In this month column of the National Hog Farmer, Dr. Albert Rovira from the University of Minnesota is reviewing the cases of intoxication due to ionophores, these antibiotics given through the feed to control bacterial and coccidial infections in swine.Clinical signs are non-specific. Indeed, pigs become weak and stop eating but do not have a fever. In more severe cases, neurological signs can be noted. However, histological lesions are striking with a dramatic change of the muscle structure as is shown in Figure 1 below.
There are three main causes of ionophore intoxication in swine:
Dosage error in the diet: the optimal concentration is very small, between 15 and 30 parts per milliom.
Mixing ionophore and tiamulin: Tiamulin prevents the ionophore from being excreted by the body, leading to toxic blood levels.
Inclusion of ionophores designed for another species. Usually, the levels are incorporated at a concentration higher than the toxic level.
In conclusion although cases of ionophore intoxication are rare in swine, it may become more prevalent starting in 2017, with the approval of the only swine ionophore as a growth promotant.
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.
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.
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, andBrachyspira 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.
One flu, many colors: that is the title of the latest article published in the National Hog Farmer by two faculty members from the University of Minnesota, Drs. Culhane and Rovira. If it is common to talk about one influenza especially in the One Health initiative which reminds us that human and animal health are intricately related, the authors also emphasize that there are “many variants of influenza A viruses [which] paint a complicated picture, sometimes with colors too numerous to grasp with quick glances.”
Because influenza is common to swine, poultry, and human, there are many differences among the strains, enhanced by the variations found between and within geographic locations. This is why our experts recommend to characterize the virus, and go one step further than the one test common to all influenza A.
As they put it themselves, “Influenza A viruses are fascinating, challenging and dynamic” and it is important to determine their colors.
Last Friday, a team of UMN swine nutritionists and veterinarians published the results of their research on the effect of thermal treatments and additives on the inactivation and survival of Porcine Epidemic Diarrhea virus (PEDv) in swine feed. They concluded that both the addition of feed additives and thermal treatments decreased PEDv load in the feed.
Fig 1. Inactivation of PEDV in complete feed when exposed to thermal processing.
The inactivation curves determined by the Weibull model for the survival of PEDV in complete feed at 120°C, 130°C, 140°C, and 145°C.
Abstract: Infection with porcine epidemic diarrhea virus (PEDV) causes diarrhea, vomiting, and high mortality in suckling pigs. Contaminated feed has been suggested as a vehicle of transmission for PEDV. The objective of this study was to compare thermal and electron beam processing, and the inclusion of feed additives on the inactivation of PEDV in feed. Feed samples were spiked with PEDV and then heated to 120–145°C for up to 30 min or irradiated at 0–50 kGy. Another set of feed samples spiked with PEDV and mixed with Ultracid P (Nutriad), Activate DA (Novus International), KEM-GEST (Kemin Agrifood), Acid Booster (Agri-Nutrition), sugar or salt was incubated at room temperature (~25°C) for up to 21 days. At the end of incubation, the virus titers were determined by inoculation of Vero-81 cells and the virus inactivation kinetics were modeled using the Weibull distribution model. The Weibull kinetic parameter delta represented the time or eBeam dose required to reduce virus concentration by 1 log. For thermal processing, delta values ranged from 16.52 min at 120°C to 1.30 min at 145°C. For eBeam processing, a target dose of 50 kGy reduced PEDV concentration by 3 log. All additives tested were effective in reducing the survival of PEDV when compared with the control sample (delta = 17.23 days). Activate DA (0.81) and KEM-GEST (3.28) produced the fastest inactivation. In conclusion, heating swine feed at temperatures over 130°C or eBeam processing of feed with a dose over 50 kGy are effective processing steps to reduce PEDV survival. Additionally, the inclusion of selected additives can decrease PEDV survivability.