Terry L. Yates

Distribution of non-telomeric sites of the (TTAGGG)n telomeric sequence in vertebrate chromosomes

The intrachromosomal distribution of non-telomeric sites of the (TTAGGG)n telomeric repeat was determined for 100 vertebrate species. The most common non-telomeric location of this sequence was in the pericentric regions of chromosomes. A variety of species showed relatively large amounts of this sequence present within regions of constitutive heterochromatin. We discuss possible relationships between the non-telomeric distribution of the (TTAGGG)n sequence and the process of karyotype evolution, during which these sites may provide potential new telomeres.

The Ecology and Evolutionary History of an Emergent Disease: Hantavirus Pulmonary Syndrome

I the spring of 1993, a previously undescribed disease emerged in the Southwest, killing 10 people during an 8-week period in May and June. Early during an infection, victims experienced flu-like symptoms for several days, but their condition suddenly and rapidly deteriorated as their lungs filled with fluids; death usually occurred within hours of the onset of this crisis period. There was no cure, no successful medication or treatment, and the disease agent (virus, bacterium, or toxin) was completely unknown. For the first few weeks, the mortality rate was 70%. Researchers from many disciplines immediately focused on the outbreak, attempting to identify the agent and understand the causes and dynamics of the disease. Within weeks, scientists at the Centers for Disease Control and Prevention (CDC) identified the agent as a previously unknown hantavirus (Bunyaviridae), subsequently named Sin Nombre virus, or SNV (Nichol et al. 1993). Because hantaviruses were known to be transmitted by rodents, investigators undertook an intensive small mammal field sampling campaign in the Four Corners region of New Mexico and Arizona. Shortly thereafter, CDC identified the viral reservoir host as a common and widely distributed rodent, the deer mouse, Peromyscus maniculatus (figure 1; Childs et al. 1994). During the identification period, on the medical side, physicians and medical staff made rapid progress in developing treatment methods to stabilize and sustain patients through the crisis period, thereby substantially improving patient survivorship; nonetheless, the mortality rate fell only to about 40%, where it remains today. The emergence of this new disease prompted many questions about its history, causes, and dynamics. Was this a newly Terry L. Yates (e-mail: tyates@unm.edu) is a professor in the Departments of Biology and Pathology at the University of New Mexico, Albuquerque, NM 87131. Cheryl A. Parmenter, Robert R. Parmenter, John R. Vande Castle, Jorge Salazar-Bravo, and Jonathan L. Dunnum are with the Department of Biology and the Museum of Southwestern Biology, University of New Mexico. James N. Mills, Thomas G. Ksiazek, Stuart T. Nichol, and Joni C. Young are with the Centers for Disease Control and Prevention, Atlanta, GA 30333. Charles H. Calisher and Barry J. Beaty are with the Arthropod-borne and Infectious Diseases Laboratory, Foothills Campus, Colorado State University, Fort Collins, CO 80523. Kenneth D. Abbott is with the Department of Biology, Yavapai College, Prescott, AZ 86301. Michael L. Morrison is with the Department of Wildlife and Fisheries Sciences, University of Arizona, Tuscon, AZ 85721. Robert J. Baker is with the Department of Biology and The Museum, Texas Tech University, Lubbock, TX 79409. Clarence J. Peters is with the Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555.

Guidelines for Working with Rodents Potentially Infected with Hantavirus

Because of the high morbidity and mortality associated with hantavirus pulmonary syndrome and the possibility of aerosol transmission of hantaviruses, persons handling known reservoir species in the field, laboratory, or classroom should take special precautions to minimize the risk of infection. We provide specific guidelines for personal safety while trapping, handling and releasing, transporting, sampling, and performing necropsy on potentially infected rodents or teaching field classes in areas occupied by reservoir species. Special consideration should be given to respiratory protection, choice and use of disinfectants, decontamination of instruments and traps, proper disposal of infectious wastes, and preservation and shipment of samples intended for hantavirus testing. Precautionary testing of wild rodents used to start laboratory colonies is recommended. Although we specifically address hantaviruses, the procedures described are applicable for any study of populations of small mammals when an infectious zoonotic agent transmissible by aerosol and capable of causing high morbidity and mortality is involved.

SMALL‐MAMMAL DENSITY ESTIMATION: A FIELD COMPARISON OF GRID‐BASED VS. WEB‐BASED DENSITY ESTIMATORS

Statistical models for estimating absolute densities of field populations of animals have been widely used over the last century in both scientific studies and wildlife management programs. To date, two general classes of density estimation models have been developed: models that use data sets from capture–recapture or removal sampling techniques (often derived from trapping grids) from which separate estimates of population size (N) and effective sampling area (Â) are used to calculate density (D = N/Â); and models applicable to sampling regimes using distance-sampling theory (typically transect lines or trapping webs) to estimate detection functions and densities directly from the distance data. However, few studies have evaluated these respective models for accuracy, precision, and bias on known field populations, and no studies have been conducted that compare the two approaches under controlled field conditions. In this study, we evaluated both classes of density estimators on known densities of e...

Experimental Evidence for Reduced Rodent Diversity Causing Increased Hantavirus Prevalence

Emerging and re-emerging infectious diseases have become a major global environmental problem with important public health, economic, and political consequences. The etiologic agents of most emerging infectious diseases are zoonotic, and anthropogenic environmental changes that affect wildlife communities are increasingly implicated in disease emergence and spread. Although increased disease incidence has been correlated with biodiversity loss for several zoonoses, experimental tests in these systems are lacking. We manipulated small-mammal biodiversity by removing non-reservoir species in replicated field plots in Panama, where zoonotic hantaviruses are endemic. Both infection prevalence of hantaviruses in wild reservoir (rodent) populations and reservoir population density increased where small-mammal species diversity was reduced. Regardless of other variables that affect the prevalence of directly transmitted infections in natural communities, high biodiversity is important in reducing transmission of zoonotic pathogens among wildlife hosts. Our results have wide applications in both conservation biology and infectious disease management.

Satellite imagery characterizes local animal reservoir populations of Sin Nombre virus in the southwestern United States

The relationship between the risk of hantaviral pulmonary syndrome (HPS), as estimated from satellite imagery, and local rodent populations was examined. HPS risk, predicted before rodent sampling, was highly associated with the abundance of Peromyscus maniculatus, the reservoir of Sin Nombre virus (SNV). P. maniculatus were common in high-risk sites, and populations in high-risk areas were skewed toward adult males, the subclass most frequently infected with SNV. In the year after an El Niño Southern Oscillation (ENSO), captures of P. maniculatus increased only in high-risk areas. During 1998, few sites had infected mice, but by 1999, 18/20 of the high-risk sites contained infected mice and the crude prevalence was 30.8%. Only 1/18 of the low-risk sites contained infected rodents, and the prevalence of infection was lower (8.3%). Satellite imagery identified environmental features associated with SNV transmission within its reservoir population, but at least 2 years of high-risk conditions were needed for SNV to reach high prevalence. Areas with persistently high-risk environmental conditions may serve as refugia for the survival of SNV in local mouse populations.

Hantavirus in Northern Short-tailed Shrew, United States

Phylogenetic analyses, based on partial medium- and large-segment sequences, support an ancient evolutionary origin of a genetically distinct hantavirus detected by reverse transcription–PCR in tissues of northern short-tailed shrews (Blarina brevicauda) captured in Minnesota in August 1998. To our knowledge, this is the first evidence of hantaviruses harbored by shrews in the Americas.

Mammalian Reservoirs of Arenaviruses

Arenaviruses are negative-stranded RNA viruses that have been isolated from several species of mammals in various parts of the world. With two exceptions, these viruses have all been isolated from rodents of the family Muridae — sensu Musser and Carleton (1993). Tacaribe virus was originally isolated from fruit-eating bats of the genus Artibeus, while Sabia virus has no known wild reservoir. Arenavirus infections in their rodent reservoirs are characterized by persistent shedding of infectious virus in the urine (Johnson 1970).

Traveling waves of infection in the hantavirus epidemics.

Traveling waves are analyzed in a model of the hantavirus infection in deer mice. The existence of two kinds of wave phenomena is predicted. An environmental parameter governs a transition between two regimes of propagation. In one of them the front of infection lags behind at a constant rate. In the other, fronts of susceptible and infected mice travel at the same speed, separated by a constant delay. The dependence of the delay on system parameters is analyzed numerically and through a piecewise linearization.

DEMOGRAPHIC FACTORS ASSOCIATED WITH PREVALENCE OF ANTIBODY TO SIN NOMBRE VIRUS IN DEER MICE IN THE WESTERN UNITED STATES

We used long-term data collected for up to 10 yr (1994–2004) at 23 trapping arrays (i.e., webs and grids) in Arizona, Colorado, Montana, and New Mexico to examine demographic factors known or suspected to be associated with risk of infection with Sin Nombre virus (SNV) in its natural host, the deer mouse (Peromyscus maniculatus). Gender, age (mass), wounds or scars, season, and local relative population densities were statistically associated with the period prevalence of antibody (used as a marker of infection) to SNV in host populations. Nevertheless, antibody prevalence and some of the risk factors associated with antibody prevalence, such as relative population density, gender bias, and prevalence of wounding, varied significantly among sites and even between nearby trapping arrays at a single site. This suggests that local microsite-specific differences play an important role in determining relative risk of infection by SNV in rodents and, consequently, in humans. Deer mouse relative population density varied among sites and was positively and statistically associated with infection prevalence, an association that researchers conducting shorter-term studies failed to demonstrate. Both wounding and antibody prevalence increased with mass class in both males and females; this increase was much more pronounced in males than in females and wounding was more frequent in adult males than in adult females. Prevalence of wounding was greatest among seropositive deer mice, regardless of mass class, but many deer mice without detectable wounds or scars eventually became infected. Many of these patterns, which will be useful in the development of predictive models of disease risk to humans, were only detected through the application of data collected over a long (10-yr) period and with abundant replication.