176 OTHER SPOROZOA 



lymphatics and ultimately into the muscles. Crawley has re- 

 cently described in Sarcocystis muris of mice what he interprets 

 as sexual differentiation of the spores and fertihzation within 

 18 hours after the spores have been ingested by mice. Crawley 

 believes the Sarcosporidia to be closely allied to the Coccidia, and 

 suggests that there may be an unrecognized stage of development 

 in a carnivorous animal. It is quite e\'ident from the various 

 hypotheses and speculations mentioned above that there is much 

 yet to be learned about these enigmatic parasites. 



Only a few scattered cases of Sarcosporidia in man have been 

 recorded, and these may be looked upon as purely accidental. 

 The parts affected have been the muscles of the heart and larynx. 

 Many speculations as to how these infections occurred have been 

 made, but nothing definite is known about it. It is probable 

 that the human infections are due to Sarcocystis muris, a species 

 which produces a very fatal disease in mice, and infections may 

 have been due to contamination of food or water with the ex- 

 crement of infected mice. The use of meat of Indian buffaloes 

 infected with another species, Sarcocystis tenella bubali, seems to 

 have no injurious effect on man, but ingested spores cause ir- 

 regular fever. 



Oroya Fever 



The Disease. — Since at least the time of the Incas, Peru has 

 suffered from a strange disease which has swept over the country 

 from time to time in the form of frightful epidemics, some of 

 which have cost thousands of Uves. One of the severest re&ent 

 outbreaks occurred among the workmen building the Peruvian 

 Central Railway between Lima and Oroya and it is estimated 

 that at least 7000 individuals died in it. In 1906 at least one- 

 tenth of 2000 workmen employed building tunnels and bridges 

 on the Central Railway died of the fever, and one bridge in par- 

 ticular, which was the scene of a great many deaths from the dis- 

 ease, has come to be known as the Oroya Fever Bridge (Fig. 53). 



The disease is at present endemic in the deep cleft canyons or 

 quebradas (Fig. 53) characteristic of the west face of the Andes, at 

 an elevation of between 2500 and 8000 ft., but it is probable that it 

 has a wider distribution than is now supposed. It shows a marked 

 seasonal prevalence, most of the cases occurring from January to 

 April, especially toward the close of the warm, rainy season. 



