ABSTRACT

Identification of the plague reservoir in an endemic area of Zambia

Bernard M. Hang'ombe^I; I. Nakamura^II; D. Kaile^III; A.S. Mweene^I; K.L. Samui^I; B.S. Kilonzo^IV; H. Sawa^II; C. Sugimoto^II; B. Wren^V

^ISchool of Veterinary Medicine, University of Zambia, Zambia
^IIResearch Center for Zoonosis Control, Hokkaido University, Japan
^IIINamwala District Medical Officer, Namwala District, Zambia
^IVSokoine University of Agriculture, United Republic of Tanzania
^VSchool of Hygiene and Tropical Medicine, London, United Kingdom

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Yersinia pestis, the bacterial agent of plague, is primarily a parasite of wild rodents that persists in permanent, discrete enzootic foci throughout the world. The disease is transmitted in humans by bites from fleas of wildlife rodent species. Therefore surveillance is the ultimate public health solution through plague detection in domestic dogs, other carnivores and wild rodents. The investigations of die-offs amongst plague-susceptible colonial rodents are also significant to determine the presence of Y. pestis in a susceptible population.

This study details the identification of the plague reservoir in a suspected endemic area of Zambia. The study was undertaken through rodent investigation for the presence of Y. pestis. A total of 105 rodents were sampled routinely and during a suspected plague period. On dissection 4 (3.81%, 95% CI: 1.23-10.0) rodents sampled during an outbreak showed signs of spleen enlargement. The blood, liver, lymph nodes and spleen of each rodent were subjected to culture on 6% sheep blood agar and MaCconkey agar. Colonies obtained were identified as Y. pestis by colony morphologic features, biochemical profiles, mouse inoculation assay and polymerase chain reaction (PCR). The PCR primers used targeted the Y. pestis plasminogen activator gene, chromosomal ferric iron uptake regulation gene and the outer membrane protein B gene.

The isolates were also subjected to antibiotic sensitivity tests using the disk diffusion method on Mueller-Hinton agar with sensitivity being observed with ampicillin, amoxicillin, chloramphenicol, gentamycin, streptomycin, tetracycline and trimethoprim-sulfamethoxazole. The findings, identifies a natural reservoir of Y. pestis in Zambia providing the public health officials with a definite host for the control strategy.

Correspondence to:
Bernard Hang'ombe
PO Box 32379, Lusaka, Zambia
Email: bernard.hang'ombe@sacids.org

Note: Proceedings of the Conference of the Southern African Centre for Infectious Disease Surveillance 'One Health' held at the National Institute for Communicable Diseases, Johannesburg, July 2011.