426 Journal of Equine Veterinary Science October 2004

Veterinary Review

In a recent issue of the Horse Report (July 2004), DrGregory L. Ferraro related equine disease to publichealth. He said, “Public health officials are oftenquoted as saying, ‘Nobody cares about public health

until there is an epidemic of a serious infectious disease.’People generally are concerned about their own healthand that of their families but seldom think about the im-portance of maintaining the health of the broader com-munity. Yet in today’s world of rapid international travel,involving the movement of large numbers of humans, an-imals, and foodstuffs, the global spread of disease is anever increasing reality.

“This phenomenon is of no less concern to equinehealth. Horses today are second only to humans in world-wide travel. Consequently, the chance for exposure to in-fectious agents abroad and the possibility for introducingdisease into the home environment upon return arecauses for concern. There are currently 17 diseases listedwith the World Health Organization that are consideredto be potential threats to global equine health. Underthese circumstances, an outbreak of infectious diseasethat could impair the free movement of horses, or stopthem entirely, is not only possible but probable. The re-sults of such an epidemic could be devastating, consider-ing that today’s industry is entirely dependent on the freemovement of horses for competition.

“Faced with these facts, each of us within the equineindustry has a solemn responsibility to become involvedat some level with the maintenance of equine publichealth. The individual horse owner, trainer, rider, or vet-erinarian must pay attention to reported disease condi-tions, abide strictly with regulations designed for theircontrol, and report outbreaks of disease whenever theyoccur. Equine industry officials must become involved inthe regulatory processes for disease management andcontrol and must support programs needed to define anddeter the spread of disease. Medical scientists with ex-pertise in both infectious disease and equine health mustwork diligently to identify pathogenic agents that pose a

0737-0806/$ - see front matter© 2004 Elsevier Inc. All rights reserved.doi:10.1016/j.jevs.2004.09.004

Infectious Disease and Equine Public Health

potential threat and identify methods for their control anderadication.

“The Center for Equine Health [CEH, at theUniversity of California, Davis] and its cooperating re-searchers have been focused on this issue for several years.We have worked to develop techniques for identifying se-rious pathogenic agents, to determine the extent of theirvirulence, and to design strategies and methods for theircontrol or prevention. We have achieved a better under-standing of how, why, and where disease-causing agents(viruses, bacteria, protozoa) develop their potential healththreat to horses. As you will see in the pages to follow, wehave made significant progress toward understanding thedelicate balance between host, pathogen, and environment,which determines the rate and virility of infection within alocal community and throughout the world.

“To a large extent, these discoveries and the diseasecontrol methods that they produced have been made pos-sible by the visionary leadership and financial support ofseveral philanthropic organizations to whom the horse isof particular interest. You have read and will continue toread about the West Nile virus [WNV] epidemic in theUnited States. Studies pertaining to this virus have beenongoing at the CEH since its initial outbreak in Queens,New York, thanks to the support of the Stans Foundation.Our work with the long-standing problem of equine pro-tozoal myeloencephalitis [EPM] has been supported bythe Wayne and Gladys Valley Foundation. Our School ofVeterinary Medicine has an internationally recognizedEquine Viral Disease Laboratory, owing to the foresightand generosity of Bernard and Gloria Salick. This labo-ratory has undertaken a major equine viral disease re-search initiative made possible by the generosity of theHarriet E. Pfleger Foundation.

“One of the most unique of the infectious disease re-search initiatives established by the CEH has been the de-velopment of the Bernice Barbour CommunicableDisease Laboratory. Supported by a New Jersey–basedfoundation of the same name, this research program isdesigned to study the very basic mechanisms within thehost, agent, and environment that allow for the infectionand transmission of pathogenic agents in humans andother animals, using diseases of the horse as experimen-tal models.”

Volume 24, Number 10 427

EQUINE INFECTIOUS DISEASE RESEARCHSeveral years ago, a meeting was held at the CEH to

discuss the future direction of equine infectious diseaseresearch. In attendance were faculty researchers with ex-pertise in a number of scientific disciplines from the UCDavis School of Veterinary Medicine. The intention ofthe group was to identify both traditional and innovativeinvestigative strategies that could significantly enhancethe global effort to control the spread of infectious dis-eases in the horse and other animal species.

In spite of the fact that in 1968 the US surgeon gen-eral declared that the war on infectious disease had beenwon, the UC Davis group knew otherwise. They knewthat of the worldwide human deaths each year, fullyone-third were caused by infectious disease. They knewthat more people are suffering from tuberculosis todaythan ever before. They knew also that the traditionalweapons of vaccination and antibiotic therapy were be-coming less effective in preventing infection and that thespread of so-called third world diseases among the mod-ern industrialized countries was now a fact of life.

This initial meeting defined and delineated the prob-lem. It also provided a stimulus for insightful discussionand set in motion a process of planning that took severalmonths to complete. At the conclusion of this process, theCEH had a research strategy for achieving significantnew knowledge about the spread of disease among horsesand other species, including humans. Groups were orga-nized to investigate specific diseases such as EPM orWNV. Others were charged with broader mandates, suchas studying genetic variations within a virus strain thatdetermine its ability to cause disease in the horse. Theplan also included an innovative group of scientistswhose mandate was to study pathogenic mechanismscommon to all infectious diseases, rather than to studyany specific disease itself.

One of the first organized scientific teams wascharged with the investigation of EPM to determine when,where, and how horses become infected with the proto-zoal agents (Sarcocystis neurona and Neospora hughesi)that cause the disease. A 5-year research plan was out-lined, and the work progressed through the support of theWayne and Gladys Valley Foundation. Better diagnostictests also were pursued, resulting in the development of animmunofluorescent antibody test to more accurately iden-tify exposure of the horse to EPM-causing agents.

The development of this test has given veterinariansa tool that can rule out the disease as a cause of neuro-logic deficits in horses. Recently, this group was able toidentify and experimentally reproduce an antigen that issecreted by EPM-causing parasites. This discovery may

ultimately lead to a test to positively identify the presenceof the parasite in sick animals. The work of these investi-gators has now taken on even more importance since Sneurona was recently linked to increasing death ratesamong sea otters along the California coast.

Equine viral disease is another area of focus for CEHscientists. Owing to the initial support of horse enthusiastsBernard and Gloria Salick, the Equine Viral DiseaseLaboratory was created through the CEH and charged withthe investigation of global viral diseases. This group hasidentified the genetic variation and virulence determinantsfor most strains of equine arteritis virus in the world. Theyhave developed a network of international collaboratingscientists and have conducted in-depth studies of viral dis-eases such as African horse sickness and WNV in southernAfrica, where both diseases are prevalent. Thanks in largepart to the Stans Foundation, researchers in the EquineViral Disease Laboratory have been able to study and trackthe progress of WNV across the United States. They arenow conducting a prospective study on the emergence ofthe virus in California and are well positioned to contributesignificantly to its control. This group has now partneredwith the Harriet E. Pfleger Foundation on a long-term viraldisease initiative designed to advance the identificationand control of viral diseases that could negatively affectthe international health, transport, and commerce ofhorses. One of the first projects of this initiative is the de-velopment of a vaccine to prevent African horse sickness,a serious and fatal disease of horses that appears to be onthe verge of spreading globally. Another project involvesthe identification and study of respiratory viruses that areconstantly present in the stables of athletically competitivehorses to find out which of them are important to the dy-namics of respiratory disease outbreaks.

Perhaps the most unusual of the infectious diseasestudy groups is one that came about through the vision-ary leadership of the Bernice Barbour Foundation. Thetrustees of this animal philanthropic foundation cameforward and requested that the CEH develop a truly newand innovative approach to the study of communicablediseases in animals. While they were supportive of ourefforts in the field of equine infectious diseases, theywere interested in finding a way to use the CEH’s recog-nized expertise to serve a broader interest in understand-ing the disease process in all animals. What resulted wasthe creation of the Bernice Barbour CommunicableDisease Laboratory. It was designed to create an intellec-tual research umbrella to study the basic mechanisms ofenvironmental pathogen transport, infection, and host im-mune response common to all disease-producing agents,regardless of species affected. Their concept was that if

428 Journal of Equine Veterinary Science October 2004

we could understand the primary way in which microbesgo about their business, we could develop disease pre-vention strategies effective in all animals. In the BerniceBarbour Communicable Disease Laboratory, diseases ofthe horse are used as a model to study factors common tothe infectious processes of all diseases. While the conceptbehind the Bernice Barbour Communicable DiseaseLaboratory was truly innovative and bold, it was notwithout risk, but the gamble has already paid off withsome startlingly new insights.

What these last several years of work at the CEH hasdemonstrated is that strategic long-term planning, com-bined with dedicated researchers and committed philan-thropic support, can result in remarkable scientificachievement. The ultimate benefit of this innovative ap-proach to veterinary research is the dramatic improve-ment to the health and welfare of animals. Its concept andimplementation is, truly, the scientific wave of the future.

THE BERNICE BARBOUR COMMUNICABLEDISEASE LABORATORY

The Bernice Barbour Communicable Disease Labora-tory was established 4 years ago with the purpose of tak-ing a new approach to the conduct of infectious disease re-search. The laboratory created a “research umbrella” underwhich medical scientists with differing skills and expertisewere brought together as a team. This team has embarkedon long-term, multitasking studies of how and whypathogenic microorganisms are able to survive, infect, andcause disease among the animal species of the world. Thelaboratory was designed to focus on the basic mechanismsby which all infectious diseases are produced, rather thanon individual diseases exclusively. Although the researchwould be conducted using pathogens that are common inhorses, the studies would be directed toward demonstrat-ing infectious processes that are characteristic of all animaldiseases and thereby have broad relevance.

The scientific plan was to conduct research along 3specific investigative tracks. (1) Studies of the life of in-fectious microbes outside the sick animal (environment).An attempt would be made to determine which factorsallow an infectious agent (protozoa, bacteria, virus, etc)to survive in the environment, reproduce, and present it-self in sufficient numbers at a specific place and time tocause disease. (2) Studies of the means used by microor-ganisms to invade the host and cause disease (pathogen).Why, for example, are certain agents able to get past thebody’s protective barriers and cause damage when other,

more abundant microbes cannot? (3) Studies of the com-plex system of immunologic and inflammatory processesthat the animal body (host) uses to protect itself againstinvading microbial enemies. The ultimate purpose of thisinvestigative track would be to determine how the body’sown physiologic processes could be used to protect anddefend itself from invasion and disease.

The Bernice Barbour Communicable DiseaseLaboratory has made considerable progress toward reach-ing these goals over the last 4 years, beginning with theirenvironmental research. Waterborne transmission of infec-tious agents remains an area of public health that is inade-quately addressed both in the United States and interna-tionally. The virulence of waterborne infectiousmicroorganisms depends on effective transport to suscep-tible hosts. Our research group hypothesized that the prob-ability of waterborne transport of microbial pathogens isgoverned by factors that load a watershed with adequatenumbers of infective pathogens, processes that attenuate orremove the pathogen load, and the efficiency of the hydro-dynamic transport system into which it is deposited. To in-vestigate that theory, the researchers studied naturally oc-curring phenomena to develop laboratory models todemonstrate the attenuation and inactivation after environ-mental contamination of groundwater with differentstrains of the protozoal parasite Cryptosporidium parvum.They found that the likelihood of the waterborne transmis-sion of this disease-producing organism depends on itsability to avoid irreversible binding to soil and/or streamsediments. This and other continuing studies together rep-resent one of the most comprehensive evaluations of thefundamental processes that could eventually lead to pre-venting waterborne zoonotic diseases.

The study of infectious organisms has been directedto understanding the characteristics within families ofmicrobes that determine their ability to cause disease.Researchers are also attempting to identify critical as-pects of natural transmission and genetic evolution thatresult in the development of virulent characteristics instrains of previously innocuous microorganisms. One so-phisticated model currently being used in this research isthe manipulation and modification of infectious comple-mentary DNA clones of virulent and nonvirulent strainsof equine arteritis virus. If we can determine in the labo-ratory those basic phenotypic viral parameters that affectinfectivity, then this knowledge could be applied towardthe development of improved diagnostic testing, vac-cines, and potential new therapies.