If you have been searching online for information about heartworm treatment, you will probably already have come across a number of sites urging you not to poison your dog with chemical preventatives or treat him for infection with adult worms with Immiticide (Melarsomine).
If this is the case, you may be confused about what you should be doing to protect your dog or treat him if he has become infected. Many of these sites advocating natural or herbal remedies for the prevention and treatment of the disease are giving out messages completely opposite to what the American Heartworm Society (AHS) advises.
Frankly, I know who I would rather trust. The AHS, which has done so much to improve the treatment and prognosis for afflicted animals and to raise public awareness of approved heartworm prevention treatments and care.
The AHS are uncompromising in what they say about natural and herbal protections and treatments:
“No “natural” or herbal therapies that have been shown to be safe and effective treatment for heartworm disease.”
By the way, if you are looking at sites promoting alternative, natural or herbal remedies, you should also find a clear disclaimer statement, advising you that the products they are recommending are not approved or authorised by the FDA for the prevention or treatment of heartworm – this in itself, should start some warning bells ringing for you – and if they are not publishing the disclaimer, they could be in big trouble!
Not All Dogs Can Be Treated With Immiticide
Having said all that, however, the AHS guidelines also clearly show that not all dogs affected by the disease are suitable candidates for treatment with Immiticide to kill the adult worms – even though this drug is the only one which has approval from the FDA for this purpose.
The AHS website does advise that for dogs not suitable for Immiticide treatment, (or during a shortage of the drug which has happened several times in the past), continuous, year round heartworm treatments with a once a month dose of a preventative medication (either ivermectin, moxidectin or selamectin) can be used to clear adult worms.
There are some drawbacks with this method and it is not a generally regarded as a substitute for the normal Immiticide treatment.
Firstly, whilst these preventive medications will shorten the life of the immature worms as well as adult worms, the more mature the worms are when the first get exposed to the preventives, the longer it takes to kill them. This means that although the monthly preventive will also eventually kill the adults as well, it can longer than 24 months for your dog to be free of infection and in all this time, the living worms go on causing damage inside your dog’s arteries and organs.
However, if for some reason the arsenic-based Immiticide is not decided upon for your dog, the long-term preventives treatment if closely monitored could eventually rid your dog of the worms. This method is one which is often adopted by pet shelters and rescue centers for whom the cost of Adulticide treatment is prohibitive (I found an interesting article mentioning heartworm treatments with Ivermectin only on the Veterinary Partner website, you will find the information near the foot of the page you arrive on if you follow the link I have provided).
However, studies indicate that it is NOT suitable for either very active dogs or dogs who are showing symptoms – it is only suitable for dogs who have tested positive but who otherwise appear healthy and well. The preventives are relatively inexpensive although the dog needs to be carefully managed with restricted exercise and regular examinations by the vet to monitor the damage being caused internally by the worms. Another concern raised by the AHS is that there is the potential for the development of drug-resistant strains of these parasites when the preventives are given long-term to those dogs who have tested positive for adult worms.
This is the best explanatory video I have come across about Heartworm – well worth a watch!
Ivermectin and Doxycycline Combination Therapy
Perhaps a better alternative to this long term treatment with preventatives is another protocol reported on the AHS website. This is a combination therapy and consists of Ivermectin together with an antibiotic, Doxycycline. Encouragingly, results suggest that this might be of great benefit in dogs for whom the standard Immiticide protocol for dogs infected with adult worms is not possible. Studies carried out :-
“… reported that ivermectin and doxycycline administered periodically over 36 weeks resulted in a 78% reduction in adult worm numbers.”
The method of treatment is Ivermectin given monthly and then every three months, a course of the antibiotic, Doxycycline (the course lasts four weeks each time). The Doxycycline kills the Wolbachia organisms which live inside the worms (please see the article on this site about treating Wolbachia or check out the section on Wolbachia in this report of a lecture given about Heartworm and Associated Diseases).
Another concern with treating dogs infected by adult worms by the monthly preventative treatment alone, is that until the adults die, they go on producing young. So there is the potential for mosquitoes to take immature larvae to new hosts and increasing the spread of infection.
Adding the Doxycycline therapy to this protocol, has the effect that the immature larvae (microfilariae) that were carried by mosquitoes from a dog treated with this combination method and passed to another host dog were unable to grow into worms capable of reproducing – thus breaking the cycle and allaying the fears for even greater levels of heartworm disease in the dog population.
This also gives the reassurance of avoiding any risk of development of drug resistant strains as mentioned in the preventives treatment above.
Surgical Treatment for the Removal of Adult Worms
For dogs that cannot take Immiticide or for whom it might be too dangerous because they have been found to be carrying large numbers of adult worms, there is a surgical alternative.
This involves removing the worms using special surgical tools passed through the jugular vein in the neck and down into the chambers of the heart and the pulmonary arteries themselves. Large numbers of worms can be removed by this method and although this procedure is not without risk, it does enable Vets to reduce the worm burden significantly enough to enable treatment with drugs for the remaining ones.
In the past surgery has been a ‘last resort’ for dogs exhibiting severe symptoms and for whom no other treatment was possible.
It seems that there are effective and approved alternatives giving more options for owners whose dogs are not good candidates for treatment with Immiticide.