Babesiosis is a group of tick-borne diseases of mammals including zoonotic diseases in humans. They are caused by protozoa of the genus Babesia, which parasitize erythrocytes, producing hemolytic anemia. In the U.S., the organism's natural host is mice and transmission is by the deer tick Ixodes scapularis. Cases of babesiosis from across the United States are to be formally reported to CDC. Canine babesiosis is becoming increasingly widespread in the USA, Europe, Africa. The infection is caused by the tick-borne hematozoan parasites Babesia canis or Babesia gibsoni. Infections are most likely to occur in dogs less than 1 year of age and has been associated with the "fading puppy syndrome." 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. Greyhounds are more likely to get infected than other breeds.
The destruction of infected red blood cells causes anemia. Acute onset anemia occurs along with fever and lethargy. Although chronic infections occur, they are uncommon. Sudden death is a common consequence of acute onset babesiosis and generally results from 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 is based on the identification of the organism within the blood cells and antibody titers test. 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 proved to be effective, but other dogs showed uncontrolled relapse after a temporary recovery. In some experimental studies, vaccination against Babesia species showed promising results. Soluble parasite antigens (SPA) from different Babesia species induced 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 red blood cell could be found in blood smears of dogs that had been repeatedly boosted (three vaccinations in total).5 However, because the vaccine is not yet available, tick infestation control is the most effective way to prevent the disease.
Babesia bovis infection is probably the most important cause of "tick fevers" of cattle. The fact that some breeds of cattle are relatively resistant to the effects of this parasite has led to the suggestion that the organism evolved in these breeds. Various species of Babesia (B. bovis, B. bigemina, B. divergens and B. yakimovi) are transmitted by ticks to wild and domesticated cattle. Large numbers of ruminants are killed by this parasite in tropical and subtropical areas of Australia, South America, southern United States, and Africa where the parasites are endemic. The fight against babesiosis is a major economic factor in these areas. Equine babesiosis 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.
- Michael Schaer. Clinical Medicine of the Dog and Cat
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