Browsing by Author "Babi, Nackson"
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Item Early-phase Transmission of Yersinia pestis by Cat Fleas (Ctenocephalides felis) and Their Potential Role as Vectors in a Plague-endemic Region of Uganda(The American journal of tropical medicine and hygiene, 2008) Eisen, Rebecca J.; Borchert, Jeff N.; Holmes, Jennifer L.; Amatre, Gerald; Van Wyk, Kristen; Enscore, Russell E.; Babi, Nackson; Atiku, Linda A.; Wilder, Aryn P.; Vetter, Sara M.; Bearden, Scott W.; Montenieri, John A.; Gage, Kenneth L.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 (Arvicanthisniloticus). 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.Item Efficacy of Indoor Residual Spraying Using Lambda-Cyhalothrin for Controlling Nontarget Vector Fleas (Siphonaptera) on Commensal Rats in a Plague Endemic Region of Northwestern Uganda(Journal of medical entomology, 2014) Borchert, Jeff N.; Eisen, Rebecca J.; Atiku, Linda A.; Delorey, Mark J.; Mpanga, Joseph T.; Babi, Nackson; Gage, Kenneth L.; Enscore, Russell E.Over the past two decades, the majority ofhumanplague cases have been reported from areas in Africa, including Uganda. In an effort to develop affordable plague control methods within an integrated vector control framework, we evaluated the efÞcacy of indoor residual spraying (IRS) techniques commonly used for mosquito control for controlling ßeas on hut-dwelling commensal rodents in a plague-endemic region of Uganda. We evaluated both the standard IRS spraying (walls and ceiling) and a modiÞed IRS technique that included insecticide application on not only on walls and ceiling but also a portion of the ßoor of each treated hut. Our study demonstrated that both the standard and modiÞed IRS applications were effective at signiÞcantly reducing the ßea burden and ßea infestation of commensal rodents for up to 100 d after application, suggesting that IRS could potentially provide simultaneous control of mosquito and ßeaborne diseases.Item Evaluation and Modification of Off-Host Flea Collection Techniques Used in Northwest Uganda: Laboratory and Field Studies(Journal of medical entomology, 2012) Borchert, Jeff N.; Eisen, Rebecca J.; Holmes, Jennifer L.; Atiku, Linda A.; Mpanga, Joseph T.; Brown, Heidi E.; Graham, Christine B.; Babi, Nackson; Montenieri, John A.; Enscore, Russell E.; Gage, Kenneth L.Quantifying the abundance of host-seeking ßeas is critical for assessing risk of human exposure to ßea-borne disease agents, including Yersinia pestis, the etiological agent of plague. Yet, reliable measures of the efÞcacy of existing host-seeking ßea collection methods are lacking. In this study, we compare the efÞcacy of passive and active methods for the collection of host-seeking ßeas in both the laboratory and human habitations in a plague-endemic region of northwest Uganda. In the laboratory, lighted “Kilonzo” ßea traps modiÞed with either blinking lights, the creation of shadows or the generation of carbon dioxide were less efÞcient at collecting Xenopsylla cheopis Rothchild and Ctenocephalides felis Bouche´ ßeas than an active collection method using white cotton socks or cotton ßannel. Passive collection using Kilonzo light traps in the laboratory collected signiÞcantly more X. cheopis than C. felis and active collection, using white socks and ßannel, collected signiÞcantly more C. felis than X. cheopis. In Þeld studies conducted in Uganda, Kilonzo traps using a ßashlight were similar in their collection efÞcacy to Kilonzo traps using kerosene lamps. However, in contrast to laboratory studies, Kilonzo ßea traps using ßashlights collected a greater number of ßeas than swabbing. Within human habitations in Uganda, Kilonzo traps were especially useful for collecting C. felis, the dominant species found in human habitations in this area.Item Evaluation of Rodent Bait Containing Imidacloprid for the Control of Fleas on Commensal Rodents in a Plague-Endemic Region of Norther Uganda(Journal of medical entomology, 2010) Borchert, Jeff; Enscore, Russell E.; Eisen Rebecca J.; Atiku, Linda A.; Owor, Nicholas; Acayo, Sarah; Babi, Nackson; Montenieri, John A.; Gage, Kenneth L.In recent decades, the majority of human plague cases (caused by Yersinia pestis) have been reported from Africa. In an effort to reduce the risk of the disease in this area, we evaluated theefÞcacy of a host-targeted rodent bait containing the insecticide imidacloprid for controlling ßeas on house-dwelling commensal rodents in a plague-endemic region of northwestern Uganda. results demonstrated that the use of a palatable, rodent-targeted, wax-based bait cube was effective at reducing the prevalence of ßeas on commensal rodents and ßea burdens on these animals at day 7 postbait exposure, but lacked signiÞcant residual activity, allowing ßea populations to rebound in the absence of additional bait applications. Our results indicate the use of a palatable host-targeted bait block containing imidacloprid was an effective technique for quickly reducing ßea numbers on rodents in northwest Uganda and, thus, could be useful for lowering the potential risk of human ßea bite exposures during plague outbreaks if applied continuously during the period of riskItem Flea Diversity and Infestation Prevalence on Rodents in a Plague-Endemic Region of Uganda(The American journal of tropical medicine and hygiene, 2009) Amatre, Gerald; Babi, Nackson; Enscore, Russell E.; Ogen-Odoi, Asaph; Atiku, Linda A.; Akol, Anne; Gage, Kenneth L.; Eisen, Rebecca J.In Uganda, the West Nile region is the primary epidemiologic focus for plague. The aims of this study wereto 1) describe flea–host associations within a plague-endemic region of Uganda, 2) compare flea loads between villages with or without a history of reported human plague cases and between sampling periods, and 3) determine vector loads on small mammal hosts in domestic, peridomestic, and sylvatic settings. We report that the roof rat, Rattusrattus, is the most common rodent collected in human dwellings in each of the 10 villages within the two districts sampled. These rats were commonly infested with efficient Y. pestis vectors, Xenopsylla cheopis and X. brasiliensis in Arua and Nebbi districts, respectively. In peridomestic and sylvatic areas in both districts, the Nile rat, Arvicanthus niloticus, was the most abundant rodent and hosted the highest diversity of flea species. When significant temporal differences in flea loads were detected, they were typically lower during the dry month of January. We did not detect any significant differences in small mammal abundance or flea loads between villages with our without a history of human plague, indicating that conditions during inter-epizootic periods are similar between these areas. Future studies are needed to determine whether flea abundance or species composition changes during epizootics when humans are most at risk of exposure.Item Identification of Flea Blood Meals Using Multiplexed Real-Time Polymerase Chain Reaction Targeting Mitochondrial Gene Fragments(The American journal of tropical medicine and hygiene, 2009) Woods, Michael E.; Montenieri, John A.; Eisen, Rebecca J.; Zeidner, Nordin S.; Borchert, Jeff N.; Laudisoit, Anne; Babi, Nackson; Atiku, Linda A.; Enscore, Russell E.; Gage, Kenneth L.is found in the West Nile region of Uganda and Democratic Republic of the Congo where flea vectors are often found inhabiting homes. We have developed a multiplexed, real-time polymerase chain reaction assay targeting mitochondrial genes that is capable of detecting blood meal sources in fleas collected off-host in East Africa. Laboratory tests showed that the assay is specific for the intended targets and has a detection limit below one picogram of DNA. Testing of wild-caught fleas from the Democratic Republic of Congo suggests that humans are at significant risk from flea-borne disease and implicates domestic animals including cats, chickens, and the black rat as potential sources of human exposure to fleas and flea-borne diseases. Future application of the assay will help us better define the ecology of plague in East Africa to implement effective control measures to combat the spread of disease.