494 INFECTIOUS DISEASES DUE TO PROTOZOA 



site was first demonstrated in 1911 (Iowa outbreak) by 

 Dr. John R. Mohler of the Bureau of Animal Industry, 

 which conclusively established the identity of the American 

 with the dourine of Europe, Asia and Africa. 



Natural Infection. — Susceptible mares are infected by dis- 

 eased stallions during copulation, the urethral discharges 

 containing the causal trypanosomes. Likewise a mare 

 suffering from the disorder may infect a stallion while he is 

 serving her. A transmission by the stallion from a diseased 

 to a healthy mare, without the stallion himself becoming 

 infected, also occurs. The trypanosomes penetrate the 

 intact mucous membranes of the genital tract and enter the 

 blood. Insect transmission is probable, but so rare, if it 

 occur at all, as to be negligible. Dogs, cats, rabbits, rats, 

 white mice and sheep have been successfully inoculated. 

 Dogs die in two to three months after becoming greatly 

 emaciated. Rabbits emaciate and die in two to eight months, 

 while white mice succumb to general septicemia in three to 

 five days following intraperitoneal inoculation. 



Symptoms. — The period of incubation varies from five to 

 thirty days or longer (probably several months) . Following 

 the incubative period the local symptoms of the first stage 

 appear. 



Primary Stage. — In stallions there is swelling of the penis 

 first noticed in the glans but later involving the whole 

 organ. The prepuce becomes edematous, but is not sensitive 

 to the touch. The edema may involve the ventral abdominal 

 wall and scrotum. The testes may also swell. From the 

 urethra is discharged a thin, yellow, serum-like fluid which 

 drips away more or less continuously (in European outbreaks 

 the urethral discharge is thicker, more purulent). In three 

 to four days small vesicles appear on the penis. In twelve to 

 thirty-six hours the vesicles erupt, discharging a thin, yellow 

 fluid leaving behind raw ulcers which tend to coalesce with 

 those adjacent. The ulcers heal rapidly but leave behind 

 white,- non-pigmented, permanent scars. The stallion may 

 show strangury and increased sexual desire (frequent 

 erections). They may attempt to cover mares, but usually 

 full erection of the penis fails. The preputial and inguinal 



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