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The little pigs and the big bad trypanosome

Lucas J Cunningham

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African Trypanosomiasis (Sleeping Sickness)

• 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_securityhttp://news.sciencemag.org/chemistry/2011/06/hitting-sleeping-sickness-where-it-lives

https://microbewiki.kenyon.edu/index.php/Membrane_proteins_as_mechanisms_of_immune_system_evasion_in_Trypanosoma_bruceihttp://www.raywilsonbirdphotography.co.uk/Galleries/Invertebrates/vectors/Tsetse_Fly.html

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Importance of Human African Trypanosomiasis (HAT)

Elimination 2020

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African Trypanosomiasis

Images: http://www.lib.utexas.edu/maps/africa.html

South Sudan

Gambiense (chronic) sleeping sickness

Rhodesiense (acute) sleeping sickness

There are three species in the brucei group• Trypanosoma brucei gambiense

• Trypanosoma brucei rhodesiense

• Trypanosoma brucei brucei

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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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Pig Sampling in Uganda

Rhodesiense sleeping sickness

Gambiense sleeping sickness

DRC

South Sudan

400

366

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Pig sampling method

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Analysis of pig blood for trypanosomes

General test for species of interest• Highly sensitive• Targets an area of DNA with

10,000 copies per parasite

Specific tests for species• limited• Targets an area of DNA with 1

copy per parasite

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• 766 pigs were screened with the general test

Site Total pigs Infected % infectedWiliffi 67 1 1.49Duku 45 1 2.22

Tondolo 25 0 0.00Ngalabia 68 0 0.00Muttee 51 7 13.73

Drimveni 100 3 3.00Inia 44 13 29.55

Perego 37 0 0.00Opiro 109 0 0.00Moipi 67 0 0.00Kendi 113 0 0.00Goopi 32 0 0.00Kuleni 8 0 0.00

766 25 3.26

Results

3.26% infection of T. brucei sl overall

Aru

aM

oyo

25 out of 400 were infected, 6.25% in Arua

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Map

1.5

2.23.0

13.7

29.6

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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

• 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:• 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