TRANSMISSIBLE FOWL LEUKOSIS 11 



the disease under natural conditions in which susceptible birds have been placed 

 in contact with diseased ones have been uniformly negative (Jarmai 99). 



Jarmai (97) demonstrated that the urine and feces from an infected bird were 

 not capable of producing the disease. Engelbreth-Holm (47, 49) was unable to 

 infect fowls by injecting whole leukotic blood into their stomachs by means of a 

 stomach tube. 



Relation of Ectoparasites 



The possibility that blood-sucking parasites may act as intermediary agents 

 in the transmission of fowl paralysis has received some attention. This aspect 

 was investigated in experiments by Ellermann (cited by Andersen and Bang 2) 

 with Cimex leticularis, by Andersen and Bang (2) with Dermanyssus avium, and 

 by Jarmai, Stenszky, and Farkas (105) with Argas species. All of these investiga- 

 tors obtained negative results. Recently, Gibbs (88) reported an experiment in 

 which there appeared to be transmission of "myeloleukosis" from diseased to 

 healthy birds by means of Dermanyssus gallinae with which the birds were in- 

 fested. This experiment was repeated after the animal quarters were cleaned and 

 the factor of the presence of mites removed with the result that there still was 

 apparent transmission of the disease to the healthy birds although a somewhat 

 smaller number became affected. Johnson (109) has reported the successful 

 transmission of the lymphomatosis agent with Dermanyssus gallinae acting as 

 an intermediate carrier. 



Although Jarmai, Stenszky, and Farkas (105) found the parasites {Argas 

 species) of no signifance in the infection of chickens in a natural way, they could 

 reproduce the disease in fowls by injecting material prepared from ticks which 

 had previously engorged themselves on a sick bird. They found, in this way, 

 that the agent of fowl leukosis would remain viable for 25 days in the body of 

 the parasite. Jarmai stressed the fact that these parasites could introduce but a 

 small quantity of infective material which would be received in the subcutaneous 

 tissues, a route not likely to result in successful inoculation (Engelbreth-Holm 

 47). It was also considered possible that the agent in the engorged tick would 

 lose its potency before a new host was attacked. 



Ratcliffe and Stubbs (167) noted that the transmissible agent of fowl leukosis 

 would survive at least three hours in the stomach of the mosquitoes, Ciilex pipiens 

 and Ades egypti. They were not able to demonstrate transmission of the disease 

 by alternating the feeding periods of these mosquitoes on leukemic and healthy 

 fowls. These workers likewise found that Dermanyssus gallinae would not act 

 as an intermediary transmitter of the disease. In their experience the trans- 

 missible agent contained in the mosquitoes and mites was inactivated in 24 hours. 



Transmission through the Egg 



Jarmai, Stenszky and Farkas (105) investigated the possibility of transmission 

 of the disease from a sick hen to chicks raised from the eggs laid by her during 

 her illness. Twenty chicks were hatched from such eggs. Two of these were 

 killed at the time of hatching to determine whether the agent was present in 

 their blood, twelve lived to be one year or more of age, and the others died of 

 intercurrent disease. None of the chickens showed evidence of leukosis and the 

 agent was not demonstrable in the day-old chicks. 



Experimental attempts to infect eggs during the incubation period have been 

 interesting. According to Jarmai, Stenszky, and Farkas (105), the transmissible 



