Commentary |
Commentary is not refereed.
The truth about "syndromes"
Dr. Steve Henry, Abilene Animal Hospital
"A diagnosis is a matter of fact; it is not a matter of opinion."
--Dr. Carl Osborne, 1973
"Syndrome worship" seems to be gaining converts in the veterinary scientific community. This troubles me a lot. Converting confusing clinical signs into an alphabet soup of subjective, quasidescriptive acronyms does not constitute objective, valid science. Left unchecked and unchallenged, elevating subjective opinions in the form of acronyms to the level of perceived objective reality leads at best to intentional delusion and, at worst, to fraud.
Many factors converge to encourage the capricious "recognition" of new disease syndromes. Product vendors avidly promote new syndromes, leveraging acronyms into marketing campaigns in an effort to expand their markets beyond the NADA or biologic license approvals they hold. Research funds are hard to come by, and self-promoted identity via acronym can be used to acquire funding through emotional appeal rather than scientific rationale. For our part, we clinicians self-aggrandize our "knowledge" by presenting as "fact" a diagnosis whose existence has not yet been proved and cannot be documented independently. At the worst, this behavior is tortured into a selling tool for financial gain.
Let me provide some examples that might better illustrate the concerns:
- GOOD: SMEDI was nicely described by Dr. Dunne. Etiology was lacking and was so acknowledged. The progress of the scientific method was reported as it developed, however. When the etiologies were defined, "SMEDI" was dropped and the proper, confirmed, and diagnosed etiology was used to clearly identify the disease.
- BAD: MMA still is viewed as a "disease" 20 years after the etiology and mechanisms were clearly described. Even today, the failure to acknowledge and accept coliform mastitis, not MMA, results in treatment that is inappropriate, extra-label, and even damaging to the sow (NAHMS survey).
- WORSE: PRDC, actually no more than an identified compound etiologic respiratory disease, has been leveraged as a marketing tool and is being promoted by inference as a "discrete disease" when it is not.
Certainly, the rush to assign acronyms to each new clinical observation is not confined to our branch of medicine alone. It is critical to the responsibility we owe our clients and the food-consuming public, however, that we cry loudly for OBJECTIVITY and the SCIENTIFIC METHOD in our dealings with each other and our practice standards, as well as our expectations for quality in our medical journals and in our communication with the public media.
This abrasive commentary is not meant to target specific persons but to raise a challenge to the institutions that are our base for credibility. "Syndromes" may be helpful in trying to communicate what we see. To elevate them beyond that level is, I believe, lying to ourselves. If we choose not to be honest with ourselves, how can we expect to truly be of service to others? We are and must remain a service industry.
Emerging diseases--Are there alternatives to the "vet rumor mill"?
Dr. Beth Lautner, National Pork Producers Council
Everyone in the United States pork industry would agree that our industry's identification of and response to the emergence of porcine reproductive and respiratory syndrome (PRRS) was less than stellar. Many pork producers expressed frustration at the lack of a coordinated and timely effort by producer associations, practitioners, the research community, diagnostic laboratories, and government animal health officials in addressing this extremely serious industry disease. As pork production becomes the sole source of income for many pork producers, they are becoming increasingly aware of the impact an emerging disease can have on their potential for success. In addition, increased movement of pigs during stages of production and the sourcing of genetic material both allow an emerging disease to move rapidly into many herds before it is detected. In other words, the stakes are higher than ever. And we face many challenges in responding to emerging diseases in an effective and timely fashion.
For example, the United States currently has no clearly defined system to detect and respond to emerging diseases--either new entities or a change in the presentation of a previously identified agent. We rely on practitioners and diagnostic laboratories to identify an emerging disease, but there is no organized group to transfer this information to those who could respond to it in the appropriate manner. By the time an emerging disease "boils to the surface" by being discussed in networks of practitioners and in the hallways at scientific meetings, it may have been present for a significant period and resulted in economic losses to some producers. We do not have a conscious system to decide how to respond to an emerging disease. Options for responses include education, lab-based research, short-term field studies, national epidemiological studies, interim control measures, and certification efforts.
The "underground" nature of these discussions is exacerbated by the increasingly proprietary character of emerging disease research and investigations. It has been extremely frustrating to organize a discussion of a critical emerging health issue in the industry, only to have many of the researchers unable or unwilling to discuss their research in a manner that will facilitate and expedite solutions for the industry. In many cases, university and government researchers and practitioners report they cannot talk about certain aspects of their research because it is being funded by outside sources and they are bound by confidentiality agreements. While outside funding plays a valuable role in an era of decreased public funding, it does add this somewhat disturbing dimension to the study of emerging diseases. Although the industry just wants answers to the questions and does not care how they are obtained, individual scientists can have professional and economic aspirations that may affect their ability and willingness to establish collaborative projects and be forthcoming with important research results.
In addition, diagnostic laboratories are challenged by the lack of compatible computer systems that would allow centralized communication on emerging diseases, the ability to make a variety of inquiries in databases, and a common case definition language for emerging diseases.
These issues are the reality we must work with. Any plan to address emerging diseases must recognize these challenges and find ways to address them in a win-win manner.
The first attempt at a collaborative response to an emerging animal disease was the development of the Acute PRRS Investigative Study. This study involved a collaboration among:
- the National Pork Producers Council (NPPC),
- the AASP,
- Veterinary Services of the Animal and Plant Health Inspection Agency, and
- university diagnostic laboratories.
For more information on the study, go to the producer section of the NPPC home page (http://www.nppc.org/). While the study has not generated as much participation as the collaborators would have liked, it has provided an extremely useful opportunity to identify the challenges faced by this type of effort and to make changes before a more serious disease situation needs to be addressed. The key challenges are:
- assuring producers of confidentiality,
- encouraging the participation of all eligible producers and practitioners,
- dispelling producer wariness toward government involvement,
- encouraging diagnostic laboratories to report all cases that meet the case definition,
- designing a case definition,
- determining who should be in charge when there are many participants,
- addressing media concerns, and
- responding to trade issues.
Being a country that has the mechanisms in place to quickly and publicly identify an emerging disease is a bit of a "Catch 22." Countries can either be secretive and guarded with information, or they can be open and forthright in discussion regarding emerging diseases. The former alternative is all too common: there are numerous examples in international public health and animal health of academics reporting a disease, only to be subsequently discredited by a government and/or industry that denies the existence of the disease. Fortunately, electronic communication is making it more difficult for countries to operate in this fashion. The second, forthright approach requires consistent communication with our trading partners to keep them informed and to minimize the potential for the placement of inappropriate trade restrictions.
While some in the short term may be more comfortable with a "don't look, don't tell" approach to emerging diseases, it is critical that the United States have a system in place to quickly minimize the production and economic impact of an emerging disease. Such a system is the key to our national future as a reliable, low-cost supplier of pork to the international and domestic market. The net long-term winners in trade and production efficiency will be countries that have such systems in place. There will be rough spots in getting there, but the rewards in risk mitigation are tremendous.
One of the most rewarding projects I have had the privilege to work with since I joined the NPPC is the Swine Futures Project. It is a joint industry and government effort to protect and improve the health of the national swine herd, support production of a quality product, and promote access to international markets. A key focus of the project is to identify future industry health needs and to determine how to meet those needs. Considerable effort is being directed to developing an emerging disease "early warning" system and a portfolio of responses. The key questions are:
- What are the sources for intelligence on emerging disease?
- How is information collected from these sources?
- Who collects this information?
- How do we decide that there truly is an emerging disease?
- What are the choices for a response?
- Who determines what the response should be?
- How is the response evaluated?
In a future issue, we will discuss the Swine Futures Project recommendations to address these areas, as well as an approach to emerging animal health issues that are not disease related.
Our industry needs a coordinated, integrated system to detect and respond to emerging diseases. It is in the best interests of all involved to help develop and support such a system. While there are many challenges to developing such a system, we must find a way to accomplish this. Our industry needs it and is expecting us to deliver it.
When is a new "syndrome" really a new disease?
Dr. Cate Dewey, Executive Editor
Defining a new syndrome can have both a positive and a negative impact on the swine industry. When it is well defined, recognizing the existence of a new syndrome can assist medical professionals in diagnosing and treating animals with a given set of clinical signs. However, when we observe signs that cannot readily be accounted for as a recognized disease, if we are too quick to assume that we have a new etiologic agent, it can detrimentally affect the export market and may reduce the domestic consumption of pork. This is particularly true when names such as "Mystery Swine Disease" or "Mad Cow Disease" are used. Producers and veterinarians also tend to treat the new syndrome as the "flavor of the month," which excuses a multitude of poor management practices.
In Dorland's Medical Dictionary1 there are 13 pages dedicated to the description of various syndromes. A syndrome is defined as a specific set of clinical signs with or without specific postmortem lesions that occur together in a given species. It must be present in the same form in a number of herds and affect the same age group of pigs. Precise, objective measurements must be used to define a new syndrome. Together, the aggregate of symptoms indicates the presence and nature of a disease.
By definition, a new syndrome does not equate to a new disease agent. Before we definitively link an etiologic agent to a new syndrome, Koch's postulates must be fulfilled. These include:
- isolating the organism in every case of the disease and in pure culture,
- failing to isolate the organism from normal tissues or in the presence of other diseases, and
- inducing the disease with the organism under controlled experimental conditions.
Indeed, a new syndrome may or may not be caused by a given etiologic agent. One example is the "18-week wall" or "porcine respiratory disease complex (PRDC)"--the sudden onset of respiratory disease and mortality in late stage finisher pigs when clinical respiratory symptoms were not apparent in the grower phase of production. The PRDC is not caused by one single etiologic agent but by a combination of already recognized respiratory pathogens acting collectively under a specific set of management conditions. PRDC may be associated with different etiologic agents in different barns. As far as I know, the syndrome has not been recreated in a laboratory setting and Koch's postulates have not been fulfilled; however, the syndrome has provided veterinarians with a recognizable description of a condition of finisher pigs. What is important to realize is that the identification of a new syndrome does not automatically imply the existence a new etiologic agent. Veterinarians, the pork consuming public, and persons responsible for the export market must not confuse the description of a new syndrome with a new etiologic agent.
The article on post weaning multisystemic syndrome (PMWS) in this issue of Swine Health and Production raises important questions for each of us. Do our clients' pigs have this syndrome? Have we missed or misdiagnosed this problem? Is the syndrome caused by circovirus? If so, should we be testing our clients herds for circovirus? Circovirus is probably widespread.2 In addition, circovirus may not be the cause of PMWS or may, like PRRS with SAMS (sow abortion and mortality syndrome), only cause the syndrome under very specific conditions. If we find circovirus, what then? As scientists, if we test suspect herds, then we must test "healthy" herds as controls.
Veterinarians are scientists. We must apply objective measurements when making diagnoses, apply scientific principles to our observations, and read the literature critically.
References
1. Dorland's Illustrated Medical Dictionary. 25th ed. Toronto, Canada: WB Saunders Company. 1994.
PMWS is a useful acronym
Drs. John C.S. Harding, Phil I. Willson, Edward G. (Ted) Clark, and John A. Ellis
We commend Drs. Henry, Lautner, and Dewey for presenting their points of view. Dr. Lautner highlighted one of the ongoing challenges of our industry: the surveillance of emerging diseases. We agree that although some governmental and nongovernmental organizations worldwide have developed excellent surveillance programs, pooling resources into one focused direction remains a challenge. We also commend Dr. Dewey for her logical thought process in defining new disease entities. However, regarding Dr. Henry's commentary, "The Truth About Syndromes," we offer the following alternative perspective.
We agree that self-aggrandizing has no place in science. However, the real issue is not whether a new syndrome represents a new disease, but rather whether the syndrome is descriptive of the condition at hand. Unfortunately, the three examples cited were a select group of the common syndromes of the day:
- SMEDI: was a descriptive acronym in its time but has since been replaced by proven etiology. The SMEDI syndrome has long been replaced and thus does not represent today's terminology.
- MMA: we agree is a poorly chosen description of the condition which presumably at the time described an anorexic lactating sow with vulvar discharge and/or mastitis. Our greater understanding of the bacterial causes of mastitis and metritis over the last 20 years has led to the demise of this acronym's practical usefulness. Veterinarians who continue to use MMA to describe anorexic post-lactational sows with udder congestion mislead their clients at their own peril.
- PRDC: We believe that PRDC is a good acronym because it portrays a clinical condition with multifactorial etiology. It is unlikely that any qualified veterinarian would portray PRDC as an etiology unto itself. PRDC remains a descriptive acronym that has enhanced the industry and our clients' understanding of respiratory disease in grow/finish pigs. As for PRDC as a marketing tool: this is simply marketing at its best, where the user must decipher fact from fiction. In our opinion, full-page advertisements displaying a prominent veterinarian beside their favorite animal health product is also marketing at its best.
Conspicuous in their absence are the syndromes that have gained household prominence in our industry and society. It is unfortunate that the commentary does not go on to critique PRRS, AIDS, SIDS, carpal-tunnel syndrome, toxic shock syndrome, trisomy-21 syndrome, etc. The list goes on and on. All of these are absolutely accepted as medically correct terminology--acronyms that at some point in the past reflected a new disease or condition.
Whether or not PMWS is new disease entity, a unique expression of an existing entity, or the result of multifactorial etiologies is yet to be proven. We intend the name of this syndrome and acronym to be descriptive and used under appropriate circumstances to facilitate understanding and communication of a disease entity or condition in swine. When "PMWS" is used in this way, we believe that it has served its purpose.