542 



NEOSPORIDIA 



fever, etc.; (2) by entry through an abrasion- — e.g., Molluscum con- 

 tagiosum ; (3) b}^ contact— ^.g., fowl pest; (4) by unknown methods 

 ■ — e.g., Novy's rat disease. 



Nature. — ^The nature of the viruses is unknown; some, especially 

 those spread by blood-sucking agents, are probably protozoal, but 

 others may be bacterial. 



Classification. — The filterable viruses may be divided into — 



1, Filterable viruses associated with no known organism. 



2. Filterable viruses associated with some known organism. 



I. Filterable Viruses associated with No Known Organism. 



Under this heading come the viruses of several diseases of im- 

 portance in tropical medicine — e.g., the virus of yellow fever, of 

 dengue fever, of pappataci fever, of typhus fever. 



Yellow Fever.- — -The virus is found in the blood only during the 

 first three days of the fever. It can pass through Berkefeld and 

 Chamberland B filters, and can be destroyed by heating to 55° C. 

 for ten minutes, or by a temperature of 24° to 30° C. for forty-eight 

 hours. It is conveyed by Stegomyia calopus after an interval of 

 twelve days from the time of the infective feed. 



Dengue Fever.- — -The virus is in the blood during the fever, and 

 can be filtered through Berkefeld filters impermeable to Micrococcus 

 melitensis. It is spread by Culex fatigans. 



Pappataci Fever.- — The virus exists in the blood during the first 

 day of the fever, and can be filtered through Berkefeld filters, and 

 is spread by Phlebotomus papatasii after an interval of seven days 

 from the date of the infective feed. 



Typhus Fever. — The virus exists in the blood, and can be filtered 

 through the coarser Berkefeld filters. It is destroyed by a tempera- 

 ture of 52° to 55" C; it is spread hyPediculus vestimentorum L. 



Verruga Peruviana.- — 'The experiments of Strong, Tyzzer, Brues, 

 Sellards, and Gastiaburu tend to show that the virus of this disease 

 is a filterable virus, and distinct from that of Oroya fever. It 

 appears to be similar in many respects to the virus of smallpox. It 

 can be inoculated successfully into monkeys, but only a modified 

 form of the disease appears, the lesions regressing in four to five 

 weeks (analogy with inoculated smallpox). It has also been 

 transmitted to rabbits and dogs. It has not yet been demonstrated 

 thsit Phlebotomus verrucarium or any other insect does transmit the 

 disease, but it is believed that some arthropod is the carrier. 



2. Filterable Viruses associated with Some Known Organism. 



Borrel has clearly shown that a minute flagellated organism 

 {Micromonas mesnili) exists in the filtrates of sheep-pox, and it is 

 quite possible that all filtrates contain these minute organisms, and, 

 further, there is reason to suppose that certain larger organisms 

 possess these minute forms in some stage of their life-cycle — e.g., the 

 organisms of trachoma, variola, and vaccinia. 



Bradford, Bashford and Wilson have described minute bodies 



