African Horse Sickness
What reptile keepers in the US need to know
It’s been a while since I last posted an entry in this blog. Recently, though, I’ve received several requests for assistance related to a problem I have not covered before: African Horse Sickness. The requests are coming from zoo personnel and private collectors of venomous snakes, in various places in North America.
What is African Horse Sickness?
African Horse Sickness, or AHS, is a disease that can cause serious illness or death, in horses. It does not infect people. It is caused by a virus and it is carried by insects. AHS has been known in Africa for many years, where zebras and a few related animals can carry it in nature. Epidemics of AHS have occasionally led to horrible problems for horses, not only from the disease itself but also from slaughter campaigns that were deemed necessary in order to eradicate it. So far, we have not had any AHS in the Americas, though, and with the controls that are currently in place it is unlikely to become a problem here any time soon.
You can read more about it in this article, written by a USDA veterinarian for the Merck Veterinary Manual.
According to the US Department of Agriculture (USDA), the regions of the world that are currently affected include the entire continent of Africa with the exception of Morocco, plus Oman and Yemen. The applicable part of the US Code of Federal Regulations is accessible here.
Why does AHS matter to scientists and reptile keepers in North America?
It matters because antivenom – the only specific treatment for potentially deadly snakebites -- is made using the blood serum of immunized horses. No matter how well they follow their safety protocols, scientists, lab workers, zoo personnel and private collectors sometimes get bitten by snakes. When the snake is a mamba or cobra or viper from Africa, we count on the availability of antivenom made using African snake venom, for the preservation of life and limb. And – here is where things get tricky – antivenom made in horses in Africa is causing our import authorities to worry that bringing it into the country could put American horses at risk.
If you are lucky enough to live in Mexico, then this next part does not apply to you, because Mexico is one of the only places in the world where antivenom that works against African snakes is manufactured. Mexican horses have never suffered from AHS. Let’s hope they never do.
If you live in the US or Canada, however, then you should know that several types of snake from Africa are on the “top ten list” of exotic snakebites in the USA.
We have plenty of antivenom in the US for bites by our native rattlesnakes and copperheads – that is not the problem. There has never in history been antivenom approved for commercial sale in the USA, however, that works against the venom of African snakes. For this reason, keepers of venomous snakes are on their own in a way that few other people can understand: they must get government permission to import these lifesaving antidotes from manufacturers around the world, regardless of whether those manufacturers care to send dossiers to the FDA.
I have been hearing about this problem because I am the physician responsible for the Antivenom Index, in support of the Association of Zoos and Aquariums and the American Association of Poison Control Centers. The index is not available for public view, for security reasons. It also should not be considered comprehensive, because there are some other organizations that import antivenom. But I took a look at the Index today, and I found that the #1 foreign antivenom product used here, BY FAR, is one that comes to us from South Africa. My data indicate that of all of the antivenom for African snakes held by AZA member organizations, 90% is manufactured in a country that worries the USDA. (The other 10% is mostly from Inosan Biopharma or from Instituto Bioclon.)
To be clear: I have been providing consultations on this subject for three decades. I am unaware of any report, ever, of AHS affecting the herds of horses that are used to make antivenom in Africa. Even if there was a problem and we did not know about it, the virus should not infect humans. There is no reason for American horses to get injected with African antivenom, because all of the snakes that American horses encounter are our own native animals. In all my career, I have never heard of an animal in the USA that needed to receive African antivenom, not even once. Bottom line: practically speaking, the risk that antivenom from South Africa will bring AHS to America’s horses is approximately zero.
At the same time, there is a terrible worldwide shortage of antivenom going on, which is particularly difficult for the people of Africa. US reptile keepers are lucky if they can find antivenom at all.
Reptile keepers and their doctors need practical solutions that will ensure that both humans and horses are safe. And we need antivenom.
What can a person or organization that keeps venomous African snakes do about this?
First: if you do not already have venomous African snakes in your collection, now is not the time to acquire them. If you have snakes but no antivenom at all, then this might be the time to find them a different home. Think about it, seriously.
Second: do not discard any African antivenom that you already have. Sometimes, expired antivenom can be used even years after it was manufactured. Consult a US expert in toxinology, if you need specific guidance on this.
Third: learn about the availability of products that are not made in South Africa, and look at what has been published on the safety and specificity of antivenom against the particular species in your collection. Many zoos in the USA have begun relying on products from Inosan and Bioclon, for example. If these work for you, and if you can get your hands on them despite the worldwide shortage, then congratulations.
Four: get involved with advocates who have recently opened discussions with APHIS. We need one of two things: either a straightforward way to prove that imported products do not carry the virus, or a system that will to guarantee to USDA that African antivenom will never find its way into US horses.
Finally: never buy antivenom except either from the manufacturer or from a licensed distributor affiliated with the manufacturer. Black market antivenom can be dangerous, expensive and ineffective, worse than none at all. The FDA’s information page on use of unlicensed antivenom can be found here.
I'm a medical toxinologist, writing to make my field less scary and more understandable to people everywhere.