Nelson’s Last Hurrah (for a while) and Some Edumacation

This morning has been looming for about a week in my mind; it’s time for Nelson’s heartworm treatment. For those of you who have never had a pet with heartworm, a.) thank you for using preventative (or lucky you for living a place with no mosquitoes), and b.) I’d like to give a bit of insight into the disease and treatment. I’ll try to keep the “sciency” terms to a minimum.
Heartworm disease in dogs is spread when a mosquito bites a dog (or relative thereof) with adult female worms in its system, it sucks up the baby worms, called microfilaria, which mature into larvae (a.k.a. infectious buggers) over the next 10-14 days. When our mortal enemy the mosquito then bites another animal, say your dog, it deposits the larvae and they enter the bloodstream through the bite wound. Without the protection of that monthly treat, the larvae mature into adult worms over the next 6 months or so, and begin to reproduce and clog up the works in the process. Heartworms can live in dogs for 5-7 years and in cats for 2-3 years, and each mosquito season can bring in new larvae. Left untreated, the worms cause lung disease, heart failure, and associated maladies including death. Even after treatment damage to the heart and lungs can remain.

I hope you’re all sufficiently educated on the disease basics (and maybe a little scared?). If you’d like more information, check out the American Heartworm Society’s website. Treatment for heartworms consists of a month of doxycycline, an antibiotic that kills a bacteria-like organism called Wolbachia living in heartworms, which plays roles in worm fertility and larvae development.¹ To kill the adult worms, dogs are given injections of melarsomine dihydrochloride (trade name immiticide) deep into the muscles in the lower back, after which the adult worms begin to break down. For 4 weeks after injection, exercise has to be strictly limited, because bits of worm block vessels and can lead to death or other severe heart complications.
So today we walked through campus and enjoyed the sunrise for a bit. Nelson will be back with us tomorrow, but Galen and I will miss him in the meantime.


(1) Frank, K.; Heald, R. D. Compend Contin Educ Vet 2010, 32 (4), E4.

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