Experimental infection with cytopathic bovine viral diarrhea virus in mice induces megakaryopoiesis in the spleen and bone marrow.

Here, we infected mice with cytopathic bovine viral diarrhea virus 1 (cp BVDV1) by oral inoculation and investigated the effects of infection by histopathological, immunohistochemical (IHC), hematological methods. Twelve mice were infected, and samples were obtained at day 2, 5, and 9 postinfection (pi). Most of the infected mice exhibited clinical signs of illness such as reduced movement, crouching, loose feces, loss of appetite, and reduced water intake. Blood samples from six mice were positive for BVDV based on reverse transcription polymerase chain reaction (RT-PCR). Blood analysis also revealed thrombocytopenia and lymphopenia. Viral antigens were detected in the spleen (12/12), bone marrow (12/12), and/or mesenteric lymph nodes (4/12) of all infected mice by IHC analysis. The spleens showed significant histopathological changes including (i) substantially increased numbers of megakaryocytes, (ii) lymphocyte depletion, and (iii) hemorrhages. The bone marrow also had an increased number of megakaryocytes, although this increase was not as strong as it was in the spleen. Severe lymphoid depletion was observed in the mesenteric lymph nodes. Viral infections were present in the lymphocytes but not detected in megakaryocytes of the spleen, bone marrow, or mesenteric lymph nodes. These results suggest that the increased numbers of megakaryocytes may be a direct result of BVDV infection. BVDV infection in mice following oral inoculation of cp BVDV1 leads to megakaryopoiesis in the spleen and bone marrow to replenish the platelets.

Noncytopathic bovine viral diarrhea virus 2 impairs virus control in a mouse model.

Bovine viral diarrhea virus (BVDV) is an economically important pathogen that causes development of mild to severe clinical signs in wild and domesticated ruminants. We previously showed that mice could be infected by BVDV. In the present study, we infected mice intraperitoneally with non-cytopathic (ncp) BVDV1 or ncp BVDV2, harvested the blood and organs of the infected mice at days 4, 7, 10 and 14 postinfection (pi), and performed immunohistochemical analyses to confirm BVDV infection. Viral antigens were detected in the spleens of all infected mice from days 4 through 14 and were also found in the mesenteric lymph nodes, gut-associated lymphoid tissue (GALT), heart, kidney, intestine, and bronchus-associated lymphoid tissue (BALT) of some infected mice. In ncp BVDV2-infected mice, flow cytometric analysis revealed markedly fewer CD4(+) and CD8(+) T lymphocytes and lower expression of costimulatory molecules CD80 (B7-1) and CD86 (B7-2) and major histocompatibility complex (MHC) class II (I-A/I-E) than those in ncp BVDV1-infected mice. Production of the cytokines interleukin (IL)-6 and monocyte chemotactic protein (MCP)-1 was higher in the plasma of ncp BVDV2-infected mice than that in that of ncp BVDV1-infected mice. Our results demonstrate that ncp BVDV1 and ncp BVDV2 interact differently with the host innate immune response in vivo. These findings highlight an important distinction between ncp BVDV1 and ncp BVDV2 and suggest that ncp BVDV2 impairs the host's ability to control the infection and enhances virus dissemination.

Experimental infection of mice with bovine viral diarrhea virus.

The objective of this study was to test the ability of bovine viral diarrhea virus (BVDV) to infect mice. Two mice each were either mock infected or inoculated with one of three BVDV strains by the intraperitoneal (IP) (n = 8) or intranasal (IN) (n = 8) route. All mice were euthanized at day 7 postinfection (p.i.). None of the infected mice exhibited any clinical signs of illness; however, the tissues harvested after BVDV challenge showed significant histopathological changes. Blood samples from five mice that were injected IP and one mouse that was inoculated IN were positive for BVDV by reverse transcription polymerase chain reaction (RT-PCR). Immunohistochemistry (IHC) was used to assess the presence of viral antigen in the organs of mice infected with three BVDV strains. In IP-injected mice, BVDV antigen was detected in the spleen (5/6), mesenteric lymph nodes (4/6), lymphatic tissue of the lung (3/6), lung (1/6), and stomach (1/6) of the infected mice; however, it was not detected in the liver (0/6) or kidney (0/6). In IN-inoculated mice, BVDV antigen was detected in the lung and mesenteric lymph nodes of one BVDV-infected mouse but was not detected in other tissues. The results of this study suggest that the spleen is the most reliable tissue for BVDV antigen detection using IHC in the IP-injected group. Our study demonstrates that mice can be infected by BVDV. This is the first report of BVDV infection in mice.

Detection of Tick-Borne Pathogens in the Korean Water Deer (Hydropotes inermis argyropus) from Jeonbuk Province, Korea.

The objective of this study was to investigate the prevalence of tick-borne pathogens in the Korean water deer (Hydropotes inermis argyropus). Pathogens were identified using PCR which included Anaplasma, Ehrlichia, Rickettsia, and Theileria. Rickettsia was not detected, whereas Anaplasma, Ehrlichia, and Theileria infections were detected in 4, 2, and 8 animals, respectively. The most prevalent pathogen was Theileria. Of the 8 Theileria-positive animals, 2 were mixed-infected with 3 pathogens (Anaplasma, Ehrlichia, and Theileria) and another 2 animals showed mixed-infection with 2 pathogens (Anaplasma and Theileria). Sequencing analysis was used to verify the PCR results. The pathogens found in this study were identified as Anaplasma phagocytophilum, Ehrlichia canis, and Theileria sp. To the best of our knowledge, this is the first report identifying these 3 pathogens in the Korean water deer. Our results suggest that the Korean water deer may serve as a major reservoir for these tick-borne pathogens, leading to spread of tick-borne diseases to domestic animals, livestock, and humans. Further studies are needed to investigate their roles in this respect.

Detection of Anaplasma sp. in Korean Native Goats (Capra aegagrus hircus) on Jeju Island, Korea.

Anaplasma species are obligate intracellular pathogens that can cause tick-borne diseases in mammalian hosts. To date, very few studies of their occurrence in Korean native goats (Capra aegagrus hircus) have been reported. In the present study, we investigated Anaplasma infection of Korean native goats on Jeju Island, Republic of Korea, and performed phylogenetic analysis based on the 16S rRNA gene sequences. Our results showed that Anaplasma infection was found mostly in adult female goats. The phylogenetic tree revealed that the 7 sequences identified in Korean native goats could belong to Anaplasma sp. and were distinct from A. marginale, A. centrale, and A. ovis. The results indicated that the sequences identified to belong to Anaplasma were closely related to sequences isolated from goats in China and were clustered within the same group. To our knowledge, this is the first study to detect Anaplasma sp. infection in Korean native goats.

Pathogenetic differences after experimental infection of calves with Korean non-cytopathic BVDV-1 and BVDV-2 isolates.

The purpose of this study was to compare clinical and virological differences between non-cytopathic (ncp) bovine viral diarrhea virus (BVDV)-1 and ncp BVDV-2 isolated from Korean field cases. Each five naïve calves were experimentally infected with Korean ncp BVDV-1 or BVDV-2 isolates. Two additional age-matched animals were used as uninfected controls. Leukocyte, lymphocyte, and platelet counts declined in all infected calves, but were significantly lower and remained decreased longer in calves infected with ncp BVDV-2 isolate. The number of monocytes was greater in calves infected with ncp BVDV-2. Flow cytometric assay showed that lymphocyte apoptosis occurred with an increase of annexin-V positive cells in all infected calves by day 6. Tumor necrosis factor alpha (TNF-α) concentration in all infected calves was lower than in control calves. In ncp BVDV-1 infected calves, interferon gamma (IFN-γ) levels in the serum were increased by day 6 compared to calves infected with ncp BVDV-2. These results demonstrated that the Korean ncp BVDV-2 isolate shows a reduced IFN-γ production, indicating prevention of the antiviral activity, and therefore promotes the development of pathological effects.