Molecular Characterization and Pathogenicity of the Novel Recombinant Muscovy Duck Parvovirus Isolated from Geese.

Goose parvovirus (GPV) and Muscovy duck parvovirus (MDPV) are the main agents associated with waterfowl parvovirus infections that caused great economic losses in the waterfowl industry. In 2020, a recombinant waterfowl parvovirus, 20-0910G, was isolated in a goose flock in Taiwan that experienced high morbidity and mortality. The whole genome of 20-0910G was sequenced to investigate the genomic characteristics of this isolate. Recombination analysis revealed that, like Chinese rMDPVs, 20-0910G had a classical MDPV genomic backbone and underwent two recombination events with classical GPVs at the P9 promoter and partial VP3 gene regions. Phylogenetic analysis of the genomic sequence found that this goose-origin parvovirus was highly similar to the circulating recombinant MDPVs (rMDPVs) isolated from duck flocks in China. The results of experimental challenge tests showed that 20-0910G caused 100% mortality in goose embryos and in 1-day-old goslings by 11 and 12 days post-inoculation, respectively. Taken together, the results indicated that this goose-origin rMDPV was closely related to the duck-origin rMDPVs and was highly pathogenic to young geese.

Human chorionic gonadotropin (hCG)-induced ovulation occurs later but with equal occurrence in lactating dairy cows: comparing hCG and gonadotropin-releasing hormone protocols.

This study assessed the effects of two hormones, human chorionic gonadotropin (hCG) and gonadotropin-releasing hormone (GnRH), on ovulatory responses during different diestrous stages in lactating dairy cows. Estrous cycles of 21 cows were synchronized and were enrolled in stage 1 of the experiment. The cows were treated with a prostaglandin (PG) F2α analog either 9 to 10 days [mid-diestrus (MD) group] or 5.5 to 6.5 days [early-diestrus (ED) group] after synchronized ovulation (day 0 = first PGF2α administration). On day 2, the cows were administrated 250 µg GnRH or 3000 IU hCG. Ovulation was determined every 2 h from 24 to 36 h after GnRH or hCG administration, and then every 4 h up to 72 h until ovulation. Cows in stage 2 were administered these treatments in the reverse order. The results indicated that average ovulation times in cows treated with GnRH in the MD group (GnRH-MD group) and cows treated with GnRH in the ED group (GnRH-ED group) were 30.0 ± 1.0 h and 28.8 ± 0.4 h, respectively. However, ovulation times for cows treated with hCG in the MD group (hCG-MD group) and cows treated with hCG in the ED group (hCG-ED group) were 35.8 ± 4.6 h and 32.8 ± 2.2 h, respectively, and ovulation occurred significantly later in the hCG-treated groups than in the GnRH-treated groups. In summary, we found that hCG-induced ovulation occurred later than GnRH-induced ovulation regardless of different diestrous peroids; however, the two treatments did not differ in terms of percentage of ovulation.

Prevalence and Genotyping of Chlamydia psittaci from Domestic Waterfowl, Companion Birds, and Wild Birds in Taiwan.

Chlamydia psittaci, the causative agent of avian chlamydiosis, an important zoonotic disease, infects a wide range of birds. Infected birds, whether symptomatic or asymptomatic, intermittently shed the agent through respiratory and intestinal routes. Therefore, it is essential to investigate the epizootiology of C. psittaci in poultry, pet birds, and wild birds. In this study, cloacal or fecal swabs collected from domestic waterfowl, psittacine birds, Columbidae, and wild birds were used to determine the prevalence of C. psittaci in Taiwan between 2014 and 2017. The C. psittaci infection rate was as high as 34.2% among domestic waterfowl farms. The waterfowl isolates clustered into two groups based on ompA phylogeny: one group (G1-like) clustered with the Polish G1 strains; the other group (waterfowl-TW) clustered near, but independently from, the classical ABE genotype cluster. Separately, 3.1% of parrot samples tested positive for C. psittaci belonging to genotype A. C. psittaci isolates of genotype B were detected in 10.1% of racing pigeons and other Columbidae. Wild bird samples from a wildlife refuge had a 2.2% prevalence rate; among these, two atypical C. psittaci genotypes were detected in samples from a Malayan night heron (Gorsachius melanolophus) and a Taiwan barbet (Megalaima nuchalis). Taken together, our results revealed that the risk of C. psittaci transmission from domestic waterfowl and Columbidae birds to humans could be underestimated, given the high prevalence rates in these birds. Furthermore, the free-range rearing system of waterfowl in Taiwan may promote C. psittaci transmission between poultry and wild birds. Pet birds and racing pigeons, which are in close contact with people, are also possible sources for cross-species transmission. Further studies are necessary to elucidate the virulence, biological and genetic characteristics, and modes of transmission of Taiwanese C. psittaci isolates to facilitate the prevention and control of C. psittaci infection.

Sequence diversity and associated pathogenicity of the hemagglutinin cleavage site of H5N2 avian influenza viruses isolated from chickens in Taiwan during 2013-2015.

The sequence at the hemagglutinin (HA) cleavage site (CS) plays a key role in determining the pathogenicity of avian influenza viruses. Three types of HA CS sequences, QREKR/GL, QRKKR/GL and QRRKR/GL, were previously reported in Taiwanese H5N2 viruses that were isolated from chickens from 2003 to 2013. However, no HA CS sequence was reported for viruses isolated after 2013. This article presents the HA CS sequences and pathogenicity of H5N2 viruses that were isolated from chickens in Taiwan during 2013-2015. Two novel HA CS sequences, QKEKR/GL and KREKREKR/GL, were found in the viruses isolated in 2013 and 2014, and pathogenicity tests showed that the viruses with these novel HA CS sequences are low and high pathogenic viruses, respectively. In contrast, the HA CS sequence QREKR/GL was found in all viruses that were isolated in 2015, and all of these viruses were low pathogenic viruses. After 10 passages in embryonated chicken eggs, a virus strain that was isolated in 2003 evolved into a viral quasispecies that contained at least four distinct types of HA CS sequences. These results highlight the potential of Taiwanese H5N2 viruses to change their pathogenicity and HA CS sequences via mutations. Furthermore, viruses with the HA CS sequence QREKR/GL were more prevalent than others in 2015. These findings are useful for understanding the mechanism of sequence changes at the HA CS and for refining H5N2 virus control measures in Taiwan.

Pharmacokinetics and tissue depletion of doxycycline administered at high dosage to broiler chickens via the drinking water.

The recommended use of doxycycline (DC) to broiler chicken is 100 mg/L via the drinking water and a 7-day withdrawal time (WDT). However, study of a higher dosage is desirable because of the possible increase of antimicrobial resistance and disease spectrum. Tissue DC residues exceeding the current maximum residue levels (MRL) was our major concern. Therefore, serum concentration and tissue depletion of DC hyclate after administration of 200 mg/L of DC in the drinking water for five consecutive days were studied. The steady-state DC concentration (8.3 ± 0.9 µg/mL) was reached on the third day of medication. The elimination constant (0.05 ± 0.01 1/h), half-life (14.9 ± 1.4 h), area under concentration versus time curve (81.0 ± 9.9 h·µg/mL) and mean residence time (22.7 ± 2.5 h) were obtained using a non-compartmental pharmacokinetic model. It was determined that the current 7-day WDT regulation was still legitimate for the kidney and liver as well as for the breast and leg muscles, which were estimated by linear regression analysis of the 99% upper distribution limit. The unregulated heart and gizzard were considered safe even when the lowest MRL of muscle (100 ng/g) was applied. While at the present time the extra-label use of drugs is only allowed under specific conditions, in the future it may become necessary to increase the general dosage of DC, and the current results suggest a safe range of DC hyclate in chicken; however, skin/fat tissue residues warrant further studies.

Surveillance of avian and swine influenza in the swine population in Taiwan, 2004.

BACKGROUND AND PURPOSE: We conducted serological and virological surveillance of pig farms in Taiwan from areas epidemic for low pathogenic avian influenza virus (AIV), H5N2 subtype, in order to determine the prevalence of AIV and swine influenza virus (SIV) in 2004. METHODS: Pig sera from 9833 animals from 1974 farms in 9 counties were examined using agar gel precipitation (AGP) to screen for the presence of antibody against influenza A virus. AGP-positive sera were subjected to hemagglutination-inhibition test against H1, H3, H5 and H7 AIV subtypes and H1 and H3 SIV subtypes. Nasal swabs from 881 pigs were also examined for the presence of SIV by virus isolation in specific pathogen-free embryonated chicken eggs. Virus isolates were identified by reverse transcriptase-polymerase chain reaction followed by DNA sequencing of hemagglutinin and neuraminidase genes. RESULTS: The AGP test on sera revealed the presence of antibodies against influenza A virus in 62.6% of farms and in 37.7% of pig sera. SIV antibodies to subtype H1 and H3 were found in 10.8% and 65.8% of sera, respectively. There were two peaks of the serological prevalence of SIV in pigs: one between January and February, and the other in October. By contrast, hemagglutinin tests against H5 and H7 AIV subtypes were negative in all sera, while there was a very low positive rate against H1 and H3 AIV subtypes. One H1N2 and one H3N1 viral isolate were obtained from nasal swabs of pigs. Phylogenetic analysis of hemagglutinin and neuraminidase genes revealed both isolates were reassortants of both classical and recent SIVs. CONCLUSIONS: Different subtypes of SIV co-circulate among swine from different farms within the same county and may cause clinical outbreaks of the disease in Taiwan.