Introduction to Epidemiology

Initial draft 8/98  Initial HTML draft 1/99 Links updated May 04, 2013

(in serious need of updating)


The purpose of this module is to introduce the discipline of epidemiology to veterinary students and veterinary practitioners in a self-teaching mode. Please note that because I don't currently teach the epidemiology class in the WSU DVM, the references in this webpage are dated.

(The handout for my recent class presentation on evidence-based medicine is here).

Learning Objectives:

After reading this module, you should be able to:

  • Define the term epidemiology.
  • List and describe the four "W" questions.
  • Define the terms risk factor, determinant, critical thinking, exposure, and cause.
  • Distinguish between empirical and theoretical evidence.
  • Distinguish between objective and subjective assessment.
  • Define "evidence-based medicine".
  • Describe how the principles of epidemiology are important in the practice of clinical veterinary medicine on grouped animals.
  • Explain why epidemiologic principles are important in protecting the integrity of one's personal professional knowledge base and how this process differs between before and after graduation.
  • Explain why incorporating personal experience into one's knowledge base is difficult.
  • Discuss the roles of the FDA and USDA in licensing veterinary pharmaceuticals and biologicals and how this differs from human medicine.
  • Discuss the potential impact of the Internet on the profession, including good and bad points.

Four Major Questions:

  • What is "epidemiology"?
  • Why are the principles of epidemiology needed in clinical medicine?
  • Why is epidemiology important to the practitioner?
  • Why is this importance increasing?

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Q1: What is "epidemiology"?

Word root and history: Epi - "upon", demos - "the people", logos - "study of".

Originated with Hippocrates (400 BC)

Classical Definition:The study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems (CDC).

Distribution: Who? Where? When? Which animals are affected (ages, breed, location, time)?

Determinants: Why? Why were the specific animals affected and others not? What "risk factors" are "causing" this?

Risk Factor: (Condition Determinant, Predisposing Factor) An individual attribute or exposure that is positively or negatively associated with the occurrence of a disease.

Attribute: Risk factor that is an intrinsic characteristic of the individual (e.g., genetic susceptibility, age, sex, breed, immune status and weight).

Exposure: Risk factor that is in the environment external to the individual (e.g., nutrition, housing, husbandry practice, infectious or toxic agent).

Cause: That combination of risk factors which, acting alone or in combination, at some time during an individual’s life, inevitably result in a particular disease in that individual.

The logical, systematic approach to understanding the complexities of disease (Torrence, 1997).

Critical observing and thinking for the clinician.

Critical Observing: Observing in a fashion to make one's observations as objective as possible rather than subjective, being aware of the problems of over-interpretation of vague signals, of bias due to prior information and using classification schemes that have been validated.

Critical Thinking: The ability and willingness to assess evidence and claims, to seek a breadth of contradicting as well as confirming information, to make objective judgments on the basis of well supported reasons as a guide to belief and action, and to monitor one’s thinking while doing so.

The methods to empirically, rather than theoretically, determine whether or not something works in the clinical setting.

Empirical: Based on direct observation of evidence without regard to theory.

Theoretical: Based on a hypothesis, reasoned from a body of principles or biological plausibility.

"Something" EX: A diagnostic test, a therapeutic treatment, a preventive vaccine.

Methods EX: Clinical trials, case-control studies

How to count and compare correctly in the medical arena.

"Medical detective work"

Doing valid, unbiased, precise counts and comparisons between groups for medical purposes has more pitfalls than is apparent on the surface.

Point: Using these methods, disease control procedures can be developed before the underlying pathophysiological mechanism is sufficiently understood (or even if is misunderstood) to do so and before any etiologic agent is identified.

Examples of this point (and a bit of history):


He advocated draining swamps to prevent the production of miasma (bad night air) because he observed its association with yellow fever and malaria.

This is also the first known example of doing the right thing (draining swamps) for the wrong reason (miasma rather than mosquitoes).

John Snow, cholera epidemics and the Broad Street Pump

He hypothesized from observational epidemiologic data that cholera was caused by something unseen that was transmitted by the fecal-oral route from sick people to healthy people in water. He then prevented cholera by removing the handle of the Broad Street Pump in 1854.

This insight is remarkable given that the germ theory of disease was not developed until the 1880’s.

See: On the Mode of Communication of Cholera, John Snow, MD, 1936 (pdf)

Kilbourne and Texas Fever (Cattle Tick Fever)

Using epidemiologic methods, Kilbourne concluded that ticks were transmitting the disease between cattle. This is the first time that a disease was identified in which a protozoan parasite, Babesia bigemina, was being transmitted to a mammal through an invertebrate vector, the tick Boophilus annulatus. The agent was unrecognized until the association was shown.

Toxic Shock Syndrome (human)

The association between TSS, Staph. aureus, and superabsorbent Rely tampons was established in 1980 by epidemiological methods, after which the risk of the disease was markedly reduced (Ann Rev Microbiol 38:315-338). As of 1998, the biological mechanism is still unclear.

AIDS (human)

Using epidemiologic methods, the "Who?" and the "Why?" of AIDS were identified and measures to prevent transmission were developed (late 1982) before the nature of the etiologic agent was identified (late 1984).

Epizootic Bovine Abortion

Using epidemiology, control measures were developed for EBA in 1976 (expose females to the ecological niche of a tick, Ornithdoros coriaceus, before pregnancy or avoidance of that niche, southwestern US coastal foothills, during pregnancy) but the etiologic agent still has not been identified as of 1998. This is much to the embarrassment of those who have thought they had identified an agent and published accordingly.

As an aside, I've heard rumors that this disease is one of the major reasons the UC Davis veterinary school was founded 50 years ago.

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Q2: Why are the principles of epidemiology needed in clinical medicine?

Differences between individuals in manifestations of a disease:

The wide variation between individual animals in response to a disease and its prevention.

If all responses were identical, we could do detailed experiments on one animal and know how to diagnose, treat and prevent that condition in all others of that breed.

EX: People respond differently to infection by the same strain of cold virus.

A spectrum of disease results from this variation

Individuals usually manifest a wide range of severity of disease signs for the same disease, ranging from unaffected to subclinical to clinical to dead.

EX: Cold virus carried into classroom by shedding individual – virtually all exposed in enclosed air space but few develop clinical disease and more develop unrecognized (subclinical) infection. Of those with clinical disease, some develop mild disease and some are bed-ridden.

The differences in risk factors acting on the individual cause this spectrum.

With infectious agents, differences between individuals in previous exposure and response to it.

Differences between individuals in exposure factors - nutrition, housing.

Differences in doses and strains (infectivity, virulence) of infectious agents.

EX: People under stress often have more severe disease than those who are not.

Differences in clinical acumen and interpretation between observers – clinicians

The more subjective (less objective) the assessment of the disease phenomenon, such as clinical signs or radiograph images, being observed, the greater this problem.

Objective: Assessment not requiring judgment on the part of the observer

EX: counting heart beats or dead animals or using a measuring instrument to establish blood pressure, weight or blood glucose.

Subjective: Assessment requiring trained judgment on the part of the observer.

EX: reading varying densities on film as abnormal or not, classifying cells as malignant or not, or classifying auscultatory sounds as abnormal or not.

Point - The amount of disagreement between experts classifying the same set of materials is sometimes surprising, indicating the difficulty of the process.

EX: Pathologists reading human biopsy slides

A panel of expert pathologists disagreed two or more times on the interpretation of 38% of human skin melanoma biopsy specimens as benign or malignant. (Hum Pathol 27:528-31 (1996))

EX: Clinicians auscultating equine abdomens

Equine clinicians auscultating equine abdomens for gut sound agreed only 37% better than random chance (complete agreement would be 100%). (Equine Vet J 22:182-185.

EX: Eddy DM (1990). The Challenge. JAMA 263:287-290.

"In general, observers looking at the same thing will disagree with each other or even with themselves from 10% to 50% of the time."

Cardiologists evaluating high quality angiograms for stenosis of coronary vessels:

"... asked to estimate whether the percentage of stenosis ... was greater or less than 50%, they disagreed on 60% of the patients."

"... on two successive readings of the same angiograms, the observers changed their minds from 8% to 37% of the time, depending on the vessel segment."

"Surgeons given written descriptions of surgical problems split down the middle ... half recommending surgery, half not. When surveyed again two years later, the same surgeons often disagreed with their previous opinions, with as many as 40% changing their recommendations."

"In Vermont, the chance of having one’s tonsils removed as a child are 8% in one community and 70% in another."

"The variability occurs because physicians must make decisions about phenomenally complex problems, under very difficult circumstances, with very little support. They are in the impossible position of not knowing outcomes of different actions, but having to act anyway."

Point - The clinical process (establishing diagnosis, prognosis and therapy) is often difficult.

EX: Necropsy results on human deaths in hospitals

Approximately 15% have conditions that had the condition been diagnosed correctly and treated antemortem the death would not have occurred. (NEJM 318:1249-1254 (1988) and others)

Aside: Advances in diagnostic technology does not appear to have reduced this percentage over the decades. See Kirch W, C Schaffi (1994). Reflections on misdiagnosis. J Intern Med 235:399-404.

EX: Rectal palpation of ovarian structures

In a study involving per-rectal ovarian palpation of 463 dairy cows, the status of ovarian function was correctly identified in only 64%. (Vet Rec 128:121-124 (1991))

In a study using per-rectal palpation of ovarian structures to determine which of 124 beef cows would respond to PGF2a for heat synchronization, 18% of the cows were incorrectly assigned to the treatment group and 37% incorrectly assigned to the non-treatment group. (JAVMA 188:1417-1419. (1986))

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Q3: Why is epidemiology important to the veterinary practitioner?

1) It is the basis for logically working up a disease problem affecting a group of animals.

Outbreak investigation - the classical application of epidemiologic reasoning ("shoe-leather" epidemiology)

EX: CDC workups of food-borne illness outbreaks in humans that are frequently reported. See the CDC Mortality and Morbidity Weekly Report (MMWR) at

Almost all species present problems to the clinician in which group membership is an important component.

EX: Infection control in hospitalized animals. (see J Vet Intern Med 11:340-343 (1997), JAVMA 211:1554-1557 (1997), JAVMA 188:173-177 (1986))

EX: Problems on horse breeding farms (see Aust Vet J 67:436-439 (1990), JAVMA 201:296-302 (1992)), dog kennels, animal control pounds, livestock operations such as dairy farms, beef feedlots, lab animal colonies, other pet breeding colonies.

EX: Problems at fairs, tracks and exhibitions. (see JAVMA 207:211-213 (1995), Cornell Vet 75:277-288 (1985), Equine Vet J 19:524-530 (1987))

2) Epidemiologic reasoning provides a sound basis for evaluating imperfect clinical studies done on groups of animals and applying the results to the individual clinical patient.

Research studies are imperfect due to ever-present constraints on resources - short time, insufficient money, and the limited number of patients that can be enrolled.

Point: Thus clinicians usually don't have perfect information on which to make decisions. The consumer of information from these clinical studies (you) must be aware of the effect of these compromises on the strength of evidence and must judge them accordingly.

The resource problem is more severe for veterinary medicine than human medicine (10 - 100 to 1 difference in amount of funds and number of people). For example, the University of Washington has more clinician FTE's in the Medical School than there are veterinarians, private, regulatory, academic and other, in the state of Washington.

Aside: Veterinary clinicians often have to make decisions on animal care by reasoning from evidence developed in human medicine. This reasoning by analogy has many opportunities for error.

3) It provides a logical basis for understanding the process of diagnosis in the presence of uncertainty, resulting in better clinical prediction for individual patients.

Clinicians often must diagnose and treat difficult cases that present vague signs and use less than perfect diagnostic tests to do so.

Understanding diagnostic test performance and how it works in the diagnostic process increases the likelihood of making correct clinical decisions.

(For an excellent preview, see JW Tyler & JS Cullor (1989). Titers, tests, and truisms: rational interpretation of diagnostic serologic testing. JAVMA 194:1550-1558. and JW Tyler & J Schumacher (1992). Problem-oriented diagnostics, statistical inference and clinical decisions. Comp Cont Educ Pract Vet 14:1009-1014.)

4) Using epidemiologic principles protects the integrity of ones personal professional knowledge base

Professional knowledge base: That body of professional knowledge that one uses to practice veterinary medicine.

How is professional knowledge base acquired?

Veterinary school education - the filtering and feedback is done for the student by the faculty.

Problem - Students are not expected nor encouraged to critically appraise the information that is being delivered by professors as part of the students' education. Thus:

The information isn't delivered with the associated detail that is needed for its critical appraisal but rather is delivered in the form of authoritative dogma.

Dogma: Those beliefs held as established or put forth as an authoritative or expert opinion presented with little or no supportive empirical evidence from primary sources.

As a consequence, the student doesn't develop the skills and habits necessary to critically appraise information that they will need to protect the integrity of their knowledge base after they graduate.

After graduation, the student will have to do the critical appraisal that is being done in school by the professor. If they don't, they run serious risk of "contaminating" their knowledge base and not providing the most sound care to their patients.

Practice experience

Continuing education

Organized - annual meetings

Self-motivated self-learning - reading journal articles, new texts, on-line materials.

What are the problems with updating and maintaining ones personal version of the professional knowledge base?

The normal progress of science.

Because of incessant scientific progress, new information is constantly found that replaces old information, continually making parts of your knowledge base obsolete. Some of the changes are quite dramatic and markedly change clinical success in dealing with the condition

EX: Changing understanding of the uterine defense mechanism in the bovine - Estrogen to PGF2a

See Paisley LG, WD Mickelsen, PB Anderson (1986). Mechanisms and therapy for retained fetal membranes and uterine infections of cows: A review. Therio 25:353-381.

EX: Changing understanding of periparturient bovine hypocalcemia - from focus on Ca:P nutrient balance to focus on cation:anion nutrient balance.

See Oetzel GR (1991). Meta-analysis of nutritional risk factors for milk fever in dairy cattle. J Dairy Sci 74:3900-12.

The volume and flow of information is increasing.

Some have estimated:

That the half-life of most veterinary information is approximately 10 years (Carl Osborne)

(The question I have is "Which half?")

That the amount of information is doubling every 5 years.

This may be due to the effects related to another estimate, which is that 80 to 90% of all the scientists ever alive are alive today. (De Solla Price, 1963)

Changes in practice species mix.

The animal species mix presented by clientele changes as fads of animal ownership come and go and as practice market area demographics change.

EX: Emergence of llamas and ratites as a major practice species over the last two decades.

The problem of interpreting personal experience appropriately

An Example:

How long does a series of successes need to be before one concludes that it is a more viable way of doing something compared to the conventional approach?

The length of the series of successes needed to support a new way of doing something is larger than most people intuitively expect.

"Three over N" Rule (JAMA 249:1743-1745 (1983), BMJ 311:619-620 (1995))

Rule: Given that a series of N cases have been treated with complete success, this is still consistent with an overall, long-term failure rate as high as 3 / N.

Number of Cases done with success

Calculated upper bound of long-term failure rate

Actual (Wilson's method)

5 cases

0.60 (60%)


10 cases

0.30 (30%)


30 cases

0.10 (10%)


300 cases

0.01 (1%)


Point: For many conditions, most clinicians do not follow enough patients well enough (objective, blinded assessment) to identify the smaller but clinically important differences between procedures (e.g., new surgical techniques, new drugs).

We humans have serious problems with the accuracy of human perception, with memory construction (as opposed to recall) and with selective recall.

(for further general information on this and other relevant issues, see the excellent book Schick et al. (1995). How to Think About Weird Things: Critical Thinking for a New Age)

For a website on the errors of visual perception (visual illusions), see

5) Veterinary medicine does not have nearly the full benefit of the rigorous FDA drug and biological approval process and the USDA approval process is not nearly as rigorous.

What the FDA does: As a practical and political matter, the FDA's major concern is with those drugs and medical devices that present risks to human health and only secondarily with those that present risks to animal health.

FDA requires rigorous evaluation of human drugs and vaccines for safety and efficacy.

EX: Compare the detail required in drug advertisements in JAMA to those in JAVMA.

FDA requires rigorous evaluation of those veterinary drugs that could result in human exposure through residues in edible tissues (food animal drugs) or through contact.

This process is very expensive (>$150 million per drug?) and is borne by pharmaceutical companies. To require it for all animal drugs would likely drastically limit the pharmaceutical armamentarium available to the veterinarian.

What the USDA does:

The USDA provides minimal monitoring of vaccines for safety, purity, potency and efficacy, concentrating primarily on safety and purity (freedom from other infectious agents or toxic materials).

This is done by monitoring the procedures and sanitation in the plants producing the product.

To show efficacy of vaccines the conventional approach is to use laboratory challenges of animals rather than to use controlled field studies.

In the Espeseth and Greenberg document on the "Published Articles" website referenced below, it states "It is generally more difficult to demonstrate significant efficacy under field conditions. Field efficacy studies are often inconclusive because of uncontrollable outside influences."

Further, if other sound, independent evidence shows that a USDA-approved product is not efficacious under most circumstances, the law does not require reexamination of its licensing or prevent its production or sale.

Point: Many people are unaware of what a USDA license does and doesn't mean; clinicians with mistaken assumptions are likely to make wrong decisions.

Point: A USDA-approved product may not be efficacious the under field conditions experienced by your client's animals.

For further information, see:

Memorandums - VS Memorandum 800.202 General Licensing Considerations: Efficacy Studies, 2002 (pdf)

6) Continuing Biological Changes:

Unnatural human selection pressure on animal characteristics:

EX: Brachycephalic dogs that need C-sections to reproduce

EX: Dairy cows that produce an average of 30,000 lbs. of milk per lactation compared to 5,000 lbs. 60 years ago.

Continuing change in the microbial community due to selective pressure and intermixing due to global transportation.

Bacteria in particular have very efficient mechanisms for genetic alteration and for exchanging successful genetic adaptations between even unrelated species and genra up to and including mammalian genes.

EX: Rapid development and exchange of antibacterial resistance to antibiotics

EX: Rapid world-wide spread (by unknown means) of new strains, such as Salmonella typhimurium DT104 and E. coli O157:H7.

Emergence of new agents or significantly different strains

In humans, 22 major etiologic agents have emerged in 20 years

(listed at

(for an entertaining read on this issue, see Garrett, L (1994). The Coming Plague: Newly Emerging Diseases in a World Out of Balance)

Selected examples of emerged agents in animals:

  • Hog cholera (1810, Tennessee)
  • Bovine Virus Diarrhea (1946, New York)
  • Cryptosporidiosis (1976)
  • Canine parvovirus (1978)
  • Lyme disease (1982, Connecticut)
  • E. coli O157:H7 (1982, North America)
  • Salmonella enterica variant Typhimurium phage type 104 Resistance Type ACSSuT
  • Bovine Spongiform Encephalopathy (1986, England)
  • Equine morbilivirus (1994, Australia)
  • Influenza A(H5N1) (1997, Hong Kong)

For further information on emerging diseases, see Emerging Infectious Diseases 4(3) 1998, presentations from the International Conference on Emerging Infectious Diseases, an on-line journal at

Emerging Infections: An Evolutionary Perspective (Joshua Lederberg)

Influenza: An Emerging Disease (RG Webster)

Who Speaks for the Microbes? (S Falkow)

7) Resolution of clinical disagreements and controversies:

Epidemiologic principles provide the clinician a sound, rational basis on which to resolve situations where evidence, advice and beliefs conflict or are inconsistent between professionals, both veterinarians and other professionals, clinical papers, industrial technical reports and so on.

Examples of serious issues and controversies facing the profession that require these skills to resolve.

Booster vaccination frequency for small animals (annual vs. longer) (see Scientific Presentations of the 64th Annual Meeting Amer Animal Hospital Assoc, 145-156 (1977))

Hip dysplasia - OFA examination criteria vs. other (see J Am Anim Hosp Assoc 34:339-347 (1998))

Incorporation of alternative medicine modalities (e.g., acupuncture, aroma therapy, chiropractory, homeopathy) into the profession.

For the two poles of the debate, see:

NCRHI Veterinary Task Force (dead link)

Alternative, Complementary and Holistic Veterinary Medicine

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Q4: Why is the importance of epidemiology increasing?

1) The groups of animals that veterinarians deal with are getting larger.

Bigger groups usually have more potential for problems than smaller groups due to a larger number of susceptible animals and more opportunities for exposure due to factors such as more traffic in and out of the group and more batches of imported feed.

EX: Due to the pressure from the economics of scale, Washington dairy herds have gone from an average size of 30 milking cows in 1947 to 150 in 1987 to 350 in 1997. This trend of increasing size is also likely occurring for kennels, pounds, veterinary hospitals, and breeding farms because it is the natural progression for firms competing in a free-market economy.

2) The development of "evidence-based" clinical medicine in human medicine during this decade.

Evidence-based medicine (EBM): EBM is "an approach to practice in which the clinician is aware of the evidence in support of their clinical practice and the strength of that evidence" (McMaster). EBM is the use of: systematic observation of the clinical patient and the rules for empirical evidence to critically appraise and interpret information from clinical research (causation, prognosis, diagnostic tests, and treatment strategies) to apply to that individual patient.

Evidence-based medicine is essentially the application of epidemiologic principles to the practice of individual animal medicine.

The term first appeared in the clinical literature in 1992 and the number of papers using the term have approximately doubled every year, reaching 595 in 1997.

For a preview, see materials on these major EBM websites:

Evidence Based Medicine: Bridging Evidence to Practice (McMaster University Health Sciences Library Evidence-Based Practice Resources - The Origin of EBM)

NHS Research and Development Centre for Evidence-Based Medicine (Oxford)

Centre for Evidence-based Veterinary Medicine (U Nottingham)

Evidence-Based Veterinary Medicine Association (EBVMA) (transitioning)

EBVM: Evidence-based Veterinary Medicine (static 11/04)

Evidence-based Veterinary Medicine: Key concepts (pdf)

3) The rise of large multi-clinic organizations.

If these large clinic systems follow the model of their human equivalent, sets of clinical guidelines will be developed to ensure that consistent care is given throughout the organization at a minimum cost.

The success of these protocols depends upon their being developed using sound epidemiologic methods to analyzed the large clinical record database of the organization and to assess the relevant clinical literature.

Similarly, clinicians wishing to deviate from these protocols will have to provide a sound justification for doing so, which will also require an understanding of these epidemiologic principles.

4) A dramatic change in post-vet school information availability and delivery to the practitioner is currently underway.

The Old Information Model - Information Scarcity - based on paper publishing with attendant information scarcity and long time lags. Veterinarians had "the corner" on clinical knowledge. Access by non-veterinarians was difficult unless they purchased veterinary texts or had access to an academic veterinary library.

To keep up to date, practitioners:

Attended annual continuing education opportunities away from practice to meet CE hour requirements.

Cost twice - lost practice revenue generation plus expenses for attending

Could realistically subscribe to and read no more than several clinical journals, which often were stacked unread in a pile due to time limitations.

Unless valuable practice time was put into keeping a good filing system up to date, relevant papers were difficult to find when they were needed.

Kept a shelf of aging textbooks and course notes in which areas of obsolesce developed as science progressed.

Solved some problems by playing phone tag with academic experts.

The New Information Model - Wide Information Access - based on the Internet with an exploding mass of information, virtually instantaneous information exchange and the attendant chaos.

The impact of this new model on the profession and on the practice of veterinary medicine is going to be major and dramatic. The traditional model of printed journals and texts archived within academic libraries is likely going to change dramatically. Some have speculated that because of increasing costs, printed journals will disappear before long. With this new model, anyone anywhere will have virtually instantaneous access to up-to-date on-line information from around the world and to experts anywhere in the world. This includes your clients.

(For more information, see "Veterinarians and the Internet: Surfing or Drowning?" (ancient - 1997)

Examples from this new model:

Cornell Consultant: A Diagnostic Support System for Veterinary Medicine

This service, maintained by Cornell clinician Dr. Maurice White and now free on the Internet provides anyone the means to identify and to obtain by FAX (for a fee) current clinical literature on almost all the clinical diseases for all species as selected by Cornell clinicians.

MEDLINE: PubMed and Internet Grateful Med (free since July 1997)

This service provides anyone the means to identify and to read the abstracts of most of the veterinary literature. This includes your clients!

Aside: One of the most useful function of PubMed is the "Related Articles" function that locates articles related to a particular "hit".

Veterinary-oriented e-mail listservers

These provide the means for any clinician anywhere to participate in virtual clinic rounds on the problems of their choice and to contact a number of participating experts.

(The following and more are listed on NetVet at (static 1998)


Dairy-L (static 2002?)

VetPlus-L (Now VetProf?)

AVMA NOAH (Network of Animal Health)

ECN An equine clinicians email network

VIN (Veterinary Information Network)

NetVet Veterinary Resources (static 2002)

The advent of on-line journals and other Internet materials

Several medical and scientific societies (e.g., AAAS, AMA, Am Society for Microbiology) have placed all of their scientific journals on-line, where they are available for a fee. One of the factors driving this move is the increasing cost of paper publishing, which some have predicted will lead to the demise of publishing as we know it.

EX: Emerging Infectious Diseases, an on-line journal at

These have several major advantages:

With these you are now able to find and read what you want when you want it (pull technology), rather than trying to recall the specifics that you have read previously or to locate the journal issue that the article was in (push technology - when the editor decided to publish it).

These are an active format, meaning that moving images and sound can be incorporated that show time effects instead of only still graphics and photographs.

EX: You could see a new surgical technique being carried out.

The author can update the article as needed and all people reading the previous version can be notified of the update if they wish.

On-line documents can be "hyper-linked" to related information, such as related and previous papers used as references, definitions of terms, or further explanation of fundamental concepts.

Potential impacts of this new model and technology upon the profession:

The standard of practice will change from a local standard to virtually a global standard.

If it does, you will have to keep up with the emerging global information because to not do so will be considered malpractice.

Clients now have access to virtually all of the scientific information upon which clinical decisions are based.

Formerly, veterinarians effectively had the corner on professional information unless the client went to unusual lengths to find, purchase and read items such as the specialized veterinary textbooks or to search veterinary libraries.

Now, clients can checkup on the currency of your knowledge by searching the veterinary literature on-line and may have more time to do so than you do.

Point: For many clients, the veterinarian's role will likely change from being the almost exclusive holder of information to more of an information evaluator, manager and interpreter.

A potential but dangerous student presumption:

Some students may presume that one doesn't need to learn the information presented in school because it will all be readily available electronically.

This presumption is no truer in the electronic information age than it was in the printed information age.

This is a serious mistake because research on the diagnostic process shows that the majority of diagnoses are made based on questioning during the initial history taking. If one doesn't know to ask the question, one will likely miss the diagnosis.

Multi-clinic research collaboration:

With the computerization of clinic patient records, this technology enables the profession to collaborate electronically to investigate problems that profession could not address before, such as rare conditions.

The following paper is one of the first examples of a multi-clinic collaboration over the Internet:

EX: Moon PF et al. (1998). Perioperative management and mortality rates of dogs undergoing cesarean section in the United States and Canada. JAVMA 213:365-369.

Point: By applying sound epidemiologic methods, clinicians can collaborate across the Internet to obtain sound, empirical evidence to answer important clinical questions, such as which therapies work best, for those conditions that are currently lacking it.

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