September 2005 Issue

Featured Case Study: Four-year-old mixed-breed female dog, Riley
Terri Wheeler, DVM, MS

Presentation

Signalment: Four-year-old mixed-breed female
Presenting complaints: Routine physical exam
Physical exam: Normal
Serology: E. canis-positive on the SNAP® 3Dx® Test

The veterinarian used the recommended IDEXX clinical approach to a SNAP 3Dx E. canis-positive and performed a CBC and, in this case, a chemistry profile, on Riley.

Interpretive Summary

Hematology
The quantitative results of the CBC reveal a pancytopenia characterized by a thrombocytopenia, leukopenia and nonregenerative anemia. In addition to overwhelming inflammation, which is not likely considering the normal clinical presentation, potential decreased or ineffective bone marrow production infection with agents such as Ehrlichia canis (E. canis) must be considered. Evaluation of the peripheral blood film reveals no significant left shift in the neutrophil compartment, which is additional support for decreased production or ineffective production at the bone marrow level. Blood-film evaluation also confirms the thrombocytopenia since only 1–3 platelets are noted per 100x objective field-of-view (see Figure 1). Additionally, large platelets are noted, suggesting bone marrow response to a peripheral demand with an increased rate of thrombopoiesis, rather than decreased production. This is further support for potential infection with an agent such as E. canis.

Blood-Film Evaluation
The blood film pictured is a 100x objective field-of-view Wright’s stain (Figure 1), which demonstrates that the decreased density of platelets supports the instrument-reported thrombocytopenia. In addition, the single platelet, seen in this field of view is enlarged, which is evidence of bone marrow response to a peripheral demand for platelets, rather than decreased production as a mechanism of thrombocytopenia. Note that erythrocytes are morphologically normal and that no leukocytes are seen in this field of view, which also supports the finding of leukopenia in the instrument-generated quantitative hematologic values.

Biochemical Profile
The only significant chemistry profile abnormalities include hypoalbuminemia and hyperglobulinemia. The hyperglobulinemia is most likely related to chronic antigenic stimulation, which is consistent with chronic E. canis infection. The most common cause for mild hypoalbuminemia is a decrease in albumin associated with inflammatory disease; however, causes such as loss through the kidney or decreased production by the liver must also be considered.

Diagnosis
E. canis infection

In light of the positive E. canis result on the SNAP® 3Dx® Test, the severe thrombocytopenia and the nonregenerative anemia, the dog’s diagnosis is E. canis.

Additional Recommended Diagnostics
Co-infections with tick-borne diseases are quite common. Screening for additional tick-borne diseases would be prudent. Organisms such as Anaplasma phagocytophilum, E. ewing, and Rickettsia rickettsii can also show similar clinical signs. A complete urinalysis investigating the possibility of protein-losing nephropathy, and if there is a suspected proteinuria, performing a urine protein:creatinine (UPC) ratio, would be indicated.

Treatment/Plan
At least a one-month course of doxycycline at 10 mg/kg/day should be initiated immediately.

• Repeat CBC within 72 hours to ensure platelet numbers are returning to reference-range values.
• Repeat CBC in 7–10 days to ensure that all parameters (including platelet count, hematocrit and leukocyte count) and distribution are returning to reference-range limits.

Prognosis
The lack of petechia and epitaxis, and the fact that the dog is still eating and active, indicates a good prognosis for Riley. Dogs in the acute stages of E. canis infection usually respond quickly to antibiotic treatment and supportive care. However, with severe thrombocytopenia and anemia, the dog’s response must be followed closely to ensure that the platelet count and hematocrit return to the normal reference range following antibiotic treatment. Dogs that are in the chronic stage of E. canis infection that present with clinical signs have a more guarded prognosis.

Prevention
Prevention of E. canis infection includes using tick preventatives.

Zoonotic Potential
Since pets share our environment, they may incidentally become sentinels for disease. Although E. canis has only rarely been isolated in humans and has questionable clinical significance, the owner should be aware of other potential human tick-borne diseases in the area.

The recommendations contained in Diagnostic Edge educational materials are intended to provide general guidance only. As with any diagnosis or treatment, you should use clinical discretion with each patient based on a complete evaluation of the patient, including history, physical presentation and complete laboratory data. With respect to any drug therapy or monitoring program, you should refer to product inserts for a complete description of dosages, indications, interactions and cautions.

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September is Senior Care Month—enjoy two specials on senior care from IDEXX

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Education and Events

We offer a variety of seminars and teleconferences about emerging trends and best practices in veterinary diagnostics—in a forum designed to involve, educate and motivate you and your staff.

Here are some of the educational events in September:

• A Practioner's Approach to Feline Retroviruses by Lynn Buzhardt, DVM
• Blood-Film Evaluation in Dogs and Cats by Rick Alleman, DVM, PhD, DAVBP, DACVP
• Canine Lyme Disease for the Canine Practioner by Steven Levy, VMD
• Vector Borne Diseases in Small Animals by Terri Wheler, DVM, MS

Visit the seminar and teleconference calendar, click the date to view the details, fill out and submit the form to register.

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Make the most of senior care client brochures when speaking with your clients

With Senior Care Month upon us, many of you will be discussing wellness testing with your clients. One of the best ways to help get your message across is to use a brochure. A brochure provides support for your recommendation, and that goes a long way in the eyes of your clients.

Having brochures available in your waiting area does not mean that your clients will pick them up or ask for the product or service that the brochures recommend. The most effective way to use a brochure is for you to take a moment to sit down with your clients to discuss several key areas of the piece and then hand it to them personally.

Since almost all veterinary industry manufacturers and associations offer materials on senior wellness (most of them free), ask several of your sales representatives or look online for those available to you, and choose the one that best fits your style. After you have chosen a piece, decide which points you would like to highlight when talking with clients. It helps to practice. The more comfortable you are talking about the piece, the more confident your clients will be with your recommendations and the better chance your patients will receive the care they need.

The IDEXX Senior Care brochure (495 KB) is designed to make senior care discussions with clients easy. It has an age chart, a list of common medical conditions, a checklist of signs to watch for and a place to record the next appointment. To place an order, call IDEXX Customer Support at 1-800-248-2483 For a complete list of IDEXX Senior Care offerings, contact your local IDEXX representative.

Good luck and have a great Senior Care Month!

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Test your senior care knowledge

Send your answer in an e-mail to: diagnosticedge@idexx.com. Please include your name, practice name, address and telephone number.

The first 10 respondents to identify all four questions correctly will appear in the next issue of the Diagnostic Edge.

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