Susceptibility to Yersinia pestis Experimental Infection in Wild Rattus rattus, Reservoir of Plague in Madagascar

Abstract

In Madagascar, the black rat, Rattus rattus, is the main reservoir of plague (Yersinia pestis infection), a disease still responsible for hundreds of cases each year in this country. This study used experimental plague challenge to assess susceptibility in wild-caught rats to better understand how R. rattus can act as a plague reservoir. An important difference in plague resistance between rat populations from the plague focus (central highlands) and those from the plague-free zone (low altitude area) was confirmed to be a widespread phenomenon. In rats from the plague focus, we observed that sex influenced plague susceptibility, with males slightly more resistant than females. Other individual factors investigated (weight and habitat of sampling) did not affect plague resistance. When infected at high bacterial dose (more than 10⁵ bacteria injected), rats from the plague focus died mainly within 3-5 days and produced specific antibodies, whereas after low-dose infection (< 5,000 bacteria), delayed mortality was observed and surviving seronegative rats were not uncommon. These results concerning plague resistance level and the course of infection in the black rat would contribute to a better understanding of plague circulation in Madagascar.

Resistance to Plague Among Black-Tailed Prairie Dog Populations

“…Grasshopper mice trapped from a population in northern Colorado with a known association with plague and their laboratory-bred F1 progeny had an LD 50 nearly 2000 times higher than that of a plague-naive population from Oklahoma. Likewise, black rat (Rattus rattus) populations from a plague-endemic area in Madagascar were shown to be at least 1000 times more resistant than populations from nearby plague-free zones (Rahalison et al 2003, Tollenaere et al 2010, and this resistance was also passed to laboratory-born offspring emphasizing its genetic basis (Rahalison et al 2003).…”

Climatic and evolutionary drivers of phase shifts in the plague epidemics of colonial India

“…Because resistance to Y. pestis is likely governed by multiple loci (28-30), we modeled phenotypic selection of the susceptibility trait. Given historical (42,43,63) and contemporary evidence (27,28,64) for counterselection of resistance in the absence of plague, we also model a fecundity trait c(ξ) = 1 -ι(1 -ξ) that quantifies the reproductive capacity of a rat as a life history tradeoff associated with resistance. The value 1 -ι is then the relative fecundity of a wholly resistant rat compared with a wholly susceptible rat.…”

“…R. rattus is encountered in sylvatic and urban settings, serving as a both a wildlife plague reservoir and the host that propagates bubonic plague epidemics affecting humans. In areas of Madagascar, where sylvatic R. rattus populations function as the primary plague reservoir (27), variable innate susceptibility to Y. pestis infection is associated with resistance alleles that have undergone intense selection over a century of plague exposure (28)(29)(30). Historical human bubonic plague epidemics have been associated with the introduction of Y. pestis to previously unexposed commensal rat populations.…”

Spatial analysis and identification of high risk plague regions in Pakistan based on associated rodent species distribution

“…According to previous studies, the most important hosts of plague in the neighboring countries of Pakistan are Rhombomys opimus (great gerbil) [20], Marmota caudate (long-tailed marmots) [21], Acomys ahirinus (cairo spiny mouse), Alticola argentatus (silver mountain vole) and Ellobius fuscocapillus (southern mole vole) [22], Mus musculus [23], Bandicota bengalensis (lesser bandicoot rat) [24], and Rattus rattus [25]. Based on the existing knowledge, we searched these potential plague carrier rodent species in different districts of Pakistan.…”