According to Cathy Connelly, DVM, of Community Animal Hospital in Reno, pet owners in northern Nevada should be concerned because heartworms now are more prevalent in the area than ever before.
“We’re seeing some cases (of heartworm) in dogs that are in this area that have supposedly never been out of the state,” Connelly said.
She explained that heartworm disease historically has been common in parts of California, and dogs that traveled to that area sometimes contracted the disease. But dogs that had spent their entire life in Nevada were less likely to be infected.
It appears that is not the case anymore, Connelly said.
Heartworms are spread by mosquitoes, and Connelly said the disease is spread when a mosquito bites an infected animal, picks up heartworm and then bites another animal, such as a dog. Heartworm cannot be spread directly from dog to dog; a mosquito is required for transmission.
According to Bridget Landon, DVM, of Fairgrounds Animal Hospital, mosquito abatement programs in northern Nevada were implemented to prevent the spread of West Nile Virus and keep mosquitoes at bay, but it is still possible for a dog to be bitten by a heartworm-carrying mosquito in Reno.
“Adult heartworms live in the heart and pulmonary arteries of infected dogs,” a Community Animal Hospital information sheet states. “They live up to five years, and during this time, the female produces millions of offspring called microfilaria. These microfilariae live mainly in the small vessels of the bloodstream.”
Immature heartworms cannot complete their life cycle in a dog, and that is where the mosquito comes in. The mosquito bites the infected dog and ingests the microfilariae, which then further develop inside the mosquito for 10 to 30 days.
After developing inside the mosquito, the microfilariae are considered infective larvae because they have reached a point where they can grow to adulthood when they enter a dog or cat.
“Heartworm is a very dangerous disease,” the website www.dogheartworm.org states. “It can kill your dog if you don’t do something about it.”
“We recommend keeping dogs on heartworm medication all year,” Connelly said, adding that heartworm is more prevalent during mosquito season, which begins in the spring.
Dogheartworm.org recommends treating a pet immediately if it contracts heartworm, or better yet, prevent the pet from getting it in the first place.
“Heartworm in dogs is a type of disease that can easily be prevented,” the website states. “There are preventives in the form of injections and oral medicines. The injection is usually given to the dog on a monthly basis, quite diligently during the heartworm peak season. Examples of such vaccines are Ivermectin, Milbemycin, Lufenuron and Selamectin.”
It can take years for an owner to realize that an animal is infected with heartworm. The first symptom usually is coughing.
“As the parasites find their way from the heart and into the lungs, it will cause a group of symptoms similar to a pulmonary disease like lung cancer,” www.dogheartworm.org states. “Hemoptysis and chest pain come along with it.”
Heartworm in dogs can be difficult to detect until it is in advanced stages, but Connelly said there are several ways to test for it, including blood tests, x-rays and ultrasounds.
“We test dogs every year,” she said, adding that sometimes the larvae can be seen under a microscope in a blood smear.
Connelly operates a mobile ultrasound unit, which she often takes to other area clinics, and she said recently she performed an ultrasound on a dog that had a very advanced case of heartworm. This case was interesting, she said, because the dog spent its life in Nevada, having been born and raised in Reno.
“I’m not sure how much it traveled,” she said, adding the dog likely traveled to Lake Tahoe or other nearby recreation areas.
Regardless of where the animal contracted heartworm, it had to be euthanized because of the advanced stage of the disease, Landon said.
“In this case, the worms would have had to be removed surgically,” she said. “The owner elected to euthanize.”
Animals diagnosed with advanced heartworm disease are not likely to live more than a few weeks or months, the Community Animal Hospital release states. Advanced cases are those where the disease has been present long enough to cause substantial damage to the heart, lungs, blood vessels, kidneys and liver.
“A few of these cases will be so advanced that it will be safer to treat the organ damage rather than risk treatment to kill the heartworms,” the release states.
When possible, treatment of heartworm disease can be risky, Connelly said.
“The treatment can be very painful,” she said, and sometimes fatal. “When you kill the larvae, they can become dislodged and go into the lungs, resulting in death.”
The best medicine is prevention, Connelly and Landon said.
“I have seen dogs fall over and die from heartworm disease,” Landon said, but an array of preventative treatments is available.
“We have a lot of options,” Landon said, everything from topical medications to flavored treats. “And they are really safe.”