204 TROPICAL MEDICINE AND HYGIENE 



clinically identical. The sudden access of high fever, 

 the headache, pains in the back and limbs, prostration, 

 thirst, and vomiting are as characteristic of tick fever as 

 of relapsing fever, as also the sudden crisis with profuse 

 sweating, followed by an apyrexial period, and this again 

 by one or 'more relapses. Enlargement and tenderness 

 of the liver and spleen are symptoms common to both 

 diseases, and herpes and epistaxis are frequently met with 

 in both. Tick fever differs from relapsing fever chiefly in 

 that the duration of attack is usually shorter, four days or 

 less instead of seven, with comparatively longer apyrexial 

 intervals and more frequent relapses. Diarrhoea is the 

 rule in tick fever, while constipation is almost always a 

 marked symptom of the early stage of relapsing fever. 

 Jaundice is rarer and iritis commoner than in Indian 

 relapsing fever. 



A slight degree of bronchitis is common and pneu- 

 monia is also met with. As in relapsing fever, spirochaetes 

 are usually found in the blood of patients suffering from 

 tick fever only during the pyrexial period. Of the two 

 diseases tick fever is the less severe, and death is rare 

 among persons who were in good health previous to 

 attack. It is said to be more severe in Europeans than 

 negroes, this probably depending upon partial immunity, 

 or tolerance, resulting from previous attacks in the latter. 

 Facial paralysis is not uncommon after an attack. 



The incubation period of tick fever is commonly about 

 five days, but may be shorter or longer, the duration 

 perhaps depending upon the severity of infection. 



Diagnosis. Before the discovery of the spirochaeta in 

 the blood many cases of tick fever were considered to 

 be suffering from malaria, pneumonia, or other diseases. 

 As in the case of relapsing fever, a correct diagnosis is 

 often impossible without the demonstration of the spiro- 

 chaete in the blood. From what has been said of the 

 symptoms of the disease, as well as of the morphology 

 of the parasites, it is obvious that the differentiation of 

 tick fever or relapsing fever may sometimes be impossible 

 without resort to experimental inoculation of animals. 



