Preventive Medicine PDF

Preventive Medicine 23 CHA P TE R Valerie A. Chadwick...

Preventive Medicine 23 CHA P TE R Valerie A. Chadwick D. Vaccines containing feline leukemia (with or with- VACCINATIONS out any other antigen except rabies) are adminis- I. Vaccinations are an important part of preventative tered on the left hindlimb as distally as possible medical practices, thus providing animals with opti- VI. Core vs. noncore vaccination mum health care A. Core vaccines are defined as vaccines appropriate A. Vaccination itself is a potent medical procedure to protect most animals against diseases that associated with known benefits and risks. Knowledge pose a risk of severe disease due to virulent, of these benefits and risks is necessary to implement highly infectious pathogens, as well as being an effective individualized vaccination protocol highly distributed B. Considerations of exposure, susceptibility, sever- B. Noncore vaccinations target diseases of minimal ity of disease, efficacy and safety of the vaccine, risk in the geographic region or lifestyle of the pet potential public health concerns, and owner’s and protect against diseases that are less severe preferences are appropriate threats to infected animals. Noncore vaccines II. Vaccinations have contributed greatly to the well-being should be considered on an individual basis of our companion animals. The number of patients C. Core vaccines with infectious disease has decreased appreciably 1. Canine: Core vaccines considered for dogs are since the first vaccines were available distemper, parvovirus, adenovirus-2, and rabies III. Recommendations for vaccines had been considered 2. Feline: Vaccines against panleukopenia, rhino- a routine part of animal care tracheitis, and calicivirus should be considered A. Differences in risk exposure to infectious dis- core vaccines for cats. Vaccines against feline eases, age and health of the patient, and potential leukemia virus should be considered a core side effects make it difficult to recommend one vaccine if the cat spends time outdoors or has protocol for all dogs or cats interaction with outside cats B. An annual wellness examination should be recom- D. Noncore vaccines mended even if the vaccinations are not being 1. Canine: Noncore vaccines considered for the given in a particular year for the overall continued dog are parainfluenza, Bordetella, coronavirus, health of the animal Lyme disease, and Giardia. Leptospirosis may IV. Puppies under 16 weeks of age represent the most be considered either core or noncore, depend- susceptible age group ing on the area of the country the dog is living A. They experience the highest rates and most se- in and exposure risk vere cases of disease and therefore the principal 2. Feline: Noncore vaccines to consider for the target population for vaccination cat are chlamydiosis, feline infectious peritoni- B. Because of maternal antibody influences, a series tis, Microsporum canis, bordetellosis, giardia, of periodically spaced vaccinations is indicated in and feline immunodeficiency virus (FIV) young dogs VII. Veterinarians should provide their clients with ade- V. Feline vaccination protocols quate information regarding vaccine choices so own- A. The American Association of Feline Practitioners ers can make an informed decision regarding vacci- and Academy of Feline Medicine created an advi- nations for their animals. Currently a signed consent sory panel in 1997 to develop guidelines for vacci- for administered vaccines is not required, but this nation of cats. These guidelines were adopted by may change with time (Table 23-1) the Vaccine-Associated Feline Sarcoma Task Force for administration of vaccines HEARTWORM AND FLEA B. Vaccines containing antigens limited to Rhinotra- PREVENTATIVES cheitis-Calicivirus-Chlamydia-Panleukopenia (RCCP) are administered subcutaneously on the I. Heartworm preventatives (Table 23-2) right shoulder A. Heartworm preventatives kill backwards in time C. A vaccine containing rabies virus antigen (plus 1. Ivermectin, milbemycin oxime, moxidectin, and any other antigen) is administered on the right selamectin kill L3 and L4 up to 60 days back in hindlimb as distally as possible time 332  CHAPTER 23 Preventive Medicine 333 Table 23-1 Canine and Feline Vaccinations Initial Puppy Initial Adult Dog Canine Vaccine Vaccination Vaccination Revaccination Comments Canine distemper virus Administer 6-8 wk Two doses 3-4 wk One year booster at Core (MLV) of age, then apart 15 mo then revac- every 3-4 wk cination once until 12-14 wk every 3 yr consid- old ered protective Canine distemper virus Administer 6-8 wk Two doses 3-4 wk One year booster at Core (rCDV) of age, then apart 15 mo, then revac- every 3-4 wk cination once until 12-14 wk every 3 yr consid- old ered protective Distemper-measles virus One dose only be- Not indicated ani- Not indicated animals Noncore tween 4-12 wk mals over 12 wk over 12 wk old Canine adenovirus-1 Not recommended. Signifi- cant risk of hepatitis blue- eye. CAV-2 cross protect against CAV-1 Canine adenovirus-2 (MLV) Administer 6-8 wk Two doses 3-4 wk One year booster at Core of age, then apart 15 mo, then revac- every 3-4 wk cination once ev- until 12-14 wk ery 3 yr considered old protective Canine adenovirus-2 (killed) Not recommended. CAV-2 (MLV) more effective Canine parvovirus (MLV) Administer 6-8 wk Two doses 3-4 wk 1- yr booster at 15 mo, Core of age, then apart then revaccination every 3-4 wk once every 3 yr until 12-14 wk considered protec- old tive Canine parvovirus (killed) Not recommended. This vaccine susceptible to maternal antibodies Canine parainfluenza virus Administer 6-8 wk One dose One year booster at Noncore (MLV) of age, then 15 mo, then revac- every 3-4 wk cination once ev- until 12-14 wk ery 3 yr is consid- old ered protective Leptospira interrogans Administer Two doses 2-4 wk Annual update Core, noncore (canicola, icterohaem- 12 wk of age, apart orrhagiae) (killed then booster bacterin) at 14-16 wk of age Leptospira interrogans (cani- Administer 12 wk Two doses 2-4 wk Annual update Core, noncore cola, icterohaemorrha- of age, then apart giae, pomona, grippoty- booster at phosa) (killed bacterin) 14-16 wk of age *Bordetella bronchiseptica Administer 6-8 wk Two doses 2-4 wk Annual update Noncore. Administer 1 wk (killed) – parenteral of age, then apart before exposure one dose 4 wk later Bordetella bronchiseptica Administer single One dose Annual update Noncore (live avirulent bacteria), dose (may give parainfluenza (MLV) – as early as intranasal 3 wk of age) Continued 334 SECTION II SMALL ANIMAL Table 23-1 Canine and Feline Vaccinations—cont’d Initial Puppy Initial Adult Dog Canine Vaccine Vaccination Vaccination Revaccination Comments Bordetella bronchiseptica Administer 8 wk Two doses 4 wk Annual update Noncore. Administer 1 wk (cell wall antigen of age, then apart before exposure extract) – parenteral repeat at 12 wk of age Canine coronavirus (killed Not recommended. and MLV) Clinical disease rarely occurs, typically self-limiting Rabies 1 yr (killed) Administer as One dose Annual update Core. State, local or early as 12 wk provincial laws apply of age Rabies 3 yr (killed) Administer as One dose Revaccination 1 yr Core. State, local or early as 12 wk following initial provincial laws apply of age vaccine, booster vaccines adminis- tered every 3 yr *Borrelia burgdorferi (killed Administer 9-12 Two doses 2-4 wk Annual update Noncore whole bacterin) wk of age, then apart booster with second dose 2-4 wk later *Borrelia burgdorferi Administer 9-12 Two doses 2-4 wk Annual update Noncore (recombinant-outer wk of age, then apart surface protein A) booster with second dose 2-4 wk later Giardia lamblia (killed) Administer 8 wk Two doses 2-4 wk Annual update Not recommended. Does of age, repeat apart not prevent infection in 2-4 wk Initial Kitty Initial Adult Cat Feline Vaccine Vaccination Vaccination Revaccination Comments Panleukopenia (MLV, Administer 6-8 Two doses 3-4 wk 1-yr booster after Core. MLV not for preg- killed), parenteral wk of age, apart primary vac- nant queens or kittens then every cines, then re- less than 4 wk of age 3-4 wk until vaccination once 12 wk old every 3 yr con- sidered protec- tive Panleukopenia (MLV), in- Administer 6-8 One dose 1-yr booster after Core. Not for pregnant tranasal wk of age, primary vac- queens then every cines, then 3-4 wk until revaccination 12 wk old once every 3 yr considered protective Rhinotracheitis virus Administer 6-8 One dose One year booster Core. Not for pregnant (MLV), parenteral, wk of age, after primary queens intranasal then every vaccines, then 3-4 wk until revaccination 12 wk old once every 3 yr considered protective  CHAPTER 23 Preventive Medicine 335 Table 23-1 Canine and Feline Vaccinations—cont’d Initial Kitty Initial Adult Cat Feline Vaccine Vaccination Vaccination Revaccination Comments Rhinotracheitis virus Administer Two doses 3-4 wk One year booster af- Core (killed), parenteral 8-10 wk of apart ter primary vac- age, repeat cines, then revac- in 3-4 wk cination once every 3 yr consid- ered protective Calicivirus (MLV, killed) Administer 6-8 Two doses 3-4 wk One year booster af- Core. MLV not for wk of age, apart ter primary vac- pregnant queens then every cines, then revac- 3-4 wk until cination once 12 wk old every 3 yr consid- ered protective Calicivirus (MLV), intra- Administer One dose One year booster af- Core. MLV not for nasal 6-8 wk of age, ter primary vac- pregnant queens then every cines, then revac- 3-4 wk until cination once 12 wk old every 3 yr consid- ered protective Rabies 1 yr (killed), Administer as One dose Annual update Core parenteral early as 12 wk of age Rabies (recombinant), Administer as One dose Annual update Core parenteral early as 8 wk of age Rabies 3-yr (killed), Administer as One dose Revaccination one Core. State, local or pro- parenteral early as 12 year following in- vincial laws apply wk of age itial vaccine, booster vaccines administered every 3 yr Leukemia virus (live ca- Administer at Two doses 3 wk Annual update Core, noncore narypox vector), 9 wk of age, apart parenteral repeat in 3 wk Leukemia virus (killed), Administer 8-10 Two doses 3-4 wk Annual update Core, noncore parenteral wk of age, re- apart peat in 3-4 wk Chlamydia psittaci (MLV, Administer 6-8 Two doses 3-4 wk Annual update Noncore killed), parenteral wk of age, apart then every 3-4 wk until 12 wk old Feline infectious Not approved Two doses 3-4 wk Annual update Not recommended. peritonitis (MLV), for cats less apart to cats Efficacy of vaccine intranasal than 16 wk 16 wk of age or controversial older Microsporum canis Not approved First dose subcuta- Not stipulated Not recommended (killed), parenteral for cats less neously 16 wk than 16 wk or greater, second dose 12-16 days afterwards, third dose 26-30 days after second dose Continued 336 SECTION II SMALL ANIMAL Table 23-1 Canine and Feline Vaccinations—cont’d Initial Kitty Initial Adult Cat Feline Vaccine Vaccination Vaccination Revaccination Comments Bordetella bronchiseptica One dose to cats One dose Not stipulated Not recommended. Pri- (MLV), intranasal 4 wk or older marily problem of very young kittens Giardia lamblia (killed), Administer 8 wk Two doses 3-4 wk Annual update Not recommended. Same parenteral of age, repeat apart limitations as those in 3-4 wk listed for canine giardiasis Feline immunodeficiency Administer 8 wk Three doses 2-3 Annual update Not recommended. Vacci- virus (killed), of age, then wk apart nation of FIV (-) cats parenteral every 2-3 wk renders current availa- for an addi- ble serologic tests tional 2 doses positive MLV, Modified live virus. 2. Diethylcarbamazine (DEC) works up to I. Revolution (moxidectin) exposure 48 hours previously 1. Topical product (may be used for food trial) B. General information about preventatives 2. Kills L3, early L4, and some L1 1. Ivermectin and milbemycin are macrolide 3. Dogs: Also treats for sarcoptes, otodectes, antibiotics American dog tick and fleas 2. Avoid ivermectin with collies, collie mixes, Old 4. Kills fleas by attacking the central nervous English sheepdogs system (CNS) C. Filaribits (DEC) 5. Sizes for dog: 0-5 lb, 5-10 lb, 10.1-20 lb, 20.1-40 lb, 1. Must be given daily 40.1-80 lb, 80.1-100 lb 2. Beef flavored (not for food trial) 6. Cats: Also treats for otodectes, fleas, round- 3. Must not give to a microfilaria-positive dog; worms, and hookworms may cause anaphylaxis 7. Sizes for cat: 0-5 lb, 5-15 lb 4. Will be available until stock depleted J. ProHeart 6/12 (moxidectin) D. Filaribits Plus (DEC, oxybendazole) 1. Taken off the U.S. market 1. Help control roundworm, hookworm, and 2. Injectable (may be used with food trial) whipworm infections 3. Also treats all stages of hookworm disease 2. No longer available 4. Two types available, lasting through a E. Heartgard (ivermectin) time release mechanism for 6 or 1. Nonflavored form may be used with food trials 12 months 2. Microfilaricidal at 5 the dose K. Heartgard Chewable for cats (ivermectin) 3. Kills L3, early L4, and some L1 at the preventa- 1. Flavored (not for food trial) tive dose 2. Also controls hookworm infestation 4. Sizes: 0-25 lb, 26-50 lb, 51-100 lb 3. Sizes: 55 mcg 0-5 lb, 165 mcg 5-15 lb F. Heartgard Plus (ivermectin, pyrantel) L. Ivomec (liquid ivermectin): Off label use in small 1. Beef flavored (not for food trial) animal except for the ferret 2. Help control roundworm, hookworm infections M. Iverheart (ivermectin, pyrantel): Generic 3. Sizes: 0-25 lb, 26-50 lb, 51-100 lb Heartgard Plus G. Interceptor (milbemycin oxime) N. Tri-Heart (ivermectin, pyrantel): Generic 1. Beef flavored (not for food trial) Heartgard Plus 2. Microfilaricidal at preventative dose O. Ivomec (liquid ivermectin) 3. May be used in cats (same packaging) 1. Off-label use in small animal except for the ferret 4. Kills L3, early L4, and L1 2. Ferret: Combine 0.1 mL of Ivomec with 5. Sizes canine: 2.3 mg 0-10 lb, 5.75 mg 11-25 lb, 0.9 mL propylene glycol; administer 0.1 mL 11.5 mg 26-50 lb, 23 mg 51-100 lb for each ferret monthly for heartworm 6. Sizes feline: 5.75 mg 1.5-6 lb, 11.5 mg 6.1-12 lb, protection 23 mg 12.1-25 lb II. Flea preventatives H. Sentinel (milbemycin, lufenuron) A. Frontline Top Spot (fipronil) 1. Combination product of Interceptor and 1. Topical application to skin in one location Program (lufenuron) 2. Waterproof 2. Lufenuron is a chitin inhibitor, thus not 3. Collects in oils of the skin and hair follicles, allowing flea eggs to hatch properly continues to be released onto skin and coat 3. Beef flavored (not for food trial) providing long-lasting activity 4. Sizes: 0-10 lb, 11-25 lb, 26-50 lb, 51-100 lb 4. Fipronil attacks the flea’s CNS  CHAPTER 23 Preventive Medicine 337 Table 23-2 Heartworm and Flea Preventives Product (Age Approved Round- Hook- Whip- Ear for Use) Heartworm Fleas Ticks worms* worms* worms* Mites Sarcoptes Mosquitoes Canine Filaribits x Canine Filaribits x x x x Plus Canine Heartgard x (6 wk) Canine Heartgard x x x Plus (6 wk) Canine x x x x Interceptor (4 wk) Canine Sentinel x x x x x (4 wk) Canine Revolu- x x x x x tion (6 wk) Canine Iverheart x x x (6 wk) Canine Tri-Heart x x x Plus(6 wk) Heartgard for x x Cats (6 wk) Feline Interceptor x x x (6 wk) Feline Revolution x x x x x x (8 wk) Canine Frontline x x Top Spot (10 wk) Feline Frontline x x Top Spot (8 wk) Canine, Feline x x Frontline Plus (8 wk) Advantage x (7 wk dog, 8 wk cat) Canine Advantix x x x Program x (4 wk dog, 6 wk cat) Capstar x (4 wk) *These products help control infections with these parasites. 5. Absorbed externally in the sebaceous glands B. Frontline Plus (fipronil, methoprene) surrounding the hair follicles 1. Treats all life stages of the flea 6. Treat for adult fleas, ticks, and chewing lice 2. Methoprene is an insect growth regulator 7. May be used on breeding, pregnant, or 3. Same factors for Frontline Top Spot apply, lactating bitches or queens except may apply on dogs and cats as early as 8. Dog: Apply at 10 weeks of age; works 8 weeks of age against fleas for up to 90 days, ticks C. Advantage (imidacloprid) 30 days 1. Water resistant 9. Cat: Apply at 12 weeks of age; works against 2. Flea preventative only fleas for up to 6 weeks, ticks 30 days 3. Topical application to skin in one location on 10. Do not use on rabbits the cat or a dog weighing 20 lb or less 338 SECTION II SMALL ANIMAL 4. Animals larger than 20 lb: Evenly applied to 4. Greater overall sensitivity than microfilaria three or four sites on the top of the back from tests, especially with monthly products killing the shoulder to the base of the tail or decreasing total numbers of circulating 5. Imidacloprid attacks the flea’s CNS microfilaria 6. Absorbed externally in the sebaceous glands 5. Immunoassays detect circulating heartworm surrounding the hair follicles antigen from adult female reproductive 7. Do not treat more than once weekly tract 8. May be applied as early as 8 weeks of age in 6. Consistently detect at least three adult female both dogs and cats worms D. Advantix (imidacloprid, pyrethrin) 7. Weak positive test results may be rechecked 1. Water resistant 8. Should test for microfilaria to validate heart- 2. Flea and tick adulticide, mosquito repellant worm positive status; indicates affected animal 3. Only for use in dogs, toxic to cats reservoir E. Program (lufenuron) D. Microfilaria testing 1. Inhibits development of chitin, main compo- 1. Direct smear assessing fresh blood for nent of flea’s exoskeleton movement 2. Does not kill adult fleas 2. Movement beneath buffy coat in spun 3. Comes in flavor tabs for dogs and cats, suspen- hematocrit tube sion for cats, 6-month subcutaneous injectable 3. Concentration techniques: Millipore filtration for cats test, modified Knott test 4. Is approved for pregnant or nursing dogs 4. Circulating microfilaria found less than 20% of and cats the time in cats; if microfilaria present in the F. Capstar (nitenpyram) cat, will only last in circulation for up to 1. Kills adult fleas by attacking the CNS 1 month 2. Can dose as often as once daily E. Antibody testing (Table 23-3) 3. Begins working within 30 minutes 1. Detect both male and female L4 larval stage 4. Application lasts one day 2. Antibody testing only available for cats 5. Safe for pregnant or lactating bitches and 3. Indicates exposure, current or past queens 4. Does not indicate whether L4 will develop into 6. May be used with other products, including heartworm infection heartworm preventatives, corticosteroids, II. Diagnostic workup for heartworm disease: Minimum antibiotics, vaccines, deworming medica- database tions, shampoos, and other flea products A. Packed cell volume (PCV)/ total solids (TS) 7. Does not have an effect on fleas in pet’s 1. PCV of 30% or less is cutoff for classifying as environment class 2 8. Administer once weekly until fleas are no 2. Anemia may be absent, mild, or moderate, longer observed depending on chronicity as well as severity of 9. For severe infestation, administer twice disease weekly until fleas no longer observed B. Chemistry profile 10. Do not administer to dogs or cats weighing 1. Azotemia may occur in dogs with complicated less than 2 lb infections 11. Sizes canine: 11.4 mg 2-25 lb, 57 mg 25.1-125 lb a. Prerenal azotemia may be due to dehydra- 12. Sizes feline: 11.4 mg 2-25 lb tion or right-sided congestive heart failure (CHF) b. Primary azotemia may result from glomeru- HEARTWORM DISEASE lopathies, including immune complex dis- (DIROFILARIA IMMITIS) ease and amyloidosis I. Diagnostic testing 2. Increased serum hepatic enzyme levels may A. Heartworm disease has been documented in all occur 50 United States 3. Hypoalbuminemia occurs in some dogs with B. The American Heartworm Society (AHS) recom- severe infections and hyperglobulinemia, mends yearly heartworm testing even if preventa- which is common in dogs and cats with tive is given year round if there is any possibility chronic heartworm disease of the owner missing one dose C. Urinalysis C. AHS currently recommends that adult heartworm 1. Proteinuria may occur due to antigen-antibody antigen tests be used as the primary method of complex deposition screening 2. In absence of hypoalbuminemia, most cases 1. Enzyme-linked immunosrobent assay and of proteinuria resolve following heartworm immunochromatographic test systems treatment available for detecting circulating heartworm D. Thoracic radiographs (Table 23-4) antigen 1. Caudal lobar arteries most severely diseased; 2. Improved accuracy of test kits diameters should typically not exceed that of 3. Simplicity of use the ninth rib  CHAPTER 23 Preventive Medicine 339 Table 23-3 Differences between Heartworm Infection in Dogs and Cats Differences Dog Cat Parasite Dirofilaria immitis Dirofilaria immitis Susceptibility to infection Very high, virtually 100% 61%-90% exposed become infected Time of development from L3 to L6 6 mo 7-8 mo Average number of adult worms 20-30 1-3 Microfilaria present 80%-90% 20%, last approximately 1 mo in circulation Ectopic infections Uncommon Common Testing Occult heartworm test, millipore Antibody testing, occult heartworm filtration test, modified Knott’s test test Longevity of infection 5-7 yr 2-3 yr Clinical signs Asymptomatic, coughing, exercise Asymptomatic, coughing, signs of intolerance, dyspnea, signs of congestive heart failure, vomiting, congestive heart failure diarrhea, neurologic signs, sudden death Immune response Spontaneously resolve infection Organ of greatest pathology Lungs and heart Lungs Treatment options See treatment section in text See treatment section in text Table 23-4 Criteria for Heartworm Infection Classification Clinicopathologic Class Clinical Signs Radiographic Signs Abnormalities 1 (Mild) None; or occasional cough, None None fatigue on exercise, or mild loss of condition 2 (Moderate) None; or occasional cough, Right ventricular enlargement  Mild anemia (PCV, fatigue on exercise, or and/or pulmonary artery 20% to 30%); ± mild to moderate loss enlargement;  perivascu- proteinuria (2 on of condition lar and mixed alveolar or dipstick) interstitial opacities 3 (Severe) General loss of condition Right ventricular  atrial en-  Anemia (PCV 30%), or cachexia; fatigue largement; moderate to ± proteinuria (2 on exercise or mild severe pulmonary artery on dipstick) activity; occasional enlargement; perivascular or persistent cough;  or diffuse mixed alveolar/ dyspnea;  right-sided interstitial opacities;  evi- heart failure dence of thromboembolism 4 (Very severe) Caval syndrome PCV, Packed cell volume. 2. Tortuosity of pruning of arteries III. Pathophysiology of heartworm disease 3. Cranial lobar arteries should typically not A. Heartworm disease is the most common cause exceed proximal portions of the third rib of pulmonary hypertension (cor pulmonale) 4. Parenchymal lung disease results from pulmo- in dogs and is increasingly recognized nary arteriolar thromboembolism with leakage in cats of plasma and inflammatory cells into adjacent B. Adult worms live mainly in the pulmonary tissues arteries. As the worm burden increases, 5. Severity of parenchymal lung disease varies; some worms move into the heart. most prevalent in caudal and intermediate lung May eventually even enter the caudal lobes and surrounding lobar arteries vena cava 340 SECTION II SMALL ANIMAL C. Cycle of endothelial cell and worm interaction 3. Ivermectin (Heartgard) causes changes in pulmonary arteries. Caudal a. Exercise restriction still required and accessory lobar arteries most severely b. Continuous monthly administration of pro- affected phylactic doses highly effective against D. Leads to pulmonary edema late precardiac larva and young adult E. Dead worms incite a more intense host response heartworms F. Worm fragments and thrombi cause embolization c. Adulticide effect will require longer than and worsen pulmonary disease one year, possibly up to 2 years total G. Vessels become tortuous and proximally dilated d. During the course of treatment, the infec- as the increased pulmonary vascular resistance tion persists, disease progresses demands higher perfusion pressures e. Older worms will take longer to die than do H. Leads to right-sided heart disease younger worms I. Chronic hepatic congestion secondary to heart- f. Long-term administration of ivermectin is worm disease can cause permanent liver damage not a substitute for conventional arsenical and cirrhosis. Circulating immune complexes adulticide treatment or possibly microfilarial antigens can produce g. Dogs with chronic mature infections might glomerulonephritis not benefit J. Occasionally, aberrant worms can cause emboliza- B. Microfilaricidals tion of the brain, eye, or other systemic arteries. 1. Ivomec (Ivermectin) May also see allergic pneumonitis or lymphoid a. Give at 4 weeks after adulticide treatment granulomatosis b. Administer in the morning, hospitalize the IV. Treatment of heartworm disease in the dog patient to monitor throughout the day for A. Adulticides signs of vomiting, depression, diarrhea, and 1. Thiacetarsamide sodium (Caparsolate) cardiovascular instability a. Arsenical c. Associated with few complications b. Older version of treatment d. Not recommended for collies or shelties c. Four doses total, one dose administered in- 2. Interceptor (milbemycin oxime) travenously every 12 hours a. Normal preventative dose is a d. Potential tissue slough if leakage outside microfilaricidal of vein; test each time by injection of b. Most potent microfilaricide at the label saline dose; produces the most rapid rate of e. Acute toxicity occurs in 10% to 20% of clearance patients c. Rapid death of large numbers of microfilaria f. Contraindications: Hepatic failure, nephrotic 4 to 8 hours following the first dose; can syndrome, advanced renal failure, right-sided cause systemic side effects such as leth- CHF, and azotemia or any life-threatening argy, inappetence, salivation, pale mucous disorder membranes, and tachycardia 2. Immiticide (melarsomine) 3. Heartgard (ivermectin). Must dose 4 to a. Arsenical 5 higher than preventative dose for b. Less hepatotoxic and improved efficacy microfilaricidal use against both sexes of adult worms C. Follow-up c. Soreness and mild swelling may occur at 1. Perform microfilarial concentration test injection site for a few days, but this can be 3 to 4 weeks following microfilaria minimized by ensuring that the injection is treatment deposited deeply with a needle of appropri- a. If negative, begin heartworm preventative ate length and gauge for the size of the dog immediately d. Exercise restriction is essential for minimiz- b. If positive, repeat treatment for microfilaria, ing cardiopulmonary complications then repeat microfilarial concentration test e. Two treatment options in another 3 weeks (1) Two deep injections administered intra- 2. Testing for adult heartworms through the oc- muscularly (IM), alternating sites, given cult heartworm test should occur 100 days or 24 hours apart 4 months following the end of the last dose of or immiticide administered, regardless of which (2) Give one deep injection IM, wait and protocol was chosen rest dog for 30 days, then give two deep a. If tested prior to 100 days, false-positives IM injections 24 hours apart may occur because of persistent circulating (3) Choice is based on history, physical antigen presence examination, thoracic radiographs, PCV/ b. If positive, decide to repeat adulticide TS, chemistry profile, and urinalysis therapy or wait 6 to 12 months based on (4) The three-injection alternative is the young, female, drug-resistant worms being treatment of choice of the AHS, many present universities, and private practitioners, c. If weakly positive, repeat test in 1 to regardless of the stage of disease 3 months  CHAPTER 23 Preventive Medicine 341 V. Treatment of heartworm disease in the cat Supplemental Reading A. If asymptomatic, do nothing, and begin or continue heartworm preventative 2005 Executive Board of the American Heartworm Society. B. If clinical, treatment based on clinical signs 2005 Guidelines for the Diagnosis, Prevention and exhibiting Management of Heartworm (Dirofilaria immitis) Infection C. Surgical removal: Do not break a worm; may in Dogs. Available online www.heartwormsociety.org. cause acute anaphylactic reaction and death of Report of the American Animal Hospital Association the patient (AAHA) Canine Task Force. 2006 AAHA Canine D. Adulticide therapy: 30% of cats receiving this Vaccination Guidelines. Available at www.aahanet.org/ treatment will have a life-threatening crisis within PublicDocuments/VaccineGuidelines06Revised.pdf. 3 weeks of therapy