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).