Vector-borne diseases, (VBD), are amongst the most important constraints to animal
production in tropical and sub-tropical regions of the world, including sub-Saharan
Africa, (SSA). Losses due to these diseases are estimated to be up to 25% of the
region's annual livestock production total. Some of the diseases are also zoonotic and
therefore contribute to human health problems. The most important VBD are caused by
the protozoa: Anaplasma, Cowdria, Babesia, Theileria and Trypanosoma parasites.
Anaplasma, Cowdria, Babesia and Theileria are transmitted by ticks while
trypanosomes are transmitted by tsetse flies in humans and animals in Africa. Control of
these diseases in SSA is non-sustainable, mainly because of ineffective disease
surveillance, poor diagnostic capacity and inadequate control measures largely due to
economic constraints ofthe affected governments.
Two of the most commonly used diagnostic methods, microscopy and molecular
techniques for pathogen detection and species characterization, were evaluated for their
sensitivity and specificity. The results showed that the two techniques have very low
diagnostic agreement in detecting all the three species of trypanosomes, (kappa values <
0.02). The sensitivity of PCR amplification in detecting trypanosomes in cattle blood
was found to be 5-10 times higher than microscopy. The specificity of microscopy was
found to be poor, in relation to PCR amplification as it mis-diagnosed many cases as
having T. vivax while PCR showed that they were T. brucei. The study showed that
Theileria species were more prevalent in Tororo than in Busia (60% vs. 38%).
Molecular based methods revealed that Theileria mutans was the predominant species
in cattle, at 42% prevalence while the overall prevalence of Theileria species was found
to be 66% in Tororo district.
The prevalence of trypanosome species was found to be 10 times higher than previously
recorded in this region. The study revealed that isometamidium chloride (Samorin)
treatment of cattle did not protect the animals from infection with any of the three
trypanosome species for more than three months. While Samorin treatment appeared to
control trypanosomiasis in areas with low prevalence, the drug had no effect in
controlling the disease in high prevalence areas. It would therefore be necessary to
combine the use of drug intervention with other methods such as vector control, to
reduce the prevalence, in order to realize effective control of trypanosomiasis. The
results further show that Samorin treatment did not offer protection against T. brucei
infections in cattle. The study also showed that treatment of cattle with diminazene
aceturate (Berenil) can not be relied upon to control transmission of trypanosomes.
Finally, the study revealed that the prevalence of T. brucei is higher in adult animals
than in calves while the prevalence of T. congolense and T. vivax is higher in animals
below 24 months.