Search

Simple Summary: Theileria orientalis Ikeda poses significant challenges to the cattle industry, encompassing economic repercussions, trade-related issues, and constraints regarding control and treatment measures. This parasite can precipitate a range of adverse effects in cattle, including diminished milk production, weight loss, anemia, and, in severe instances, cattle fatalities. These adverse impacts directly translate into economic burdens for farmers and the broader cattle industry. The financial costs associated with treating afflicted animals and implementing control strategies can be substantial. Additionally, occurrences of Theileria orientalis Ikeda in regions where it is not endemic can lead to trade restrictions and impediments affecting both cattle and cattle products. This can curtail the international movement of cattle and influence global trade in livestock. Furthermore, there is a dearth of effective treatment options for infected cattle, and severe cases frequently culminate in fatalities. This lack of viable treatment exacerbates the difficulties in disease management. Addressing the presence of Theileria orientalis Ikeda in the USA necessitates comprehensive efforts to understand the prevalence and distribution of the pathogen. This study utilizing PCR followed by DNA sequencing identified two cases of Theileria orientalis Ikeda-positive cattle, marking the first report of this virulent genotype in Alabama, USA. Theileria orientalis Ikeda genotype, a parasite causing a disease in cattle that leads to significant economic challenges in Asia, New Zealand, and Australia, has been identified in seven U.S. States since 2017. Two previously validated PCR tests for Theileria followed by DNA sequencing were performed to test blood samples collected from 219 cattle in Alabama, USA, during the period of 2022–2023. Bidirectional Sanger sequencing revealed that the MPSP gene sequences (639–660 bp) from two cattle in Lee and Mobile Counties of Alabama exhibited a 100% match with those of recognized T. orientalis Ikeda strains, and showed similarities ranging from 76% to 88% with ten other T. orientalis genotypes. A high copy number of T. orientalis Ikeda was detected in the blood of infected cattle (ALP-1: 1.7 × 105 and 1.3 × 106/mL whole blood, six months apart; ALP-2: 7.1 × 106/mL whole blood). Although the confirmed competent vector for T. orientalis Ikeda, Haemaphysalis longicornis tick, has not yet been identified in Alabama, the persistent nature of T. orientalis Ikeda infection and the detection of a high pathogen burden in seemingly healthy cattle in this study suggest that other tick species, as well as shared needles and dehorning procedures, could facilitate pathogen transmission within the herd. Continued investigations are necessary for the surveillance of T. orientalis Ikeda and Haemaphysalis longicornis ticks in Alabama and other U.S. states, along with assessing the pathogenicity of T. orientalis Ikeda infections in cattle. [ABSTRACT FROM AUTHOR]

The antigenicity of bovine viral diarrhea virus (BVDV) has been evaluated using virus-neutralizing titer data analyzed by principal component analysis (PCA) and has demonstrated numerous isolates to be antigenically divergent from US vaccine strains. The lack of BVDV-1b strains in currently licensed vaccines has raised concerns regarding the lack of protection against BVDV-1b field strains. The aim of this study was to evaluate the antigenic diversity of BVDV-1b strains and better understand the breadth of antigenic relatedness using BVDV-1b antisera and antisera from vaccine strains. Results from this analysis demonstrate the antigenic diversity observed among BVDV-1b isolates and genetic assignment into the BVDV-1b subgenotype is not representative of antigenic relatedness. This is demonstrated by BVDV-1b isolates (2280N, SNc, Illc, MSU, and 2337) observed to be as antigenically dissimilar as BVDV-2a isolates when using BVDV-1b antisera. Additionally, when BVDV-1a vaccine antisera was used for comparisons, a greater percentage of BVDV-1b isolates clustered with BVDV-1a vaccine strains as part of PC1, suggesting antigenic relatedness and potentially partial protection. Collectively, data from this study would suggest that while most BVDV-1b isolates are antigenically similar, there are antigenically dissimilar BVDV-1b isolates as determined by the lack of cross-reactivity, which may contribute to the lack of protection. [ABSTRACT FROM AUTHOR]

Simple Summary: Bovine respiratory syncytial virus (BRSV) is a common cause of respiratory disease in calves. Vaccination of young calves against BRSV is a common prevention strategy; however, antibodies derived from maternal colostrum interfere with vaccine response and efficacy in young calves. The objective of this study was to determine if vaccination before colostrum absorption results in the effective induction of immune responses and clinical protection in calves. Within 6 h of birth, beef calves were assigned to 2 different treatment groups. Group Vacc (n = 25) was vaccinated with a modified-live virus (MLV) intranasal (IN) BRSV vaccine. Group Control (n = 25) remained unvaccinated. At approximately 3 months of age, calves were experimentally infected with BRSV. Immune responses and viral shedding were evaluated before and after infection. Respiratory signs before and after infection as well as viral shedding were similar between Vacc and Control calves. Local and systemic antibody responses were similar and suggested natural BRSV exposure before experimental infection. Based on the results from this study, early vaccination does not provide advantages for the clinical protection of calves from endemic BRSV farms. Maternal antibodies interfere with BRSV vaccine responses and efficacy in young calves. The objective of this study was to determine if vaccination before the complete absorption of colostral antibodies results in adequate immune priming and clinical protection of beef calves. Within 6 h of life, calves were randomly assigned to 2 different treatment groups. Group Vacc (n = 25) received a single dose of a modified-live virus (MLV) BRSV vaccine intranasally (IN) and group Control (n = 25) received 2 mL of 0.9% saline IN. At approximately 3 months of age, all calves were experimentally challenged with BRSV. Serum and nasal secretion samples were collected before and after challenge for BRSV real-time RT-PCR and antibody testing. Respiratory signs were not observed before challenge. After challenge, respiratory scores were similar between groups. On the challenge day, >40% of calves in each group were febrile. The mean serum and nasal BRSV-specific antibody titers indicated natural BRSV exposure before the experimental challenge in both groups. All calves tested positive for BRSV and had a similar duration of shedding after challenge. Based on these results, vaccination at birth does not offer advantages for immune priming or clinical protection for beef calves in BRSV-endemic cow-calf herds. [ABSTRACT FROM AUTHOR]

Maternal antibodies interfere with BRSV vaccine responses and efficacy in young calves. The objective of this study was to determine if vaccination before the complete absorption of colostral antibodies results in adequate immune priming and clinical protection of beef calves. Within 6 h of life, calves were randomly assigned to 2 different treatment groups. Group Vacc (n = 25) received a single dose of a modified-live virus (MLV) BRSV vaccine intranasally (IN) and group Control (n = 25) received 2 mL of 0.9% saline IN. At approximately 3 months of age, all calves were experimentally challenged with BRSV. Serum and nasal secretion samples were collected before and after challenge for BRSV real-time RT-PCR and antibody testing. Respiratory signs were not observed before challenge. After challenge, respiratory scores were similar between groups. On the challenge day, >40% of calves in each group were febrile. The mean serum and nasal BRSV-specific antibody titers indicated natural BRSV exposure before the experimental challenge in both groups. All calves tested positive for BRSV and had a similar duration of shedding after challenge. Based on these results, vaccination at birth does not offer advantages for immune priming or clinical protection for beef calves in BRSV-endemic cow-calf herds.