3.5.3 Associated factors influencing flea abundance on rodents
Basically we found that flea abundance on rodent community were
influenced by variation of season of the year (wet and dry season),
plague and non-plague foci villages, variation of habitat types and host
characteristics. Among all these factors, variation of season of the
year has the major impact on flea abundance as it determine distribution
of food and breeding cycle of their rodent host (Leirs et al .,
1996). Change in temperature and humidity of the year in response to
changing season (wet and dry season) is significantly controlling the
growth and survival of immature fleas (Ziwa et al ., 2013).
Different studies have reported the influence of seasonal change on
abundance of rodents and fleas to have the impact on maintenance and
transmission of plague disease (Njunwa et al ., 1989; Makundiet al ., 1994; Eads et al ., 2016; Shuai et al .,
2022).
Variation of wet and dry season is generally affecting growth,
reproduction and survival of immature stage of fleas (Krasnov et
al ., 2001; Ngeleja et al ., 2017). Low abundance of fleas during
wet season could be explained by the fact that, the survival of immature
fleas in rodent burrows is affected by soil moisture which is controlled
by precipitation outside the burrow. Excessive wet conditions in rodent
burrows contained with organic matter at a relative humidity
>95% can promote growth of vicious fungi that reduces
larval and egg survival (Eisen, 2009; Ben Ari et al. , 2011). The
increase in flea abundance during dry season was probably due to the
increase in the abundance of their rodent host as well as the supportive
weather with moderate warm and moist condition during early dry season.
Reportedly, rodent’s flea abundance is mainly affected by ambient
temperatures, precipitation, and relative humidity, where as warm-moist
weather is providing the explanation for higher flea indices (Ben Ariet al., 2011; Wale et al ., 2023).
Plague foci villages was significantly increasing abundance of fleas
compared to non-plague foci villages. The increase of flea abundance
could be encouraged by high proportion of abundance of rodents in plague
foci that presented many potential biological habitats and source of
blood meal for fleas. The increase in abundance of rodents influences
the increase in abundance of fleas and subsequently enhances the
distribution and composition of flea communities (Krasnov et al .,
2002; Eads et al ., 2016).
Habitat type was another factor that influenced abundance of fleas in
our study area. Different habitats have different characteristics that
are important for determining distribution and abundance of rodent host
of fleas. As reported by Brinkerhoff, (2008) and Laudisoit et al.
(2009), the change of habitats is affecting the composition of rodent
species and their fleas, making it an important factor in ecological
surveillance of abundance of flea species on rodents. In this study we
found that abundance of fleas was significantly increasing in farm lands
as compared to other habitats. Farm land habitat was observed to
encourage rodent colonization as it promote availability of food such as
maize and wheat seeds left after harvest during dry season. Habitually
rodents prefer to reside in areas with adequate foods where they can
make burrows and nest to protect them and their young from predation.
Habitats with high food availability and less disturbance and control
facilitate the increase in abundance of rodents and their fleas.
Moreover, we found that different rodent species have different
influence on flea abundance. Rattus rattus was significantly
influencing abundance of fleas as compared to other rodents. The
characteristics of individual rodent host have been reported to affect
responsible mechanism for flea acquisition (Kiffner et al .,
2013). Behavior and tendency of R.rattus to live in human
habitats facilitates the interactions and sharing of fleas among them
due to existence of small range of this habitat. Movements ofR.rattus from one house to another and from nearby farms and
livestock shelters is also predisposing this specie to encounter many
fleas which are subsequently shared to other R.rattus . In
addition, human habitats provide suitable environment with availability
of food and warm condition supporting growth and reproduction of both
rodent and fleas especially when the control measures are abandoned
leading to increase flea index among rodents in this habitat. Tactics
employed by fleas and many other ectoparasites to colonies microhabitats
of the host species (such as rodent’s burrows) or wait until a suitable
host is present helps parasites to infest host easily especially a new
born or when new host has visited the burrow (Bitam et al .,
2010).