The applicability of species sensitivity distributions to the development of generic doses for phytosanitary irradiation.

Ionizing radiation is used as a phytosanitary treatment to prevent the introduction of pests through trade. Generic doses are a valuable means to increase the number of pest-commodity combinations that can be treated using phytosanitary irradiation. Generic doses allow for the treatment of the entire taxa for which the dose has been approved, allowing for the treatment of untested species. As such, the approval of a generic dose requires substantial supporting data and careful consideration of the risks involved. We adopt the Species Sensitivity Distribution (SSD) framework, already in widespread use in the field of ecotoxicology and environmental risk assessment, to evaluate generic doses for phytosanitary irradiation treatments. Parametric SSDs for Curculionidae and Tephritidae were developed using existing data on efficacious phytosanitary irradiation treatments. The resulting SSDs provided estimates of the taxa coverage expected by the generic dose, along with the margin of uncertainty. The SSD analysis lends support to the existing 150 Gy generic dose for Tephritidae and a proposed 175 Gy generic dose for Curculionidae. The quantitative estimates of risk produced by the SSD approach can be a valuable tool for phytosanitary rule making, improving the process for generic dose development and approval.

Investigation of risk factors for introduction of highly pathogenic avian influenza H5N1 virus onto table egg farms in the United States, 2022: a case-control study.

Introduction: The 2022-2023 highly pathogenic avian influenza (HPAI) H5N1 outbreak in the United States (U.S.) is the most geographically extensive and costly animal health event in U.S. history. In 2022 alone, over 57 million commercial and backyard poultry in 47 U.S. states were affected. Over 75% of affected poultry were part of the commercial table egg production sector. Methods: We conducted a case-control study to identify potential risk factors for introduction of HPAI virus onto commercial table egg operations. Univariate and multivariable analyses were conducted to compare farm characteristics, management, and biosecurity factors on case and control farms. Results: Factors associated with increased risk of infection included being in an existing control zone, sightings of wild waterfowl, mowing or bush hogging vegetation less than 4 times a month, having an off-site method of daily mortality disposal (off-site composting or burial, rendering, or landfill), and wild bird access to feed/feed ingredients at least some of the time. Protective factors included a high level of vehicle washing for trucks and trailers entering the farm (a composite variable that included having a permanent wash station), having designated personnel assigned to specific barns, having a farm entrance gate, and requiring a change of clothing for workers entering poultry barns. Discussion: Study results improve our understanding of risk factors for HPAI infection and control measures for preventing HPAI on commercial U.S. table egg farms.

Investigation of risk factors for introduction of highly pathogenic avian influenza H5N1 infection among commercial turkey operations in the United States, 2022: a case-control study.

Introduction: The 2022-2023 highly pathogenic avian influenza (HPAI) H5N1 outbreak in the United States (U.S.) is the largest and most costly animal health event in U.S. history. Approximately 70% of commercial farms affected during this outbreak have been turkey farms. Methods: We conducted a case-control study to identify potential risk factors for introduction of HPAI virus onto commercial meat turkey operations. Data were collected from 66 case farms and 59 control farms in 12 states. Univariate and multivariable analyses were conducted to compare management and biosecurity factors on case and control farms. Results: Factors associated with increased risk of infection included being in an existing control zone, having both brooders and growers, having toms, seeing wild waterfowl or shorebirds in the closest field, and using rendering for dead bird disposal. Protective factors included having a restroom facility, including portable, available to crews that visit the farm and workers having access and using a shower at least some of the time when entering a specified barn. Discussion: Study results provide a better understanding of risk factors for HPAI infection and can be used to inform prevention and control measures for HPAI on U.S. turkey farms.

Effectiveness of Hot-Water Immersion Against Brevipalpus yothersi (Acari: Tenuipalpidae) as a Postharvest Treatment for Lemons.

Citrus leprosis is a destructive disease of citrus caused by several viruses (CiLVs) that are quarantine pests in the United States. Brevipalpus yothersi Baker (Acari: Tenuipalpidae) vectors the most virulent strain of CiLV. This mite is present in the United States and could facilitate the spread of the disease if CiLV reaches the country. Postharvest treatments could mitigate B. yothersi on imported commodities from areas where CiLV exists. The current study explores the effectiveness of hot-water immersion as a postharvest treatment against B. yothersi. Lemons were immersed in water at 21, 48, 53, or 63°C for 5, 10, and 15 min. Immersions at 53 and 63°C for all time schedules dislodged over 99% of adult mites. Lemon fruit quality and B. yothersi egg viability after hot-water immersion were also evaluated. Fruit quality significantly decreased in lemons treated at 63°C resulting in decay (grade 3, rejection), while at 53°C there was a quality reduction (grade 2, minimum acceptable market level) compared to lemons immersed at 21°C or nontreated controls (grade 1). None of the eggs hatched when the lemons were immersed in water at 63°C and an average of 1.5% hatched at 53°C for all time schedules. Immersion in water at 53°C for 5 min dislodged 99.71% and 57.14% of adult and immature mites, respectively, and resulted in 98.11% unhatched eggs without significant fruit quality reduction. Hot-water immersion could be a key component in a systems approach to control B. yothersi on imported citrus fruits from countries where citrus leprosis is present.

Critical PO2 as a diagnostic biomarker for the effects of low-oxygen modified and controlled atmospheres on phytosanitary irradiation treatments in the cabbage looper Trichoplusia ni (Hübner).

BACKGROUND: Phytosanitary irradiation is a sustainable alternative to chemical fumigants for disinfesting fresh commodities from insect pests. However, irradiating insects in modified atmospheres with very low oxygen (<1 kPa O2 ) has repeatedly been shown to increase radioprotective response. Thus, there is a concern that modified atmosphere packaging could reduce the efficacy of phytosanitary irradiation. One hurdle slowing the widespread application of phytosanitary irradiation is a lack of knowledge about how moderate levels of hypoxia relevant to the modified atmosphere packaging of most fresh commodities (3-10 kPa O2 ) may affect phytosanitary irradiation treatments. Therefore, we hypothesize that critical PO2 (Pcrit ), the level of oxygen at which an insect's metabolism becomes impaired, can be used as a diagnostic biomarker to predict the induction of a radioprotective response. RESULTS: Using the cabbage looper Trichoplusia ni (Hübner), we show that there is a substantial increase in radiation resistance when larvae are irradiated in atmospheres more hypoxic than their Pcrit (3.3 kPa O2 ). These data are consistent with our hypothesis that Pcrit could be used as a diagnostic biomarker for what levels of hypoxia may induce radioprotective effects that could impact phytosanitary irradiation treatments. CONCLUSION: We propose that the relationship between Pcrit and radioprotective effects could allow us to build a framework for predicting the effects of low-oxygen atmospheres on the efficacy of phytosanitary irradiation. However, more widespread studies across pest species are still needed to test the generality of this idea.

Deleterious effects of electron beam irradiation on development and reproduction of tomato/potato psyllids, Bactericera cockerelli.

The potato/tomato psyllid Bactericera cockerelli causes serious damage to several solanaceous crops by direct feeding and vectoring Candidatus Liberibacter solanacearum, a bacterial pathogen. Electron beam (eBeam) irradiation is an environmentally friendly, chemical-free alternative method that is increasing in use for disinfestation of insect pests. We hypothesize that this irradiation technology will have detrimental effects on potato psyllid and thus impede its disease vectoring. To this end, we explored the effects of eBeam treatment ranging from 50 to 500 Gy on survival, development and reproduction of this pest. Impact on psyllids was apparently dose-dependent. When irradiated at 350 Gy, eggs could not hatch, 1st instar nymphs failed to emerge, and although a small portion of irradiated 5th instar nymphs survived, the emerged adults were mostly deformed. Abnormality in eclosed adults suggests harmful effects of eBeam on metamorphosis. Reproduction was seriously impaired when female psyllids were exposed to eBeam at the 5th instar nymphal or young adult stage, presumably due to inability to form oocytes. In addition, reciprocal crosses between irradiated and untreated psyllids indicated that female psyllids were more radiosensitive than males to eBeam. Taken together, these findings indicate that eBeam negatively impacted potato psyllid development and reproduction, which would inevitably compromise its disease transmission capacity. A dose of 350 Gy can be considered as a reference dose for effective control of potato psyllids.

Case Series of Turkey Farms from the H5N2 Highly Pathogenic Avian Influenza Outbreak in the United States During 2015.

Between December 2014 and June 2015, an outbreak of H5N2 HPAI caused the largest and most expensive agriculture emergency in U.S. Department of Agriculture-Animal and Plant Health Inspection Service history. The outbreak affected 21 states; 232 poultry farms (211 commercial and 21 backyard) were affected, and approximately 49.6 million birds were depopulated on poultry farms. The majority of affected farms were commercial turkey operations (n = 160). This report is a case series describing 104 H5N2 HPAI-affected turkey farms in Iowa, Minnesota, Missouri, North Dakota, South Dakota, and Wisconsin that had H5N2 HPAI virus detected between March 5 and June 1, 2015. The farm manager or farm personnel voluntarily completed an epidemiologic questionnaire administered by state and federal animal health officials. Equipment and vehicle sharing with other farms was common, particularly for feed trucks (77% of farms shared feed trucks with other farms), live haul loaders (90.4%), poult trailers (72.0%), and preloaders (80.7%). Many farms had water bodies in proximity to the farm, such as a pond (42.6%) or stream (21.8%). About one-third of farms (33.7%) reported seeing wild birds inside the turkey barns. Only 44.2% of farms reported that third-party biosecurity audits or assessments had been conducted. Because the newly introduced Asian H5N8 HPAI and two new HPAI viruses, H5N2 and H5N1, are now circulating in U.S. wild birds, primarily migratory waterfowl, a greater potential for reoccurrence exists with the spring and fall migratory seasons, representing higher risk periods for outbreaks of HPAI in commercial poultry farms in the future. Eliminating exposure to wild birds, especially waterfowl or environments contaminated by wild waterfowl, will reduce risk of reintroduction of H5N2 HPAI virus, and ensuring good on-farm biosecurity will help the poultry industry avoid introduction of influenza and lateral spread between farms.

A Porcine Epidemic Diarrhea Virus Outbreak in One Geographic Region of the United States: Descriptive Epidemiology and Investigation of the Possibility of Airborne Virus Spread.

This study describes a spring 2013 outbreak of porcine epidemic diarrhea virus (PEDv), using data from 222 swine sites in 14 counties area in 4 contiguous states in the United States. During the outbreak, the premises-level incidence of PEDv was 40.5 percent (90/222 sites). One of the three companies from which data were collected had a lower incidence (19.5 percent) than the other two companies (41.1 and 47.2 percent). Sow sites had the highest incidence of PEDv during the outbreak (80.0 percent). Spatial analysis showed that PEDv was clustered rather than randomly distributed, which suggested that sites near a positive site had increased risk of acquiring PEDv infection. Meteorological data were used to investigate the hypothesis that PEDv was spread by air. If airborne dissemination played a role in this outbreak, we would expect the direction of disease spread to correlate with the predominant wind direction. Two methods were used to determine the direction of disease spread--linear direction mean analysis in ArcGIS and the direction test in ClusterSeer. The former method indicated PEDv spread was south to slightly southwest, and the latter indicated spread was to the southeast. The predominant wind direction during the month of the outbreak was toward the south, with some southeast and southwest winds; the strongest wind gusts were toward the southwest. These findings support the hypothesis that PEDv was spread by air. The results, however, should be interpreted cautiously because we did not have information on direct and indirect contacts between sites, such as movement of trucks, feed, pigs or people. These types of contacts should be evaluated before pathogen spread is attributed to airborne mechanisms. Although this study did not provide a definitive assessment of airborne spread of PEDv, we believe the findings justify additional research to investigate this potential mechanism of transmission.

Factors affecting use of veterinarians by small-scale food animal operations.

OBJECTIVE: To identify factors associated with use of a veterinarian by small-scale food animal operations. DESIGN: Cross-sectional descriptive survey. SAMPLE: 16,000 small-scale farm or ranch operations in all 50 states. PROCEDURES: Surveys were conducted via mail or telephone during 2011 for small-scale operations (gross annual agricultural sales between $10,000 and $499,999) in which an animal or animal product comprised the highest percentage of annual sales. RESULTS: 8,186 (51.2%) operations responded to the survey; 7,849 surveys met the inclusion criteria. For 6,511 (83.0%) operations, beef cattle were the primary animal species. An estimated 82.1% of operations (95% confidence interval [CI], 81.1% to 83.0%) had a veterinarian available ≤ 29 miles away; 1.4% (95% CI, 1.2% to 1.7%) did not have a veterinarian available within 100 miles of the operation. Operations for which the nearest veterinarian was ≥ 100 miles away or for which a veterinarian was not available were located in 40 US states. Overall, 61.7% of operations (95% CI, 60.6% to 62.9%) had used a veterinarian during the 12 months prior to the survey. Producers with college degrees were significantly more likely to use a veterinarian (675%) versus those who did not complete high school (52.9%). CONCLUSIONS AND CLINICAL RELEVANCE: Results of this study indicated most small-scale operations had adequate access to veterinarians during 2011, but there seemed to be localized shortages of veterinarians in many states.