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Featured case study:
Six-month-old female mixed-breed puppy, Faith
by Matthew Eberts, DVM, Lakeland Veterinary Hospital, Baxter, Minnesota
History
Faith was found as an abandoned puppy and taken to the local animal shelter. Upon arrival she was in poor body condition. She was dewormed, vaccinated, and placed on an appropriate diet. Shortly after arrival she developed a cough that was consistent with canine infectious tracheobronchitis (ITB). Fortunately Faith had a very sweet personality and was adopted quickly. The shelter’s policy is to sterilize all dogs before adoption so Faith was spayed and discharged to the new owner the following day. Within 48 hours, Faith became increasingly lethargic, refused to eat, and developed a purulent nasal discharge. The morning of her examination she showed dramatic lameness and was unwilling to move.
Physical exam
- Weight: 13.2 kg
- Temperature: 104.3° F
Depressed but responsive. Bilateral mucopurulent nasal discharge with a productive cough elicited on tracheal palpation. Abdominal incision from ovariohysterectomy appears within normal limits. Faith is markedly lame on right front and left hind legs. Palpable effusion on right and left radio-carpal joints, the left stifle, and the right hock joint. All joints with effusion are painful on manipulation.
Plan
CBC, SNAP® 4Dx®, thoracic radiographs, abdominal radiographs and abdominocentesis.
Erythron—Mild normocytic, normochromic anemia. This is most consistent with the anemia of inflammatory disease, the most common type of anemia seen in dogs. The slight increase in MCHC is most commonly seen with slight in vitro hemolysis, hemolysis that may not be detected visually when examining the plasma. The slight increased RDW suggests slight anisocytosis.
Leukon—Marked leukocytosis characterized by a neutrophilia and monocytosis. Analysis of a blood smear showed a moderate left shift (7% band neutrophils) with some toxic changes in the neutrophils. No infectious agents or inclusions were noted. This is consistent with severe inflammation with evidence of a demand for macrophages (monocytosis).
Thrombon—The platelet count is within reference interval limits. Although a reference interval for PDW is not provided, PDW values greater than 15–20% are commonly seen when there is significant variability in size of platelets. This is a common finding in dogs with inflammatory disease.
SNAP® 4Dx® Test
Faith had polyarthropathy on exam, which prompted in-house screening for tick-borne infections. Lyme disease and anaplasmosis are endemic in Minnesota. Faith was positive for Lyme and anaplasmosis, indicating exposure to both Borrelia burgdorferi and Anaplasma phagocytophilum. She was negative for heartworm disease and Ehrlichiosis. Since granulocyte inclusions were not seen on a blood smear, it is not possible to tell if Faith had an active Anaplasma infection. A PCR test could have been performed to document active infection.
Thoracic radiographs
With the fever, coughing, and purulent nasal discharge, bronchopneumonia was on the initial differential diagnostic list. The radiographs were within normal limits with no signs of pulmonary lesions.
Abdominal radiographs
With the recent ovariohysterectomy, high fever, anemia and extreme leukocytosis, septic peritonitis and abdominal hemorrhage were differential diagnoses. The abdominal radiographs were within normal limits.
Abdominocentesis
This was performed by simultaneous abdominal puncture using two 1½-inch 22-gauge needles. No fluid was collected. This is a rapid, inexpensive low-morbidity test that allows collection and characterization of abdominal fluids. In this case it was important to rule out septic peritonitis since this would have required aggressive (potentially surgical) management.
Diagnosis
ITB with purulent rhinitis, arthropathy likely triggered by Lyme and anaplasmosis co-infection.
Further diagnosis
A quantitative C protein titer (Lyme Quant C™ Test) was submitted. Results showed C antibody = 68 µ/L.
Clinic case management
Faith was started on doxycycline 100 mg orally, twice daily for 28 days. Within 24 hours her fever had resolved and she began to eat. Within 48 hours she was ambulating more normally and in 96 hours was showing no visible lameness. The mucopurulent nasal discharge began abating within 48 hours and resolved by day five of antibiotic therapy. Her coughing rapidly improved and she showed resolution within 10 days of exam.
A follow-up CBC was performed 16 days following initial presentation:
Erythron—Faith shows a hematocrit of 33.1%, which can be considered low-normal for a puppy. The hemoglobin is high for the hematocrit reported (hemoglobin x 3 should result in a value similar to the hematocrit) and the MCHC is high and outside the reportable range. This is most commonly seen with either slight in vitro or in vivo hemolysis. Since the hematocrit has increased compared to the presenting CBC, in vitro hemolysis is most likely. The RDW is returning to within reference interval limits suggesting less anisocytosis than on the presenting CBC.
Leukon—Normal, the leukocytosis has resolved.
Thrombon—Normal
Faith’s physical exam at that point was completely normal and a follow-up Quant C antibody level test is planned in six months to confirm response of Lyme infection to doxycycline therapy.
Discussion
Faith was very unfortunate in that she experienced practically every single stress possible to her system prior to placement in a new home! Before coming to the shelter, she had been living outside in a Minnesota winter with inadequate nutrition. She had been exposed to both Borrelia burgdorferi and Anaplasma phagocytophilum (from presumptive Ixodes scapularis tick bites). She was taken to an animal shelter and immediately infected with ITB. She was placed under general anesthesia for ovariohysterectomy, which further compromised her immune system. This was the final factor that induced severe clinical disease.
It was clear on her presentation that Faith suffered from infectious disease, but the clinical challenge was to correctly diagnose the sources of infection. Due to the severity of her illness, the goal was to perform diagnostics that would rapidly narrow the differential diagnoses and allow immediate therapy. I strongly believe that in-house diagnostics add tremendous value to case management by giving the clinician immediate results. For Faith, critical decisions regarding antimicrobials and supportive care needed to be made right away.
Bordetella bronchiseptica, Mycoplasma species and Streptococcus species have all been identified as bacterial components of ITB. Faith had both serologic evidence of Lyme and anaplasmosis co-infection and compatible clinical signs. Thus, doxycycline was a reasonable empiric antibiotic choice. She responded very rapidly to doxycycline. Clinical response to treatment is the most important factor in case management and Faith responded beautifully. The follow-up CBC showed resolution of leukocytosis and correction of the anemia. The quantitative C6 antibody will allow measurement of Faith’s response to Lyme treatment. A baseline sample was submitted and follow-up samples will be collected in six months. The goal is to see a 50% reduction in the C6 antibody level.
Infectious diseases are often opportunistic and Faith provided the ultimate opportunity for several different infections. The immune system can handle only so much compromise, and co-infections make disease more likely. Faith’s therapy required proper antimicrobial therapy in addition to resolution of underlying stresses to her immune system. Faith was adopted by a wonderful owner and is now in a stable, warm environment with great nutrition. I personally would not have recommended an ovariohysterectomy while she was fighting ITB, but the shelter’s policy is to have all pets sterilized before they leave the facility, which is understandable.
Clinical case outcome
Fortunately Faith made a rapid and uneventful recovery.
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