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EEHV

A HEARBREAKING ELEPHANT UPDATE

We are heartbroken to share that our 7-year-old African elephant, Ajabu, passed away on Monday evening after a 12-day battle with the devastating viral infection known as elephant endotheliotropic herpesvirus (EEHV). This was his second fight with this insidious disease – he previously faced an active case of EEHV in March 2021 and survived. For more information on Ajabu’s initial bout with EEHV, see this video. 

Despite the round-the-clock care and heroic efforts of his animal care and veterinary teams for 12 days, along with support from zoo teams across the country, Ajabu laid down in the barn in the evening of Monday, May 8 and simply could not fight any longer.  

EEHV is carried naturally by African and Asian elephants and affects elephants living in the wild, as well as in human care. It is an all-too-often lethal disease that tends to be most severe in young elephants from one year of age into the animal’s teenage years.  

Ajabu’s active case initially showed up on Thursday, April 27, during the course of regular blood testing we conduct on our entire elephant herd. Ajabu’s sample revealed a slightly elevated EEHV viral load. Though he showed no physical signs or symptoms of EEHV, the team immediately began proactive treatment to try to stem the progression of the virus.   

Ajabu’s treatment over the next almost two weeks included administering antiviral and antibiotic medications, fluids to prevent dehydration, immune stimulants, anti-inflammatories, and transfusions of fortified whole blood, plasma, and stem cells.    

We are only beginning to process the loss of this amazing ambassador for his species. He surprised us all with his entrance to the world following the rescue of elephants, including his mother, Mlilo, from Swaziland in 2016, and now we have lost him much too soon. Please lead with compassion and kindness, and hold the entire Dallas Zoo family close to your heart as we navigate through the difficult days ahead.  

EEHV FAQs

  • EEHV (elephant endotheliotropic herpesvirus) is a type of herpesvirus that can cause fatal hemorrhagic (bleeding) disease in elephants.  

  • This devastating viral infection is one of the deadliest diseases in elephants worldwide, both in the wild and in human care. 

  • The virus is carried naturally by Asian and African elephants – it is thought almost all elephants are either born with, or exposed shortly after birth to, EEHV. The virus often remains dormant but may activate in individuals when their immune system is developing.  

  • Research is ongoing but there is still much to learn before we fully understand this disease and how and why it manifests itself in some elephants and not in others.  
  • The infection most often affects younger elephants ages, who are between weaning from their mother and fully developing their own adult immunities.  

  • While Asian elephants appear more susceptible to the virus and more have been diagnosed with EEHV, both African and Asian elephants have battled, and many have ultimately died from, this disease.  

  • EEHV does not discriminate between elephants living in zoos and elephants in the wild. Whether it’s a calf at a zoo or the young animals in a wild herd, EEHV can strike without an evident cause or reason.  
  • When an elephant is experiencing an active EEHV case, its symptoms may include lethargy and unwillingness to eat, a rapid heartbeat, decreased white blood cell and platelet count, and edema. The virus can quickly cause life-threatening bleeding in the animal.  
  • In its most severe form, the virus can cause hemorrhaging / bleeding that can be fatal within hours of the first signs of illness.  
  • When EEHV is confirmed by a blood test, the elephant is treated with large doses of antiviral medications, blood and plasma transfusions, and other supportive therapies. 

  • The treatment goal is to help the elephant fight the virus, which can cause life-threatening bleeding internally.  
  • Most elephants are able to fight the virus and survive when it comes out of latency. 

  • Elephants showing symptoms can potentially recover if diagnosed and treated early in course of the virus.  

  • Calves are most susceptible after they have been weaned and are no longer protected by their mother’s antibodies.  
  • There is currently no vaccine for EEHV, and it is not preventable.  

  • However, the treatment protocols continue to improve, and detection and treatment recommendations continue to evolve. 

  • It’s important to know there are a lot of talented and committed people working on the challenge. Zoos are helping fund and participate in scientific research focused on finding a vaccine to protect elephants against EEHV.  

About Ajabu’s Most Recent EEHV Case

  • While he was showing no clinical or physical symptoms, standard blood tests we conduct weekly revealed a slightly elevated EEHV viral load on Thursday, April 27.  

  • The team immediately began proactive treatment to try to stem the progression of the virus, which included around-the-clock monitoring and care by our veterinary and animal care teams.  

  • Ajabu’s blood indicators and symptoms progressed through the first week of May.  

  • We had hoped to see his viral load and symptoms plateau and begin diminishing as of Day 7, which was the pattern the virus produced in him when he fought EEHV in March 2021. 

  • Unfortunately, this was not the case. Concerning symptoms, high viral loads, and low platelet counts persisted through Day 12, until he passed away on the evening of Monday, May 8.
     
  • We know Ajabu was afflicted by a different strain of the virus in 2023 (EEHV-2, as compared to his bout with EEHV-3 in 2021), and while we can’t be certain, it seems likely that this strain was the reason for different symptoms and presentation.   
  • In the days leading up to Ajabu’s positive EEHV blood test, he was behaving completely normally. There were no outward signs or symptoms that he had an active case of EEHV.  

  • As the virus ran its course, he developed some lethargy, and his appetite went up and down from day to day.  

  • He did begin to show signs of edema (swelling caused by fluid build-up) in his legs by Day 5. That progressed to his belly, chest, and chin by Day 10.  

  • The most concerning indicators were his high viral load, the drop in white blood cell and platelet counts, and the emergence of edema, as the illness continued.  
  • After the blood tests indicated we might be dealing with EEHV, the team began an aggressive treatment plan.  

  • The team was onsite for round-the-clock monitoring and treatment, which included administering antiviral and antibiotic medications, fluids to prevent dehydration, immune stimulants, anti-inflammatories, and transfusions of fortified whole blood, plasma, and stem cells.  

  • We found ways to try to encourage movement in his legs to help improve circulation and try to reduce the edema.  
  • Scientists and veterinarians widely believe that most Asian and African elephants both in zoos and in the wild have been exposed to and carry EEHV. But it is not known why the virus becomes suddenly active from its dormant phase, and we do not know what caused the virus to suddenly become active in Ajabu. 
  • We have continued to monitor behavior, as well as test blood samples from other elephants within our herd as we would normally – no other elephants are showing signs or have tested positive for EEHV since Ajabu’s positive case. 
  • Just as with the rest of the herd, we are monitoring Okubili 24/7 for ANY signs of a change in behavior that might be consistent with EEHV symptoms.  

  • With Okubili still being so young – and not yet having weaned off mom Mlilo’s milk – scientific research would tell us he is still benefiting from the immunity and antibodies passed along to him through mom’s milk.  

  • Beyond that – since Ajabu’s diagnosis, he has been separated from most of the herd; and even prior to that, Okubili had not yet been introduced to Ajabu. The risk to Okubili is low.  
  • At seven years old, Ajabu is the one individual in our herd who sits squarely in the most at-risk age range for developing an active case of EEHV.  
  • There are several different strains of EEHV; there is no evidence of cross protection between strains. 
  • We are so thankful for the advice, feedback, and actual staffing support, as well as the shipments of blood, plasma, and stem cells that have come from across AZA institutions to help support Ajabu’s EEHV case and treatment.  

  • We’ve received support from Birmingham Zoo, Caldwell Zoo, Denver Zoo, Disney’s Animal Kingdom, Fort Worth Zoo, Houston Zoo, Indianapolis Zoo, San Diego Zoo, Sedgwick County Zoo, and Toledo Zoo; among others who helped through previous research and information sharing. 

EEHV at the Dallas Zoo

  • Ajabu’s current EEHV case is the fifth time since 2021 that our teams have treated a Dallas Zoo elephant for this dangerous viral disease.

  • Unfortunately, this is the second time Ajabu has battled the virus. He became ill with the EEHV-3 in March 2021, and survived following aggressive treatment for the disease.

  • Later in 2021, and once earlier this year, elephants in the herd tested positive for an elevated EEHV viral load and were treated, but none ever showed significant symptoms of the virus.
  • Dallas Zoo’s veterinary and animal care team do ongoing behavioral training to establish trust with the elephant herd so the animals will voluntarily participate in their own care. This makes it possible for staff to watch for signs of EEHV and regularly draw blood for routine testing.  

  • We draw blood regularly, and as often as twice weekly for animals considered more susceptible, and then send blood samples to the National Elephant Herpesvirus Laboratory at the Smithsonian’s National Zoo in Washington, D.C. for ongoing testing.  

  • Dallas is part of a multi-institutional research effort that has been underway for more than a decade to study the virus, identify the various strains, learn about transmission, develop and improve treatments, and create a vaccine.  
  • There is not enough research to confirm how EEHV is transmitted, but most viruses are normally spread from one individual to another. Viral shedding occurs when the virus comes out of latency (hiding); however, there is no simple way to detect if the virus is active without a blood test. What we do know is that every elephant – in the wild and in human care – probably carries one or more forms of herpesvirus. (Source: Smithsonian’s National Zoo & Conservation Biology Institute) 
  • For all elephants, having a herpesvirus is the norm, not the exception.

     

  • Like all mammals and humans, elephants carry a variety of different herpesviruses throughout their lives, and the majority of them may never cause illness, likely remaining latent (hidden). Some cause mild disease, while others cause severe illness or death.

     

  • Claims that zoos become “contaminated” once an animal becomes ill from EEHV are unfounded and based on a lack of understanding of how the viruses live within their hosts. Like many viruses, herpesviruses cannot live very long outside the body, so an EEHV outbreak in one individual does not “contaminate” a facility. (Source: Smithsonian’s National Zoo & Conservation Biology Institute) 
  • Humans and other animal species cannot contract or transmit the virus.