Heartworm Disease PDF - Combined Dogs & Cats

10/17/2022 Heartworm Disease Heartworm Disease Vincent Centonze, DVM Dirofilaria immitis 1 2 Heartworm Disease...

10/17/2022 Heartworm Disease Heartworm Disease Vincent Centonze, DVM Dirofilaria immitis 1 2 Heartworm Disease Heartworm Passed by Mosquitoes Affects Dogs, Cats, Ferrets, Coyotes, Wolves Rarely affects humans! First Described in dogs more than 100 yrs ago First Described in cats in 1920’s 3 4 Aedes albopictus Aedes vexans Heartworm Disease Ochelerotatus canadensis Passed by over 70 species of mosquitoes Ochelerotatus cantator worldwide Ochelerotatus excrucians Malaria passed by only Anopheles Ochelerotatus sollicitans In the eastern U.S., sixteen species of Ochelerotatus sticticus mosquitoes known to pass HW Ochelerotatus stimulans 11 species found in abundance in Florida. Ochelerotatus taeniorhynchus Anopheles bradleyi Anopheles punctipennis Anopheles quadrimaculatus Culex nigripalpus Culex quinquefasciatus Culex salinarius Psorophora ferox 5 6 1  10/17/2022 Heartworm Disease Heartworm Disease 7 8 Heartworm Disease Heartworm Disease Larval Heartworms need a certain Mosquito injects the larval stage L3 into number of consecutive days over 57º the dog F (14º C) to develop in the gut of the mosquito Remain in the subcutaneous connective @ 30 days at 57º F tissue for a while then migrate through the @ 10-14 days at 80º F body 4-6 months and several moltings, they increase in size in the heart as adults 9 10 Heartworm Disease Heartworm Disease Females produce offspring called “Microfilaria” which can be seen in the blood 11 12 2  10/17/2022 Video of Microfilaria in Urine Heartworm Disease “Microfilaria” can never grow up to be adult heartworms without going through a mosquito 13 14 Heartworm Disease Heartworm Cycle mosquito then bites the dog sucks in the microfilaria with the blood allows them to develop to L3 stage, …and the cycle continues… 15 16 Heartworm Disease Heartworm Disease Adult worm life span 5-7 years! In the lungs, heartworms block arteries and cause inflammation Lung hypertension, and back blood up into right side of the heart Right-sided heart failure! 17 18 3  10/17/2022 Heartworm Disease Heartworm Disease Signs Coughing Exercise intolerance Fainting Difficulty breathing Coughing up blood Blood and Protein in urine Anemia 19 20 Heartworm Disease Diagnostic Blood Tests Heartworm Disease Antigen Test – looks for tiny pieces of worms Diagnostics Worms must be adults Worms must be female Antibody Test – looks for antibodies against the worms Exposure Visually observing Microfilaria under the microscope 21 22 Echocardiography Dipetalonema reconditum Worms appear as parallel lines “railroad tracks” in right sided heart chambers Dipetalonema reconditum adults live in the skin D. reconditum microfilaria are transmitted and part of their development occurs in fleas Dogs with D. reconditum test negative for heartworms D. reconditum is an incidental finding in dogs but the microfilaria can be confused with heartworm microfilaria Note that it is starting to be called by a new name Acanthocheilonema reconditum (A. reconditum) 23 24 4  10/17/2022 Distinguishing Dirofilaria immitis with Dipetalonema reconditum microfilaria Dipetalonema reconditum (Acanthocheilonema reconditum) D. reconditum microfilaria number < 100 per ml of blood D. immitis microfilaria usually number in thousands per ml of blood D. reconditum microfilaria have blunt cranial end D. immitis have pointed cranial end Formalin fixed D. reconditum microfilaria have “buttonhook tail” Formalin fixed D. immitis microfilaria have straight tail D. reconditum microfilaria are thinner and shorter than D. immitis microfilaria 25 26 Video of Dipetalonema reconditum microfilaria in blood Heartworm Disease 27 28 Heartworm Disease Prevention Prevent Deposition of L3 by mosquito Numerous products on the market Macrocyclic lactones -- Monthly Ivermectin (Heartgard®, Heartgard Plus®, Iverheart®, Triheart®) Milbemycin oxime (Interceptor®, Sentinel®) Moxidectin (Advantage-Multi®) Selamectin (Revolution®) 29 30 5  10/17/2022 Lots of New “Combo” Products Heartworm Disease Prevention ◼ Diethylcarbamazine – once daily treatment (Filarabits®, Dimmitrol®) 31 32 Heartworm Disease Prevention Preventatives kill L3, L4 stage larva and microfilaria Does NOT immediately kill L5 “teenagers” or adults Has a slow kill for adults Reduces life span from 5-7 years down to 2-4 years 33 34 Heartworm Disease Treatment Heartworm Disease Treatment Injections of arsenic-based drug Immiticide Historically, treatment began immediately (melarsomine hydrochloride) Currently, treatment should be delayed until 3-6 mos of ivermectin-based preventative 30 days of Doxycycline antibiotic Preventative weakens adults to make immiticide treatment more effective 35 36 6  10/17/2022 Heartworm Disease Treatment Dog Shaved on Back for Heartworm Injections Historically, two or three injections based on class of HW disease American HW Society now recommends 3 shots regardless of class First injection on day 1 Second and Third injections 30 days later, 24 hours apart 37 38 Heartworm Disease Treatment Heartworm Disease Treatment Immiticide only kills adults not microfilaria Worms start dying shortly after treatment Historically, injectable ivermectin given 30 Dogs can have a “dying worm crisis” days after treatment to kill microfilaria Can kill dog just as live worms can Currently, routine ivermectin-based preventative to kill microfilaria Steroid anti-inflammatories given Dogs kept calm & stress-free until negative 39 40 Heartworm Disease Treatment Heartworm Disease in Cats Smaller numbers (2-5) worms Retest the dog four months after treatment Hopefully, it will be negative …but NOT necessarily! 41 42 7  10/17/2022 Heartworm Disease in Cats Heartworm Disease in Cats More difficult to diagnose on tests Cats are more resistant Worms have shorter lifespan (2-3 years) You may think this is a good thing…. Cats usually don’t have microfilaria 5-10% of unprotected cats may become infected in an endemic area There is no treatment in cats 43 44 Wrong!!!! Heartworm Disease in Cats Cats get severe lung damage from adults Cats self-eliminate most L5 stage “teenage” worms, before adulthood Damage to lungs from eliminated L5 worms just as bad as damage from adults 45 46 Heartworm Disease in Cats Heartworm Disease in Cats Signs include SUDDEN DEATH! When they do show signs in advance, Coughing usually mimics feline asthma Rapid breathing Heartworm Associated Respiratory Disease Vomiting (HARD) Lethargy Anorexia & weight loss Neurologic signs Heart murmur 47 48 8  10/17/2022 Heartworms in Ferrets Signs Similar to cats Lethargy, chronic cough, dyspnea, shortness of breath when active Rapidly progressive and fatal Cardiomyopathy can cause identical symptoms. 49 50 Heartworms in Ferrets Heartworms in Ferrets Diagnosis Similar to cats Antigen test, as in cats, not 100% accurate in ferrets due to small number and sex of worms Antibody test, as in cats, may be more sensitive than the antigen test, but less specific than antigen test Blood tests can help differentiate cardiomyopathy from HW disease Radiographs (x-rays) and echocardiograms can be useful 51 52 Heartworms in Ferrets Heartworms in Ferrets Prevention Ivermectin tablets -- American Heartworm Society & Merck recommend Heartgard in ferrets 0.5-1 tablet for small dog size Compounded liquid ivermectin liquid formulation of 0.100 mg suspension of Ivomec in propylene glycol (in an amber bottle); 0.1 ml per pound body weight (0.010 mg/lb) Ferrets over six months of age should be tested prior to beginning heartworm prevention. 53 54 9  10/17/2022 Heartworms in Ferrets A pet on heartworm prevention is a happy pet! Treatment Thiacetarsemide 0.12ml/lb via cephalic catheter One dose BID X 2 days (four doses total) Begin prednisone 0.25 mg/lb PO q 24 hrs X 90 days Taper over a two-week period Cage rest throughout treatment period natural instinct to run and play may result in embolism Retest four months post-treatment Antigen tests may remain positive for up to six months 55 56 Questions?????????? 57 10