Some tick borne diseases can be found in many parts of the world and others have very limited geographical distribution. Lyme disease, is an example of a tick borne disease that is most prevalent in a fairly limited geographical area. The Ehrlichia family of parasites is found in many areas of the world.
Ehrlichia canis is probably the most widely recognized tick borne disease other than Lyme disease. It is found in many areas of the world and is primarily spread by the brown dog tick. Infection rates are higher in warmer areas, so this disease tends to have a Southern distribution in the U.S. The first signs of infection with E. canis typically occur within 1 to 3 weeks after the organism enters the body. Low grade fever, decreases in platelet counts, weight loss, lymph node enlargement, lessening or lack of appetite and weight loss are the typical clinical signs. This phase of the clinical signs is often missed by pet owners and does not often cause severe enough illness to cause death. The majority of dogs manage to kill the Ehrlichia organisms during this acute phase of the infection and are no longer infected.
Dogs whose immune systems can not totally eliminate the E. canis infection become chronically infected. This group of dogs has a much higher risk of dying from the infection or problems the infection causes, over time. During chronic infections there is often development of a bleeding disorder through signs such as nose bleeds, blood in the stool, bruising of the skin, hemorrhage in an eye or blood in the saliva. Anemia without obvious bleeding occurs in some dogs, leading to very pale gums or eye tissue. Swollen lymph nodes are common in affected dogs. Some dogs develop neurologic signs such as difficulty walking or a head tilt. Kidney failure may occur due to glomerular damage in the kidneys. White blood cell counts may be so depressed that secondary infections occur easily and these may be the reason that the dog is first seen by a veterinarian. Ehrlichiosis is one of the causes of immune mediated hemolytic anemia (IMHA) and this must be kept in mind in areas in which the infection is likely.
Testing for ehrlichiosis is usually done by blood test. A serum sample is tested for the presence of antibodies against E. canis. This means that a positive test can only be used to indicate exposure to the disease. Dogs with positive titers may have cleared the infection themselves, may be in the process of clearing the infection or may be chronically infected. If a titer is measured prior to treatment and then compared with a second titer done two to three weeks later by the same laboratory, a rise in titer is indicative of an active infection being present. Paired titer samples are nice to have but most dogs are going to be better after two to three weeks of treatment and so it not uncommon for veterinarians and veterinary clients to presume treatment was successful based on the response to the treatment.
New DNA tests, polymerase chain reaction (PCR) tests, can indicate the presence of the E. canis organism directly. This is a big advantage when trying to decide if there really is an infection but due to the nature of E. canis infections it is possible to get a negative test in a dog that is really infected. Lab errors are a constant risk when doing PCR testing, as contamination of samples with even one organism can lead to a positive test result. For this reason, it is usually advised to combine PCR testing with serologic testing to get the most information possible when testing for ehrlichiosis.
Sometimes it is possible to see a cluster of Ehrlichia organisms in a white blood cell on a blood smear. If clinical signs of ehrlichiosis are present, this is sufficient for a presumptive diagnosis of infection. These inclusions are referred to as a morula if one is seen or morulae if more than one is seen.
Ehrlichisosis is probably missed when it is present in a fairly large percentage of dogs. The most common reason for this is simply not looking for it. The signs of the disease are fairly vague and are not specific for ehrlichiosis. The tests only give information on this specific disease, are somewhat expensive and take several days to get results from, making it difficult to recommend testing for every patient who has some sign of this disease. There is a new test kit for E. canis infection that can be run in any veterinary practice and this test appears to work well as an indication of antibodies to E. canis but does not provide enough information to differentiate between past exposure that was successfully handled by the dog's immune system and current infection. Still, the availability of this test kit may make it easier to screen for ehrlichiosis and decrease the potential for missing the disease early on.
Treatment for ehrlichiosis is usually accomplished with doxycyline (usually generic) or imidocarb dipropionate (Imizole Rx). Doxycycline is given in capsule form most of the time and can be administered at home. Imidocarb is an injectable medication given initially and then repeated in two weeks. The injection can cause a lot of salivation, nasal exudates, diarrhea or breathing difficulty so it is often given after an atropine injection, which cuts down on the side effects of the imidocarb.
Figuring out if treatment has been successful is quite difficult in dogs. If the infection has been cured the titer to E. canis should decrease over the course of 6 to 9 months but this isn't completely consistent. If clinical signs of illness persist it is important to keep in mind the possibility of a second vector borne illness and to consider changing the medication being used to treat the ehrlichiosis. Fortunately, treatment for ehrlichiosis is successful more often than not.
There is no vaccination to prevent this disease, so prevention efforts have to be directed towards avoidance of tick bites. Fipronil (Frontline, Frontline Topspot tm), permethrin (many products) and amitraz (Preventic Collars tm) are the most consistently successful tick control products. In severely endemic areas it might even be reasonable to administer doxycycline periodically to try to eliminate infections before signs appear but this is a questionable approach to prevention given what is known about antibiotic resistance at this time.
Cats appear to be able to be infected with E. canis but reported infections are uncommon and it is hard to be certain that E. canis is the infecting organism, although that is the best guess in some infections, currently. Affected cats have similar clinical signs based on the case reports so far. Serologic testing doesn't seem to be reliable in cats so PCR testing is the mainstay of diagnosis in this species. Doxycycline is usually recommended for treatment of cats but care must be taken to ensure the capsules or tablets are passed through the esophagus and into the stomach, usually be giving water with a syringe after administration of the doxycycline. There have been a number of case reports of esophageal damage attributable to doxycyline capsules hanging up in the esophagus and causing scarring or even complete strictures. Having a compounding pharmacy make the doxycyline into a liquid form can be helpful in preventing this problem. Immune mediated hemolytic anemia, which can easily be confused with ehrlichiosis, is also uncommon in cats, so it makes sense to consider both of these problems when signs of IMHA occur in cats.
Ehrlichia ewingii is another Ehrlichia species that infects dogs. It is carried predominantly by the brown dog tick and is most common in the Southern states. At this time it does not appear to infect cats. Affected dogs usually have acute severe lameness with discernible joint pain. There may be swelling of the joints in some dogs. Fever is usually present. Lymph node swelling is not a consistent sign. More rarely, neurologic signs have been reported, such as inability to balance. Bleeding disorders are not as likely as they are with E. canis but have been reported. Due to the clinical signs it is likely that at least some cases of E. ewingii infection are mistaken for Lyme disease. Treatment with doxycycline is usually effective and recovery is usually swift. This disease is most common in the spring and summer since the brown dog tick is most active during these times.
Ehrlichia caffeensis is a disease that most commonly affects people. It causes fevers, headaches and muscle pain. It can be fatal if untreated. It is carried by the brown dog tick (Rhipcephalus sanguineus) and the American dog tick (Dermacentor variabilis) This organism can infect dogs, although it is thought that most will not show clinical signs, or will have only mild signs of illness such as lethargy. There have been a very small number of more serious cases of disease in dogs. Clinical signs included nose bleeds, lymph node enlargement, lethargy, vomiting and eye inflammation (uveitis). Unfortunately, E. chaffeensis antibody cross reacts with E. canis antibody on serologic tests, making it difficult to be certain how frequently this infection occurs. Keeping ticks off of your dogs so that they do not serve as a reservoir for this infection in people seems like a reasonable preventative health care measure to me.
Another species of organism carried by ticks that infect people, cats and dogs is Anaplasma phagocytophilia (was Ehrlichia equi). This organism is carried by Ixodes ticks, the same ones that carry Lyme disease. In dogs infection with this organism may not cause clinical signs or may cause lethargy, fever, decreased platelet numbers and sometimes lameness. In cats the disease is also thought to be inapparent in most cases but may cause mild disease with the same signs seen in dogs. Perhaps the major worry with this disease is that it is thought to be a fairly frequent coinfection with Lyme disease and may be a factor in some cases of Lyme disease that appear to be non-responsive to treatment.
Anaplasma platys (used to be Ehrlichia platys) causes a cyclic thrombocytopenia, or periodic decreases in platelet numbers. This usually does not cause bleeding disorders but A. platys infection sometimes occurs concurrently with E. canis infection and the combination may lead to severe clinical signs in some dogs. This disorder can cause severe platelet deficiencies in some dogs (it has not been documented in cats). It would definitely be worth considering testing for A. platys if a dog had recurrent episodes of low platelet counts that can't be explained by the presence of another disease. This disease seems to have worldwide distribution, as it has been seen in the U.S, Europe, Asia and Africa. A paper with case reports from Israel reported more severe clinical signs, including lameness, fever, lymph node enlargement and lethargy in association with the cyclic platelet count abnormalities. (Harrus S, 1997)
Neorickettsia risticii (was Ehrlichia risticii) is most commonly recognized as the cause of Potomac horse fever, but it can infect dogs and cats, as well as horses. In dogs and cats it causes lethargy, vomiting, joint pain and bleeding disorders. This disease is not thought to be carried by ticks. It's life cycle is more complex than the Ehrlichia organisms and involves development in small snail species. It is not clear whether the snails have to be ingested or whether there can be other vectors such as aquatic insects. This life cycle is probably the main reason that the infection was noticed first in horses and only later discovered in dogs and cats, since horses are more likely to be eating vegetation that might harbor the snails or insects. Dr Mike Richards, DVM 4/06/2004
Question: Dr. Richards,
I'm a new subscriber, and looking forward to learning more.
My 3 1/2 year old borzoi bitch was diagnosed with ehrlichia at the age of 11 months. Actually my vet at the time tentatively diagnosed it as one of the rickettsial diseases; ehrlichia wasn't that well recognized then, or as common in Israel as it is now. She was treated with tetracycline, and seemed to recover. No real follow up was done - the vet didn't know and I hadn't yet learned enough to ask for a follow up titer and blood test.
A year and a half ago she showed signs of neck pains, the vet (same vet still) thought it might be wobblers syndrome or CVI, and referred me to a veterinary neurologist. At that point I started reading, found a reference to neck pain being a sign of ehrlichia, and went to a different vet. Titers were high positive for ehrlichiosis and there was thrombocytopenia, she was put on a course of doxycycline which improved her blood chemistry. 6 months later her titers were still high but the blood chem was fine - and since titers can stay high for up to a year the new vet wasn't worried. 6 months later a new vet (we moved) did a blood chemistry, saying that titers could stay high for years and that once a dog tested positive there was little meaning in future positives. The blood showed some very mild low platelet levels (185), though the lab said that the platelets had clustered and that actual levels were estimated much higher. Hemoconcentration was also high, although this is somewhat normal for sighthounds, as far as I know. There was also mild neutropenia. Based on these findings, the vet prescribed another course of doxycycline - she just finished 6 weeks. The new blood chem just came back, and there was very little change. She is feeling fine, and although she is a really lazy couch potato - common for borzois, has plenty of energy when she feels like it.
After this very long history, here are the questions: What does this picture mean to you? Is the ehrlichia still there, or could these be somewhat normal values for this particular dog? What is your opinion of the value of a titer for ehrlichia? If we do one now and it is low - great. But what would be the suggested course if it is still high? What is the significance of neutropenia?
The more I read about ehrlichia the more confused I am, since so much of it seems to be contradictory.
thanks in advance for your input! Marcia
I do not deal personally with many cases of ehrlichiosis, so what I am going to relate is my understanding of ehrlichiosis based mostly on literature references. I definitely understand your feeling that this disease is confusing because there are disagreements in the literature sources, because a full understanding of ehrlichiosis has not been achieved yet.
In reviewing abstracts of articles on ehrlichiosis that I could find on the PubMed web site and veterinary databases, there seem to be some trends that might help in your interpretation of what is happening.
* Doxycycline is still considered to be the most effective medication for treatment of ehrlichiosis but it does not work in all cases. A rough estimate of the failure rate based on several conflicting studies is somewhere between 25 and 40% of dogs treated. Other medications that may be sucessful include tetracycline, chloramphenical, imidocarb and fluoroquinolones such as enrofloxacin (Baytril Rx). Some studies have suggested that imidocarb and fluoroquinolones are as effective as doxycycline and some suggest they are not nearly as effective. I think it would be reasonable to try another medication if clinical signs returned, though.
* When it can be reasonably shown that ehrlichia organisms are very signficantly depressed or no longer present, using tests as Western blot, polymerase chain reaction (PCR) testing or negative blood cultures, titers tend to drop significantly, although a measurable titer may persist for long periods of time. I do not know how to arrange for these tests so it wouldn't surprise me if many other general practitioners don't know, either. So you may have to talk your vet into talking to an expert in this field. In the reference search suggestion below, Dr. Waner is from Isreal, so it may be possible for your vet to confer with him or her.
*In several studies, platelet counts returning to normal levels was a positive sign for response to therapy that correlated pretty well with other testing.
* It is not unusual for dogs to have more than one ehrlichia organism, another tick borne disease or even an organism that cross reacts on ehrlichia titer testing that may be confusing when interpreting titers or response to therapy.
* Dogs that have had ehrlichiosis do not appear to be immune to new infections, even when they have positive titers to the organism at the time of a new exposure. Either that, or chronic infection is being mistaken for new infections. I am not sure that it is possible to be certain which is happening at this time but at the literature references favor the susceptibility to new infections theory as far as I can tell.
If the titers did drop within a couple of months after treatment it would be a good sign. If not, I would continue to be a little worried about the possibility of a chronic infection. That would also hold true if platelet counts continued to be low normal on future (and non-clumped) samples. It is probably a good idea to check platelet counts for a couple of months.
You can find much of this information by searching the PubMed website http://www.ncbi.nlm.nih.gov, and using "Waner T" as the search term, then clicking on the related articles links. You might want to do this and consider printing out some of the research. It may be that your vet can arrange for one of the other testing procedures if you find yourself continuing to question the response to therapy based on clinical or laboratory signs (low platelet counts, continued high titers).
Mike Richards, DVM 5/22/2001
Question: Dear Dr Richards,
I am a new subscriber to the Vet Info Digest. I've often read your excellent information on the Web when researching for information for my pets, namely for my dog who has ehrlichiosis.
Balzac is an eight-year old mix of Black Labrador and Great Dane who was born here in Montreal, Canada. I adopted him from the SPCA when he was three months old. I brought him along to live with me when I moved to Mexico about when he was nine months old. We lived down there for about 4 years and then moved back to Montreal. Last summer, during a routine heartworm blood test to determine if he still had the disease, (he had tested positive the summer before)- (and was negative this summer after 12 months of treatment with Heartguard), we found out that his white and red blood cell counts were below normal and subsequent testing revealed that he had ehrlichiosis, which he probably caught in Mexico, where there are many ticks and where this disease is rapidly becoming endemic. In fact, the other dog that I had at the time that I lived in Mexico had caught the disease while we were living down there, so I was familiar with it.
However, contrary to my other smaller older dog, who was abruptly assaulted by this disease literally overnight, starting with diarrhea, gradual loss of appetite, trembling of the head and loss of usage of the hind legs, all this within about 2 weeks, and who was completely cured within two months, Balzac seems to have well surmounted the initial acute phase without symptoms and went on to the chronic phase without us really noticing anything. He was getting older and has a bit of arthrosis in his hips, which we thought accounted for the gradual loss of energy, playfulness and mobility he was experiencing. But after the diagnosis, we realized that it was the ehrlichiosis that was making him sick.
In mid-August, he initially tested positive for ehrlichia canis at 1/20 or greater - the end-point titer was positive up to 1/1600. Less than 2 months later his titer was at 1/10240, which shows that his immune system really kicked in. He was treated starting in August, upon the recommendation of a friend who is a neurological vet and with the agreement of my own vet, for eight weeks with 500 mg/day of Doxycycline. I was told it was useless to repeat the end titer test for at least six to eight months, because the titer would not go down until then. We did however, continue to monitor his red and white blood cell count - the red count went back to normal but the white is still down a little. In conjunction with the Doxycycline, we started him on ADEKs multi-vitamins with zinc daily as well as 500 mg of glucosamine and 400 mg of chondroitine which he still takes now.
He seems to have regained his health, he is now completely transformed - energetic and happy, he runs and plays again, eats and sleeps well. His white blood cell count however, remains a little low and that bothers me. My vet does not know why - ehrlichiosis is not a very-well known disease in Canada - and we don't quite know what to do about it, if anything.
I understand that Balzac's remission may be temporary and that the ehrlichiosis may come back, in which case he will immediately be put back on Doxycycline. Now that I know the symptoms, I will notice it more easily.
I would like to know what you think of this case, if you have ever seen anything like it, what you think of the low white blood cell count and what recommendations you may have.
Any information that may contribute to the well-being of my beloved dog will be greatly appreciated. Thank you so much for your time and attention. Sincerely yours, France
According to "The Textbook of Veterinary Internal Medicine, 5th Ed." by Ettinger and Feldman, it can take up to a year for the bone marrow to recover after a patient with chronic ehrlichiosis is treated for the disease. The reason that bone marrow suppression persists for so long has not been determined. If I interpreted the information in this reference correctly, giving doxycycline on a continuous basis to try to speed up the recovery process (or to try to ensure death of the organisms) actually slows down the recovery process in the bone marrow, so even though it is hard to wait around and see what happens, that is actually the best approach. While doing this it probably is a good idea to be very vigilant for signs of illness, since the depressed white blood cell counts, platelet counts or red blood cell counts (all are possible) could make it easier for other diseases to occur.
I do not see a great number of cases of ehrlichiosis but we have seen occasional patients with this condition. So far, I can't recall a patient with a recurrence of the illness, perhaps because we do not practice in an area in which the odds of reinfection are high. If that is the reason, then I would think that you also have a really good chance of never seeing a recurrence of the illness in Balzac, since reinfection isn't too likely where you live, either. There are reports of dogs who do not totally respond to therapy for ehrlichiosis but whether this means they are chronically infected or that their bone marrow or immune system has been permanently damaged is unclear. Our experience, although it is with a small number of patients, suggests that a recurrence of clinical signs is not very likely once patients are treated.
Good luck with this. I would be very hopeful that you will see a complete clinical recovery, including a return to normal white blood cell counts but it may take more time. It is good to keep track of this recovery. Patients in which the Ehrlichia canis or E. chafeensis organisms are eliminated usually have dramatic reductions in the titer, or no measurable titer, after six to eight months. It will be reassuring if you get a good result when you do recheck the titers.
Mike Richards, DVM 2/19/2001
Question: Dear Dr. Mike,
Thank you so much for this wonderful service. I am US military serving overseas and it is often difficult to obtain veterinary advice.
My 6 month old Rhodesian has tested positive for Ehrlichiosis (Elisa test). We put him on Doxycycline but I am worried that his platelet count is not improving.
His count before treating with Doxy was 174, after two weeks of treatment 168 and now after three weeks of treatment it is 146.
Is it possible that the dosage is not high enough to fight the disease? Or is this normal for this particular tick borne disease.
Any advise would be welcome.
The platelet counts that you are seeing in the test results are within the normal range for dogs, so it is possible that this is the level of platelet production that your dog normally achieves. It is definitely a high enough platelet count to produce expected blood clotting effects, as long as the platelets are functioning properly (usually there is no problem with this in ehrlichiosis).
It is possible that some platelet destruction is occurring and that you are seeing rises in the platelet levels by now. It wouldn't worry me, at all, if a patient of mine continued to have platelet numbers in this range, though.
Hope this helps.
Mike Richards, DVM 11/26/2000
Question: Dear Dr. Mike,
First, you have a very nice site and do the animal owners a service. Having just discovered your site while searching for information, I am happy to subscribe both to support your efforts as well as to give me the opportunity to ask a question of you.
I have read all the information I could find on your site concerning Erlichiosis and Rocky Mountain Spotted Fever, so I am hopeful that perhaps you can add to what you have already published.
I live back in the Tennessee woods, and although I have always used Frontline on my dogs, I usually skip January and February, and this year (to my everlasting shame), I was too preoccupied with my work schedule to go by my vet's office and hence ended up missing March as well. Apparently, a big mistake. I have a very athletic 4-1/2 year old SchH III German Shepherd bitch who competed in the DVG Nationals last year and who has earned a spot this year as well. Since I had her hips & elbows OFA'd before I bred her in January, and since she has never had any joint pains (not even "pano"), I was dumbfounded to see her limping a week ago after just a brief workout. (Because she had nine puppykins, this was the first time I had worked her since early February.) Headed straight to my vet. He examined her and re-Xrayed and saw nothing. So, knowing this was a big deal to me, he started digging. The titers for Erlichiosis and Rocky Mountain Spotted Fever were 1:80 and 1:128, respectively, and he stated that this particular test (??) was to be interpreted as positive for titers less than 1:40 and 1:64, respectively. He started her on Doxycycline immediately, and she's still taking it.
Now the questions. The more I try to learn about this disease, the more conflicting information I find, so I hope you can offer some clarifications. Since, in her case, we believe we caught the disease early on, can you give any odds for a complete recovery?? (My vet would only say that if the titers, when repeated in 6 weeks, were negative, that she _likely_ would be cured, but there was a possiblity that it would end her working career.) Can you offer any more definitive/quantitative assessment of the likely outcome? Is there any additional treatment that would improve the odds?
Second, this was only her second litter, and I had planned to breed her two or three more times over the next few years as she has produced some very nice pups. If she does not recover fully and I have to retire her from competition (which would kill her as much as me -- she loves to work), would it likely stress her system too much or cause her pain to breed her again in the future? If not, is there any possibility that the puppies would be affected in any way?
I appreciate any "enlightenment" you can share.
Thanks & regards, Richard
The current information on ehrlichiosis is that any positive titer at all should be considered as sufficient evidence to treat for this particular disease if there are clinical signs and known exposure to ticks. Doxycyline is the drug of choice at the current time. There is a great deal of controversy over whether or not dogs are completely cleared of this organism so it is not surprising that you are confused. The titer to the infection may stay high for years after an exposure and some dogs have persistently high titers who have never shown signs of clinical illness. The assumption in these cases is that the dog probably had a good immune response to the rickettsia that causes ehrlichiosis and did not need treatment. Some dogs respond well to treatment initially and then have relapses that really do appear to be due to recurrrences of the ehrlichiosis and the assumption is that they were never completely cleared. However, most dogs that show clinical signs will respond to doxycycline and will not have chronic long term joint damage, as is sometimes seen with Lyme disease. So basically, your vet has given you the best possible answer with the information available at this time. There is some hope that in the future PCR testing or some other form of identifying low numbers of ehrlichia organisms will allow us to differentiate the dogs that have almost been cured from the ones that have been cured. I don't think you can count on the titer to this disease disappearing any time soon but I would not overly worried about this ending her competitive career, since high titers persist in a lot of normal acting dogs. If there is clinical disease due to Ehrlichia, the earlier it is treated, the better. Early treatment resolves clinical signs more effectively than later treatment and may reduce the potential for long term infection.
Rocky Mountain spotted fever (RMSF) is even harder to draw conclusions about based on titers. I am somewhat convinced that anytime I want a diagnosis for a patient when I am struggling to find one that I can run RMSF titers and get a positive result. The situation probably isn't that bad but we get a lot of positive titers in situations in which we are not certain that the results are accurate. On the other hand, when there are clinical symptoms, when tick exposure is certain, or likely, and when there are titers greater than 1:64, we will treat for this disease. Doxycycline is also a good choice for RMSF, so we don't have to know which tick disease is present, for sure. I have a couple of patients that I have treated for reasonably certain cases of RMSF who had residual soreness or lameness for several months, so I think it is conceivable that it does some damage to the joints, although I have not been able to document this with X-rays. Most dogs seem to do fine after a few weeks to a few months, though.
Some of the more recent work on tick borne illnesses suggests that multiple infections are very likely to be present, so it is entirely possible that your dog could have both conditions or could have been exposed to both organisms.
I do not know of any additional therapy, except perhaps the use of anti-inflammatory medications to lessen the effects on the joints, if lameness seems to be persisting.
I would also consider the possibility that this is all just a red herring. Titers to tick borne diseases are present in a lot of dogs without any clinical signs, making interpretation of these titers difficult, as you have discovered. The most common problem leading to rear leg lameness in German shepherds that do not have hip dysplasia or cruciate ligament degeneration is probably intervertebral disc disease. This may present as an intermittent weakness or lameness, in some cases. If the lameness persists, it would be worthwhile to continue to try to rule out alternative problems. Especially since ehrlichiosis is usually associated with polyarthritis (affecting more than one limb) and since other signs, such as platelet deficiency, are very common with this infection and do not appear to have been a problem.
If she continues to be lame, breeding could cause problems, as the weight gain is hard with almost any orthopedic condition. Some bitches who have had ehrlichiosis will have future problems with breeding, including difficulty conceiving, abortion or death of puppies shortly after birth. I could not find any indication of how likely these effects are, though. Presumably they would be more likely in dogs with chronic illness (intermittent weight loss
I know this didn't clarify things, much. If you have additional information that you would like to ask about please feel free to write again.
Mike Richards, DVM 5/4/2000
Ehrlichiosis is caused by the rickettsial organism Ehrlichia canis. Other examples of rickettsial organisms are Riskettsia rickettsi, which causes Rocky Mountain Spotted Fever and Ehrlichia risticii, which causes Potomac Fever in horses. These orgainisms tend to be carried by ticks and other insect vectors, in some cases. For ehrlichiosis, the most common vector is the brown dog tick. For this reason, ehrlichiosis occurs anywhere this tick occurs. At present, it has been reported in 34 states, with the northern states being spared in most instances. The southeastern and south central states are the most heavily affected. A few cases of Ehrlichia canis infection have been reported in people after tick bites.
Ehrlichia infection can cause a number of clinical signs. It can be extremely hard to diagnose due to the wide range of symptoms that can occur. Most dogs infected with this organism will have be lethargic, lose weight, show less interest in food and become anemic. Other possible clinical signs include hemorrhages under the skin or in around the gums, swollen lymph nodes, muscular or joint soreness, nasal discharges or nosebleeds, severe neck or back pain, blood in the urine and eye problems ranging from exudates to severe inflammation of the internal eye structures. Neurologic signs such as seizures and difficulty walking can occur. Respiratory or heart related signs can occur due to hemorrhaging and compensation for anemia if it becomes severe. Hemorrhaging occurs primarly due to decrease in platelet counts from the infection. While most dogs show a number of symptoms when first infected with Ehrlichia, there is also a chronic infection that can occur if the acute infection is not treated. In this case, the dog may appear to be normal or may show vague signs of illness occasionally. This is one cause of the complaint that "my dog just isn't doing right". The chronic illness can suddenly become very severe again if the dog is stressed in some manner or become less immune competent for some reason.
The best method of diagnosing this disease is through testing of serum from the dog using an immunofluorescent antibody (IFA) test. Unfortunately, a positive test only indicates exposure. Still, in the presence of clinical signs or if the titer rises after treatment or stays consistently high, infection is strongly implied by the lab results.
Ehrlichia canis is normally susceptible to treatment with tetracycline antibiotics, including doxycycline. In some situations the organism will not respond to these antibiotics or their use is contraindicated due to the young age of a dog or pregnancy. In this case, chloramphenicol can be used and there is anecdotal evidence of success using cephalosporin antibiotics. The bleeding tendencies in this disease are related to a drop in platelets (thrombocytopenia) so it can be necessary to use corticosteroids to treat this condition if the platelet counts are low. While this can be life saving, the use of corticosteroids should be discontinued as quickly as possible so that their immunosuppressive effect does not interfere with successful treatment. Extensive supportive care, including intravenous fluids, administration of blood products and hospitalization may be necessary to treat this problem in some dogs. The survival rate is good if the disease is recognized and treated aggressively.
Mike Richards, DVM
Q: Hi Dr., our dog may have a severe case of Ehrlichia Canis, our vet says. However, most of the symptons described in the Q+A do not really show. Is nose-bleeding a symptom? She has had this a couple of times recently, and it was extremely hard to stop. She also may be possibly infected with Lichmaniosis (SP?), a disease that comes from a meditarrenean sand-fly. (she spent the first 4 months of her life in Portugal)? Are there any experiences as to the cross-reactions or interactions between Ehrlichia and Lichmaniosis? Thanks, Klaus
A: Klaus - I am sorry for the delay in replying. I practice in an area in which leishmaniasis is not a problem and I was not familiar at all with this problem. This does occur naturally in some areas of the United States (mostly Texas) and it is a problem in the Mediterrean area, as you note. A dog moving to the US from an area in which the infection occurs does have to be considered as a suspect for it when clinical signs are present.
Leishmaniasis is caused by a protozoan in the Leishmania species. Skin disease, polyarthritis (arthritis in multiple joints), mucosal disorders (lumps on tongue, gums, etc), damage to internal organs and possibly bleeding disorders. It is diagnosed by examination of tissues from affected dogs or by serology through antibody titers. I am not sure if there is a consistently effective medical treatment for this condition since there appear to be a lot of semi-effective medications listed in the veterinary literature.
The skin signs seen with this disease include loss of hair, scaling of the skin, ulceration of the skin on the limbs or ears, formation of nodules on the body and sometimes pustules.
Ehrlichiosis causes bleeding disorders and nosebleeds can occur when a dog is infected with this organism. It is usually a good idea to consider using an antibiotic, such as doxycycline, when ehrlichiosis is suspected. I am sure your vet already has done that.
Nose bleeds do sometimes occur with ehrlichiosis.
I could not find any information on dual infections but it is possible that the vet school at Texas A&M University may be able to provide more information on this since the problem occurs in their area, if there is still doubt about the diagnosis or prognosis at this point. Mike Richards, DVM
Q: I have an Old English Sheepdog that was not diagnosed for 2 years with Ehrlichiosis...she is having a relapse and I am afraid I will lose her...She has been on Doxi and Batril for 2 years but never gets better...her white and red blood cell counts are grim....Any Ideas ??? Please let me know , I love her very much , she is all I have ....
A: Dream- I am sorry for the later reply. We do not practice in a area in which ehrlichiosis is common and therefore do not have much practical experience with this. When doxycycline doesn't work, imidocarb dipropionate is sometimes recommended as an alternative. I do not know if it is possible to obtain imidocarb in the United States, though. If doxycycline is controlling the Ehrlichia organisms but the anemia continues to be non-responsive corticosteroids are supposed to be beneficial in some cases, or other immunosuppressive medications may be used. Blood transfusion are sometimes necessary in acute ehrlichiosis and it doesn't seem like they would be ruled out by the chronic nature of the problem you are seeing but they do have a short term benefit and would not probably be a good long term solution to the anemia and low white blood cell counts you are seeing.
I hope that this situation has been resolved successfully by now.
Mike Richards, DVM
Q: We have just been informed by our vet that our dog (a black lab mix) has ehrlichea. We found this out because we were having her tested to try to find out the cause of seizures she was having. How successful are the antibiotics usually used to combat this disease? Where can I find out more info on the disease? Any help would be greatly appreciated. Thank you, Glen
A: Glen- Tetracyclines, especially doxycycline, seem to be very effective for ehrlichiosis. Once in a while there is a recurrence of the condition despite apparently successful treatment. I hope this was the cause of the seizuring but suspect that it was not -- you may need to continue to treat that problem separately. Your vet will work with you that, I'm sure.
I'm pretty sure we have information on ehrlichia in our Dog Information area.
Mike Richards, DVM
Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...