Epidemiologic aspects of infectious agents involved in reproductive inefficiency in swine

First litter gilts (N = 210) in 15 herds were monitored through their first gestation. Prevalence of 6 infectious agents associated with reproductive failure was estimated in the sow and finisher populations in each herd. The association between reproductive failure and infection, as determined by a ≥4-fold increase in antibody titer, was determined. Farrowing ≥3 stillborn pigs, farrowing ≥3 mummified fetuses, and farrowing ≤6 live pigs were statistically associated with seroconversion to infectious agents;The sensitivity, specificity, and diagnostic titer of the microtiter serum neutralization test (SN) for the diagnosis of encephalomycarditis virus was determined. Antibody titers up to 1:8 were observed in uninfected animals and ranged from 1:5.7 to 1:1024 in infected animals. SN antibody titers of 1:8 were highly suggestive of infection, with an estimated 97.8 % sensitivity and 95.7 % specificity at this dilution. Antibody titers of 1:16 or greater were conclusive for EMCV infection, based on a test specificity of 100% at these dilutions;A total of 2614 animals from 104 herds located throughout the state of Iowa were tested for antibodies against EMCV. A difference (P \u3c 0.002) was observed between the prevalence in sows and gilts (17.2%) vs. finishing animals (12.2%). Breeding swine in total confinement (20.5%) showed a higher prevalence (P = 0.04) than breeders in other types of housing (12.1%), while the prevalence in finishing animals raised in total confinement (6.4%) was lower (P = 0.02) than finishers not raised in total confinement (13.6%). No association was detected between prevalence and herd size, or prevalence and season of the year. The true prevalence of EMCV in Iowa swine was estimated to be 13.8% in breeding stock and 8.5% in finishing animals. On a herd basis, 89.4% (93/104) of the herds had one or more EMCV-positive animals. These animals were also tested against for antibodies against Toxoplasma gondii by ELISA. The true prevalence of toxoplasmosis was estimated as 5.4% among finishing swine and 11.4% among sows and gilts. Herds with fewer than 100 breeders were more likely to be infected than herds with 100 or more breeders (P \u3c 0.05). Seropositivity in breeding stock was approximately the same in infected herds, regardless of herd size. Herds with finishers in total confinement were as likely to become infected as herds with other types of facilities, but infected herds with finishers in confinement appeared to have a lower in-herd prevalence than herds with other types of facilities (P = 0.09). No seasonal effects were observed and prevalence remained relatively constant throughout the year

Susceptibility of Swine to Hepatitis E virus and its Significance to Human Health

Previous reports indicate that swine can be experimentally infected with Asian isolates of human hepatitis E virus (HEV), which supports epidemiological data indicating that domestic swine can serve as a reservoir for the virus in parts of Asia and as such have the potential to transmit the virus to humans by the fecal-oral route or through contact with pork products. The increasing incidence of human HEV infections in the western hemisphere raises the question of whether or not pigs can play a role in the transmission of this virus in the Americas. Accordingly the susceptibility of swine to a New World isolate of the human hepatitis E virus, Mexico 14, was evaluated. No evidence of infection was detected in experimental pigs. However a high herd and individual prevalence rate for seroreactivity to recombinant HEV antigen was detected in Iowa swine during the selection of experimental pigs. These observations suggests that swine vary in their susceptibility to human HEV isolates. Whether or not swine are susceptible to other New World isolates of HEV and can serve as a reservoir for human infection remains to be determined. The significance of the high rate of seroreactivity of swine to recombinant antigen with respect to human and swine health is not known. An epidemiological study currently in progress should help answer this important question

Field-Based Assessment of the Role of Porcine Cytomegalovirus in Respiratory Disease of Nursery Pigs

Porcine cytomegalovirus (PCMV) is an ubiquitous infectious agent in swine population throughout the world. Field and some experimental observations have suggested that PCMV plays an important role in causing or enhancing respiratory and/or reproductive disease of swine. However, no actual measure of this has been documented. As the first step in assessing the economic significance of PCMV infection for swine herds in the United States, a field-based case-control study was conducted to evaluate the potential role of the virus in respiratory disease of young swine. The data in this study, thus far, suggest that there may be an association between PCMV infection and increased risk of respiratory disease development in nursery pig populations and that, as was expected, PCMV infection is a common finding among nursery pigs. In an era in which multifactorial respiratory disease and associated decrease in production efficiency is such a large concern, it may be prudent to consider PCMV when developing and implementing strategies for production management and pig flow

Effect of Feed Cost on the Economic Impact of PRRS

Economic impacts based on PRRS associated losses as reported in a previous study were modeled with varying grain prices. Sensitivity tables show that as grain (feed) prices rise, the economic impact of disease events increases. As corn prices rise from $2.25/bu up to$5.00/bu, there is a $92.6 million increase in the cost of PRRS to US pork producers. Every$0.50/bu increase in corn price costs the pork industry $18.52 million in PRRS associated losses. In the PRRS-affected farm, for every$0.50/bu increase, the cost per litter increases $0.886, the cost per nursery pig increases$0.072/hd and the cost per finisher pig increases $0.405/hd. With corn at$2.50 to $5.00/bu the national impact is estimated at$594.19 to $686.77 million annually, or$5.94 to $6.87/hd marketed in the US. As feed prices rise, the value of improved health care also rises. As costs rise, it is imperative to continue efforts on disease control and prevention

Shedding of PRRS Virus in Milk and Colostrum

Porcine reproductive and respiratory virus (PRRSV) is endemic in many swine herds. The means by which PRRSV continues to circulate in herds is not well understood. Under experimental conditions, we found that PRRSV is shed in the milk and colostrum of infected dams. Virus-contaminated mammary secretions could play an important role in virus transmission in endemically infected herds

Effects of Dietary Echinacea purpurea on PRRSV-infected Nursery Pigs

The effect of dietary additions of Echinacea purpurea on the rate of rate of growth, viremia, and ontogeny of the humoral antibody response against porcine reproductive and respiratory syndrome virus (PRRSV) infection was evaluated in weaned pigs. In three replicates, weaned pigs (18 ± 1 day of age) from a PRRSV-naïve herd were randomly allotted to one of four pens (diets) in two rooms, each pen containing five pigs. Each pen of pigs (pens) began one of four dietary treatments 1 week before inoculation with PRRSV: 1) basal ration plus carbadox (0.055 g/kg); 2) basal ration plus Echinacea I (2% of the total ration); 3) basal ration plus Echinacea II (4% of the total ration); and 4) basal ration composed of corn, soybean meal, whey, and supplemented essential vitamins and minerals. E. purpurea was purchased in powder form and determined by chemical analysis to contain 1.35% cichoric acid. Seven days after starting the diets (day 7), all pigs in one room were intranasally inoculated with PRRSV isolate ATCC VR-2332 at a concentration of 10 4 TCID50 /ml. To monitor the effects of diet and PRRSV infection, body weight and blood samples were collected from all pigs at 7-day intervals (day 0 to 42). Serum samples were analyzed for the presence of PRRSV and PRRSV-specific antibodies. All inoculated pigs become infected with PRRSV and all uninoculated pigs remained free of infection. PRRSV-infected pigs had a lower percentage increase in body weight between day 7 and 42 compared with uninfected animals (P\u3c0.06). There were no differences in body weight, average daily gain (ADG), average daily feed intake (ADFI), or gain:feed ratio (G:F) in PRRSV-infected compared with uninfected animals. Animals receiving diets supplemented with Echinacea (treatments 2 and 3), no differences were observed in percentage increase in body weight, ADG, ADFI, and G:F ratio in either the PRRSV-infected and the uninfected pigs. Among PRRSV-infected animals, dietary Echinacea did not affect the rate or level of the ELISAdetectable antibody response day 7 to 42 or the level and duration of PRRSV in serum. Under the conditions of this study, dietary Echinacea did not reverse the growthinhibiting effects of PRRSV, did not exhibit antiviral effects and did not show any evidence of immunostimulatory properties

Double Exposure Materials: Simulation Study of Feasibility

Double patterning and double exposure techniques have been proposed as possible methods for reducing half pitch resolution below k1=0.25. Both methods have the potential to reduce the theoretical lithographic half pitch to k1=0.125. Double patterning is a process-intensive method that requires multiple coat, develop, and etch steps to achieve the low k1 imaging. Double exposure processes have been proposed that do not require multiple coat, develop, or etch steps. Potentially, double exposure processes will have a lower cost of ownership that double patterning. However, double exposure materials have not yet been proven to work experimentally. Before applying significant effort to develop double exposure materials, their feasibility can be determined using rigorous simulation techniques. This work presents a feasibility study of four types of double exposure materials and their potential process windows

Materials modeling and development for use in double-exposure lithography applications

The current optical photolithography technology is approaching the physical barrier to the minimum achievable feature size. To produce smaller devices, new resolution enhancement technologies must be developed. Double-exposure lithography has shown promise as a potential pathway that is attractive because it is much cheaper than double-patterning lithography and can be deployed on existing imaging tools. However, this technology is not possible without the development of new materials with nonlinear response to exposure dose. The performance of existing materials such as reversible contrast enhancement layers (rCELs), and theoretical materials such as intermediate state two-photon (ISTP) and optical threshold layer (OTL) materials in double-exposure applications have been investigated through computer simulation. All three materials yielded process windows in double-exposure mode. OTL materials showed the largest process window (depth of focus (DOF) 0.14 µm, exposure latitude (EL) 5.1%). ISTP materials had the next-largest process window (DOF 0.12 µm, EL 3.2%), followed by the rCEL (0.11 µm, 0.58%). This study is an analysis of the feasibility of using the materials in double-exposure mode