As early as the 1970s, duck short beak dwarf syndrome (SBDS), caused by goose parvovirus (GPV), was reported in European countries . The main hosts, Muscovy and hybrid Muscovy ducks, exhibit short beaks and severe growth retardation in 10–30% of affected ducks [12, 14]. In 1990, the Taiwan region of China reported the occurrence of SBDS caused by a mixed viral infection of Muscovy duck parvovirus and duck hepatitis virus . At the end of 2014, duck SBDS caused by novel duck parvovirus (NDPV) appeared on duck farms in many provinces and regions in China, which was mainly characterized by skeletal developmental obstacles and severe growth retardation in Cherry Valley ducks, Pekin ducks, mule ducks, and sheldrakes [1, 2, 8, 11, 18]. The mortality rate of this disease is not high (2–6%), but the disabling elimination rate can reach 50%, causing serious economic losses to the duck industry . The disease is still prevalent in some areas, and can be mixed with other virus. At present, there exists no effective vaccine to prevent and control the disease.
Studies have shown that NDPV isolates are more pathogenic to ducks than classical GPV isolates [2, 11]. NDPV not only evolves at a much higher rate than GPV, but also possesses a higher rate of transmission than GPV . This demonstrates the evolutionary dominance of this pathogen and the threat it poses to the duck breeding industry, which cannot be underestimated. Hence, there is an urgent need to develop a vaccine that can prevent and control SBDS.
Although genome sequences and amino acid sequences of NDPV are more than 90% homologous to those of GPV, there still exist differences in key amino acids, such as a change from Ser to Asn at positions 489 and 650 in NDPV, and mutations at positions 7, 116, 366, and 444 [3, 8], which may result in the GPV vaccines to protect ducks against SBDS less effectively. Therefore, the protective efficacy of the GPV vaccine needs to be systematically validated in ducks.
More extensive research has been conducted on the prevention and control of gosling plague, including testing of attenuated and inactivated vaccines. Although attenuated vaccines can stimulate the body to produce an immune response more quickly, their safety is still an issue, which cannot be ignored. There is a risk of the attenuated strain returning to a virulent strain as well as the possibility of recombination with other virulent strains to form new strains with stronger pathogenicity. The causative pathogen of duck SBDS, which was prevalent in 2019 in Linwu, Hunan, was a recombinant NDPV strain composed of N-GPV sdlc01, GPV Y, and the vaccine strain SYG61v . SDLY1602, isolated in Shandong, has been shown to be a recombinant strain formed by the involvement of the primary parental GPV vaccine strain 82-0321v and the secondary parental GPV wild strain GDaGPV . In addition, anti-GPV egg yolk antibodies are clinically used for controlling the disease, but there could be biosafety risks associated with the use of goose egg yolk antibodies for the prevention and control of duck diseases. Therefore, in view of the current situation, the development of an inactivated NDPV vaccine for ducks having SBDS is still the first choice for the prevention of SBDS.
In this study, we developed an inactivated virus vaccine based on NDPV-DS15 for SBDS and tested its efficacy in 112 ducks, which were randomly divided into vaccination, challenge control, vaccination-challenge, and blank control groups.