Pet Connection by Dr. Marty Becker, Kim Campbell Thornton and Mikkel Becker

One-Two Punch Against Heartworm

New approach to preventing infection in dogs may stem tide of resistance

Andrews McMeel Syndication

If you've heard that heartworm, a dangerous parasite that can cause serious disease and death in dogs as well as cats, is becoming resistant to the drugs we've long relied on to protect our pets, you've heard correctly.

"Failure of oral preventive drugs is reported most often from the Mississippi Delta area, where transmission rates are very high and resistance to preventive drugs has been confirmed," said Dr. John McCall, professor emeritus in the department of infectious diseases at the University of Georgia College of Veterinary Medicine. "But the spreading of resistance to other parts of the country is just a matter of time."

The threat of heartworm that can't be prevented with our present drugs is not a minor one. Infection with heartworm, a parasite spread by mosquitos, can cause life-threatening immune system reactions, respiratory distress, kidney failure, heart failure and other symptoms in both cats and dogs. However, there's some good news, too. McCall recently published a study of a new two-step approach to fighting heartworm infection in dogs: one that targets both the heartworm and the mosquito that carries it.

"Heartworm is a two-parasite system," said Dr. Elizabeth Hodgkins, director of veterinary relations for Ceva Animal Health, which makes Vectra 3D, a topical mosquito repellent and insecticide for dogs that also fights fleas and ticks. "Until now, we have not targeted one of these parasites, the mosquito. We've relied on preventive drugs against the worm to do the 'heavy lifting' alone."

This flies in the face of how human public health programs fight mosquito-carried diseases like Zika virus, where the mosquito is always the primary target. Not only that, but putting all your health eggs in one prevention basket will always be less effective than protecting against disease with more than one strategy.

"When you get a flu vaccine, you still take other precautions, don't you?" asked Hodgkins. "You still wash your hands and avoid standing in the air space of someone who's coughing. You know there are other things you need to do to give that vaccine the best chance to keep you from getting sick." It's the same, she said, with heartworm.

When it comes to preventing the spread of resistant heartworm outside the South, or protecting dogs in areas where resistance is already present, targeting the mosquito is a valuable extra layer of prevention.

Resistance is thwarted because the topical medication stops more than 95% of mosquitos from biting protected dogs. As a result, the dog has a greatly reduced risk of getting infected -- and so does an uninfected mosquito, who might bite an infected dog later. That stops the transmission of both resistant and non-resistant heartworm.

On top of that, the repellent and insecticide killed 98% of the mosquitos exposed to a protected dog. That's good news for everyone, including humans, cats and other pets, who would benefit from a reduced mosquito population. "In areas where mosquitoes are abundant, hundreds, and possibly thousands, of mosquitoes can bite a dog in a 24-hour period," said McCall. "The use of a repellent and insecticide could reduce this by 95% or more for an entire month."

While there's no such thing as 100% protection when it comes to living creatures, this double-defense of topical repellent and oral preventive medication is about as close as you can get.

Although cats also suffer from heartworm infection, there is currently no repellent safe for use on them. Owners of both cats and dogs should keep the treated dog away from the cat until the topical repellent is fully dry, usually a few hours after application.

Dog owners can learn more at, and should consult their veterinarian about how to best protect their pets from heartworm infection.


Feline liver mass

usually benign

Q: My 8-year-old cat has been diagnosed with a biliary cyst. Can you tell me anything about this condition?

A: That's an interesting question. A biliary cyst is a large, fluid-filled growth on the bile duct system of the liver. It's the most common type of liver mass seen in cats, but the incidence isn't very high -- about 5.5%. Biliary cysts usually affect senior cats older than 10 years.

Cats with biliary cysts may have a decreased appetite and lose weight. If the mass is large enough -- some can be the size of a softball -- it may put pressure on the stomach and cause discomfort. The condition is usually diagnosed with an abdominal ultrasound exam.

The good news is that the cysts are benign and don't spread elsewhere in the body. The bad news is that they often require surgical removal, the sooner the better. Fortunately, they don't typically invade the liver, so the surgery tends to be uncomplicated.

One potential risk, though, is excessive bleeding, which sometimes occurs when tumors are removed from the liver. Another is if cats refuse to eat after surgery, especially if those cats are overweight. It might seem like a good way for the cat to lose some weight, but lack of appetite is downright dangerous for fat cats because it puts them at risk for a serious condition called hepatic lipidosis. These cats may need to have a feeding tube placed to make sure they take in enough nutrition until they recover.

Generally, the prognosis is good for cats with biliary cysts. Once the mass is removed, it usually doesn't return quickly. Depending on location and whether a cat has complications, the cost of surgery and aftercare can approach $6,000, but a good pet health insurance policy will cover most of the expense. -- Dr. Marty Becker

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Dogs, livestock at

risk from algal blooms

-- Summer temperatures continue well into September in many parts of the country. Protect dogs from toxic blue-green algae by keeping them out of warm, shallow, stagnant bodies of water such as ponds and lakes. Those are the conditions under which the algae begin producing toxins that can cause liver damage or failure, leading to death. Swimming in or ingesting a few mouthfuls of contaminated water can kill a dog and can make humans sick, too. Signs of toxicity include excessive drooling, fatigue, difficulty breathing, vomiting, diarrhea, seizures and death within minutes to hours of exposure. There’s no antidote to algae poisoning, but immediate veterinary treatment of symptoms with anti-seizure medication, oxygen and supportive care may save the dog’s life.

-- Vegetarian? Don’t try to get your cat to join you. Meat contains a nutrient called taurine that’s essential for heart and eye health and cell, muscle and skeletal function. Cats can’t synthesize taurine on their own, so they must get it from their diet.

-- The following five tips can help your pet’s veterinary visits go more smoothly. 1. Accustom your pet from an early age to going into a carrier and riding in the car. 2. Schedule “practice visits” to the veterinarian where your pet simply goes in and gets petted by and receives treats from staff so that he develops a positive association with the clinic and the people there. 3. Accustom pets to being touched all over the body so that an exam is less distressing to them. 4. Check in via phone once you’ve parked, then wait in the car until you receive a call that the exam room is ready for your pet to go right in. 5. Bring tasty treats to reward your pet through the exam and any procedures. Find more advice on making veterinary visits less stressful at -- Dr. Marty Becker, Kim Campbell Thornton and Mikkel Becker


Pet Connection is produced by a team of pet care experts headed by “The Dr. Oz Show” veterinarian Dr. Marty Becker, founder of the Fear Free organization and author of many best-selling pet care books, and award-winning journalist Kim Campbell Thornton. Joining them is behavior consultant and lead animal trainer for Fear Free Pets Mikkel Becker. Dr. Becker can be found at or on Twitter at DrMartyBecker. Kim Campbell Thornton is at and on Twitter at kkcthornton. Mikkel Becker is at and on Twitter at MikkelBecker.