Case 27: Microfilaricide

Case 27 — Microfilaricidal Therapy

Marso presents to the Cardiology Service today for microfilaricide administration. He was diagnosed on 11/13/99 with heartworm disease and has undergone three IM injections of melarsomine 100 mg (11/13/99) and 88 mg (12/16/99, 12/17/99). His first injection was followed by lethargy, anorexia and difficulty breathing.
The owners report that Marso has had a healthy appetite since returning home from his last visit. There has been no dyspnea, sneezing, vomiting or diarrhea. Marso does still cough following eating, drinking, or when nervous, probably as a sequela of debarking surgery. He is kept indoors except when allowed out in the yard for defecation/urination.

General: BARH, nervous. BCS 5/9. T = 100.5°F; P = 120; R = panting.
Integument: Two shaved areas over dorsum.
EENT: Normal.
Musculoskeletal: Symmetrical muscling. No gait abnormalities noted.
Cardiovascular: No murmurs or arrhythmias auscultated. mm = pink, CRT = 1.5 s. Good femoral pulses.
Respiratory: Normal.
GI: Normal.
GU: Normal.
Nervous system: No gross deficits.
Lymph nodes: WNL.

S/O: An Interceptor (milbemycin) tablet for a 51–100 lb dog was administered at 11:15 AM. No tachypnea, dyspnea or tachycardia was noted through the course of the afternoon and into the evening.
A: Microfilaricidal treatment with no complications.
P: Retest for microfilariae in one month and repeat treatment if test is positive. If negative, begin monthly heartworm preventative. Repeat antigen test in three months and if positive, possibly give another course of melarsomine. Recommend Marso be allowed to gradually return to normal activity after several days of rest.

Marso presented to the Cardiology Service for treatment to clear the heartworm larvae (microfilariae) present in his bloodstream. He was given Interceptor (milbemycin) at 11:15 AM and observed through the course of the day for any adverse reactions. None were observed.
Marso will need to be retested for the heartworm larvae (microfilariae) in one month. If he tests positive, today’s treatment will need to be repeated. If he is negative at that time, you can begin to give him a monthly heartworm preventative such as Heartgard or Interceptor.
He will also need to be retested in three months for adult heartworms. If he is positive, he may need another injection of melarsomine.
It is important to keep Marso quiet for the next several days. Over a week, gradually allow him to increase activity and by a week he can go back to a normal lifestyle.
Please observe him for signs of difficulty breathing, such as increased respiratory rate and restlessness. If you notice these signs, please call us or take him to your local veterinarian immediately.
Thank you for bringing Marso to the VMTH. He is a very handsome and sweet dog. Please do not hesitate to contact us if you have any questions or concerns.