Behavioral Response of Glossina pallidipes to Trypanosome-Induced Semiochemicals under Laboratory and Field Conditions in Kwale County, Kenya
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Date
2025-08
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Kenyatta University
Abstract
Animal African Trypanosomiasis (AAT) transmitted by the Glossina spp is a major
constraint to livestock production in Sub-Saharan Africa (SSA) despite various
control efforts. Trypanosome-induced semiochemicals found in urine of infected
cattle are predictive AAT biomarkers with potential for use as baits for tsetse trapping
enhancement. The objective of this study was to investigate the urine from
trypanosome infected cow and its modified semiochemicals as effective attractants
for infected Glossina pallidipes with an economical dispenser for field application.
Coupled Gas Chromatography-Mass Spectrometry was used to analyze cow urine
odor profiles to identify Trypanosoma congolense (T. c) modified semiochemicals.
The chemistry of urine from trypanosome-infected cow was mimicked by formulation
of blends of T. c modified semiochemicals. The flies’ response to the various
treatments were conducted using bioassays in the laboratory and field. Laboratory
bioassays involved free flight dual choice testing the fly’s response to urine from
trypanosome infected cow. Field evaluations involved comparing the baited trap
catches against un-baited trap used as a negative control. Both liquid and dry
formulation dispensers were evaluated whereby dry dispensers proved the most
economical and effective way of dispensing the test compounds due to its single
loading. The urine from trypanosome infected cow and its modified semiochemicals
were evaluated for their attractiveness to infected G. pallidipes by screening of field
caught flies using ITS1 primers to determine their infection rates. Infection rates were
checked through molecular biology techniques which involved DNA extraction, PCR,
gel electrophoresis and sequencing. Urine from trypanosome-infected cattle exhibited
induced semiochemicals and elevated levels of existing semiochemicals.Urine from
trypanosome infected cow attracted significantly more flies in both laboratory (t=3.15,
p=0.003) and field bioassays (F=4.2, p=0.03). Traps baited with dihydro-α-ionone
and 3-ethylphenol attracted significantly more G. pallidipes compared to un-baited
control trap, (dihydro-α-ionone, p=0.04, and 3-ethylphenol, p=0.02). Three blends of
T.c modified semiochemicals (NB1, NB2 & NB3) attracted significantly more G.
pallidipes compared to un-baited control trap (F=10.31, p= 0.001). NB1 attracted
significantly more blood-fed G. pallidipes compared to un-baited negative control trap
(Fisher Exact Test, p=0.0001). There was no significant difference between mean G.
pallidipes catches using dry and liquid formulation dispensers (p=0.7257). Traps
baited with urine from Tc-infected cow attracted five times more infected G.
pallidipes compared to those baited with urine from healthy cow (Fisher Exact Test,
p=0.001). NB1 attracted twice the number of infected flies whereas NB3 attracted
three timesinfected flies as compared to un-baited control trap. Trypanosome-induced
semiochemicals demonstrate their ability as effective attractants for infected G.
pallidipes. The results of this study are vital for developing new trypanosomiasis
control strategies using effective baits for G. pallidipes
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science (Applied Parasitology) in the School of Pure and Applied Sciences of Kenyatta University, August, 2025
1.Jenard Patrick Mbugi
2.Lucy Muthoni Kamau
2.Merid Negash Getahun