INFLUENZA OF THE HORSE 315 



aged horses.. Horses three to five years of age are most fre- 

 quently affected. One attack produces lasting immunity. 

 Horses which have had influenza may, however, take in- 

 fectious pneumonia, and vice versa. The infection is most 

 commonly taken in with the food and water. Infection via 

 respiratory tract is highly probable but not proven. 



Symptoms. — The period of incubation is usually less than a 

 week. A minimum period of one day and a maximum of ten 

 days is recognized. The initial symptoms in many cases are 

 moderately developed, but in the majority they are quite 

 intense. Usually the first symptoms noticed by the owner or 

 caretaker are loss of appetite, dulness, and marked languor. 

 The patient stands with head down, eyes closed, ears drooped, 

 appearing excessively fatigued. The gait is staggering, and 

 crackling of joints is heard when the patient is moved. 



The temperature is elevated (103° to 105° F.). It usually 

 drops by crisis on the second or third day. The pulse in the 

 earlier stages is relatively low compared with the fever, but as 

 soon as cloudy swelling of the heart begins it goes up to 60 to 

 100, and becomes irregular and weak. 



Eye Lesions. — Conjunctivitis appears early, and later kera- 

 titis and iritis (exudate in anterior chamber, contraction of 

 pupil, etc.). The blood is charged with bile pigment, hence 

 the conjunctiva assumes a yellowish, ochre, or a natural 

 mahogany color. Sometimes a phlegmonous conjunctivitis 

 with marked swelling and eversion of the eyelids occurs. 

 These symptoms generally rapidly subside, provided the 

 cases take the normal benign course. 



, Respiratory Trad. — Cough is usually present. It is gen- 

 erally strong and moist. Nasal discharge, at first clear but 

 later turbid and more profuse, is a constant symptom. The 

 submaxillary glands are swollen. The patient shows moder- 

 ate dyspnea; the respirations 20 to 25. Percussion normal. 

 Auscultation exaggerated, vesicular breathing and moist 

 rales. 



Digestive Tract. — Lost or impaired appetite; during the 

 fever increased thirst is noted. Usually symptoms of catarrhal 

 stomatitis and pharyngitis are present (coated tongue, warm, 

 congested mucous membranes; regurgitation of water through 



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