Etiology, Auatouiical Changes, Symptoms. 841 



themselves at night to chickens and suck their blood. If the 

 blood contains spirochaetes, they are found for 3 to 4 days 

 in the digestive canal of the ticks, whereupon they disappear 

 from there, but they may remain infectious for a longer time, 

 according to Nuttall even after six months. If they are kept 

 at 35° C, the parasites multiply in their bodies, and after 4 

 to 5 days they may be found in the excretory duct of the salivary 

 gland of the ticks (Borrel & Marchoux). 



Anatomical Changes. In birds dead with the disease the 

 spleen is considerably enlarged and swollen, the liver swollen, 

 showing fatty degeneration and focal necrosis ; the heart muscle 

 also shows at times fatty degeneration and the epicardium is 

 covered with fibrinous membranes. No spirillae are found in 

 the blood. 



Symptoms. The incubation is in chickens 7 to 9 days after 

 placing infected ticks upon them ; spirochaetes may however be 

 demonstrated in the blood as early as from the fifth day on 

 (Marchoux & Salimbeni, Uhlenhuth & Gross). 



The symptoms consist in inappetence, rise of temperature 

 as high as 42.5-43° C, marked weakness and somnolence, pale- 

 ness of the comb, diarrhea and emaciation, with which in some 

 cases paralysis of the legs becomes associated. (Mohn observed, 

 even before the appearance of spirochaetes in the blood, the 

 feet swollen and the toe turned under and backwards.) 



After the somnolence has reached a high degree, the crisis 

 sets in 1 to 2 days later, the comb taking on a bluish-red colora- 

 tion, the temperature falls, and soon death follows, usually 

 under severe convulsions or recovery commences. Sometimes 

 however this is only apparent, as the paralysis of the legs in- 

 creases and gradually extends to the wings, the birds become 

 greatly emaciated, and finally die with a few rare exceptions 

 (chronic form). 



According to Nuttall the spirochetes are totally or mostly destroyed 

 by bactericidal and agglomerating substances after having multiplied 

 for a time in the blood. The more resistant, and therefore the surviving 

 parasites are then the cause of the supervening chronic affection. Serum 

 of birds which have recovered from one attack, destroys in test tube 

 experiments the spirochetes of the first attack, but not those of later 

 attacks. The appearance of parasiticidal substances in great quantities 

 in the blood before the crisis is reached has also been demonstrated by 

 Gabritschewsky and Uhlenhuth. 



By microscopical examination spirochaetes may be demonstrated in great 

 numbers in fresh blood- pre])arations made with physiological salt sohition until the 

 appearance of the crisis, but later, and also in animals dead of the disease, they are 

 no longer present. 



The duration of the disease in the more frequent acute 

 cases is mostly 4 to 5, in the chronic cases 8 to 15 days. 



