CategorySwine Health - General Disease
Date Full Report Received03/02/2016
Date Abstract Report Received03/02/2016
Funded ByNational Pork Board
Rotavirus is not a new disease within the swine industry; however, there is an evidence of re-emergence and importance in neonates and early weaned piglets. Group C rotaviruses often cause neonatal and pre-weaning diarrhea while group A rotavirus infection is still predominantly a post-weaning enteric disease problem. A typical approach for control of rotavirus-associated disease in piglets is boosting the immunity of dams for the virus and transferring maternal immunity to the piglets until the pig reaches an age at which it is less susceptible to rotavirus infection and associated disease. Commercial and autogenous vaccines have been utilized by producers to control group A rotavirus although those have been variably effective. In contrast, enteric disease associated with group C rotavirus has been more difficult, if not possible, to control because of the inability to grow this rotavirus in laboratory which prevents production of a conventional vaccine. The only effective control measure currently being used is planned exposure (i.e., “feedback”) of dams to a farm-specific live rotavirus isolates 2-5 weeks pre-farrow in attempt to boost their immunity against farm-specific virus and enhance transfer of maternal immunity to piglets. Despite the effort, efficacy has been variable and often poor and group C rotavirus continues to be a major problem in neonatal and pre-weaning diarrhea and mortality, raising the need for better understanding of immune-mediated protection against group B or C in piglets.
The proposed study was designed to address if maternal/lactogenic immunity correlates with protection against rotavirus C-associated disease in piglets as well as ontogeny of antibody response to various vaccine forms in old pigs. Two animals experiments were conducted. The first animal experiment involved passive transfer of rotavirus-specific IgG to mimic the maternal immunity in neonates and assess if the level of maternal antibody correlate with protection against oral challenge of rotaviruses. CDCD piglets were fed concentrated IgG raised against a porcine rotavirus C isolate right after birth and monitored for antibody decay and protection against challenge over time. In the second animal experiment, the ontogeny of antibody response of pigs after receiving cell-culture derived live virus, ice cubes containing rotavirus-positive feces and recombinant VP7 was characterize in attempt to estimate the level of material antibody which can be passively transferred to piglets via colostrum. Our study demonstrated that: a) naïve pigs could develop serum antibody response with neutralizing activity when they were given a low dose of live virus orally or injected with a recombinant viral protein; b) virus neutralizing antibody response appeared to be subtype-specific (i.e., G type); and c) orally fed virus-specific immunoglobulin could reduce the severity of disease by rotavirus but not infection.
Our study observations suggest that: a) immunoglobulin feeding can be an option for temporary relief of clinical severity due to group C rotavirus infection and b) while both killed and live vaccines can be options for control, its use depends upon farm status with rotavirus. More importantly subtype matching should be taken into consideration when devising a vaccine for better efficacy.