Predicting the time to detect moderately virulent African swine fever virus in finisher swine herds using a stochastic disease transmission model

Background

African swine fever (ASF) is a highly contagious and devastating pig disease that has caused extensive global economic losses. Understanding ASF virus (ASFV) transmission dynamics within a herd is necessary in order to prepare for and respond to an outbreak in the United States. Although the transmission parameters for the highly virulent ASF strains have been estimated in several articles, there are relatively few studies focused on moderately virulent strains. Using an approximate Bayesian computation algorithm in conjunction with Monte Carlo simulation, we have estimated the adequate contact rate for moderately virulent ASFV strains and determined the statistical distributions for the durations of mild and severe clinical signs using individual, pig-level data. A discrete individual based disease transmission model was then used to estimate the time to detect ASF infection based on increased mild clinical signs, severe clinical signs, or daily mortality.

Results

Our results indicate that it may take two weeks or longer to detect ASF in a finisher swine herd via mild clinical signs or increased mortality beyond levels expected in routine production. A key factor contributing to the extended time to detect ASF in a herd is the fairly long latently infected period for an individual pig (mean 4.5, 95% P.I., 2.4 - 7.2 days).

Conclusion

These transmission model parameter estimates and estimated time to detection via clinical signs provide valuable information that can be used not only to support emergency preparedness but also to inform other simulation models of evaluating regional disease spread.

The Risk of Highly Pathogenic Influenza A Virus Transmission to Turkey Hen Flocks Through Artificial Insemination

Artificial insemination is a routine practice for turkeys that can introduce pathogens into breeder flocks in a variety of ways. In this manuscript, a risk analysis on the potential transmission of highly pathogenic avian influenza (HPAI) to naïve hens through artificial insemination is presented. A case of HPAI on a stud farm where the potential transmission of the virus to susceptible hens in the 2015 H5N2 HPAI outbreak in Minnesota is described along with documentation of known and potential transmission pathways from the case. The pathways by which artificial insemination might result in the spread of HPAI to susceptible hens were determined by considering which could result in the 1) entry of HPAI virus onto a premises through semen movement; and 2) exposure of susceptible hens to HPAI as a result of this movement. In the reported case, HPAI virus was detected in semen from infected toms, however, transmission of HPAI to naïve hens through semen is unclear since the in utero infectious dose is not known. This means that the early detection of infection might limit but not eliminate the risk of hen exposure. Because of the numerous potential pathways of spread and the close contact with the birds, it is highly likely that if semen from an HPAI-infected tom flock is used, there will be spread of the virus to naïve hens through insemination. If insemination occurs with semen from stud farms in an HPAI control area, receiving hen farms should have restricted movements to prevent outbreak spread in the event that they become infected.

Exploring Risk for Echinococcosis Spillover in Northern Minnesota Tribal Communities

Echinococcus spp. are zoonotic cestode parasites with a worldwide distribution and a complex, two-host life cycle involving carnivore definitive hosts and small mammal or ungulate intermediate hosts. Surveillance for Echinococcus spp. in the Midwestern United States (USA) is rare. Using a mixed-methods approach, we examined Echinococcus infection risks in wildlife and domestic dogs in four Minnesota Tribal Nations. We hypothesized that the spillover of Echinococcus spp. into domestic dogs would vary with the presence or absence of suspected wildlife host species and certain behaviors associated with domestic dog ownership, like feeding wildlife host carcasses or frequency of veterinary care. Among 83 dogs tested, three (3.6%) were positive for Echinococcus spp. Despite low prevalence, pet owner survey and focus group findings indicated that dogs encounter peri-domestic wildlife most often when they roam freely or consume wildlife carcasses. This study demonstrates a need for further research into spillover potential of endemic zoonotic Echinococcus spp. in the Midwest USA.

Modeling the Transmission of Foot and Mouth Disease to Inform Transportation of Infected Carcasses to a Disposal Site During an Outbreak Event

In the event of a Food and Mouth Disease (FMD) outbreak in the United States, an infected livestock premises is likely to result in a high number of carcasses (swine and/or cattle) as a result of depopulation. If relocating infected carcasses to an off-site disposal site is allowed, the virus may have increased opportunity to spread to uninfected premises and result in exposure of susceptible livestock. A stochastic within-herd disease spread model was used to predict the time to detect the disease by observation of clinical signs within the herd, and the number of animals in different disease stages over time. Expert opinion was elicited to estimate depopulation parameters in various scenarios. Disease detection was assumed when 5% of the population showed clinical signs by direct observation. Time to detection (5 and 95th percentile values) was estimated for all swine farm sizes (500-10,000 head) ranged from 102 to 282 h, from 42 to 216 h for all dairy cattle premises sizes (100-2,000 head) and from 66 to 240 h for all beef cattle premises sizes (5,000-50,000 head). Total time from infection to beginning depopulation (including disease detection and confirmation) for the first FMD infected case was estimated between 8.5-14.3 days for swine, 6-12.8 days for dairy or beef cattle premises. Total time estimated for subsequent FMD cases was between 6.8-12.3 days for swine, 4.3-10.8 days for dairy and 4.5-10.5 days for beef cattle premises. On an average sized operation, a sizable proportion of animals in the herd (34-56% of swine, 48-60% of dairy cattle, and 47-60% of beef cattle for the first case and 49-60% of swine, 55-60% of dairy cattle, 56-59% of beef cattle for subsequent cases) would be viremic at the time of beginning depopulation. A very small fraction of body fluids from the carcasses (i.e., 1 mL) would contain virus that greatly exceeds the minimum infectious dose by oral (4-7x) or inhalation (7-13x) route for pigs and cattle.

Planning "Plan B": The Case of Moving Cattle From an Infected Feedlot Premises During a Hypothetical Widespread FMD Outbreak in the United States

In the event of a foot-and-mouth disease (FMD) outbreak in the United States, "stamping out" FMD infected premises has been proposed as the method of choice for the control of outbreaks. However, if a widespread, catastrophic FMD outbreak in the U.S. were to occur, alternative solutions to stamping out may be required, particularly for large feedlots with over 10,000 cattle. Such strategies include moving cattle from infected or not known to be infected operations to slaughter facilities either with or without prior implementation of vaccination. To understand the risk of these strategies, it is important to estimate levels of herd viremia. Multiple factors must be considered when determining risk and feasibility of moving cattle from a feedlot to a slaughter facility during an FMD outbreak. In addition to modeling within-herd disease spread to estimate prevalence of viremic animals, we explore potential pathways for viral spread associated with the movement of asymptomatic beef cattle (either pre-clinical or recovered) from an infected feedlot premises to offsite harvest facilities. This analysis was proactive in nature, however evaluation of the likelihood of disease spread relative to disease (infection) phase, time of movement, and vaccination status are all factors which should be considered in managing and containing a large-scale FMD outbreak in the United States.

Best practices to optimize utilization of the National Living Donor Assistance Center for the financial assistance of living organ donors

Living organ donors face direct costs when donating an organ, including transportation, lodging, meals, and lost wages. For those most in need, the National Living Donor Assistance Center (NLDAC) provides reimbursement to defray travel and subsistence costs associated with living donor evaluation, surgery, and follow-up. While this program currently supports 9% of all US living donors, there is tremendous variability in its utilization across US transplant centers, which may limit patient access to living donor transplantation. Based on feedback from the transplant community, NLDAC convened a Best Practices Workshop on August 2, 2018, in Arlington, VA, to identify strategies to optimize transplant program utilization of this valuable resource. Attendees included team members from transplant centers that are high NLDAC users; the NLDAC program team; and Advisory Group members. After a robust review of NLDAC data and engagement in group discussions, the workgroup identified concrete best practices for administrative and transplant center leadership involvement; for individuals filing NLDAC applications at transplant centers; and to improve patient education about potential financial barriers to living organ donation. Multiple opportunities were identified for intervention to increase transplant programs' NLDAC utilization and reduce financial burdens inhibiting expansion of living donor transplantation in the United States.

Garbage Management: An Important Risk Factor for HPAI-Virus Infection in Commercial Poultry Flocks

Garbage management represents a potential pathway of HPAI-virus infection for commercial poultry operations as multiple poultry premises may share a common trash collection service provider, trash collection site (e.g., shared dumpster for multiple premises) or disposal site (e.g., landfill). The types of potentially infectious or contaminated material disposed of in the garbage has not been previously described but is suspected to vary by poultry industry sector. A survey of representatives from the broiler, turkey, and layer sectors in the United States revealed that many potentially contaminated or infectious items are routinely disposed of in the trash on commercial poultry premises. On-farm garbage management practices, along with trash hauling and disposal practices are thus key components that must be considered to evaluate the risk of commercial poultry becoming infected with HPAI virus.

Incentives for Bushmeat Consumption and Importation among West African Immigrants, Minnesota, USA

The knowledge, attitudes, and practices surrounding bushmeat consumption and importation in the United States are not well described. Focus groups of West African persons living in Minnesota, USA, found that perceived risks are low and unlikely to deter consumers. Incentives for importation and consumption were multifactorial in this community.

The effect of estrogen on muscle damage biomarkers following prolonged aerobic exercise in eumenorrheic women

This study assessed the influence of estrogen (E₂) on muscle damage biomarkers [skeletal muscle - creatine kinase (CK); cardiac muscle - CK-MB] responses to prolonged aerobic exercise. Eumenorrheic women (n=10) who were physically active completed two 60-minute treadmill running sessions at ∼60-65% maximal intensity during low E₂ (midfollicular menstrual phase) and high E₂ (midluteal menstrual phase) hormonal conditions. Blood samples were collected prior to exercise (following supine rest), immediately post-, 30 min post-, and 24 hours post-exercise to determine changes in muscle biomarkers. Resting blood samples confirmed appropriate E₂ hormonal levels Total CK concentrations increased following exercise and at 24 hours post-exercise were higher in the midfollicular low E₂ phase (p<0.001). However, CK-MB concentrations were unaffected by E₂ level or exercise (p=0.442) resulting in the ratio of CK-MB to total CK being consistently low in subject responses (i.e., indicative of skeletal muscle damage). Elevated E₂ levels reduce the CK responses of skeletal muscle, but had no effect on CK-MB responses following prolonged aerobic exercise. These findings support earlier work showing elevated E₂ is protective of skeletal muscle from exercise-induced damage associated with prolonged aerobic exercise.

Changing Cultural and Social Environments: Implications for Older East Asian Women

The world is aging and the trend is towards a global feminization of aging. In the Asia Pacific region, which already contains approximately 50% of the world's population over age 60, the number of older women exceeds that of older men in most countries. This article explores the changes that are occurring in East Asian social and cultural traditions for aging and discusses the implications of those changes for women who aged in that culture. In the traditional culture, Chinese, Japanese, and Korean families are influenced by values of family centrality and collective orientation to life that are mostly rooted in Confucian values and ethics. In those traditions, older women assume and maintain a valued status within the family and community through respected roles and productive contributions. However, various factors, such as migration to urban areas and demographic shifts, have precipitated modernization of these societies and alterations of traditional culture. These cultural shifts are relevant to the United States where, according to the 2000 U.S. Census, 71.0% of Asian and Pacific Islander-Americans over the age 65 are foreign-born. Immigration can prompt an immediate cultural shift and create a fast forward insight into the slower cultural evolution currently occurring in East Asian societies.

[Biomechanics and injury prevention in road traffic]

The main predicting factor for the injury severity is "speed". This fact is predominantly important with regard to the protection of pedestrians and two wheelers. Today's safety features such as new steering and breaking systems, car body construction, seat belts, head restraints and crash helmets etc. let us sometimes overlook the hazards on the road. However, further improvements can be expected from advanced restraint system combinations, reinforced frontal and lateral car structures and padding, perhaps side air bags and automatically adjusted head restraint systems. Collision reconstruction and assessment of causality are needed, e.g., in cases of soft tissue neck injuries, questionable overrunning, walking direction of impacted pedestrians, uncertain belt or helmet wearing etc. Considerable legal problems arise if the causality is judged only from clinical point of view while the important criterion of collision mechanics is not taken into account in acceptable quantitative detail. Therefore it is recommended that determining the causality of a mechanical event should be left to specially trained professionals.

Quantitative autoradiography reveals selective changes in cerebellar GABA receptors of the rat mutant dystonic

In the rat mutant dystonic (dt), glutamic acid decarboxylase (GAD) activity in the deep cerebellar nuclei (DCN) is elevated compared to normal littermates. The distribution of this increase within the DCN, and the effect upon GABA receptor density, was assessed in 25-d-old animals. GAD activity was increased 45, 41, and 74% in the medial, interpositus, and lateral divisions of the DCN, respectively. Autoradiographic analysis of GABAA receptor density, using the ligand 3H-muscimol (MUSC), revealed a significant decrease in MUSC binding in the DCN of the mutant. No changes in the binding of the benzodiazepine ligand 3H-flunitrazepam (FLU) were found in the DCN. At 18 other sites, including motor areas in the brain stem, midbrain, and forebrain, no significant changes were found in either MUSC or FLU binding. There also was a failure to find any significant changes in dt animals in the binding of ligands which label the muscarinic cholinergic receptor, dopamine D2 receptor, or serotonin 5-HT2 receptor. The results support earlier findings that GABAergic activity is increased in Purkinje cell terminals of the dt mutant and suggest that in response to this enhanced activity, GABA receptors in the DCN are down-regulated. At other levels of the neuraxis no consistent changes were found in any of the variables studied, suggesting that cerebellar dysfunction may be a primary component of the dystonic syndrome.