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Dr. Jo
Dr. Jo, Dog Veterinarian
Category: Dog Veterinary
Satisfied Customers: 2808
Experience:  DVM from Iowa State University in 1994; actively engaged in private regular and emergency practice since that time.
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I work with a rural shelter - all dogs that come in are heartworm

Customer Question

I work with a rural shelter - all dogs that come in are heartworm positive. We recently had two small dogs that were moderate to heavy. Advantage Multi was applied to both dogs... within two or three days one of the dogs stopped eating/drinking and passing blood in urine. Vet said that his heart valve had burst. The other small dog in foster care appears to be swollen, coughing and sneezing - is the application of the advantage multi or any heart worm preventative the cause of these problems?
Submitted: 2 years ago.
Category: Dog Veterinary
Expert:  Dr. Jo replied 2 years ago.
Hello,I'm Dr. Jo and I'm here to help you with your question about heartworms in these shelter dogs. Bless you for the work you are doing. I understand how frustrating it can be to see these dogs getting so sick and feel helpless to do anything about it. It can be so trying to see them get worse in spite of your best efforts to help. You may join the conversation at any time by typing in what you want to say then clicking REPLY or SEND. That way we can chat back and forth until you're satisfied with the information I've provided.
Expert:  Dr. Jo replied 2 years ago.
Your question was about one small dog appearing to be swollen, coughing and sneezing... is this due to applying Advantage multi or any other heartworm preventive?Most likely, no. This is much more likely to be due to the dog having some kind of illness. Heartworm disease itself can cause coughing, but so can many other infectious and parasitic diseases.
Expert:  Dr. Jo replied 2 years ago.
Shelter medicine provides its own unique set of challenges. So many of the dogs who come in are sick, and so many of the illnesses they have are contagious. That means any dog who comes in with obvious signs of illness needs to be isolated. I apologize if I'm telling you things you already know, but several areas in the country are experiencing outbreaks of a serious form of canine influenza. That's why it's important to take symptoms like this seriously. Again, it's much more likely that this dog is ill from some disease he has, not from the heartworm preventive. Please also do keep in mind that heartworm *prevention* is not heartworm treatment. Heartworm positive dogs require therapy with doxycycline and melarsomine in order to treat their disease. For the most current recommendations on how to treat heartworm disease, please read the guidelines at
Expert:  Dr. Jo replied 2 years ago.
That being said, giving a heartworm positive dog a dose of preventive without also addressing the other aspects of his disease can certainly make him sicker. Please let me know if I've answered your question to your satisfaction. I want to be as helpful as possible. If you are satisfied with the information I've provided, please take a moment to ACCEPT my answer and rate my response. Without your positive feedback the website keeps the entire fee you paid and I receive no compensation, so your rating is important to me. If you are not satisfied, please let me know what else I can do to earn that positive rating. Thank you.
Expert:  Dr. Jo replied 2 years ago.
Here are the heartworm treatment guidelines from the AHS...
The extent of diagnostic testing necessary at this
point will vary depending on the clinical status
of each patient and results of a thorough history,
physical examination, and antigen and microfilaria
tests. Key factors influencing the probability of
post-adulticide thromboembolic complications
and outcome of treatment include activity level
of the dog, including exercise, excitement, and
overheating; the extent of concurrent pulmonary
disease as seen on thoracic radiographs; and
severity of infection (worm burden). There is no test
(or combination of tests) to accurately determine the
number of heartworms present, thus every infected
pet must be managed as though a substantial
heartworm mass is present or a potently violent
individual immune reaction to the dead and dying
worms could occur. There is no set protocol for pretreatment
workup. Adulticide treatments have been
successfully performed in numerous cases without
the benefit of extensive diagnostic testing; it is
probable that treating in the absence of diagnostics,
while not ideal, is better than refusing to perform a
needed treatment.
Treating heartworm infections in asymptomatic
patients or those exhibiting signs of mild disease
usually is not problematic if exercise is curtailed.
Infections associated with moderate or severe
heartworm disease or in patients with concurrent
disease often are challenging. The goals of any
heartworm treatment are to improve the dog’s
clinical condition and to eliminate all life stages
of the heartworms with minimal post-treatment
complications. Dogs exhibiting significant clinical
signs of heartworm disease should be normalized
as much as possible before administering an
adulticide. This may require administration of
glucocorticosteroids, diuretics, vasodilators, positive
inotropic agents, and fluid therapy. A thorough
understanding of the host–parasite relationship is
necessary to effectively manage all cases.
Melarsomine dihydrochloride is the only adulticidal
drug approved by the FDA for heartworm treatment.
The AHS recommends the three-dose protocol, one
deep intramuscular (IM) injection into the belly of the
epaxial lumbar muscles (between L3 and L5) of 2.5
mg/kg body weight followed at least 1 month later
by two IM injections of the same dose 24 hours apart
in all cases (with the exception of caval syndrome)
due to the increased safety and efficacy compared
with the two-dose regimen.
Exercise restriction during the recovery period
is ESSENTIAL for minimizing cardiopulmonary
complications. As worms die as a result of adulticidal
treatment, they decompose and worm fragments
lodge in the distal pulmonary arteries and capillary
beds in the caudal lung lobes blocking blood flow
and causing thromboembolism. Increased activity or
2014 Canine Heartworm Guidelines Summary 5
exercise increases the blood flow to these blocked
vessels, causing capillary delamination, rupture, and
subsequent fibrosis, leading to increased pulmonary
vascular resistance, pulmonary thromboembolism,
and potential right-sided heart failure.
Steroids. Diminishing anti-inflammatory doses of
glucocorticosteroids can help to control clinical
signs of pulmonary thromboembolism, which can
be severe after adulticide therapy if infection is
heavy and pulmonary arterial disease is extensive.
Prednisone is routinely dosed at 0.5 mg/kg BID
for the first week and 0.5 mg/kg once daily for the
second week, followed by 0.5 mg/kg every other day
(EOD) for 1 to 2 weeks.
NSAIDs/Aspirin. The empirical use of aspirin for
its antithrombotic effect or to reduce pulmonary
arteritis is not recommended for heartworm-infected
dogs. Convincing evidence of clinical benefit is
lacking and there is some research suggesting that
aspirin may be contraindicated.
Doxycycline. Many filarial nematodes, including D
immitis, harbor obligate, intracellular, gram-negative,
endo-symbiotic bacteria belonging to the genus
Wolbachia (Rickettsiales). Wolbachia have also been
implicated as a component in the pathogenesis of
filarial diseases. Doxycycline reduces Wolbachia
numbers in all stages of heartworms. The AHS
recommends administration of doxycycline at
10 mg/kg twice daily (BID) for 4 weeks before
administration of melarsomine (Table 1). Minocycline
given at the same dosage regimen may be a viable
alternative during periods of doxycycline shortage.
Macrocyclic Lactones. In addition to adult
heartworms, a heartworm-positive dog likely
harbors juvenile stages of heartworms. The efficacy
of melarsomine against juvenile stages (less than
4 months old worms) could present a susceptibility
gap, where some stages of D immitis might not
be susceptible to either the MLs or melarsomine.
The susceptibility gap can be minimized by
administering an ML preventive for 2 months prior
to administering melarsomine. This will reduce new
infections, eliminate existing susceptible larvae,
and allow older worms (between 2 and 4 months
of age) to mature to a point where they would be
more susceptible to melarsomine. Reduction of
the susceptibility gap can also be potentiated with
concurrent use of doxycycline for 30 days, as this
will essentially eliminate all developing larvae during
first 60 days of infection. Exercise restriction should
be rigidly enforced from the time of diagnosis
through the period of treatment and recovery,
with the most extreme restriction recommended
for 4 weeks following each melarsomine
administration. Macrocyclic lactones administered
as a microfilaricide may cause a rapid decrease in
the numbers of microfilariae and should be used
with caution in dogs with high microfilarial counts.
Topical moxidectin is now FDA-approved for use in
heartworm-positive dogs to eliminate microfilariae.
No adverse reactions due to high microfilarial counts
were observed in the laboratory or field studies
conducted for approval of this label claim.
Macrocyclic Lactone/Doxycycline. In cases
where arsenical therapy is not possible or is
contraindicated, the use of a monthly heartworm
preventive along with doxycycline at 10 mg/kg BID
for a 4-week period might be considered. An antigen
test should be performed every 6 months and the
dog not considered cleared until two consecutive
NAD (no antigen detected) heartworm antigen
tests, 6 months apart, have been obtained. If the
dog is still antigen positive after one year, repeat
the doxycycline therapy. Exercise should be rigidly
restricted for the duration of the treatment process.
The AHS recommends a multi-modal approach
to treating heartworms based on the information
presented above and depicted in the following
example management protocol (Table 1). A
retrospective study of clinical cases comparing the
protocol listed in Table 1 with a similar protocol
without doxycycline showed a decrease in
respiratory complications and mortality rates when
doxycycline was included.
Expert:  Dr. Jo replied 2 years ago.

I'm just following up on our conversation about your pet. How is everything going?

Dr. Jo