Animal Health (NP 103) Annual Report for 2004

Introduction

The mission of the Animal Health Program is to conduct basic and applied research on selected diseases of economic importance to the United States livestock and poultry industries. The goals of the research mission are to produce knowledge and technology to reduce economic losses from infectious, genetic, and metabolic diseases of livestock and poultry. Dr. Robert Heckert, National Program Leader, Animal Health and Dr. Cyril G. Gay, National Program Leader, Animal Health and Safety continue to lead this ARS research program. Dr. Gay is lead on domestic disease issues and vaccine and drug discovery projects, and Dr. Heckert is lead on projects involving foreign and emerging diseases. 

The Animal Health National Program is coming to the end of its five-year program cycle and the program assessment of past performance is underway, lead by Professor Paul-Pierre Pastoret, Director, Institute for Animal Health, United Kingdom. A program assessment workshop was held in Greensboro, NC in October 2004, where the program assessment external review panel had a chance to hear about the ARS Animal Health research activities, talk to commodity groups and ask a lot of questions of all those involved in the program. The assessment will also include an appraisal of the program as determined by a national electronic survey. In 2005, scientists in the Animal Health program will begin writing their project plans that will set the research plans for the next five years up until 2010.

The Animal Health National Program currently includes 54 research projects supported by 106 scientists located at 12 research sites throughout the country.  The ARS research budget for the Animal Health Program Fiscal Year (FY) 2004 was $49.8 million (NET).  Critical to the success of the research conducted at ARS is the ability to build and maintain the infrastructure of our laboratories to ensure the highest level of biosecurity and quality research.  Accordingly, we are continuing to develop plans to upgrade the animal research facilities at the National Animal Disease Center (NADC) in Ames Iowa. Construction of a high containment animal barn began in the fall of 2003 and is progressing.  Design of a consolidated laboratory that will be used by NADC and the Animal and Plant Health Inspection Service (APHIS) is progressing and ground breaking is scheduled for the fall of 2005.

Several of the scientists in the Animal Health National Program again received accolades this past year.  Dr. Curt Van Tassell had a stellar year, receiving the American Dairy Science Outstanding Young Scientist award and the Presidential Early Career Award for Scientists and Engineers for his work in bovine genomics. Darrell Kapczynski received the P. P. Levine Award for his paper published in Avian Diseases 2004, "Development of a Virosome Vaccine for Newcastle Disease Virus". Drs. Kapczynski, Spackman, Suarez, Swayne and King all received the USDA Group Honor Award for Excellence reflecting their contributions to the Exotic Newcastle Disease Research Response Team.

Scientists within the National Animal Health Program were very active in their fields Fiscal Year (FY) 2004, with 240 articles submitted for publication.  Of these, 90% (217) were sent to peer-reviewed scientific journals with 54% (117) already accepted for publication by midyear.  Many of the discoveries and findings were published in the popular press to reach our customers and stakeholder, including articles in trade journals and book chapters.  Technology transfer activities for the National Animal Health Program also included 5 invention disclosures.

A number of meetings and workshops were sponsored by this national program in the past year including an ARS Program Review Workshop and an ARS TSE research planning meeting.

The following section of the report summarizes high impact research results addressing objectives in the current national program action plan.

Animal Health Research Highlights

Detecting and Finding the Source of the First Bovine Spongiform Encephalopathy (BSE) Case in the United States (Washington State Index Case).  Discovering the first BSE-infected cow in the U.S. had the potential to significantly impact our economy, undermine the confidence of our trade partners in our cattle industry, and curtail our export market of live cattle and meat products.  Finding BSE in the U.S. also underscored the importance of animal health research in safeguarding our food supply and public health, with ARS playing a significant role in providing APHIS critical scientific information that enabled USDA’s action and regulatory agency to take swift action.  First ARS was able to very quickly conduct sophisticated confirmatory tests to let APHIS know that the samples they tested were indeed of bovine origin and BSE-positive.  Second, ARS conducted forensic genetic tests to let APHIS know that the Washington State index case came from Canada.  This information enabled APHIS to move forward rapidly and execute an action plan to protect consumers and limit the damage to our livestock industries.  ARS’s transmissible spongiform encephalopathy (TSE) research program exemplified the value of having expert scientists readily available to support APHIS’s diagnosticians and epidemiologists in time of crisis.  Although a significant amount of TSE research has been conducted in laboratories worldwide, we still do not understand how the BSE agent (a presumed infectious protein) inflicts damage to the central nervous system, what animal species that can be infected and transmit the disease, and how to detect “pre-clinical” infected animals to prevent them from entering the food supply chain.  Investing in the ARS TSE research program will enable our veterinary scientists to provide answers to these important questions and continue to provide critical support to our colleagues at APHIS, FSIS, and FDA as they tackle TSE-related issues, including the emerging Chronic Wasting Disease (CWD).  

Defining the epidemiology of SARS and West Nile Virus. The USDA, Agriculture Research Service has an interest in emerging zoonotic diseases that may impact human and poultry health. ARS, with specialized Biosafety-Level 3 facilities, is in a unique position to study some of these emerging diseases.  ARS was one of the first laboratories to do poultry related research for both the Severe Acute Respiratory Syndrome (SARS) virus and West Nile virus in the U.S.  The SARS virus emerged in Southeast Asia and infected over 8400 humans with over 800 deaths.  Early epidemiologic evidence suggested a zoonotic potential for the virus with animals in the live animal markets in China.  The source of the virus causing SARS is still unknown but animals may be the source or may be contributing to the spread of the virus.  ARS scientists conducted a study to determine if chickens, turkeys, ducks, geese and Japanese quail were susceptible to the SARS virus and could spread the virus to humans. The study failed to demonstrate that the SARS virus could grow in these birds. These data indicate that the common five domestic poultry species were not the reservoir and will not spread the SARS virus to humans.  Similar research with West Nile Virus was conducted that showed the common poultry species could be infected with these viruses, but clinical disease seldom occurred and that with low levels of viremia, these species were unlikely to spread the virus. Continued research such as this on emerging zoonotic diseases is important to ensure animal and human health.

Scientific Publications:

Swayne, D.E., Suarez, D.L., Spackman, E., Tumpey, T., Beck, J.R., Erdman, D., Rollin, P.E., Ksiazek, T.G. 2004. Sars - Coronavirus Does Not Cause Disease or Infection in Experimentally Inoculated Domestic Poultry. Emerging Infectious Diseases 10(5):914-916, 2004.

Avian influenza virulence mechanism defined. Avian influenza presents a major disease threat to the US poultry industry. The unpredictable nature of the disease and the viral agent that causes it is the same today as it was in 1983 when the disease struck the Northeastern United States with severe economic consequences. Because of research on avian influenza viruses in recent years we now know that some viruses can rapidly change from causing only mild disease to one that causes a deadly disease in chickens. It is likely that the longer a virus infects commercial poultry, the more likely it is to cause the severe form of the disease. ARS scientists in collaboration with the National Veterinary Services Laboratories (Ames, IA), Central Veterinary Laboratory (Weybridge, England), and the Chilean Department of Agriculture (Santiago, Chile) have now described the first field case of recombination for an avian influenza virus that resulted in a low pathogenicity avian influenza virus mutating to high pathogenicity form of the virus.  The origins of how highly pathogenic avian influenza viruses arises from the mutation of low pathogenic viruses are described in a paper published in Emerging Infectious Diseases and illustrate a new mechanism of how an influenza virus evolve to more virulent forms. The understanding of this mechanism for increased virulence for avian influenza will improve our understanding of the pathogenesis of the virus and eventually may improve our ability to predict which low pathogenic viruses may become highly pathogenic.

Scientific Publications:

Suarez, D.L., Senne, D.A., Banks, J., Brown, I.H., Essen, S.C., Lee, C.W., Manvell, R.J., Mathieu-Benson, C., Marreno, V., Pedersen, J., Panigrahy, B., Rojas, H., Spackman, E., Alexander, D.J. Recombination Resulting In Virulence Shift In Avian Influenza Outbreak, Chile. Emerging Infectious Diseases. Vol 10, No.4, 2004.

Jones, Y., Swayne, D.E. 2004. Comparative Pathobiology of Low and High Pathogenicity H7N3 Chilean Avian Influenza Viruses in Chickens. Avian Diseases 48(1):119-128, 2004.

A non-antibiotic treatment for mastitis. Mastitis is the most costly of all dairy cattle diseases, resulting in losses of over $2,000,000,000 annually. The dairy industry requires new tools to solve the mastitis problem.  Use of antibiotics and other drugs and chemicals in the dairy industry is one of the greatest threats to food safety.  Surveys indicate that at least 5% of bulk milk shipments and 30% of milk sold to consumers contains detectable amounts of antibiotics and drugs. This presents a significant human health hazard.  Also, the antibiotics approved for treating mastitis are increasingly ineffective, largely due to the appearance of resistant strains. A non-antibiotic preventative of mastitis during the dry period of dairy cows was shown to be as effective as antibiotics. At dry off, mammary quarters of 40 cows were injected with antibiotics and 40 cows were injected with Poly-X. At the time of calving, cows treated with Poly-X had less mastitis than cows treated with antibiotics.  A patent application has been filed. Dairymen and organic farmers will have available a non-antibiotic compound for use during the dry period for dairy cows.

Scientific Publication(s):

Bannerman, D.D., Paape, M.J., Hare Jr, W.R., Hope, J.C. 2004. Characterization of the bovine innate immune response to intramammary infection with klebsiella pneumoniae. Journal of Dairy Science. 87(8):2420-2432.

Bannerman, D.D., Paape, M.J., Lee, J., Zhao, X., Hope, J.C., Rainard, P. 2004. Escherichia coli and staphylococcus aureus elicit differential innate immune responses following intramammary infection. Clinical and Diagnostic Laboratory Immunology. vol. 11(3), pp. 463-72.

Paape, M.J., Bannerman, D.D., Zhao, X., Lee, J. 2003. The bovine neutrophil; structure and function in blood and milk.  Veterinary Research. Vol. 34, pp. 597-627.

Paape, M.J., Burvenich, C., Mehrzad, J., Monfardini, E., Capuco, A.V. 2004. Role of neutrophil polymorphonuclear leukocytes during bovine coliform mastitis: physiology or pathology? Veterinary Research. 66(2):97-153.

Detection of epidemic strains of Listeria monocytogenes.  Listeria monocytogenes is a bacterium capable of causing serious disease in humans and animals.  L. monocytogenes infection of cattle and sheep can lead to disease of the central nervous system and death. Human listeriosis is a potentially fatal food borne disease often associated with the consumption of contaminated dairy products.  In order to understand the epidemiology and epidemic potential of L. monocytogenes isolates, it is important to effectively access their virulence.  ARS scientists in collaboration with Washington State University developed the first biologically relevant model that can be used to assess L. monocytogenes strain virulence, which is a critical step towards understanding why some strains cause epidemics whereas others do not.   Six human epidemic strains and six environmental strains were assayed for invasiveness using an oral inoculation mouse model.  Variation in strain invasiveness was observed and epidemic strains were significantly more invasive than environmental strains. The oral inoculation mouse model will be used to evaluate the virulence potential of genes present in epidemic strains and provide valuable insight into understanding the epidemiology of this animal and human health threat, resulting in the application of early control measures at the farm level.

Scientific Publication(s):

Borucki, M.K., Peppin, J.D., White, D., Loge, F., Call, D.R. Variation in biofilm formation among strains of Listeria monocytogenes. Applied Env. Microbio. 2003. v. 69. p. 7336-7342.

Kim, S.H., Bakko, M., Knowles Jr, D.P., Borucki, M.K. 2004. Oral inoculation of a/j mice detects invasiveness differences between listeria monocytogenes epidemic and environmental strains. Infection and Immunity. 72(7):4318-4321.

Ward, T.J., Gorski, L.A., Borucki, M.K., Mandrell, R.E., Hutchins, J., Pupedis, K. 2004. Intraspecific phylogeny and lineage group identification based on the Prfa virulence gene cluster of Listeria monocytogenes. Journal of Bacteriology. 2004. 186(15):4994-5002.

Immunology of Porcine Reproductive and Respiratory Syndrome (PRRS) Virus.  Porcine reproductive and respiratory syndrome (PRRS) virus infections account for up to 15-20% of the economic losses yearly (nearly $600 million) in the U.S. swine industry.  Methods of PRRS virus intervention (vaccines, therapeutics, genetics, etc.) are limited and new novel strategies are desperately needed.  One reason new intervention strategies have not been forthcoming is the lack of information known about the host cell response to infection by PRRS virus.  ARS scientists demonstrated that PRRS virus infection does not result in the induction of type I interferons as would be expected with most RNA viruses.  Specifically, PRRS actively suppresses the induction of Interferon-beta (IFNB) expression, which also prevents the induction of Interferon-alpha (IFNA).  These results are significant because both IFNA and IFNB are members of the innate immune system, which is typically viewed as the first response of the immune system. Activation of this response signals other branches of the immune system to become activated and mount a protective immune response.  The fact that PRRS virus is capable of suppressing the activation of this response may explain an important mechanism this virus used to evade the immune host response, a critical step in the rational design of effective biotherapeutics and vaccines to control this important swine disease.

Scientific Publication(s):

Miller LC, Laegreid WW, Bono JL, Chitko-McKown CG, Fox JM. Interferon type I response in porcine reproductive and respiratory syndrome virus-infected MARC-145 cells. Arch Virol. 149:2453-63, 2004.

Newcastle disease virulence determination. Newcastle disease virus (NDV), also known as avian paramyxovirus type 1 (APMV-1), infects all known wild and domestic bird species. Different NDV strains vary in virulence from those that caused disease and mortality during the 2002-03 outbreak of exotic Newcastle disease (END) in California to those of low virulence that cause mild or inapparent respiratory infections with reduced flock productivity, the predominant form that occurs in the U.S. END is a reportable disease and its presence in commercial poultry resulted in embargoes of poultry export from the affected U. S. states. Currently there is no method besides animal inoculation used to determine the virulence of NDV. ARS scientists examined the embryonated chicken egg as a model system to evaluate virulence properties of NDV isolates. Embryos from eggs inoculated with NDV reference and mutated reference strains were collected, formalin fixed, sectioned, and stained with a gene probe and NDV antibodies to detect virus distribution in the tissues and membranes of the embryonated eggs. Low-virulence strains were detected exclusively in the cells of the chorioallantoic membrane, whereas more virulent NDV isolates and mutated strains that had been demonstrated to have acquired virulence for chickens were widely disseminated in chicken embryo tissues. The results demonstrate the potential value of this as a model system for evaluating NDV virus virulence as an alternative to chicken inoculation.

Development of a rapid test for a turkey disease. Poult enteritis mortality syndrome (PEMS) is a highly infectious disease of young turkeys. PEMS and similar disease conditions have been reported in most regions where turkeys are commercially produced including; the Southeastern United States, Texas, California, Arkansas, Missouri, and Israel.  PEMS has been called one of the most devastating emergent disease to strike the poultry industry in recent years.  Since its emergence in the early 1990's, outbreaks of PEMS have cost the turkey industry millions of dollars in losses annually. The major impact of PEMS is due to mortality and decreased production as turkeys are stunted and grow poorly when affected by the disease.  Currently the agent or agents that cause PEMS are unknown.  PEMS appears to be a complex disease, possibly involving multiple pathogens and some anecdotal evidence suggests that immunosuppression may be involved. By understanding what agents are involved in causing PEMS, management practices may be modified to minimize the impact of the disease. Real-time reverse transcriptase polymerase chain reaction (RRT-PCR), a new molecular diagnostic technique, which is rapid, highly specific and highly sensitive (superior to standard RT-PCR) was developed and applied to the detection of three viruses commonly associated with Poult Enteritis Mortality Syndrome (PEMS); turkey astrovirus, turkey coronavirus and turkey reovirus. Previously, no rapid or specific diagnostic tools were available for the detection of viral agents, which are involved in causing PEMS.  A laboratory validation for these tests with clinical samples from experimental cases was successfully completed with optimization of for sample types and times were determined for each of the three viruses.  This assay is superior to previous tests and will accurately identify infected turkeys.

Epidemiology of avian disease clarified. Avian pneumovirus (APV), now classified as an avian metapneumovirus (AMPV), was isolated from commercial turkeys in Colorado in 1996. The disease was reported in the United Kingdom in 1985 and prior to 1996 the disease was exotic to North America. The virus causes a mild, but rapidly spreading, upper respiratory disease and adverse effect on weight gain and feed conversion. Secondary bacterial infections increase the severity of the disease. The initial diagnosis of the disease in the U.S. was delayed because the U.S. isolate was of a different subtype than had been isolated elsewhere and serological assays to detect the new subtype had to be developed. APV infections continue to cause productivity losses in turkeys in the Upper Midwest particularly in the state of Minnesota, but more recently in Iowa, Wisconsin, and North and South Dakota as well. ARS scientists, in collaboration with scientists in the University of Minnesota, completed the entire genomic sequences and compared the AMPV subtype C genes SH, G, and L nucleotides and predicted amino acid sequences with those of human metapneumoviruses (hMPV). The comparison supported earlier findings that AMPV subtype C was closer evolutionary to hMPV than the other AMPV subtypes A, B, and D. This suggests that the source of the new APV serotypes seen in the US was derived from humans and not from other avian sources.

Scientific Publication(s):

Kapczynski, D.R., Sellers, H.S. 2003. Immunization Of Turkeys With A DNA Vaccine Expressing Either the F Or N Gene Of Avian Metapneumovirus. Avian Diseases v.47 p.1376-1383.

Kapczynski, D.R. 2004. Development of A Virosome Vaccine For Protection In Turkeys Against Avian Metapneumovirus Subtype C. Avian Diseases v.48, p.332-343. 2004.