The little pigs and the big bad
trypanosome
Lucas J Cunningham
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African Trypanosomiasis (Sleeping Sickness)
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Neglected Tropical Diseases, fatal if untreated
66 million people at risk in 36 African countries
Single cell parasites called trypanosomes
Transmitted by the bite of a tsetse fly
Causes serious disease in animals
Animal African Trypanosomiasis is responsible for a loss of U.S. $4.5 billion
per year across sub Saharan Africa
http://sitemaker.umich.edu/section003group6/impact_on_food_production_and_security
http://news.sciencemag.org/chemistry/2011/06/hitting-sleeping-sickness-where-it-lives
https://microbewiki.kenyon.edu/index.php/Membrane_proteins_as_mechanisms_of_immune_syste
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m_evasion_in_Trypanosoma_brucei
http://www.raywilsonbirdphotography.co.uk/Galleries/Invertebrates/vectors/Tsetse_Fly.html
Importance of Human African Trypanosomiasis (HAT)
Elimination 2020
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African Trypanosomiasis
There are three species in the brucei
group
• Trypanosoma brucei gambiense
• Trypanosoma brucei rhodesiense
South
Sudan
Gambiense (chronic)
sleeping sickness
• Trypanosoma brucei brucei
Rhodesiense (acute)
sleeping sickness
Images: http://www.lib.utexas.edu/maps/africa.html
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Can animals be a reservoir for gambiense?
• Past experiments have shown that pigs can be readily infected with
gambiense sleeping sickness
• Recently more importance has been placed on the possibility of animal
reservoirs influencing the transmission of the disease
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South Sudan
Pig Sampling in Uganda
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DRC
Gambiense
sleeping400
sickness
Rhodesiense
sleeping sickness
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Pig sampling method
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Analysis of pig blood for trypanosomes
General test for species of interest
Specific tests for species
• Highly sensitive
• Targets an area of DNA with
10,000 copies per parasite
• limited
• Targets an area of DNA with 1
copy per parasite
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Results
• 766 pigs were screened with the general test
Moyo
Arua
Site
Wiliffi
Duku
Tondolo
Ngalabia
Muttee
Drimveni
Inia
Perego
Opiro
Moipi
Kendi
Goopi
Kuleni
Total pigs
67
45
25
68
51
100
44
37
109
67
113
32
8
766
Infected
1
1
0
0
7
3
13
0
0
0
0
0
0
25
% infected
1.49
2.22
0.00
0.00
13.73
3.00
29.55
0.00
0.00
0.00
0.00
0.00
0.00
3.26
3.26% infection of T.
brucei sl overall
25 out of 400 were
infected, 6.25% in
Arua
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Map
29.6
3.0
2.2
13.7
1.5
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Do we have the big bad trypanosome?
• 25 positive samples re-screened for gambiense infections
• So far none of the pigs appear to be positive for the big bad trypanosome,
this could be good news for the farmers
• But…
• Not all the tests have been finished, issue with sensitivity, plus the pigs
still have animal trypanosomiasis
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Conclusions
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25 out of 766 pigs positive for trypanosomes of interest
20 out of 25 cases came from just two sample sites
The issue with the sensitivity needs to be ruled out
Secondary tests will need to follow to determine exact species present
Why is Arua a hot spot and why isn’t Moyo?
Is the big bad trypanosome still at large, not yet concluded
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Thanks to:
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Stephen Torr (LSTM and Warwick NTD)
Jessica Lingley (LSTM, Vector Group)
Ugandan field technicians
Ugandan vets
Ugandan farmers
Lee Haines (LSTM, Vector Group)
Johan Esterhuizen (LSTM, Vector Group)
Inaki Tirados (LSTM, NTD)
Hannah Betts (LSTM, Vector Group)
Liam Morrison (Roslin Institute, University of Edinburgh)
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Impact of finding gambiense in pigs
• Target and screen animals- requires more accurate field diagnostics
• Identifying areas of transmission- disease is very focal, mass screening of
the flies for the parasite maybe in conjunction with human and animal
screening
• Integration of controls- will probably require a number of control
strategies to eliminate the disease
• Disease eradication challenging
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