Revised December 2011.
It’s been around a long time, and it’s not going to go away. Once considered an exotic or tropical disease, later associated specifically with German Shepherd Dogs but not your little Fifi, Ehrlichiosis is a disease that can range from stubbornly persistent to downright fatal. Actually, we might not be technically correct in calling it a disease—some prefer to call it a syndrome, which means a collection of symptoms, not all present at one time or in one individual.
In what we were taught in high school is the shady area between the Animal Kingdom and the Plant Kingdom, lies a large and varied assortment of organisms that have one figurative foot in each. Analogously, in the gray area between bacteria (simple one-celled “plants”) and viruses there are microorganisms that some would classify in one of those groups or the other, or separately, but act like both in some ways. Whether you identify bacteria as plants and one-celled flagellant microbes like Giardia as animals because the latter are somewhat motile, doesn’t make much more than academic difference, nor does it matter much whether you call Ehrlichia microbes bacteria, rickettsia, or anything else. Rickettsia has been thought of as a separate genus of evil little critters intermediate between bacteria and viruses, but today, most medical references list it as “a bacterium in the Rickettsiaceae family.” The name has nothing to do with the disease of rickets; rather it is named after a pathologist named Ricketts. The bottom line for the average person is that it seems the smaller the organism, the nastier it is likely to be. More people are killed by virus particles than by elephants. Some of the microorganisms are so small, they slip through the most sophisticated filters and barriers.
There are a few rickettsial-like Ehrlichial species, sometimes hard to tell apart, that affect dogs: Ehrlichia canis, E. phagocytophilia, E. ewingii, and E. equi, for examples. Some cause milder symptoms than do others. Each species results in a disease state that may have more than one name, usually based on what it does to the body’s cells, especially blood cells, or its history of discovery. Ehrlichia organisms are “gram-negative,” meaning they can be made visible and identified under the microscope by the way in which they are stained by certain dyes.
The E. canis designation is self-identifying as the species perhaps of greatest importance in dogs, the words canis and canidae referring to the canine. E. equi, associated with the horse, and E. ewingii, named after its discoverer, cause granulocytic Ehrlichiosis, which is not as severe a disease as that as that produced by E. canis, especially in regard to neurological signs. E. platys and others were later added to the list of Ehrlichia species. Another canine-affecting species that has not yet been fully characterized is similar to E. risticii (which causes Potomac horse fever) in its DNA. Other rickettsial diseases include Canine Infectious Cyclic Thrombocytopenia, Rocky Mountain Spotted Fever, Elokomin Fluke Fever, and Salmon Poisoning Disease.
Transmission
Although medication may appear to give a “cure,” there may be many untreated (or even a few treated) dogs that serve as reservoirs for the microbes, and can donate some to subsequently-encountered ticks. The microscopic invaders infect and kill white blood cells: monocytes, neutrophils, lymphocytes, and leukocytes are attacked. The way this happens is that microorganism, like any foreign substance that is recognized by the body’s defense mechanisms, is consumed by the white blood cells in an attempt to isolate and destroy them, but the little devils are too hardy and multiply inside those cells faster than they can be “digested.” Breaking out of the ruptured white cell, the aliens also attack other blood cells and damage their function, frequently leading to anemia and problems in bone marrow (where blood cells are manufactured). It also disrupts the host’s autoimmune system so that the animal starts phagocytizing (consuming) its own red blood cells; with a weakened immune system, the host is then susceptible to many secondary infections and illness symptoms. No vaccine is available.
In the early 1960s, military dogs were found to be contracting Ehrlichiosis in Vietnam (or perhaps being stimulated into the chronic severe phase by repeated exposure to the bacteria and under a great deal of physical and psychological stress). Some returned to the States where the disease was identified, others stayed and perhaps shared the infected ticks with their handlers. The military K-9s were erroneously or unfairly blamed for the appearance of the disease in America and its spread throughout southeast Asia. By the early 1980s, it had spread across nearly the whole U.S., and soon thereafter was to be found wherever the brown dog tick existed, which is almost universal.
At Texas clinics used by GSD breeders, vets such as Harold Krug and Marc Rachovsky have seen so many cases as to become equivalent to Ehrlichiosis specialists. While transmission is primarily via the bite of a tick as intermediate host, it may be possible to spread Ehrlichiosis through blood transfusions, although Dr. Edward Breitschwerdt and colleagues were unable to induce the disease in “clean” or “naïve” dogs that way. According to a few vets I conferred with in the greater Dallas area, where Ehrlichiosis had been rampant for many years, and where probably 80% of imported GSDs had it, it can be transmitted also by saliva, fleas, and maybe mosquitoes and seminal/prostatic fluid. Dr. Ibulaimu Kakoma intimates that Ehrlichiosis may wisely be handled as if it were also a venereal disease, and recommended that infected dogs be kept out of the breeding pool. Certainly, while a couple types of ticks are the most common vectors, it can also be carried by the same tick species that spreads Lyme Disease. If fact, a single tick can infect a dog with two or three diseases at once, the third of these most common diseases being Rocky Mountain Spotted Fever. Since Ehrlichia is so widespread, there may be a chance your vet’s blood donor dogs could be carriers. By the way, many dogs test positive for all three of these tick-spread diseases, and some have also picked up Babesia and Bartonella infections from ticks.
Since ticks are by far the most important means of transmission, you can reduce the odds of contracting Ehrlichiosis by vigorous attempts to control the ticks. Some Ehrlichia species, perhaps all, can affect any number of animals: dogs, horses, cats, goats, rodents, deer, humans, and more. It seems to take a day or two of attachment to the host before efficient transmission of the microorganism is effected. Because cats tend to groom themselves often and thoroughly, there is a decreased opportunity for the disease to bother cats—perhaps we should learn from Kitty.
Zoonoses
A zoonosis is a disease that can be transmitted directly or indirectly from one species to another, and the context is usually one in which we speak of humans getting it from their pets. Often, there is an intermediate host or “carrier” that does not suffer from the disease but that transfers it, sometimes after it undergoes a change in the body of that “middleman.” You are already familiar with the spread of heartworm and tapeworm by mosquitoes and rodents or fleas. Most diseases, such as “the common cold” are not transferable, but there are enough out there to give us concern. One is Ehrlichiosis.
You probably cannot get it directly from your dog, but if a tick feeds on him and then you, you could. The first human case was in Japan in 1954, and it wasn’t until 45 years later that it became serious enough in man for the Center for Disease Control (CDC) to list it as a “reportable disease.” That year (1999) there were over 300 human cases, including several deaths. Besides E. canis, E. chaffeensis and E. phagocytophilia are known to have caused human Ehrlichiosis. In the U.S., the first reported case of E. canis infection in a human was in Arkansas in 1986, where a man who was bitten by ticks showed a dramatic rise in antibody titers. Prior to this, only E. sennetsu was known to affect humans, and then only in Japan, in the case mentioned above, and parts of Southeast Asia. Humans develop the acute phase, but so far it appears Homo sapiens does not get the chronic form; perhaps this is because people tend to aggressively seek remedies during the acute phase, but I believe it is more likely due to a more efficient immune system.
Earliest identified cases of Ehrlichiosis in dogs were mostly found in Africa and Israel. Canine occurrence was first recognized in 1935 in Algeria and later found in horses, cattle, man, and other species. It is surmised that a “species jump” occurred as a result of minor evolution or mutation in order for varieties of Ehrlichia to be able to infect humans. Bacteria do not mutate nearly as fast as the smaller viruses do, but eventually many diseases jump from the original host to humans; examples: AIDS, SARS, Ehrlichiosis, and more. Cattle are subject to at least one variety of Ehrlichia, and ranchers would love to use some of the more potent treatments, but some leave a toxic residue in the meat.
Besides in Texas, where GSDs imported from Germany had been more plentiful at one time, the early heavy pockets of disease were in Northern Georgia, the Carolinas, and other east-coast areas.
Symptoms
Symptoms range from as mild as a little itching, to severe hemorrhage from gums and other tissues. Some dogs appear to develop resistance to it, but in actuality might merely be in the subclinical phase, which can last for years. Some show only occasional, mild signs after an apparent recovery. Variability of symptoms from dog to dog and between species of animals, are part of the reason this disease is so hard to diagnose. In humans, signs can appear from as short as one day after a tick bite, but usually it’s about 12 days when suddenly the person gets one or some of these: muscle ache, chills, nausea, sweating, headache, overall discomfort, abdominal pain, vomiting, diarrhea, problems with blood vessels, seizures, blindness, or even coma. Rarely, there is a rash on the extremities or around the trunk.
Similar symptoms are found in the canine. Cervical pain, bleeding gums, lethargy, muscle atrophy, swollen popliteal lymph glands behind the knees — the list is lengthy and symptoms confusing because so many point to other diseases, too. Incubation in dogs apparently (and incredibly) is at least 3 weeks in dogs, according to most reports, and evidence of platelet destruction might not be discovered until 2 or 3 months after infection. Prophylactic shots may be the best idea, then; besides, the shots are cheaper than the test. Some GSD breeders in northern Texas routinely gave shots to pups at 12 days of age! Many buyers and importers treat dogs even before taking them from the airport. A blood test on a newly imported or purchased dog might not reveal the problems you might face a month later, as you can get a “false negative” test result. Texas A&M’s vet school stopped doing the blood tests years ago, while Auburn in Alabama was still offering a series of 3 tests.
Typically, the disorder first goes through an acute severe stage, then the dog seems to improve (often coincidental with an administration of antibiotics or almost any or no treatment) as if to lull the owner into a false sense of security. This second part of the progression of the syndrome is called the subclinical phase, although lab tests and titers will tell you the danger is still there. Later, in most dogs, symptoms come back with a vengeance in the third, chronic, phase. This severe period can happen years after the first acute phase ends; even without another tick bite, the dog’s immune system may be overwhelmed and it becomes very sick again. Emaciation, lack of coordination, kidney failure, paresis, poor proprioception, and other signs are common in the severe chronic cases.
Nosebleeds are common in the doliocephalic (long-faced) breeds, and even without that sign, the dog’s olfactory powers may suffer. This can be a factor in some GSDs having trouble passing their tracking title exams. It also may play a very important part in lack of interest in breeding, since scent of a bitch approaching ovulation is necessary to stimulate a stud dog. Sterility and reproductive problems are also found in affected dogs, in all three phases.
The immune system has reduced efficacy, which means that more of the affected dog’s blood cells are overwhelmed, and the animal is more susceptible to other diseases. In the autoimmune response, the dog’s body tries to combat the microorganism inside its blood cells, but is tricked into developing antibodies that attack its own platelets as well. Polymyositis, neuro- or poly-myalgia, and other probably-autoimmune responses can be as deadly as the trigger disease itself. German Shepherd Dogs typically have more immune system related disorders than many or most other breeds, and frequently they respond poorly to challenges from organisms such as Ehrlichia. Thus, they often have more severe symptoms than other dogs do, but all breeds are at risk. The Merck Veterinary Manual says, “Dogs with [Ehrlichiosis] often have thrombocytopenia, anemia, leukopenia, hyperglobulinemia, and mononuclear pleocytosis and marked increase in protein on CSF analysis.”
Diagnosis
Diagnosis can be difficult, and often is a process of elimination. Very helpful, though, is a test called IFA, for Indirect Fluorescent Antibody, which can (sometimes) detect antibodies from one to 4 weeks after infection. Antibodies are a class of reaction chemicals produced by the body when a disease antigen or foreign organism or chemical is introduced. A positive test is positive, all right, but a negative test is not always proof that an animal is not infected. The IFA test is often quite variable between labs, technicians, and other factors. We refer to this as a lack of sensitivity and reliability. When it works, a single serum antibody titer is usually sufficient for diagnosis of E. canis.
Treatment
When one drug does not work well, veterinarians have a choice of a few others to try. The usual drug of choice for all forms of Ehrlichiosis is tetracycline, given for a minimum of 2 weeks in acute cases, 1-2 months in chronic cases. Puppies that are still teething are normally given something else, because of the severe discoloration of tooth enamel produced by tetracycline on developing teeth. Treatment of rickettsial myelitis (tissue inflammation) may also be accomplished with doxycycline or chloramphenicol for 2-3 weeks. Because of better intracellular penetration, doxycycline seems to be effective in some cases in which tetracycline fails. Doxycycline has some advantages in administration: dosing only two times a day, and oral doses just about as good as injections, for example. Early treatment is important to successful treatment and the prevention of lasting effects. Treatment with either one might have to be continued for a couple of months to kill the microorganisms; some claim that it takes up to 6 months to kill them and get the lab tests back into normal range. Even then, a dog may be left with permanent damage such as incoordination, muscle atrophy, general poor resistance, inability to regain normal weight, and other neurologic deficits despite treatment.
Two shots of imidocarb dipropionate 2 weeks apart, are variably effective against both Ehrlichiosis and Babesiosis; however, the drug is not approved for use in the USA. A series of 2 to 4 Diamperon shots in 2 or 3 weeks usually (97-100%) seems to result in cure (per Rachovsky). Although Diamperon has not yet been approved for use in dogs in the U.S. but has been used for a long time in Israel, many American vets, beginning in the early 1990s, bought it from there and used it “off-label.”
Some species of Ehrlichia, especially those that produce HGE, human granulocytic Ehrlichia, seem susceptible to other antibiotics like ciprofloxacin, trovafloxacin, and rifampin. Other species resist these drugs but are killed by various drugs. Clients should understand that the vet might have to try one after another until something works, because the identification of Ehrlichia species is not always accurate or easy.
In acute cases, the temperature returns to normal within 24-48 hours after successful treatment, and the dog becomes more active and begins to eat. In chronic cases, the hematologic abnormalities may persist for 3-6 months, although clinical response occurs much sooner. Supportive therapy may help prevent or make wasting and specific organ dysfunction less severe; platelet or whole-blood transfusions may be required when hemorrhage is considerable. The E. canis antibody titer should be measured again within 6 months of illness to confirm a seronegative status, an indication of successful therapy. If serum titers persist, even though at lower levels, another test should be run in 6 months.
Prevention
It is probably impossible to absolutely prevent ticks from biting your dog, but you certainly can reduce the incidence by diligently inspecting your pet after every walk where there is any vegetation at all. Removing ticks by feeling under the coat all over the dog’s body during daily combing, and visually inspecting your own bodies when you bathe, is recommended during at least the heaviest infestation period s of summer and fall. Several years ago in Alabama we had two horrible tick years back-to-back, and beginning treatment of our few dogs consisted of dipping them entirely up to their eyes in a 50-gallon plastic garbage can nearly filled with a potent miticide solution. Quite toxic to the ticks, and supposedly mildly so to us and the dogs, but we had no practical choice. Rubber gloves helped, and we made sure it was at least a week, usually two, between dippings.
Normally, it is sufficient and safer to remove them one at a time with tweezers (fingernails will do in a pinch), depositing the ticks in a saucer or bowl with concentrated dishwash detergent or soap water in it. That’s because the ticks cannot breathe or crawl well through soap the way they can through plain water, and they suffocate in a very short time. It’s also a lot less messy than crushing them between rocks and risking the spread of their eggs. Be sure you grasp them at the dog’s skin, to get all or most of the mouth and head, even though you’ll probably pull off a little piece of the dog’s epidermis with it.
Treating the premises may be of some value if you only have a small back yard, but is not feasible if the dog has access to woods, tall grass, and bushes off your own property. Wildlife may be hard to control, too, although some limited success in preventing as much Lyme disease in New England has been had by soaking cotton balls in tick killers, and leaving this nice nesting material in tubes where mice can find it and carry it to their boudoirs. The reason this works is that the tick goes through a few different phases in its life cycle. After engorging on a dog’s blood, for example, it will lay eggs which later hatch into larvae which feed on small mammals and birds, Some varieties then drop off and molt into nymphs, and lie dormant until the next spring when again they find the blood wagons in the form of rodents, rabbits, birds, etc. In that fall, they molt again into larger adults, and go after larger game such as deer, dogs, and you. If control agencies can make mouse nests comfy for the mice but deadly for the ticks, they can interrupt a year’s worth of tick development this way. There are no Ehrlichiae in the eggs, but larva, nymph, and adult can all carry the germ from stage to stage to host.
