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'We have been working hard, but we have also been lucky'

Elephant calf Sanuk cured of viral infection.

When zookeepers examined two-year-old elephant calf Sanuk last November, they discovered that her tongue was unusually red. This symptom might point to elephant endotheliotropic herpesvirus (EEHV), an infection that could be fatal to young elephants. As the zoo immediately went on red alert, its teamwork, rapid intervention, and cooperation with national and international experts gave Sanuk the chance to overcome this infection.

Thursday 8 November, 8:45 a.m. – Inspection of Sanuk's tongue


Sanuk’s tongue

Examination of Sanuk's tongue

ARTIS has been especially watchful for possible symptoms of an EEHV infection since 2015, when Mumba the elephant suddenly died. Consequently, the elephant keepers perform daily examinations of Sanuk's tongue. One of the keepers notices its abnormally red colour on 8 November, resembling minor bleeding. The zoo immediately goes on red alert. ARTIS veterinarian Martine van Zijll Langhout pays a prompt visit, which confirms that the haemorrhages on Sanuk's tongue can be a sign of the lethal EEHV. However, Sanuk does not display unusual behaviour, as her activity levels and appetite appear healthy. Martine: 'We made great efforts over the past years to create a treatment protocol so that we know what we should do in case of an infection with EEHV. The chances of survival improve significantly with rapid and targeted intervention. While we are unfortunately unable to prevent EEHV infections, we try our absolute best to avoid losing a young elephant.'

In the wild and in zoos

Asian elephants fall prone to EEHV both in the wild and in zoos. Elephants around the globe are victims of this disease; especially calves. So far, the chances of recovery have been slim: of all infected elephants, 80% die within a matter of days. Martine: 'Calves who start eating solid food miss out on most of the antibodies obtained by drinking their mother's milk. The result is that young elephants become more vulnerable to EEHV infections from the age of two, although we still do not know the reason for the sudden illness in elephants due to this virus.'

9:00 a.m. – Antiviral medication  

Immediate start of treatment

Treatment starts immediately by having Sanuk take antiviral drugs. Although she dislikes the taste, Sanuk swallows most of the 30 pills. These pills come from the emergency supply at ARTIS. Long-term treatment would require a much bigger supply though, so when subsequent research indeed identifies the infamous virus, Martine calls several pharmacies straight away in hopes of collecting the whole lot of pills. Martine: 'Some pharmacists did raise their eyebrows when I placed my rather large order. They were very understanding, however, when I told them that the recipient was a one-tonne elephant.'

10:00 a.m. – Call to Belgian zoo Pairi Daiza

Blood plasma from donor elephants in Belgium

Another key component of EEHV treatment is administering thrombocytes, coagulation factors and antibodies through transfusion of blood plasma from healthy elephant adults. To this end, the veterinary team quickly calls their colleagues at Pairi Daiza zoo in Belgium, which houses a large herd of Asian elephants.

Meeting halfway

Its elephant keepers tap no fewer than seven bags of blood from three elephants and transport these bags to the Netherlands as quickly as possible. Meanwhile, an ARTIS employee drives towards the Belgian transport, collects the blood bags from them halfway and returns to ARTIS post-haste. Martine: 'It is crucial to perform the plasma treatment. Transfusing blood plasma increases the infected animal's resistance, supplies additional coagulation factors and reduces the risk of internal bleeding.'

11:00 a.m. – Extraction of blood samples

Blood samples need to be taken in order to diagnose Sanuk accurately. Before she is sedated, her mother Thong Tai will be administered a mild anaesthetic. Seeing her mother in a calm state will help to reduce Sanuk's stress at being sedated, which is important. Martine: 'It is best to anaesthetise elephants while they are standing. Even though they're unconscious and desensitised, they do remain upright on their own. This process allows us to perform most actions safely, whereas the huge and heavy animals cannot hurt or harm themselves from an unfortunate fall.'

Taking swabs

Sanuk is only sedated when her mother is fast asleep and it takes about 20 minutes before blood can be tapped. Moisture is also administered to Sanuk, while swabs are taken from her eyes and vulva to see whether these excretions contain the herpesvirus. The veterinarian notes at this time that the vaginal mucosa is haemorrhaged as well, which is another sign of an EEHV infection. Martine: 'The elephants are fortunately subjected to a minimum of stress. It's vital in this respect that the zookeepers and the animals are on good terms. These elephants have visible faith in their keepers, which is beautiful to behold.'

You can boost the immune system, but it is the body that must defeat this virus

2:00 p.m. – Transport of blood samples to laboratories in Amsterdam and England


Bustling activity

Some of the blood samples are sent to a specialised laboratory in Addlestone, England by express delivery. This laboratory is only one of two in Europe that can perform EEHV tests. These tests examine the quantity of viral particles in the blood. Other blood samples undergo a full blood screening in the haematological clinical chemical laboratory of the OLVG hospital in Amsterdam.
The veterinary team at ARTIS also test the blood samples for thrombocytes and cellular inflammation. Martine: 'Through this method, we can monitor the response of Sanuk's immune system and organs to the virus within hours of taking blood samples. We need this information to keep tailoring the treatment plan to her needs.' The English laboratory has found over 2 million EEHV1B viral particles per millimetre of Sanuk's blood. As the quantity of particles is dramatically elevated and the virus can kill quickly, the team decides to continue treatment in accordance with the protocol.

7:00 p.m. – Tests on Belgian donor blood

The blood samples from Belgium reach ARTIS early in the evening. It is now possible for the veterinary team to examine the donor blood and see whether the three Belgian elephants are a proper match for Sanuk. Just as humans, elephants have a variety of blood types, which makes it crucial to conduct a cross-matching test in advance. To everyone's relief, all three elephants prove to be suitable donors.


Friday 9 November, 9:00 a.m. – Production of blood plasma

The next morning, Martine takes the blood bags to the Sanquin blood bank in Amsterdam. The bags with the donor elephants' blood are then churned in a huge centrifuge. This process separates the heavier blood cells from the clear fluid: blood plasma.

Friday 9 to Sunday 11 November – Successful treatment

On Friday, Saturday and Sunday, Sanuk is administered blood plasma transfusions. Each treatment also includes antiviral drugs, moisture and antibiotics. Daily blood samples are taken to monitor the success of the treatment. Martine: 'And it catches on! There's a clear decrease in the number of viral particles on Sunday and Sanuk's tongue is noticeably less red on Monday. The blood also contains more thrombocytes and lots of cellular inflammation. In other words, her immune system is working hard, which bodes well.' The next blood sample, eight days after the initial symptoms, indicates normal values again.


A month later

We are midway through December and Sanuk seems to be in tip-top shape. Her tongue is a healthy pink hue, her appetite has remained and her presence in the herd is vibrant. She also continues to be playful; for example, finding her balance as she walks across the large tree trunk on the floor of the elephants' new outdoor enclosure. 

While Martine breathes a sigh of relief at the happy end, the rest of the elephant keepers and the veterinary team continue to monitor the situation. 'Elephants remain highly susceptible to this sort of virus until the age of eight, whereas Sanuk is only two years old. Furthermore, a variety of virus strains can be found, so chances are that Sanuk will prove vulnerable to the outbreak of another variant.'

To tackle this issue, zoos around the globe maintain close partnerships. ARTIS is one of the participants in a study that aims to solve the mysteries surrounding this virus. In addition, international research meetings on this topic are organised periodically. Martine: 'Since cases such as Sanuk teach us a great deal about the disease, we hope to have an even better cure in future. While we would be euphoric if we found a vaccine which prevents the infection, we unfortunately have not reached that stage yet.'