August 2016 – Swine in Minnesota

Effect of electrostatic particle ionization technology on swine airborne pathogens

Dr. Alonso who just graduated from her PhD at the University of Minnesota, published in collaboration with Drs. Davies, Morrison and Torremorell an article evaluating the electrostatic particle ionization (EPI) technology as a technique to reduce particle load in the air. The results showed that EPI was the most efficient when the system was close to the particle source and when the particle size was between 3.3 and 9 μm no matter what swine pathogen was evaluated. This technique could be promising in decreasing the risk of disease transmission between swine facilities.

Abstract Influenza A virus (IAV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV) and Staphylococcus aureus are important swine pathogens capable of being transmitted via aerosols. The electrostatic particle ionization system (EPI) consists of a conductive line that emits negative ions that charge particles electrically resulting in the settling of airborne particles onto surface s and potentially decreasing the risk of pathogen dissemination. The objectives of this study were to determine the effect of the EPI system on the quantity and viability of IAV, PRRSV, PEDV and S. aureus in experimentally generated aerosols and in aerosols generated by infected animals. Efficiency at removing airborne particles was evaluated as a function of particle size (ranging from 0.4 to 10 μm), distance from the source of ions (1, 2 and 3 m) and relative air humidity (RH 30 vs. 70 %). Aerosols were sampled with the EPI system ‘‘off’’ and ‘‘on.’’ Removal efficiency was significantly greater for all pathogens when the EPI line was the closest to the source of aerosols. There was a greater reduction for larger particles ranging between 3.3 and 9 μm, which varied by pathogen. Overall airborne pathogen reduction ranged between 0.5 and 1.9 logs. Viable pathogens were detected with the EPI system ‘‘on,’’ but there was a trend to reducing the quantity of viable PRRSV and IAV. There was not a significant effect on the pathogens removal efficiency based on the RH conditions tested. In summary, distance to the source of ions, type of pathogen and particle size influenced the removal efficiency of the EPI system. The reduction in inf ectious agents in the air by the EPI technology could potentially decrease the microbial exposure for pigs and people in confinement livestock facilities.

Link to the full article

New swine virus identified in the US: introducing porcine sapelovirus

This past month, a team of swine pathologists including Dr. Albert Rovira from the University of Minnesota identified, thanks to funds from Swine Health Information Center’s Support for Diagnostic Fees program, a new swine virus called porcine sapelovirus.

Swpalovirus-figure2 — Histological lesion associated with infection by porcine sapelovirus

This virus is thought to induce atypical neurological signs in pigs and has previously been described in Korea. Videos of the clinical presentation can be been here.

Research is still on-going to prove Koch’s postulate and declare causality between the presence of the virus and the clinical presentation but it is a step forward in the identification and understanding of swine pathogens.

Full description of the porcine sapelovirus cases

What is the antimicrobial susceptibility of US Brachyspira species?

To answer this question, Drs. Mirajkar, Davies, and Gebhart from the University of Minnesota, collected a total of 124 field isolates originating from all over the country. In this study, four different Brachyspira species were evaluated for their susceptibility against the main antimicrobial medicines used in swine production. Overall the US isolates had the tendency to be less resistant to antimicrobials than were isolates from other countries. However, low susceptibility to lincomycin and to tylosin were noted in the domestic strains. Lastly, the authors raised the question of the lack of Clinical and Laboratory Standards Institute-approved clinical breakpoints for Brachyspira species which, by categorizing an isolate as sensitive, intermediate, or resistant, would be a tremendous help in determining the best treatment and control strategies at the farm level .

Abstract: Outbreaks of swine dysentery, caused by Brachyspira hyodysenteriae and the recently discovered “Brachyspira hampsonii,” have reoccurred in North American swine herds since the late 2000s. Additionally, multiple Brachyspira species have been increasingly isolated by North American diagnostic laboratories. In Europe, the reliance on antimicrobial therapy for control of swine dysentery has been followed by reports of antimicrobial resistance over time. The objectives of our study were to determine the antimicrobial susceptibility trends of four Brachyspira species originating from U.S. swine herds and to investigate their associations with the bacterial species, genotypes, and epidemiological origins of the isolates. We evaluated the susceptibility of B. hyodysenteriae, B. hampsonii, Brachyspira pilosicoli, and Brachyspira murdochii to tiamulin, valnemulin, doxycycline, lincomycin, and tylosin by broth microdilution and that to carbadox by agar dilution. In general, Brachyspira species showed high susceptibility to tiamulin, valnemulin, and carbadox, heterogeneous susceptibility to doxycycline, and low susceptibility to lincomycin and tylosin. A trend of decreasing antimicrobial susceptibility by species was observed (B. hampsonii > B. hyodysenteriae > B. murdochii > B. pilosicoli). In general, Brachyspira isolates from the United States were more susceptible to these antimicrobials than were isolates from other countries. Decreased antimicrobial susceptibility was associated with the genotype, stage of production, and production system from which the isolate originated, which highlights the roles of biosecurity and husbandry in disease prevention and control. Finally, this study also highlights the urgent need for Clinical and Laboratory Standards Institute-approved clinical breakpoints for Brachyspira species, to facilitate informed therapeutic and control strategies.