News : 2017 : March

Case of the Month: From the Lab Bench

The Case of the Prognostic Value of CRP in a Rabbit with Suspected Encephalitozoon cuniculi infection. Dr. Carolyn Cray presents the new Case of the Month. Impressive IgM and IgG titers as well as an elevated C-reactive protein (CRP) were observed in the initial evaluation of a rabbit with head tilt and ataxia. Antibody was quite long lived but the CRP decreased with clinical improvement.

Clinical history – A 2 year old male dwarf rabbit presented with neurological signs including head tilt and ataxia. The duration of the clinical signs was approximately 1 week. A sample was submitted for E. cuniculi testing. The initial results were as follows:

  • IgM – 1:64 – considered the first significant titer
  • IgG – 1:4096 – considered a very strong titer; often observed with neurological presentation
  • CRP – 196 mg/L (normal range 0-20)

The animal was treated with fenbendazole and the animal was retested at day 39. Clinical signs had improved but not completely resolved. At this time the results were as follows:

  • IgM – 1:64
  • IgG – 1:2048
  • CRP – 171 mg/L

Another course of treatment ensued and the animal appeared to respond fully to treatment. A final sample was submitted at day 128.

  • IgM – < 1:64
  • IgG – 1:1024
  • CRP – 18 mg/L

Interpretation of titers – IgM titers are not as profoundly increased as IgG titers and should signify acute or active infection. In this case, the IgM antibody persisted with the observation of the clinical signs. In experimental models of infection, IgM can be detected for an extended period. Anecdotally, we generally observe a decrease in IgM as noted in this case. IgG titers are extremely long lived and while a decrease IgG is expected, the timetable for a decrease appears variable. Recheck of titers alone may not have immediate value unless clinical signs persist. A recheck of IgG may have value at some point distant to the recovery of the patient to establish a new baseline in the event that E. cuniculi serology needs to be performed at a future date.

Interpretation of CRP levels – C-reactive protein is a major acute phase protein in the rabbit. The reference interval is 0-20mg/L. Clinically abnormal rabbits will vary in CRP levels. High values often exceed 200mg/L. Acute phase proteins are not present or present in low levels in normal animals. Increases can occur within 24 hours of insult. With a positive response to treatment, levels can drop rapidly. In this case, with a suspected prolonged course of infection, there was a mild decrease at the first recheck. The final result showed the prognostic value of measuring CRP. In this case, given mild changes in IgM and IgG titers, CRP results reflected the efficacy of the treatment addressing the systemic inflammatory process. It should be noted that CRP is not specific for E. cuniculi and can increase with infection, inflammatory disease, neoplasia, trauma, and stress.

See more updates on_E. cuniculi _testing.