By Dr. Becker
From measles, bird flu, to Ebola, we're constantly being inundated with news about the latest disease outbreaks facing humans. Much less talked about are outbreaks facing animals, but this doesn't mean they don't happen.
In fact, animal outbreaks occur with some regularity, just as they do in people. The World Health Organization (WHO) actually maintains an early warning system for major animal diseases, including zoonoses, which are diseases that can be transmitted from animals to people (and vice versa).1
The US Centers for Disease Control and Prevention (CDC) also maintains a database of zoonotic disease outbreaks, but these have mainly involved salmonella infections transmitted from live poultry, reptiles or, in one case, frozen feeder rodents.2
This spring, the CDC has even been reporting on a canine influenza (dog flu) outbreak in the Chicago area (canine influenza A H3N2 virus), which has sickened more than 1,000 dogs. In this case, the virus does not pose a risk to humans but is highly contagious among dogs, prompting warnings for pet owners to avoid dog parks, groomers, group training facilities, and doggy daycares.3,4
Animal diseases are certainly not confined to house pets, however. TIME recently featured eight diseases that are plaguing animals worldwide, some of which are threatening the very survival of the species.5
Eight Plagues of the Animal Kingdom
1. White-Nose Syndrome – Bats
The fungus Pseudogymnoascus destructans can infect the muzzles, wings, and ears of hibernating bats, causing the incredibly deadly white-nose syndrome. It first appeared in New York in 2006 and has to date killed 6.7 million bats across the US and Canada. Although the disease originated in Europe, the bats there seem to be immune to the condition.
It's thought that the fungus is spread from bat to bat, although they may also pick up the spores from contaminated caves (possibly contaminated by fungal spores brought in by human cave explorers). The fungus kills 70 to 90 percent of bats infected within a hibernating group.
2. Canine Distemper Virus – Tigers and Canines
Canine distemper virus (CDV) is spread through respiration but attacks the nervous system and gastrointestinal tract. Many people have heard of canine distemper in dogs but are not aware that it can infect big cats like tigers too. In one five-year period, one group of tigers in Russia declined from 38 tigers to nine, and CDV is thought to be the culprit.
3. Starfish Wasting Disease – Starfish
Starfish wasting disease causes a starfish's limbs to curl and fall off, then eventually causes tissue decay and death. As Live Science reported:6
"By the time the disease has run its course, there's nothing left of the infected animal but a gooey lump of decomposing flesh."
While it was originally thought the disease might be due to pollution or changing ocean temperatures, a recent study found the culprit may be a waterborne virus called densovirus.7
4. Brucellosis – Bison, Cow, and Elk
Brucellosis is a venereal disease caused by bacteria that invade the reproductive organs. It occurs in a variety of different animals (including dogs) through infection with several species of Brucella bacteria, leading to a variety of symptoms, including inflamed joints and reproductive problems.
In humans, infection can occur when a person comes into contact with an animal or animal product infected with the Brucella bacteria. The disease has been largely eliminated from US cattle but still circulates among bison and elk living in Yellowstone National Park.
There is some concern that wild animals could transmit the disease to nearby livestock, as has occurred in about 17 instances from 2002 to 2012.8 Unfortunately, Yellowstone park officials are planning to cull 900 bison in an attempt to curb the spread of brucellosis in the area this year.
5. Colony Collapse Disorder – Honeybees
Since 2006, US beekeepers have lost a stunning 29.6 percent of their honeybee colonies annually due to a disease dubbed colony collapse disorder (CCD).
The condition causes bees to become disoriented, leaving their hives and never returning. Hives across the country have been decimated, and while there's still no definitive cause, pesticides, viruses, mites, fungi, and antibiotics may play a role.
The widespread use of neonicotinoids, a class of insecticides, appears to be particularly damaging to bees, and last year a Harvard study concluded, "Neonicotinoids are highly likely to be responsible for triggering CCD" in previously healthy honeybee hives.
It's also been suggested that CCD may weaken bees' immunity, leaving them vulnerable to other infections or parasites.
6. Rabies – Bats, Monkeys, Dogs, Raccoons, Foxes, and More
Rabies is a virus transmitted through saliva. The virus travels to the brain, where it interferes with the animal's ability to regulate heartbeat, breathing, and salivation.
Once a disease of domestic animals, rabies is now primarily found in wildlife (although it can be contracted by any mammal, including humans).
About 90 percent of rabies in animals occurs in wildlife. Most cases of human rabies transmission in the US have occurred from bats, while raccoons and skunks are the animals most likely to be infected.
To curb its spread, some states drop rabies "vaccine packets" into wildlife areas. The vaccine packets resemble ketchup packets and are smeared with stinky fishmeal, which appeals to raccoons. The plastic packets squirt rabies vaccine into raccoons' (and other animals') mouths when they bite down on them.
7. Chytridiomycosis – Frogs
This fungal disease, caused by the chytrid fungus Batrachochytrium dendrobatidis, infects a frog's outer layer of skin, which is important for respiration. The fungus causes the skin to thicken, which interferes with the frog's ability to absorb water through its skin and eventually leads to cardiac arrest and death.
About 200 amphibian species have dwindled or gone extinct due to this condition. Researchers have attempted to stave off the fungus using anti-fungal treatments and warm-water incubation for tadpoles, but it is still prevalent in the wild.
8. Cattle Fever – Cows and Deer
Parasites transmitted by ticks can cause cattle fever, a wasting disease in cattle that is sometimes deadly within days. According to TIME:9
"The US government employs a cadre of cowboys to ride the banks of the Rio Grande in order to stop the spread of ticks that cause cattle fever…
A nationwide tick eradication program has largely pushed cattle fever out of US borders, but the 'tick rider' cowboys still patrol the borders to catch any stray Mexican cattle—often abandoned by ranchers fleeing drug war violence—that might spark an outbreak."
Many Pet Diseases May Stem from the Gut
Interestingly, just as research is showing that the human microbiome is essential for preventing disease, the collection of microorganisms in your pet also plays a large role in his overall health.
Research by Kelly Swanson, PhD, a nutritionist at the University of Illinois, for instance, suggests many of the conditions often seen in pets, such as oral disease, gastrointestinal (GI) disease, inflammatory bowel disease (IBD), skin and urinary tract diseases, and bacterial infections, are all linked to changes in the microbiome.
If you'd like to lower your pet's risk of zoonotic and chronic diseases, one of the best approaches may be to nurture your pet's microbiota, which you can do much like you may do to yourself – by focusing on healthy species-appropriate foods, beneficial bacteria, and avoiding antibiotics unless absolutely necessary.