Early-phase Transmission of Yersinia pestis by Cat Fleas (Ctenocephalides felis) and Their Potential Role as Vectors in a Plague-endemic Region of Uganda

Abstract

In recent decades, the majority of human plague cases (caused by Yersinia pestis) have been reported from Africa. In northwest Uganda, which has had recent plague outbreaks, cat fleas (Ctenocephalides felis) have been reported as the most common fleas in the home environment, which is suspected to be a major exposure site for human plague in this country. In the past, C. felis has been viewed as only a nuisance-biting insect because limited laboratory studies suggested it is incapable of transmitting Y. pestis or is an inefficient vector. Our laboratory study shows that C. felis is a competent vector of plague bacteria, but that efficiency is low compared with another flea species collected in the same area: the oriental rat flea, Xenopsylla cheopis. On the other hand, despite its low vector efficiency, C. felis is the most common flea in human habitations in a plague-endemic region of Uganda (Arua and Nebbi Districts), and occasionally infests potential rodent reservoirs of Y. pestis such as the roof rat (Rattus rattus) or the Nile rat (Arvicanthis niloticus). Plague control programs in this region should remain focused on reducing rat flea populations, although our findings imply that cat fleas should not be ignored by these programs as they could play a significant role as secondary vectors.

Blood Meal Identification in Off-Host Cat Fleas (Ctenocephalides felis) from a Plague-Endemic Region of Uganda

“…trapped in our study area and from the three predominant domestic and peridomestic rodent species in our study area: black rat, Nile rat and multimammate mouse. 15,31 The mixedsample sequences differed from the rodent sequences by 5 nt and from the Crocidura sp. sequence by 3 nt.…”

“…We collected tail tissue or whole blood from the four small mammal species that predominate in domestic and peridomestic environments in our study area: black rat, Nile rat (Arvicanthis niloticus), multimammate mouse (Mastomys natalensis), and shrew (Crocidura species). 15,31 Mammals were trapped in the West Nile region and identified to genus or species based on morphological measurements. 36 Tail tissue was stored in 70% ethanol.…”

“…Cat fleas in East Africa are most often identified as C. felis strongylus based on morphological characteristics 15,17,18 ; recent molecular studies, however, have found no evidence for the existence of C. felis subspecies. 19,20 Ctenocephalides felis strongylus may therefore share biological characteristics, including feeding behavior and transmission efficiency, with other C. felis subspecies, including Ctenocephalides felis felis.…”

“…26,[28][29][30] In the West Nile region, this species occasionally infests rodents, including the black rat (Rattus rattus), which is abundant in the domestic environment and susceptible to Y. pestis infection. 8,15,31 Further implicating the cat flea as a potential bridging vector, Eisen and others 15 recently showed that C. felis is capable of early-phase transmission of Y. pestis.…”

“…[8][9][10] Some studies, however, have implicated the human flea, Pulex irritans, as a potentially important Y. pestis vector in regions where it is the predominant host-seeking (off-host) flea species in human habitations, although it is unclear to what extent its postulated role in human plague outbreaks derives from an ability to spread the bacterium from one person to another versus an ability to serve as a bridging vector from rodent hosts to humans. [10][11][12][13][14] Recent investigations have found that the cat flea, Ctenocephalides felis, comprises the majority of off-host fleas captured in huts in the West Nile region, 15,16 however relatively little is known about its potential role as a Y. pestis vector in this plague focus.…”