Effects of Theileria orientalis Ikeda type infection on libido and semen quality of bulls

Theileria orientalis Ikeda infection does not negatively impact growth performance or breeding soundness exam results in young beef bulls at bull test stations

Introduction

Theileria orientalis Ikeda genotype is an emerging cattle disease in the US. Since 2017, when T. orientalis Ikeda was discovered in beef cattle in two counties in Virginia, cattle infections have risen to include ~67% of Virginia counties and 14 states. Consistent with New Zealand studies, many infected herds in Virginia were >90% positive upon initial testing without overt evidence of infection. Central bull tests present a unique opportunity to study the effects of T. orientalis Ikeda infections, as bulls from multiple source herds are consolidated. The objective of this study was to determine if infection with T. orientalis Ikeda affected the average daily gain (ADG), adjusted yearling weight (AYW) and breeding soundness of bulls at two test stations in Virginia over a period of years.

Materials and methods

The bulls were fed and housed similarly to compare their growth performance and breeding soundness. For T. orientalis Ikeda testing, DNA was extracted from whole blood for quantitative polymerase chain reaction.

Results

The number of bulls infected with T. orientalis Ikeda at initial delivery to the stations increased significantly over the years studied. Multivariable linear regression models, using Angus bulls from Virginia test stations, indicated no significant effect on ADG or AYW in bulls that became test positive during the test or were positive for the duration, compared to Angus bulls that were negative for the duration. At LOC A, the odds of passing a breeding soundness exam (BSE) were not significantly different for bulls that turned positive during the test or were positive for the duration, compared to bulls that were negative for the duration of the test. At LOC B, bulls that became positive during the test were 2.4 times more likely (95% CI: 1.165-4.995, p = 0.016) to pass their BSE compared to bulls that remained negative throughout the test.

Discussion

We do not suppose that an obscured infection of T. orientalis Ikeda is protective for bulls to pass a BSE. However, this study demonstrates an obscured infection of T. orientalis Ikeda does not negatively affect weight gain or achievement of a satisfactory BSE rating at the central bull test stations in Virginia.

Satisfactory breeding potential is transiently eliminated in beef bulls with clinical anaplasmosis

BACKGROUND

Natural service breeding is common in U.S. cow-calf operations. Diseases impacting bull reproductive performance have significant economic consequences for producers. Anaplasmosis may be an underappreciated cause of poor reproductive performance in bulls. The primary systemic effects of bovine anaplasmosis including anemia, fever, and weight loss, can all result in unsatisfactory reproductive performance. The objective of this pilot study was to evaluate breeding soundness examination (BSE) outcomes and clinical changes in bulls during and upon resolution of clinical anaplasmosis. Anaplasma marginale-challenged bulls were observed for clinical disease and infection progression and changes in breeding soundness compared to uninfected control bulls for 16 weeks.

RESULTS

All Anaplasma marginale-challenged bulls were PCR-positive, seropositive, and showed clinical signs by 3-, 17-, and 24-days post-challenge, respectively. Clinical signs of anaplasmosis included pallor, icterus, fever (≥ 40.2 °C), and weight loss. Acute anemia was observed in all challenged bulls with PCV nadirs ≤ 18% and peak percent parasitized erythrocyte ≥ 50%. Decreased scrotal circumference and poor semen quality (e.g., increased percentage of abnormal spermatozoa, decreased progressively motile sperm), were initially observed within days after onset of clinical anaplasmosis signs and continued weeks beyond disease resolution. Control bulls remained negative for A. marginale.

CONCLUSION

This pilot study demonstrates that clinical anaplasmosis reduces breeding soundness in beef bulls. Anaplasmosis should be considered as a differential for bulls with decreased semen quality, especially within endemic areas. A 90 day or greater retest window is recommended for bulls of unsatisfactory breeding potential recently recovered from clinical anaplasmosis.

Theileria-free grazing of dairy heifers on grassland in Kyushu, Japan where T. orientalis was epidemic before a 7-year vacancy

This study aimed to produce a Theileria-free grazing system for Holstein heifers reared on a dairy farm in the Hita area, Kyushu, Japan. In the grazing area, spreading of T. orientalis infection was confirmed in 2009. To eradicate the T. orientalis infection, four measures were conducted: 1) 7-year deferred grazing; 2) grazing only T. orientalis-uninfected heifers; 3) anemia check by red blood cell parameters at least once per month; and 4) protecting heifers from blood-sucking T. orientalis-infected ticks. Grazing was restarted in 2017 in the same area and continued to 2021. During last 2 years of pasturing (2020–2021) all of the 129 heifers were confirmed to be T. orientalis-free. In summary, it is possible to establish a T. orientalis-free grazing system by conducting appropriate measures.

Review of the New Zealand Theileria orientalis Ikeda Type Epidemic and Epidemiological Research since 2012

This article sets out to document and summarise the New Zealand epidemic and the epidemiological research conducted on the epizootic of bovine anaemia associated with Theileria orientalis Ikeda type infection, which began in New Zealand in August 2012. As New Zealand has no other pathogenic tick-borne cattle haemoparasites, the effects of the T. orientalis Ikeda type infection observed in affected herds and individual animals were not confounded by other concurrent haemoparasite infections, as was possibly the case in other countries. This has resulted in an unbiased perspective of a new disease. In addition, as both New Zealand’s beef and dairy cattle systems are seasonally based, this has led to a different epidemiological presentation than that reported by almost all other affected countries. Having verified the establishment of a new disease and identified the associated pathogen, the remaining key requirements of an epidemiological investigation, for a disease affecting production animals, are to describe how the disease spreads, describe the likely impacts of that disease at the individual and herd level and explore methods of disease control or mitigation.

Effects of Theileria orientalis Infection on Health Status and Productivity of Dairy Cows Reared inside Barns

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.

A large-scale survey of Theileria orientalis infection in grazing dairy heifers in Kyushu, Japan

The objective of the present study was to investigate the prevalence of Theileria orientalis infection and the influence of this disease on dairy grazing heifers in Kyushu by monitoring red blood cell (RBC) indexes, and to evaluate the efficacy of diminazene diaceturate treatment of T. orientalis-infected animals. A monthly epidemiological survey was conducted for Holstein heifers, which were reared from 10 to 16 months of age on a large commercial dairy farm and grazed on eight independent grasslands from April to November, 2009. During the survey, a total of 2,803 blood samples were collected from the 891 grazing heifers, in which the prevalence of T. orientalis infection was 52.4%. Compared with the heifers before infection, heifers with high parasitemia (more than 100 parasites per 10⁴ RBC) had significantly decreased RBC indexes, such as RBC count, hemoglobin concentration, and hematocrit (P<0.05), whereas heifers with low parasitemia (less than 100 parasites per 10⁴ RBC) had similar RBC indexes as those before infection. Treatment with diminazene diaceturate had lower efficacy in heifers with high parasitemia than those with low parasitemia (40.7% and 73.2% became negative, respectively, P<0.05). In summary, T. orientalis infection is a potentially serious problem in Kyushu, and it is important to routinely implement control programs for heifers that are grazed on grasslands in this region.