This study was conducted to understand the occurrence, diversity and epidemiology of tickborne
diseases (TBDs) in a transhumant pastoral area of Karamoja Region, Uganda. We used
participatory epidemiology (PE), involving focus group discussions (n = 24) with livestock
keepers, 30 key informant interviews, review of previous surveillance data, clinical
examinations, and laboratory confirmation of cases of TBDs, to define and prioritise cattle
diseases, evaluate current control activities, and identify constraints to the control of TBDs.
The livestock keepers regarded TBDs, particularly East Coast fever (ECF) and anaplasmosis, as
the most important health problems in their cattle, based on morbidity and mortality rates,
rates of transmission, treatment costs, difficulty in accessing the correct treatment, difficulty
to control, and inadequate knowledge to manage the diseases.
The main constraints to the
control of TBDs were inadequate knowledge, inadequate veterinary services and limited
availability of drugs. Hand picking of ticks was done by all pastoralists while hand spraying
was done with under-strength acaricides, often at irregular intervals and with little acaricide
wash. We determined the endemic status of TBDs in 20 randomly-selected cattle herds by
estimating the proportion of annual ECF and anaplasmosis cases in different age groups of
cattle using participatory approaches and clinical examinations, determining the diversity and
abundance of ticks (161 cattle in 20 herds), and establishing the seroprevalence of antibodies to Theileria parva and Anaplasma marginale among cattle (n = 397 in 20 herds).
examinations and informant interviews showed that TBDs affected all age groups of cattle.
Two-thirds of the cattle were infested with moderate (37.3%, 11-50 ticks) to abundant (28.6%,
> 50 ticks) numbers of ticks. Out of the 10,923 ticks collected, Rhipicephalus appendiculatus
(54.4%) was the most abundant species followed by R. decoloratus (17.7%), Amblyomma
variegatum (12%) and A. lepidum (11.6%). We collected tick species that are either rare in
Uganda (A. lepidum, Hyalomma truncatum, A. gemma) or were not known to be present in
the country (R. pulchellus). The true seroprevalence of antibodies to A. marginale was high
(95.1%, 95% confidence interval [CI] 91.3% - 98.5%), while that of T. parva was low (16.5%,
95% CI 12.9% - 19.6%). We determined the presence of tick-borne haemoparasites among
cattle and the prevalence of infections using reverse line blot (RLB) hybridisation and
quantitative real-time polymerase chain reaction (qPCR), and characterised Theileria and
Babesia species by sequence and phylogenetic analyses of the full-length 18S rRNA gene. The
RLB hybridisation assay demonstrated the presence of tick-borne haemoparasites in most
cattle (99.6%), mostly as mixed infections (97.5%). The most frequently-detected species
were Theileria mutans (88.3%, 95% CI: 84.6-92.1%), A. marginale (73.8%: 68.3-79.2%), T.
velifera (71.3%: 65.8-76.7%) and Anaplasma sp. Omatjenne (63.3%: 57.5-68.8%). Other
virulent pathogens, namely Babesia bigemina (5.0%) and T. parva (2.9%), were also detected
with RLB, but Ehrlichia ruminantium was not detected. The proportions of qPCR positive
samples were 82.9% (A. marginale), 12.1% (A. centrale), 3.3% (T. parva), and 1.7% (E.
ruminantium). Variations (5 to 9 nucleotides) in the 18S rRNA gene sequences of B. bigemina
were identified as compared with previously published sequences.
We assessed the 16S rRNA
gene phylogeny of Anaplasma species from cattle and analysed the msp1α gene sequences
of A. marginale to identify genotypes. There was genetic heterogeneity within A. marginale
in cattle in the study area. Most A. marginale sequences (16/19) were closely related (99-
100% identities) and clustered with A. marginale strain Veld from cattle in South Africa, with
strong bootstrap support, while three sequences clustered (100% identity) with A. marginale
strain from Virginia, USA. The A. centrale sequences were closely related (100% identity) and
clustered with the Israel vaccine strain. We found four different kinds of MSP1a tandem
repeat sequences (UP39-F-M2-3) that correspond to one A. marginale strain unique to
Uganda. One tandem repeat (UP39) was unique to Karamoja cattle. The findings from this study provide knowledge on the diversity and epidemiology of TBDs, which can be used to
support diagnosis and strategic control of TBDs, and consequently improve cattle productivity
and the livelihoods of pastoralists. More effective control and prevention measures against
ticks and TBDs should urgently be implemented in the region. There is need to facilitate and
promote immunisation of cattle against ECF. Given the scarcity of veterinarians in the region,
the activities of community-based animal health workers [CAHWs] should be strengthened.
The local governments in Karamoja Region should facilitate a more favourable business
environment to attract private companies, who could scale-up veterinary drug supplies to the
region. Pastoralists should be sensitised to improve their ecological knowledge of the
seasonal activity of ticks for strategic tick control.