A note from Lew: I would like to personally give thanks to Gil for writing this very wonderful article on Ehrlichia; its cause, its symptoms, testing for it, and treatment. I know this was very hard for her to write after the loss of her beloved Thunder to this disease, and we can only hope that the information included here will help other dogs and their owners.
Dedicated to Thunder on his birthday. He would have been six on September 2nd.
Proud Owner of a Black, American Bred German Shepherd Dog Bauernhoffen’s Rain Dragon
In the late 1960’s, military dogs in Vietnam began dying in the hundreds from what was then called canine hemorrhagic fever. CHF, the name used by the vets trying to save them, was graphically descriptive of its effect on the dogs whose bone marrow simply stopped making red and white blood cells, but it said nothing about the organism causing it. We know now that the disease that was killing those tracker dogs was Ehrlichiosis canis and it is carried by ticks.
Ehrlichiosis spread rapidly after ‘Nam. Unlike Lyme disease, which is primarily restricted to a fairly small area of North America and is crippling but seldom fatal, Ehrlichosis is a threat to dogs over a vast geographic area; it has stricken dogs in every one of The United States and on nearly every continent, and it is always fatal if a diagnosis is not gotten in time for the damage it can do to be reversed. It can silently undermine the health of its host for years until stress or some other factor brings it to light, then the dog can die with a suddenness shocking to the grieving owner who may never have realized anything was wrong. Perhaps for that reason, it is practically unknown among dog owners and the level of knowledge about it among veterinarians is abysmal.
WHAT IS IT?
Ehrlichia are parasitic organisms which are something like a virus but are classed with bacteria. They attack the bone marrow, crippling its ability to make the white blood cells (leukocytes) which are an important component of the immune system.
“Once a human or animal is stricken with Ehrlichiosis, white cells die off faster than the bone marrow can replace them. These dead cells migrate primarily to the spleen which enlarges as a result. Frantically, the bone marrow works to form new, healthy cells. In its haste, it sends out immature cells which do not work efficiently. Quite often these immature cells are almost indistinguishable from those seen in leukemia patients. Advanced Ehrlichiosis is, in fact, often misdiagnosed as leukemia or lymphosarcoma.”
Since that was written, indications have grown stronger that Ehrlichiosis either causes cancer or sets up the conditions for cancer to develop. It has been suggested that dogs ostensibly cured of it should be tested for cancer four years after titering clear as so many seem to develop cancer of one form or another in that time frame. This is no big surprise to those of us who have seen our dogs come down with serious illnesses after – or during – their infection with Ehrlichiosis since, with an immune system that is essentially out of commission, the dog is defenseless.
Ehrlichiosis is transmitted by the nymph and adult of the brown dog tick, rhipicephalus sanguineus, and the adult deer tick, dermacentor variabilis. Once an infected tick has attached and begun feeding, the disease is pumped into the dog with the tick’s saliva. Saliva keeps the blood from coagulating so the flow of food for the tick is constant and there is some conjecture that tick saliva contains a substance which prevents the immune system from recognizing an invader soon enough to ward it off. At any rate, the deadly inoculation continues until the tick is sated and detaches. Transmission of Erhlichiosis takes from 24 to 72 hours, though on rare occasions it has happened in less than twelve.
One strain of this difficult and hard to pin down disease is not carried by ticks. E. risticii, which has been renamed neorickettsia risticii to reflect its close relationship to the organism that causes the deadly Pacific Salmon Poisoning Disease, is transmitted by the larvae of flukes that live on river snails. Once it infects the dog, however, it acts like every other strain of Ehrlichiosis and requires the same treatment.
Eight to twenty days after infection, in the acute stage of the disease, the dog may show symptoms such as a discharge from the nose or eyes, fever, lethargy, depression, enlarged lymph nodes, disinterest in food or difficulty breathing. Or it may not. The acute stage is short, about four weeks at the outside, and many people never notice anything to alarm them. Unfortunately, this is the stage at which it is most easily cured.
The disease then passes into the sub clinical stage, a term that simply means no symptoms are evident and it may stay in this stage for up to five years while the immune system is steadily undermined. Cure is not as easy but still possible for most dogs at this point.
When Ehrlichiosis becomes chronic, damage is usually extensive and curing a dog of it is difficult. Dogs may begin to bleed from the nose, they may develop edema (swelling), blood disorders such as leukopenia (an abnormal decrease in white blood cells), thrombocytopenia (a decrease in the number of platelets in the blood which can lead to increased bleeding as the blood loses the ability to clot) and abnormally high levels of antibodies in the blood. With the immune system effectively destroyed, almost anything from vague symptoms that go nowhere to kidney failure, cancer and inflammation of the brain can be the result. German Shepherd Dogs are hit particularly hard and in the late chronic stage may develop fatal hemorrhaging.
Cross infections with other strains of Ehrlichiosis or other TBDs are common.
There are various tests that can be done to detect Ehrlichiosis. The IFA, or Indirect Fluorescent Antibody test, looks for the actual organisms in the blood. The PCR, or Polymerase Chain Reaction test, looks for DNA evidence of Ehrlichiosis; false positives and negatives are possible with it and it should be run by experts. The western blot is capable of giving further information on specific species.
The Snap3 Dx Test which looks for signs of heartworm, Lyme disease and E. canis can tell you nothing about any strain other than E. canis. If the dog has one of the other forms of Ehrlichiosis, it will not be detected and a negative titer will not mean the dog is not infected with one of the other strains. A positive titer for Ehrlichiosis with this test, however, confirming a diagnosis, can be helpful since the treatment for E. canis will work against any form of the disease.
E. canis, the most common form of the disease, will cross-react with E. chafeensis. Separate tests must be run for the other strains of
Ehrlichiosis: E. platys, ewingii, equi, and risticii.
A negative IFA does not mean that a dog is free of Ehrlichosis. In the acute stage, dogs may test negative because antibodies have not had time to form. In the chronic stage, the immune system may be exhausted and there may no longer be any detectable antibodies.
Diagnosis is not testing alone but the evaluation of the veterinarian; if a negative titer doesn’t make sense in the picture she is seeing, the dog should be put on doxycycline and if it improves, the diagnosis is confirmed.
Misdiagnosis is a huge problem with tick disease because it is so often mistaken for something else entirely and misdiagnosis in this case is more than ordinarily dangerous. If there is the slightest hint that a dog has TBD, it should be treated for that first; if the dog improves, a diagnosis of tick disease is confirmed and any other condition should be treated with that in mind. Things can get sticky if the dog also has a concurrent blood disorder like thrombocytopenia which is treated with an immune suppresser like prednisolone; the vet then has to walk a very fine line in deciding how much to prescribe since steroids can kill a dog with Ehrlichiosis or any other form of TBD. It can, however, be done. Steroids can also allow cross-infection with babesiosis to become active, producing another complication. Anabolic steroids, though not dangerous, have not proven particularly effective since they stimulate the bone marrow and often enough, there is nothing left in the bone marrow to stimulate.
The drug of choice for Ehrlichiosis is doxycycline. The Merck Veterinary Manual recommends giving doxycycline at a dosage of 10 milligrams per kilogram of body weight every day for a period of ten days to two weeks. The vets who deal with tick disease most often, however, have found that a higher dose of twice that amount – 10mg given every 12 hours for six to eight weeks – is more effective at stopping Ehrlichiosis (as well as Rocky Mountain Spotted Fever and Lyme disease) and preventing its recurrence. Their recommendation is still controversial but among most dog owners who have suffered along with their dogs through the ravages of this disease, there is no hesitation about following it. The thinking there is that disease resistance is more likely to build with low doses of antibiotic; hit it hard the first time out.
Outward signs of improvement, if they are going to happen, are almost immediate, and fortunately, doxycycline, a semi-synthetic tetracycline antibiotic, is relatively benign, has few, rare side effects, and can be given with food, making it less likely that the dog will vomit it up. If that should happen, the twice daily dose can be adjusted so that the dog can get it more often in smaller amounts less likely to irritate the stomach. In the event a dog cannot tolerate doxycycline, there are other drugs that can be substituted which vary in their effectiveness and Imizol may be the best of these for all but E. platys.
Imizol (immidocarb diproprionate) is not approved by the FDA for the treatment of Ehrlichiosis and is used off-label but it can be effective in knocking out stubborn cases of the disease. However, it is imperative that the vet read the product label and balance risk against benefit for dogs that have impaired lung, liver or kidney function.
Of the four major tick diseases in The United States, Ehrlichiosis is the most widespread and probably the most dangerous because of it. As noted above, Lyme disease seldom kills but may cripple the dog if not treated. Rocky Mountain Spotted Fever comes on quickly and can kill quickly, infection occurring in as little as six to ten hours after the tick begins feeding; illness may become apparent in as little as two days up to two weeks, though a week is more common. Babesiosis can be fatal but it does not seem to be as prevalent as Ehrlichiosis and so is probably not as great a risk to most dogs. But all should be taken seriously and treated promptly for the health, for the life, of the dog.
Ehrlichiosis, like all tick disease, is a huge and complicated subject; what you have read barely scrapes the surface and if any of the above information is incorrect or out-dated, it is not intentional. Nothing about this disease is easy to be certain about. There is just not enough funding for research and some of what is known about it comes from experience and anecdotal evidence, something which makes it difficult to convince many veterinarians that it is epidemic, that it can cause or appear to be diseases which they think they see, yet which do not respond to the approved treatments for them, or that they should even test for TBD.
Strangely, if tests are run and dogs are found to have Ehrlichiosis, they are then often reluctant to follow the advice of veterinarians experienced in dealing with it and treat it aggressively with doxycycline given at a high dose for a longer period of time than the Merck Veterinary Manual recommends. All that being so, it is almost a necessity for the dog owner to learn as much as she can about Ehrlichiosis and the other forms of TBD, or at least be aware that her dog could become infected and be ready to insist that he be tested and treated aggressively if tick disease is found.
Some excellent sources of information about Ehrlichiosis and other TBDs, given in much more depth, can be found at the links below.
Ehrlichiosis: A Silent and Deadly Killer
Newsday.com: Interview with Susan Netboy and Dr. Ibulaimu Kakoma
Critter Fixer Pet Hospital: ehrlichiosis
Journal of Clinical Microbiology
Tick Borne Ehrlichiae and Rickettsiae of Dogs – updated May 2003
Document No. A0315.0503. Recent Advances in Canine Infectious Diseases: Canine Monocytic Erhlichiosis
Imizol product label