DIFFERENTIAL ])IAGNOSIS 505 



renal connective tissue and mesentery ; swelling of the lymph 

 glands ; yellowish serous exudates in the larger cavities of the 

 body and imperfect coagulation of the blood. One or all of 

 these changes may appear in a single animal. 



§ 390. Differential diagnosis. Influenza must be dif- 

 ferentiated from strangles and contagious pneumonia. The 

 differentiation between pleuro-pneumonia and influenza is 

 difticult only at the beginning, when merely general symp- 

 toms, such as fever, loss of appetite and weakness are pre.sent. 

 It should be mentioned that the two di.seases may affect the 

 horse simultaneously. When the skin is greatly .swollen, 

 influenza may resemble petechial fever, from which it can, 

 however, verj- soon be distinguished b\' the ab.sence of 

 petechiae, by the mildness of its course and its greater conta- 

 giousness. In case of strangles, the lesions in the lymphatics 

 may serve as distinguishing characters. If ab-scesses are in 

 evidence the finding of the streptococcus of strangles would be 

 quite conclusive. It would be positive providing streptococcus 

 equi could readih- be distinguished from the pyogenic 

 streptococci. 



With these diseases, a diagnosis, save in the more typical 

 forms, is difficult. Without a definite, recognizable, etiologi- 

 cal factor or other exact tests, a positive diagno.sis in doubtful 

 cases can not be made. 



REFERENCES 



1. LiGNiERES. The etiology of equine influenza or infectious 

 pneumonia. Joiir. of Coinp. Path, and Thera., \ o\. XI (189S), p. ,312. 



2. M'Fadvean. Influenza of the horse— what is it? Jour, of 

 Camp. Path, and Thera., \o\. II (1889), p. 105. 



3. Marsden. Influenza. The Vet. four. New series, \'ol. II 

 (19CO), p. 315. (M. describes three forms, (i) catarrhal fever, (2) 

 bilious fever, (3) epizootic cellulitis. ) 



4. Nelson. Influenza. Bulletiu 22. State Agric. F.xper. Sta- 

 Jiofi, Washington. 1896. 



