Excalibur, the Spanish dog infected with Ebola, before he was euthanized by Spanish authorities for fear of contaminating humans. Reuters/Susana Vera

A visual guide to the nasties possibly lurking inside your best friend.

Spanish authorities made the decision to euthanize and incinerate poor Excalibur the dog this week, after his owner, nurse Teresa Romero Ramos, contracted Ebola while treating repatriated Spanish missionaries. The reaction throughout world the one has been one of outrage tinged by panic. Did Excalibur have Ebola? Is it even possible for a dog to contract Ebola? Can my dog give Ebola to me?

There is one article in the medical literature that draws a link between Ebola and dogs, CDC Director Thomas Frieden pointed out Tuesday. “Whether that was an accurate test and whether that was a relevant test, we don't know, but we want to look at all possibilities,” he said.

I spent some time speaking to veterinary and infectious disease experts, and they all agree: If you live in America, even in a densely populated American city, do not toss Fido to the curb yet. As my colleague Tanvi Misra explained last week, Ebola isn’t all that contagious; given the advanced state of American public health, it’s even less so here. So your dog (and you) probably won’t get Ebola in the first place.

However, your dog really could make you sick. Researchers estimate that there are roughly 4 million pet-derived human infections in the U.S. per year, costing the public upwards of $300 million in medical expenses. In fact, most human infectious diseases began as zoonotic diseases, or diseases that can be passed between animals and people. But don’t panic: “For the general public, there are not many diseases that we need to worry about,” says Polina Vishkautsan, an internal medicine specialist at the UC Davis School of Veterinary Medicine. "Good hygiene prevents common diseases, and that will prevent anything else that comes," says Peter Rabinowitz, an occupational and environmental medicine expert at the University of Washington’s School of Public Health.

But here, according to the CDC and for your edification, are the five most common parasites and diseases that you can get from your dog—and how to prevent them:

Camplylobacteriosis

(Pooley De Wood, USDA, ARS, EMU/Wikimedia Commons)

What is it?
Camplybacteriosis is caused by the Campylobacter bacteria, the little bugger above. The only bacterial infection on this list, scientists estimate that it causes more than 200,000 cases of gastroenteritis in humans per year. Campylobacter can be found in the guts of even healthy dogs, though it most often affects puppies. Doggies shed the bacteria through their feces; we get it through what’s delicately called “fecal-oral contact.” Basically, by accidentally eating trace amounts of dog poop.

What will it do to me?
Camplybacteriosis will cause your stomach and intestines to become irritated and inflamed, which leads to diarrhea and fever.

How do I prevent it?
Wash your hands with soap after contact with pet feces, you filthy human. Additionally—and this goes for all parasitic diseases on this list, as well—use deworming products on your pup regularly. Most vets recommend that adult dogs be dewormed twice a year.

Dog tapeworm

(CDC's Division of Parasitic Diseases (DPD)/Wikimedia Commons)

What is it?
There are actually—and I’m sorry to tell you this—a number of different types of parasitic tapeworms possibly inside your dog, but we’re going to focus on Dipylidium caninum, one that infects animals through contact with fleas or lice. The worm is transmitted when animals and humans accidentally ingest their flea hosts. Among humans, the dog tapeworm is mostly commonly found in children.

What will it do to me?
Human Dipylidium caninum infections are not that bad. In the worst and most isolated cases, infection can lead to abdominal pain, diarrhea, irritability, and “anal pruritus," which sounds horrific but is just an itchy butt. In humans, dog tapeworms can be detected by finding, in the words of the CDC, “rice-like segments of the tapeworm crawling near the anus or in fresh bowel movements.” To which I say, “Please, god, no.”

How do I prevent it?
Prevent your dog from getting fleas in the first place by using flea-control products, which come in the form of collars, topical treatments, and doggy pills.

Hookworm

I apologize for this one. It's cutaneous larva migrans, caused by hookworm infection. (WeisSagung/Wikimedia Commons)

What is it?
Hookworm is a parasitic nematode that lives in its host's small intestines. They move from dogs to humans (again) through fecal matter. Puppies can also get hookworm from their mothers’ milk. But hookworms, unlike tapeworms, get in through the skin. Once larvae enter your skin, they travel through the bloodstream and into the lungs or small intestine.

What will it do to me?
Hookworms can’t reproduce inside humans, but they are pretty nasty. A papule generally forms where the larvae enters the skin, soon followed by red, wavy rashes and itching. The symptoms are worst at night.

How do I prevent it?
Avoid walking barefoot on beaches or in parks—or anywhere in your community where dogs generally defecate.

Rabies

Rabies patient in 1959. (Wikimedia Commons)

What is it?
Rabies is the only viral disease on this list; it causes inflammation of the brain in affected humans or animals. The good news is that incidences of dog-to-human rabies transmission are very rare because of vaccination procedures. Dogs are vaccinated against rabies when they’re puppies, and then again every one to three years. In the U.S., humans unlucky enough to get rabies are generally infected by wild animals. Transmission between animals, and then between animals and humans, happens through bites or scratches.

What will it do to me?
Oh, this one is bad. The period between rabies infection and the first flulike symptoms of the infection can last up to 12 weeks, but once those symptoms hit, rabies is almost always fatal. Inflammation of the brain can cause paralysis, confusion, agitation, paranoia, hallucinations, and delirium—then death. Scary stuff.

How do I prevent it?
Get your dog vaccinated! And then vaccinated again! Additionally, avoid strange dogs (or any animals, for that matter) that are behaving erratically. If you have been bitten by an animal, see a doctor for treatment immediately, before symptoms appear.

Toxocara Roundworm

(Flukeman/Wikimedia Commons)

What is it?
Toxocara roundworms are yet another kind of parasite. Both dogs and people become infected by swallowing roundworm eggs. Additionally, roundworms can be transmitted during gestation or through a mommy dog’s milk, so puppies are especially susceptible.

What will it do to me?
Children are most often affected by roundworms, and most human infections are asymptomatic. Rarely, the parasite migrates to the liver or lungs or, in even rarer cases, to the eyes. Visceral larva migrans, the liver and lung kind, affects an estimated 10,000 Americans per year; in the very worst cases, the parasites will cause organ inflammation and damage. Ocular larva migrans, in the eyes, affects only 700 Americans per year. In these cases, the roundworms invade the retina, which leads to inflammation, scarring, and—very, very rarely—blindness. Let the nightmares begin.

How do I prevent it?
Wash your hands after dealing with feces, and make sure it’s disposed of in the trash. And use deworming products.

***

Here are two pieces of good news: The first is that most of these diseases, even if you contract them, are not serious. The second is that human and animal doctors are increasingly working together to prevent the transmission of infections from pets to pet owners. If, heaven forbid, your Rover becomes the next Excalibur—or even the next victim of dog tapeworm—scientists say the American medical community is becoming increasingly more prepared to deal with any transmission issues. According to Rabinowitz, some doctors are using what's called a "One Health" approach, considering the health of humans, animals and the environment when addressing human medical problems. In short: a happy, healthy dog makes a happy, healthy human.

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