Iceland, Horses, and Hendra: Greg thinks about infectious disease when he’s supposed to be on vacation

By Greg Mercer

I recently visited Iceland, which in addition to being naturally beautiful and having weird day/night cycles thanks to its latitude, is something of an ecological paradise with an excellent renewable energy record. I was surprised to learn about their horses and the restrictions placed upon them, partially for the prevention of disease.

The Icelandic horse is notable for being fairly small (pony-sized, but don’t call it a pony), adaptable, hardy, and having 5 types of gaits, a detail which is basically meaningless to me but is apparently of great significance to horse dressage enthusiasts. My companions and I stopped at a stable, where one of the breeders told us about the breed, its history, and its unique international commerce status. I haven’t met too many horses but these ones seemed pretty nice.

Icelandic horses are popular around the world, and are frequently exported to foreign buyers for work or show. Imports of horses to Iceland, however, are banned. Once they leave, they can’t go back home, and horses born outside the country aren’t allowed in. Allegedly, this has been the case for about a thousand years. It’s hard to pin down a start date for that, but the policy is in effect today. There are two reasons for this: Icelandic horses are prized for being purebred and having a heritage that dates back to Viking settlers. They’re the only breed of horse in Iceland, so maintaining these traits is easy. Presumably the 80,000 horses in the country are enough to avoid a population bottleneck (I must reiterate that I am no horse expert).

But the import ban also guards against disease. Iceland has few natural horse diseases, and the breeder I spoke to said that Icelandic horses are frequently unvaccinated, which would be very unusual in the rest of the world. When they’re exported, they have to be treated as if they don’t have any immune protection. The import ban prevents foreign diseases from entering the country (via other horses, anyway).

Horse vaccines are big business. Throughout the rest of the world, horse owners can vaccinate their horses against West Nile Virus, Influenza, Potomac Horse Fever, Rabies, and other diseases. It makes a lot of sense: horses represent a major investment. For a horse owner, the cost of vaccination could be a fraction of the financial loss from a fatal horse disease. Plus, people tend to like their horses, and want to keep them from getting sick.

Even if you aren’t a horse dressage enthusiast or otherwise equine-inclined, horse diseases are no joke. Consider Hendra virus: Named for the suburb of Brisbane, Australia, where it was first isolated, Hendra is a Henipavirus, in the same family as Nipah virus. It’s found in Australia, Southeast Asia, India, and Madagascar. It can be transmitted from horses to humans via exposure to a horse’s bodily fluids, tissues, or excretions, and can prove fatal in both humans and horses. It’s likely that horses are exposed to the virus from the urine of flying foxes, a type of large bat. The details of the fatal Brisbane outbreak are detailed in David Quammen’s excellent book, Spillover.

This is all to say that Icelandic horses have a unique situation. As long as no new equine diseases enter the country, it’s more or less a closed system. The Icelandic Food and Veterinary Authority takes this equilibrium very seriously, offering warnings about foreign disease and guidelines for preventing infection.

Pandora Report 4.11.15

It’s a public health weekend here at Pandora Report as we check out stories on TB and Polio. We also have other stories you may have missed.

Have a great week and see you back here next weekend!

Ancient Hungarian Crypt Offers Clues to Tuberculosis Origins

As one of the leading infectious disease killers, Tuberculosis, a bacterial infection, holds interest for scientists who disagree over the origins of the human disease. However, a new study in Nature Communications uses a cutting-edge approach called metagenomics to analyze corpses that were naturally mummified in a Hungarian crypt. Of 14 genomes found in eight of the corpses, researchers discovered that multiple strains were circulating in Hungary in the 18th century when these people died.

The Toronto Star—“‘All the historic genomes belonged to lineages that we see today,” said senior author Dr. Mark Pallen, a professor of microbial genomics at the University of Warwick. “So TB hasn’t changed much in 200 years … (and) it turns out that the most common ancestor of the Euro-American lineage that all our (tuberculosis) genomes belonged to dates back to late Roman times.’”

Polio, Cancer—One Nemesis May Counter the Other

Tomorrow, April 12, is the 60th anniversary of when Dr. Jonas Salk’s polio vaccine was declared to be effective. Today, as the world inches closer to full polio eradication, interesting news highlighted on “60 Minutes” looks at the polio virus’ ability to kill another lethal illness—Cancer. A genetically engineered strain of polio virus appears to thwart lethal brain cancer tumors.

The Huffington Post—“The modified polio virus seems to deactivate the cancer tumor’s ability to defeat immune capacities. Freed up, the immune system works at defeating the tumor. Miraculously, the immunotherapy workings spare healthy tissues, while killing cancer cells.”

Stories You May Have Missed

Image Credit: Pudelek

Hendra Virus: Vaccines Available but Underused

By Chris Healey

Horse owners in Australia are reluctant to vaccinate their horses against an emerging viral illness capable of sickening humans.

Hendra virus, an emerging infectious disease of horses and humans, has been responsible for the death of 4 people and dozens of horses in Australia since its discovery during a 1994 outbreak of an acute respiratory illness among horses and stable workers in Queensland, Australia. Laboratory tests performed during that outbreak confirmed horses and humans became sick from identical viral agents.

An epidemiologic investigation revealed flying foxes of the Pteropus genus act as Hendra virus reservoirs. Health officials have hypothesized that horses contract the illness through inadvertent consumption of infected bat urine. Hendra virus spreads to humans who come into contact with body fluids, tissues, or excretions of infected horses. Those who work closely with horses, such as equine veterinarians and stable hands, are most at risk of Hendra virus infection.

Early on, researchers discovered Hendra virus glycoproteins could be exploited as an immunization strategy. Following a human Hendra virus death in 2009, and an exposure in 2010, a vaccine for horses was released in 2012 by Zoetis, Inc. As an animal vaccine, developers were spared arduous human pharmaceutical testing protocols and quickly released the product.

The vaccine, called Equivax HeV, is unprecedented in preventative medicine. Not only is it the first vaccine licensed and commercially available to prevent illness from a BSL-4 agent, a pathogen requiring the highest laboratory safety protocols, but it is also the first veterinary vaccine used to transitively prevent illness in humans.

Similar to how smallpox and measles vaccination prevents spread of their respective illnesses, Hendra-vaccinated horses are less likely to transmit Hendra virus to humans by reducing viral shedding. Equivax HeV provides Hendra protection for the horse and the people who interact with it.

Despite vaccine advantages, horse owners say they cannot afford it. A single administration can cost upwards of $200, and booster administration is needed every 6 months for the life of the horse to maintain immunity. Many are unwilling to pay. As a result, only 11% of horses in Australia are estimated to have received the vaccine.

Health authorities are working to approve guidelines recommending yearly booster administrations, cutting immunity maintenance costs in half.  Veterinarians say more horse owners will choose to vaccinate as attitudes toward occupational safety change. Greater awareness of the danger posed to equine veterinarians and stable hands working with unvaccinated horses is expected to place a stigma on non-vaccinating establishments.


(Image Credit: Fainmen)