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Nutritional strategies to reduce the severity of infection with EI
Nutritional Strategies to Assist in Reducing the Severity of Infection with Influenza
Dr C.E. Foote
Equine Consulting Services
Several scientific studies suggest that certain nutrients may assist in reducing the severity of influenza infection. While these studies are based on laboratory work using mouse models, they may pose some relevance to other species including horses. This paper summarises some of these studies, with reference to the current equine influenza outbreak in Australia.
Nutrients of particular importance – Summary
Ø Selenium – reduces severity and persistence of infection
Ø Zinc – enhances immune responses
Ø Vitamin A – assists with regeneration of respiratory epithelium
Ø Vitamin E – enhances virus clearance particularly in aged animals
Nutrient and study details
Selenium
Studies have demonstrated that a dietary deficiency of the nutritionally essential trace element selenium increases the severity and persistence of infection with influenza virus.
Ø In a laboratory study, mice fed diets with a deficiency in selenium had much more severe pathology than mice that were fed a diet adequate in selenium following experimental infection with influenza A strain. In addition to the lung pathology being more severe, it also persisted longer in selenium deficient mice as compared with selenium adequate mice (Beck et al., 2001).
Importance in Australia → A marginal selenium deficiency is widespread in Australian soils.
Daily Nutrient Requirements* → Adult 1.0mg/day; Lactating mare 1.25mg/day
Common feed sources** → Lucerne hay 0.5mg/kg; Oats 0.21mg/kg; Trace mineral supplements; Premixed feeds
Zinc
Ø Zinc deficiency is associated with profound impairment of cell-mediated immunity and studies of zinc supplementation in older adults have demonstrated enhanced immune responses (High, 2001).
Daily Nutrient Requirements* → Adult 400mg/day; Lactating mare 500mg/day
Common feed sources** → Lucerne hay 23mg/kg; Oats 23.8mg/kg; Trace mineral supplements; Premixed feeds
Vitamin A
Ø A deficiency in Vitamin A resulted in the impaired regeneration of normal, respiratory epithelium of laboratory mice experimentally infected with a mouse-adapted strain of influenza A virus (Stephensen, 1993).
Daily Nutrient Requirements* → Adult 15000IU/day; Pregnant/Lactating mare 30000IU/day
Common feed sources** → Green pasture, hay. Unlikely to be inadequate in most horse diets.
Vitamin E
Vitamin E supplementation enhances immune functions of mice and humans.
Ø Experiments using mouse models demonstrate that high doses of vitamin E significantly enhance clearance of influenza virus in aged mice. The effect of supplemental vitamin E in young mice was not as significant (Hayek, 1997, Han et al., 2000a).
Ø When comparing the effect of Vitamin E on the course of influenza infection with that of other antioxidants, following experimental infection in mice, vitamin E supplemented animals had significantly reduced viral titres compared to unsupplemented animals, and were able to maintain body weight after infection. Other antioxidants did not have a significant effect on viral titre or weight loss (Han et al., 2000b).
Daily Nutrient Requirements* → Adult 500IU/day; Pregnant/Lactating mare 800-1000IU/day
Common feed sources** → Green forage.
→ In diets consisting largely of cereal grains, protein meals, chaff and dried hays, Vitamin E is generally in short supply.
Omega 3 fatty acid
Ingestion of oils high in Omega-3 (e.g. fish oil) can suppress the inflammatory response to injury and may impair host resistance to infection (Byleveld et al. 1999).
Oils that contain higher amounts of Omega-3 (n-3) fatty acids are considered to provide natural anti-inflammatory compounds. Suppression of inflammation is associated with an increased severity of infectious disease (Rubin et al., 1989) and for this reason, concerns have been raised by various researchers regarding the use of oils high in Omega-3 (such as fish oil). High intakes of Omega-3 fatty acids can imbalance the controlling action of other fatty acids. In animals, an Omega-3 to Omega 6 fatty acid ratio of 1 part Omega 3 to 5-10 parts Omega 6 is considered beneficial. Canola oil in pure form or blended 50:50 with soyabean or corn oil contains a suitable ratio of Omega-3 to Omega-6 essential fatty acids (Kohnke et al., 1999).
Need more information? Contact Equine Consulting Services
Copyright Ó 2008 Equine Consulting Services
References:
* Dietary nutrient requirement information was sourced from NRC (National Research Council) 2007. Nutrient Requirements of Horses, 6th rev. ed. Washington, DC: National Academy Press.
** Sourced from Kohnke, J. Kelleher, F., Trevor-Jones, P. (1999). Feeding Horses in Australia. RIRDC Publication No 99/49.
Beck, M.A., Levander, O.A., Handy, J. 2003. Selenium deficiency and viral infection. J. Nutr. 133, 1463S-1467S.
Beck, M.A., Nelson, H.K., Shi, Q., Van Dael, P., Schiffrin, E.J., Blum, S., Barclay, D., Levander, O.A. 2001. Selenium deficiency increases the pathology of an influenza virus infection. FASEB J. 15, 1481-1483.
Han, S.N., Wu, D., Beharka, A., Smith, D.E., Mender, B.S., Meydani, S.N. 2000a. Vitamin E supplementation increases T helper 1 cytokine production in old mice infected with influenza virus. Immunology 100, 487-493.
Han, S.N., Meydani, M., Wu, D., Bender, B.S., Smith, D.E., Viňa, J., Cao, G., Prior, R.L., Meydani, S.N. 2000b. Effect of long-term dietary antioxidant supplementation on influenza infection. The Jounrals of Gerontology Series A: Biological Sciences and Medical Sciences 55, B496-B503.
Hayek, M.G., Taylor, S.F., Bender, B.S., Han, S.N., Meydani, M., Smith, D.E., Eghtesada, S., Meydani, S.N. 1997. Vitamin E supplementation decreases lung virus titers in mice infected with influenza. J. Infect. Dis. 176, 273-276.
High, K.P. 2001. Nutritional strategies to boost immunity and prevent infection in elderly individuals. Clinical Infectious Diseases 33, 1892-1900.
Rubin, R.H., Wilkinson, R.A., Xu, L., Robinson, D.R. 1989. Dietary marine lipid does not alter susceptibility of (NZBxNZW)F1 mice to pathogenic organisms. Prostaglandins. 38, 251-262.
Stephensen, C.B., Blount, S.R., Schoeb, T.R., Park, J.Y. 1993. Vitamin A deficiency impairs some aspects of the host response to influenza A virus infection in BALB/c mice.
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