Animal Susceptibility to Trypanosoma Hippicum, the Equine Trypanosome of Panama

With Special Reference to Cattle as an Unharmed Host and Probable Reservoir of Importance

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  • Gorgas Memorial Laboratory, Panama, R. de P.


  1. 1.A study has been made of animal susceptibility to the equine trypanosome of Panama (T. hippicum) using as many wild and domestic animals as could be collected that are found in contact with horses and mules in the stable, pastures or on the trails.
  2. 2.The only animals in the series studied that disclosed a spontaneous infection with T. hippicum were the horse, mule and cattle.
  3. 3.Cattle that had ranged with a herd of horses and mules during an epidemic of this equine trypanosomiasis were examined a few months after the last case had appeared. The blood films of the cattle did not reveal trypanosomes but the use of 2 to 4 cc. of blood injected into the peritoneal cavity of a guinea pig disclosed the fact that 4.5 per cent of the cattle were light carriers of T. hippicum. The strain recovered from the cattle developed the usual clinical picture of murrina in the two horses tested and killed them in the usual period of time. A calf was experimentally given the infection and was positive to guinea pig inoculation over a period of about four months. It developed no symptoms and recovered spontaneously.
  4. 4.Other susceptible animals in the series capable of carrying a light infection a long time and ending in a spontaneous recovery were the hog, sheep and goat.
  5. 5.Susceptible animals in the list that ran a prolonged course ending in death were the domestic cat, the white tailed deer, the brocket deer, the collared peccary or wild hog.
  6. 6.Most wild and domestic animals can be experimentally infected and killed in a few weeks. The chicken was the only refractory experiment in the series.
  7. 7.This form of trypanosomiasis is distinctly a disease of the solipeds, particularly of the horse and mule. The fact that cattle can carry T. hippicum for a long period of time without injury and that cattle range in large numbers with horses and mules at night as well as day throughout the Republic makes these animals probably the most important reservoir in maintaining the presence of the disease in our region. The vampire bat feeds with equal freedom on equine and bovine animals and they live for almost a month after they acquire the infection and suffer no loss of appetite for blood meals until within a few hours of death.