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9 Questions & Answers on Diagnosing Ehrlichiosis Canis

9 Questions & Answers on Diagnosing Ehrlichiosis Canis
Ehrlichiosis Canis by Dr Revital Netta

Get the information you need on the challenges of diagnosing E.canis and on the available point-of-care test kits that can assist you in making the right decisions for your patients 

 

In Biogal’s latest webinar, “Ehrlichia Canis In-Clinic Diagnosis” on the challenges of diagnosing Ehrlichia canis (E.canis), Dr. Revital Netta went over the clinical aspects of the disease in general veterinary practice and on the most common in-clinic diagnostic protocols in conjunction with serology and PCR. The following 9 questions were asked during the webinar and were hand-picked by Dr. Netta who answered them (as well as several other questions) in collaboration with Dr. Trevor Waner.

 

1- Can in-house tests be helpful when diagnosing a disease?

Yes, but some points need to be considered when using available point-of-care test kits, such as serology and PCR.

 

Biogal’s products include:

  1. ImmunoComb Antibody Test Kit – produces semi-quantitative results that can demonstrate a four-fold rise in titer as proof of an active disease rather than a previous exposure. In addition, during the chronic phase, it can demonstrate high score results in titer as expected in such a longitudinal exposure.  
  2. PCRun– PCR can detect E.canis as early as 4-10 days post-infection. In subclinical and chronic phases the rickettsia might not be found in the patient’s blood, but it can be found in the bone marrow and/or spleen (the spleen seems to be the last organ to harvest E.canis- (Harrus, S et al, 1998)).

 

2- What is the possible cause of a false-positive result when using serology to detect Ehrlichiosis?

  1. Previous exposure – in acute and subclinical phases, when recovery occurs w/o treatment, the anti-E.canis antibody can persist up to 3-5 years post-exposure (begins to drop 6-9 months post-exposure).
  2. Cross reaction mainly with other Ehrlichia organisms such as Ehrlichia chaffeensis, Ehrlichia E. ewingii, and A. phagocytophilum (not with Anaplasma platys). Exposure to such species should be considered in light of the suspected dog’s geographic residential area and travel history.

 

3- How many days post-infection would be ideal to run an IgM serology test to reduce the odds of a false-negative result when no PCR is available?

PCR is able to detect E.canis as early as 4-10 days post-infection.

IgM is not considered a reliable indicator of E.canis exposure due to the inconsistent development of IgM antibodies in the course of the disease.

When using IgG, the antibodies are expected to rise around ±10 days post-infection and could persist up to 3-5 years when recovery occurs (w/o treatment). With that being said, a previous exposure (possibly a false-positive result) or late responders (possibly a false-negative result) should be taken into consideration. A rising four-fold titer between 2 tests 7-14 weeks apart is highly suggestive of a recent ongoing infection.

 

4- Can cats have Ehrlichiosis? If so, what signs would we expect to see in cats?

Clinical manifestations of Ehrlichiosis have been seen in cats with consistent E.canis infection laboratory findings, which responded to common anti-Ehrlichial drugs. In addition, suspected morula/ E.canis-like DNA/ positive E.canis/ N. risticii serology results were found.

*Ewingii, E. chaffeensis, and A. phagocytophilum have also been described in cats.

 

5- Considering the fact that E.canis is a bacteria/rickettsial disease, what are the possibilities of diagnosing E.canis using a rapid test?

Assuming you’re asking about yes/no serological tests:

Those tests are based on E.canis IgG* antibodies detection. Therefore, a previous exposure (a possibility of a false-positive result) or late responders (a possibility of a false-negative result) should be taken into consideration.

To overcome that, a demonstration of a rising titer with another semi-quantitative/quantitative method, taken between 2 tests 7-14 weeks apart, is highly suggestive of a recent infection.

In addition, during the chronic phase, those methods can also demonstrate high score results in titer as expected in such a longitudinal exposure. 

*There is no IgM test for E.canis – IgM is not considered a reliable indicator of E.canis exposure due to the inconsistent development of IgM antibodies in the course of the disease.

 

6- Are PCRun tests semi-quantitative or just qualitative?

PCRun tests can be semi-quantitative/qualitative depending on the method used (from the two available methods). Read more about Biogal’s options when using PCRun.

 

7- Can Biogal’s tests be used on cats?

ImmunoComb, which is based on serology, is compatible with dogs only. PCRun, however, can be used on both dogs or cats for the detection of E.canis.

 

8- What interval should you take between two IgG tests?

In order to detect an acute infection, compare the E.canis IgG titers after 7-14 days. In the case of an active infection, the titer should increase four-fold.

 

9- For a chronic active infection should we still expect an increase in antibody titer?

The high titer will remain stable without a rise of four-fold in titer. In addition, during the chronic phase, the titer levels should be very high as expected in such a longitudinal exposure. 

When it comes down to it, diagnosis of E.canis can be sometimes challenging due to its different phases, coinfections with other vector-borne disease pathogens (VBDP), and multiple clinical manifestations. For more information on Biogal’s point-of-care tools for the diagnosis of E.canis make sure to check out the ImmunoComb Canine Ehrlichia Antibody Test Kit and the PCRUN Ehrlichia canis Molecular Detection Kit

You can get more information by watching the entire webinar and don’t forget to sign up for our next one. 

 

Trevor Waner BVSc MSc Ph.D. Dipl ECLAM:
Trevor graduated from Pretoria University, South Africa in 1971. He worked for the PDSA in District Six, Cape Town, before continuing his studies at the University of Cape Town, graduating with an MSc degree in Virology. He emigrated to Israel in 1977 and worked at the Soroka Medical Center in Be’er Sheva in the Department of Comparative Medicine. After joining the Israel Institute for Biological Research, he completed his Ph.D. in Infectious Diseases in 1999 at the University of Utrecht. His thesis dealt with the diagnosis of canine monocytic ehrlichiosis. He is a European Recognised Specialist in Laboratory Animal Medicine and runs a small animal veterinary clinic. Trevor is widely published and has lectured at a number of international conferences.

 

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