Rodent borne pathogens infecting mastomys natalensis in selected areas of Morogoro and Iringa, Tanzania
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Date
2024
Authors
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Publisher
Sokoine University of Agriculture
Abstract
The study on the rodent borne pathogens infecting Mastomys
natalensis in selected sites of Morogoro and Iringa was conducted
between January, 2021 and July, 2022. Various studies have
shown that, human and animal diseases caused by viruses,
bacteria, and parasites carried by rodents are on the increase,
however, relatively, little is known of the prevalence and dynamics
of infections by Trichuris spp. Leptospira spp. Bartonella spp. and
other helminths in rodents and their ectoparasites. Similarly, little
is known on the effectiveness of broad spectrum anthelminthics
on gastrointestinal parasites of rodents.
In this study, the prevalence and seasonal variation of Trichuris
worm infection in rodents was investigated. In addition, molecular
detection of Leptospira spp. and Bartonella spp. in M. natalensis
and its ectoparasites was studied. Furthermore, the effect of
Ivermectin® against gastrointestinal helminths was determined.
These studies were carried out between January 2021 and July
2022.
The study aimed at addressing three key specific objectives; i)
Determining prevalence and seasonal variation of Trichuris worms
infection in M. natalensis in Morogoro and Iringa regions ii)
Molecular detection of Leptospira spp. and Bartonella spp. in M.
natalensis and its ectoparasites in Morogoro iii) Determining the
effect of Ivermectin® on Intestinal helminths in the multimmate
mouse (M. natalensis).
The study sites were in Morogoro and Iringa regions. In Morogoro
region, the studies were carried out in Choza, Kiroka and in an
enclosed area (Fence) close to Sokoine University of Agriculture
main campus. For Iringa region, Isimani and Idodi villages were
selected.
Mastomys natalensis was used throughout the study as the model
rodent species because it is known to carry a number of athogens. Also, it is the most abundant, dominant and most
studied species of the small mammals in Tanzania.
To address the first specific objective, the study was conducted
between January and November, 2021 in Morogoro and Iringa
regions. These regions differ significantly in their eco-climatic
conditions. Removal trapping was conducted using Sherman® live
traps in rainy and dry seasons. Gastrointestinal tracts of captured
rodents were screened for the presence of Trichuris worms and
identified using morphological keys. The effect of geographical
region, season and sex of the rodents on Trichuris worm
infections were tested using a generalized linear model with
binomial function. Data were analyzed using R Statistical Software
4.1.3 at a p- value of 0.05. For the second objective, M. natalensis
were captured live in fallow habitats using Sherman® traps and
anesthetized using halothane. Blood samples were obtained from
the retroorbital sinus and ectoparasites were removed from the fur
using a hard brush and preserved in 70% ethanol. Real Time –
qPCR followed by Sanger sequencing was used to detect
Leptospira spp. and Bartonella spp. from the blood and
ectoparasites respectively. Confidence intervals (95% CI) for the
prevalence of Bartonella spp. and Leptospira spp. in M. natalensis
was determined at the level of alpha of 0.05. The statistical
difference in Bartonella spp. infection in mites from males and
females M. natalensis was determined using a two-tailed student’s
t-test.
For the third objective, rodents were live captured from the open
field as well as free ranging rodents from “Fence”. The animals
were marked, caged individually and supplied with feed and water
ad libitum. A total of 45 animals were released into each of two
enclosed plots (treatment and control groups).
The treatment group received a single dose of an aqueous
suspension of Ivermectin® (0.0007ml/l), while the control group
was left untreated. The animals from both plots were captured
biweekly and screened for helminths eggs over a period of eight weeks. Analysis of variance (ANOVA) was used to determine the
mean variation of gastrointestinal helminths burden before and
after treatment with Ivermectin®.
The following were the results of these studies. i) A total of 200 M.
natalensis were studied from each of the two regions, consisting
of 100 animals per season. For Morogoro, the overall prevalence
of Trichuris worms in M. natalensis was 36% (n=72), of which
42/200 and 30/200 were for the rainy and dry seasons
respectively. For Iringa, the overall prevalence was 65% (n=130),
of which 80/200 and 50/200 were for the rainy and dry seasons
respectively. Trichuris worm infection was significantly higher
during the rainy season in Iringa than in Morogoro and no
significant difference in infection was observed between males
and females in either of the two regions or seasons. Other forms
of helminths detected were Strongyloides spp., Capillaria spp.,
Hymenolepis spp. and eggs of a yet to be confirmed helminths,
possibly an Anoplocephalid sp.
ii) For the molecular studies, Leptospira spp. was demonstrated in
one out of 100 M. natalensis while, for Bartonella spp., the
prevalence of (14%) was recorded in mites with a higher
proportion in adult males than in females. Upon Sanger
sequencing, four positive samples showed a complete sequence
of the ITS gene. Indicating that all samples belonged to
Uncultured Bartonella.
iii) With regard to the effect of Ivermectin® on intestinal helminths,
there was no significant difference in Strongiloides spp., H. nana
and Physaloptera spp. infection before and after treatment.
However, a significant reduction of H. diminuta and Trichuris
worms was observed in the treated animals. No significant
increase in the number of worms recorded in the control group.
The overall prevalence of helminths in M. natalensis was
significantly higher in male than female rodents. To address the gaps identified from these studies, there is a need
for improved surveillance of rodents borne diseases in the studied
regions and elsewhere and to establish strategic control programs
to reduce their adverse impact on health. This is important,
considering that rodents and specifically M. natalensis is the most
abundant rodent pest species in sub-Saharan Africa and
maintenance host and carrier of diverse zoonotic pathogens.
Further interventions to raise awareness of the role of commensal
rodents and their ecto/endoparasites in disease transmission are
recommended. Also, Ivermectin® is recommended for use in
treatment against helminths. However, it is recommended to
investigate the scope of its effectiveness in diverse helminths.
Description
Dissertation
Keywords
Rodents, Mastomys natalensis, Trichuriosis, Leptospira spp., Bartonella spp.