Background: Avian origin canine influenza virus was reported in Korea. The dog to dog contact transmission of the avian origin canine influenza virus (CIV) H3N2 and CIV H3N8 was shown by experimental contact transmission. This study was focused on viral excretion and fever in order to elucidate the epidemiological associations which might be helpful to control the disease transmissions in CIV outbreak in dogs. Methods: An influenza seronegative 10-week-old Beagle dog was experimentally inoculated with the canine influenza virus A/canine/01/2007, subtype H3N2. Eight hours after inoculation, the infected dog was cohoused with seven uninfected Beagle dogs. Clinical signs including fever were recorded for 14 days post inoculation. Results: The infected dog and four of seven contact dogs in the study showed clinical signs (sneezing, nasal discharge and coughing) during the study. Viral shedding occurred in all of the animals tested and began on 1 to 6 DPI in dogs with clinical signs. Elevated body temperatures above 39.5°C (geometric mean temperature of 39.86°C±0.49) were observed in all symptomatic dogs. The mean viral titer during fever was 2.99 log EID₅₀/ml, which was significantly higher than the viral titer detected in the non fever. Conclusions: The data show that contact dogs with a canine influenza infected dog shed different levels of virus in their nasal excretions and demonstrate that clinical signs, including fever, significantly correlate with the viral shedding.

Background: There have been many efforts to develop efficient vaccines for the control of porcine reproductive and respiratory syndrome virus (PRRSV). Although inactivated PRRSV vaccines are preferred for their safety, they are weak at inducing humoral immune responses and controlling field PRRSV infection, especially when heterologous viruses are involved.Results: In all groups, the sample to positive (S/P) ratio of IDEXX ELISA and the virus neutralization (VN) titer remained negative until challenge. While viremia did not reduce in the vaccinated groups, the IDEXX-ELISA-specific immunoglobulin G increased more rapidly and to significantly greater levels 7 days after the challenge in all the vaccinated groups compared to the non-vaccinated groups (p< 0.05). VN titer was significantly different in the 10⁶PFU/mL PRRSV vaccine-inoculated and binary ethylenimine (BEI)-inactivated groups 22 days after challenge (p< 0.05). Consequently, the inactivated vaccines tested in this study provided weak memory responses with sequential challenge without any obvious active immune responses in the vaccinated pigs.Conclusions: The inactivated vaccine failed to show the humoral immunity, but it showed different immune response after the challenge compared to mock group. Although the 10⁶PFU/mL-vaccinated and BEI-inactivated groups showed significantly greater VN titers 22 days after challenge, all the groups were already negative for viremia.

Since avian-origin H3N2 canine influenza virus (CIV) was first identified in South Korea in 2008, the novel influenza virus has been reported in several countries in Asia. Reverse zoonotic transmission of pandemic H1N1 (2009) influenza virus (pH1N1) has been observed in a broad range of animal species. Viral dominance and characterization of the reassortants of both viruses was undertaken in the present study. Here we describe the viral dominance of 23 CIV reassortants between pH1N1 and canine H3N2 influenza viruses from a naturally co-infected dog. These results indicate that the M gene of pandemic H1N1 and the HA gene of canine H3N2 are predominant in the reassortants. Furthermore, unlike the original canine H3N2 virus, some reassortants showed high pathogenicity in mice. This study suggests that continuous monitoring of influenza infection in companion animals may be necessary to investigate the potential of the emergence of novel influenza viruses.

Background: Recently, new emergence of type I PRRSV has been reported in Korea by several research groups. Although specific subgroups of type I PRRSVs in Korea were observed in the previous phylogenetic analysis, there is a lack of information about the virulence of type I PRRSV recently isolated in Korea. Methods: One type I PRRSV isolate (G2446, 3 times passaged in primarily cultured pulmonary macrophages) in Korea was experimentally infected in colostrum-deprived pigs. The pathological and serological evaluations were performed and compared to type II PRRSV strain (CP07-401-9, 5 times passaged in MARC-145 cell lines)-infected pigs, for 21 days post challenge (dpc). Results: The pneumonia found in gross examination was more severe in type I PRRSV-infected pigs than type II PRRSV-infected pigs. Both groups showed bronchointerstitial pneumonia, mild multifocal perivascular lymphohistiocytic myocarditis and lymphadenopathy at 14 dpc. However, the unique histopathologic lesions were not found in the pigs experimentally infected with a Korean type I PRRSV isolate, when compared to previous data about classical pathology of PRRSV. The PRRS-specific antibodies were detected in the first week after challenge and viremia continued at least until 21 dpc in both groups. Conclusion: The gross and histopathologic lesion in this study indicated that Korean type I PRRSV strain (G2446) caused classical PRRSV-specific lesions. Although this study evaluated one representative strain of Korean type I PRRSV, the results may provide information regarding the pathogenicity of type I PRRSV recently emerged in Korea.