TEXAS FEVER. 685 



According to Smith and Kilbourne, numerous minute 

 motile forms (coccus-like bodies) penetrate the corpus- 

 cles and eventually reach the pear-shaped form. The 

 breaking up of the adult pear-shaped parasites into such 

 small forms has not been observed. 



A characteristic symptom of Texas fever is the pro- 

 nounced hemoglobinuria which has given to the disease 

 the additional name of hemoglobinuric fever. 



The disease is transmitted by means of a tick (Boophi- 

 lus lovis). The six-legged larvae fill themselves with 

 blood, and in about eight days have been changed into 

 eight-legged nymphse. In eight days more they have 

 changed into fully-formed sexual animals, and, after 

 filling themselves with blood and after having been im- 

 pregnated, they drop off the cattle and lay their eggs. 

 Larvae hatch from the eggs in from 3 to 4 weeks, and 

 the former are again ready to attach themselves to 

 cattle (cited from Kossel). Inasmuch as infected ticks 

 transmit the parasites to their offspring, the bites of the 

 larvae are able to give rise to the disease in cattle. A 

 mature tick may deposit from 2,000 to 4,000 eggs. It 

 has not been possible to transmit the disease to other 

 species. 



The disease is endemic in the southwestern states, Transmissioi 

 and the cattle in that region are supposed to acquire an 

 immunity similar to that described by Koch in relation 

 to malaria. Presumably the cattle first acquire the dis- 

 ease when they are young, and those which withstand it 

 show resistance to the infection in later life. Cattle 

 from uninfected districts are more susceptible than those 

 coming from localities in which the disease is endemic, 

 and the latter even when apparently healthy may intro- 

 duce the disease into new herds. This is done through 

 transportation of the ticks. ^^- 



Partially successful attempts at active immunization 

 have been made, and in Australia this is practiced on 

 a fairly extensive scale. Five to ten cubic centimers of 

 blood, taken from an infected animal, during the course 

 of the disease or after recovery has been established, are 

 injected into non-immune cattle. The disease is thereby 

 reproduced in the latter with typical parasites in the 

 blood. If the blood is taken from animals which have 



