Technical Services Inquiries

Scott Adams, D.V.M., Ph.D., President and CEO | Apr. 2006

Ehrlichia canis – 

Question: Why is the IFA positive using VMRD E. canis substrate slides while with the same sample I get a negative reaction with an E. canis lateral flow device?

Answer: IFA has broader reactivity than the lateral flow assay. The lateral flow assay detects antibody to E. canis only. The IFA will detect antibody to E. ewingii and E. chaffeensis as well and perhaps to other Ehrlichia spp. yet to be identified.

Clostridium novyi species reclassification – 

Question: Does VMRD’s C. novyi Direct FA conjugate (Catalog Nos. 210-16-CN & 210-17-CN) react with C. haemolyticum ?

Answer: We have recently learned that Clostridium novyi and Clostridium haemolyticum have been reclassified as very similar, if not the same organism. Thus, our C. novyi (B) direct FA conjugate will react with both C. novyi and C. haemolyticum organisms.

Anaplasma marginale-Anaplasma phagocytophilum cross-reactivity – 

Question: A recent paper out of Switzerland [Dreher et al.] documents serologic cross-reactivity between A. marginale and A. phagocytophilum using VMRD’s cELISA and IFA for the aforementioned agents, respectively. What is VMRD’s position with respect to the meaning of data derived from either assay?

Answer: From the time that VMRD began marketing the cELISA for detection of antibody to Anaplasma in cattle it was known and we readily acknowledged in our literature and product insert that it was designed to detect antibody to Anaplasma spp. not A. marginale only. This was based on work previously published about MSP-5, major surface protein-5 of Anaplasma spp. by Visser et al. The species specifically mentioned at the time were A. marginale, A. centrale and A. ovis. Furthermore, the cELISA has been shown to detect antibody to A. ovis in goat sera [Ndung'u et al.]. Thus it is not surprising to find that another species, A. phagocytophilum, which has recently been reclassified from an Ehrlichia to an Anaplasma spp., would also induce antibody capable of inhibiting binding of the monoclonal antibody used in the cELISA, thus giving a positive result. Therefore, as indicated from the beginning, VMRD’s cELISA is a genus specific test for Anaplasma .

Bovine Herpesvirus 1-Bovine Herpesvirus 5 cross- reactivity – 

Question: Do any of VMRD’s BHV-1 monoclonal antibodies react with BHV-5?

Answer: Yes. The table below shows the results of IFA tests against our isolates of BHV-1 and BHV-5. Only F2 does not react with BHV-5. L6G reacts only with BHV-5 and not BHV-1.