Bat Species Presence in Southwestern Montana

Published information on bat species presence in many parts of Montana is limited. Our study was initiated to gather data on the distribution of bat species found in the southwestern part of the state. We captured 106 individuals of eight bat species in mist-nets at 15 water sources in southwestern Montana during July through August 2003-2006. The western long-eared myotis (Myotis evotis) was the most frequently captured species and detected at over half the sites surveyed. Other common species captured across numerous sites included little brown myotis (M. lucifugus), hoary bats (Lasiurus cinereus), and big brown bats (Eptesicus fuscus). These species are apparently broadly distributed throughout southwestern Montana, occurring in a variety of habitat types. Our study provides some much needed baseline data on bat distribution in southwestern Montana

Examining Antibody to Sin Nombre Virus in Rodents Associated with Peridomestic Habitats in North East Montana

Hantaviruses are rodent-borne pathogens that produce chronic persistent infections in their reservoir hosts.  Sin Nombre virus (SNV) is a type of hantavirus carried by deer mice (Peromyscus maniculatus).  Infected deer mice shed virus in urine, saliva, or feces, and human contact with the virus can lead to a serious illness called hantavirus cardiopulmonary syndrome. Most studies examining SNV in the rodent host have been conducted in natural settings where human contact with the virus is unlikely.  This study, performed in a peridomestic setting (in and around buildings), where contact with the virus is more likely, adds data to a previous study in west central Montana.  Mice were live trapped for 3 consecutive nights every two weeks from May to August 2014, at 2 sites in NE Montana.  Captured individuals were ear tagged,and species, body mass, sex, reproductive condition, presence of scars or wounds, and location of capture were recorded into a field journal.  Blood samples were collected from the retro-orbital sinus of each captured animal.  These blood samples were frozen until they could be analyzed.  Blood samples were analyzed for antibodies (IgM) to SNV.  Deer mice were the most common species captured at both study sites and antibody positive deer mice were detected at both study sites.  Antibody prevalence was found to be variable both spatially and temporally with highest prevalence in the middle of the summer

Survey of Colorado Tick Fever Virus Presence in Montana Deer Mice and Wood Ticks

Colorado Tick Fever Virus (CTFV) is carried by Rocky Mountain wood ticks (Demacetori andersoni). Its double-stranded RNA genome is comprised of twelve segments. In humans, it causes a variety of flu-like symptoms, including fever, headache, sensitivity to light, and muscle soreness. Because the symptoms often mimic the flu and other common diseases, it is often overlooked during clinical diagnosis. Deer mice (Peromyscus manisculatus) are considered to be a reservoir for the virus. This study aimed to determine the prevalence of CTFV nucleic acid in mouse blood. The whole blood samples were screened from Polson and Gregson, Montana. These samples were collected both prior to the study for a separate Hantavirus study as well as during the study. Only Hantavirus negative samples were screened. In addition, ninety ticks were collected. While these have not been tested, they provide another sample set to screen for the presence of CTFV.https://digitalcommons.mtech.edu/urp_aug_2017/1001/thumbnail.jp

Grazing Effects on Deer Mice with Implications to Human Exposure to Sin Nombre Virus

We examined the effects of grazing on deer mouse (Peromyscus maniculatus) movements into buildings using passive integrated transponder (PIT) technology and small simulated buildings located on 0.6-ha treatment (grazing) and control (no grazing) plots. Twelve experimental 9-day trials were conducted over the course of the study. During these trials, mouse movements into buildings were monitored during three time periods (each 3 days in length). In the treatment plots these time periods corresponded to pre-grazing, grazing, and post grazing by horses. The number of individual deer mice entering buildings over time decreased in both the grazed and control plots during the 9 days of each experiment. The number of entrances per/individual among the pre-grazing, grazing and post grazing periods was different between control and treated plots for both males and females. The distribution of entrances/individual among the three periods differed between males and females in both grazed and control plots. The habitat modification caused by grazing appeared to reduce deer mouse activity (entrances/individual) in buildings but does not affect the number of mice entering buildings. Reducing vegetative cover by grazing or mowing may not affect the number of mice investigating small structures but grazing creates different activity patterns in the structures for neighboring deer mice

Effect of Rock Cover on Small Mammal Abundance in a Montana Grassland

We examined the influence of rock cover, as an indicator of presumable retreat site availability on the abundance of deer mice (Peromyscus maniculatus) and prevalence of Sin Nombre virus (SNV) using long-term live trapping and habitat data from three live trapping grids and a shortterm (three month), spatially replicated study across three slopes in Cascade County, Montana. In our long-term study, we found that deer mice were more abundant at a live-trapping grid with greater rock cover, than two grids with less rock cover. There was a non-significant trend (P = 0.053) for deer mice to be more abundant in rocky sites in the short term study. In the long-term study, average SNV antibody prevalence among deer mice was slightly greater (5.0 vs. 3.5 % on average) at the live trapping grid with more rock cover, than the grid with less rock cover. We were unable to demonstrate differences in SNV antibody prevalence among treatments in the short-term study. Further studies are needed to elucidate the multiple determinants of deer mouse abundance and SNV prevalence in grassland ecosystem and other habitat types

Firefighter’s Workers’ Compensation Claims in Montana, 2007-2017: A Cost Analysis

The objective of this study was to examine costs associated with workers’ compensation claims from firefighters in Montana. Workers’ compensation claims data were obtained from the Montana Department of Labor and Industry. The highest proportion of total benefit amount dollars was paid to male firefighters (93.7%), public employees (84.8%), and those who were 45-54 years of age at time of injury (23.9%). Part-time employees represented the employment category receiving the highest total benefit amount ($766,354). July represented the month with the highest average total benefit amount cost ($52,084). Strains and sprains, back injuries, and lifting activities all represented the highest total benefit amount cost in terms of nature of injury, body part injured, and cause of injury, respectively. No statistically significant difference was found between the median total benefit costs in terms of gender, employment type, employment sector, or firefighting activity. Understanding the costs associated with workers’ compensation claims can provide insight into injury severity and these results may aid in the development of more informed decisions for resource allocation and effective prevention strategies

Removing Deer Mice from Buildings and the Risk for Human Exposure to Sin Nombre Virus

Trapping and removing deer mice from ranch buildings resulted in an increased number of mice, including Sin Nombre virus antibody–positive mice, entering ranch buildings. Mouse removal without mouse proofing will not reduce and may even increase human exposure to Sin Nombre hantavirus

Population Density and Seasonality Effects on Sin Nombre Virus Transmission in North American Deermice (Peromyscus maniculatus) in Outdoor Enclosures

Surveys of wildlife host-pathogen systems often document clear seasonal variation in transmission; conclusions concerning the relationship between host population density and transmission vary. In the field, effects of seasonality and population density on natural disease cycles are challenging to measure independently, but laboratory experiments may poorly reflect what happens in nature. Outdoor manipulative experiments are an alternative that controls for some variables in a relatively natural environment. Using outdoor enclosures, we tested effects of North American deermouse (Peromyscus maniculatus) population density and season on transmission dynamics of Sin Nombre hantavirus. In early summer, mid-summer, late summer, and fall 2007–2008, predetermined numbers of infected and uninfected adult wild deermice were released into enclosures and trapped weekly or bi-weekly. We documented 18 transmission events and observed significant seasonal effects on transmission, wounding frequency, and host breeding condition. Apparent differences in transmission incidence or wounding frequency between high- and low-density treatments were not statistically significant. However, high host density was associated with a lower proportion of males with scrotal testes. Seasonality may have a stronger influence on disease transmission dynamics than host population density, and density effects cannot be considered independent of seasonality

A longitudinal study of Sin Nombre virus prevalence in rodents, southeastern Arizona.

We determined the prevalence of Sin Nombre virus antibodies in small mammals in southeastern Arizona. Of 1,234 rodents (from 13 species) captured each month from May through December 1995, only mice in the genus Peromyscus were seropositive. Antibody prevalence was 14.3% in 21 white-footed mice (P. leucopus), 13.3% in 98 brush mice (P. boylii), 0.8% in 118 cactus mice (P. eremicus), and 0% in 2 deer mice (P. maniculatus). Most antibody-positive mice were adult male Peromyscus captured close to one another early in the study. Population dynamics of brush mice suggest a correlation between population size and hantavirus-antibody prevalence

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 micrositespecific 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