34 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
(C) In Gambia there is an undoubted trypanosome disease in horses which is 
characterized, in its first stage, by the absence of obvious symptoms ; and 
later, by fever, emaciation, and weakness. The course of this disease may 
be chronic and death delayed for a long period. 
We have a horse, in good condition, under observation in Liverpool, which was first found to be naturally 
infected on October 30, 1902. A letter, dated January 18, 1904, from an officer in Gambia, says that 
his horse, found naturally infected in April, 1903, ' could not be better, and is in excellent condition.' 
This Gambian horse disease seems to present a striking analogy to the human trypanosome disease 
seen in the Congo. The dull, listless expression, the weakness, the wasting and lack of energy, the 
irregular elevation of temperature, the frequent disappearance of the parasite from the peripheral blood 
(to ordinary examination), and the chronic course of the disease, are features characteristic of both 
infections. The similarity seems to us to be a point in favour of the casual relation of trypanosomes to 
Congo sleeping sickness. 
(D) The sleeping sickness of the Congo is known to have a long latent period. 
Symptoms are said to have developed 111 some cases two to five years after 
leaving an infected locality. 1 
It is interesting to note that natives may be infected with trypanosomes for 
many months without showing signs of illness. 
We have just heard that a Gambian native in whose blood trypanosomes were seen over a year ago 
is still in the very best of health. 
Dr. Zerrim, State Physician at Boma, has just sent us a report on cases observed by us in Boma 
during October last. His report is based on either his own observations or on the statements of heads 
of departments in those instances in which the cases had passed from his care. The report on five 
cases is indistinct or vague. Five had been in perfect health during the whole six months. Three have 
had surgical troubles, but are now well. One has had persistent diarrhoea, but has quite recovered and 
has been sent to the Upper Congo. Two cases have died of pneumonia, and the remaining four, only 
one of whom was in perfect health when we saw them, show slight oedema, lack of energy, or some other 
ailment. In none is there any suspicion of sleeping sickness. 
(£) Europeans 1 ' ! ' + infected with Trypanosoma gambiense show symptoms which 
are quite comparable with those observed in uncomplicated trypanosome 
infections of Congo natives. 
(F) In Gambia, where cases of sleeping sickness are rarely seen (Dr. M. Forde, 
Principal Medical Officer at Bathurst, stated that perhaps one case a year 
came under his care), only six out of one thousand odd natives were found 
to be infected, 5 by the examination of fresh cover-slip preparations. In an 
almost exactly equal number of a similar class of natives examined in the 
same way in the Congo, forty-six have been infected In Uganda, where 
the disease occurred in epidemic form, the percentage of infection among 
the general population was still higher. 6 
1. Guerin, Archives de Mcdecine, VI e series, vol. 14, Paris, 1869. 
2. Manson, Brit. Med. Jour., March 28, May 30, 1903. 
3. Dutton, Todd, Christy, Brit. Med. Jour., January 23, 1904. 
4. Broden, Les injections a Trypanosomes au Congo chez 1'homme et les animaux. {Extrait du Bulletin de la Soc. d'etudes 
Colonia/es, Fevr., 1904). 
5. Dutton, Todd, Bid. 
6. Reports of the Sleeping Sickness Commission, Royal Society. 
