Differential somatic cell count as an additional indicator for intramammary infections in dairy cows.

Mastitis, often caused by intramammary infection (IMI), is a significant problem in dairy farming globally. Somatic cell count (SCC) is widely used as a parameter for screening IMI in cows that are then treated or culled. We investigated the potential of a new parameter, differential SCC (DSCC), to detect IMI at cow level when SCC is already known. We achieved this using bacterial culture (BC) and PCR to detect 4 categories of pathogens (major, minor, other, and any) in 2 Danish dairy herds. Quarter milk samples were collected from monthly dairy herd improvement samplings over 1 yr and analyzed with BC, whereas cow-level dairy herd improvement samples were analyzed using PCR. Days in milk, parity, and IMI status had a significant effect on DSCC. Using DSCC in addition to SCC significantly improved the indication of IMI compared with using only SCC in the any pathogen category in both herds as well as the minor pathogens category in herd 2 when BC was used for detection. When PCR was used to detect IMI, the use of DSCC in addition to SCC was significant for the other pathogens category in herd 1 and the minor pathogens category in herd 2. Thus, our data revealed that DSCC can add significant information describing IMI status even when SCC is already known; however, this depends on the causative pathogen. Future studies may address how to use DSCC in practice as well as consider the availability of temporal data to potentially gain insight into the course of infection.

Composite or aseptic quarter milk samples: Sensitivity and specificity of PCR and bacterial culture of Staphylococcus aureus based on Bayesian latent class evaluation.

Bacterial culture (BC) and quantitative polymerase chain reaction (qPCR) are widely used as diagnostic tests for pathogens causing intra-mammary infections (IMI) and it is therefore important to evaluate their performance to optimize pathogen detection. However, with no reference standard, their sensitivity (Se) and specificity (Sp) are unknown. Furthermore, the Se and Sp can differ between quarter samples and composite samples, both of which can be used to test for IMI. Latent class analysis (LCA) offers a method for estimating the Se and Sp of two tests on the same population, but to our knowledge this has not yet been applied to qPCR and BC for the detection of Staph. aureus in both composite and aseptically collected quarter milk samples. This allows for a performance evaluation of not only the two diagnostic methods, but also the two different samples -both cow and quarter level. In this study, we used Bayesian LCA on a dataset from one sampling day at a Danish dairy herd to estimate the Se and Sp for detecting Staph. aureus at cow and quarter level. We used Ct cut-offs of 32 and 37 cycles for the qPCR. When using a cut-off of 37 cycles, the estimated Se and Sp for BC were 62.2% and 90.5% at cow level, and 90.7% and 93.5% at quarter level, respectively. Similarly, the estimated Se and Sp for qPCR at cow level were 82.7% and 84.1%, respectively, and 80.0% and 96.8% at quarter level. Sp was therefore higher for both BC and qPCR at quarter level. Se was also highest for BC at quarter level, but the opposite was true for qPCR. The same pattern was found using a Ct cut-off at 32 cycles, but with different estimates. The results show that qPCR with a Ct cut-off at 37 had a higher Se than BC for composite DHI samples and it is therefore more suitable as a routine screening test for Staph. aureus. However, BC on quarter samples gave the highest Se and Sp and should therefore be used for confirmatory testing.

Transmission dynamics of Staphylococcus aureus within two Danish dairy cattle herds.

Staphylococcus aureus is a major pathogen causing intramammary infections (IMI) in dairy cattle herds worldwide. Simulation models can be used to investigate the epidemiologic and economic outcomes of different control strategies against IMI. The transmission rate parameter is one of the most influential parameters on the outcomes of these simulation models. Very few studies have estimated the transmission rate parameter and investigated the transmission dynamics of Staph. aureus IMI in dairy cattle herds. The objective of our study was therefore to analyze the transmission dynamics of Staph. aureus in 2 Danish dairy herds participating in a longitudinal study. The 2 herds had 180 and 360 milking cows, and animals were tested at quarter level once per month over a period of 1 yr. We estimated the quarter-level prevalence to be 34% for herd 1 and 2.57% for herd 2. The daily quarter-level transmission rate was estimated to be 0.0132 and 0.0077 cases/quarter-day for herds 1 and 2, respectively, and the median duration of infection was estimated to be 91 and 64 d for herds 1 and 2, respectively. We also estimated the reproductive ratio at 1.21 for herd 1 and 0.52 for herd 2. The results can provide valuable information for simulation models to aid decision-making in terms of the prevention and control of Staph. aureus IMI in dairy cattle herds.

Short time window for transmissibility of African swine fever virus from a contaminated environment.

Since the introduction of African swine fever virus (ASFV) into the Baltic states and Poland in 2014, the disease has continued to spread within these regions. In 2017, the virus spread further west and the first cases of disease were reported in the Czech Republic and Romania, in wild boar and domestic pigs, respectively. To control further spread, knowledge of different modes of transmission, including indirect transmission via a contaminated environment, is crucial. Up until now, such an indirect mode of transmission has not been demonstrated. In this study, transmission via an environment contaminated with excretions from ASFV-infected pigs was investigated. Following euthanasia of pigs that were infected with an isolate of ASFV from Poland (POL/2015/Podlaskie/Lindholm), healthy pigs were introduced into the pens, in which the ASFV-infected pigs had been housed. Introduction was performed at 1, 3, 5 or 7 days, following euthanasia of the infected pig groups. Pigs, that were introduced into the contaminated environment after 1 day, developed clinical disease within 1 week, and both ASFV DNA and infectious virus were isolated from their blood. However, pigs introduced into the contaminated pens after 3, 5 or 7 days did not develop any signs of ASFV infection and no viral DNA was detected in blood samples obtained from these pigs within the following 3 weeks. Thus, it was shown that exposure of pigs to an environment contaminated with ASFV can result in infection. However, the time window for transmissibility of ASFV seems very limited, and, within our experimental system, there appears to be a rapid decrease in the infectivity of ASFV in the environment.

Estimation of the transmission dynamics of African swine fever virus within a swine house.

The spread of African swine fever virus (ASFV) threatens to reach further parts of Europe. In countries with a large swine production, an outbreak of ASF may result in devastating economic consequences for the swine industry. Simulation models can assist decision makers setting up contingency plans. This creates a need for estimation of parameters. This study presents a new analysis of a previously published study. A full likelihood framework is presented including the impact of model assumptions on the estimated transmission parameters. As animals were only tested every other day, an interpretation was introduced to cover the weighted infectiousness on unobserved days for the individual animals (WIU). Based on our model and the set of assumptions, the within- and between-pen transmission parameters were estimated to ß w = 1·05 (95% CI 0·62-1·72), ß b = 0·46 (95% CI 0·17-1·00), respectively, and the WIU = 1·00 (95% CI 0-1). Furthermore, we simulated the spread of ASFV within a pig house using a modified SEIR-model to establish the time from infection of one animal until ASFV is detected in the herd. Based on a chosen detection limit of 2·55% equivalent to 10 dead pigs out of 360, the disease would be detected 13-19 days after introduction.

Spatial patterns of antimicrobial resistance genes in a cross-sectional sample of pig farms with indoor non-organic production of finishers.

Antimicrobial resistance (AMR) in pig populations is a public health concern. There is a lack of information of spatial distributions of AMR genes in pig populations at large scales. The objective of the study was to describe the spatial pattern of AMR genes in faecal samples from pig farms and to test if the AMR genes were spatially randomly distributed with respect to the geographic distribution of the pig farm population at risk. Faecal samples from 687 Danish pig farms were collected in February and March 2015. DNA was extracted and the levels of seven AMR genes (ermB, ermF, sulI, sulII, tet(M), tet(O) and tet(W)) were quantified on a high-throughput real-time PCR array. Spatial differences for the levels of the AMR genes measured as relative quantities were evaluated by spatial cluster analysis and creating of risk maps using kriging analysis and kernel density estimation. Significant spatial clusters were identified for ermB, ermF, sulII and tet(W). The broad spatial trends in AMR resistance evident in the risk maps were in agreement with the results of the cluster analysis. However, they also showed that there were only small scale spatial differences in the gene levels. We conclude that the geographical location of a pig farm is not a major determinant of the presence or high levels of AMR genes assessed in this study.

Decisions on control of foot-and-mouth disease informed using model predictions.

The decision on whether or not to change the control strategy, such as introducing emergency vaccination, is perhaps one of the most difficult decisions faced by the veterinary authorities during a foot-and-mouth disease (FMD) epidemic. A simple tool that may predict the epidemic outcome and consequences would be useful to assist the veterinary authorities in the decision-making process. A previously proposed simple quantitative tool based on the first 14 days outbreaks (FFO) of FMD was used with results from an FMD simulation exercise. Epidemic outcomes included the number of affected herds, epidemic duration, geographical size and costs. The first 14 days spatial spread (FFS) was also included to further support the prediction. The epidemic data was obtained from a Danish version (DTU-DADS) of a pre-existing FMD simulation model (Davis Animal Disease Spread - DADS) adapted to model the spread of FMD in Denmark. The European Union (EU) and Danish regulations for FMD control were used in the simulation. The correlations between FFO and FFS and the additional number of affected herds after day 14 following detection of the first infected herd were 0.66 and 0.82, respectively. The variation explained by the FFO at day 14 following detection was high (P-value<0.001). This indicates that the FFO may take a part in the decision of whether or not to intensify FMD control, for instance by introducing emergency vaccination and/or pre-emptive depopulation, which might prevent a "catastrophic situation". A significant part of the variation was explained by supplementing the model with the FFS (P-value<0.001). Furthermore, the type of the index-herd was also a significant predictor of the epidemic outcomes (P-value<0.05). The results of the current study suggest that national veterinary authorities should consider to model their national situation and to use FFO and FFS to help planning and updating their contingency plans and FMD emergency control strategies.

Comparing control strategies against foot-and-mouth disease: will vaccination be cost-effective in Denmark?

Recent outbreaks of foot-and-mouth disease (FMD) in Europe have highlighted the need for assessment of control strategies to optimise control of the spread of FMD. Our objectives were to assess the epidemiological and financial impact of simulated FMD outbreaks in Denmark and the effect of using ring depopulation or emergency vaccination to control these outbreaks. Two stochastic simulation models (InterSpreadPlus (ISP) and the modified Davis Animal Disease Simulation model (DTU-DADS)) were used to simulate the spread of FMD in Denmark using different control strategies. Each epidemic was initiated in one herd (index herd), and a total of 5000 index herds were used. Four types of control measures were investigated: (1) a basic scenario including depopulation of detected herds, 3 km protection and 10 km surveillance zones, movement tracing and a three-day national standstill, (2) the basic scenario plus depopulation in ring zones around detected herds (Depop), (3) the basic scenario plus protective vaccination within ring zones around detected herds, and (4) the basic scenario plus protective vaccination within ring zones around detected herds. Disease spread was simulated through direct animal movements, medium-risk contacts (veterinarians, artificial inseminators or milk controllers), low-risk contacts (animal feed and rendering trucks, technicians or visitors), market contacts, abattoir trucks, milk tanks, or local spread. The two simulation models showed different results in terms of the estimated numbers. However, the tendencies in terms of recommendations of strategies were similar for both models. Comparison of the different control strategies showed that, from an epidemiological point of view, protective vaccination would be preferable if the epidemic started in a cattle herd in an area with a high density of cattle, whereas if the epidemic started in an area with a low density of cattle or in other species, protective vaccination or depopulation would have almost the same preventive effect. Implementing additional control measures either 14 days after detection of the first infected herd or when 10 herds have been diagnosed would be more efficient than implementing additional control measures when more herds have been diagnosed. Protective vaccination scenarios would never be cost-effective, whereas depopulation or suppressive vaccination scenarios would most often be recommended. Looking at the median estimates of the cost-benefit analysis, depopulation in zones would most often be recommended, although, in extreme epidemics, suppressive vaccination scenarios could be less expensive. The vast majority of the costs and losses associated with a Danish epidemic could be attributed to export losses.

Bioeconomic modeling of intervention against clinical mastitis caused by contagious pathogens.

The objective of this study was to assess the epidemiologic and economic consequences of intervention against contagious clinical mastitis during lactation. A bioeconomic model of intramammary infections (IMI) was used to simulate contagious spread of Staphylococcus aureus, Streptococcus uberis, and Streptococcus dysgalactiae, and an environmental spread of Escherichia coli IMI in a 100-cow dairy herd during 1 quota year. The costs of clinical IMI, subclinical IMI, and intervention were calculated into the total annual net costs of IMI during lactation per scenario and compared with a default scenario. Input parameter values were based on the scientific literature. The scenarios were 3-d intramammary lactational treatment (default), 5-d intramammary treatment, 5-d intramammary treatment and 3-d systemic treatment, 3-d intramammary treatment and culling bacteriologically unrecovered clinical IMI cows, and 5-d intramammary treatment and culling bacteriologically unrecovered clinical IMI cows. Sensitivity analysis was conducted on parameter input values. The results showed that interventions including antibiotic treatment combined with culling unrecovered clinical IMI cows resulted in the lowest transmission, number of IMI cases, and persistent subclinical IMI cases. Nonetheless, the high associated costs of culling bacteriologically unrecovered clinical IMI cows made the other scenarios with a long and intensive antibiotic treatment, but without culling, the most cost effective. The model was sensitive to changes to the cure rate of clinical IMI following treatment, but the ranking of the intervention scenarios did not change. The model was most sensitive to the changes to the transmission rate of Staph. aureus. The ranking of the intervention scenarios changed at low transmission rate of this pathogen, in which the default scenario became the most cost-effective scenario. In case of high transmission of contagious IMI pathogens, long and intensive treatment of clinical IMI should be preceded by strategies that lower the transmission.

Source attribution of human campylobacteriosis using a meta-analysis of case-control studies of sporadic infections.

Campylobacter spp. is a widespread and important cause of human illness worldwide. Disease is frequently associated with foodborne transmission, but other routes of exposure, such as direct contact with live animals and person-to-person transmission, are also recognized. Identifying the most important sources of human disease is essential for prioritizing food safety interventions and setting public health goals. Numerous case-control studies of sporadic infections of campylobacteriosis have been published. These studies investigated a variety of potential risk factors for disease, often using different methodologies and settings. Systematic reviews (SRs) consist of a formal process for literature review focused on a specific research question, and include the identification of relevant literature, quality assessment of relevant studies, summarization or statistical analysis of data, and conclusions. With the objective of identifying the most important risk factors for human sporadic campylobacteriosis, we performed a SR of case-control studies of human sporadic cases and a meta-analysis of the obtained results. A combined SR focusing on Salmonella and Campylobacter studies was performed and the results analysed separately. From 1295 identified references, 131 passed the relevance screening, 73 passed the quality assessment stage, and data was extracted from 72 studies. Of these, 38 focused on campylobacteriosis. Information on exposures of cases and controls, and estimated odds ratios for investigated risk factors were collected and analysed. In the meta-analysis, heterogeneity between the studies and possible sources of bias were investigated, and pooled odds ratios for identified risk factors were estimated. Results suggest that travelling abroad, eating undercooked chicken, environmental sources, and direct contact with farm animals were significant risk factors for campylobacteriosis. Sub-analyses by geographical region, age group, and study period were performed, and differences were discussed.

Source attribution of human salmonellosis using a meta-analysis of case-control studies of sporadic infections.

Salmonella is an important cause of human illness. Disease is frequently associated with foodborne transmission, but other routes of exposure are recognized. Identifying sources of disease is essential for prioritizing public health interventions. Numerous case-control studies of sporadic salmonellosis have been published, often using different methodologies and settings. Systematic reviews consist of a formal process for literature review focused on a research question. With the objective of identifying the most important risk factors for salmonellosis, we performed a systematic review of case-control studies and a meta-analysis of obtained results. Thirty-five Salmonella case-control studies were identified. In the meta-analysis, heterogeneity between studies and possible sources of bias were investigated, and pooled odds ratios estimated. Results suggested that travel, predisposing factors, eating raw eggs, and eating in restaurants were the most important risk factors for salmonellosis. Sub-analyses by serotype were performed when enough studies were available.

Meta-analysis on the efficacy of foot-and-mouth disease emergency vaccination.

The objectives of this study were to provide a summary quantification of the efficacy of FMD emergency vaccination based on a systematic review and a meta-analysis of available literature, and to further discuss the suitability of this review and meta-analysis to summarize and further interpret the results. Peer-reviewed, symposium, and unpublished studies were considered in the analysis. Clinical protection and virological protection against FMD were used as parameters to assess the efficacy of emergency vaccination. The clinical protection was estimated based on the appearance of clinical signs including FMD lesions and fever, while the virological protection parameter was estimated based on the outcome of laboratory tests that were used to diagnose FMD infection. A meta-analysis relative risk was calculated per protection parameter. Results of the meta-analyses were examined using publication bias tests. In total, 31 studies were included in the analyses, of which 26 were peer-reviewed studies, 1 was a symposium study and 4 were unpublished studies. Cattle, swine and sheep were well protected against clinical disease and FMD infection following the use of emergency vaccine. Fortunately, no significant bias that would alter the conclusions was encountered in the analysis. Meta-analysis can be a useful tool to summarize literature results from a systematic review of the efficacy of FMD emergency vaccination.

Modelling food safety and economic consequences of surveillance and control strategies for Salmonella in pigs and pork.

Targets for maximum acceptable levels of Salmonella in pigs and pork are to be decided. A stochastic simulation model accounting for herd and abattoir information was used to evaluate food safety and economic consequences of different surveillance and control strategies, based among others on Danish surveillance data. An epidemiological module simulated the Salmonella carcass prevalence for different scenarios. Cost-effectiveness analysis was used to compare the costs of the different scenarios with their expected effectiveness. Herd interventions were not found sufficient to attain Salmonella carcass prevalence <1%. The cost-effectiveness of abattoir interventions changed with abattoir size. The most cost-effective strategy included the use of steam vacuum and steam ultrasound. Given uncertainty of the effect of steam vacuum and steam ultrasound, model results should be updated as more information becomes available. This framework contributes to informed decision-making for a more cost-effective surveillance and control of Salmonella in pigs and pork.

Bioeconomic modeling of lactational antimicrobial treatment of new bovine subclinical intramammary infections caused by contagious pathogens.

This study determined the direct and indirect epidemiologic and economic effects of lactational treatment of new bovine subclinical intramammary infections (IMI) caused by contagious pathogens using an existing bioeconomic model. The dynamic and stochastic model simulated the dynamics of Staphylococcus aureus, Streptococcus uberis, Streptococcus dysgalactiae, and Escherichia coli during lactation and the dry period in a 100-cow dairy herd during 1 quota year. Input parameters on cure were obtained from recent Dutch field data. The costs of clinical IMI, subclinical IMI, and intervention were calculated into the combined total annual net costs of IMI per herd. The cost effectiveness of 4 scenarios with lactational intervention was determined; scenarios included no intervention, treatment after 1 mo of infection, treatment after 2 mo of infection, and treatment after 1 mo of infection and culling of uncured cows after 2 mo of infection. Model behavior was observed for variation in parameter input values. Compared with no lactational intervention, lactational intervention of new subclinical IMI resulted in fewer clinical flare ups, less transmission within the herd, and much lower combined total annual net costs of IMI in dairy herds. Antimicrobial treatment of IMI after 1 mo of infection and culling of uncured cows after 2 mo of infection resulted in the lowest costs, whereas treatment after 2 mo of infection was associated with the highest costs between the scenarios with intervention. Changing the probability of cure resulted in a nonlinear change in the cumulative incidence of IMI cases and associated costs. Lactational treatment was able to prevent IMI epidemics in dairy herds at high transmission rates of Strep. uberis, Strep. dysgalactiae, and E. coli. Lactational treatment did not limit the spread of Staph. aureus at high transmission rates, although the associated costs were lower compared with no intervention. To improve udder health in a dairy herd, lactational treatment of contagious subclinical IMI must therefore be preceded by management measures that lower the transmission rate. Lactational treatment of environmental subclinical IMI seemed less cost effective. Detection of subclinical IMI needs improvement to be able to most effectively treat subclinical IMI caused by contagious pathogens during lactation.

Meta-analysis of dry cow management for dairy cattle. Part 1. Protection against new intramammary infections.

The objective of this study was to estimate the preventive effect of various dry cow management measures against quarter new intramammary infections (IMI) during the dry period up to 21 d postcalving. Moreover, the potential publication bias was assessed in the studies selected for this analysis. The intervention measures were blanket dry cow therapy (BDCT), selective dry cow therapy (SDCT), cloxacillin compared with other dry cow therapy products, and teat sealant. A meta-analysis relative risk (RR) was calculated per intervention and pathogen group when enough studies were available from the 33 selected studies. Results of the meta-analyses were examined using publication bias tests. Blanket dry cow therapy showed significant protection against new IMI caused by Streptococcus spp. [the pooled RR was 0.39 (0.30 to 0.51)] but no protection was observed against coliform new IMI [the pooled RR was 0.95 (0.81 to 1.10)]. After correction for publication bias, it became doubtful whether DCT is protective against new Staphylococcus spp. IMI. Cloxacillin showed similar protection against new quarter IMI compared with other DCT products [the pooled RR was 1.09 (0.94 to 1.25)]. Selective dry cow therapy showed higher protection against new IMI compared with no DCT [the pooled RR was 0.51 (0.30 to 0.86)]. However, BDCT showed more protection when compared with SDCT [the pooled RR was 0.55 (0.37 to 0.80)], but the inference about whether BDCT is superior to SDCT was dependent on whether the selection criteria for SDCT was at the cow or quarter level. Internal teat sealants showed significant protection against new IMI during the dry period [the pooled RR was 0.39 (0.18 to 0.82)]. Publication bias should be taken into account when attempts are made to review literature in a meta-analysis.

Meta-analysis of dry cow management for dairy cattle. Part 2. Cure of existing intramammary infections.

The main goal of dry cow therapy (DCT) is to cure existing intramammary infections (IMI) at dry off. Although several published studies have estimated the cure rate of IMI after DCT, variation among studies is great, which makes it difficult to conduct a proper economic evaluation of DCT. The objective of the present meta-analysis of existing peer-reviewed literature was to provide a summary quantification of quarter IMI cure based on DCT. A meta-analysis relative risk (RR) was calculated per intervention and pathogen group when at least 4 studies were available for analysis per comparison from the 22 selected studies, according to the selection criteria. Results of the meta-analysis were examined using publication bias tests. Blanket DCT with a 95% confidence interval (CI) provided a 1.78 (1.51 to 2.10) times higher calculated cure rate from quarter IMI during the dry period up to 21 d postcalving, compared with no DCT. The RR of cure was similar when treatment was conducted for Streptococcus spp. IMI quarters compared with Staphylococcus spp. IMI quarters. The pooled RR with the 95% CI were 1.83 (1.48 to 2.35) and 1.65 (1.38 to 1.96), respectively. There was no significant difference between cloxacillin and other DCT products in the cure of quarter IMI during the dry period up to 21 d postcalving. The pooled RR with the 95% CI was 1.00 (0.92 to 1.09). Similarly, there was no significant difference between cloxacillin and other DCT products in the cure of quarter Staphylococcus spp. IMI. The pooled RR with the 95% CI was 1.00 (0.96 to 1.06). The pooled RR with the 95% CI of quarter IMI cure using selective DCT, compared with no DCT, was 1.76 (1.23 to 2.54).

Production loss due to new subclinical mastitis in Dutch dairy cows estimated with a test-day model.

Milk, fat, and protein loss due to a new subclinical mastitis case may be economically important, and the objective of this study was to estimate this loss. The loss was estimated based on test-day (TD) cow records collected over a 1-yr period from 400 randomly selected Dutch dairy herds. After exclusion of records from cows with clinical mastitis, the data set comprised 251,647 TD records from 43,462 lactations of 39,512 cows. The analysis was carried out using a random regression test-day modeling approach that predicts the cow production at each TD based on the actual production at all previous TD. The definition of new subclinical mastitis was based on the literature and assumed a new subclinical case if somatic cell count (SCC) was >100,000 cells/mL after a TD with SCC <50,000 cells/mL. A second data set was created by applying an adjustment to correct low SCC for the dilution effect when determining if the previous test-day SCC was <50,000 cells/ mL. Thereafter, the loss was estimated for records with SCC >100,000 cells/mL. The production (milk, fat, or protein) losses were modeled as the difference between the actual and predicted production (milk, fat, or protein) at the TD of new subclinical mastitis, for 4,382 cow records, and 2,545 cow records after dilution correction. Primiparous cows were predicted to lose 0.31 (0.25-0.37) and 0.28 (0.20-0.35) kg of milk/d at an SCC of 200,000 cells/mL, for unadjusted and adjusted low SCC, respectively. For the same SCC increase, multiparous cows were predicted to lose 0.58 (0.54-0.62) and 0.50 (0.44-0.56) kg of milk/d, respectively. Moreover, it was found that the greater the SCC increase above 100,000 cells/mL, the greater the production losses. The estimated production losses were more precise than previously reported estimates.

Economic effects of bovine mastitis and mastitis management: a review.

Several studies have been published since 1990 on the economics of mastitis and mastitis management. However, hardly any of these studies has discussed the consistency of results with other studies. In the present paper, the economic factors associated with mastitis are explained, providing a framework for economic analysis. As a second step calculations of the costs of mastitis and the costs in relation to the benefits of mastitis management published since 1990 in peer-reviewed journals are extensively reviewed and analysed. The result shows a large variation in the calculated costs and benefits of mastitis and mastitis management between the different studies. Moreover, it is clear that important factors were ignored in some of the studies. The framework provided in this paper can provide a basis for analysis for future studies on the economics of mastitis and mastitis management.