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Formalin-fixed, paraffin-embedded tissues from European rabbits ( Oryctolagus cuniculus) that succumbed to rabbit hemorrhagic disease virus 2 (RHDV2; Lagovirus GI.2) during the 2019 outbreak in Washington, USA, were utilized for in situ hybridization via RNAscope (ACDBio). This detection method was both sensitive and specific, with no staining in tissues from RHDV- ( Lagovirus GI.1) and RHDV2-negative rabbits, and only slight background staining of RHDV-positive rabbits; RHDV2-positive tissues had bright-red cytoplasmic staining. Although much of the viral mRNA detection was consistent with previously described antigen detection via immunohistochemistry of the liver, lungs, and spleen, there was also significant glomerular staining in the kidneys, and endothelial staining within blood vessels of almost all organs. We validated the RNAscope technique for detection of RHDV2 mRNA in formalin-fixed, paraffin-embedded tissues, with increased sensitivity from previous techniques, and identified additional affected cell types that may contribute to the understanding of pathogenesis.

Theileria parva kills over one million cattle annually in sub-Saharan Africa. Parasite genetic complexity, cellular response immunodominance, and bovine MHC diversity have precluded traditional vaccine development. One potential solution is gene gun (GG) immunization, which enables simultaneous administration of one or more DNA-encoded antigens. Although promising in murine, porcine, and human vaccination trials, bovine GG immunization studies are limited. We utilized the model T. parva antigen, polymorphic immunodominant molecule (PIM) to test bovine GG immunization. GG immunization using a mammalian codon optimized PIM sequence elicited significant anti-PIM antibody and cell-mediated responses in 7/8 steers, but there was no difference between immunized and control animals following T. parva challenge. The results suggest immunization with PIM, as delivered here, is insufficient to protect cattle from T. parva. Nonetheless, the robust immune responses elicited against this model antigen suggest GG immunization is a promising vaccine platform for T. parva and other bovine pathogens.

Giardia cysts are commonly encountered in fecal examinations of dogs; intestinal infections can be asymptomatic or cause diarrhea but have not been previously associated with urticaria. A five-month old dalmatian puppy presented with a one-week history of cutaneous urticaria and pruritis. Wheals were most prominent on the head, abdomen, and inguinal region. A fecal flotation was performed to rule out internal parasites as a cause of hypersensitivity. Fecal float yielded many Giardia cysts, and treatment for giardiasis with fenbendazole was initiated. Urticaria improved drastically within a day after treatment initiation and completely resolved by the completion of the treatment regimen. No Giardia cysts were detected on the follow up fecal flotation three days later, and fecal Giardia antigen testing was negative at this time. No additional changes in management, housing, food, or environment were noted and the puppy has remained without additional clinical signs for three months following initial presentation.

Recombinant herpesvirus vaccine vectors offer distinct advantages in next-generation vaccine development, primarily due to the ability to establish persistent infections to provide sustainable antigen responses in the host. Recombinant bovine herpesvirus-4 (BoHV-4) has been previously shown to elicit protective immunity in model laboratory animal species against a variety of pathogens. For the first time, we describe the induction of antigen-specific immune responses to two delivered antigens in the host species after intranasal nebulization of recombinant BoHV-4 expressing the chimeric peptide containing the bovine viral diarrhea virus (BVDV) glycoprotein E2 and the bovine herpesvirus 1 (BoHV-1) glycoprotein D (BoHV-4-A-CMV-IgK-gE2gD-TM). In this study, four cattle were immunized via intranasal nebulization with the recombinant BoHV-4 construct. Two of the cattle were previously infected with wild-type BoHV-4, and both developed detectable serologic responses to BVDV and BoHV-1. All four immunized cattle developed detectable viral neutralizing antibody responses to BVDV, and one steer developed a transient viral neutralizing response to BoHV-1. Approximately one year after immunization, immunosuppressive doses of the glucocorticoid dexamethasone were administered intravenously to all four cattle. Within two weeks of immunosuppression, all animals developed viral neutralizing antibody responses to BoHV-1, and all animals maintained BVDV viral neutralizing capacity. Overall, nebulization of BoHV-4-A-CMV-IgK-gE2gD-TM persistently infects cattle, is capable of eliciting antigen-specific immunity following immunization, including in the presence of pre-existing BoHV-4 immunity, and recrudescence of the virus boosts the immune response to BoHV-4-vectored antigens. These results indicate that BoHV-4 is a viable and attractive vaccine delivery platform for use in cattle.

Tick-borne pathogens that cause persistent infection are of major concern to the livestock industry because of transmission risk from persistently infected animals and the potential economic losses they pose. The recent reemergence of Theileria equi in the United States prompted a widespread national survey resulting in identification of limited distribution of equine piroplasmosis (EP) in the U.S. horse population. This program identified Babesia caballi -seropositive horses using rhoptry-associated protein 1 (RAP-1)–competitive enzyme-linked immunosorbent assay (cELISA), despite B. caballi being considered nonendemic on the U.S. mainland. The purpose of the present study was to evaluate the suitability of RAP-1–cELISA as a single serological test to determine the infection status of B. caballi in U.S. horses. Immunoblotting indicated that sera from U.S. horses reacted with B. caballi lysate and purified B. caballi RAP-1 protein. Antibody reactivity to B. caballi lysate was exclusively directed against a single ∼50-kDa band corresponding to a native B. caballi RAP-1 protein. In contrast, sera from experimentally and naturally infected horses from regions where B. caballi is endemic bound multiple proteins ranging from 30 to 50 kDa. Dilutions of sera from U.S. horses positive by cELISA revealed low levels of antibodies, while sera from horses experimentally infected with B. caballi and from areas where B. caballi is endemic had comparatively high antibody levels. Finally, blood transfer from seropositive U.S. horses into naive horses demonstrated no evidence of B. caballi transmission, confirming that antibody reactivity in cELISA-positive U.S. horses was not consistent with infection. Therefore, we conclude that a combination of cELISA and immunoblotting is required for the accurate serodiagnosis of B. caballi .