Literature Searches for Luddites: A Primer
American Association of Zoo Veterinarians Conference 2006
Dalen W. Agnew, DVM
Department of Pathology, Immunology, and Microbiology, School of Veterinary Medicine, University of California, Davis, CA, USA


Luddite: one of a group of early 19th century English workmen destroying labor-saving machinery as a protest; broadly, one who is opposed to technologic change. Etymology: perhaps from Ned Ludd, 18th century Leicestershire workman who destroyed machinery.1

Be it for writing a case report, checking on a new employee’s resume, developing an Institutional Animal Care and Use Committee (IACUC) report, conducting relevant and novel research, or making a treatment plan for a clinical case (otherwise known as “evidence-based treatment”), a veterinarian’s skill in conducting a thorough review of the available medical literature can be as valuable as the ability to use a stethoscope. The resources available are considerable, though many are associated with academic institutions and not readily available to the clinical veterinarian. PubMed and multiple search engines are freely available, however, and are powerful tools and easy to use with practice. In addition, there are a growing number of journals available on-line. Most are available only by subscription or through a university, but some are free over the web. There are several excellent textbooks available for those who catch the computer “bug” and want to delve more deeply into the topic or use these tools more effectively.2,3 A review of some of the available resources and some basic search techniques will help the Luddite (or the willing, but digitally challenged) veterinarian to effectively use these resources.

Search Engines

The clinician can often benefit from resources freely available on the web. In fact, many journals are listed on both the major medical databases and on many of the commonly used web search engines. Search engines are a personal choice—every computer aficionado will have a favorite. It is best to pick one and stick to it so that you can get used to its particular grammar. On the web, there are “directories” and “crawlers.” Directories are categorized lists of sites compiled by robots or human editors. These are ideal for narrowing down a topic or finding general information on a broad range of topics but are often too broad to be useful. Examples are:

Crawlers are software programs that regularly scan the internet and index the contents of individual websites. These are perfect for hard-to-find information, but they can provide an overwhelming database of results if searches are not carefully conducted. These can return results in the hundreds of thousands! A few examples are: (VIN editor: link was not accessible as of 1/25/2021.)

Metasearches are a collection of multiple search engines that run simultaneously. These can combine the coverage of several search engines to give a very complete coverage of the internet, but they are the most likely to provide an overwhelming quantity of potentially useless information. Examples are: (my personal favorite)

Search strategies are a learned skill, but a few hints will help. It is important to choose your initial terms carefully. Use the most direct and precise words possible. For example, the term “murine” will give more scientific and/or animal sites than the term “mouse.” Time spent initially picking words carefully will be saved in the number of hits you must screen. Use the terms in the correct order: (e.g., if you enter “dog shows” you will get results on various dog shows, clubs, and events, but if you enter “show dogs” you will get specific information on dog breeds). Some punctuation marks can also assist you:

1.  The + symbol gives you all the websites with both terms listed together (e.g., veterinary+law [not veterinary law]), allowing you to concentrate your search on “hits” (also known as positive search results) where both terms occur together.

2.  The – symbol helps reduce and narrow subjects by eliminating words you do not want to associate with your word of interest (e.g., abortion–rights [not abortion rights]) gives you all the sites having to do with abortion that do not relate to abortion rights.

3.  “Quotation marks” are excellent for narrowing a search to a specific phrase (e.g., “leptospiral abortion”).

4.  These symbols can be used concurrently on the same search line.

Some search engines have other filters as well, allowing you to choose a language (e.g., English- or German-only articles) or to limit adult content (an important tool when searching for articles on reproductive diseases).

Finally, most search engine homepages have a tutorial. Spend a few minutes using the tutorial and it may save you hours later.

Medical Literature Resources

While the search engines can provide a dizzying array of information, the quality of that information may be variable, limited, or even suspect. For the best medical information (though perhaps, not the most up-to-date), the peer-reviewed literature is certainly preferable and is necessary when publishing in journals. There are many literature resources available, often geared to specific scientific fields. Unfortunately, many of these are only available through universities or are associated with expensive fees. Library privileges, however, can often be negotiated with local universities, particularly if a clinical veterinarian has an adjunct appointment. As a last resort, dating a graduate student is always an option.

Of the available medical databases, PubMed is by far the most complete, available, and for the most part, user-friendly. It covers over 4000 journals and has 11 million records back to 1966 with worldwide coverage. And best of all, it’s free. It can be found at:

Other databases available (usually via universities) and pertinent to zoo and wildlife veterinarians are:
Biosis, (VIN editor: link was not accessible as of 1/25/2021.)

Current Contents, (VIN editor: link was not accessible as of 1/25/2021.)
Web of Knowledge, (VIN editor: link was not accessible as of 1/25/2021.)
Web of Science, (VIN editor: link was not accessible as of 1/25/2021.)
Zoological Record, (VIN editor: link was not accessible as of 1/25/2021.)

However, all of these databases have subscription costs that can be quite substantial. For this reason, only PubMed searches will be discussed, though these same techniques can be used for other databases if you are lucky enough to have access.

Searching in PubMed is fairly simple, but a few tricks will help you reduce the number of references you will need to screen. To search, type a word or phrase into the query box at the top of the page ( and click “go” or press the “enter” key. Just as in search engines, term choice is crucial. Identify the key concepts you are looking for and use the most specific terms possible. Determine alternative terms, if you do not get appropriate results (e.g., search for both Toxoplasma gondii and T. gondii). You will see many of the same references with both terms, but you may see some references that are found in only one of the two searches.

PubMed has the useful quality that it will search for the term you typed as well as related terms. For example, if you type “face” as a search word, PubMed will automatically search for “cheek,” “chin,” “eye,” and “forehead.” If you want it to only search for “face,” type that word in parentheses. You can also search using truncated terms, using the wildcard symbol “*.” For example, if you want to find references on “infarct,” “infarcts,” “infarction,” “infarctions,” and “infarctive processes,” you can search using the term “infarct*” and all these terms will be included. Unfortunately, using this wildcard will turn off any of the automatic features of PubMed, which would have also identified references with the term “heart attack” in it. Finally, it will do no good to include terms such as “a,” “it,” “also,” or “these.” These terms could potentially return every document in the database and so PubMed has not indexed them.

You can connect search terms using Boolean logic. George Boole was a 17th Century mathematician who devised a logical combinatorial system composed of logical operators such as “AND,” “OR,” and “NOT.”1

AND will return only citations which include both terms.
OR will return all citations which include either term.
NOT will block citations which include the term preceded by NOT.

For example, searching with the following string of terms: “Bovine AND abortion OR endometritis NOT Chlamydia” would return citations pertaining to bovine reproductive diseases, but would not include citations in which the term “Chlamydia” appeared.

Note that these Boolean logic terms are in all capital letters. The computer will process these terms from left to right and from within parentheses, then outside the parentheses.

Once you have identified a reasonable number of references, you can alter the display. Initially, they are displayed in summary format (author, title, journal, year, volume, and pages). To view more information, you can use the menu attached to the display button to pick “abstract,” “citation,” or “MEDLINE” format. You can also select specific references (by clicking in the box by its author line) and have only those references displayed in a more complete format. You can also use this check box to send these documents to a clipboard for later review (using the “send to” button and later, the “clipboard” on the “features” toolbar). These clipboard items are, unfortunately, lost if the clipboard is inactive for more than one hour, but you can save it to your desktop or a disk. You can also use the “send to” button to put the documents in a text format that is easy to print and file a hard copy.

Adjacent to every citation, there is also a link to “related articles.” Clicking on this will pull up many articles with similar subjects as your initial search, and often turns up new and interesting articles you may have missed on the first search.

An important aspect of PubMed is “limits,” which is found on the “features” toolbar. This provides a pull-down menu for “publication type,” “languages,” “subsets,” “ages,” “human or animal,” “gender,” “entrez date (date it was added to the database),” “publication date,” and others. You can also restrict your search to only those references which contain an abstract. These limits can be turned off later by unchecking the “limits” box.

Full articles can be ordered directly from the PubMed webpage (via Loansome Doc), but this is associated with a fee and you must develop a relationship with a neighboring medical library. An additional (and free service) is the “Cubby.” You must register to use this service, but it allows you to store search strategies and update your searches (useful if you are monitoring the most current literature for a particular disease or treatment). The PubMed website also provides an excellent tutorial for the website along the left margin of the homepage.

Journals On-Line

An increasing number of journals are being published on-line as well as in print (the Journal of Zoo and Wildlife Medicine is one). These journals are rarely available as individual subscriptions, however, and are usually controlled by one of the large publishing houses that sell subscriptions providing access to a battery of related journals. These subscriptions are generally intended for libraries and large institutions. However, PubMed provides a large number of on-line journals free of charge at:

In addition, many publishers are retrospectively scanning journals and make their archives available on-line. Within one year, the Journal of Zoo and Wildlife Medicine will be one of these journals, with all issues dating back to its first volume available.

Other Favorites

The Internet is an amazing tool, regardless of who might have invented it. It can save time and resources by making information immediately available. It can, however, be a great time-waster if it is not used effectively. Hopefully, the hints provided in this article and a bit of practice will make it one of the most effective diagnostic instruments in your medical arsenal. As a parting gift, I would like to offer a few of my favorite zoo and medically relevant websites, feel free to pass on yours: (VIN editor: link was not accessible as of 1/25/2021.) (VIN editor: link was not accessible as of 1/25/2021.) (VIN editor: link was not accessible as of 1/25/2021.) (VIN editor: link was not accessible as of 1/25/2021.)
and of course,

Literature Cited

1.  Merriam-Webster OnLine.

2.  Chellen S. 2003. The Essential Guide to the Internet for Health Professionals. 2nd ed. London, UK: Routledge; 2003:256.

3.  Kienholz M. OnLine Guide to Medical Research. iUniverse. 1999:528.


Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Dalen W. Agnew, DVM, PhD, DACVP
Department of Pathology, Microbiology, and Immunology
University of California
Davis, CA, USA

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