Volume IV 
JUNE, 1911 
No. 2 
THE PROBABLE MODE OF INFECTION AND THE 
MEl’HODS USED IN CONTROLLING AN OUTBREAK 
OF EQUINE TRYPANOSOMIASIS {MURRINA) IN THE 
PANAMA CANAL ZONE. 
By S. T. darling, M.D. 
Chief of Laboratory, Isthmian Canal Commission, Ancon, Canal Zone. 
The methods so successfully used in ridding Panama of yellow fever 
and delimiting malarial fever have been equally valuable in checking 
an epidemic of Equine Trypanosomiasis in the Canal Zone. 
In 1909 there broke out in the Commission corrals among some 
mules and a few work-horses a fatal trypanosomal disease which I have 
identified as Murrina or Derrengadera, the Panaman names for a fatal 
disease of Horses in this region. The corrals had been free up to this 
time from any disease of this kind since 1904, the date of the beginning 
of canal operations by Americans. 
The pathogenic agent, T. hippicwm, has been described elsewhere f 
My attention was called to the disease some months after its 
appearance and at a time when from its symptomatology it was 
regarded by the Veterinarians as “Swamp fever” or the “Infectious 
Anaemia of Equines,” a disease prevalent in some sections of the 
Western United States, of obscure etiology and whose mode of trans¬ 
mission is unknown. 
With the discovery of the trypanosome, infected animals were 
isolated, and work was begun to ascertain, if possible, the natural means 
of infection, by an examination of suspected biting Hies, ticks, bats and 
muscid Hies. The results of the investigation may be epitomized as 
follows: 
Apparently ticks were not responsible, for ticks were never found on 
mules or work-horses because they were never worked in localities 
s 
1 Bull, de la Societe de Pathologie Exotique, Paris, in. p. 381, 1910. American 
Veterinary Review, New York, xxxvii. p. 375, 1910. 
Parasitology iv 
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