Author: Karen L. McGlothlin, DVM, PhD
Veterinarian: Dr. McGlothlin
Patient: Beau Barringer
Breed: Pitbull Mix
Age: 4-5 years old (estimated)
Background: Life changed for good for a stray dog who appeared to have led a tough life and hadn’t received proper veterinary care on August 29, 2019. That was the afternoon that the Barringer family witnessed him being pushed out of a truck on the dead-end road in front of their home. Although it was obvious that this boy had endured a mountain of neglect, the stray was very friendly and seemed desperate for affection and attention. The Barringers immediately arranged for a visit to Lawndale Veterinary Hospital to see what needed to be done to help and decided to name this new member of their family Beau.
At his initial visit, Beau was in tough shape. He was very thin, his teeth were severely worn down from chewing, his hair coat was very dull, and he was infested with fleas. In addition, Beau’s abdomen was a bit distended, he was putting a lot of effort into breathing, and wheezes could be heard when his chest was auscultated. Multiple diagnostic tests, including bloodwork, fecal evaluation, 4DX testing (a test that checks for heartworms and tick-borne diseases), and chest radiographs, were conducted and Beau was found to have several problems. His initial list was extensive: heartworm positive (with large numbers of heartworm larvae, or microfilariae, visible under a microscope), Lyme disease positive, conjunctivitis (inflammation of the conjunctiva – a thin, delicate membrane that covers the globe of the eye and lines the eyelid), flea infestation, and whipworm infestation.
Beau was immediately given a general dewormer, a flea/tick preventative, and an antibiotic eye drops for his conjunctivitis. In addition, Beau was started on Heartgard Plus (an ivermectin-based heartworm preventative), doxycycline (an antibiotic), and prednisone (a steroid), to initiate his battle against heartworms.
Heartworm Treatment: Beau remained on Heartgard Plus and was given courses of doxycycline and prednisone regularly. Since he was not in terribly good condition at the time of his first visit, the plan was to give time for Beau to improve and, hopefully, allow for some of the adults in his body to die on their own. By doing this, when the time came for adulticide treatment, there would be fewer live adults present in Beau’s heart and lungs, likely reducing the risks of harmful side effects, such as severe adverse reaction to the adulticide or pulmonary embolism secondary to death of the adult worms. It took a bit of time for Beau to put on some weight, regain strength and improve his health enough for us to be comfortable putting him through the rigors of adulticide therapy.
Prior to receiving this treatment, Beau was brought in for two rounds of thoracic (chest) radiographs and multiple rounds of bloodwork to make sure that he could withstand the process. Beau did great and by the beginning of March, 2020, we felt confident that he could tolerate the first injection of melarsomine dihydrochloride, the only FDA-approved drug used to kill adult heartworms. Melarsomine dihydrochloride (which is known by the trade names Immiticide and Diroban) is an arsenical compound and, while there are some risks involved in receiving this drug, the risks of not treating heartworm infection are far more substantial. The lifespan of an adult heartworm has been determined to be 5-7 years and an adult female heartworm can reach 10-12 inches in length, while adult males may reach 4-6 inches in length. Even a small number of worms occupying space in the heart and lungs for that length of time can cause considerable permanent damage.
Update: Beau went through the three-injection protocol, which is the protocol recommended by the American Heartworm Society. In early March, Beau was given an injection of melarsomine hydrochloride deep in the epaxial muscles on the left side of his lower back. The injection itself is uncomfortable and can result in soreness for the dog for the next few days after injection. Beau tolerated his injection well and did not experience any adverse effects or injection site reactions.
Beau returned in early April for his second adulticide treatment – just as this blog entry was going to press, in fact. This time, melarsomine was injected first into the deep epaxial muscles on the right side of his lower back. Twenty-four hours later, a second melarsomine injection was administered into the deep epaxial muscles on the left side. The administration of two injections, 24 hours apart, has been shown to have a synergistic effect in killing of the remaining adult worms.
Through his whole experience, Beau has remained on a monthly heartworm preventative. We expect that Beau will do well over the next 30 days and we plan to see him back again in early May to check his blood for any evidence of microfilariae (larval heartworms).
April is National Heartworm Awareness Month and we are so happy to have helped Beau become healthier and go through the process of adulticide treatment for his heartworms. Please do your pets a favor and keep them on heartworm preventatives all year long. You may recall our previous blog post on why it is important to do this – heartworms are spread through mosquito bites and our climate is so mild that they are active all year. Heartworm adulticide treatment is risky and it is expensive – it has been estimated that the cost of adulticide therapy is equivalent to the cost of 7 YEARS worth of heartworm preventative products!