Abstract
The objective of the present study was to investigate the effects of Theileria orientalis on the severity of anemia, the prevalence of disease within 21 days after calving and productivity in cows raised inside barns. This longitudinal observational study, which was conducted on a commercial dairy farm in Japan, involved 627 Holstein cows subjected to PCR analysis for T. orientalis. In study 1, we collected blood samples from 156 sick cows within 21 days after calving, and we found the prevalence of T. orientalis infection to be 65.4%. In study 2, we randomly selected 471 cows during the dry period and collected blood samples to conduct PCR analysis for T. orientalis and determined the prevalence of T. orientalis infection to be 69.0%. Compared with the values for the T. orientalis-uninfected group, the T. orientalis-infected cows had significantly decreased hemoglobin concentrations and hematocrit, but there were no differences in the other complete blood count indexes between the two groups. In addition, there were no differences in productivity and the prevalence of major diseases between the T. orientalis-infected and uninfected cows. In summary, T. orientalis had few effects on anemia, productivity and the health of cows raised inside a barn.
Highlights
Theileria orientalis, which is a tick-borne protozoan parasite that causes mild to severe anemia in infected cattle [1], is distributed throughout many countries, including Australia, Britain, Iran, Japan, USA, Korea, and Russia [2]
The outcomes of T. orientalis infections are highly dependent on environmental stress factors [11,12,13], and it is assumed that the protozoan replicates rapidly to cause symptoms, including fever and anemia, when the host is under any stress
The objective of the present study was to investigate the effects of T. orientalis on the degree of anemia with peripartum diseases, the prevalence of diseases within 21 days after calving, and productivity (305-day milk yield and number of days from calving to conception) in cows raised inside a barn in Japan
Summary
Theileria orientalis, which is a tick-borne protozoan parasite that causes mild to severe anemia in infected cattle [1], is distributed throughout many countries, including Australia, Britain, Iran, Japan, USA, Korea, and Russia [2]. Several studies carried out in Hokkaido and Kyushu, Japan, revealed that T. orientalis infections are a potentially serious problem in grazing cattle [6,7]. In Japan, ticks are the main causative agents of horizontal transmission of T. orientalis; approximately 10%. The outcomes of T. orientalis infections are highly dependent on environmental stress factors [11,12,13], and it is assumed that the protozoan replicates rapidly to cause symptoms, including fever and anemia, when the host is under any stress. The peripartum period is the most stressful for cows, and disease status during this period may progress depending on stress levels
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