Sin Nombre Virus and Rodent Species Diversity: A Test of the Dilution and Amplification Hypotheses

BACKGROUND:Species diversity is proposed to greatly impact the prevalence of pathogens. Two predominant hypotheses, the "Dilution Effect" and the "Amplification Effect", predict divergent outcomes with respect to the impact of species diversity. The Dilution Effect predicts that pathogen prevalence will be negatively correlated with increased species diversity, while the Amplification Effect predicts that pathogen prevalence will be positively correlated with diversity. For many host-pathogen systems, the relationship between diversity and pathogen prevalence has not be empirically examined. METHODOLOGY/PRINCIPAL FINDINGS:We tested the Dilution and Amplification Effect hypotheses by examining the prevalence of Sin Nombre virus (SNV) with respect to diversity of the nocturnal rodent community. SNV is directly transmitted primarily between deer mice (Peromyscus maniculatus). Using mark-recapture sampling in the Spring and Fall of 2003-2005, we measured SNV prevalence in deer mice at 16 landscape level sites (3.1 hectares each) that varied in rodent species diversity. We explored several mechanisms by which species diversity may affect SNV prevalence, including reduced host density, reduced host persistence, the presence of secondary reservoirs and community composition. We found a negative relationship between species diversity and SNV prevalence in deer mice, thereby supporting the Dilution Effect hypothesis. Deer mouse density and persistence were lower at sites with greater species diversity; however, only deer mouse persistence was positively correlated with SNV prevalence. Pinyon mice (P. truei) may serve as dilution agents, having a negative effect on prevalence, while kangaroo rats (Dipodomys ordii), may have a positive effect on the prevalence of SNV, perhaps through effects on deer mouse behavior. CONCLUSIONS/SIGNIFICANCE:While previous studies on host-pathogen systems have found patterns of diversity consistent with either the Dilution or Amplification Effects, the mechanisms by which species diversity influences prevalence have not been investigated. Our study indicates that changes in host persistence, coupled with interspecific interactions, are important mechanisms through which diversity may influence patterns of pathogens. Our results reveal the complexity of rodent community interactions with respect to SNV dynamics

A Comparative Study of Aquatic Invertebrates and Water Quality of the Animas River, the Los Pinos River and the La Plata River

With climate change and multiple other factors affecting our planet as a whole, water is likely the most fragile and finite resource available to us and we must make it a priority for our generation. Of the many water bodies scattered across Colorado, the Animas, Los Pinos, and La Plata Rivers are three of the larger rivers in La Plata County. I analyzed water quality on each of these using traditional water quality tests as well as invertebrate sampling. Due to differences in land use practices, I predict that of the three rivers sampled, that the La Plata River will have the best water quality, with the Los Pinos having the second highest, and the Animas having the lowest water quality. Sampling methods consisted of measuring invertebrate populations on three sites per river, each spaced one half mile apart, as well as other water quality data consisting of pH, dissolved oxygen, and turbidity. A Pollution Tolerance Index (PTI) value was also calculated based on the invertebrate samples. All water quality tests followed manufacturer instruction and invertebrates were sampled using the Kick-net method. Sample sites were chosen by similar site characteristics, for example dominant substrate and dominant vegetation type. Results showed a variety of invertebrate densities and species richness values which created PTI values for each of the rivers being 59.333, 213.917, and 292.125 for the Animas, Los Pinos, and Animas Rivers respectively (larger values indicate higher water quality). Dissolved oxygen, turbidity, and pH values were within a normal range for the most part with averages following the same trend as the PTI values with the La Plata having the highest quality values, followed by the Los Pinos, and the Animas River showing the lowest averages. Overall, the La Plata River showed the highest water quality followed by the Los Pinos River, and the Animas River showed the lowest water quality. Water conservation and preservation should be our top priorities and continuous monitoring is required to maintain this gift

EVALUATING THE IMPACTS OF BLACK-TAILED PRAIRIE DOGS ON VEGETATION IN TRADITIONAL AND NON-TRADITIONAL HABITATS

The wildland-urban interface (WUI), defined as areas where human development meets undeveloped wildland (Radeloff et al. 2005), is a focal area for humanwildlife interactions in many communities of the western United States, particularly in those areas that have experienced rapid and expansive human population growth. Since 1960, conversion of rural to urban land has more than doubled in the United States (Theobald 2001). The eastern front range of the Rocky Mountains has experienced one of the most rapid urban expansions in the country, with approximately 110,000 hectares of undeveloped rural land being converted to human-developed land every year between 1992 and 1997 (Obermann et al. 2000, Maestas et al. 2001). In grassland remnants within the WUI, many native wildlife species, including black-tailed prairie dogs (Cynomys ludovicanus), persist and land managers are faced with decisions about how to manage these wildlife population

Human Encroachment on Elk Winter Ranges in The La Plata Mountain Region of Southwestern, Colorado Where Migration is Obligatory

Migratory ungulates, such as Rocky Mountain Elk (Cervus elaphus) occupy a “keystone” ecosystem role, often defining terrestrial processes (Houston 1982; Sinclair 2003). Because of their critical ecosystem role, concern for the changing behavior in the elk’s migratory habits is mounting (Schaller 1988; Berger 2004; Johnson et al. 2005). Often this change in behavior can be attributed to human encroachment. Human development and activities have caused the natural migration travel corridors to become reduced and limited in certain areas, as well as the winter ranges that these ungulates utilize. Using digital aerial photographs from the years 1993 and 2007 as well as migration information from the National Diversity Information Source (NDIS), I was be able to overlay the elk migration and winter range data on top of the aerial photos. This allowed me to calculate the difference in human development within the elk wintering grounds over the 14 year span. Upon calculating the difference in development in 2007 and compared it to 1993, I was able to determine that there has been a significant amount of development that has occurred within the elk wintering grounds over the past 14 years within these particular study areas. From the year 1993 to 2007 there was an 83.31% increase in the amount of buildings/structures and a 150.10% increase in total road length within the Lightner Creek and Durango West study areas. Being that my results showed that there has been a significant amount of human development within elk wintering grounds and that this is just one small case among a much larger scale, it is imperative that we monitor human development on crucial wintering grounds for both elk and other migratory ungulates

Water for the World, Testing the Effectiveness of Homemade Water Filters at Removing Disease Causing Bacteria

Bacterially contaminated water is a common source of infection, in developing countries, for various diarrheal diseases, which infect millions annually. Therefore water filtration that is booth cheap and effective has recently gained attention for its importance in preventing these diseases. The purpose of this study was to examine how effective homemade ceramic filters and sari cloth might be at removing bacteria. The study uses E. coli specifically because of the current lack of research on how effective these cheap filters might be at removing it. Ceramic filters were made using equal part terracotta and coffee grounds, and firing until the coffee burned away; a silk sari cloth was used. Nutrient broth was inoculated with non-pathogenic E. coli to a Mc. Farland standard of 5. The filters were then sterilized and 10 ml of broth was run through each of the filters, another 10 ml was given no filtration. The filtered broth was then pipetted onto 15 nutrient plates for each treatment. The nutrient plates were then incubated and the colony numbers recorded. The ceramic filters resulted in significantly less growth than both the control and the sari cloth, p < .01. The sari cloth resulted in significantly less growth than the control, p< .03. The ceramic filter resulted in approximately 58% less colony growth than the control, and the sari cloth filter resulted in 6.6% less colony growth

EVALUATING THE IMPACTS OF BLACK-TAILED PRAIRIE DOGS ON VEGETATION IN TRADITIONAL AND NON-TRADITIONAL HABITATS

The wildland-urban interface (WUI), defined as areas where human development meets undeveloped wildland (Radeloff et al. 2005), is a focal area for humanwildlife interactions in many communities of the western United States, particularly in those areas that have experienced rapid and expansive human population growth. Since 1960, conversion of rural to urban land has more than doubled in the United States (Theobald 2001). The eastern front range of the Rocky Mountains has experienced one of the most rapid urban expansions in the country, with approximately 110,000 hectares of undeveloped rural land being converted to human-developed land every year between 1992 and 1997 (Obermann et al. 2000, Maestas et al. 2001). In grassland remnants within the WUI, many native wildlife species, including black-tailed prairie dogs (Cynomys ludovicanus), persist and land managers are faced with decisions about how to manage these wildlife population

Contact heterogeneity in deer mice: implications for Sin Nombre virus transmission

Heterogeneities within disease hosts suggest that not all individuals have the same probability of transmitting disease or becoming infected. This heterogeneity is thought to be due to dissimilarity in susceptibility and exposure among hosts. As such, it has been proposed that many host–pathogen systems follow the general pattern whereby a small fraction of the population accounts for a large fraction of the pathogen transmission. This disparity in transmission dynamics is often referred to as ‘20/80 Rule’, i.e. approximately 20 per cent of the hosts are responsible for 80 per cent of pathogen transmission. We investigated the role of heterogeneity in contact rates among potential hosts of a directly transmitted pathogen by examining Sin Nombre virus (SNV) in deer mice (Peromyscus maniculatus). Using foraging arenas and powder marking, we documented contacts between wild deer mice in Great Basin Desert, central Utah. Our findings demonstrated heterogeneity among deer mice, both in frequency and in duration of contacts with other deer mice. Contact dynamics appear to follow the general pattern that a minority of the population accounts for a majority of the contacts. We found that 20 per cent of individuals in the population were responsible for roughly 80 per cent of the contacts observed. Larger-bodied individuals appear to be the functional group with the greatest SNV transmission potential. Contrary to our predictions, transmission potential was not influenced by breeding condition or sex