Peste

Animals 2011, 1, 242-255; doi:10.3390/ani1020242
OPEN ACCESS

animals
ISSN 2076-2615 www.mdpi.com/journal/animals Review

Plague: Infections of Companion Animals and Opportunities for Intervention
Petra C.F. Oyston * and Diane Williamson Biomedical Sciences, Dstl Porton Down, Salisbury, Wiltshire, SP4 0JQ, UK; E-Mail: dewilliamson@dstl.gov.uk * Author to whom correspondence should beaddressed; E-Mail: pcoyston@dstl.gov.uk; Tel: +44-1980-613641. Received: 19 May 2011; in revised form: 20 June 2011 / Accepted: 20 June 2011 / Published: 21 June 2011

Simple Summary: Plague is a notorious disease of humans, typically transmitted from rodents to man by the bite of infected fleas. However, plague can also be brought into the home by domestic animals. Cats are acutely susceptible toplague and can pose a significant hazard to close contacts. Dogs are relatively resistant to plague, but can import infected fleas into the home. This review discusses options available for vaccinating cats and dogs, to protect the animals, their owners and veterinarians from infection. Abstract: Plague is a zoonotic disease, normally circulating in rodent populations, transmitted to humans mostcommonly through the bite of an infected flea vector. Secondary infection of the lungs results in generation of infectious aerosols, which pose a significant hazard to close contacts. In enzootic areas, plague infections have been reported in owners and veterinarians who come into contact with infected pets. Dogs are relatively resistant, but can import infected fleas into the home. Cats are acutelysusceptible, and can present a direct hazard to health. Reducing roaming and hunting behaviours, combined with flea control measures go some way to reducing the risk to humans. Various vaccine formulations have been developed which may be suitable to protect companion animals from contracting plague, and thus preventing onward transmission to man. Since transmission has resulted in a number offatal cases of plague, the vaccination of domestic animals such as cats would seem a low cost strategy for reducing the risk of infection by this serious disease in enzootic regions. Keywords: plague; vaccine; cats; dogs; fleas

Animals 2011, 1 1. Yersinia pestis

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Plague is caused by the bacterial pathogen Yersinia pestis, a Gram-negative non-motile, non-spore-forming coccobacillus. It iscapable of growth between 4 and 40 °C, but grows optimally at 28–30 °C. Growth is somewhat slow, requiring 48 h on rich media for colony formation. The organism exhibits a range of nutritional requirements, having mutated genes in many metabolic pathways [1,2]. Y. pestis is a clonal derivative of the enteropathogen Yersinia pseudotuberculosis estimated to have emerged relatively recently inevolutionary terms, between 1,500 and 20,000 years ago [3]. Historically, three biovars have been recognised, Antiqua, Medievalis and Orientalis, differentiated by their ability to ferment glycerol and to reduce nitrate. Strains belonging to all the biovars are virulent and it has been suggested that they are linked to separate pandemics. Nowadays biovar Antiqua strains are isolated in Africa, and maybe descended from the bacteria that caused the first pandemic. Medievalis strains are isolated in Central Asia and may be related to the bacteria of the second pandemic. Orientalis strains are widespread and appear to be the cause of the current pandemic [4]. However, modern taxonomic methods have shown the nomenclature to be more complicated than originally described (reviewed by [5]), and manyresearchers now favour the inclusion of a fourth biovar, Pestoides, first used for strains isolated from vole populations in the Former Soviet Union. However, despite the advent of modern molecular taxonomy methods e.g., [6], the inherent variability of Y. pestis strains still provokes discussion as to the best way to divide the species (reviewed by [5]). A comparison of the Y. pestis and Y....