Babesia Canis

Synonyms: Pyrosoma bigeminum var. canis, Piroplasma canis, Babesia rossi, Rossiella rossi, Babesia vitalii, Rangelia vitalii.

Disease: Canine babesiosis, canine piroplasmosis, biliary fever, malignant jaundice, nambiuvu.

Hosts: Dog, wolf, side-striped jackal (Thos adustus), black-backed jackal (T. mesomelas). In addition, the red fox, and jackal (Canis lupaster) have been infected experimentally. However, Thomas and Brown (1934) were unable to infect the cat even after splenectomy.

Location: Erythrocytes.

Geographic Distribution: North America (Florida, Virginia, Texas, Puerto Rico), Central America, South America, southern Europe, USSR, Africa, Asia.

Prevalence: This parasite is common in many tropical regions. It is uncommon in the U.S., but has been reported from Florida by Eaton (1934) and Sanders (1937), from Texas by Merenda (1939) and from Virginia by Grogan (1953).

Morphology: This is a large form. The trophozoites are piriform and 4 to 5 u long, or amoeboid and 2 to 4 u in diameter. They generally contain a vacuole. Multiple infections of the erythrocytes are common. In addition, masses of 30 to 100 "merozoites" have been described for Rangelia vitalii (a synonym of B. canis) in the endothelial cells of the lungs and kidneys. However, these were much more likely agglomerations of organisms in the small blood vessels.

Life Cycle: The life cycle has been described above (p. 287). The vectors are Rhipicephalus sanguineus thruout the world, Dermacentor marginatus (syn., D. reticulatus), D. pictus andD. venustus in Europe, D. pictus and Hyalomma marginatum in the USSR, and Haemaphysalis leachi in South Africa. Transmission takes place thru the egg in all but D. pictus, and stage-to-stage in this species, R. sanguineus and H. leachi.

Pathogenesis: The severity of infections with B. canis varies considerably with the strain. In some localities it is a comparatively mild disease, while in others it may be highly pathogenic. Both young and old dogs are susceptible. In countries where the disease is endemic, the indigenous dogs usually become infected while young and do not suffer such a severe disease, while the mortality is high among imported dogs.

The incubation period is 10 to 21 days in naturally infected dogs. The first sign of disease in acute cases is fever. This is quickly followed by marked anemia, with icterus, inappetence, marked thirst, weakness, prostration and often death. Hemoglobinuria is sometimes but not usually present.

In chronic cases the fever is not high and seldom lasts more than a few days and there is little icterus. Anemia is severe, and the dogs are listless and become very weak and emaciated.

Canine babesiosis is protean in its manifestations, and may take on many different clinical forms. Involvement of the circulatory system may produce edema, purpura and ascites; there may be stomatitis and gastritis; and involvement of the respiratory system causes catarrh and dyspnea. Keratitis and iritis are seen if the eyes are affected, and myositis and rheumatic signs if the muscles are involved.

Central nervous system involvement causes locomotor disturbances, paresis, epileptiform fits, etc. (Malherbe and Parkin, 1951; Malherbe, 1956). A cerebral form of the disease was described by Purchase (1947) in which parasites were rare in the blood but abundant in the brain capillaries. This tendency to clog the capillaries is common to many species of Babesia. In cerebral babesiosis the signs may be confused with those of rabies.

In South America, the disease is called nambiuvu, meaning "bloody ears" in the Guarani language. As the name suggests, it is a hemorrhagic disease. There is bleeding from the edges of the ears and from the muzzle, particularly in young dogs in summer. There are also internal hemorrhages.

The spleen is enlarged, with dark red, soft pulp and prominent splenic corpuscles. The liver is enlarged and yellow, with pathological changes ranging from congestion to centrilobular necrosis (Gilles, Maegraith and Andrews, 1953). The heart is pale and yellowish. The kidneys are yellowish, and show considerable nephrosis or nephritis histologically. The muscles are pale and yellow, and the fat and mucous membranes may be yellowish. There may be a variable amount of fluid in the pleural, pericardial and peritoneal cavities. Small hemorrhages are sometimes present on the heart, pleura, bronchi and intestines. There is less icterus in chronic than in acute cases.

Immunity: Recovered animals remain infected in a state of premunition. This persists for life if they are kept in an endemic area, but the parasites die out in a year or more in the absence of reinfection.

Diagnosis: In endemic areas, symptoms of fever, anemia, and icterus, with or without hemoglobinuria, are suggestive of canine babesiosis. The diagnosis can ordinarily be confirmed by finding the parasites in stained blood smears. They are often present in capillary blood when they cannot be found in venous blood.

Treatment: Trypan blue is effective against B. canis. It is injected intravenously, the dosage for a 35-pound dog being 4 to 5 ml of a 1% solution. Acriflavine has also been recommended. It is injected intravenously in 0.1 to 2.0% solution, the dosage being 1 to 3 ml of the drug per kg body weight. Acaprin is safer than acriflavine. It is injected subcutaneously in 0.5% solution at the rate of 0.05 ml per kg body weight. Phenamidine has given excellent results. It is injected subcutaneously in 5% solution at a dosage rate of 10 mg per kg (i. e., 0.2 ml per kg); a single dose is usually effective, but it may be repeated the next day.

Prevention and Control: As for other Babesia infections, these depend upon tick control.