Effects of glycyrrhizic acid (Viusid-Vet® powder) on the reduction of influenza virus spread and on production parameters in pigs

Abstract

Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Ocampo Camberos L, Tapia G, Gutierrez L, Sumano Lopez HS. Effects of glycyrrhizic acid (Viusid-Vet® powder) on the reduction of influenza virus spread and on production parameters in pigs. Veterinaria Mexico OA. 2017;4(1). doi: 10.21753/vmoa.4.1.373 Influenza viruses are among the most important respiratory pathogens in pigs and humans. They cause seasonal epidemics in pigs and occasional pandemics in humans. Herbal remedies have been regarded as suitable elements to aid in controlling influenza. This study was carried out to analyse the effects of the in-feed administration of glycyrrhizic acid, the best-known component of liquorice (as Viusid-Vet® powder), in pigs suffering an outbreak of influenza. Eighty crossbred Duroc-Landrace pigs, one day post-weaning (22 days old), were included in this trial. Piglets were randomly divided into the following two groups: those treated with glycyrrhizic acid and an untreated control group. Serological measurements to assess viral load and humoral responses were carried out. Blood samples from pigs were obtained every fortnight, starting on week two and ending on week 15. With these samples, haemagglutination inhibition (HI) tests were performed, using A/swine/New Jersey/11/76 (H1N1) and A/swine/Minnesota/9088-2/98 (H3N2) as reference viruses. Quantitative RT-PCR tests against the M gene of the influenza virus were also performed to assess viral shedding from nasal swab samples on weeks 1 to 8 after the beginning of the trial. Weight variables were assessed weekly for 18 weeks. In the HI tests, treated animals showed fewer positive responses compared to the control group for H1N1 and H3N2. However, a positive response to viral protection, as assessed by HI tests, was regarded as not conclusive of humoral immune stimulation. qRT-PCR tests for viral spread exhibited a lower rate of excretion for the treated group compared to the untreated one. Hence, it appears that glycyrrhizic acid stimulates, to some extent, immune responses against pig influenza as measured by viral shedding. For mean body weight, the generalized estimating equations show a higher weight gain for pigs treated with glycyrrhizic acid than the control group (P = 0.0001). These effects may assist producers in addressing the aftermath of an influenza outbreak. Figure 1. Results of RT-PCR viral shedding test against the M gene. (Likelihood χ21,7 = 19.2 P = 0.0001).