Copepod survival in water bowls exposed to typical Chadian ambient temperatures

Zavier Eure, a junior from North Carolina A&T, worked with the lab of Dr. Michael Yabsley to study copepod survival in different types of water bowls.

Abstract:  Guinea Worm Disease (GWD), caused by the nematode Dracunculus medinensis, has been detected with increasing incidence among dogs in Chad, Africa. Cyclopoid copepods (freshwater crustaceans) are intermediate hosts for D. medinensis. Currently the route(s) of D. medinensis transmission to dogs is still unknown but drinking from unprotected water sources would pose a risk. Dogs have access to water dishes provided for domestic animals and depending on the source of water, these dishes could harbor infected copepods, thereby acting as a source of transmission. To determine how long copepods survive in water dishes when exposed to Chadian ambient temperatures (41.1ᵒC), copepods were placed in three different container types (plastic, glass, and metal) and heated to 40ᵒC. Our results indicate that under simulated Chadian temperatures, metal dishes result in the highest rate of copepods death in the shortest period of time (2hrs) and were the only container to reach 100% copepod mortality. Conversely, plastic dishes exhibited the lowest mortality of copepods. These results indicate that the type of dish used when supplying water for animals in Chad is an important consideration in terms of preventing or interrupting transmission of D. medinensis among dogs.



Download (PDF, 1.38MB)

Resource shifts and infectious disease dynamics in urbanized bird popualtions

Katie Adkins, a student from Clemson University, participated in an ongoing study of infectious disease dynamics in urban bird populations, supervised by Drs. Sonia Hernandez and Michael Yabsley.

Many wildlife species benefit from novel resources – especially supplemental food – offered in human-altered habitats. Shifts in wildlife ecology in response to intentional or accidental feeding can dramatically alter infectious disease dynamics. If hosts aggregate near resources and interact with novel species, provisioning can increase contact rates and exposure to pathogens. Concentrated resources could also improve host immune defenses, and dietary changes might alter the host’s microbiome, with downstream effects on pathogen invasion. Depending on the strengths of these relationships, provisioning could cause some pathogens and parasites to increase and others to decline. The goal of the overarching project is to examine how host use of anthropogenic resources influences pathogen and parasite dynamics across organizational scales. Specifically, our research explores interactions between an enteric pathogen, Salmonella, and the American White Ibis in South Florida, a recently urbanized species, to understand how resource shifts in urban habitats alter host ecology and pathogen dynamics.


Natural history and genetic diversity of Dracunculus spp.

Alec Thompson, a Microbiology major from the University of Oklahoma, worked in the lab of Dr. Michael Yablsey to increase understanding of the genetic diversity of a parasite.

Abstract: Dracunculus spp. are spiruroid nematode parasites that live in the subcutaneous tissues or abdominal cavity of mammals. The most important species is D. medinensis, the human Guinea Worm. In 1985, over 3.5 million people were infected, but due to control efforts by the Carter Center and public health agencies, there were only 22 cases in 2015. Control was primarily through the use of water filters. A related species, D. insignis, is found in various wildlife species, and rarely dogs and cats, in North America. We have been conducting studies on D. insignis as a model parasite to better understand the ecology of D. medinensis. In this study, various potential vertebrate hosts were examined to determine the host-parasite interactions and genetic diversity of Dracunculus parasites within the United States. Analysis of the preliminary results suggests that the raccoon (Procyon lotor) is the preferential host for the parasite but opossums (Didelphis virginiana) are often frequently infected. Molecular characterization was attempted to investigate the intraspecific variation between hosts and regions and also to definitively identify adult female worms which cannot be identified using morphologic characteristics. However, the PCR was problematic as low specificity was observed with the PCR primers we used. Most sequencing attempts were either host DNA or mixed products.  We did get amplicons from four worms that were parasite DNA and they were all D. insignis. Methods for better specificity and amplification and other gene targets of are currently being researched and results are pending. Finally, we conducted experimental infection trials to investigate the potential role of amphibians and fish as hosts. Several species of amphibians were exposed to copepods infected with D. insignis. Infections of 2 species of tadpoles (gray tree frog and northern cricket frog) were confirmed by necropsy. These parasites were fed to ferrets and results will take 6-8 months. Bufo tadpoles did not consume copepods. Previous studies suggested that fish did not become infected with larvae, but we investigated the possible role as a transport host. Three species of fish (tilapia, fathead minnows, and gambusia) were exposed to infected copepods and then immediately fed to ferrets. Ferrets will be tested after 6-8 months. Although results of several studies are pending, this study has provided new data on the natural history of D. insignis and intiated additional studies that may help understand the continued transmission of D. medinensis by the use of alternative hosts.

Download (PDF, 751KB)

Identifying Avian Haemosporidians in Turkey Vultures and Black Vultures from South Carolina

Alexandra Wickson, a student at the University of Georgia, worked with Dr. Michael Yabsley and others in his lab to determine parasite prevalence in vulture populations.

Abstract: Avian haemosporidian blood parasites are widespread among many families of birds and, in some species, can cause avian malaria.  In previous studies on blood parasites of vultures, prevalence and diversity of parasites were low. However, the long-term effects of infection on the birds were unknown. Overall, Turkey Vultures (Cathartes aura) have had a higher prevalence and diversity of blood parasites (i.e., Haemoproteus, Plasmodium, and Leucocytozoon spp.) compared with Black Vultures (Coragyps atratus) with only a single Plasmodium sp. infection has been reported in one Black Vulture from Florida. Based on morphological data, Haemoproteus catharti was described from the Turkey Vulture. The primary goal of this study was to better characterize H. catharti with morphologic and molecular data and to investigate ecological or intrinsic factors associated with infection. Turkey Vultures and Black Vultures were sampled at the Savannah River Site in Aiken, SC. Blood smears were immediately prepared, fixed with methanol, and stained with modified Giemsa. Parasite prevalence and parasitemia were determined by examination of at least 20,000 erythrocytes. We also conducted nested polymerase chain reaction (PCR) targeting the cytochrome b gene. We detected a high prevalence of parasites in Turkey Vultures (43%) and a complete absence of parasites in Black Vultures. No difference in prevalence or parasitemia levels were noted between sites, sexes, or age class. Phylogenetically, this parasite was most similar to a parasite reported from wood storks (Mycteria americana) from Florida. Together, these two sequences were distinct from the genera Haemoproteus and Plasmodium, and likely represent a new genus of avian blood parasite. This study documents the first genetic characterization of malarial parasites of vultures. Further genetic work targeting multiple genes is needed to confirm the phylogenetic relationship of this parasite to other avian haemosporidians.

Download (PDF, 581KB)


Baylisascaris procyonis prevalence and dynamics in a rodent population in Georgia

Ian Buchta, from Tulane University, worked with Dr. Michael Yabsley and members of his lab to study parasites in a local racoon population.

Ian Buchta1,2, Amanda Holley1, Kayla Buck1,3, Sarah Sapp1,4, Michael Yabsley1,3

Baylisascaris procyonis, the common roundworm parasite of raccoons, is a well-recognized zoonotic parasite. It utilizes small vertebrates as intermediate hosts and undergoes migration through the central nervous system which can lead to behavioral modifications or death. Previous studies on rodents have been conducted in Indiana where the prevalence of B. procyonis in raccoons is very high and only focused on a single species, the white-footed mouse (Peromyscus leucopus). In Georgia, the prevalence is low in raccoons, possibly due to its recent emergence. Our study was conducted to determine if rodents in Georgia are infected and investigate if other rodents are involved in the life cycle. Additionally, we tested if habitat disturbance impacted prevalence. Rodents were trapped at five sites with variable disturbance. After human euthanasia, brains were removed, pressed between glass slides, and microscopically analyzed for larvae. The remaining tissues, other than the skin, were digested in a 0.3% pepsin and 1% hydrochloric acid and the resulting liquid was analyzed for larvae. Infections were noted at two sites in Jackson and Clarke counties. Of 71 P. leucopus tested, seven (10%) were infected, although only one had larvae in the brain. None of the cotton rats (n=10), cotton mice (n=3), brown rats (n=4), or chipmunks (n=2) were infected. No difference in prevalence was noted for P. leucopus from sites with low or high levels of disturbance. Our finding of B. procyonis in P. leucopus is the first to document the parasite in a non-raccoon host in Georgia and of the parasite in Jackson Co., Georgia. Because this parasite causes disease in numerous avian and mammalian hosts, wildlife with neurologic disease should be considered suspects for B. procyonis infection



  1. Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine,  Athens, GA 30602
  2. Tulane University, New Orleans, LA 70118
  3.  Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602
  4. Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602

Download (PDF, 1.06MB)