Current Canine Guidelines for the Prevention, Diagnosis, and Management of Heartworm (Dirofilaria immitis) Infection in Dogs Revised 2018 Current Canine Guidelines for the Prevention, Diagnosis, and Management of Heartworm (Dirofilaria immitis) Infection in Dogs (Revised 2018) CONTENTS Thank You to Our Generous Sponsors: Click on the links below to navigate to each section. Preamble .....................................................................................................................................................................3 HIGHLIGHTS ................................................................................................................................................................3 EPIDEMIOLOGY ..........................................................................................................................................................4 Key Points Minimizing Heartworm Transmission in Relocated Dogs (box) Figure 1. Urban heat island profile. BIOLOGY AND LIFE CYCLE ........................................................................................................................................7 Key Points Figure 2. The heartworm life cycle. Figure 3. Images of a feeding mosquito. HEARTWORM PREVENTION .....................................................................................................................................9 © 2018 American Heartworm Society | PO Box 8266 | Wilmington, DE 19803-8266 | E-mail: [email protected] Key Points Macrocyclic Lactones Reports of Lack of Efficacy Vector Control Measures to Reduce Heartworm Transmission (box) Use of Repellents and Ectoparasiticides Multimodal Risk Management PRIMARY DIAGNOSTIC SCREENING ......................................................................................................................14 Key Points Test Timing for Optimal Results Microfilaria and Antigen Testing Antigen Tests When Should Heat Treatment of Samples Be Considered? (box) Microfilaria Tests How to Perform the Knott Test (box) Testing Considerations Following Noncompliance and When Changing Products Figure 4. Acanthocheilonema reconditum and Dirofilaria immitis. Figure 5. The testing protocol following known noncompliance. 2018 Canine Heartworm Guidelines 1 Other Diagnostic Aids ..............................................................................................................................................18 Prepared by Dr. C. Thomas Nelson, Dr. John Radiography W. McCall, Dr. Stephen Jones, and Dr. Andrew HIGHLIGHTS Echocardiography Moorhead, and approved by the Executive Board of • Diagnostics Figure 6. Moderate heartworm disease (radiographs). the American Heartworm Society: Officers: Dr. Chris AHS recommends annual antigen and Figure 7. Severe heartworm disease (radiographs). Rehm, President; Dr. Stephen Jones, Past President; microfilaria testing. (As the interpretation Figure 8. Echocardiogram. Dr. Tony Rumschlag, Vice President; Dr. Bianca of diagnostics has become more complex, Zaffarano, Secretary-Treasurer; Dr. Patricia Payne, please see the “Microfilaria and Antigen Diagnostics For Pre-Adulticide Evaluation In An Infected Dog ............................................................................18 Editor; Dr. Doug Carithers, Symposium Program Testing” section for more complete Chair; Board Members: Dr. Elizabeth Clyde, Dr. Brian information.) PRINCIPLES OF TREATMENT ..................................................................................................................................20 DiGangi, Dr. Chris Duke, Dr. Andrew Moorhead, Dr. Key Points Charles Thomas Nelson, and Dr. Jennifer Rizzo; and • Prevention Table 1. Summary of Clinical Signs of Canine Heartworm Disease Ex Officio Members: Dr. Marisa Ames, Symposium AHS recommends year-round Figure 9. Image of the main trunk of the right pulmonary artery. Program Co-Chair; Dr. John W. McCall, Associate administration of preventive drugs Figure 10. Image of a dead adult heartworm lodged in a distal pulmonary artery. Editor; Dr. Chris Adolph and Dr. Edward Wakem. approved by the US Food and Drug Administration (FDA) to prevent heartworm Adulticide Therapy ...................................................................................................................................................21 References by Christopher Evans, MS, Research infection and enhance compliance, the Melarsomine Dihydrochloride Professional II, Department of Infectious Diseases, latter being particularly important in Pulmonary Thromboembolism College of Veterinary Medicine, University of light of the documented presence of Georgia. resistant subpopulations. Application Adjunct Therapy .......................................................................................................................................................22 Preamble of an Environmental Protection Agency Steroids (EPA) registered mosquito repellent/ NSAIDs and Aspirin These recommendations supersede previous ectoparasiticide has been shown to Doxycycline editions and are based on the information increase the overall efficacy of a heartworm Macrocyclic Lactones presented at the 2016 Triennial Symposium of prevention program in laboratory Macrocyclic Lactones/Doxycycline the American Heartworm Society (AHS), new studies involving known resistant Figure 11. Pulmonary pathology associated with death of heartworms. research, and additional clinical experience. The heartworm isolates by providing control recommendations for the prevention, diagnosis, of the arthropod vector of heartworm. In AHS-Recommended Protocol ..................................................................................................................................24 and management of heartworm infection in cats Table 2. AHS-Recommended Protocol addition, AHS recommends reduction of are contained in a companion feline document exposure to mosquitoes through standard (available on the AHS website). Elimination of Microfilariae ......................................................................................................................................26 environmental control of mosquitoes and their breeding environments, and when Surgical Extraction of Adult Heartworms ...............................................................................................................26 possible, reducing outdoor exposure during Caval Syndrome (Dirofilarial Hemoglobinuria) key mosquito feeding periods. Pulmonary Arterial Infections • Adulticide Therapy Figure 12. Photographic Image of a heart from a dog suffering from caval syndrome. AHS recommends use of doxycycline and a Figure 13. Echocardiogram image. macrocyclic lactone prior to the three-dose Figure 14. Surgical removal of worms. regimen of melarsomine (one injection of 2.5 mg/kg body weight followed at least Alternative Therapies ................................................................................................................................................28 one month later by two injections of the Long-term Macrocyclic Lactone Administration same dose 24 hours apart) for treatment of Herbal Therapies heartworm disease in both symptomatic and asymptomatic dogs. Any method Compounded Medications .......................................................................................................................................28 utilizing only macrocyclic lactones as a slow-kill adulticide is not recommended. Confirmation of Adulticide Efficacy .........................................................................................................................28 Elective Surgeries in Dogs with Heartworms .........................................................................................................29 REFERENCES .............................................................................................................................................................29 2 American Heartworm Society 2018 Canine Heartworm Guidelines 3 EPIDEMIOLOGY Heartworm infection in dogs has been diagnosed around the globe. In the United States, its territories, and protectorates, heartworm is considered at least regionally endemic in each of the contiguous 48 states, Hawaii, Puerto Rico, US Virgin Islands, and Guam (Bowman et al, 2009; Kozek et al, 1995; Ludlam et al, 1970). Heartworm transmission has not been documented in Alaska; however, there are regions in central Alaska that have mosquito vectors KEY POINTS: and climate conditions to support the transmission EPIDEMIOLOGY of heartworms for brief periods (Darsie and Ward, • Heartworm infection has been diagnosed 2005; Slocombe et al, 1995; Terrell, 1998). Thus, in all 50 states and around the globe. the introduction of microfilaremic dogs or wild • Environmental and climatic changes, canids could set up a nidus of infection for local both natural and those created by transmission of heartworm in this state (see box on Figure 1. Urban heat island profile showing the elevation in urban air temperature compared with rural air temperature. (Image courtesy of Heat Island Group, Lawrence Berkeley National humans, relocation of microfilaremic page 5 for more on the role of transport of infected Laboratory). dogs, and expansion of the territories of dogs). Such relocation of microfilaremic dogs and expansion of the territories of microfilaremic microfilaremic wild canids continue to be Urban sprawl has led to the formation of The length of the heartworm transmission season in wild