An analysis of host-carrier association, prevalence and community awareness of plague disease in south-western, Zimbabwe

Abstract

Human-animal species interaction has increasingly become a subject of interest in community ecology as evidenced by the recent theory on species co-occurrences in interaction networks. However, a neglected area is that of understanding zoonotic disease host-carrier associations in tropical semi-arid savanna ecosystems, that is, the extent and impact of biotic interactions. Over time, however, humans have developed unique knowledge which helps in awareness and practices on zoonotic diseases like plague. The aim of this study was to analyze the diversity and host-carrier association, prevalence and local community awareness of plague disease in a semi-arid tropical savanna ecosystem of south-western Zimbabwe. Specifically, the objectives of this study were to: (i) analyse the diversity of rodents and fleas, and rodent-flea association, (ii) determine the prevalence of plague bacteria (Yersinia pestis) among captured rodents, and (iii) assess the level of awareness and practices of local communities on zoonotic disease management. This study followed a quasi-experimental design comprising of two study areas, Nkayi and Umzingwane districts. For the first and second objectives, rodents were captured using the removal trapping method, utilizing Sherman traps between April 2017 and April 2018. Using standard procedures rodents were euthanized and subsequently dislodging fleas from them. A two-way case study was used with a quasi-control site (Umzingwane district) and treatment (Nkayi district). Data were analysed using chi-square test of independence, Mann-Whitney U and graphical analysis. For the third objective, focus group discussions were used to collect data on community awareness and local practices on zoonotic disease in the two districts between July 2017 and April 2018. Thematic data analysis was done in Microsoft word. Results showed, firstly, a total of five (5) rodent species and four (4) flea species recorded in the study areas, with no significant differences in both species diversity between the study districts. The relative abundant rodent and flea species in Nkayi district were Gerbilliscus leucogaster (N= 65; relative abundance (RA) = 80.25) and Xenopsylla brasiliensis (N = 113; RA = 99.12). In Umzingwane district the RA of rodents was high for Mastomys natalensis (N = 70; vi RA = 95.89) while fleas were highest for Chiastopsylla rossi (N = 20; RA = 41.67) and Dinopsyllus ellobius (N = 19; RA = 39.58). In Nkayi district, the flea species, X. brasiliensis, was mostly associated with four rodent species, namely, M. natalensis, Saccostomys campestris, Gerbilliscus brantsi and G. leucogaster whereas in Umzingwane district, all the recorded flea species, i.e., X. brasiliensis, C. rossi, Ctenophthalmus calceatus and D. ellobius were associated with only one rodent species, i.e., M. natalensis. Percentage Incidence Indices (PII) and Specific Flea Indices (SFI) for X. brasiliensis on M. natalensis was higher in Nkayi district compared to Umzingwane district. Noteworthy was the higher PII and SFI of X. brasiliensis on G. leucogaster in Nkayi district. Secondly, an overall low plague prevalence of 2.4% in the study area with only one study site, i.e., Umzingwane having a single M. natalensis rodent recorded as infected. Thirdly, most of the study focus group discussants were fairly aware of zoonotic diseases and reported that there were several management practices adopted by the local communities to manage zoonotic disease inclusive of plague. In conclusion, this study revealed a low and insignificant diversity of both rodents and flea species, variable rodents and fleas’ species interactions in different areas, a low prevalence of plague disease associated with fair local awareness and diversified practises in zoonotic disease management, however, coupled with poor awareness of plague disease especially in Umzingwane district and poor uninformed practices on rodent population control. High relative abundance of G. leucogaster and X. brasiliensis in Nkayi district warrants for active plague surveillance system in the district. High PII and SFI of X. brasiliensis on M. natalensis and G. leucogaster further on gives the importance of the active surveillance system in the district. High relative abundance of M. natalensis in Umzingwane district also warrants the need for an active surveillance system in the district as well. Integrated disease management system covering monitoring of rodent-flea species interactions and associated population dynamics and plague prevalence would help minimise future emergence of plague disease in the study area and similar areas.