Influence of variations in species and host physiological attributes on olfactory response and reproductive performance of female adult ornithodoros moubata
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Date
2024-05
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Sokoine University of Agriculture
Abstract
ick-borne relapsing fever (TBRF) poses a significant threat to
public health, particularly in Tanzania, where it causes high mortality
rates in children under five and disrupts the health of pregnant
women. Pervasiveness of this disease has raised the need to
understand behavioural response of the ticks to their reservoir hosts.
To effectively combat this disease, it is crucial to understand the
behavioural responses of the vector, Ornithodoros moubata, to its
various host species. This study delves into this intricate
relationship, exploring the impact of host characteristics and species
on the tick's olfactory response and feeding behaviour. Additionally,
despite the evident role of climatic, anthropogenic, and biological
factors in increasing the risk of recurrent TBRF outbreaks in many
African countries like Tanzania, there is a significant lack of
comprehensive data from studies elucidating intra-species variations
in the feeding and reproduction patterns of the primary vectors (O.
moubata) across diverse hosts.
The first part of the study investigates the influence of physiological
factors such as age, sex, and weight of white mice on the tick's
attraction. Additionally, it examines the attractiveness of different
host species, including Mus musculus, Mastomys natalensis, Rattus
rattus, and Gallus gallus domesticus, to O. moubata. The second
part focuses on intra-species variations in the feeding behaviour and
reproductive performance of O. moubata across different hosts,
including mice, rats, and chickens. This comprehensive analysis
sheds light on the tick's host preferences and provides valuable
insights for developing effective control strategies against TBRF and
other tick-borne diseases.
The assessment of effects of physiological status specifically age,
sex, and weight of white mice and different host species on the
olfactory behavioural response of O. moubata, initially involved
obtaining an adult colony to be utilized in the experiment from the Tanzania Plant Health and Pesticide Authority (TPHPA). 15 (10
males and 5 females) ticks were introduced through the release
chamber in the middle of each olfactometer and allowed to select
the test stimulus/host for 12 hours over night. The numbers of ticks
trapped in both arms and the release chamber was counted. Each
dual choice mode was composed 12 olfactometers. The experiment
had five replicates per three of the four choice dual choice modes
employed (fixed age, fixed sex and varying age and sex) while
remaining dual-choice mode (varying hosts) had six replicates. The
number of ticks trapped in both arms of the olfactometer was the
measure of attractiveness. Results revealed that mice sex (P =
0.028) and low weight (P < 0.001) to be highly associated with O.
moubata attraction. Slight significant attraction was observed in 45
days old mice (P = 0.045). Gallus gallus domesticus was most
attractive compared to white mice. Additionally, only sex and weight
interaction had positive correlation to attraction of O. moubata (P=
0.020). Additional testing is required to evaluate exact age, weight,
and the species dependent response as well as the role of mice skin
microbiota on attraction of O. moubata.
On the other hand, the second part of the study focused on
assessing intra-species variations in the feeding and reproduction
patterns of O. moubata across different hosts in a controlled lab
experiment. Employing a cross-sectional experimental study design,
the controlled-lab experiment sought to examine differences in
feeding behaviours and reproductive success of the ticks exposed to
various host species including Mus musculus, Mastomys natalensis,
Rattus rattus, and Gallus gallus domesticus. Descriptive and
inferential analysis of the generated data was performed using the R
Software Version 2023.12.1. The study revealed that O. moubata
exhibited the highest feeding success on Rattus rattus, indicating a
preference for this host species. However, the results lacked
statistical significance, emphasizing the necessity for further
research to confirm host preference. Additionally, the study
uncovered host-specific feeding behaviour and reproductive success in O. moubata, with Gallus gallus domesticus being the most
favorable host for egg production compared to others. Given the
potential impact on disease transmission and pest control, it is
crucial to investigate the underlying factors influencing the
preference of the ticks for Rattus rattus, necessitating exploration of
strategies to mitigate their impact. Furthermore, additional research
into the physiological and ecological factors affecting tick feeding
efficiency and host-specific variations is warranted.
Description
Master of Science in Public Health and Pest Management
Keywords
Ornithodoros moubata, Tick-borne relapsing fever, Olfactory behaviour, Host attractiveness, Vector competence, Olfactometers