Glanders, a very serious disease of horses, donkeys and mules caused by infection with the bacterium Burkholderia mallei, has made the news again in a rather unusual manner – it has been reported as the cause of an outbreak in lions and a tiger at an Iranian zoo in Tehran.
The story goes that two Amur tigers arrived at the Tehran zoo from Eastern Russia in April 2010 as part of an exchange program between the two countries. The tigers were supposed to be used to help restore the tiger population in northern Iran on the Miankaleh nature reserve, but their living quarters there were apparently still not ready, and thus they were being kept at the zoo. One of the tigers died in December 2010.
And that’s were the story starts to get a little dicey. The Iranians claim the tigers were imported already carrying the disease, and that the last case of glanders at the zoo was 50 years ago. The tigers had already been at the zoo for eight months – although the incubation period for glanders can be months in some cases, it is normally only weeks. The Russians of course insist that the tigers were completely healthy when they were transferred – they’d been thoroughly examined and quarantined prior to being moved. (This makes the most sense to me, since transporting an animal such a long distance is a major stress and increases the risk of illness, and transporting an animal that is already sick would be even more risky. Not a chance I would take with two members of a species of which there are fewer than 900 individuals left in the world.) They also pointed out that a sick tiger from the cold regions of Russia would be much more likely to succumb to illness during the very hot Iranian summer, not during the winter.
Another report said that three lions at the zoo also died from glanders in the last two months, and subsequently another 14 lions were diagnosed with the disease, all of which were put down by the authorities. The main concern seemed to be the spread of the disease from the big cats to the feral cat population, and then to the human population. This second report states that “the tiger died after being fed contaminated meat, though it is possible it could also be related to the glanders.” Yet another report said that the tiger was infected with feline immunodeficiency virus (FIV – the feline equivalent of HIV).
Facts to keep in mind:
- Glanders is an highly contagious disease, and highly fatal (B. mallei is even classified as a Class B bioterrorism agent).
- Animals that do recover from the disease can become long-term carriers of B. mallei, and are a risk to other animals (and people). Prompt euthanasia of affected animals is therefore often the primary means of controlling outbreaks (but the bacterium is susceptible to antibiotics).
- The infection can be transmitted to other animals (and people), usually through close direct contact or contact with oral and nasal secretions and discharge from skin ulcers. It can also be transmitted by eating tissues from infected animals.
- The bacterium is killed by most disinfectants, and UV radiation (sunlight).
Glanders can affect species other than equids, including people and cats, however there is very little information available about glanders in any felids, let alone lions and tigers. Theoretically it might be possible for the disease to spread from the zoo animals to feral cats and then to people, but I don’t know how many feral cats are brave (or stupid) enough to wander into a lion enclosure. There’s also a possibility that a glanders-positive feral cat may have infected the zoo cats (but again, it would have to be very brave, or very stupid). It is also unclear what tests were used to confirm that the big cats were infected with glanders, and it is unknown if other animals at the zoo have been tested. Since this is typically a disease of equids (and has also been found in goats and camels), I would certainly be checking these animals first.
The big question is, where did the glanders come from in the first place? It seems unlikely that the tigers brought it from Russia, when the disease is actually endemic in Iran (even though they’d had no diagnosed cases at the zoo for many years). Is there a carrier animal in the zoo? Were the animals infected by eating contaminated meat? Was it brought in by feral cats? The source needs to be identified and addressed or animals will continue to be infected, which is particularly bad news for the kinds of rare species that may be found in a zoological collection. Some more details about the testing would also be appreciated – given the severity of this disease, and the severity of the consequences for positive animals (euthanasia), one needs to be as sure as possible that these animals are infected with B. mallei and not something else.
Photo: Amur Tiger (Panthera tigris ssp. altaica) (click image for source)