SURRA 375 
are outside the animal body and in a dry state, they are killed or 
rendered inert by prolonged atmospheric action. 
The period of incubation seems to be liable to great variation. It 
may be put from four to eight days after inoculation or ingestion of 
blood taken from an animal suffering from surra. It appears from 
Lingard’s investigation that it may be prolonged to thirteen days, if 
the blood used for inoculation has been taken from a dead animal. 
Means of transmission. It was formerly believed that surra was 
transmitted by ingestion of infected food or water. Lingard stands 
almost alone in the belief that infection can take place through healthy 
mucose. It is reported that carnivora have contracted the disease by 
eating blood and meat from infected animals. 
The demonstrated natural methods of transferring the virus from 
infected to non-infected animals is by means of insects, especially the 
biting flies. Of the flies, the tsétsé-fly (Glossina morsitans) is reported 
to be the most important. Musgrave and Clegg conclude concerning 
the réle played by flies in transmitting this disease that “it has thus 
far been conclusively shown that the tsétsé-fly (Glossina morsitans), 
at least one other variety of Glossini, Stomoxys calcitrans, Musca 
brava (?), Taon, and at least one variety of Tabani transmit the virus. 
All other biting insects have been looked upon with suspicion, but 
absolute proof of transmission by them has not been furnished.” 
The theory as to the method of transferring the parasite is that it is 
purely mechanical, although some have thought the trypanosome 
passed through one phase of its life cycle in the fly. Mohler and 
Thompson state that the breeze fly, Labanus atratus, was the carrier 
of the trypanosome in the quarantined India cattle in New York in 
1906. 
In 1901, surra was introduced into the Island of Mauritius by an 
importation of Indian cattle and from 70 to 80 per cent. of the native 
cattle died of it. Mitzmain found Tabanus striatus to be the carrier 
in the Philippine Islands. 
The spread of the disease from one locality to another is caused by 
the introduction of cattle carrying the parasite, although themselves 
but slightly susceptible. 
Symptoms. The symptoms as given by Lingard are as follows: 
“The chief symptoms are the occasional appearance of an urticarial 
eruption, generalized or localized, closely following the first rise of 
temperature, but which may make its appearance at any time during 
