Temporal patterns of bovine leukemia virus infection in dairy herds in Atlantic Canada

Objective

The primary objective was to determine the youngest age group where bovine leukemia virus (BLV)-infected dairy animals were identified. The secondary objective was to investigate associations between age-specific management practices and BLV infection status of different age groups of dairy calves and heifers.

Procedure

For enrolled herds, BLV status was determined using blood samples from pre-weaned calves, weaned calves, and breeding-age heifers; and bulk tank milk from the adult herd. A questionnaire investigating age-specific management factors was administered for each herd. Ordinal logistic regression was performed to identify management factors associated with the youngest age range in which BLV was identified.

Results

Fifty-three dairy herds from the 4 provinces in Atlantic Canada were enrolled. Bovine leukemia virus was most commonly earliest identified in pre-weaned heifers (18 herds, 32.1%) and the adult herd (18 herds, 32.1%). Ordinal logistic regression revealed that BLV was first identified in older age groups more often than in younger age groups when herds regrouped weaned heifers at least once, when fly control was used for breeding-age heifers, when herds practiced foot trimming on breeding-age heifers, and when bred heifers were brought in.

Conclusion

Producers can use results to identify the youngest age group(s) in which BLV is identified and to tailor management strategies to prevent new infections.

Listeria monocytogenes cholangiohepatitis in a lactating Holstein cow

OBJECTIVE

To describe a unique presentation of systemic Listeria monocytogenes infection in a lactating adult Holstein cow.

ANIMAL

3-year-old second-parity female Holstein, 200 days in milk.

CLINICAL PRESENTATION, PROGRESSION, AND PROCEDURES

A 3-year-old Holstein dairy cow was presented for decreased appetite, decreased milk production, and pyrexia. Blood work displayed marked abnormalities in liver-associated parameters. A diagnosis of L monocytogenes cholangiohepatitis was made following liver biopsy, histopathology, and bacterial culture.

TREATMENT AND OUTCOME

The cow was treated with systemic antimicrobial and antipyretic therapy. The cow was discharged to continue treatment on farm, and at time of last communication with the owner, the cow was doing very well, with full resolution of clinical signs.

CLINICAL RELEVANCE

This case report describes a novel presentation of L monocytogenes infection in an adult bovine. L monocytogenes cholangiohepatitis should be considered a rare differential diagnosis in cattle presenting with evidence of pyrexia and liver disease.

Retrospective review of atrial fibrillation in Standardbred racehorses at a tertiary care facility in Atlantic Canada

Atrial fibrillation (AF) is the most clinically relevant cardiac arrhythmia identified in the Standardbred racehorse. However, there is limited literature regarding athletic ability in Standardbred racehorses following AF conversion. To investigate this issue, the objectives of this review were to: i) determine the success rate in using quinidine sulphate to treat AF in a population of hospitalized equine patients in Atlantic Canada between January 2008 and December 2019; and ii) measure return to athletic ability (using racetrack earnings and top-3 finishes) following cardioversion with quinidine sulphate in a population of Standardbred racehorses. Overall, 73% (16/22) of AF instances in this study were successfully treated with enteral quinidine sulphate. No significant difference was detected in racetrack earnings or number of top-3 finishes for each horse that raced at least 5 times pre- and post-conversion. Key clinical message: To the authors' knowledge, this is the first published review to assess the athletic ability of Standardbred racehorses following cardioversion with enteral quinidine sulphate. Based on the current information, it does not appear that treatment of AF with quinidine sulphate affects future athletic performance in horses that achieved cardioversion.

Development of a predictive model for bovine leukemia virus proviral load

Background

There is currently no commercially available method in Canada to identify bovine leukemia virus (BLV)‐positive cows with high proviral load (PVL).

Objectives

First, develop a model to predict PVL using common, commercially available, cost‐effective diagnostic tests. Second, investigate the relationship between lymphocyte count and PVL in BLV‐positive cows.

Animals

A total of 339 BLV‐positive and 62 BLV‐seronegative cows on 15 dairy farms.

Methods

Cross‐sectional study. Blood and milk samples were collected from all lactating BLV‐positive cows on each farm and 5 to 10 BLV‐seronegative cows depending on herd size. Blood and milk samples were tested for anti‐BLV antibodies using enzyme‐linked immunosorbent assay (ELISA). Complete blood counts were performed on blood samples, and standard components analyses were obtained for milk samples. Proviral load was determined by quantitative polymerase chain reaction for each cow.

Results

The inverse of lymphocyte count, the square of the inverse of lymphocyte count, and milk ELISA percent positivity were positively associated with increasing PVL in BLV‐positive cows. For BLV‐positive cows, lymphocyte count >5.2 × 10⁹/L predicted a high PVL (BLV:Bovine DNA of >1 in blood) with a sensitivity of 92.4% and a specificity of 79.8%. For BLV‐positive cows, white blood cell count >10.8 × 10⁹/L predicted a high PVL, with a sensitivity of 85.5% and a specificity of 83.6%.

Conclusions and Clinical Importance

Based on these results, producers can implement commonly available diagnostic tests to identify cows with high probability of having high PVL, which may help in designing effective disease control strategies for BLV‐positive herds.

Development and implementation of a risk assessment and management program for enzootic bovine leukosis in Atlantic Canada

Over the past 30 yr, the prevalence of bovine leukemia virus (BLV) infection has increased in North America, including Atlantic Canada, at both the herd and individual cow levels. This has occurred despite increased awareness of the disease and its deleterious effects and despite implementation of management practices aimed at reducing disease transmission. Our objectives were to identify risk factors associated with the within-herd prevalence of BLV-infected cows by using a risk assessment and management program workbook, as well as to determine the current level of BLV prevalence in the Atlantic Canada region. We hypothesized that previously established risk factors, including management practices associated with calf rearing and fly control, would affect within-herd BLV prevalence. Bulk tank milk (BTM) samples were collected in January and April of 2016 and again during the same months in 2017 and 2018 from all dairy farms shipping milk in the region. Samples were tested with ELISA for levels of anti-BLV antibodies to estimate within-herd prevalence. Regional BLV prevalence at the herd level was 88.39% of dairy herds infected in 2016 and 89.30% in 2018. All dairy farms shipping milk and who had BTM samples collected in 2017 (n = 605) were eligible to participate in the risk assessment and management program questionnaire (RAMP), which was developed and distributed to all bovine veterinarians in Atlantic Canada. One hundred and six RAMP were returned, with representation from all 4 provinces. The RAMP results were combined with the mean BTM ELISA results, and univariable logistic regression followed by multivariable logistic regression was performed to investigate the association between RAMP risk factors and the estimated within-herd BLV prevalence. Factors in the multivariable model significantly associated with the odds of a herd being classified as >25% estimated within-herd prevalence included history of diagnosis of clinical BLV and calves receiving colostrum from cows with unknown BLV status. Differences in within-herd prevalence were not associated with hypodermic needle and injection practices, rectal sleeve practices, or using bulls for natural breeding, based on these 106 dairy farms.

Spontaneous resolution of bilateral congenital patellar luxation in an alpaca cria

An 8-day-old alpaca was presented for suspected meconium impaction and abnormal gait and posture. Physical examination revealed bilateral medial patellar luxation. In previous reports, medical treatment of patellar luxation in crias has been associated with a poor to grave prognosis; here we report a case of successful resolution.

Investigation of within- and between-herd variability of bovine leukaemia virus bulk tank milk antibody levels over different sampling intervals in the Canadian Maritimes

Bulk tank milk (BTM) samples are used to determine the infection status and estimate dairy herd prevalence for bovine leukaemia virus (BLV) using an antibody ELISA assay. BLV ELISA variability between samples from the same herd or from different herds has not been investigated over long time periods. The main objective of this study was to determine the within-herd and between-herd variability of a BTM BLV ELISA assay over 1-month, 3-month, and 3-year sampling intervals. All of the Canadian Maritime region dairy herds (n = 523) that were active in 2013 and 2016 were included (83.9% and 86.9% of total herds in 2013 and 2016, respectively). BLV antibody levels were measured in three BTM samples collected at 1-month intervals in early 2013 as well as two BTM samples collected over a 3-month interval in early 2016. Random-effects models, with fixed effects for sample replicate and province and random effects for herd, were used to estimate the variability between BTM samples from the same herd and between herds for 1-month, 3-month, and 3-year sampling intervals. The majority of variability of BTM BLV ELISA results was seen between herds (1-month, 6.792 ± 0.533; 3-month, 7.806 ± 0.652; 3-year, 6.222 ± 0.528). Unexplained variance between samples from the same herd, on square-root scale, was greatest for the 3-year (0.976 ± 0.104), followed by the 1-month (0.611 ± 0.035) then the 3-month (0.557 ± 0.071) intervals. Variability of BTM antibody levels within the same herd was present but was much smaller than the variability between herds, and was greatest for the 3-year sampling interval. The 3-month sampling interval resulted in the least variability and is appropriate to use for estimating the baseline level of within-herd prevalence for BLV control programs. Knowledge of the baseline variability and within-herd prevalence can help to determine effectiveness of control programs when BTM sampling is repeated at longer intervals.

Enhancing self-care, adjustment and engagement through mobile phones in youth with HIV

AIM

To evaluate the effectiveness of mobile phones in enhancing self-care, adjustment and engagement in non-disclosed youth living with HIV.

BACKGROUND

Youth aged 15-24 years represent 42% of new HIV infections globally. Youth who are aware of their HIV status generally do not disclose it or utilize HIV-related facilities because of fear of stigma. They rely on the Internet for health maintenance information and access formal care only when immune-compromised and in crisis.

INTRODUCTION

This study shows how non-disclosed youth living with HIV can be reached and engaged for self-management and adjustment through mobile phone.

STUDY DESIGN

One-group pre-test/post-test experimental design was used.

METHODS

Mobile phones were used to give information, motivation and counselling to 19 purposively recruited non-disclosed youth with HIV in Calabar, South-South Nigeria. Psychological adjustment scale, modified self-care capacity scale and patient activation measure were used to collect data. Data were analysed using PASW 18.0.

RESULTS

Scores on self-care capacity, psychological adjustment and engagement increased significantly at post-test. HIV-related visits to health facilities did not improve significantly even at 6 months. Participants still preferred to consult healthcare providers for counselling through mobile phone.

DISCUSSION

Mobile phone-based interventions are low cost, convenient, ensure privacy and are suitable for youth. Such remote health counselling enhances self-management and positive living.

CONCLUSION AND IMPLICATIONS FOR HEALTH POLICY

Mobile phones enhance self-care, psychological adjustment and engagement in non-disclosed youth living with HIV, and can be used to increase care coverage. Findings underline the importance of policies to increase access by locating, counselling and engaging HIV-infected youth in care.

Redundant contribution of a Transient Receptor Potential cation channel Member 1 exon 11 single nucleotide polymorphism to equine congenital stationary night blindness

BACKGROUND

Congenital stationary night-blindness (CSNB) is a recessive autosomal defect in low-light vision in Appaloosa and other horse breeds. This condition has been mapped by linkage analysis to a gene coding for the Transient Receptor Potential cation channel Member 1 (TRPM1). TRPM1 is normally expressed in the ON-bipolar cells of the inner nuclear layer of the retina. Down-regulation of TRPM1 expression in CSNB results from a transposon-like insertion in intron 1 of the TRPM1 gene. Stop transcription signals in this transposon significantly reduce TRPM1 primary transcript levels in CSNB horses. This study describes additional contributions by a second mutation of the TRPM1 gene, the ECA1 108,249,293 C > T SNP, to down-regulation of transcription of the TRPM1 gene in night-blind horses. This TRPM1 SNP introduces a consensus binding site for neuro-oncological ventral antigen 1 (Nova-1) protein in the primary transcript. Nova-1 binding disrupts normal splicing signals, producing unstable, non-functional mRNA transcripts.

RESULTS

Retinal bipolar cells express both TRPM1 and Nova-1 proteins. In vitro addition of Nova-1 protein retards electrophoretic migration of TRPM1 RNA containing the ECA1 108,249,293 C > T SNP. Up-regulating Nova-1 expression in primary cultures of choroidal melanocytes carrying the intron 11 SNP caused an average log 2-fold reduction of ~6 (64-fold) of TRPM1 mRNA expression.

CONCLUSIONS

These finding suggest that the equine TRPM1 SNP can act independently to reduce survival of TRPM1 mRNA escaping the intron 1 transcriptional stop signals in CSNB horses. Coexistence and co-inheritance of two independent TRPM1 mutations across 1000 equine generations suggests a selective advantage for the apparently deleterious CSNB trait.