VETgirl December 2024 BEAT e-Magazine

QUARTERLY BEAT / DECEMBER 2024

REFERENCES

1. Hays KM, Rodriguez JY, Little SE, Litster AL, Mwacalimba KK, Sundstrom KD, Amodie DM, Serrano MA, Guerios SD, Lane JN, Levy JK. Heartworm prevalence in dogs versus cats: Multiple diagnostic modalities provide new insights. Vet Parasitol. 2020;277S:100027. doi: 10.1016/j. vpoa.2020.100027. Epub 2020 Jun 12. PMID: 34392951. 2. Atkins, CE, DeFrancesco TC, Coats JR, Sidley JA, Keene BW. Heartworm infection in cats: 50 cases 1985-1997). J Am Vet Med Assoc. 2000;217, 355-358.

By conducting these antibody and antigen tests concurrently on a routine basis, practitioners can increase the odds of accurately diagnosing feline patients. Routine testing can also help veterinarians establish a diagnosis when clinical evidence of infection exists, monitor the status of cats already diagnosed with heartworms, establish a baseline prior to beginning a heartworm prevention product, and help veterinarians understand the relative risk of feline heartworm in their geographical practice area. When antigen and antibody tests do not provide a positive diagnosis, radiography, echocardiography and point of care ultrasound can also assist in finding evidence of heartworm disease. It's the AHS’ hope that increased testing will also lead to improved understanding of the disease and increased awareness of its prevalence in cats. Such a shift could also spur research into improved diagnostic and treatment strategies for cats.

The updated AHS feline guidelines now also include a discussion of the importance of vector control in preventing heartworm infection in cats. Because cats are sensitive to many of the pesticide products considered safe for dogs, environmental vector control becomes especially important. Strategies include eliminating sources of standing water or treating sources of standing water with chemical and/or biological tools such as insect growth regulators, Bacillus species and mosquito fish. In addition, owners can limit their cats’ outdoor exposure and utilize local environmental application of insecticidal sprays and fogs, as well as adult mosquito traps. MANAGEMENT OPTIONS FOR CATS WITH FELINE HEARTWORM DISEASE With more routine testing, veterinarians can logically expect numbers of cats diagnosed with heartworms to increase. Because there are no adulticide treatments approved for cats, the AHS guidelines now include updated recommendations for managing cats that have become infected. These recommendations are designed to relieve the clinical signs of disease and, in cases of adult infection, to prevent sudden death of cats. Within the updated guidelines, veterinarians will find specific dose, route, and frequency recommendations for treatment of acutely dyspneic cats, as well as cats with chronic disease or asymptomatic infection.

scientific information that supports a more proactive approach to heartworm diagnosis, as well as greater specificity in prevention and treatment approaches. If these recommendations are widely adopted, we believe it will encourage further advancements in testing, treatment, and prevention for a class of patients that has been historically overlooked. The AHS Heartworm Management Guidelines for dogs and cats are living documents that are updated as appropriate when new information and evidence comes to light. The AHS Board of Directors would like to thank the following board members who serve on the Heartworm Guidelines Committee:

• Charles Thomas (Tom) Nelson, DVM • John McCall, MS, PhD • Andrew Moorhead, DVM, MS, PhD, DACVM (Parasitology) • Lindsay Starkey, DVM, PhD, DACVM (Parasitology) • W. Mark Cousins, DVM, DABVP (Feline Practice) • Marisa Ames, DVM, DACVIM (Cardiology)

When treating infected cats, veterinarians can consider the following medications:

• Prednisolone to relieve coughing and other respiratory signs • Doxycycline to eliminate Wolbachia organisms from heartworms (these endosymbiont bacteria contribute to heartworm pathogenesis in cats as well as dogs)

• Antileukotrienes to prevent respiratory crisis • Macrocyclic lactone preventives to prevent new infection • Supportive therapy with corticosteroids, bronchodilators, oxygen, fluids and thermal support during episodes of respiratory distress The revised AHS recommendations also provide guidance for veterinarians considering surgical removal of adult heartworms in cats, for such cases where it may be deemed necessary. As an organization that is dedicated to reducing the incidence of heartworm disease and its impact on pets, the AHS has long been concerned about the underdiagnosis and undermanagement of heartworm disease in cats. We now have

ROUTINE YEAR-ROUND HEARTWORM PREVENTION NOW INCLUDES VECTOR CONTROL For years, the AHS has recommended routine use of heartworm preventives in cats. Any cat that lives where heartworm-positive dogs and wild canids exist is at risk for heartworm transmission, and with no treatment for adult heartworm infection approved in cats, year-round prevention of heartworms is the best means of protecting these patients from a potentially life-threatening infection. Indoor cats are no exception, as mosquitoes can enter homes and transmit infective heartworm larvae to unprotected animals. In a retrospective study conducted at North Carolina State University, roughly one in four cats found to be heartworm- positive were identified by their owners as “indoor” pets. 2

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