Rodent Biology and Management; Abstracts of papers presented at the International Conference on Rodent Biology and Management, held at Beijing, China, 5-9 October 1998

Farm Management,

Ecology, Impacts, and Management of Invasive Rodents in the United States

Approximately 42% of all mammalian species in the world are rodents, amounting to about 2277 species (Wilson and Reeder 2005). Rodents have adapted to all lifestyles: terrestrial, aquatic, arboreal, and fossorial (underground). Most species are small, secretive, nocturnal, adaptable, and have keen senses of touch, taste, and smell. For most species of rodents, the incisors continually grow throughout their life span, requiring constant gnawing to keep the incisors sharp and at an appropriate length. This can result in extensive damage to seeds, fruits, field crops, structures, wires, and insulation. Rodents are known for their high reproductive potential; however, there is much variability between species as to the age at first reproduction, size of litters, and the number of litters per year. All these characteristics make many rodent species ideal invaders. Rodents have ecological, scientific, social, and economic values (Witmer et al. 1995; Dickman 1999). Rodents are important in seed and spore dispersal, pollination, seed predation, energy and nutrient cycling, the modification of plant succession and species composition, and as a food source for many predators. Additionally, some species provide food and fur for human uses. Hence, the indiscriminate removal of native rodents from ecosystems, including agroecosystems, is not the best management option in many cases (Villa-Cornejo et al. 1998; Aplin and Singleton 2003; Brakes and Smith 2005)

The role of climate change, wildfire and human interference in the potential spread of Sin Nombre Hantavirus in North America

Sin Nombre hantavirus is a rare rodent-borne pathogen that causes Hantavirus Cardiopulmonary Syndrome (HCPS), a disease with a 35% fatality rate in humans. The main rodent host of Sin Nombre hantavirus is the deer mouse (Peromyscus maniculatus), one of the most prolific, best studied and highly adaptable rodent species in North America. Deer mice are hyper-reservoirs, carrying Sin Nombre virus, plague (Yersinia pestis) and the Peromyscus species carry Lyme disease. Although deer mice have been shown to react positively to wildfire, current assessments of Sin Nombre hantavirus risk to humans and climate change do not consider increasing fire risk. In order to assess the effects of wildfire, human interference and climate change on the human-pathogen risk of Sin Nombre hantavirus in North America, a cross-disciplinary literature review was performed. Climate change and human interference has already increased wildfire incidents, extended wildfire seasons, and intensified drought; all of which are expected to worsen as climate change progresses. Deer mice population’s positive reaction to increased fire and preference for burned areas was found to be significant enough to warrant better monitoring of wildfire incidents across the United States, especially in areas of fragmentation and ecosystem disruption as these conditions may lead to increased incidence of Sin Nombre hantavirus. Future pathogenic hotspots may be determined by creating a comprehensive monitoring system using remote sensing of total fire (wildfire and agricultural burning) across North America which currently does not exist. Expansion of public health and increased testing in North America is recommended to reduce risk

Oral Delivery of Human Biopharmaceuticals, Autoantigens and Vaccine Antigens Bioencapsulated in Plant Cells

Among 12 billion injections administered annually, unsafe delivery leads to \u3e20 million infections and \u3e100 million reactions. In an emerging new concept, freeze-dried plant cells (lettuce) expressing vaccine antigens/biopharmaceuticals are protected in the stomach from acids/enzymes but are released to the immune or blood circulatory system when plant cell walls are digested by microbes that colonize the gut. Vaccine antigens bioencapsulated in plant cells upon oral delivery after priming, conferred both mucosal and systemic immunity and protection against bacterial, viral or protozoan pathogens or toxin challenge. Oral delivery of autoantigens was effective against complications of type 1diabetes and hemophilia, by developing tolerance. Oral delivery of proinsulin or exendin-4 expressed in plant cells regulated blood glucose levels similar to injections. Therefore, this new platform offers a low cost alternative to deliver different therapeutic proteins to combat infectious or inherited diseases by eliminating inactivated pathogens, expensive purification, cold storage/transportation and sterile injections

Prevention of Immune Cell Apoptosis as Potential Therapeutic Strategy for Severe Infections

Lymphocyte apoptosis prevention may improve survival

Rats, Mice, and People: Rodent Biology and Management

Farm Management,

THE PROSPECTS AND ASSOCIATED CHALLENGES FOR THE BIOLOGICAL CONTROL OF RODENTS

Biological control using macro- or micro-parasites is a promising research area for control of rodents. The largest impediment to progress is a dearth of high quality research, under field conditions, on wild rodents and their diseases. A major challenge is to identify a candidate control agent which is sufficiently pathogenic, has a high transmission rate and is target specific. Once this has been done, ecological studies of both the host and the disease agent, and of the epidemiology of transmission, are required. Whether the desired pathogenicity is via increased mortality and/or reduced fertility will depend on the agent and on the dynamics of the pest species in particular agricultural systems. Overall, the best prospects for the biological control of rodents lies with agents that reduce fertility rather than increase mortality. The development of immuno-contraception using a virus as a vector is proffered as the most promising generic approach for the biological control of rodent pests

Innate Immune Response To Yersinia Pestis

This study demonstrates the various aspects of host immune response to Yersinia pestis. Y. pestis, the causative agent plague is mainly a rodent pathogen but is usually transmitted to humans via infected flea bite. After transmission to mammalian hosts, Y. pestis evades the host innate immune response and develops a systemic infection. Mast cells are recognized as the powerful sentinel cells responsible for controlling the early responses to a disease. We sought to determine whether mast cells are involved in the early innate immune response to Y. pestis and thus blocking mast cell degranulation would alter the outcome of infection. Mast cells in resistant young B10.T(6R) mice were depleted by use of anti-c-kit (ACK2) antibodies during Y. pestis infection. Our results demonstrated that Y. pestis infected anti-C kit treated mice showed lower survival rate than Y. pestis infected control mice suggesting mast cells are involved in early innate immune responses to Y. pestis. The other study is focused to understand the difference in the outcome of infection induced by endemic KIM5 and pandemic CO92 strains of Y. pestis. Both of these Yersinia strains have functional Type Three Secretion Systems (T3SS), which secretes effector molecules like Yersinia outer proteins (Yops) into the host cytosol to modulate the host immune response. KIM5 and CO92 strains express different isoforms of one of the Yop effectors, YopJ, which has been shown to inhibit NF-κB and MAPK activation in mammalian cells. The YopJ isoform in Y. pestis KIM5 has two amino acid substitutions, F177L and K206E, which are not present in YopJ proteins of Y. pestis CO92. We show that young B10.T (6R) mice that are resistant to the KIM5 strain (LD50 of 14,000 CFUs) were susceptible to the CO92 strain (LD50 of 17 CFUs). A set of KIM5 isogenic strains expressing various YopJ isoforms allowed a demonstration that amino acid differences in YopJ were largely responsible for the increased virulence of the pandemic strain, CO92 in the B10.T (6R) mice