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Heartworm Disease and Omaha Pets

Learn how to treat and prevent heartworm
Heartworm Disease and Omaha Pets
Published on August 1, 2010 : 8 comments

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During the spring and summer of 2010, I have seen more heartworm positive dogs than the total number I had previously seen in my entire career. Other Omaha veterinarians have similarly alarming accounts.

Heartworm disease is most common in hot, humid areas. It is spread by mosquitoes, so it thrives where mosquitoes thrive. The preferred host of heartworm larva is dogs, though it will also infect other animals, including cats, ferrets, raccoons, foxes, wolves and rarely, humans.

If I could speak for every veterinarian, I would say that we are concerned. And we are over ourselves. We thought we could beat the system. Heartworm is a seasonal and regional disease. We know our seasons! We know our region! But…

  • Have you noticed how rainy and humid it has been this summer? Mosquitoes love moisture.
  • Have you noticed the unpredictability of weather patterns in Omaha? In fact, I believe I may have heard a joke or two about that very subject…
  • Have you noticed how often families travel and relocate with their pets? Pets bring their parasites with them wherever they go.

Heartworm disease is present in the mosquitoes, pets and, wildlife in every state in the country to varying degrees. In some areas of Florida and Texas, for example, a dog who is not on a heartworm preventative medication will almost assuredly be heartworm positive. In Omaha, about ten percent of dogs not on heartworm prophylaxis in a given year will contract heartworm disease, which means that a dog who is not ever on a preventative medication will most likely contract heartworm disease in his or her lifetime. The incidence in cats and ferrets is lower than that in dogs but still significant.

Prevention of heartworm disease consists of a monthly oral medication (dogs, cats and ferrets) or monthly topical medication (dogs and cats) or an injection (dogs only) given every six months, all of which are very safe and very effective. An annual blood test is done (dogs only) to screen for the presence of adult heartworms.

When Hurricane Katrina occurred in 2005, many dogs were—thankfully—rescued and re-homed from Louisiana and surrounding areas. Over half of these pets were infected with heartworm disease. 

Pet RescuePet rescuers did all they could to screen and treat their charges who were heartworm positive. Treatment can take several weeks to months, and in the meantime, new mosquitoes in new states were biting the rescued dogs and infecting new dogs. These new dogs may not have been on preventative treatment because the incidence in their area had beforehand been so low.

The jury is still out among veterinarians over how much of an impact Katrina has had on the demographics of heartworm disease in America, but I suspect that it has contributed significantly to its rise. One of the disheartening aspects of heartworm disease is that it is unquestionably becoming more common among our pets, though it is completely preventable.

I know of very few veterinarians who would ask you to do what they themselves would not be willing to do for their own pets.  We will tell you the American Heartworm Society guidelines, and the wisest course of action and the reasons behind it, but we will also tell you whether we ourselves treat our dogs seasonally and our cats at all.

Since my family has lived in Omaha, I have tested each of my own dogs yearly and treated them with monthly heartworm preventative medicine from April through November. For the first time, I plan on continuing monthly heartworm preventative medicine for all three of our dogs through this coming winter and every month for the rest of their lives.

Max the catI will still stand on a box and yell, as I always yell to anyone I think may be listening, “Have your dog heartworm tested every year! Have your dog on a preventative medication!” Only now I am also stepping off of my box and saying quietly and humbly to you directly, “You might want to consider year-round prevention.  Heartworm disease has become more prevalent in Omaha, and it sure couldn’t hurt to take extra precautions. I am with my dogs.”

Oh, and also, I recently started Max the Cat on heartworm preventative medicine for the first time in all his many years.  If you would like, I will tell you about how I reached that decision too…

Finch93Shawn Finch is a veterinarian and Mom. She works at Banfield, The Pet Hospital of Papillion. She writes for her own website (, and Carefresh. :)


Shawna (not verified) says:

August 6, 2010 : 13 years 34 weeks ago

Shawna's picture

Dr. Finch — I’m a bit confused. The American Heartworm Society says that it takes 5 to 6 months after infection to accurately test for heartworm (quote and link below). If this is true how could vets in Omaha get so many positive test results due to this years wet weather? March was still too cold for the larvea to develop to the infective stage.

I ask this because my youngest (born with kidney disease - now 4) is not now nor has ever been on a conventional heartworm preventative. My vet agrees with this decision. I have her tested twice per year based on the 5 to 6 month criteria… Is this wrong?
“Test Timing for Optimal Results
Currently available heartworm antigen tests detect protein secreted mainly by adult female Dirofilaria immitis and the most useful microfilaria tests concentrate microfilariae and allow for more accuracy in identifying the filarial species. The earliest that heartworm antigen and microfilariae can be detected is about five and six months post-infection, respectively. Antigenemia may precede, but sometimes lags the appearance of microfilariae by a few weeks. Antigen may never be detected or only sporadically detected in dogs with very low worm burdens”


Finch93 says:

August 10, 2010 : 13 years 33 weeks ago

Finch93's picture

Hi Shawna!

You are absolutely right! Heartworms take at least five months and often longer to mature and begin releasing the antigen (females only) for which we most commonly test.

I believe this year’s increase in heartworm positive dogs in Omaha is probably due in part to after-effects of rescued heartworm positive dogs spreading throughout the country after Hurricane Katrina. Heartworm infections are also present in wildlife and of course, non-Katrina involved dogs who are not on preventatives.

My point with this summer’s hot, wet weather is that ideal mosquito thriving weather is not going to subside any time soon - the only way to protect pets with near 100% certainty is to have them on a heartworm preventative.

jesskamish says:

August 10, 2010 : 13 years 33 weeks ago

jesskamish's picture

Hi Dr. Shawn!
Thanks for the article. Heartworms are a fascinating topic to me. I didn’t realize that heartworms were transferred by a mosquito biting an infected dog. I guess I thought it was from another host like a raccoon or something. I learn something new about heartworms all the time! =)

I tend to have more of a holistic mindset about my pugs health care. What do you think about using other preventative measures to keep our pets healthy rather than the conventional medication?

I’ve read some articles online about how dangerous some of the side affects of the medication can be, and it makes me nervous to use the drugs. I, of course, want to do whatever I can to keep my pets healthy, I’m just not sure that the drugs are the way to go.

Do you hear this often? What’s your thought about using more natural ways to prevent heartworms?

Finch93 says:

August 10, 2010 : 13 years 33 weeks ago

Finch93's picture

Hi Jess!

That is a very good question. I do not like to use drugs/medication either unless the benefits will most likely outweigh the costs. In the case of heartworm preventative medications, the risk of side effects is much lower than the risks associated with NOT using a preventative.

Also, something you would not automatically know from looking at the packaging…the medication in the preventative is a tiny amount compared to that used to treat other diseases, which lowers the risks involved even further.

I have not found a mosquito repellant or natural heartworm larva killer that offers even near the protection that the “official” monthly and six month preventatives do, so I think they are still the best option for protection.

I LOVE the idea of keeping pets healthy through prevention rather than treatment whenever possible…I think heartworm preventative medication fits well with that mindset! This is one disease that is so much easier on pets to prevent than to treat!

Shawna (not verified) says:

August 10, 2010 : 13 years 33 weeks ago

Shawna's picture

Thanks Dr. Finch!! That makes sense :)

My youngest, as mentioned in earlier post, was born with kidney disease. I’ve done a lot of research since she came to me at nine weeks old and like Jessica was concerned about the conventional preventatives. I decided to give garlic instead (which in smaller amounts, I’m told by Dr. Karen Becker DVM and a few others, doesn’t cause Heinz Body Anemia). Dr. Becker has info on her website as well

I have study articles from respected journals and colleges stating that garlic does detract mosquitos as it disquises the carbon dioxide being emitted by the eater (fresh garlic - specifically the allicin in freshly crushed garlic).

Here’s one example:
“Colorado State University Extension
Garlic for Mosquitoes?
Edited by: Mary Schroeder, M.S., R.D. & Pat Kendall, Ph.D., R.D., Colorado State - Fall 2003
When garlic is eaten and its components are metabolized, compounds are released from the body through the skin and the breath. Although they may not be detectable by others (or may, in the case of garlic breath!), mosquitoes use smell to locate a host. For example, carbon dioxide and lactic acid released from the breath of humans are two known mosquito attractants that can be detected within 40 yards. While it has not been proven through clinical studies, it is thought that the sulfur compounds present on the skin and in the breath after eating garlic may help ward off those pesky mosquitoes.”

I eat a lot of garlic myself and have yet to be bitten this season.. I’m hoping it’s the garlic and that that same protection is experienced by my kidney girl..

I believe one of the B vitamins (as found in Brewer’s Yeast) likely has the same effect? Although I have not been able to find any credible data on this yet.

For my kd girl, would you say the risk is greater for her using the heart worm prevantative or the alternatiives. I use an essential oil spray on her as well but mainly rely on the garlic.

Dr. Martin Goldstein DVM, in his book, says he has “cured” heartworm with black walnut. I believe the tincture is not kidney friendly though…. He suggests black walnut to those of his clients that feel better using a preventative.

Lastly, I recently came across one study paper discussing ginger.

Wendell L. Combest, Ph.D.
Associate Professor of Pharmacology Department of Pharmaceutical Sciences Campbell
University School of Pharmacy, Buies Creek, NC
Alcoholic extracts of ginger injected subcutaneously (100 mg/kg) in dogs infected with Dirofilaria immitis reduced microfilarial concentrations in the blood by 98%.”

Thanks for your thoughts and guidance. Much appreciated!

Finch93 says:

August 10, 2010 : 13 years 33 weeks ago

Finch93's picture

Hi Shawna!

Yes, you are right, those compounds (garlic and Brewer’s yeast) can deter mosquitoes. I do not advocate garlic at all in dogs because of it’s effect on the cell membrane of red blood cells. At low levels, it causes low levels of damage, and at higher levels, it causes higher levels of damage, clinically manifesting in Heinz Body Anemia, like you mentioned. My opinion is that any level of damage is not ideal, even if it is not clinically detected.

I do not doubt the findings of the veterinarians who have had success with black walnut and ginger in treating heartworm disease, but I still feel most confident using treatment that has been proven in controlled studies with large numbers of dogs (It’s the scientist in me!) and that is approved by Veterinary Parasitologists and the American Heartworm Society. New studies with new compounds are awesome, I just don’t think they should replace our standard of care unless they have been proven to be more beneficial or safer or both.

I still think even with a mosquito deterrent, a heartworm preventative is wise, for the mosquito that does get through…but YOUR vet knows YOUR pup and her history and current situation! Especially with her kidney issues, make sure you go with his or her recommendations!

Great job with the research and links! I would rather have a well-informed client say “Yeah, but” than have a pet owner who is NOT involved in medical decision making.

You know your pet best, and your veterinarian knows her medical situation best, so use my info as just that - info. Hope it helps more than muddies the water!

(I love talking about heartworm disease with you! Thanks! Since isn’t paper based, they won’t mind if we keep going… :))

Shawna (not verified) says:

August 10, 2010 : 13 years 33 weeks ago

Shawna's picture

Thank you for the offer to continue this conversation :)

Many of the vets (or maybe most) whom I have dealt with in the past (at least 8 in the clinic I go to plus several more) seem put out if I question their insturctions/suggestions etc. How refreshing to have a vet willing to have an open discussion. Thank you for that as well. My vets have learned to deal with me but I have to wonder if they go “oh no not her” when I walk in the door :)… I’m involved in rescue so they see enough of me…

I learn not only by researching but by question/answer as well so please bear with me… You say that low levels of garlic have an effect on the cell membrane. Can that membrane repair itself or is it damaged for life? If the body can amply generate enough new cell growth is this a major factor? Have you experienced this in practice or something learned in a textbook or online? I’ll try to research this myself but sometimes when you get this detailed its quite hard to find reliable info..

Garlic has SOOO many health benefits I would hate to give it up to quickly :) Garlic kills giardia as an example. Its also one of the best food based prebiotics. The action of probiotics feeding is a nitrogen trap helping her kidneys and is also helping the innate immune system by amplifying neutrophils and monocytes… Between the antibacterial, antifungal, antiparasitic, immune boosting, blood cleansing benefits of garlic - I want to make sure the benefits don’t outweigh the one side effect you just made me aware of. Garlic is my little wonder buddy if you can’t already tell :) I use it almost daily myself..

I know where you are coming from with the heartworm preventative and I totally respect that. I just have to wonder if several years down the road the FDA doesn’t start releasing data on it as they have with flea/tick prevenatives? I know that’s a big IF especially when it comes to the consequences of having a heartworm infected dog… I’m sure the people who have had a heartworm positive dog are rolling their eyes wondering why I’m bothering with all this =] But, serveral vets I have talked with or read material from feel that heartworm preventatives increase the risk of cancer, as an example, not to mention other less serious diseases.

I am familiar with the recommendations from the American Heartworm Society (and actually quote from them often) but I also know there surely is a conflict of interest as at least eight of their sponsors are pharmaceutical companies.. Example: They discuss the temperature requirement for infection but then recommend year round preventatives nation wide? Additionally I have to wonder if, like with the Rabies Challenge Fund, alternative treatments just aren’t tested because there is no money in it for the players financially at risk??

One of the products tested and suggested by agriculture for landscaping mosquito control is garlic sprays — why then haven’t they tested the alternatives? Obviously a rhetorical question :) Just throwing it out there.

Anyway, I’ve taken up enough of your time today.. Thanks again for taking the time to discuss this further.. You truly are a champion of vets. I just might have to see how far you are from me :)


Finch93 says:

August 11, 2010 : 13 years 33 weeks ago

Finch93's picture

Hi Shawna!

Just so you know, I work very hard to make sure as many as my clients are as invested in their pets as you are. I have even had other vets and team members ask why my client base is so great :D

I did not mean garlic is not good for people! It is awesome for us - do not give it up. For dogs and cats, they have a weird toxicity issue in which garlic lyses (destroys) the cell membranes of their red blood cells. The cell membrane cannot be repaired, but of course the body is constantly making new red blood cells, even in the best of times, adjusting output based on need.

I know pharmaceutical companies help out the American Heartworm Society, but I do believe they have an interest in helping pets too. And I do trust their recommendations as their medical inferences and research seem solid to me. Part of the reason they recommend year-round treatment is compliance - easier to remember. But also weather patterns change and people (and pets) move around. I have decided to treat our three year round, even though winter in Omaha is very (very) cold, mainly so I don’t have to guess upcoming weather patterns. Until I was doing year round, I didn’t feel comfortable suggesting it to clients! But of course, everyone gets to make their own decisions for their own pets…as it should be :)

Hope I didn’t miss anything! Talk to you soon I hope!!