To: "FT Rescue" <FTRescue@yahoogroups.com>
From: "E/N Orr" <norinfox@sbcglobal.net>
Date: Wed, 14 Jun 2006 09:10:34 -0500
Subject: [FTRescue] Fw: New Heartworm Information

Re heartworm treatment with adjunct therapy with doxycycline. The more technical part is toward the end.

Erin


-------- Original Message --------

Hi All,

I have just learned some important new information regarding heartworm infection and treatment. This info is very new, which is why I didn't come across it before. Here is a brief explanation. (permission is given to crosspost):

Recent research has led to the discovery of a parasite called Wolbachia that lives symbiotically inside heartworms. Studies
indicate that this parasite contributes to the adverse effects of both heartworm infection and heartworm treatment, including inflammation, embolism and allergic reaction. Treatment with doxycycline for 30 days to kill the Wolbachia parasite weakens the heartworms and makes them unable to reproduce, and greatly reduces the chance of adverse reaction during heartworm treatment.
Any dog that currently has heartworms should be treated with doxycycline for 30 days. If the dog will be treated with Immiticide (fast-kill method), it is best to treat with doxycycline prior to beginning Immiticide treatment, as this should make the treatment much safer, by greatly reducing the potential for embolism and allergic reaction to the death of the worms. If anyone has dogs currently undergoing treatment with Immiticide, I would still give doxycycline, as even concurrent treatment may have some benefit. 
Doxycycline should also be given to dogs that  are being treated  with monthly Heartgard (slow kill method) or any type of alternative heartworm treatment method, as it will weaken the heartworms, prevent them from reproducing, and reduce the chance of adverse effects caused by the heartworm infection itself, and by the worms dying. 
It appears unlikely that the Wolbachia parasite persists in the body after the heartworms have been cleared, though we do not know for certain at this time. To be safe, it may be best to treat any dogs that have completed heartworm treatment in the past with doxycycline for 30 days, to clear any possible remaining Wolbachia. 
I was unable to find any information on the recommended dosage of doxycycline in dogs. Because Wolbachia is a rickettsial organism, similar to those that cause tick disease, it may be advisable to use the higher dose of doxycycline that is recommended for treatment of tick disease, which is 10 mg/kg twice a day. 
Veterinarians may contact Merial, the manufacturer of Immiticide, for more information on this topic, if needed.
 Here is some additional info on the topic that I was able to find, though most of it is highly technical and still in preliminary stages of research: 
http://www.veterinarypartner.com/Content.plx?P=A&A=610
"Wolbachia is a genus of rickettsial organisms (sort of like bacteria, but not exactly). They live inside the adult heartworm. These organisms seem to be protective or beneficial to heartworms and treating the dog with the antibiotic doxycycline seems to sterilize female heartworms (meaning they cannot reproduce). Wolbachia is also thought to be involved in the embolism and shock that result when heartworms die. The role of this organism is still being investigated. If your veterinarian wants to pre-treat your heartworm positive dog with doxycycline, it may be because of concerns regarding this organism. As new information emerges, we will post here."

http://www.vetmed.auburn.edu/~blagbbl/Blagburnheskasymposium.pdf
"Wolbachia are intracellular bacteria that infect numerous species of filarial worms including heartworms. Many contend that these friendly inhabitants (endosymbionts) play a role in the pathogenesis of diseases caused by heartworms and other filarids. Contention is that host immune responses directed at Wolbachia can actually go awry and enhance the disease process in heartworm infections. Some also contend that elimination of Wolbachia spp. from heartworms may affect the survival of adult heartworms and may decrease the host's errant immunologic responses when adult worms are killed or die."

http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2005&PID=10906&O=Generic>
"Dirofilaria immitis [heartworms] the cause of heartworm disease in dogs and cats harbours an endosymbiont intracellular bacteria of the genus Wolbachia (a Rickettsia). Studies performed recently indicate that these bacteria may play an important role in the pathogenesis and immune response to filarial infection (Bandi et al, 2001)." This article goes on to say that Wolbachia may contribute to many of the side effects of heartworm disease, including inflammation, kidney disease, lung problems and allergic reactions.

http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2005&PID=10907&O=Generic
"Furthermore, preliminary data from our laboratory indicates that antibiotic treatment before adulticide therapy in dogs with heartworm disease leads to a decrease in pro-inflammatory cytokines, particularly IL-8."

http://lib.bioinfo.pl/meid:13044
This site has numerous other studies on human treatment, indicating that doxycycline, oxytetracycline (of which doxycycline is a derivative) and rifampicin (sometimes use in conjunction with doxycycline) are all effective against Wolbachia.

http://www.pnas.org/cgi/content/full/94/21/11154
"Bacterial relatives of Wolbachia include a number of agents that have arthropods as vectors and cause serious human diseases such as typhus, scrub typhus, erhlichiosis, and Rocky Mountain spotted fever. Studies of these bacteria require special containment facilities. In contrast, Wolbachia have so far been found only in invertebrates and are not known to cause mammalian disease." 
Mary Straus
Pleasanton, CA
http://www.dogaware.com

***
And I got this in response to my posting the above on my local rescue list:
***
We have been following this protocol for a few months now, after speaking with Dr. Nelson, the Prez of the American Heartworm Society. We are not only giving them the Doxy 30 days in advance (or as much time as possible), but continuing them on the Doxy throughout the treatment. Believe me, there is a marked difference in the health of the dogs. I currently have three high-risk dogs undergoing treatment, and they are showing virtually no adverse side effects from the treatment! It is incredible to think that a parasite such as heartworms, actually have parasites themselves. How wild is that! And to think that those parasites contribute to the adverse reactions, and sometimes death, in heartworm-treated dogs - well, it just boggles the mind!!!
But I am now a huge proponent of the Doxy protocol - we are ordering it by the case!!!
Karen
***
I am currently trying to find out if there are any beneficial effects to giving doxy post hw treatment. I urge everyone to crosspost this info and to also discuss it with your vet if you have a dog that needs to be treated for heartworms. I am sure many vets know about this, but not all. And it never hurts any of us to be further educated on this terrible infection/disease.
Sandy in TX

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