Royal GD (Netherlands)

• Hybrid within-farm model combines detailed agent dynamics with compartmental efficiency • Simulates disease spread through movement of people and animals • Model uses ABC-SMC for reliable parameter estimation with scarce data • Evaluates biosecurity interventions using swine influenza A virus as a case study. Effective prevention of pathogen transmission through biosecurity practices is vital for maintaining pig health and productivity. This study presents HogDSim, a novel within-farm model for farrow-to-finish pig farms. The model incorporates epidemiological scenarios that account for farm structure and pathogen spread via both animal and farmer movement. Farmer mobility is tracked using Bluetooth®-enabled personal beacons and detection points, allowing high-resolution monitoring of human-mediated transmission routes. We demonstrate the model using swine influenza A virus (swIAV) as a case study in a single farrow-to-finish farm. Transmission parameters were calibrated via Approximate Bayesian Computation Sequential Monte Carlo across scenarios with varying data availability, where synthetic infection data were generated from literature-based swIAV parameters. Additionally, we offer a concise demonstration of the model’s application in evaluating biosecurity measures. HogDSim is a modular framework for simulating within-farm disease dynamics. It integrates epidemiological processes, animal and farmer movements, an auxiliary transmission route, and modules for detection and ABC-SMC calibration. Using swIAV as a case study, we show that calibration from fattening-area observations can recover main transmission pathways, although auxiliary-route parameters remain difficult to identify under sparse surveillance. While demonstrated on swIAV, the framework is adaptable to diverse pathogens, biosecurity strategies, and farm configurations, supporting reproducible scenario comparison.

Depending on the plasma frequencies and the radar frequency, plasmas may become impenetrable for radar waves. This paper describes different modeling strategies when the permittivity of the plasma is negative.

Respiratory tract infections remain a major challenge in cattle production, particularly in calves, but increasingly in adult dairy cows. Over the past decade, outbreaks of fatal Mannheimia haemolytica fibrinous pleuropneumonia (FPP) emerged in dairy herds in the Netherlands, with similar occurrences reported in other countries. The objective of this case-referent study was to describe the characteristics of these outbreaks and the circumstances under which they occur. For this purpose, 50 dairy farmers who had submitted a cow with a confirmed M. haemolytica FPP necropsy diagnosis participated in a telephone survey and provided farm data for analysis. The findings at herd level were compared with the national reference population (average Dutch dairy herd) and those at cow level, with ±1,700 necropsies routinely submitted during the study period January 2019 to March 2021. Most cases were part of larger outbreaks of FPP on the submitting farm. Before the onset of clinical signs, the case cows were average performing, healthy, and otherwise unremarkable cows; age and production were average, and all were in normal to good condition and in middle to late lactation. All necropsied case cows were more than 30 d postpartum. The vast majority of case cows showed no signs of other diseases that could have triggered M. haemolytica FPP; 18% had not received any medication preceding the clinical signs of FPP, and the remaining cows had on average a medication-free period of 4 mo before they became severely ill or died. The median outbreak duration, morbidity, and mortality were respectively 30 d, 6.3%, and 1.8%. Eighty-two percent of the index case cows died, most likely because the nonspecific clinical signs were recognized too late as M. haemolytica FPP, as the median overall case-fatality risk was 33%. In 40% of the cases, the necropsy report diagnosing M. haemolytica FPP was the first the farmer knew of M. haemolytica involvement in these animals. Early recognition and confirmation of the diagnosis appeared essential to decrease the mortality risk of M. haemolytica FPP. The FPP cows originated from farms with an average milk production level per cow, but with an above-average herd size and farming intensity (kg milk/ha). Moreover, these farms were more likely to introduce cattle from other farms (48% of the case farms introduced cattle in the month preceding the onset of the outbreak), often imported animals from other countries and showed less-favorable herd-health certification statuses for infectious bovine rhinotracheitis virus, bovine viral diarrhea virus, and Leptospirosa hardjo. The majority of outbreaks occurred in the winter season or after a week with increased relative humidity. At farm level, the results suggest stressors, inadequate biosecurity (purchase of cattle), and housing as risk factors for these outbreaks. Although M. haemolytica FPP appears to be a multifactorial disease, the results also seem to indicate a primary infectious disease pattern of fatally affecting healthy dairy cows at random. Further research is needed to quantify the relative importance of risk factors and identify specific virulent factors in the isolated M. haemolytica strains.

Since 2018, Dutch dairy farmers have been obliged to opt for 1 of 4 routes to achieve bovine viral diarrhea virus (BVDV) freedom in the national BVDV eradication program. This observational study evaluated efficacy of the total BVDV program using indicators such as the number of persistently infected (PI) cattle, the percentage of dairy herds with a BVDV-free status, and the percentage of BVDV-free dairy herds with evidence of introduction of BVDV, as well as a cost calculation per route. The Dutch BVDV program appeared to be successful, as the percentage of BVDV-free dairy herds increased from 59% at the start of the program to 89% by the end of 2023. The number of PI detected each quarter declined from 500 PI in the third quarter of 2019 to 83 PI in the last quarter of 2023. The percentage BVDV-free dairy herds with evidence of (re)introduction of BVDV decreased from 1.29% per quarter in the first year of the mandatory program to 0.25% per quarter by the end of 2023. In Europe, BVDV control program designs are often tailored to the country's specific situation, such as the prevalence at the start of eradication, risk profile of a country or herd, desired speed of eradication, and available funds. These results show that the Dutch approach, in which multiple routes can be followed toward BVDV freedom, is successful.

Avian influenza (AI) is a highly contagious zoonotic disease primarily affecting birds with clinical manifestation depending on bird species and virus subtype. Globally, outbreaks have had a large socioeconomic impact. Moreover, highly pathogenic AI virus (HPAIv) outbreaks can pose a public health risk. Detection of AIv, particularly HPAIv, mainly relies on passive surveillance, risking underreporting and delayed detection. This study describes and compares the contribution of passive and active surveillance components on HPAI detection in poultry flocks in years with different HPAIv introduction risk (free, seasonal outbreaks, and year round) in the Netherlands. We drafted a flowchart representing the flow of information and samples between farmers and veterinarians, the competent authority (CA), the national reference lab (NRL), and the private organization Royal GD and identified four different surveillance components and derived the use of each of these components during 2016 (reference), 2019 (low risk), and 2022 (high risk). The first component, "notification of suspicion," where farmers and veterinarians directly report suspicions to the CA, accounted for 88.4% of farm visits and detected 98.1% of all HPAIv outbreaks. The second component, "testing to exclude" (TTE), consisting postmortem/sample submission and contact with the veterinary helpdesk of GD detected 2% of the cases in 2022. The third and active surveillance component, "protection zone screening," screens farms closely to a positively detected farm. No outbreaks were detected, suggesting limited between-farm transmission. The last and active surveillance component, mandatory national serological surveillance detected two low pathogenic AI outbreaks. Analysis between years for the passive surveillance components "notification of suspicion" and "TTE," using chi-square test of independency and odd ratios, showed increased use and farm visits in the high-risk year. However, postmortem-related submissions for TTE were increased in the disease-free year. All components combined detected HPAI or provided valuable information across different risk periods.

ABSTRACT Mycoplasma gallisepticum (Mg) and Mycoplasma synoviae (Ms) are regarded as the most important avian mycoplasma species for today’s chicken and turkey farming industry from clinical and economical perspectives. Control strategies for Mg and Ms have become more efficient due to investments in mycoplasma research over the last 70 years. These investments have contributed to the further implementation of serological and molecular testing, the development of vaccines, and the improvement of antimicrobial treatment strategies. However, the increasing spotlight on welfare, the pressure on prudent use of antimicrobials, and the expected global increase in poultry production, are going to have an impact on the future control of avian mycoplasmas in commercial poultry. In this paper a group of avian mycoplasma experts discuss the future challenges in mycoplasma control considering the background of these expected changes and the relevance for future avian mycoplasma research.

ABSTRACT Beside biosecurity, vaccination is important for Mycoplasma synoviae (MS) control as it has been shown to contribute to the reduction of economic impact and, experimentally, also lessens horizontal transmission. In this study, the effect of MS live vaccination on horizontal transmission was quantified under field conditions by analysing 4-year MS monitoring data from non-MS-vaccinated broiler and layer breeders and MS-vaccinated broiler breeders with good biosecurity in single-age housing systems. Flocks were monitored at 20 and 30 weeks of age and every 12 weeks thereafter. At every sampling, 60 blood samples or 24 tracheal swabs were tested using rapid plate agglutination test and ELISA serially or MS DIVA PCR, respectively. The MS incidence rate was calculated and the association with vaccination was analysed by logistic regression. The average MS incidence rate per 1000 weeks was 11.6 cases for non-MS-vaccinated broiler breeders and decreased from 29.6 to 5.6 cases with successive vaccinated production cycles. In non-MS-vaccinated layer breeders it was 3.6. A significant negative association with MS incidence was found after vaccinating four to six successive production cycles compared to non-MS-vaccinated or only one production cycle vaccinated breeders (odds ratio (OR) = 0.23, P = 0.05 & OR = 0.12, P = 0.01, respectively). A significant negative association with MS in non-MS-vaccinated layer breeders (OR = 0.29, P = 0.00) was observed compared to non-MS-vaccinated broiler breeders, possibly due to more controlled contact structures within the layer breeder industry. The results suggest that vaccination and control of contacts contribute to the reduction of between-farm MS transmission.

Simple SummaryLameness in dairy cattle is mainly caused by affection of the under feet. This affection can be caused by an infection of the skin (e.g., digital dermatitis or interdigital phlegmon) or by non-infectious claw horn lesions (e.g., sole ulcers, white line lesions, or toe necrosis). The latter of these are sometimes infected secondarily by environmental bacteria like Spirochetes, and those lesions were for many years considered to be non-healing and responsible for the premature culling of dairy cows. In a clinical pilot study with a one-group post-test-only design, dairy cows with such infected claw horn lesions were claw trimmed, topically treated, and additionally injected with tilmycosin parenterally. A follow-up after 3 months showed not only a better cure, but also an almost normal locomotion and better production, even in comparison with non-affected herd mates.Non-healing claw horn disorders are a serious problem in dairy herds because of the long duration of the disorder and the chronic pain derived from it, seriously affecting animal welfare and causing decreased production and premature culling from the herd. In a clinical trial, 40 cows in 13 herds (12 dairy herds and 1 herd with cow–calf operations) with toe necrosis (TN, 27x) or a non-healing white line disorder (NHWLD, 13x) were treated topically with an unguent-containing zinc sulphate and acetyl acid in combination with a parenteral injection of tilmycosin. An evaluation was conducted 3 months after treatment using locomotion scoring (LS), a clinical observation of the lesion, and the lactation value (the lactation value is the Net Profit of the individual animal divided by the average Net Profit of the entire herd. The mean is 100, so >100 is related to better production (combination of kg milk, %fat, and protein)) (LV) before and after treatment. The mean LS improved significantly from 4.0 (SD: 0.2) before treatment to 1.2 (SD: 0.4) 3 months after treatment (p < 0.001). The clinical presentation showed that all of the cows were cured from horn shoe infection (both TN and NHWLD). The LVs of the treated cows increased significantly from 111.2 (SD: 12.2) to 116.8 (SD: 15.1; p = 0.003).