Case Studies In Small Animal

Cardiovascular Medicine

Home Up Rx Pictures 2nd Treatment

Microfilaricide

Case 27

Presenting Complaint

bulletHeartworm Treatment

Pertinent History

bulletMarso presents to the Cardiology Service for the second step in treatment of his heartworm disease. Last month (11/13/99) Marso was diagnosed with heartworm disease and was given a single IM injection of melarsomine (100mg). He is also microfilaria positive.
bulletThe owners report that Marso was lethargic and anorexic during the week following the injection. He also had intermittent episodes of difficulty breathing. His attitude subsequently improved; he is now breathing without apparent difficulty and his appetite is good. He is being kept indoors only, and the owners are restricting his activity. He has not had any more bleeding from his mouth, and his defecations are normal. The owners report that he still occasionally coughs at home, especially after drinking. He has always done this, and the owners think it is a sequelae of his debarking surgery. 

Physical Examination

bulletGeneral: BARH, Wt=35.2kg, T=102.7, P=104, R=panting (56bpm with mouth closed).
bulletIntegument: Normal
bulletEENT: Normal
bulletMusculoskeletal: BCS=4/9, no gait abnormalities.
bulletCardiovascular: CRT=1sec, MM pink. No murmurs, when Marso begins to pant his heart rate dramatically increases to ~180 bpm, no jugular pulses. Femoral pulses present bilaterally, no deficits.
bulletRespiratory: Dog is breathing deeply.
bulletGastrointestinal: Normal
bulletGenitourinary: Normal
bulletNervous system: NE.
bulletLymph nodes: WNL.

Clinical Diagnoses

bulletHeartworm disease

Plans and Progress Notes

bullet12/16/99: Problem #1: Heartworm disease. S/O: Gave first dose of second stage of adulticide therapy - melarsomine (88mg IM) in the left epaxial musculature along the L4 vertebra at 13:00H. This dose was lower than the dose given one month ago because the dog has lost weight.  A: Adequate recovery following first stage of adulticide therapy. We have most likely killed the male worms at this point; the two injections in the second series will hopefully kill all the remaining worms. Risks associated with melarsomine treatment include direct lung toxicity, GI signs (vomiting), and later, pulmonary thromboembolism secondary to worm dissolution. P: Give second IM injection of melarsomine tomorrow afternoon. Owner intends to pick Marso up on Saturday (12/18/99). 
bullet12/17/99: Problem #1: Heartworm disease. O: Marso's resting respiratory rate ranges from 16-64bpm. His heart rate is within normal limits (80-100bpm), although he does have runs of tachycardia associated with an increase in his respiratory rate (when he begins panting). His temperature has remained within normal limits. He continues to be nervous and refuses to eat. He was given the second dose of melarsomine (88 mg IM) today at 13:00H within the right epaxial musculature at the level of L3. Approximately one hour later, he had a bout of diarrhea. A: The diarrhea may be due to his nervousness, or may be a reaction to the melarsomine. He is doing well otherwise. P: Continue to monitor vital signs.
bullet12/18/99: Problem #1: Heartworm disease. No change in Marso's status. Discharged at 09:30H.

Discharge Instructions

bulletWe have given Marso his two remaining injections of melarsomine in the second step of treatment for his heartworm disease. He received one injection on each side of his back within the muscles. As a result, he may be sore in this area for the next week or so.
bulletAs you know, it is very important that Marso be kept indoors and quiet for the next month. Please do not allow him to rough-house with your other dog and only take him outside on a leash when he needs to go to the bathroom. Keeping him in a separate room or in a crate is ideal. Excitement or exercise can dislodge a large number of dead worms rather than allowing them to slowly decompose, and could cause serious problems, including death.
bulletThere is a possibility that Marso will experience some negative effects from the melarsomine itself and also as the remaining worms in his lungs are killed. Some of the side effects include difficulty breathing, lack of appetite, and gastrointestinal signs such as vomiting or diarrhea.
bulletIf he begins to have difficulty breathing or his respiratory rate at rest is rapid, please take him to your local veterinarian right away. If possible, check the rate of his breathing once daily when he is resting; if it is greater than 40 to 50 breaths per minute, call us or your local veterinarian.
bulletMarso's appetite may also be decreased during the next 7-10 days. If he begins to vomit or has diarrhea, please contact us or your local veterinarian. He may cough up a small amount of blood; if he continuously coughs or coughs up more than just a small amount, again, please contact us or your local veterinarian.
bulletThe treatments he has received do not kill the larvae present in his bloodstream. These are a potential reservoir for infection of mosquitoes, which can then spread the disease to other dogs. He can be treated with a heartworm preventative (Interceptor) in one months' time to kill the circulating larvae. He must be observed at your local veterinarian for the day when he is given the Interceptor to ensure he does not have a bad reaction to the dying larvae. You can get Interceptor from your local veterinarian or from us. Another blood test for presence of microfilariae (larvae) should be run a month after the Interceptor is given.
bulletEither your veterinarian or we can retest Marso in four months to check for any remaining adult heartworms by performing an antigen test. If he is still positive for adult heartworms, he may need another series of melarsomine injections.
bulletThank you for bringing Marso to the VMTH and entrusting his care in us. He is a beautiful boy and has a sweet disposition.

Quiz

Correct Quiz

Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.