Canine Babesiosis

Babesiosis is an important tropical tick-borne protozoan infection caused by a parasite of the genus Babesia. Canine babesiosis is an infection caused by tick-borne hematozoan Babesia canis or Babesia gibsoni, which occurs most commonly in southern United States, Arkansas, Florida, Arizona, and Oklahoma. Infections are most likely to occur in dogs less than 1 year of age. The disease is transmitted by Ixodid ticks. Once infected, the Babesia organisms multiply within red blood cells (erythrocytes). The infection has been associated with the "fading puppy syndrome". Infected erythrocytes are destroyed which causes anemia.

Dogs that are bitten by or were biters of other dogs are more likely to have the parasite, thus suggesting that blood-to-blood transmission contributes to the spread of this disease between dogs.

Signs of Babesiosis

Acute onset anemia occurs along with fever and lethargy. Although chronic infections occur, they are uncommon. Sudden death is a possible consequence of acute onset Babesia infection associated with low blood pressure shock and hypoxia. The wide variety of additional clinical signs depends on the tissues affected by the infection. Mild to severe pulmonary disease, diarrhea, vomiting, muscle pain, yellow-colored urine, rapid weight loss, eye discharge, and neurological signs are often reported.

Diagnosis of Babesiosis

Diagnosis is based on the identification of the organism within the blood cells. Antibody titers are also important to recognize the infection. Antibody titering is a laboratory test that measures the presence and amount of antibodies in blood. The body uses antibodies to attack and remove foreign substances.

Treatment of Babesiosis

There are a number of effective medications including imidocarb dipropionate and diminazene aceturate which are also the most widely used. In some individuals, combination therapy using clindamycin, metronidazole and doxycycline against canine babesiosis, proved to be effective, but other dogs showed uncontrolled relapse after a temporary recovery. Clinical reports suggest that Greyhounds are more likely to get infected than other breeds.

Recent studies show that some homeopathic remedies can be as effective as conventional drugs in treating canine babesiosis. It appears that C. horridus is as effective in causing clinical recovery in moderate cases of canine babesiosis caused by Babesia gibsoni as the standard drug diminazine. Large scale randomized trials are indicated for more conclusive results. Supportive therapy such as intravenous fluids and blood transfusions are employed when necessary.

Tick infestation control is the most effective way to prevent the disease. In some experimental studies, soluble parasite antigens (SPA) from different Babesia species have been shown to induce protective immunity when used as vaccine. When dogs were vaccinated with a vaccine comprising SPA from B. rossi combined with SPA from Babesia canis, protective immunity against experimental challenge infection was accomplished. Vaccination resulted in reduced clinical signs that resolved spontaneously, and reduction of parasites and SPA in the blood. Not a single infected erythrocytes could be found in blood smears of dogs that had been repeatedly boosted (three vaccinations in total) ⁵.

Some Babesia species can infect humans, particularly Babesia microti and Babesia divergens, and human babesiosis is a significant emerging tick-borne zoonotic disease. Clinical manifestations differ markedly between European and North American diseases. B. microti is the most common organism affecting humans in the United States. Infections are generally considered mild and can be treated with clindamycin.

In the United States, babesiosis is most commonly caused by B. microti. While more than 100 species have been reported, only a few have been identified as causing human infections. Babesia microti and Babesia divergens have been identified in most human cases, but variants (considered different species) have been recently identified. Little is known about the occurrence of Babesia species in malaria-endemic areas where Babesia can easily be misdiagnosed as Plasmodium.

The Babesia microti life cycle involves two hosts, which includes a rodent, primarily the white-footed mouse, Peromyscus leucopus. During a blood meal, a Babesia-infected tick introduces sporozoites into the mouse host. Humans enter the cycle when bitten by infected ticks. During a blood meal, a Babesia-infected tick introduces sporozoites into the human host. Deer are the hosts upon which the adult ticks feed and are indirectly part of the Babesia cycle as they influence the tick population. When deer populations increase, the tick population also increases, thus heightening the potential for transmission.

Babesiosis in Humans

Babesiosis, also called piroplasmosis, Texas Fever, Meadow Red, Redwater Disease, occurs in Nantucket, Martha's Vineyard, Shelter Island, and parts of Long Island. In humans, B. microti infection may be subclinical or may present as a febrile illness with constitutional symptoms and anemia. In humans manifestations are most severe in elderly and immunosuppressed persons. Manifestations of disease include fever, chills, sweating, muscle pain, fatigue, hepatosplenomegaly, and hemolytic anemia. Symptoms typically occur after an incubation period of 1 to 4 weeks, and can last several weeks.

Various species of Babesia (B. bovis, B. bigemina, B. divergens and B. yakimovi) are transmitted by ticks into wild and domesticated cattle. Large numbers of ruminants are killed by this parasite in tropical and subtropical areas of Australia, South America, South USA, and Africa where the parasites are endemic. The fight against babesiosis is a major economic factor in these areas. Babesia bovis infection is probably the most important cause of "tick fevers" of cattle. The fact that some breeds of Bos indicus are relatively resistant to the effects of this parasite has led to the suggestion that the organism evolved in these breeds.

Babesia canis infection is a common cause of death in dogs. Mildly affected animals develop anemia and fever, are lethargic and have poor appetite. They show no visible signs of jaundice and recover after a few days. More severe cases show a wide variety of signs, including severe depression, salivation, vomiting, diarrhea, jaundice and bloody urine.

Prevention of Babesiosis

Vaccination against the parasite is the only mean of fighting the disease.

Equine babesiasis is widespread; severe clinical disease and mortality may occur occasionally. Therefore, the elimination of carrier infection in horses being shipped from endemic zones to Babesia-free areas gains increasing importance. Various drugs may be used for clearing Babesia caballi infections.

Canine babesiosis is becoming increasingly widespread in the USA, Europe, Africa (B. canis) and Asia (B. gibsoni). The disease can be treated with a few antibabesial drugs causing more or less toxic side effects, such as diminazene (which is not recommended for use in dogs by the manufacturer), imidocarb, amicarbalide, phenamidine and trypan blue.

References:
1. Clinical Medicine of the Dog and Cat Michael Schaer
2. Blood, Bull Terriers and Babesiosis: further evidence for direct transmission of Babesia gibsoni in dogs.Jefferies R, Ryan UM, Jardine J, Broughton DK, Robertson ID, Irwin PJ.
3. A Possible treatment strategy and clinical factors to estimate the treatment response in Bebesia gibsoni infection.Suzuki K, Wakabayashi H, Takahashi M, Fukushima K, Yabuki A, Endo Y.
4. Clinical management of babesiosis in dogs with homeopathic Crotalus horridus 200C.Chaudhuri S, Varshney JP.
5. Immunity against Babesia rossi infection in dogs vaccinated with antigens from culture supernatants.Schetters TP, Strydom T, Crafford D, Kleuskens JA, van de Crommert J, Vermeulen AN. Parasitology R&D Department, Intervet International B.V. The Netherlands
6. Chemotherapy against babesiosis.Vial HJ, Gorenflot A. Dynamique Moléculaire des Interactions Membranaires, UMR 5539 CNRS/Université Montpellier II