Elephant Endotheliotropic

Herpes Virus-Hemorrhagic

Disease (EEHV-HD)

Compiled by Willem Schaftenaar

History:

EEHV-HD is caused by a delta-herpesvirus. The virus has evolved with the elephant species and is older than the currently living elephant species. Most (if not all) adult elephants are latently infected with EEHV.

Young elephants between 1 and 9 years of age can be susceptable for an often fatal syndrom: EEHV-Hemorrhagic Disease. It is hypothesized that the long half-lifetime of maternal antibodies (EEHV maternal antibodies can circulate for up to 36 months in a calf) protects the calf against developing this syndrome. If this is true, it means that calves need to be exposed to EEHV during the phase in which antibodies are decreasing, but still protecting the calf.

​Fatal cases in Asian elephants have been reported over 20 times more than in African elephants. One of the hypotheses is that African elephant are shedding the virus much more frequent than Asian elephants, which offers a better opportunity for the calf to build up a solid immunity during the period that it is still protected by maternal antibodies.

​Asian elephants can carry EEHV1a, EEHV1b, EEHV4 and EEHV5, of which EEHV1a has caused the vast majority of the fatal cases.

African elephants can carry EEHV2, EEHV3a, EEHV3b, EEHV6 and EEHV7. EEHV3 has been associated with fatal cases, while the other African EEHV-subtypes are associated with lymphoid nodules in lungs and skin of African elephants. There is one report of a fatal case caused associated with EEHV3 in an Asian elphant.

​Like all herpesviruses, EEHV has a latent phase in an so far unknown tissue of the elephant body. For reasons that are not yet known, the virus can be reactivated, probably due to a (temporary) weakening of the elephant's immune system. The virus migrates to the mucous membranes of the mouth, trunk, eyes and the female genital tract. Shedding in semen or mucous membranes of the penis has not yet

been reported.

 

Symptoms and diagnosis:

10-14 days before the elephant shows external symptoms of EEHV-HD, the presence of the virus can be demonstrated in the blood by qPCR (EDTA blood sample). It is important to monitor the presence of EEHV in calves between 1 and 9 years of age on a weekly base. As soon as the presence of EEHV has been confirmed, the number of monocytes and platelets are indicative for the further development of the virus in the days to come. When monocytes and platelets are stable and the viral load remains below 5.000 Viral Genome Equivalents (VGE's)/ml, close observation is required. As soon as the viral load in the blood increases or monocytes or platelets drop, immediate treatment is required.

           

The most relevant tools needed for the diagnosis of EEHV-HD are: qPCR and total WBC, platelet count and blood smear (manual count of monocyte and heterophyls). The monocyte/heterophil (M/H) ratio is an important prognostic indicator for EEHV-HD. A ratio below 1 is reason for great concern and immediate treatment should be started.

Photo: courtesy of Florence Ollivet-Courtois

Photo: courtesy African Lion Safari Park

Photo: courtesy Amersfoort Zoo

Click here for the EAZA elephant TAG EEHV treatment protocol

Treatment of EEHV-HD

Early treatment of EEHV-HD is essential for the survival of the elephant. The list of recommended drugs is shown below. The clinician should not hesitate to administer all these drugs and should even sedate the sick elephant if needed for its treatment. Repetitive sedations have been given to sick calves without negative effects.

Circulatory support:

Rectal fluids:         

Luke-warm water 10-20 ml/kg BW TID or QID, up to every 2 hours

Crystalloids:           

IV as a bolus of 0.3-4 ml/kg BW

Plasma transfusion:

IV bolus of 0.5-2 ml/kg BW (after minor cross matching of donor and recipient blood)

 

Plasma transfusion in elephants

 

In: Emergency care for elephants clinically ill from Elephant Endotheliotropic Herpes Virus–hemorrhagic disease (EEHV-HD, EAZA Elephant TAG, compiled by Fieke Molenaar (ZSL-Whipsnade zoo), Mads Bertelsen and Kathryn Perrin (Copenhagen zoo), Imke Lueders (GEOLifes), Lauren Howard (Houston zoo), Willem Schaftenaar (vet adv. EAZA Elephant TAG, 9 February 2021)

 

Plasma is currently considered one of the best supportive therapies to provide, as platelets, clotting factors and potentially protective antibodies can thus be provided. Note that the freezing process activates platelets, which renders them useless at the time of transfusion. Therefore - where possible - freshly collected plasma is preferred. The following should be considered for plasma transfusions:

  • If frozen plasma is available, this can be given in an early stage of the disease to save time (despite the activated and spent platelets).

  • Blood collection from an adult elephant (plasma donor) should be initiated to provide fresh plasma as soon as possible.

  • Cross-matching the donor animals with the recipients, especially if one donor will be used on multiple occasions.

 

For more information about plasma transfusion: click here

Antiviral treatment:

Several antiviral drugs are routinely used, although none of these have proven to be effective; preliminary studies are suggesting that the TK-gene of EEHV does not make the virus sensitive for the group of “ciclovirs” that is currently used. Famciclovir has been used most frequently, followed by ganciclovir. In the absence of the former antivirals, aciclovir has been

Famciclovir: 15 mg/kg orally or rectally, TID

Ganciclovir: 5 mg/kg BW BID 5 mg/kg IV, BID, each dose given slowly diluted in 1 liter of NaCl.

Aciclovir: 15 mg/kg BID orally, rectally or IV

Antibiotic treatment:

A broad-spectrum antibiotic is recommended as the integrety of the intestinal wall may be disrupted and gut bacteria may leak into the abdominal cavity.

Pain management:

Pain management (opioids, NSAIDs) is recommended if there are clear signs of pain or discomfort

Butorphanol: 0.008-0.014 mg/kg IM Q 4 hrs

Flunixin: 0.25 to 0.5 mg/kg IM SID

Omiprazole: 0.7 to 1.4 mg/kg PO SID

Anti-inflammatory treatment:

Gluco-corticosteroid drugs are indicated in case of suspicion of DIC.

Dexamethasone: 0.05-0.1 mg/kg IV or IM SID for 1-3 days. Please note that in human medicine DIC (e.g. in Covid-19 cases) is treated with Dexamethasone 0.1mg/kg SID for 7-10 days (https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-dexamethasone#:~:text=Recommendation%201%3AWHO%20strongly,medication%20for%20another%20condition.)

Triamcinolon: 0.067 mg/kg IV SID for 1-3 days

Immunostimulating drugs:

Immunostimulants have been used in one case of EEHV1a-HD: Interferon alpha 2a or 2b (25 mIU/2.5 ml IntronA, Merck or 4.5 mIU/0.5 ml Roferon A, Roche) were administered at 27–33 mIU intramuscularly once a day on days 1–12 then every 48 hours to day 20, administered by dart on days with no treatment session, incomplete delivery on days 8 and 14. Bacterial plasmid DNA in a liposome carrier (Zelnate DNA immunostimulant, Bayer HealthCare LLC) was given to the same elephant (2 ml intramuscularly on days 0, 4, 7 and 12).

It should be noted that the same elephant was also given anti-inflammatory treatment (dexamethasone).

Adjunctive drugs:

Oxygen

Furosemide (1 mg/kg IM )

Vitamin C (commonly used in Asia)

 

Treatment of EEHV-HD

Cross-matching procedure

Based on design elaborated by Houston Zoo, Inc.

 

Step one:  Prepare a 3-5% red cell suspension.

1. Collect blood from both donor and recipient in EDTA.

2. Centrifuge the tube and separate the plasma from the red cells.  Save both.

3. Place 1 drop of recipient red cells into a small (2-5 ml) clean test tube.

4. Add approx. 1-2 ml of normal saline to the tube with the red cells (or 1 drop RBC to 40 drops saline)

5. Centrifuge at 2500 RPM for 20 seconds.

6. Remove the supernatant, leaving the red cell button on the bottom.

7. Repeat steps 4-6 three times (for a total of 4 washes).

8. Add 1 drop of newly washed recipient red cells to a new test tube.

9. Add approximately 20-40 drops of saline and mix to suspend the red cells.  This should be an approximate 3-5% cell suspension to work with.

 

Step two:  Minor cross-match (for plasma transfusion).

1. Add 1 drop of the recipient’s 3-5% red cell suspension to a labeled test tube. Add 1 drop of the recipient’s 3-5% red cell suspension to another labeled test tube to be used as a control.

2. Add 2 drops of donor plasma or serum to the test tube.

3. Add 2 drops of saline to the control tube.

4. Incubate these tubes at 37oC for 15 minutes.

5. Centrifuge the tubes for 20 seconds at 2500 RPM.

6. Observe the supernatant for signs of haemolysis. If present in the cross-match tube and not the control tube, the match is not compatible.  If present in both, start again with a new cell suspension.

7. If no haemolysis, then gently rock the test tube back and forth to re-suspend the cell button. Observe the cell button while rocking the tube and grade for the presence of agglutination. Grade on a 0-4 scale where 0 is no agglutination and 4 is heavy clumping. Record your results.

 

Step three:  Major cross-match (for whole blood transfusion).

1. Add 1 drop of the donor’s 3-5% red cell suspension to a labeled test tube. Add 1 drop of the donor’s 3-5% red cell suspension to another labeled test tube to be used as a control.

2. Add 2 drops of recipient’s plasma or serum to the test tube.

3. Add 2 drops of saline to the control tube.

4. Incubate these tubes at 35-37oC for 15 minutes.

5. Centrifuge the tubes for 20 seconds at 2500 RPM.

6. Observe the supernatant for signs of haemolysis. If present in the cross-match tube and not the control tube, the match is not compatible.  If present in both, start again with a new cell suspension.

7. If no haemolysis, then gently rock the test tube back and forth to re-suspend the cell button. Observe the cell button while rocking the tube and grade for the presence of agglutination. Grade on a 0-4 scale where 0 is no agglutination and 4 is heavy clumping.  Record your results.

 

References:

  • Fuery et al. 2020. Fuery A. et al. 2020. Lethal Hemorrhagic Disease and Clinical Illness Associatedwith Elephant Endotheliotropic Herpesvirus 1 Are Caused by Primary Infection: Implications for the Detection of Diagnostic Proteins. J. Vir. Volume 94 Issue 3.

  • Wissink N. et al. 2018.Using in-house hematology to direct decisionmaking in the successful treatment and monitoring of a clinical and susequently subclinical case of Elephant Endotheliotropic Her Vitus 1B.  J. of Zoo and Wildlife Med., 50(2): 498-502

  • Luz S & Howard L.L. 2017. Elephant Endotheliotropic Herpesvirus (EEHV) in Asia. Recommendations from the 1st Asian EEHV Strategy Meeting (On behalf of the Asian EEHV Working Group), second edition.

  • Howard L.L. & Schaftenaar W. 2017. Elephant Endotheliotropic Herpes Virus. In: Fowler’s Zoo and Wild Animal Medicine Current Therapy, Volume 9.

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