Vive la resistance: the impact of antibiotic use in US livestock on emerging antibiotic resistance

Sydney Rentsch, a junior from Connecticut College, worked with Dr. JP Schmidt to examine the relationship between antibiotic use and resistance in US livestock.

Abstract:  The potential for livestock to spread antibiotic resistant pathogens to human populations is a cause for concern. This research focused on finding trends in data on US livestock antibiotic resistance, US livestock inventory and US livestock antibiotic consumption. Data was compiled from CDC, USDA and FDA reports and publicly available datasets. Data was analyzed in R and generalized additive models (GAMs) were used to test for increasing resistance as a function of time. We found that the tetracycline class of antibiotics had consistently high resistance over time. The antibiotic class lincosamides, had a sharp increase in resistance which was positively associated with the data from turkeys and chickens. Analyzes also found that poultry had the highest burden of antibiotic resistant pathogens. These results may lead future studies focused on antibiotic resistance in poultry and provide framework for future data analysis.


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Testing the Enemy Release Hypothesis in Ungulates (Artiodactyl and Perissodactyl) and Carnivores

Lauren Kleine, a student from Colorado State University, examined the enemy release hypothesis in a project directed by Dr. Patrick Stephens and Dr. J.P. Schmidt.

Abstract:  The Enemy Release Hypothesis (ERH) predicts that invasive species will achieve greater success in non-native ranges due in part to escape from parasites found in their native ranges. The purpose of our study was to determine whether members of mammal populations occurring outside their native ranges are generally infected by fewer parasites than those from populations of the same species within their native ranges. We used the Global Mammal Parasite Database version 2.0 to investigate 39 species with entries from both inside and outside of their native ranges. For each species, Parasite Species Richness (PSR) was calculated for each species in native and non-native ranges, as well as measures of sampling effort. We used a Generalized Additive Model (GAM) of PSR as a function of sampling effort to generate residual values of PSR. Residual values were then used to test for differences in PSR in native vs. invasive ranges. In final analyses restricted to well-studied hosts, we found a significant reduction in PSR in invasive ranges. This study highlights the importance of considering sampling effort measures when comparing species richness values, and lends support to the enemy release hypothesis.

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Using a large spatial database to explore relationships between fungal pathogens and their insect hosts

Chevana Dorris, a Biology major from Jackson State University, and Dr. J.P. Schmidt looked at relationships between fungal pathogens and their insect hosts.

Abstract: The USDA-ARS Collection of Entomopathogenic Fungal Cultures (ARSEF) database features nearly 8,000 fungal pathogen-insect host entries. For each fungal entomopathogen and its insect host, the database lists taxonomy and geographic location. Relying on the data from ARSEF, our project explores biases and patterns in relationships between fungal pathogens and their insect hosts. After removing entries in which hosts or pathogens were not resolved to species, we summarized the data on unique host-pathogen pairs by fungal class and insect host order. We ran analyses to create visualizations of the cleaned data. We summarized the number of fungal pathogens per host, the number of hosts per fungal pathogen, and the latitudinal range of pathogens. From these visualizations, we identified a set of biases and patterns in the data. Fungal species that have been investigated for use as biocontrol agents dominated the database and infected many hosts, especially species within the insect classes Coleoptera, Hemiptera, and Lepidopotera which include many economically damaging pests. We also found that the database has more fungal pathogens from the more-studied temperate zones as opposed to the tropics where fungi are actually more abundant and fungal richness is greater. Despite clear taxonomic and geographic biases, this large database has potential for exploring patterns in generalism and specialism among well-studied pathogen species.

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