3.2 Introduction
Fleas (Siphonaptera) are hematophagous insects and obligatory
ectoparasites of vertebrates that have colonized variety of habitats
from wet tropical forests to semi-arid and desert areas ( Zając et
al ., 2020; Zhang et al ., 2022). They have an obligate parasitic
life with a wide range of potential hosts, primarily small mammals and
less often birds (Eads et al ., 2020). Fleas exhibit a
holometabolous type of lifecycle and complete their life cycle in 14
days to 140 days, depending mainly on temperature and humidity (Krämer
and Mencke, 2012; Ashwini et al ., 2017; Gram and Short, 2020).
Fleas contribute significantly in the circulation of pathogens hence
receiving considerable attention mostly because they are vector of many
zoonotic diseases (Eads et al ., 2020). They play role in
spreading plague disease as well as other emerging pathogens that causes
zoonoses such as bartonelloses, tularemia and rickettsioses (flea-borne
spotted fever, Q fever and murine typhus), fleas also maintains and
transmits pathogens of myxomatosis and trypanosomiasis and can act as
intermediate hosts of some helminthes (Zając et al ., 2020;
Cófreces et al ., 2021). However, the most known flea borne
zoonotic disease is plague caused by bacteria known as Yersinia
pestis ; a zoonotic bacteria renowned for killing millions of humans
during the Black Death in Europe in 14 century (Ditchburn and Hodgkins,
2019; Barbieri et al ., 2021; Izdebski et al ., 2022).
Plague is still threatening the public health in some parts of the
world, especially in African countries (Ditchburn and Hodgkins, 2019).
By doing surveillance studies on flea assemblage on rodent community in
plague endemic areas we can understand factors that influence flea
abundance and infestation potential on rodents and being aware of
significant factors that may endanger the public health and therefore we
can be in a good position to suggest effective intervention strategies
to control their spread.
Plague persistence in plague endemic areas is characterized by
coexistence of interactions among rodent communities and flea species,
whereby some species of rodents and fleas are better at maintaining,
amplifying and transmitting Yersinia pestis (Gage and Kosoy,
2006; Antolin et al ., 2010). Some of frequently reported fleas
and rodents species involved in plague maintenance and transmission areXenopsylla cheopis, Xenopsylla brasiliensis andDinopsyllus lypusus and rodent species Lophuromys spp ,Praomys delectorum , Graphiurus murinus , Lemniscomys
striatus, Mastomys natalensis , and Rattus rattus (Kilonzoet al ., 2006; Makundi et al ., 2008; Eisen and Gage, 2009).
A study done by Ziwa et al. (2013) has reported the concurrence of
host-vector interaction to be responsible for transmission of plague
disease. Also Makundi et al. (2015) has reported the presence of
multiple associations between domestic and peridomestic rodent species
infested with fleas to be among major contributing factors for
persistence and spread of plague in plague endemic areas. Moreover, the
roles of hosts and fleas, for instance in plague maintenance or
amplification, is mostly affected with change of space and time (Kosoyet al ., 2017).
The distributions and community structure of fleas are influenced by
numerous biotic and abiotic factors, that include, host species
diversity, sex, age, body size, immune status, host population
abundance, habitat diversity and seasonal variation of temperature and
precipitation (López-Pérez et al ., 2017, 2022). Host diversity is
a relevant factor to consider since it involves variation in flea
species richness (Fantozzi et al ., 2022), yet it is not a fixed
rule, fleas can infest hosts phylogenetically close, switching between
coexisting species within guilds (Cófreces et al ., 2021).
Noting this uncertainty plague management in plague foci is mostly
efficient when encompassing rodents and their flea parasites. As
described by Garcia-Longoria et al. (2019) host communities can
influence parasitism. Community organization of parasites is considered
to be determined mainly by their hosts because host present a habitat
for parasites, providing them with place for living, feeding and mating
(Fellin and Schulte, 2022). Thus, a host can be reflected as a
biological shelter for parasites. Unlike endoparasites, ectoparasites
are influenced not only by host characteristics, but also by
characteristics of the host environment (Krasnov et al ., 1997).
Therefore, a habitat of the ectoparasite should not be just a particular
host, but a particular host in a particular habitat. If so, an important
determinant of parasite community structure should be a complex
host-habitat relationship. Quantifying variation of ectoparasites load
among host species and comparing these variation with other ecological
factors which are known to shape host communities is the good approach
for understanding dual nature of host-parasite interaction (Merrillet al ., 2020; Veitch et al ., 2020).
Concisely, the aim of this study was to examine rodent’s flea load and
their associated factors in plague endemic area of Karatu district by i)
quantifying and assessing the variation of flea’s parasitological
indices (specific flea index, total flea index and flea infestation
prevalence on rodents), ii) assessing the association of abundance of
species of fleas with rodent species, plague and non-plague foci
villages, season (wet and dry season), habitat type and rodent sex, iii)
investigating flea biased parasitism on rodent’s weight and sex (male
and female rodents) and lastly, iv) assessing the influence of host
characteristics (rodent species, sex and weight), habitat type, season
and plague locations on abundance of fleas. Result of this study will
help to create awareness to the public health sectors and vector control
programs by providing valuable information that will help in decision
making process regarding flea control in plague endemic area of Karatu
district, northern Tanzania.