﻿346 
  C. 
  F. 
  M. 
  SWYNNERTON. 
  

  

  The 
  disease 
  has 
  continued 
  to 
  exist 
  in 
  Kavirondo 
  ever 
  since 
  the 
  great 
  outbreak 
  

   on 
  the 
  Lake. 
  A 
  report 
  by 
  Dr. 
  Johnston, 
  dated 
  5th 
  May 
  1922, 
  states 
  that 
  in 
  middle 
  

   Kavirondo 
  a 
  case 
  or 
  two 
  is 
  present 
  in 
  practically 
  every 
  location, 
  though 
  the 
  majority 
  

   are 
  in 
  the 
  Lake 
  shore 
  areas, 
  and 
  I 
  was 
  told 
  by 
  himself 
  and 
  others 
  that 
  the 
  position 
  

   was 
  certainly 
  not 
  better 
  in 
  south 
  Kavirondo. 
  Infection 
  thence 
  represents 
  a 
  third 
  

   alternative. 
  

  

  Shoiild 
  our 
  trypanosome 
  be 
  gambiense, 
  actual 
  or 
  convertible 
  into 
  rhodesiense, 
  

   the 
  fact 
  that 
  the 
  disease 
  can 
  be 
  freely 
  carried 
  by 
  a 
  fly 
  of 
  the 
  morsitans 
  group 
  would 
  

   turn 
  the 
  position 
  in 
  Kavirondo, 
  if 
  it 
  should 
  continue, 
  into 
  a 
  menace 
  to 
  the 
  great 
  

   territories 
  to 
  its 
  south. 
  

  

  If 
  the 
  Parasite 
  is 
  T. 
  rhodesiense. 
  

  

  In 
  this 
  case, 
  which 
  seems 
  more 
  likely, 
  three 
  further 
  theories 
  of 
  origin 
  arise 
  : 
  

  

  (a) 
  that 
  it 
  was 
  introduced 
  into 
  Usukuma 
  as 
  a 
  human 
  trypanosome 
  by 
  the 
  movements 
  

   of 
  man 
  in 
  the 
  war, 
  for 
  example, 
  from 
  the 
  South, 
  in 
  Neumann's 
  incursion, 
  or 
  from 
  the 
  

   Congo 
  by 
  the 
  Belgians. 
  There 
  is 
  no 
  apparent 
  reason 
  why 
  T. 
  rhodesiense, 
  just 
  

   recorded 
  from 
  the 
  Sudan, 
  should 
  not 
  exist 
  in 
  the 
  appropriate 
  areas 
  in 
  the 
  Congo 
  ;* 
  

  

  (b) 
  that 
  it 
  had 
  been 
  present 
  all 
  the 
  time 
  as 
  a 
  specific 
  trypanosome 
  pathogenic 
  to 
  man, 
  

   which, 
  in 
  spite 
  of 
  the 
  distributional 
  evidence 
  to 
  the 
  contrary 
  obtained 
  in 
  the 
  war, 
  is 
  

   widely 
  spread 
  in 
  morsitans 
  areas 
  at 
  every 
  latitude 
  in 
  which 
  temperature 
  conditions 
  

   are 
  favourable 
  to 
  its 
  development, 
  but 
  tends 
  to 
  be 
  overlooked 
  so 
  long 
  as 
  cases 
  are 
  

   few 
  ; 
  or 
  (c) 
  that 
  it 
  is 
  simply 
  a 
  strain 
  that 
  may 
  arise 
  from 
  T. 
  brucei 
  of 
  game, 
  tempera- 
  

   ture 
  and 
  other 
  conditions 
  being 
  suitable, 
  in 
  any 
  place 
  in 
  which 
  the 
  latter 
  trypanosome 
  

   is 
  present 
  and 
  heavy 
  and 
  continuous 
  concentration 
  of 
  tsetse 
  is 
  taking 
  place 
  in 
  

   relation 
  to 
  man. 
  

  

  Whatever 
  theory 
  of 
  origin 
  is 
  correct 
  — 
  and 
  on 
  this 
  I 
  express 
  no 
  opinion 
  — 
  what 
  

   caused 
  the 
  infection 
  to 
  grow 
  into 
  an 
  epidemic 
  in 
  this 
  particular 
  place 
  ? 
  

  

  Duke 
  has 
  suggested 
  that 
  direct 
  transmission 
  may 
  play 
  the 
  all-important 
  part 
  — 
  

   we 
  cannot 
  perhaps 
  yet 
  say 
  the 
  only 
  part 
  — 
  in 
  producing 
  and 
  maintaining 
  a 
  virulent 
  

   strain 
  of 
  trypanosome 
  in 
  nature, 
  as 
  under 
  experimental 
  conditions, 
  and 
  I 
  have 
  shown 
  

   that 
  in 
  this 
  outbreak 
  a 
  position 
  favourable 
  to 
  direct 
  transmission, 
  as 
  also 
  probably 
  

   to 
  transmission, 
  direct 
  and 
  cyclical, 
  that 
  would 
  be 
  almost 
  confined 
  to 
  man, 
  existed 
  

   in 
  the 
  fact 
  that 
  the 
  human 
  population 
  was 
  being 
  specially 
  and 
  continuously 
  attacked 
  

   by 
  Glossina 
  as 
  a 
  result, 
  undoubtedly, 
  of 
  a 
  previous 
  destruction 
  of 
  game, 
  and 
  that 
  

   the 
  greatest 
  destruction, 
  and 
  therefore 
  the 
  greatest 
  concentration, 
  had 
  in 
  all 
  

   probability 
  coincided 
  rather 
  particularly 
  with 
  the 
  locality 
  (Usmao 
  and 
  Igombe) 
  

   in 
  which 
  the 
  outbreak 
  appears 
  first 
  to 
  have 
  assumed 
  serious 
  epidemic 
  form. 
  But 
  

   game 
  destruction 
  and 
  special 
  attacks 
  on 
  man 
  have 
  taken 
  place 
  locally 
  in 
  parts 
  of 
  the 
  

   territory 
  in 
  which, 
  nevertheless, 
  so 
  far 
  as 
  we 
  know, 
  no 
  outbreak 
  of 
  human 
  trypanoso- 
  

   miasis 
  has 
  followed. 
  

  

  Coincidental 
  factors 
  seem 
  to 
  complete 
  the 
  explanation. 
  Thus 
  in 
  1917 
  the 
  bush- 
  

   dwelling 
  Bagwe 
  (Wasukuma) 
  were 
  brought 
  into 
  contact 
  with 
  the 
  heterogeneous 
  

   collection 
  of 
  humanity 
  that 
  accompanied 
  the 
  Ikoma 
  pursuit 
  and 
  were 
  much 
  scattered, 
  

  

  * 
  While 
  correcting 
  the 
  proofs 
  of 
  this 
  paper 
  I 
  have 
  been 
  shown 
  by 
  Dr. 
  Newham 
  a 
  war-time 
  

   report 
  (I 
  believe 
  unpublished) 
  by 
  Wolff, 
  the 
  German 
  investigator, 
  in 
  which 
  the 
  following 
  passage 
  

   occurs: 
  "The 
  large 
  bodies 
  of 
  troops 
  and 
  porters 
  have 
  carried 
  infection 
  to 
  districts 
  formerly 
  

   unaffected. 
  I 
  discovered 
  three 
  sleeping 
  sickness 
  patients 
  in 
  Mwanza 
  District 
  among 
  a 
  small 
  

   number 
  of 
  Belgian 
  askaris 
  who 
  were 
  prisoners 
  of 
  war, 
  and 
  of 
  these 
  one 
  reported 
  that 
  he 
  was 
  

   infected 
  with 
  his 
  illness 
  and 
  had 
  already 
  been 
  treated 
  for 
  it 
  in 
  the 
  Congo 
  territory. 
  These 
  people 
  

   had 
  brought 
  their 
  sleeping 
  sickness 
  with 
  them 
  from 
  the 
  Congo 
  and 
  come 
  there 
  in 
  a 
  condition 
  to 
  

   infect 
  other 
  districts. 
  Alter 
  this 
  demonstration 
  it 
  must 
  be 
  admitted 
  that 
  a 
  considerable 
  number 
  

   of 
  the 
  Belgian 
  natives 
  will 
  have 
  carried 
  the 
  disease 
  through 
  a 
  large 
  portion 
  of 
  German 
  East 
  

   Africa. 
  All 
  prevention 
  and 
  control 
  have 
  ceased 
  since 
  the 
  beginning 
  of 
  the 
  war." 
  

  

  The 
  period 
  of 
  the 
  war 
  at 
  which 
  these 
  prisoners 
  were 
  taken 
  is 
  not 
  indicated 
  (Neumann 
  took 
  

   Belgian 
  prisoners), 
  nor 
  is 
  anything 
  said 
  of 
  the 
  trypanosome, 
  but 
  the 
  record 
  is 
  valuable 
  and 
  

   suggestive 
  nevertheless. 
  It 
  also 
  reinforces 
  my 
  argument 
  in 
  Sect. 
  XX. 
  

  

  