Bionomics, blood-host plasticity and its effect on host-choice and feeding behaviour of tsetse species from selected human- wildlife interface in Tanzania
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Date
2024-04
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Sokoine University of Agriculture
Abstract
Tsetse flies are vectors of trypanosome parasites which cause
human African trypanosomiasis (HAT) in human and African animal
trypanosomiasis (AAT) in livestock across Sub-Saharan Africa.
These flies feed exclusively on animals’ blood. It is during blood-
feeding process of these flies; un-infected host get infected by
parasites carried by infected vector. Several tsetse controls
programs have been implemented so as to minimize the incidences
of trypanosome infections; however, the human-wildlife interfaces
remain as the risk areas where both livestock and human being can
be infected with trypanosome parasites. Therefore, surveillance and
control of these flies is important so as to minimize the African
trypanosomiasis’ risks in these areas. This study assessed the
species composition, abundance and phylogenetic relatedness of
wild collected tsetse flies from selected human-wildlife-livestock
interface in Tanzania. Variation in host choice and feeding
behaviours of predominant species’ (Glossina morsitans) siblings
whose parents were blood-fed on different host species were also
investigated. The tsetse flies were trapped seasonally in two
selected wards within Morogoro Rural district. The study wards and
villages were purposively selected targeting those which are
bordering to protected areas. In each ward, baited NZI, Pyramidal
and Biconical traps were deployed at 200m distance apart from each
other for 72 hours before rotating to the next trapping sites. Trapped
flies were collected from the traps after 24 hours then identified
morphologically and later confirmed using the Polymerase Chain
Reaction (PCR). Moreover, a colony of tsetse flies were established
from pupa obtained from tsetse and vector control centre, Tanga.
Hatched flies were maintained on selected hosts blood until the
offsprings were obtained for the experiments. The host-choice and
feeding behaviours experiments were carried out in large semi-field
cage containing four small equal size screen cages. During the
experiments, individual host was placed in a screen cage which
allowed flies to enter through openings on each side. The groups of flies (20 per replicate) colour-marked differently basing on their
parents’ bloodmeal hosts, were released from the centre of large
semi-field cage and left to forage for 24 hours before being
collected, then, sorted basing on the location, feeding status and
parents’ bloodmeal. The total of 784 tsetseflies were collected;
Glossina pallidipes (n=371; 47.32%) and Glossina morsitans
morsitans (n=413; 52.68%). Of these, 96 flies (80-female, 16-male)
were blood-fed; 57(48-female and 9-male) G. pallidipes and 39(32-
female, 7-male) G.m. morsitans. Overall abundance of collected
tsetse significantly varied across surveyed wards (χ2=4.597, df=1, p=
0.032), villages (χ2=9.491, df=3, p= 0.023), habitats (χ2=17.239,
df=2, p<0.001), months (χ2=13.507, df=3, p= 0.004) and deployed
traps (χ2=6.348, df= 2, p= 0.04). About 78.82% of tsetse flies were
collected from Kisaki ward (n=618; p<0.001) and 21.17% (n=166;
p=0.032) from Bwakila chini. The highest proportion of these flies
were collected in Mbojoge village (62%; n= 489) followed by
Kiperege (18%; n=141) and Sebo (16%; n=129). NZI traps collected
the highest proportion of tsetse flies (n=422; 54%; 4.98 FTD)
followed by Pyramidal traps (n=281; 36%; 4.01 FTD) and Biconical
traps (n=81; 10%; 1.87 FTD). Similarly, the large proportion of tsetse
flies (78.06%) were collected in bushed grassland habitat (n=612;
55.41 FTD) followed by woodland habitat (16.45%; n=129; 20.56
FTD) and farmland (5.5%; n=43; 7.17 FTD). The phylogenetic
analysis revealed genetic relatedness of tsetse flies collected in
Tanzania with those collected from Nigeria and Senegal.
Furthermore, a total of 213 flies (72.95% of the recovered) were
attracted to the hosts. The number of flies attracted to different hosts
varied significantly (χ24= 33.685, p= 0.0001); Rodent (n=80,
p=0.006), Rabbit (n=59, p=0.331), Guinea pig (n=49, p=0.057) and
squirrel (n=25, p=0.005). The number of flies attracted to their
parent’s blood meal source varied significantly (χ212 = 56.476,
p<0.001); rabbits (n= 35, 59.32%, p<0.001), rodent (n=25, 31.25%,
p=0.043) and guinea pig (n= 19, 38.78%, p=0.45). But, only 39 flies
(18.31% of total attracted) bloodfed on the hosts; Guinea pigs (n=10,
25.64%), Rodents (n=23, 58.97%), Rabbits (n=6, 15.38%) and Squirrels (n=0,0.0%). There was significant variation in number of
flies that fed successively across hosts (χ24=49.478, p<0.001). The
present study recommends NZI and Pyramidal traps for tsetse fly
control at the interface and wet season as appropriate season for
conducting control activities. Also, the study confirms the presence
of the hosts’ differential attractiveness to flies but failed to explain
observed behaviours in relation to genetic inheritance. Therefore,
future studies are recommended to investigate the effect of
bloodmeal sources on tsetse fly siblings’ behaviours across filial
generations using small mammals.
Description
MSc. Dissertation
Keywords
Tsetse fly, wildlife-livestock-human interface, NZI, Pyramidal, Abundance, Glossina morsitans, Rabbits, Guinea pigs, Rodents -Squirrels, blood-fed, attracted