symbiosis of ducks of different sexes.

Effect of Goose Parvovirus and Duck Circovirus Coinfection in Ducks

Introduction

Coinfection of goose parvovirus (GPV) and duck circovirus (DuCV) occurs commonly in field cases of short beak and dwarfism syndrome (SBDS). However, whether there is synergism between the two viruses in replication and pathogenicity remains undetermined.

Material and Methods

We established a coinfection model of GPV and DuCV in Cherry Valley ducks. Tissue samples were examined histopathologically. The viral loads in tissues were detected by qPCR, and the distribution of the virus in tissues was detected by immunohistochemistry (IHC).

Results

Coinfection of GPV and DuCV significantly inhibited growth and development of ducks, and caused atrophy and pallor of the immune organs and necrosis of the liver. GPV and DuCV synergistically amplified pathogenicity in coinfected ducks. In the early stage of infection, viral loads of both pathogens in coinfected ducks were significantly lower than those in monoinfected ducks (P < 0.05). With the development of the infection process, GPV and DuCV loads in coinfected ducks were significantly higher than those in monoinfected ducks (P < 0.05). Extended viral distribution in the liver, kidney, duodenum, spleen, and bursa of Fabricius was consistent with the viral load increases in GPV and DuCV coinfected ducks.

Conclusion

These results indicate that GPV and DuCV synergistically potentiate their replication and pathogenicity in coinfected ducks.

Clinical and Histologic Characterization of Co-infection with Astrovirus and Goose Parvovirus in Goslings

Goose astrovirus is a novel and distinct astrovirus that causes fatal visceral gout in 4- to 21-day-old goslings. Goose parvovirus is the etiologic agent of Derzsy disease, an acute, contagious, and fatal disease that affects mainly young goslings. This paper describes the clinical signs and gross and histopathologic features of co-infection with astrovirus and goose parvovirus. Clinical signs and history included increased mortality, depression, anorexia, enteritis, joint swelling, and paralysis. Postmortem examination showed a considerable amount of urate covering the internal organs, especially the heart, liver, and kidney. Some goslings had swollen duodenum and ileum. Histologic lesions in the kidney, liver, spleen, lung, proventriculus, and brain included hemorrhage, congestion, edema, cell necrosis, inflammatory cell infiltration, and an eosinophilic protein-like substance in renal tubules. The extensive infiltration of heterophil myelocytes into the kidney, spleen, liver, lung, bursa of Fabricius, and pancreas is a new finding.

Pathological lesions in the immune organs of ducklings following experimental infection with goose parvovirus

Goose parvovirus (GPV) is the etiological agent of Derzsy's disease, with a natural reservoir consisting only of geese and Muscovy ducks. However, the pathological changes in the immune organs of ducklings experimentally infected with GPV remain unknown. In this study, 2-day-old Cherry Valley ducklings were intramuscularly injected with GPV. Immune organs (e.g., thymus, bursa of Fabricius, spleen, Harderian gland, cecal tonsil, bone marrow, and peripheral blood lymphocytes [PBLs]) were collected 1, 3, 5, 7, 10, and 14 days post-infection (dpi). Pathological lesions were assessed by histology and the viral load was concurrently assessed using quantitative real-time polymerase chain reaction. GPV antigen was detected via immunofluorescence staining and immunohistochemistry. No clinical symptoms or death were observed in the infected ducklings from 1 to 14 dpi; however, lesions with different degrees of hemorrhage and hyperemia were observed in the thymus, spleen and Harderian gland. Lymphocyte necrosis was identified in the thymus and spleen. In the immune organs, the highest viral loads were found in the spleen at 7 dpi, followed by the bone marrow, PBLs, and cecal tonsil at 3 dpi, and the bursa, Harderian gland, and thymus at 1 dpi. GPV antigen was primarily expressed in the cecal tonsil, spleen, and Harderian gland at 5 dpi, as well as in the PBLs and bone marrow at 3 dpi. Our findings indicate widespread GPV replication and dissemination in the immune organs of Cherry Valley ducklings.

Epidemiological investigation of H9 avian influenza virus, Newcastle disease virus, Tembusu virus, goose parvovirus and goose circovirus infection of geese in China

To deepen the knowledge about epidemic prevalence in the goose breeding field, a triplex PCR assay was established, and 478 samples were collected from scaled goose farms in 11 provinces in China. The results of this epidemiological investigation showed that incidence rates of H9 avian influenza and goose circovirus were the highest among five infectious diseases that were evaluated. In addition, the triplex PCR assay established remarkable sensitivity, rapidity and versatility compared to other diagnostic methods. Dual infection comprised a large proportion of the co-infections in the field, of which the combinations of H9/Tembusu, H9/goose circovirus and goose circovirus/Tembusu co-infected cases were more common. Epidemics were more severe in winter and spring. Additionally, significant differences in the prevalence of these infectious diseases were observed in association with different age groups. In addition, phylogenetic analysis, determined by the neighbour-joining method, was carried out to investigate the evolution of these viruses during the study period. For the most part, virus strains isolated during the study were consistent with most goose-origin strains isolated from the Chinese mainland over the past few years. However, mutations were observed between isolated H9 avian influenza virus strains and sequences available from GenBank, which should draw much attention.