Babesia canis is a protozoal parasite which infects red blood cells and can lead to anemia. Babesia canis is transmitted by the brown dog tick (Rhipicephalus sanguineus) and is one of the most common piroplasm infections. The brown dog tick is adapted to warmer climate, therefore most infections come from the southern and southeastern United States and from California, especially in shelters and greyhound kennels. Babesia canis is also predominately in Europe and transmitted by Dermacentor ticks with an alarming increase in infections due to people traveling with their pets.
"Dogs become infected with Babesia canis when a tick feeds on the blood and releases sporozoites into the dog's bloodstream. The young Babesia organisms attach to red blood cells, eventually penetrating and making a new home for themselves within. Inside the red blood cell, the Babesia organism divests its outer coating and begins to divide, becoming a new form called a “merozoite” which a new tick may ingest during a blood meal."  "Following ingestion by the tick, Babesia undergoes sexual reproduction (gamogony) followed by asexual reproduction (often schizogony and always sporogony), resulting in numerous sporozoites (in the tick salivary glands) that are infective to vertebrate hosts."  Pregnant dogs can give Babesia canis to their unborn puppies and it is recommended that infected females should not be bred.
Symptoms, diagnosis, and treatment
The clinical signs of Babesia canis are lethargy, weakness, vomiting, anorexia, fever, pale mucous membranes, and dark discoloration of the urine. There may be other symptoms including neurological and respiratory signs.
Babesia canis is not easy to diagnose. A veterinarian can take a blood smear, but the odds of being able to see the parasite is unlikely as it is small. If the veterinarian wants to take blood, it is best to take it from a capillary source (such as a fresh cut) than from a blood vessel. The most current and best way to diagnose Babesia canis is polymerase chain reaction (PCR) testing. "This is extremely sensitive testing and can distinguish four different species of Babesia. While only certain laboratories run this type of testing, this is really the best method." 
"Dogs infected with Babesia canis usually respond to treatment with imidocarb dipropionate at a dose of 6 mg/kg IM administered twice at 14-day intervals. A higher dose administered once is recommended occasionally but can result in neurotoxicity. Treatment for babesiosis reduces parasitemia and supports resolution of clinical signs, but it is important to remember that the infection itself may not be eliminated. Dogs diagnosed with Babesia should be considered permanent carriers of the infection." 
Vaccines are not available in North America to prevent Babesia canis, but in France there is a vaccine available although it only seems effective against certain strains. The best prevention is tick control. If you find a tick on your pet it should be removed promptly to prevent transmission of any pathogens they may harbor. "To avoid potential exposure to zoonotic pathogens and accidental inoculation of agents into the pet during the removal process, ticks should be retracted using forceps or a commercial tick-removal device, and care should be taken to avoid contact with tick contents, ideally by wearing gloves. Careful attention to handwashing following tick removal is also recommended. Blood donors should be screened for infection with Babesia canis by serology, PCR, and blood smear, and any dogs testing positive excluded. Splenectomy or corticosteroid treatments of Babesia-positive dogs should be avoided as much as possible."
- Cornell University. "Babesia Canis". Cornell.
- Irwin, Peter. "Canine Babesiosis". Canine Babesiosis: 1141.
- Halos, L.; Lebert, I.; Abrial, D.; Danlois, F.; Garzik, K.; Rodes, D.; Schillmeier, M.; Ducrot, C. et al. (2014). "Questionnaire-based survey on the distribution and incidence of canine babesiosis in countries of Western Europe.". Parasite 21: 13. doi:10.1051/parasite/2014015. PMC 3952654. PMID 24626325.
- Irwin, Peter. "Canine Babesiosis". Canine Babesiosis: 1144.
- Marvista Vet. "Babesia Infection in Dogs".
- "Babesia". Companion Animal Parasite Council.
- Irwin, Peter. "Canine Babesiosis". Canine Babesiosis: 1146.