Development of LIME-NZ: a generic tool for prompt estimation of economic impacts of disease for New Zealand livestock

AIMS

To develop a simple and robust generic tool to measure the impacts of livestock diseases on New Zealand dairy, beef and sheep farms using enterprise gross margin models.

METHODS

The most recent (2018-2020) livestock production benchmarking data was extracted from industry-led economic surveys. Gross margin models were built for each enterprise type, accounting for 11 dairy farm types and 16 farm types for beef and sheep. Disease parameters, including changes in mortality, reproduction performance, milk yield, price of animals and culling rate, as well as additional expenses for veterinary intervention, were applied to the infected compartment of the herd/flock using the assumed annual within-herd disease incidence. Farm-level disease impacts were estimated as the difference in annual profit between the baseline and infected farm. The baseline gross margin models were validated against the industry data. The disease impact models were validated using a recently published study on bovine viral diarrhoea (BVD). The impact assessment tool, LIME-NZ, was developed using the statistical software R and implemented in the web-based R package Shiny. The input parameters can be varied interactively to obtain a range of disease impacts for uncertain disease parameters.

RESULTS

The baseline gross margin models demonstrated reasonable accuracy with a mean percentage error of <14% when compared with the industry reports. The estimated annual impacts of BVD were comparable to those reported in the BVD study, NZ$38.5-140.4 thousand and $0.9-32.6 thousand per farm per year for dairy and beef enterprises, respectively.

CONCLUSIONS

LIME-NZ can be used to rapidly obtain the likely economic impacts of diseases that are endemic, recently introduced or at increased risk of introduction in the New Zealand context. This will aid communication and decision-making among government agencies and the livestock industry, including veterinarians and livestock producers, about the management of diseases, until refined information becomes available to improve decision-making.

Identification of Genomic Instability in Cows Infected with BVD Virus

An important factor for dairy cattle farmers is the profitability of cattle rearing, which is influenced by the animals' health and reproductive parameters, as well as their genomic stability and integrity. Bovine viral diarrhea (BVD) negatively affects the health of dairy cattle and causes reproductive problems. The aim of the study was to identify genomic instability in cows with reproductive disorders following infection with the BVD virus. The material for analysis was peripheral blood from Holstein-Friesian cows with reproductive problems, which had tested positive for BVD, and from healthy cows with no reproductive problems, which had tested negative for BVD. Three cytogenetic tests were used: the sister chromatid exchange assay, fragile sites assay, and comet assay. Statistically significant differences were noted between the groups and between the individual cows in the average frequency of damage. The assays were good biomarkers of genomic stability and enabled the identification of individuals with an increased frequency of damage to genetic material that posed a negative impact on their health. The assays can be used to prevent disease during its course and evaluate the genetic resistance of animals. This is especially important for the breeder, both for economic and breeding reasons. Of the three assays, the comet assay proved to be the most sensitive for identifying DNA damage in the animals.

Dynamic changes of gut fungal community in horse at different health states

Accumulating studies indicated that gut microbial changes played key roles in the progression of multiple diseases, which seriously threaten the host health. Gut microbial dysbiosis is closely associated with the development of diarrhea, but gut microbial composition and variability in diarrheic horses have not been well characterized. Here, we investigated gut fungal compositions and changes in healthy and diarrheic horses using amplicon sequencing. Results indicated that the alpha and beta diversities of gut fungal community in diarrheal horses changed significantly, accompanied by distinct changes in taxonomic compositions. The types of main fungal phyla (Neocallimastigomycota, Ascomycota, and Basidiomycota) in healthy and diarrheal horses were same but different in relative abundances. However, the species and abundances of dominant fungal genera in diarrheal horses changed significantly compared with healthy horses. Results of Metastats analysis indicated that all differential fungal phyla (Blastocladiomycota, Kickxellomycota, Rozellomycota, Ascomycota, Basidiomycota, Chytridiomycota, Mortierellomycota, Neocallimastigomycota, Glomeromycota, and Olpidiomycota) showed a decreasing trend during diarrhea. Moreover, a total of 175 differential fungal genera were identified for the gut fungal community between healthy and diarrheal horses, where 4 fungal genera increased significantly, 171 bacterial genera decreased dramatically during diarrhea. Among these decreased bacteria, 74 fungal genera even completely disappeared from the intestine. Moreover, this is the first comparative analysis of equine gut fungal community in different health states, which is beneficial to understand the important role of gut fungal community in equine health.

Characterization of gut microbiota dysbiosis of diarrheic adult yaks through 16S rRNA gene sequences

The ruminant gut microbial community has a strong impact on host health and can be altered during diarrhea disease. As an indigenous breed of the Tibetan Plateau, domestic yak displays a high diarrhea rate, but little research has been done to characterize the bacterial microbial structure in diarrheic yaks. In the present study, a total of 30 adult yaks, assigned to diarrhea (case, N = 15) and healthy (control, N = 15) groups, were subjected to gut microbiota profiling using the V3–V4 regions of the 16S rRNA gene. The results showed that the gut microbiome of the case group had a significant decrease in alpha diversity. Additionally, differences in beta diversity were consistently observed for the case and control groups, indicating that the microbial community structure was changed due to diarrhea. Bacterial taxonomic analysis indicated that the Bacteroidetes, Firmicutes, and Proteobacteria were the three most dominant phyla in both groups but different in relative abundance. Especially, the proportion of Proteobacteria in the case group was increased as compared with the control group, whereas Spirochaetota and Firmicutes were significantly decreased. At the genus level, the relative abundance of Escherichia-Shigella and Prevotellaceae_UCG-003 were dramatically increased, whereas that of Treponema, p-2534-18B5_gut_group, and Prevotellaceae_UCG-001 were observably decreased with the effect of diarrhea. Furthermore, based on our linear discriminant analysis (LDA) effect size (LEfSe) results, Alistipes, Solibacillus, Bacteroides, Prevotellaceae_UCG_003, and Bacillus were significantly enriched in the case group, while the other five genera, such as Alloprevotella, RF39, Muribaculaceae, Treponema, and Enterococcus, were the most preponderant in the control group. In conclusion, alterations in gut microbiota community composition were associated with yak diarrhea, differentially represented bacterial species enriched in case animals providing a theoretical basis for establishing a prevention and treatment system for yak diarrhea.

Seroprevalence of Seven Reproductive Diseases in Beef and Dairy Cows from Three Provinces in Indonesia

Bovine reproductive diseases are endemic in Indonesia, but comprehensive information about their infectious causes is not available. Therefore, our aim for this study was to detect several infectious agents that cause reproductive diseases in Indonesian beef and dairy cows. A total of 152 cow serum samples collected by Faculty of Veterinary Medicine of Brawijaya University and Veterinary Disease Investigation Centre as a part of the mandatory and regularly surveillance system from three provinces during 2019–2020 were used. The samples were then sent to Indonesian Research Centre for Veterinary Science (IRCVS) for further detection of seven reproductive diseases by enzyme-linked immunosorbent assay (ELISA). Seven reproductive diseases to be tested in parallel are neosporosis, chlamydiosis, brucellosis, Q fever, bovine viral diarrhea (BVD), infectious bovine rhinotracheitis (IBR), and BHV-4 infection. The dominant reproductive diseases in Indonesian cows were BVD (45.69%), chlamydiosis (31.58%), IBR (20.53%), neosporosis (11.84%), and BHV-4 infection (10.53%). The seroprevalence of IBR, BHV-4 infection, neosporosis, and brucellosis varied significantly (P < 0.05) between dairy and beef cattle. The most dominant reproductive diseases in aborted cows were chlamydiosis (45%), BVD (41%), and neosporosis (10%). The conclusion drawn from this study is that the dominant reproductive diseases in Indonesian cows are BVD, chlamydiosis, IBR, neosporosis, and BHV-4 infection. Chlamydiosis, BVD, and neosporosis are common among aborted cow. Chlamydiosis, neosporosis, and BHV-4 infection should be included in the national priority list in Indonesia. Control and preventive measures should be focused on high-risk areas and animals like stray cat and dog.

Bovine viral diarrhea virus (BVDV) infection: Effect on reproductive performance and milk yield in dairy herds

The impact of an outbreak of bovine viral diarrhea (BVD) on reproductive performance and milk production was investigated in 28 Spanish dairy herds using an observational study design. Mean calving to conception interval (CCI), mean number of inseminations per conception (AI/P) and mean daily milk yield were recorded from herds affected by outbreaks. Infection was confirmed by evidence of viral transmission to young stock (heifers 9-24 months) and persistently infected animals, after previous BVD-free status. Fifteen herds did not use vaccines (G1) whereas the remaining 13 received modified live BVD virus (BVDV) vaccines (G2). In G1 herds, a significant increase in CCI (13.8 days; 95% CI, 0.4-27.3 days; P = 0.050) was observed during the BVD outbreak compared to the year before the outbreak. In G2 herds, there was a not a significant increase in CCI (3.0 days; 95% CI, -1.2-7.2 days; P = 0.558). Changes in AI/P between periods were not significant in any of the herds. In G1 herds, there was an increase of 0.09 units (P > 0.05) during the outbreak, whereas in G2 herds, AI/P decreased 0.08 units (P > 0.05). Compared to milk production in the year before the BVD outbreak, there was no significant change in G1 herds throughout the study period (P > 0.05), but there were significant increases in G2 herds over the study period (P1-P2, 1.4 kg/day increase, P = 0.019; P1-P3, 2.0 kg/day increase, P = 0.007). These results indicate that BVDV infection affected reproductive performance, which is critical in maintaining dairy herd profitability.

The effect of new bovine viral diarrhea virus introduction on somatic cell count, calving interval, culling, and calf mortality of dairy herds in the Dutch bovine viral diarrhea virus-free program

Bovine viral diarrhea virus (BVDV) infection has a major effect on the health of cows and consequently on herd performance. Many countries have implemented control or eradication programs to mitigate BVDV infection and its negative effects. These negative effects of BVDV infection on dairy herds are well documented, but there is much less information about the effects of new introduction of BVDV on dairy herds already participating in a BVDV control program. The objective of our study was to investigate the effect of a new BVDV introduction in BVDV-free herds participating in the Dutch BVDV-free program on herd performance. Longitudinal herd-level surveillance data were combined with herd information data to create 4 unique data sets, including a monthly test-day somatic cell count (SCC) data set, annual calving interval (CIV) and culling risk (CR) data sets, and a quarterly calf mortality rate (CMR) data set. Each database contained 2 types of herds: herds that remained BVDV free during the whole study period (defined as free herds), and herds that lost their BVDV-free status during the study period (defined as breakdown herds). The date of losing the BVDV-free status was defined as breakdown date. To compare breakdown herds with free herds, a random breakdown date was artificially generated for free herds by simple random sampling from the distribution of the breakdown month of the breakdown herds. The SCC and CIV before and after a new introduction of BVDV were compared through linear mixed-effects models with a Gaussian distribution, and the CR and CMR were modeled using a negative binomial distribution in generalized linear mixed-effects models. The explanatory variables for all models included herd type, BVDV status, year, and a random herd effect. Herd size was included as an explanatory variable in the SCC, CIV, and CMR model. Season was included as an explanatory variable in the SCC and CMR model. Results showed that free herds have lower SCC, CR, CMR, and shorter CIV than the breakdown herds. Within the breakdown herds, the new BVDV introduction affected the SCC and CMR. In the year after BVDV introduction, the SCC was higher than that in the year before BVDV introduction, with a factor of 1.011 [2.5th to 97.5th percentile (95% PCTL): 1.002, 1.020]. Compared with the year before BVDV breakdown, the CMR in the year of breakdown and the year after breakdown was higher, with factors of 1.170 (95% PCTL: 1.120; 1.218) and 1.096 (95% PCTL: 1.048; 1.153), respectively. This study reveals that a new introduction of BVDV had a negative but on average relatively small effect on herd performance in herds participating in a BVDV control program.

Practices and opinions of New Zealand veterinarians regarding control of bovine viral diarrhoea

AIMS

To explore recommendations that New Zealand veterinarians make for diagnosing and managing bovine viral diarrhoea (BVD) in cattle herds under different clinical scenarios and their opinions towards potential barriers and opportunities for implementing BVD control programmes in New Zealand.

METHODS

A cross-sectional survey of registered veterinarians in New Zealand was conducted in 2019. Respondents were asked about the approaches they would use to manage BVD under different clinical scenarios as well as their opinions on national BVD control. A subset of veterinarians completed a more in-depth survey providing additional free-text responses on a range of different BVD topics. Descriptive statistics were provided for all quantitative study variables and the free-text responses were also analysed to generate further insights into veterinarians' perceptions towards BVD management.

RESULTS

The cross-sectional survey was completed by 101 of an estimated 870 (11.6%) cattle veterinarians. Thirty-five veterinarians completed the in-depth survey. There was wide variation in the BVD diagnostic testing and vaccination protocols that respondents recommended under different clinical scenarios. Annual bulk milk BVD testing was perceived as a valuable tool for initiating BVD discussions with dairy farmers. Respondents indicated that beef farmers were more difficult to engage in BVD control largely due to the logistical challenges of yarding cattle at the appropriate times to implement interventions, with many farmers only contacting veterinarians after experiencing a BVD outbreak Most respondents (91/101; 90%) believed it was possible to eradicate BVD from New Zealand, but cited lack of farmer awareness and poor compliance with management recommendations as significant barriers. The measure with the most support for inclusion in a compulsory national eradication programme was requiring farmers to declare the status of their animals prior to sale while the least supported measure was requiring farmers to double fence boundaries to prevent nose-to-nose contact with neighbouring stock. Although respondents highlighted the need for farmers and industry to support any national eradication programme in order for it to be successful, there was also recognition that veterinarians could be more pro-active in engaging with farmers particularly in discussions around the economics of BVD.

CONCLUSIONS AND CLINICAL RELEVANCE

While the survey respondents appeared to be highly supportive of BVD control, it was perceived that financial and logistical barriers existed that could impede farmer engagement. Further extension efforts may be needed to ensure that veterinarians are presenting clear and consistent recommendations about BVD management to farmers.Abbreviations: BVD: Bovine viral diarrhoea; NAIT: National Animal Identification and Tracing System; PI: Persistently infected.

Detection of Pestivirus in small ruminants in Central Java, Indonesia

Background and Aim:

Globally, pestiviruses are among the most economically important viral pathogens of livestock. The genus Pestivirus comprises four species, including bovine viral diarrhea virus type 1 and 2 (BVDV-1 and BVDV-2), which infect cattle, border disease virus and classical swine fever virus which infect small ruminants and pigs, respectively. Accumulating evidence suggests that pestiviruses are no longer species-specific, creating new challenges for disease control. In Indonesia, investigations related to pestiviruses remain focused on cattle as the primary host and no research has been conducted on small ruminants (sheep and goats). Therefore, the present study aimed to study the possible occurrence of pestivirus (BVDV or BVD) infections in small ruminants in Indonesia, particularly in Central Java.

Materials and Methods:

We used 46 blood samples consisting of 26 sheep’s blood and 20 goat’s blood. Samples were selected from 247 small ruminant blood collected between July and October 2020 in Central Java, Indonesia, which met the following criteria: Female, local species, approximately 1-2 years old, never been pregnant, raised in the backyard, and had no close contact with cattle in either shelter or grazing area. We tested plasma samples from sheep and goats using competitive antibody enzyme-linked immunosorbent assay to detect specific antibodies against pestivirus followed by reverse transcription-polymerase chain reaction (RT-PCR) analysis for all positive samples to differentiate the species of pestivirus.

Results:

Two of the 20 samples collected from goats were positive for pestivirus at the serological and molecular levels, whereas 2 of 26 samples collected from sheep were doubtful but tested negative by RT-PCR. The genotyping test results obtained using nested PCR revealed that the positive samples collected from goats had a BVDV-1 genotype.

Conclusion:

The results of the present study demonstrated that BVDV-1 can infect species other than bovines, in Central Java, Indonesia. Further studies involving a larger number of samples are required to: (1) Determine the actual seroprevalence of pestiviruses in small ruminants and (2) Determine the potency of small ruminants as reservoirs for pestiviruses, both of which are important for the identification of the appropriate control program for pestiviruses in Indonesia.

Microbiome Analysis Reveals the Attenuation Effect of Lactobacillus From Yaks on Diarrhea via Modulation of Gut Microbiota

Domestic yaks (Bos grunniens) are indigenous to the Tibetan Plateau and display a high diarrhea rate due to poor habitat and husbandry conditions. Lactobacillus has been shown to exert beneficial effects as antimicrobial, growth promotion, and gut microbiota in humans and/or murine models, but the relevant data regarding Lactobacillus isolated from yaks was unavailable. Therefore, this study aimed to investigate the effects of Lactobacillus from yaks on the intestinal microbial community in a mouse model and determine whether Lactobacillus supplementation contributed in alleviating diarrhea by modulating gut microbiota. A total of 12 ileac samples from four groups were collected for 16S rRNA gene amplicon sequencing of V3-V4 region. Results revealed that although Lactobacillus supplementation did not change the diversity of gut microbiota in mice, the proportion of some intestinal microbiota significantly changed. Specifically, the proportion of Lactobacillus and Sphingomonas in the Lactobacillus treated-group (L-group) were increased as compared to control group (C-group), whereas Pantoea, Cutibacterium, Glutamicibacter, Turicibacter, Globicatella, Microbacterium, Facklamia, unidentified_Corynebacteriaceae, Brachybacterium, and Staphylococcus were significantly decreased in the L-group. In contrast, Escherichia coli (E. coli) infection significantly decreased the proportion of beneficial bacteria such as Globicatella, Acinetobacter, Aerococcus, and Comamonas, while loads of pathogenic bacteria significantly increased including Roseburia and Megasphaera. Interestingly, Lactobacillus administration could ameliorate the microbial community structure of E. coli-induced diarrheal mice by reducing the relative abundance of pathogenic bacteria such as Paenibacillus, Aerococcus, Comamonas, Acinetobacter, Corynebacterium, Facklamia, and Globicatella. Results in this study revealed that Lactobacillus supplementation not only improved the gut microbiota but also alleviated diarrhea in mice, which may be mediated by modulating the composition and function of gut microbiota. Moreover, this study is expected to provide a new theoretical basis for the establishment of a preventive and treatment system for diarrhea in yaks.

Temporal trends in bulk tank milk antibody ELISA and PCR test results for bovine viral diarrhoea in New Zealand pastoral dairy herds

Aims: To describe temporal trends in bulk milk antibody ELISA and PCR testing for bovine viral diarrhoea (BVD) in New Zealand pastoral dairy herds and to assess the use of historical accession data to predict herd-level BVD incursions. Methods: Data on all diagnostic testing of bulk milk for BVD performed by the Livestock Improvement Corporation (Hamilton, NZ) over eight lactation seasons from 1 June 2010 to 31 May 2018 were analysed. This included anonymised herd identification, geographic location, herd size, sample collection date, sample to positive (S/P) ratio for antibody ELISA results, and cycle threshold values for PCR detecting viral RNA. Multivariable logistic regression was used to explore the relationship between historical accession data and the risk of herds having at least one positive bulk milk PCR test result in the 2017 season. Results: There were 156,034 bulk milk BVD diagnostic testing accessions for 10,495 uniquely identified dairy herds over the 8-season period. The prevalence of tested herds with at least one positive bulk milk PCR test result decreased from 14.6% (407/2,786) in the 2010 season to 5.6% (355/6,309) in the 2017 season with similarly marked declines in S/P ratios. In the 2017 season, 2,961/6,309 (46.9%) herds had S/P ratios greater than the 0.75 cut-off value indicating recent or active BVD virus transmission within the herd while 1,422/6,309 (22.5%) herds were classified as having negative or low S/P ratios. Herds that cleared BVD from the milking herd experienced a mean decline in S/P ratio of 0.11 units per year (min 0.05; max 0.18). In the multivariable analysis, the overall incidence risk of herds experiencing a BVD incursion in the 2017 season was 3.8% (146/3,848) and there were three significant predictors in the final model: herd size, PCR status in the 2014 season, and change in S/P ratio between the 2014 and 2015 seasons. The area under the receiver operating curve for the final model was 0.695 indicating poor discrimination. Conclusions and clinical relevance: The prevalence of dairy herds in New Zealand with positive bulk milk PCR test results and high S/P ratios has decreased over time, suggesting fewer herds are actively infected with BVD and that herd immunity may also be declining. Although monitoring trends in bulk milk test results provides useful information on changes in individual herd status, it is difficult to accurately predict when new incursions will occur and farmers should continue to maintain good biosecurity.

Comparison of milk production of dairy cows vaccinated with a live double deleted BVDV vaccine and non-vaccinated dairy cows cohabitating in commercial herds endemically infected with BVD virus

Daily milk production and reproductive performance of cows vaccinated with a live double-deleted Bovine Viral Diarrhoea Virus (BVDV) vaccine were compared to those of non-vaccinated cows, cohabitating in endemic BVDV herds. All animals in the treatment group were vaccinated on study day 0 irrespective of lactation or gestation status, while control animals did not receive any treatment. 1463 animals were enrolled in the study from four different farms in three different countries (UK, Italy, France). Endemic presence of BVDV in study herds was demonstrated by the detection of BVDV in the bulk tank milk, and seroconversion was evaluated at the beginning of the study. For individual animals, the day of calving was taken to be the start of lactation for the calculation of days in milk (DIM). The standard lactation period of 305 days was divided into three periods: early lactation (EL, from DIM 8 to DIM 102), mid lactation (ML, from DIM 103 to DIM 204 and late lactation (LL, from DIM 205 to DIM 305). For each farm and each lactation period, a mixed model statistical analysis was performed with daily milk production as response, and group, day as well as the interaction between those two factors as fixed factors. Chi-square test was used to compare abortion rate and prolonged inter-oestrous interval rate between treatment and control groups. A significant increase in milk production in the vaccinated group was observed in farms 1 (1.023 L/day) and 3 (0.611 L/day) during EL (p<0.001) and in farm 2 (1.799 L/day) during ML (P<0.001). In addition, at farm 2, vaccinated cows produced more milk than non-vaccinated cows starting from 80 DIM. No differences were found between groups in abortion rates or prolonged inter-oestrous interval rates. Data demonstrate that cows in herds endemically infected with BVDV and vaccinated with live double-deleted BVDV vaccine produce more milk; the difference in milk production occurs during early lactation.

Selection for Favorable Health Traits: A Potential Approach to Cope with Diseases in Farm Animals

Disease is a global problem for animal farming industries causing tremendous economic losses (>USD 220 billion over the last decade) and serious animal welfare issues. The limitations and deficiencies of current non-selection disease control methods (e.g., vaccination, treatment, eradication strategy, genome editing, and probiotics) make it difficult to effectively, economically, and permanently eliminate the adverse influences of disease in the farm animals. These limitations and deficiencies drive animal breeders to be more concerned and committed to dealing with health problems in farm animals by selecting animals with favorable health traits. Both genetic selection and genomic selection contribute to improving the health of farm animals by selecting certain health traits (e.g., disease tolerance, disease resistance, and immune response), although both of them face some challenges. The objective of this review was to comprehensively review the potential of selecting health traits in coping with issues caused by diseases in farm animals. Within this review, we highlighted that selecting health traits can be applied as a method of disease control to help animal agriculture industries to cope with the adverse influences caused by diseases in farm animals. Certainly, the genetic/genomic selection solution cannot solve all the disease problems in farm animals. Therefore, management, vaccination, culling, medical treatment, and other measures must accompany selection solution to reduce the adverse impact of farm animal diseases on profitability and animal welfare.

Modelling the economics of bovine viral diarrhoea virus control in pastoral dairy and beef cattle herds

Bovine viral diarrhoea virus (BVDV) is a prevalent pathogen in the New Zealand cattle industries, yet few studies to date have evaluated the economics of BVDV in pastoral dairy and beef herds to help inform management decisions. To address this knowledge gap, we developed stochastic individual-based simulation models to represent the transmission dynamics of BVDV in typical spring-calving dairy and beef farms in New Zealand. The models conservatively estimated the direct losses due to a BVDV outbreak at NZ$ 22.22 and NZ$ 41.19 per mixed-age cow per year for a naïve dairy and beef farm, respectively, over a 5-year period. The greatest economic impacts for the dairy farm occurred when persistently infected replacement heifers joined the lactating cow group and caused transient infection of cows to drop in milk production, whereas the greatest impacts for the beef farm was through the loss of fattening stock for sale due to lowered pregnancy rates. Various combinations of diagnostic testing, vaccination, and biosecurity measures were then explored to evaluate the cost-efficiency of different strategies for controlling BVDV at the farm-level. Providing farmers with the estimates of economic impacts of BVDV in their herds may further encourage the uptake of control measures, but close collaboration with a veterinarian to determine the optimal strategy for their unique farm circumstances is still required.

Estimation of the burden of leptospirosis in New Zealand

BACKGROUND

Human leptospirosis mainly affects people in close occupational contact with domestic livestock and their products in New Zealand. The disease has an unquantified impact on both human health and animal production in the country. This study aimed to estimate the burden of leptospirosis in terms of disability-adjusted life years (DALYs) and cost associated with loss due to absence from work, treatment of disease, animal production loss and cost of vaccination.

METHODS

Previously published studies of abattoir workers farmers, and veterinarians, reporting annual risks of influenza-like illness attributable to Leptospira infection, were used to estimate the expected number of cases in a year. The cost of lost animal production was based on results of observational studies in beef cattle, sheep and deer conducted in New Zealand.

RESULTS

Expected median annual number of severe and mild cases of human leptospirosis was 2,025 (95% probability interval [95% PI] 1,138-3,422). Median annual DALYs were 0.42 (95% PI: 0.06-2.40) per 100,000 people for the entire population, and 15.82 (95% PI: 2.09-90.80) per 100,000 people working in at-risk occupations (i.e. abattoir workers, farmers and veterinarians). Human infection resulted in a median cost of 4.42 (95% PI: 2.04-8.62) million US dollars (USD) due to absence from work and disease treatment. Median production loss cost in beef cattle, sheep and deer was USD 7.92 (95% PI: 3.75-15.48) million, while median vaccination cost in cattle, (including dairy), sheep and deer was USD 6.15 (95% PI: 5.30-7.03) million. Total annual cost of leptospirosis plus vaccination was USD 18.80 (95% PI: 13.47-27.15) million, equivalent to USD 440,000 (95% PI: 320,000-640,000) per 100,000 people.

CONCLUSION

This study provides an estimate of the disease burden and cost of leptospirosis in New Zealand that could support occupational health authorities and livestock industries in assessing interventions for this disease.

Practices and opinions of New Zealand beef cattle farmers towards bovine viral diarrhoea control in relation to real and perceived herd serological status

Aims: To investigate the seroprevalence of infection with bovine viral diarrhoea (BVD) virus among 75 beef herds and seroconversion in cattle during early pregnancy, and to determine the practices and opinions of farmers towards BVD control and their association with real and perceived herd serological status.Methods: Blood samples were collected before mating in 75 beef herds across New Zealand from 15 unvaccinated heifers that had delivered their first calf that season. Serum samples were tested for BVD antibodies using ELISA individually, and after pooling samples for each farm. Animals that were antibody-negative were retested at either pregnancy diagnosis or weaning. Farmers were asked to complete a detailed survey about herd demographics, BVD testing and vaccination practices, and opinions towards national BVD control.Results: Based on the pooled serum antibody ELISA results, there were 28/75 (37%) negative herds, 15/75 (20%) suspect herds, and 32/75 (43%) positive herds. Of 1,117 animals sampled 729 (65.3%) tested negative for BVD virus antibodies; when retested, 47/589 (8.0%) animals from 13/55 (24%) herds had seroconverted. Among 71 famers providing survey responses 11 (15%) believed their herd was infected with BVD, 24 (34%) were unsure and 36 (51%) did not think their herd was infected. Only 19/71 (18%) farmers had performed any BVD testing within the past 5 years and 50/70 (71%) had not vaccinated any cattle for BVD. Support for national BVD eradication programme was strong in 51/71 (56%) respondents, but the biggest challenge to BVD control was considered to be famer compliance. Compared to farmers who did not think their herd was infected, more farmers who thought BVD was present in their herds had previously tested for BVD, would consider testing all replacement calves, and would support establishing a national BVD database; fewer would consider purchasing BVD tested or vaccinated cattle only.Conclusions and clinical relevance: Only 15% of the beef farmers in this study believed their herds were infected with BVD virus and few of them had undertaken BVD screening. Nevertheless many were supportive of implementing a national BVD control programme. It is likely that the lack of farmer awareness around BVD and the failure of farmers to recognise the potential impacts in their herds are hindering progress in controlling the disease in New Zealand. There are opportunities for New Zealand veterinarians to be more proactive in helping beef farmers explore BVD management options.

Assessing the use of diagnostic laboratory accession data to support national bovine viral diarrhoea control in New Zealand

Aims: To assess the suitability of using existing national diagnostic laboratory testing data to support national bovine viral diarrhoea (BVD) research, surveillance, and control in New Zealand. Methods: Data on laboratory accessions for BVD diagnostic testing in New Zealand from 1 January 2015 to 31 December 2017 were provided by four commercial veterinary diagnostic companies. The data were integrated into a single dataset containing the unique accession number, sample submission date, farm location (territorial authority level), test type (bulk milk antibody-ELISA, bulk milk PCR, serum antibody-ELISA, blood/serum/tissue antigen-ELISA, or blood/serum/tissue PCR), and test results. Estimates for the number of registered cattle farms in each territorial authority were generated from the National Animal Identification and Tracing database. Results were summarised for July 2015 to June 2016 and July 2016 to June 2017. Results: There was a total of 59,007 unique BVD diagnostic test accessions including 39,920 (67.6%) for bulk milk antibody-ELISA, 27,832 (47.2%) for bulk milk PCR, 3,229 (5.5%) for serum antibody-ELISA, 9,132 (15.5%) for blood/serum/tissue antigen-ELISA, and 7,122 (12.1%) for blood/serum/tissue PCR. Of the 17,946 accessions for blood/serum/tissue samples, 4,316 (24.0%) were missing the herd production type and 6,678 (37.2%) were missing the animals age. Approximately 7,000/10,958 (65%) dairy herds and 1,600/43,611 (4%) beef herds were conducting annual BVD screening tests. In 2016/2017, the prevalence of accessions with ≥1 BVD-positive result was 40.6% for bulk milk antibody, 6.4% for bulk milk PCR, 45.6% for serum antibody, and 9.8% for blood/serum/tissue antigen-ELISA or PCR tests. There was substantial regional variation in both the percentage of herds testing for BVD and the prevalence of positive accessions. Following pooled serum antibody-ELISA, only 175/604 (29.0%) beef herds and 177/566 (31.3%) dairy herds had recorded follow-up testing. Conclusions and Clinical Relevance: Laboratory diagnostic accession data has the potential to provide valuable insights about BVD epidemiology in New Zealand, but there are significant limitations in the data collected and discrepancies in the different systems that each laboratory uses to measure, interpret, and record diagnostic data. There is a strong need to develop a more consistent national system for recording and sharing BVD test results to support BVD management at farm and industry levels. Abbreviations: BVD: Bovine viral diarrhoea; Ct: Cycle threshold; NAIT: National Animal Identification and Tracing; NZVP: New Zealand Veterinary Pathology; PI: Persistently infected; S/P: Sample to positive control.

Probiotic Potential of Leuconostoc pseudomesenteroides and Lactobacillus Strains Isolated From Yaks

The purpose of this study was to evaluate the antibacterial activity and safety of bacterias with probiotic potential isolated from free-ranging Tibetan yaks in high altitude regions of Tibet. For this purpose, one Leuconostoc pseudomesenteroides strain (named P1) and two Lactobacillus johnsonii and Lactobacillus mucosae strains (named LY1 and LY2), respectively, were isolated from fecal samples of Tibetan yaks. The antibacterial activity of the isolates was studied using Escherichia coli (E. coli ATCC 25922), Staphylococcus aureus (S. aureus ATCC 26112), and Salmonella enteritidis (S. enteritidis NCTC 13349) as indicator pathogens. The results showed that LY1 had high antibacterial efficacy against E. coli and S. enteritidis, while P1 had the most powerful bacteriostatic ability against S. aureus. PCR amplification showed that all the isolated strains were positive for Ent P2 (enterocin P-like bacteriocin) and exhibited a high tolerance to bile and low pH. Moreover, the safety of P1, LY1, and LY2 was determined through antibiotic resistance experiments, resistance gene testing, and hemolytic analysis while the antibacterial activity was assessed by in vitro and in vivo experiments. The LY2 strain was abandoned as a potential probiotic due to the detection of the vanA gene. The mice were fed from days 1 to 30 in six groups, the P1-1 (gavaged with P1 1 × 108 CFU/day), P1-2 (gavaged with P1 1 × 109 CFU/day), LY1-1 (gavaged with LY1 1 × 108 CFU/day), LY1-2 (gavaged with LY1 1 × 109 CFU/day), control (gavaged with an equal volume of vehicle), and blank control (gavaged with an equal volume of vehicle) groups. After 30 days, mice in the P1-1, P1-2, LY1-1, LY1-2, and control groups were intraperitoneal challenged with 1 × 108 CFU of E. coli (n = 10) in the abdomen. After 2 days of infection, the mice in the control group showed more severe damage in the liver, spleen and intestine than the mice in the P1-2 and LY1-2 groups. The mice in the P1-2 and LY1-2 groups had lower rates of diarrhea and mortality than other groups. In conclusion, bacteria with probiotic potential isolated from yaks may possibly be effective and safe antibacterial substances, providing a new treatment method to reduce the incidence of diarrhea associated with bacterial diseases in yaks.

Elimination of bovine viral diarrhoea virus in New Zealand: a review of research progress and future directions

The major impacts of bovine viral diarrhoea (BVD) on cattle health and production have prompted many countries to embark on national elimination programmes. These programmes typically involve identifying and removing persistently infected (PI) cattle in infected herds and implementing biosecurity measures, such as pre- or post-movement testing. In order to design a systematic national control programme to eliminate BVD in New Zealand, which achieves the greatest benefits to the industries at the lowest cost to individual farmers, an accurate understanding is necessary of the epidemiology, economics and social motivation for BVD control in New Zealand. In this article we briefly review the pathogenesis of BVD, transmission and diagnosis of BVD virus infection, and effectiveness of vaccination. We summarise the current state of knowledge of the prevalence, risk factors for transmission, and financial impacts of BVD in New Zealand. We describe control programmes in Europe and then discuss the challenges that must be addressed to design a cost-effective national control programme to eliminate BVD in New Zealand.

Dembo polymerase chain reaction technique for detection of bovine abortion, diarrhea, and respiratory disease complex infectious agents in potential vectors and reservoirs

Bovine abortion, diarrhea, and respiratory disease complexes, caused by infectious agents, result in high and significant economic losses for the cattle industry. These pathogens are likely transmitted by various vectors and reservoirs including insects, birds, and rodents. However, experimental data supporting this possibility are scarce. We collected 117 samples and screened them for 44 bovine abortive, diarrheal, and respiratory disease complex pathogens by using Dembo polymerase chain reaction (PCR), which is based on TaqMan real-time PCR. Fifty-seven samples were positive for at least one pathogen, including bovine viral diarrhea virus, bovine enterovirus, Salmonella enterica ser. Dublin, Salmonella enterica ser. Typhimurium, and Neospora caninum; some samples were positive for multiple pathogens. Bovine viral diarrhea virus and bovine enterovirus were the most frequently detected pathogens, especially in flies, suggesting an important role of flies in the transmission of these viruses. Additionally, we detected the N. caninum genome from a cockroach sample for the first time. Our data suggest that insects (particularly flies), birds, and rodents are potential vectors and reservoirs of abortion, diarrhea, and respiratory infectious agents, and that they may transmit more than one pathogen at the same time.

Perspectives on Current Challenges and Opportunities for Bovine Viral Diarrhoea Virus Eradication in Australia and New Zealand

This review outlines the history of bovine viral diarrhoea virus (BVDV) and the current situation in Australia and New Zealand. BVDV has been reported as present in cattle from both countries for close to 60 years. It rates as the second most economically significant disease afflicting cattle, and is highly prevalent and spread throughout the beef and dairy industries. While other cattle diseases have been the subject of government control and eradication, infection with BVDV is presently not. Eradication has been undertaken in many other countries and been judged to be a good investment, resulting in positive economic returns. Presently, Australia and New Zealand have adopted a non-compulsory approach to control schemes, initiated and managed by farmers and veterinarians without the ultimate goal of eradication. Moving towards eradication is possible with the infrastructure both countries possess, but will require additional resources, coordination, and funding from stakeholders to move to full eradication.

Engaging veterinarians and farmers in eradicating bovine viral diarrhoea: a systematic review of economic impact

Bovine viral diarrhoea (BVD) is a significant drain on efficient and successful cattle production in both dairy and beef systems around the world. Several countries have achieved eradication of this disease, but always through the motivation of stakeholders who accept the benefits of eradication. These include increased cattle welfare and fitness of cattle to withstand other diseases, and decreased costs of production, the latter resulting from both decreased costs spent on managing the disease and decreased losses. This paper provides a systematic review of 31 papers, published between 1991 and 2015, that address the economic impact of BVD. Each paper takes a different approach, in either beef or dairy production or both. However with the breadth of work collated, a stakeholder engaged in BVD eradication should find an economic figure of most relevance to them. The reported economic impact ranges from £0 to £552 per cow per year (£2370 including outliers). This range represents endemic or subclinical disease situations seen in herds with stable BVD virus infection, and epidemic or severe acute situations, most often seen in naïve herds. The outcome of infection is therefore dependent on the immune status of the animal and severity of the strain. The variations in figures for the economic impact of BVD relate to these immune and pathogenicity factors, along with the variety of impacts monitored.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bovine viral diarrhoea (BVD)

Bovine viral diarrhoea (BVD) has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of BVD to be listed, Article 9 for the categorisation of BVD according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to BVD. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, BVD can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (d) and (e) of Article 9(1). The assessment here performed on compliance with the criteria as in Section 3 of Annex IV referred to in point (c) of Article 9(1) is inconclusive. The animal species to be listed for BVD according to Article 8(3) criteria are mainly species of the families Bovidae, Cervidae and Camelidae as susceptible species and several mammalian species as reservoirs.

Economic evaluation of the eradication program for bovine viral diarrhea in the Swiss dairy sector

Since 2008, the Swiss veterinary service has been running a mandatory eradication program for Bovine Viral Diarrhea (BVD) that is focused on detecting and eliminating persistently infected (PI) animals. Detection was initially based on antigen testing from ear tag samples of the entire cattle population, followed by antigen testing of all newborn calves until 2012. Since then, bulk milk serology (dairy herds) and blood sample serology (beef herds) have been used for the surveillance of disease-free herds. From 2008 to 2012, the proportion of newborn PI calves decreased from 1.4% to less than 0.02%. However, this success was associated with substantial expenditures. The aim of this study was to conduct an economic evaluation of the BVD eradication program in the Swiss dairy sector. The situation before the start of the program (herd-level prevalence: 20%) served as a baseline scenario. Production models for three dairy farm types were used to estimate gross margins as well as net production losses and expenditures caused by BVD. The total economic benefit was estimated as the difference in disease costs between the baseline scenario and the implemented eradication program and was compared to the total eradication costs in a benefit-cost analysis. Data on the impact of BVD virus (BVDV) infection on animal health, fertility and production parameters were obtained empirically in a retrospective epidemiological case-control study in Swiss dairy herds and complemented by literature. Economic and additional production parameters were based on benchmarking data and published agricultural statistics. The eradication costs comprised the cumulative expenses for sampling and diagnostics. The economic model consisted of a stochastic simulation in @Risk for Excel with 20,000 iterations and was conducted for a time period of 14 years (2008-2021). The estimated annual financial losses in BVDV infected herds were CHF 85-89 per dairy cow and CHF 1337-2535 for an average farm, depending on the production type. The median net present value (NPV) was estimated at CHF 44.9 million (90% central range: CHF 13.4 million-69.4 million) and the break-even point to have been reached in 2015. Overall, the outcomes demonstrate that the Swiss BVD eradication program results in a net benefit for the dairy sector. These findings are relevant for planning similar BVD control programs in other countries.

Prevention of fetal infection in heifers challenged with bovine viral diarrhoea virus type 1a by vaccination with a type 1c or type 1a vaccine

AIMS

To evaluate a vaccine containing type 1c bovine viral diarrhoea (BVD) virus for prevention of fetal infection in pregnant heifers when challenged with New Zealand BVD virus type 1a 6 months after vaccination, compared to unvaccinated heifers and heifers vaccinated with a vaccine containing type 1a BVD virus.

METHODS

Fifty five crossbred Friesian heifers, free from BVD virus and antibody, were randomly allocated to three groups. Twenty five heifers were vaccinated twice with a vaccine containing type 1c BVD virus (T1c group), and 10 heifers with a vaccine containing type 1a BVD virus (T1a group), and 20 heifers were unvaccinated (NC group). After oestrus synchronisation the heifers were bred by artificial insemination followed by natural bull mating. Six months after booster vaccination 15 heifers from the T1c group, eight from the T1a group, and 15 from the NC group, were exposed to four calves that were persistently infected with type 1a BVD virus, for 4 weeks. At the beginning of the challenge phase 36/38 heifers were 72-74 days pregnant and 2/38 heifers were approximately 53 days pregnant. Approximately 52 days after the start of the challenge the heifers were subjected to euthanasia and fetal tissues were collected for the detection of BVD virus by ELISA in fetal heart blood and PCR in fetal tissues.

RESULTS

Based on PCR results, BVD virus was detected in 15/15 fetuses in the NC group, compared to 4/14 fetuses in the T1c group and 3/8 fetuses in the T1a group. The proportion of BVD virus-positive fetuses was lower in both vaccinated groups compared to the NC group (p<0.002), but there was no difference in proportions between the vaccinated groups (p=1.00). Fetal protection, expressed as the prevented fraction, was 71.4 (95% CI=41.9-91.6)% and 62.5 (95% CI=24.5-91.5)% for the T1c and T1a groups, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

The vaccines containing killed type 1c and type 1a BVD viruses significantly reduced fetal infection following challenge with a New Zealand type 1a BVD virus. Prevention of fetal infection by vaccination may not be 100%, and the risk of persistently infected calves being born to some vaccinated cattle should be acknowledged and managed as part of a BVD control programme.

Genetic characterization of bovine viral diarrhea virus strains in Beijing, China and innate immune responses of peripheral blood mononuclear cells in persistently infected dairy cattle

To acquire epidemiological data on the bovine viral diarrhea virus (BVDV) and identify cattle persistently infected (PI) with this virus, 4,327 samples from Holstein dairy cows were screened over a four-year period in Beijing, China. Eighteen BVD viruses were isolated, 12 from PI cattle. Based on genetic analysis of their 5'-untranslated region (5'-UTR), the 18 isolates were assigned to subgenotype BVDV-1m, 1a, 1d, 1q, and 1b. To investigate the innate immune responses in the peripheral-blood mononuclear cells of PI cattle, the expression of Toll-like receptors (TLRs), RIG-I-like receptors, interferon-α (IFN-α), IFN-β, myxovirus (influenza virus) resistance 1 (MX1), and interferon stimulatory gene 15 (ISG15) was assessed by qPCR. When compared with healthy cattle, the expression of TLR-7, IFN-α, and IFN-β mRNA was downregulated, but the expression of MX1 and ISG-15 mRNA was upregulated in PI cattle. Immunoblotting analysis revealed that the expression of interferon regulatory factor 3 (IRF-3) and IRF-7 was lower in PI cattle than in healthy cattle. Thus, BVDV-1m and 1a are the predominant subgenotypes in the Beijing region, and the strains are highly divergent. Our findings also suggest that the TLR-7/IRF-7 signaling pathway plays a role in evasion of host restriction by BVDV.

Characterization of bovine A20 gene: Expression mediated by NF-κB pathway in MDBK cells infected with bovine viral diarrhea virus-1

Cytokine production for immunological process is tightly regulated at the transcriptional and posttranscriptional levels. The NF-κB signaling pathway maintains immune homeostasis in the cell through the participation of molecules such as A20 (TNFAIP3), which is a key regulatory factor in the immune response, hematopoietic differentiation, and immunomodulation. Although A20 has been identified in mammals, and despite recent efforts to identify A20 members in other higher vertebrates, relatively little is known about the composition of this regulator in other classes of vertebrates, particularly for bovines. In this study, the genetic context of bovine A20 was explored and compared against homologous genes in the human, mouse, chicken, dog, and zebrafish chromosomes. Through in silico analysis, several regions of interest were found conserved between even phylogenetically distant species. Additionally, a protein-deduced sequence of bovine A20 evidenced many conserved domains in humans and mice. Furthermore, all potential amino acid residues implicated in the active site of A20 were conserved. Finally, bovine A20 mRNA expression as mediated by the bovine viral diarrhea virus and poly (I:C) was evaluated. These analyses evidenced a strong fold increase in A20 expression following virus exposure, a phenomenon blocked by a pharmacological NF-κB inhibitor (BAY 117085). Interestingly, A20 mRNA had a half-life of only 32min, likely due to adenylate- and uridylate-rich elements in the 3'-untranslated region. Collectively, these data identify bovine A20 as a regulator of immune marker expression. Finally, this is the first report to find the bovine viral diarrhea virus modulating bovine A20 activation through the NF-κB pathway.

Development of a novel detection system for microbes from bovine diarrhea by real-time PCR

Diarrhea in cattle is one of the most economically costly disorders, decreasing milk production and weight gain. In the present study, we established a novel simultaneous detection system using TaqMan real-time PCR designed as a system for detection of microbes from bovine diarrhea using real-time PCR (referred to as Dembo-PCR). Dembo-PCR simultaneously detects a total of 19 diarrhea-causing pathogens, including viruses, bacteria and protozoa. Specific primer-probe sets were newly designed for 7 pathogens and were synthesized on the basis of previous reports for 12 pathogens. Assays were optimized to react under the same reaction conditions. The PCR efficiency and correlation coefficient (R(2)) of standard curves for each assay were more than 80% and 0.9766, respectively. Furthermore, the sensitivity of Dembo-PCR in fecal sample analysis was measured with feces spiked with target pathogens or synthesized DNA that included specific nucleotide target regions. The resulting limits of detection (LOD) for virus-spiked samples, bacteria and DNA fragments were 0.16-1.6 TCID50 (PFU/reaction), 1.3-13 CFU/reaction and 10-100 copies/reaction, respectively. All reactions showed high sensitivity in pathogen detection. A total of 8 fecal samples, collected from 6 diarrheic cattle, 1 diarrheic calf and 1 healthy cow, were tested using Dembo-PCR to validate the assay's clinical performance. The results revealed that bovine coronavirus had infected all diarrheic adult cattle and that bovine torovirus had infected the diarrheic calf. These results suggest that Dembo-PCR may be a powerful tool for diagnosing infectious agents in cattle diarrhea.

Analysis of individual farm investigations into bovine viral diarrhoea in beef herds in the North Island of New Zealand

AIMS

To use data from individual farm investigations of herd bovine viral diarrhoea (BVD) status and risk factors to estimate the prevalence of recent active BVD virus (BVDV) infection in beef herds in the Waikato, King Country, Wairoa and Gisborne areas of New Zealand; to identify farm management factors associated with BVDV infection in these herds; and to gain a better understanding of farmers' attitudes to BVD.

METHODS

Data from 43 farm investigations were combined. Each investigation involved collecting blood samples from 10 to 15 rising 2-year-old replacement heifers (n=637) to test for individual antibodies to BVDV using ELISA. A farm was classified as having evidence of recent active infection when more than 20% of samples were positive. At the time of sampling a risk assessment questionnaire was completed to collect information about farm management practices and farmer attitudes. The influence of these factors on the odds of there being evidence of recent BVDV infections on the farm was then analysed using logistic regression modelling.

RESULTS

Of the 43 herds, 25 (58 (95% CI=43-71)%) had evidence of recent active BVDV infection. The percentage of such herds did not differ between the four areas (min 55, max 67%; p=0.87). Four factors were identified as contributing to the odds of a herd being classified as having recent active BVDV infection. Increasing numbers of heifers on the farm, introducing replacement heifers, and the farmer considering BVD was an issue on the farm were all significantly associated with increased odds of active infection; whereas vaccinating introduced breeding bulls was associated with decreased odds of infection.

CONCLUSIONS

The results are consistent with earlier studies that found BVD was widespread in beef herds throughout New Zealand. Farm management factors that may influence the odds of active BVDV infection have been identified.

CLINICAL RELEVANCE

Pooling data from individual herd investigations of BVD status can significantly add to the value of those investigations and provide information that can identify potential risk factors for a practice area. With these local data now available, our clients should have greater confidence in the need to proactively manage BVD on their farms.

What is the global economic impact of Neospora caninum in cattle - the billion dollar question

Neospora caninum is regarded as one of the most important infectious causes of abortions in cattle worldwide, yet the global economic impact of the infection has not been established. A systematic review of the economic impact of N. caninum infections/abortions was conducted, searching PubMed with the terms 'cattle' and 'Neospora'. This yielded 769 publications and the abstracts were screened for economically relevant information (e.g. abortion prevalence and risk, serological prevalence). Further analysis was restricted to countries with at least five relevant publications. In total, 99 studies (12.9%) from 10 countries contained data from the beef industry (25 papers (25.3%)) and 72 papers (72.8%) from the dairy industry (with the remaining two papers (2.0%) describing general abortion statistics). The total annual cost of N. caninum infections/abortions was estimated to range from a median US $1.1 million in the New Zealand beef industry to an estimated median total of US $546.3 million impact per annum in the US dairy population. The estimate for the total median N. caninum-related losses exceeded US $1.298 billion per annum, ranging as high as US $2.380 billion. Nearly two-thirds of the losses were incurred by the dairy industry (US $842.9 million). Annual losses on individual dairy farms were estimated to reach a median of US $1,600.00, while on beef farms these costs amounted to just US $150.00. Pregnant cows and heifers were estimated to incur, on average, a loss due to N. caninum of less than US $20.00 for dairy and less than US $5.00 for beef. These loss estimates, however, rose to ∼US $110.00 and US $40.00, respectively, for N. caninum-infected pregnant dairy and beef cows. This estimate of global losses due to N. caninum, with the identification of clear target markets (countries, as well as cattle industries), should provide an incentive to develop treatment options and/or vaccines.

Validation and evaluation of a commercially available ELISA for the detection of antibodies specific to bovine viral diarrhoea virus (bovine pestivirus)

OBJECTIVE

To compare the performance of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies specific to bovine viral diarrhoea virus (BVDV) with a virus neutralisation test (VNT) and agarose gel immunodiffusion (AGID) test.

DESIGN

A total of 125 cattle serum samples were tested by a commercially available ELISA for antibodies specific to BVDV and by a VNT as the reference standard. A comparison between AGID and ELISA for detection of BVDV antibodies was also carried out, using 1182 serum samples from unvaccinated South Australian cattle.

METHODS

Two-graph receiver operating characteristics (TG-ROC) analysis was used to confirm that the manufacturer's recommended cut-off value for the ELISA was appropriate. Two-by-two tables were constructed to analyse the concordance of serological results among the three assays. McNemar tests were used to assess the agreement among serological tests.

RESULTS AND CONCLUSIONS

Using the manufacturer's cut-off threshold, supported by TG-ROC analysis, the ELISA's sensitivity and specificity were calculated to be 96.7% and 97.1%, respectively, compared with the VNT. Compared with AGID, ELISA with specific BVDV antibodies may be more sensitive and detect 5.8% more samples than AGID. McNemar test also showed a significant difference (P < 0.001) between AGID and ELISA.

Natural in utero infection of neonatal calves with bovine viral diarrhoea virus on a large dairy farm in Saudi Arabia

The dairy industry is a large and important business in Saudi Arabia. Although farms are administered to high international standards, some reproduction problems, of uncertain aetiology, are encountered. The most frequently seen are conception failures, abortions, stillbirths and the birth of weak or malformed calves. These conditions are suggestive of bovine viral diarrhoea virus (BVDV) infection. Unfortunately, very little published information is available regarding the impact of this disease on cattle populations in Saudi Arabia. As a consequence, the present study was carried out and is the first of its kind in Saudi Arabia and the Gulf region. The aim of the study was to elucidate the role of in utero BVDV infection leading to the birth of weak or malformed calves on a large dairy farm in Saudi Arabia. The study was divided into two parts. Firstly, apparently healthy neonatal calves were sampled for the detection of pre-colostral serum antibodies to BVDV. The presence of these antibodies indicates exposure of the foetus to BVDV during the last two trimesters of gestation. Secondly, tissue samples from malformed neonatal calves were examined for the presence of BVDV antigens. Detection of such antigens confirms exposure of the foetus to the virus during the first trimester of gestation. The results of the investigation indicated that 36.1% of the neonatal calves were exposed to BVDV infection in utero. This is higher than what has been reported in the literature and suggests that dairy farmers in the Arabian Peninsula need to be made aware of the dangers of BVDV infections in their herds. The epidemiological significance of the results is discussed.

Bovine tuberculosis and milk production in infected dairy herds in Ireland

This study describes the relationship between bovine tuberculosis (TB) and milk yield in TB-infected dairy herds in Ireland. The study had two objectives: to determine whether cows detected as TB reactors (and thus subject to immediate slaughter) were likely to be the higher milk-producing cows, and to determine whether subclinical TB infection was associated with reduced milk production at or around the time of disclosure (detection). All Irish dairy herds restricted from trading between the 1(st) June 2004 and the 31(st) May 2005 as a result of two or more TB reactors by the Single Intradermal Comparative Tuberculin Test (SICTT) were considered for study. The data consisted of 419 herds. Data were collected on all TB reactors and a random sample of 5 non-reactor cows in these herds: a data set of 4340 cows (2342 TB reactors and 1998 non-reactors). Previous milk data for the cows were taken into consideration and thus all lactations on a cow were analysed together with the years of lactations. There was an inherent hierarchical structure in the data, with lactations nested within cows and cows within herds and thus a linear mixed model with two random effects was used to describe the data. The results of this study showed that for all lactations and years under investigation, milk yield was significantly lower for TB reactor cows, with differences ranging from 120kg (2003, lactation 3) to 573kg (2001, lactation 1), when compared to the non-reactor cows.