|dc.description.abstract||Over the past two decades movement of cattle towards the north of Uganda has enabled
the Trypanosoma brucei rhodesiense focus in south-eastern Uganda to spread into
previously unaffected districts. This thesis brings together important epidemiological
data regarding the impact of mass cattle drug treatment on the point prevalence of
several different species of trypanosome in a newly endemic area of human sleeping
sickness. Crucially the findings illustrate mass drug treatment is effective in reducing
the prevalence of T. b. rhodesiense in cattle, thus minimising the reservoir potential of
these animals in the epidemiology of human disease.
During 2006 a control programme was launched to halt the northward spread of this
zoonotic parasite. This programme, entitled ‘Stamping Out Sleeping Sickness’ (SOS)
proposed to reduce the prevalence of Human African Trypanosomiasis (HAT) in the
newly affected districts by reducing the prevalence of this parasite in the main animal
reservoir of infection – domestic cattle. Cattle were mass treated using trypanocides to
Previous work demonstrated the prevalence of T. brucei s. l. and T. b. rhodesiense in
cattle was higher in the districts of Dokolo and Kaberamaido than in the other SOS
intervention districts (Selby 2011). To determine whether animals in these areas were
also exposed to pathogenic cattle trypanosomes samples were screened for the presence
of T. vivax and T. congolense savannah using PCR. Chapter three of this thesis
determined the prevalence of these trypanosomes in cattle in these districts. Before
treatment had taken place the prevalence of T. vivax was 2% (4/200, 95% CI 3.57 –
0.12%) in Dokolo and 7.3% (21/310, 95% CI 10.17 - 4.24 %) in Kaberamaido. The
prevalence of T. congolense savannah at baseline was 3.5% (7/200, 95% CI 7.08–1.42
%) in Dokolo and 9.1% (21/230, 95% CI13.6–5.7 %) in Kaberamaido. Monitoring was
conducted three, nine and 18 months post treatment and both pathogens were detected
at all time points. The impact the treatment had on point prevalence varied by
trypanosome species and between the two districts.
Several clusters of villages in Dokolo and Kaberamaido continued to report cases of
HAT after the initial SOS intervention due in part to their proximity to livestock
markets (Batchelor et al., 2009). In 2008 re-treatment of these ‘high risk’ areas was
undertaken. Monitoring was performed before and six months after treatment. Cattle
blood samples were collected at 20 village sites from ten ‘case-positive villages’ (from
which human sleeping sickness cases had been reported six months prior to June
2007) and from ten ‘case-negative villages’ (no reported human sleeping sickness cases
six months prior to June 2007). These samples were screened for all of the
aforementioned trypanosomes using species specific PCR protocols.
Chapter five details the results of this screening, and assessed whether re-treatment in
Dokolo and Kaberamaido was effective in reducing the prevalence of trypanosomiasis.
The re-treatment had a dramatic effect, significantly reducing the point prevalence of
overall trypanosomiasis in the 20 villages screened from 38.1% (95% CI = 40.5 –
35.79%) at baseline to 26.9% (95% CI 28.96 – 24.97, p < 0.0001) at six months.
Looking at each species separately, point prevalence of three out of four detected
species of trypanosome fell significantly, including T. b. rhodesiense, which was
reduced to 25% of its baseline prevalence.
Finally the two SOS treatment cycles were compared both statistically and spatially
with emphasis on trends at village level and the occurrence of mixed infections.||en