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In the News

The American Heartworm Society is the leading resource on heartworm disease, and our mission is to lead the veterinary profession and the public in the understanding of this serious disease. Every year, hundreds of stories are written on the diagnosis, prevention and treatment of heartworm, as well as on the plight of affected pets. These stories are an important way of reaching both veterinary professionals and pet owners with information they need to know about heartworm disease.

The American Heartworm Society is led by a board of directors comprised of veterinarians and specialists in the fields of veterinary parasitology and internalmedicine. As leaders in the fight against heartworm disease, they are available as resources and authors of related stories.

Members of the media are encouraged to contact the American Heartworm Society for information, visuals and interviews about heartworm disease. Please contact Sue O’Brien at This email is for media inquiries only. All other inquiries, please email:



News & Alerts

Heartworm: Where Are We Today?

Warnings and reports about pets infected with Dirofilaria immitis in the United States are not unusual. In fact, canine heartworms were first discovered on the southern US coast in 1856.1 What should be making headlines is the fact that despite the preventive medications that have been widely available for decades, the incidence of heartworm disease continues to rise across the nation.


AHS introduces algorithm to minimize heartworm transmission in relocated dogs

From The American Heartworm Society (AHS) has announced a new set of best practices for minimizing heartworm transmission in relocated dogs, including recommendations for testing, treatment and prevention, that were developed in collaboration with the Association of Shelter Veterinarians (ASV), according to a society release.

Send a Clear Parasite Prevention Message

Clients simply aren’t getting the message when it comes to preventing fleas, ticks, and in particular heartworm.


American Heartworm Society announces 2018 Heartworm University schedule

AHS symposia, proceedings bring heartworm education to veterinary professionals.

The American Heartworm Society (AHS) is redoubling efforts to bring the latest heartworm information directly to veterinarians and veterinary nurses via scientific symposia and proceedings.




10 Myths About Heartworms

It takes just one bite from a mosquito infected with heartworm larvae to jeopardize your pet’s health and welfare. Heartworm disease is often debilitating and can be fatal if not treated. That’s why the stakes are too high to listen to myths like only dogs are susceptible to heartworms and heartworm disease is just a summer issue.

AHS Heartworm Hotline Wolbachia and Heartworm: Why Doxycycline Is Needed in Heartworm Treatment

The treatment of adult heartworm (Dirofilaria immitis) infection in dogs has changed significantly since the days when veterinarians’ only option was injectable thiacetarsamide sodium. First, the introduction of melarsomine dihydrochloride in the mid-1990s revolutionized the treatment of adult heartworm infection by providing superior efficacy via intramuscular administration.1 The next great leap forward in heartworm treatment came with the discovery that some filarial worms harbor a type of bacteria, Wolbachia, and that elimination of these bacteria proved beneficial to the animal and reduced the complications of disease.2


Pulmonary Hypertension & Heartworm Disease

In the Literature
Serrano-Parreño B, Carretón E, Caro-Vadillo A, FalcónCordón S, Falcón-Cordón Y, Montoya-Alonso JA. Pulmonary hypertension in dogs with heartworm before and after the adulticide protocol recommended by the American Heartworm Society. Vet Parasitol. 2017;236:34-37.

FROM THE PAGE … Pulmonary hypertension is one of the most serious complications that can occur in dogs with heartworm disease. The inflammatory response can increase during adulticide therapy as worms die and an increased amount of antigen is released.


Photo courtesy of the ASPCA

Help Stop Heartworm Travel Plans

The American Heartworm Society announces new “best practices” to help stop heartworm transmission via transported dogs.

(Photo courtesy of the ASPCA)

Transporting and relocating dogs is an increasingly common practice.

Whether the situation is an owned pet accompanying emigrating or traveling caretakers, the relocation of homeless animals for adoption, or the movement of dogs for competition, exhibition, research or sale, this process carries the risk of spreading infectious diseases.This includes the transmission of Dirofilaria immitis when infected dogs have become microfilaremic.

The following practices will minimize the risk of heartworm transmission associated with the transportation and relocation of dogs ( pdfFull Story): 

1. Test all dogs greater than 6 months of age for microfilariae (Mf) and heartworm antigen (Ag) prior to relocation.

a. If testing is not possible, assume transmission is possible and proceed to Step 3b.

2. If dogs test positive for microfilariae or antigen, reconsider relocation at this time and begin treatment in accordance with the American Heartworm Society (AHS) Guidelines.

a. Dogs with clinical signs attributed to heartworm infection should not be transported.

b. Dogs that have been treated with melarsomine dihydrochloride should not be transported for at least 4 weeks after an injection to minimize stress and physical exertion that accompany the relocation process.

3. If dogs test positive and relocation cannot be postponed, clinical decisions should be based on the dog’s heartworm status.

a. If Mf-, Ag+:

i. Administer an approved macrocyclic lactone product. This should prevent the prepatent dog from becoming microfilaria positive.1

ii. Begin doxycycline therapy.
A 4-week course of doxycycline should prevent the pre-patent dog from becoming microfilaria positive.2,3

iii. Repeat Knott’s testing in 7 days; if negative, proceed with relocation. If positive, repeat Knott’s testing in 7 days.
Two negative tests 7 days apart can provide reasonable assurance of a lack of circulating microfilariae and reduced risk of transmission.

b. If Mf+, Ag- or Mf+, Ag+:

i. Apply an approved moxidectin topical product and proceed with relocation.
A single dose of topical moxidectin prior to transport will eliminate most microfilariae.4-6
Administer an approved macrocyclic lactone product along with a topical canine insecticide (containing permethrin + dinotefuran + pyriproxyfen) that is labelled to kill and repel mosquitoes. This will prevent infection of mosquitoes and subsequent transmission of infective larvae during transportation and for 1 month thereafter.7

ii. Begin doxycycline therapy.
Administration of a 4-week course of doxycycline will render microfilariae incapable of normal development to infective larvae in mosquitoes and subsequent development of these larvae in dogs.8,9

Once heartworm-positive dogs have been safely transported, heartworm treatment should be completed according to AHS Guidelines as soon as possible.

4. If dogs test negative for microfilariae and antigen, proceed with relocation.

a. Administer macrocyclic lactone preventive drugs to dogs greater than 6 weeks of age prior to relocation.1

b. Repeat microfilariae and antigen testing in 6 months. If a history of preventive administration is well-documented, repeat testing in 12 months.1

Caring for dogs that undergo relocation is an everyday challenge veterinarians face in today’s mobile society, and one that necessitates the adoption of approaches to mitigate heartworm transmission.

Along with considering the recommendations in this document, veterinarians should ensure that transportation of animals is carried out in accordance with state and/or federal transportation regulations, as well as professional guidelines.10,11

In the case of organized homeless animal relocation programs, veterinarians should work with both source and destination organizations to establish protocols for minimizing transmission of infectious diseases, including heartworm disease.

SKO Transport Guidelines Algorithm

1. American Heartworm Society. Current Canine Guidelines for the Prevention, Management, and Diagnosis of Heartworm Infectionin Dogs. Available online here
2. Hoerauf A, Mand S, Fischer K, et al. Doxycycline as a novel strategy against bancroftian filariasis – depletion of Wolbachia endosymbionts from Wuchereria bancrofti and stop of microfilaria production. Med Microbiol Immunol. 2003; 192:211-216.
3. Rossi MID, Paiva J, Bendas A, et al. Effects of doxycycline on the endosymbiont Wolbachia in Dirofilaria immitis (Leidy, 1856) —Naturally infected dogs. Vet Parasitol. 2010; 174:119-123.
4. Bayer Healthcare LLC. Advantage Multi® Product Label. Available online here
5. Blagburn BL, Dillon AR, Arther RG, et al. Comparative efficacy of four commercially available heartworm preventive products against the MP3 laboratory strain of Dirofilaria immitis. Vet Parasitol. 2011; 176:189-194.
6. McCall JW, Arther R, Davis W, Settje T. Safety and efficacy of 10% imidacloprid + 2.5% moxidectin for the treatment of Dirofilaria immitis circulating microfilariae in experimentally infected dogs. Vet Parasitol. 2014; 206; 5-13.
7. McCall JW, Hodgkins E, Varloud M, et al. Blocking the transmission of heartworm (Dirofilaria immitis) to mosquitoes (Aedes aegypti) by weekly exposure for one month to microfilaremic dogs treated once topically with dinotefuran-permethrin-pyriproxyfen. In Proceedings, 2016 American Heartworm Society Triennial Symposium. Parasites & Vectors, 2017, in press.
8. McCall JW, Genchi C, Kramer L, et al. Heartworm and Wolbachia: therapeutic implications. Vet Parasitol. 2008; 158:204-244.
9. McCall JW, Kramer L, Genchi C, et al. Effects of doxycycline on heartworm embryogenesis, transmission, circulating microfilaria, and adult worms in microfilaremic dogs. Vet Parasitol. 2014; 206(1-2):5-13.
10. American Veterinary Medical Association. Relocation of Dogs and Cats for Adoption: Best Practices. Available online here
11. Association of Shelter Veterinarians. Guidelines for Standards of Care in Animal Shelters. Available online here.

AHS Heartworm Hotline Beyond the Map: The State of Heartworm Incidence in the United States

How many pets in the United States are infected with heartworms? The truth is that no one knows. Because heartworm diagnosis requires one or more blood tests that must be conducted in a veterinary clinic and/or testing laboratory, diagnosis is limited to patients seen in veterinary hospitals and animal shelters. Dogs and cats not seen by veterinarians and/or not tested for heartworms during annual veterinary visits may be infected but go unrecognized.


AHS Heartworm Hotline Turning Up the Heat on Heartworm Diagnosis

Antigen testing for Dirofilaria immitis has been a foundational component of model preventive veterinary care for many years, particularly for dogs. For privately owned pets, the results of such testing guide prevention strategies and, in the event of a positive result, treatment for heartworm disease. In shelter populations, the results are often a key determining factor in the management of a dog throughout its stay in the shelter system, including its likelihood of a live release.

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