Ultrasonographic Assessment and Ultrasound-Guided Biopsy of the Retropharyngeal Lymph Nodes in Elephants
So far there are no valid diagnostic tools available for identifying latent carriers of endotheliotropic elephant herpes virus (EEHV).4,5 For this reason, the lateral retropharyngeal lymph node complex (LARELYNOC) of elephants, identified during postmortem studies as target organ for EEHV and suitable for transcutaneous biopsy, was grossly described.3 Transcutaneous ultrasound (3.5 MHz) was applied behind the ear region to identify the LARELYNOC containing up to four single lymph nodes on each side. The lymph node tissue is situated 20–50 mm below the skin surface. An ultrasonographic assessment of the LARELYNOC and two biopsies were performed on 39 healthy Asian elephants (Elephas maximus). Samples were tested for EEHV via PCR.1,2 Whole blood samples were also collected and tested for active EEHV infection. Lymph nodes were ultrasonographically classified as active (calculated mean volume=17.4±6.9 cm3, p>0.001), inactive (calculated mean volume=3.1±0.6 cm3, p<0.001), or chronic active (calculated mean volume=10.6±1.0 cm3, p<0.05). Histology confirmed not only the presence of lymph tissue but also the ultrasonographically diagnosed reactivity status of the lymph node biopsies. Although all samples including whole blood were found to be negative for the EEHV DNA particles, the successful development of this procedure in elephants could prove beneficial for the screening of not only latent EEHV infections but might also be a less dangerous alternative method for the diagnosis of zoonotic infections such as tuberculosis.5
The authors like to acknowledge the German Research Council and the Thai government for funding this project. The authors are grateful for additional financial support by the African Lion Safari, Cambridge, Canada and the Zoo Zurich, Switzerland. The authors also thank the staff of all facilities contributing with their help and expertise.
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