Tiny, eight-legged creatures born to be prolific vectors of disease in both dogs and humans, ticks are the second most significant carriers of disease next to mosquitoes, and the leading pathogen of illness in humans. When they're infected with the intraerythrocytic protozoan parasites of the genus Babesia, the Ixodes species of ticks can be deadly or significantly devastating to their unfortunate host in the disease babesiosis which is similar to malaria.
Neither insect or spider, ticks belong to a special group of mites — invertebrates with external skeletons and jointed legs (Arthropods). And Ixodes ticks, like all other species of ticks, are external parasites (ectoparasites), living by feeding on the blood of mammals, birds, and occasionally reptiles and amphibians, which is how they transmit the babesia parasite. While Ixodes ticks are the primary vector, some other species of ticks may also carry the disease.
Where are babesia parasites most prevalent?
Plagued by their deserved nasty reputation, millions of ticks are thankfully exterminated each year via pesticide applications or otherwise curtailed from causing serious illness in dogs treated with tick prevention medications. Yet, still, every year, many dogs become infected with babesia regardless of these safeguards. Babesia is found worldwide, but in the United States, most canine cases of babesiosis occur in the southern states. It has also been reported farther north in Massachusetts, Pennsylvania, and New Jersey.
What animals are affected by babesia?
Dogs, as well as cattle and humans, can be affected by babesiosis, also known as Texas cattle fever, Redwater, and piroplasmosis. One babesia parasite species, Babesia gibsoni, primarily affects pit bull terriers. Further, dogs such as racing greyhounds housed in kennel environments with poor tick control are at increased risk for the infection.
How does my dog get infected with the babesia parasite from a tick bite and what happens?
In the world of microorganisms, reproduction is asexual (schizogony), and through the process of division or multiple fission, parasites produce or give birth to two or more new organisms. As reservoirs for babesia, Ixodes ticks become infected with the parasite, and like the vampires of folklore, become vectors or carriers. When the tick bites a dog, its bite is akin to an inoculation and injects the babesia into the dog's bloodstream. When babesia are at the piroplasm stage in their complex life cycle where they're capable of initiating a new asexual cycle of development (merozoites), they aggressively invade the dog's red blood cells causing hemolytic anemia or the destruction of red blood cells. With the initial infection, your dog's body will fight back to produce red blood cells to replace the ones it lost, but if unsuccessful, anemia occurs. The excess hemoglobin is released, which can result in jaundice or icterus.
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Evidence suggests that an infected dog with oral lesions or wounds or abrasions can infect another dog through a bite, leading to the incidence in pit bull terriers. Some studies have also shown that babesia transmits transplacentally to unborn puppies in the uterus. Tainted blood transfusions are yet another mode of inadvertent transmission.
What are the symptoms or clinical signs of babesia infection in your dog?
Symptomatically, a babesia infection presents in a wide range of severity from sudden collapse with systemic shock to a hemolytic crisis or hyperhemolytic crisis characterized by an accelerated rate of red blood cell destruction causing anemia, jaundice, and reticulocytosis — dogs typically present with these acute signs. Conversely, symptoms can be vague or non-existent as the infection slowly progresses undetected. Seek veterinary care at once if your dog displays any of the following clinical symptoms of a babesia infection:
- Lethargy or lack of energy.
- Loss of appetite.
- Weight loss
- Swollen abdomen.
- Abnormally dark urine color.
- Unusual stool color.
- Yellow-to-orange-tinged skin.
- Pale mucous membranes such as the gums.
- Swollen lymph nodes (lymphadenopathy).
- An enlarged spleen.
How is babesiosis diagnosed by your veterinarian?
Once your dog exhibits any of the classic symptoms of a babesia infection, observe her carefully and take notes that will assist your veterinarian in his diagnosis. He will want to know if and when your dog was bitten by a tick and her behavior and any signs of illness since the onset of the first symptom. Your vet will also review your dog's medical history and do a full physical examination.
A complete blood count of red and white blood cells and a blood profile may reveal anemia, low platelets which assist in blood coagulation (thrombocytopenia), or low albumin, a blood protein (hypoalbuminemia). Blood smears were typically used to visually detect the parasite in the past. However, several additional diagnostic tools such as FA (fluorescent antibody) staining of the organism, ELISA (Enzyme-Linked Immunosorbent Assay) tests and polymerase chain reaction (PCR) tests are commonly used nowadays to diagnose babesiosis.
A urinalysis may indicate bilirubin, a product of the red blood cell breakdown which is normally carried through the bloodstream passing into the liver where it's removed and becomes part of bile. When bilirubin is present in the urine it indicates liver damage or disease.
What is the treatment protocol for babesia infection and prognosis?
Hopefully, one day in the near future we'll have a vaccine to protect our dogs from babesia and other tick-borne canine diseases. In the meantime, the prognosis for babesiosis is guarded. Babesiosis symptoms are persistent and tend to recur — many dogs remain sub-clinically infected, thus relapse is a strong possibility. Affected dogs may also spread the disease in future and should never be used as blood donors.
Treatment protocol as of 2018, consists of intramuscular or subcutaneous administration of the FDA approved drug imidocarb diproprionate or imiozol, trypan blue, or pentamidine isethionate. One readily available antibiotic which has shown promise and seems to be an excellent starting point for the treatment regimen of canine babesia is Clindamycin, the gold standard treatment for Babesia microti, the major species that infect humans.