Tick-Borne Disease in Dogs
B-Naturals Newsletter – April 2009
Tick-Borne Disease in Dogs
Lew Olson, PhD Natural Health
In September 2003, B-Naturals featured Gil Ashe’s article on Erlichia. Gil began researching tick disease when her beloved German Shepherd dog, Thunder, was dianosed with Erhlichia risticii. She has generously shared her knowledge with others for many years in memory of Thunder.
B-Naturals is pleased once again to bring you another article written by Gil, titled ‘Quiet Killers: Tick-Borne Disease in Dogs’. We will present this article in two parts, with Part I which includes her introduction, the definitions of different tick diseases, their symptoms and disease progression, transmission of the diseases and tick removal. Part II will come out in May and will provide information on tick prevention, testing and treatment. We trust you will find the information in this article not only timely with the season, but also eye-opening and very informative.
PART I: quiet killers: tick-borne disease in dogs
by Gil Ashe
. . . for Thunder and all the dogs who were diagnosed too late or not at all
Something was wrong with Casey. Instead of bounding around with her usual energy and good spirits, she always seemed tired these days and her eyes were constantly bloodshot. Where once she would have been up like a shot and ready for the day, getting to her feet was becoming more difficult and sometimes she'd limp, first on one leg, then on another. Even her behavior had altered; the ten-year-old Border Collie/Keeshond mix had become aggressive toward one of the cats she'd lived with all her life. It was as if Judith Sookne had gradually acquired a dog that only looked like her Casey and she was at a loss to know why – until one evening an answer jumped at her as she checked through Casey's fur for ticks, something so obvious she wondered that she hadn't thought of it before. Judith took Casey and her newly aroused suspicion of tick-borne disease to the vet.
Tick-borne disease? Impossible. Her vet dismissed the idea. Evidently, where Judith saw a dog that might be helped, she saw a dog that was just getting old and refused a request for tests to find out if Casey had been infected with a tick-borne disease, saying that some minor arthritis was normal in a dog her age and Casey's bloodwork was normal. As it happens, however, signs of infection do not always show up in routine bloodwork and Judith knew it. She remained firm in her belief that there were reasons beyond age for what Casey was going through and eventually demanded the tests that her vet opposed so adamantly.
Annoyed, her vet changed tactics and agreed to comply – up to a point. She would draw blood and prepare the serum sample but if Judith wanted these tests run, particularly if she insisted on sending them to a lab specializing in tests for TBD, she would have to mail the sample herself. As a deterrent, it failed miserably; Judith had no problem at all with using Fed-Ex and, a few days later, held the test results in her hand: Casey had tested positive for both Rocky Mountain Spotted Fever and Ehrlichia canis.
As is often the case, Casey responded almost at once to treatment, made her peace with the cat, regained her spirits and stopped limping. Now past thirteen, she is slowing down but not so much that she has lost her zest for life or her interest in squirrels. She was lucky.
Every day, dogs like Casey are taken to the vet because they just "ain't doing right" and every day, vets look at common, all-too-familiar symptoms and address them separately rather than asking themselves if they might not be looking at a syndrome, a group of related things that might point to something far more serious. The usual approach would seem to make sense. After all, how alarming, say, is a slight fever and diarrhea in a dog that has lost his pep and been off his feed for a few days? The trouble is, the usual approach doesn't work when you're dealing with TBD. In his foreword to Ehrlichiosis, a Silent and Deadly Killer, the first Internet website to make clear, well-researched information on TBD available to everyone, Ibulaimu Kakoma, DVM, Ph.D. notes that "the spectrum of syndromes and disease entities imitated by ehrlichiosis are incredible" and emphasizes the need to rule out ehrlichiosis for common infectious disease.
Tom Beckett, DVM, of Austin, Texas, whose years of experience in the field parallel Dr. Kakoma's in the research laboratory, has come to the same conclusion. "Many of the TBD cases I see have vague, nonspecific, "nagging" health problems rather than the more specific and dramatic symptoms the textbooks describe. The dogs seem to be somewhere 'in between' the symptoms-free subclinical stage and the definitively symptomatic chronic stage. Unfortunately, quite often one of two responses occurs: either the problems are dismissed as a (mis)perception of an overprotective owner or due to 'normal' processes such as aging; or a whole host of tests and other diagnostics is done – but the diagnostics do not include tests for TBD. There needs to be greater awareness among owners and veterinarians that dogs with these presentations should have a comprehensive panel of tests for TBD antibodies as part of their initial workup."
The key to curing all tick-borne disease is early diagnosis and treatment.
There are vets who refuse to consider TBD as a possibility and say "it can't happen here". That attitude can have serious consequences for dogs and one hopes it is becoming less common as knowledge of TBD and its danger spreads. Anywhere in the United States that the hard-bodied Ixodid ticks are found, the diseases they carry can be found. Dogs travel with their owners, or to new owners from kennels or rescue facilities, and ticks go with them. A warming climate increases the range in which ticks can live and in places where it was once assumed that TBD could not happen, it does. Clearly, there are places where it is more likely, but no one can say, "it can't happen here", until they know where the dog has been and they make dead sure that tick-borne disease has never been found in their area.
Those veterinarians who have never seen, or more properly, recognized a case of TBD may be handicapped by their lack of knowledge. Focused on what appears to be wrong, they treat for it and are puzzled when the dog gets no better. Well, that wasn't it. What else could it be? Considering a list of possibilities, the vet chooses another and the outcome is unfortunately the same. In the end, stymied and more than a little frustrated, he or she may suggest a specialist for what the dog appears most likely to have, or fall back on the diagnosis that is no diagnosis at all: a genetically defective immune system. There is nothing that points so suggestively to tick-borne-disease as a vet who is stumped or who sends you running to one specialist after another. It is a red flag alerting the dog's owner to think hard about having a tick panel run and doing it quickly. One luxury you do not have a great deal of in dealing with TBD is the luxury of time.
The Tick-borne Diseases: A very brief introduction to the five dollar words which can spell trouble for your dog.
Ehrlichia canis, found world-wide, is the most common and one of the most dangerous tick-borne disease organisms known to infect dogs; as it has been the object of the most study and as many of the TBDs follow its general pattern, it will be discussed in more depth than the rest.
Parasitic bacteria which share some of the traits of viruses, E. canis proliferate inside the white blood cells manufactured in the bone marrow. As the disease they cause progresses, it cripples the ability of the white blood cells to replicate correctly or, in the end, at all, and the immune system is effectively destroyed. But that's not the end of it; the list of symptoms and conditions that can be caused by E. canis seems almost endless; it can be mistaken for or cause leukemia, heart disease, cancer of the spleen, the brain and other organs, to name only a few. This is a dangerous, treacherous organism.
In the first, or acute stage of E. canis, the outlook for cure is best, but symptoms can be vague and easily missed or put down to a mild viral infection. If a dog is feverish, if his lymph glands are enlarged and he's generally off-color, a vet looking further may find the characteristic signs of early TBD: an enlarged spleen, an abnormal decrease in blood platelets, an abnormal decrease in white blood cells, and/or nonregenerative anemia. And just to make things more complicated, a high white cell count may be seen instead. Testing for TBD is useless for two or three weeks after a dog has been infected, however, as the immune system will not have had time to make the antibodies that register on a test until enough time passes. But a correct diagnosis depends on much more than numbers on a sheet of paper. Some dogs with E. canis never do mount a detectable titer and some have a very low titer that, by itself, would not indicate the need for treatment. It is your vet's knowledge and experience of TBD that can make all the difference then.
If a dog is unable to throw off E. canis by himself in the acute stage, the disease passes into the second, subclinical stage where there are no outward symptoms, hides out in the spleen and the dog becomes a carrier, although he may appear to be completely normal. E. canis may remain in this stage from months to years until something – another infection, stress, or simply a body worn out by an unending struggle with the disease, particularly if he is ill with another – causes the dog to go into the final, chronic stage.
Once it becomes chronic, the prognosis for recovery is poor and the end can come with shocking suddenness if no one is aware the dog is infected. A serious deficiency of all the blood elements (pancytopenia) is quite possible at this stage; death may come from hemorrhage, multiple organ failure or secondary bacterial infection.
German Shepherd Dogs, many of whom died of E. canis serving as war dogs in Vietnam, "appear to have depressed cell-mediated immunity as compared to other breeds and are more likely to develop severe disease", according to Cynthia Holland, Ph.D., an authority on tick-borne disease in dogs and horses. For GSDs, prompt, early diagnosis and treatment of E. canis is especially critical. The primary vector for E. canis in the United States is the brown dog tick, Rhipicephalus sanguineus.
Ehrlichia chaffeensis is a less common cause of ehrlichiosis which was first identified at Fort Chaffee, Arkansas in the United States. Its known geographic distribution ranges from the South and South Central states to lower New England. Significant lameness is a marked symptom and E. chaffeensis is thought to be both serious and harder to clear from a dog than E. canis, which in many ways it resembles. It also occurs in humans. The brown dog tick, R. sanguineus, and the Lone Star tick, Amblyomma americanum, carry E. chaffeensis.
Ehrlichia ewingii, found mostly in North Carolina, Florida and Missouri, has been identified in ticks in Texas but its geographic distribution may be wider than currently realized. It shares characteristics of A. phagocytophilum and E. canis but does not appear to cause as much damage to the dog and, like E. chaffeensis, has been known to infect humans. E. ewingii is carried by the Lone Star tick, A. americanum.
Anaplasma phagocytophilum, once known as E. equi, is presently considered less of a threat than E. canis, though anecdotal reports of dogs suffering serious repercussions and/or dying from it may cause that conclusion to be reconsidered. A. phagocytophilum can cause painful arthritis in several joints, lethargy, high fever, loss of appetite, vomiting and diarrhea. Less commonly, a dog may have neck pain or seizures due to central nervous system dysfunction. A. phagocytophilum is carried by Ixodes scapularis, the black-legged or deer tick, and Ixodes pacificus, the Western black-legged tick, both of which also carry Lyme disease.
Anaplasma platys, once known as E. platys, causes severe cyclic thrombocytopenia, targeting the blood platelets that stop bleeding and promote clotting. A few days after infection, platelet counts drop dramatically; in another few days, they rise to normal, then the cycle begins again. A. platys is self-limiting and gradually goes away except when another TBD is also present to aggravate it and be aggravated by it. There is grave danger of hemorrhage during surgery on a dog with A. platys unless the surgeon knows about it and exercises caution. A. platys is carried by the brown dog tick.
Neorickettsia risticii, once known as E. risticii, is best known as Potomac Horse Fever or Shasta River Crud and is not carried by ticks. So why is it here? Well, until a few years ago no one knew exactly what the vector (the agent carrying it) was and ticks seemed the likely candidate. Now, we know that it gets to the dog by a complicated process that starts in some freshwater snails and ends by the dog ingesting one of the insect vectors that live and fly over water. How? It may fall in his food, he may lap it up from a river or puddle, or, as many dogs do, he may snap at and swallow the infected insect. And the damage is done. Once established in its canine victim, N. risticii behaves like E. canis but with a virulence that makes it fortunate this disease is not considered common. Dogs which develop chronic N. risticii have almost no chance of surviving.
Rocky Mountain Spotted Fever, oddly enough, is found more often in the East than the West, though it occurs all over the continental US. Caused by Rickettsia rickettsii, RMSF is an acute disease which has no progressive stages. In considerable pain from the infection, a dog may be unable to keep his balance; he may hold his head at a tilt, act as if he is only half conscious, suffer seizures or go into a coma. Without treatment, he will either get well in two weeks or die.
Because of the speed with which this disease can kill, chances of survival are much higher if the dog is treated with doxycycline immediately the disease is suspected, without waiting for test results. A pair of tests are run to confirm a diagnosis of RMSF, the second 21 days after the first. If the second titer is four times as great as the first, the diagnosis is rock solid.
Dogs which survive become immune to any further infection with RMSF, though they may carry detectable titers for a considerable time, perhaps for life. Those which manage to make it through on their own without help may always suffer varying degrees of neurologic dysfunction. The vectors of RMSF are the American dog tick, Dermacentor variabilis, the wood tick, D. andersoni, and the brown dog tick, R. sanguineus.
Babesia canis and Babesia gibsoni are protozoal parasites, not bacteria like the other organisms that cause TBD. Hemolytic anemia, essentially destruction of the red blood cells that carry oxygen to the blood, is the hallmark of babesiosis and half of all infected dogs will need transfusion. In the peracute (violent, sharp) stage, clinical signs may appear suddenly, followed by shock that cannot be reversed and death. The peracute and acute stages are not seen often in the US, however, as most adult dogs diagnosed with babesiosis are subclinical, i.e., carriers without evident clinical signs, and remain so unless something upsets the precarious balance between the immune system and the disease.
In the chronic stage, the jaundice and anemia of earlier stages is not as apparent but dogs are weak, their mucous membranes may be pale and body condition deteriorates along with appetite. The spleen of a dog with chronic babesiosis is very enlarged, according to Ron Hines, DVM, Ph.D., and often kidney and liver function is poor. Feces may be yellow and the urine may appear orange. Babesia canis can infect any dog and is very often found in greyhounds rescued from race tracks, while B. gibsoni is almost always found only in pit bull terriers. Babesiosis is generally detected in blood work done on a dog without symptoms or in the chronic stage. Direct blood-to-blood transmission of B. gibsoni has occurred in fighting dogs. Unfortunately, the disease can be mistaken for Auto-immune Hemolytic Anemia (also called Immune Mediated Hemolytic Anemia) as an infected dog will test positive for AIHA.
Dr. Hines notes that another strain, B. canis vogeli, occurs all over the Southeastern US. While it is the weakest of the Babesia, an occasional dog will develop severe anemia from this strain and his blood will fail to clot. It is especially common in greyhounds. The brown dog tick, R. sanguineus, is the vector for B. canis and presumably B. gibsoni as well.
Lyme disease, caused by Borrelia burgdorferi, hardly needs an introduction to people in the Northeastern US where it is most prevalent and where it was first identified in the town of Lyme, CT. Lyme is not, however, as destructive as many of the other TBDs; as a rule, active Lyme disease may cause crippling arthritis but it doesn't kill. The exception to that is when it causes Lyme nephritis (glomerulonephritis), an inflammation of the glomeruli of the kidneys marked by a drop in the production of urine which will have blood and protein in it (proteinuria). The end result is renal failure. So far, Lyme nephritis does not appear to be common but it would be wise to have regular blood work done on a dog diagnosed with Lyme disease to keep an eye out for signs of kidney problems.
Bartonellosis, caused by Bartonella vinsonii, subsp. berkhofii, like most of the TBDs, is characterized by vague symptoms at first: lethargy, weight loss and lack of appetite. Fever is not one of the early signs. Half of all dogs with B. vinsonii develop thrombocytopenia (a serious reduction in blood platelets), according to Ed Breitschwerdt, DVM, of North Carolina State University, world-renowned for his work in vector-borne disease in dogs. He notes that, at present, the incidence of bartonellosis seems to be low and the disease occurs most often in dogs which roam free, live in a rural area and are heavily infested with ticks. Many of these dogs are also infected with Ehrlichia canis or Babesia canis. The brown dog tick, R. sanguineus, is a probable vector.
Infection with more than one tick-borne disease is common and results in more serious illness.
Hepatazoon americanum is an oddity in that the dog bites the tick, Amblyomma maculatum, rather than the other way around. The dog becomes infected by swallowing A. maculatum, found mostly in the humid regions surrounding the Gulf Coast, and the infectious parasites it carries migrate through the intestines to the muscles and the membrane covering the bone. The rapid proliferation of these parasites inside cells causes the cells to rupture which, in turn, causes severe pain. Many of the symptoms found in other TBDs are also seen, including fever, lethargy, lameness and anorexia. To date, there is no cure, though good supportive care may relieve or lessen a dog's symptoms.
Tick paralysis is very different from other tick-borne disease in this respect: it doesn't depend on an infectious organism. It occurs when an engorged female tick produces a neurotoxin in her saliva, then injects that saliva into the dog on which she's feeding. The onset of signs is sudden and includes difficulty breathing or barking, rear end weakness and staggering. Starting with the hind legs, paralysis moves rapidly toward the head and the dog will soon be unable to move, stand, sit, or lift his head. If the tick is found and removed in time, improvement is generally seen within 24 hours. If the tick is not found and removed soon enough, the outlook is grim.
Animals have a great many more chances than humans to encounter ticks, so while the incidence of tick paralysis in humans is low, the threat to livestock and dogs is a good bit higher. No matter what the probability of tick paralysis might be, however, dog owners should be aware of how it operates as the outcome can be severe injury or death if it is not recognized and dealt with quickly.
Ticks can be carriers for more than one TBD. Cross-infection is common.
When a tick has found a likely place to feed – often on the ear, close to the body under the leg, between the toes, on the neck or shoulder – it punctures the skin with pincers finer than a hair (chelicerae), then inserts a specialized mouthpart that it will use to drink the dog's blood. This mouth part, called the hypostome, has barbs along its length which are efficient at cutting in and help to anchor the tick in place. To make itself even more secure, the tick secretes a cement around the edges of the wound that will later dissolve when it is ready to detach. Once that is done, it is ready to feed.
It is the tick's saliva that contains an anticoagulant to keep blood flowing freely and the saliva that carries disease. As the tick alternately regurgitates it into the dog and sucks blood out, peristaltic action causes the infectious organisms in its midgut to move up through the large salivary glands branching to either side of its body. Fortunately these organisms move sluggishly; it takes a minimum of 24 hours as a rule for them to reach the point where they will be pumped into the dog. On occasion, infection has occurred in less time but this probably doesn't happen often so we have a grace period after the tick latches on to remove the tick ourselves or for a preventive to stop the tick's ability to feed and kill it. Because the relatively small male is under the female as she drinks and is mating with her, when they die an entire new generation has no chance to be born. Sometimes nature is both wonderful and frightening.
Never remove a tick with your fingers. Never burn it, put petroleum jelly on it, twist it or jerk it off the dog. Ticks breathe only a few times an hour so attempting to suffocate one is next door to useless. Grasping one with your fingers, you are all but guaranteed to squeeze the tick and propel any infectious saliva into your dog. Burning or using irritants on ticks can cause them to convulse and achieve the same outcome. As for 'unscrewing' a tick, they do not screw themselves in the first place. The best and safest way to remove a tick is to use a small, inexpensive, curved Kelly forceps, a pair of tweezers or one of the tools especially made for the purpose, catch the tick right behind the flattened 'head' (capitulum) as close as possible to the dog's skin, and pull gently straight out. Drop the tick in a solution of water and dish soap to kill it.
If your dog is covered with the tiny nymphs called seed ticks which are far too numerous to remove one by one, you can bathe the dog with Ivory dishwashing liquid. Work up a good lather, leave the suds on for 15 minutes then rinse thoroughly with plain water. Ivory liquid is gentle enough not to cause skin irritation but it will kill immature ticks.