Synonyms: Trypanosoma franki, T. wrublewskii, T. himalayanum, T. indicum, T. muktesari, T. falshawi, T. scheini, T. americanum, T. rutherfordi.
T. theileri occurs in the blood of cattle. It is worldwide in distribution. It is probably quite common, but is rarely found in blood smears. Crawley (1912) found it in blood cultures from 74% of 27 cattle around Washington, D. C. and Glaser (1922) found it in blood cultures from 25% of 28 New Jersey cattle. Neither found it in direct blood smears. Atchley (1951) found it in the blood of 1% of 500 South Carolina cattle.
T. theileri is relatively large, being ordinarily 60 to 70 u long, but forms up to 120 u long and smaller ones 25 u long often occur; those found by Levine et al. (1956) in an Illinois heifer were 34 to 40 u long exclusive of the flagellum. The posterior end is long and pointed. There is a medium-sized kinetoplast some distance anterior to it. The undulating membrane is prominent, and a free flagellum is present. Both trypanosome and crithidial forms forms may occur in the blood. Multiplication occurs by binary fission in the crithidial form in the lymph nodes and various tissues.
T. theileri is transmitted by various tabanid flies, including Tabanus and Haematopota. It reproduces in the fly intestine by binary fission in the crithidial stage.
T. theileri is ordinarily non-pathogenic, but under conditions of stress it may cause serious signs and even death. It has caused losses in cattle being immunized against rinderpest and other diseases, and has occasionally been accused of causing an anthrax-like disease. Carmichael (1939) found masses of T. theileri in the brain of a cow which had died with signs of "turning sickness" in Uganda.
T. theileri may also be associated with abortion, altho it has not proved that it causes this condition. Levine et al. (1956) found it in an Illinois heifer which had aborted, and Dikmans, Manthei and Frank (1957) found it in the stomach of an aborted bovine fetus in Virginia. Lundholm, Storz andc McKercher (1959) found it as a contaminant in a primary culture of kidney cells from a bovine fetus in California. This was further evidence that intrauterine transmission may occur.
Ristic and Trager (1958) found T. theileri in three Florida dairy cattle with depressed milk production; it was not found in cows in the same herd with normal milk production. The affected cows had a marked eosinophilia.
Since T. theileri is rarely seen in the blood, diagnosis ordinarily depends on cultivation. It can be cultivated in NNN and other media at room temperature. Ristic and Trager (1958) also cultivated it at 37 C in a blood-lysate medium. Both crithidial and trypanosome forms were present in their cultures. Lundholm, Storz and McKercher (1959) found that it grew well in tissue culture medium containing 10% lamb serum, but better if bovine kidney cells were present.
No treatment is known for T. theileri. Infections can be prevented by elimination of the tabanid vectors.