Rick Gerhold

Rick Gerhold
University of Tennessee | UTK · Biomedical and Diagnostic Sciences

DVM, MS, PhD, Diplomat ACVM (Parasitoloy)

About

237
Publications
67,351
Reads
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1,382
Citations
Introduction
I am a veterinary parasitologist and I perform classical and molecular diagnostics and research on parasites. My main area of focus is wildlife parasitology. Current projects include: meningeal worm and filarid epidemiology in cervids, avian parasitology, Trichomonas gallinae epidemiology and ecology, and ecology of Toxoplasma gondii.
Additional affiliations
January 2013 - present
University of Tennessee
Position
  • Research Assistant
Description
  • Perform classical and molecular identification of parasites obtained from domestic and wild animals. In addition, I instructed first and fourth year veterinary students in veterinary parasitology
August 2012 - December 2012
Universtity of Tennessee
Position
  • Research Assistant
Description
  • Established own research projects and funding including ecology of Toxoplasma gondii transmission in wild animals in the southeastern US and investigation of filarid nematode-associated moose morbidity and mortality.
January 2011 - August 2012
University of Tennessee
Position
  • PostDoc Position
Description
  • Supervising and conducting mammal and reptile trapping, ectoparasite sampling, and tick identification associated with a National Science Foundation funded Lyme disease ecology investigation.
Education
January 2008 - December 2010
University of Georgia
Field of study
  • Wildlife Diseases - parasitology
January 2002 - December 2007
University of Georgia
Field of study
  • Wildlife Diseases - parasitology
August 1997 - May 2001
Purdue University
Field of study
  • Veterinary Medicine

Publications

Publications (237)
Article
Full-text available
We report cross-reactive antibodies from prepandemic cats and postpandemic South Carolina white-tailed deer that are specific for that SARS-CoV RBD. There are several potential explanations for this cross-reactivity, each with important implications to coronavirus disease surveillance.
Preprint
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In late 2019, a novel coronavirus began circulating within humans in central China. It was designated SARS-CoV-2 because of its genetic similarities to the 2003 SARS coronavirus (SARS-CoV). Now that SARS-CoV-2 has spread worldwide, there is a risk of it establishing new animal reservoirs and recombination with native circulating coronaviruses. To s...
Article
Full-text available
Toxoplasma gondii is a parasite of significant public health importance. We attempted to detect T. gondii contamination and assess advantages and disadvantages of contamination indicators through surveilling soil, wildlife, cats, and agricultural animals on a dairy farm in eastern Tennessee, U.S in 2016 and 2017. Twenty-two soil samples were collec...
Article
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Between March 2019 and February 2020, Asian long-horned ticks (Haemaphysalis longicornis Neumann, 1901) were discovered and collected for the first time in one middle and seven eastern Tennessee counties, facilitated by a newly developed passive and collaborative tick-surveillance network. Network collaborators included federal, state, county, univ...
Chapter
This chapter presents the details about clinical history, causative agent, clinical signs and lesions, transmission route, diagnostic tests, differential diagnosis, and prevention and control of parasitic diseases that include coccidiosis, histomonosis, cryptosporidiosis, trichomonosis, crop capillariasis, oxyspiruriasis, and toxoplasmosis. Clinica...
Article
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Bushmeat hunting and consumption, although widely utilized as necessary supplement to household income and nutrition in many regions, presents threats to public health and wildlife conservation efforts. In northern Uganda, consumption of bats and primates, two wildlife groups often implicated in zoonotic disease emergence, is not widely culturally...
Article
Full-text available
Toxoplasma gondii is an important zoonotic protozoan parasite that can infect all warm-blooded animals including mammals and birds. Raptors can be intermediate hosts for T. gondii and the infection may be dependent on their feeding habits. In this study, we investigated the seroprevalence of T. gondii in ten raptor species from Florida, Pennsylvani...
Article
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Old World Camelids (OWC) represent two species (Camelus bactrianus and Camelus dromedarius) with increasing numbers in North America. Gastrointestinal (GI) parasitism is a major cause of clinical disease in camelids and leads to significant economic impacts. Literature reporting on clinical parasitism of camels is localized to India, Africa, and th...
Article
Full-text available
Lyme disease is common in the northeastern United States, but rare in the southeast, even though the tick vector is found in both regions. Infection prevalence of Lyme spirochetes in host-seeking ticks, an important component to the risk of Lyme disease, is also high in the northeast and northern midwest, but declines sharply in the south. As ticks...
Article
Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii , is an important food borne zoonosis affecting a wide range of hosts, including birds. This study investigated the seroconversion, feed conversion rate, weight gain, and parasite tissue tropism as a function of parasite dose and virulence in turkeys. Twenty five four-week old female...
Article
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Since 2002, reports of deer with swollen muzzles from throughout the United States have resulted in significant interest by wildlife biologists and wildlife enthusiasts. The condition was identified in 25 white-tailed deer (Odocoileus virginianus) and 2 mule deer (O. hemionus). Microscopic lesions consisted of severe, granulomatous or pyogranulomat...
Article
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Background: Few reports of Echinococcus spp. have been described in the USA; however, the geographical distribution of Echinococcus spp. in wild hosts is increasing consequent to human activities. In the early 2000's, 253 elk (Cervus canadensis) originating from Alberta, Canada were released into the Great Smoky Mountains National Park and North C...
Article
A 2-y-old Brahman bull was presented with progressive hindlimb ataxia and paraparesis that led to recumbency. Postmortem examination revealed scattered pinpoint, red-brown foci within the brainstem and gray matter of the spinal cord, and a larger lesion within the spinal cord at the level of T13. Histology of the section of T13 contained cross-sect...
Article
We screened raptors (n=186), vultures (n=2), and columbids (n=2) presenting to a Tampa, Florida, USA rehabilitation center from June 2016 to April 2017 for Trichomonas gallinae. One juvenile Cooper's Hawk (Accipiter cooperii) was culture- and PCR-positive and sequencing identified as Genotype E1. A subset of culture-negative (10%, n=19) samples wer...
Article
There are limited reports of the genetic characterization of Toxoplasma gondii infecting captive macropods in North America. A novel genotype, ToxoDB PCR-RFLP genotype 263, was reported from six wallabies at a zoological facility in Virginia, USA, prompting an investigation into the genotypes from T. gondii strains infecting macropods at a zoologic...
Article
Full-text available
Black bears (Ursus americanus) are commonly exposed to Toxoplasma gondii. However, there are no reports of exposure or infection with T. gondii in black bears from Oklahoma. The purpose of our project was to determine the seroprevalence of T. gondii antibodies in black bears collected in Oklahoma. Additionally, since only serum was available from t...
Article
The modified agglutination test was used to study Toxoplasma gondii exposure in 70 eastern Tennessee, US, black bears ( Ursus americanus) from 2015 to 2017. Overall, 74% (52/70) of bears were seropositive, and T. gondii was more prevalent in adults than subadults.
Article
We molecularly examined brains from 186 hunter-killed Mourning Doves (Zenaida macroura) and 11 Rock Pigeons (Columba livia) from eastern Tennessee for Toxoplasma gondii. Two doves (1%) were PCR- and sequence-positive, whereas all pigeons were PCR-negative.
Article
Full-text available
In Europe, Trichomonas gallinae recently emerged as a cause of epidemic disease in songbirds. A highly virulent and clonal strain of the parasite, first found in the UK, has become the predominant strain there and spread to continental Europe. Discriminating this epidemic strain of T. gallinae from other strains necessitated development of multi-lo...
Article
Trichomonas gallinae is a protozoan pathogen that causes avian trichomonosis typically associated with columbids (canker) and birds of prey (frounce) that predate on them, and has recently emerged as an important cause of passerine disease. An archived panel of DNA from North American (USA) birds used initially to establish the ITS ribotypes was re...
Article
Full-text available
Water containing organic material has been shown to increase the persistence of the avian pathogenic protozoa, Trichomonas gallinae. We hypothesized that the decrease in dissolved oxygen due to microbes in the organic material could increase persistence of the microaerophilic trichomonads. Using simulated birdbaths, we determined 1) the levels of d...
Article
Nine of 23 (39%) research ewes with severe diarrhea and weight loss had histologic lesions consistent with Eimeria gilruthi infection in their abomasa. Gross anatomic lesions included hundreds of opaque 1-mm nodules in abomasal mucosa that corresponded microscopically to 200-300 µm diameter organisms surrounded by areas of necrosis. Analysis of fec...
Article
Full-text available
Background: Moose (Alces alces) are a culturally and economically valued species in Minnesota. However, the moose population has experienced a sudden, marked decline in their range, including extirpation in the northwest and a 66% decline in the last decade in the northeast portions of the state. Although the exact cause of this decline is unclear...
Article
Full-text available
A majority of emerging infectious diseases in humans are zoonoses. Understanding factors that influence the emergence and transmission of zoonoses is pivotal for their prevention and control. Toxoplasma gondii is one of the most widespread zoonotic pathogens known today. Whereas only a few genotypes of T. gondii dominate in the Northern Hemisphere,...
Article
We analyzed 69 eastern Tennessee wildlife samples for Baylisascaris spp. during 2011. The prevalence of Baylisascaris spp. in raccoons ( Procyon lotor) was 16% (8/49), an increase compared to previous surveys in this region. One Virginia opossum ( Didelphis virginiana) had eggs in its feces, indicating that opossums can play a role in Baylisascaris...
Article
Avian trichomonosis, caused by the protozoan Trichomonas gallinae, affects bird-eating raptors worldwide. Raptors can develop trichomonosis by feeding on infected prey, particularly Rock Pigeons (C olumba livia), which are a reservoir for T. gallinae. Raptors may be particularly vulnerable to T. gallinae infection in degraded habitats, where change...
Article
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To better understand the clinical pathology, diseases, and causes of mortality of reintroduced American martens ( Martes americana) in Michigan, a study was conducted from 2011 to 2015 in the Upper and Lower Peninsulas of Michigan. Samples obtained from live trapping ( n = 58) or harvested carcasses ( n = 34) were serologically tested for select pa...
Article
Toxoplasma gondii counts among the most consequential food-borne parasites, and although the parasite occurs in a wide range of wild and domesticated animals, farms may constitute a specific and important locus of transmission. If so, parasites in animals that inhabit agricultural habitats might be suspected of harboring genetically distinct parasi...
Article
During an outbreak of Wellfleet Bay virus (WFBV) in common eiders ( Somateria mollissima) from the Cape Cod region of Massachusetts, several birds were diagnosed with trichomonosis consisting of multiple trichomonad species. Six birds were examined, with trichomonads found in ceca in four birds and associated typhlitis in three of these four birds....
Article
Toxoplasma gondii is a feline protozoan reported to cause morbidity and mortality in manatees and other marine mammals. Given the herbivorous nature of manatees, ingestion of oocysts from contaminated water or seagrass is presumed to be their primary mode of infection. The objectives of this study were to investigate oocyst contamination of seagras...
Article
Full-text available
Background Toxoplasma gondii is a widespread protozoan parasite that infects humans and other animals. Previous studies indicate some genotypes of T. gondii are more frequently isolated in wildlife than agricultural animals, suggesting a wild/feral animal diversity model. To determine seroprevalence and genetic diversity of T. gondii in southeaster...
Article
This manuscript describes an outbreak of fatal toxoplasmosis in wallabies. Ten adult red necked wallabies (Macropus rufogriseus) were imported from New Zealand to the Virginia Zoo. Agglutination testing upon admission into quarantine showed all animals to be negative for antibodies to Toxoplasma gondii. Nine of these wallabies died from acute toxop...
Article
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There are reports of horses with acute onset acquired cervical scoliosis and cutaneous analgesia. The underlying dorsal gray column myelitis that produces these neurologic signs has been only presumptively attributed to migration of Parelaphostrongylus tenuis within the spinal cord. Despite previous confirmation brain by polymerase chain reaction t...
Article
Full-text available
We diagnosed renal coccidiosis in two of five Great-horned Owls ( Bubo virginianus ) examined in eastern Tennessee, 2007-2013. Histopathologic examination of the kidneys revealed multifocal mild-to-moderate dilation and epithelial hyperplasia of collecting ducts. Renal collecting duct epithelial cells contained intracytoplasmic microgametocytes, ma...
Data
Fig S1. Aerial view of the filly with cervical scoliosis.
Data
Fig S2. Cervical scoliosis with right‐sided convexity.
Article
Full-text available
There are concerns regarding population declines of northern bobwhite (Colinus virginianus) over the past 4 decades (Palmer et al. 2011). Infectious and noninfectious diseases are among the limiting factors that potentially influence bobwhite demographics (Applegate 2014). The last update of diseases of bobwhite was presented at the Second National...
Article
Field isolates of coccidia from 20 natural outbreaks in the chukar partridge (Alectoris chukar) were received from gamebird farms in 10 U.S. states. These were propagated in the laboratory and identified by microscopy and PCR. Of 20 samples, 18 were Eimeria kofoidi, two were Eimeria legionensis only, and one was a mixture of the two species. One is...
Article
Full-text available
Marine mammals are important indicators for ecosystem health and serve as sentinel species for infectious agents including zoonoses. Histological examination of tissues from a stranded Florida manatee Trichechus manatus latirostris revealed protozoal cysts in the cerebrum and intrahistiocytic tachyzoites in the liver and caudal mesenteric lymph nod...
Article
An adult nematode was grossly identified in the meninges of a Malayan sambar (Rusa unicolor equina), with numerous microfilariae associated with encephalitis and vasculitis on histopathology. The nematode was confirmed to be Elaeophora schneideri by sequencing a portion of the 18S rRNA gene. Our report highlights the potential for aberrant migratio...
Article
Full-text available
Background Moose (Alces alces) are a culturally and economically valued species in Minnesota, where the northeast population has decreased by 60 % since 2006. The cause of the decline is currently unclear; however, parasites, predation, and climate change have all been implicated. Nematode parasites are important pathogens in North American moose,...
Article
Full-text available
The American marten (Martes americana) was reintroduced to both the Upper (UP) and northern Lower Peninsula (NLP) of Michigan during the 20th century. This is the first report of endoparasites of American marten from the NLP. Faeces from live-trapped American marten were examined for the presence of parasitic ova, and blood samples were obtained fo...
Article
Full-text available
The privatization of captive cervids, with associated interstate movement of cervids, poses a substantial health risk to native free-ranging wildlife and domestic animals in North America. Captive cervid operations provide an avenue for transmission of diseases such as chronic wasting disease that could have significant impact on wild cervid popula...
Article
Full-text available
Trichomonas gallinae, a well-documented protozoan parasite of avian hosts, has been implicated in major passerine mortality events recently and historically throughout the literature. It has been suggested that bird baths and artificial water sources could serve as a source of infection for naive birds; however, trichomonad persistence in water is...
Article
Full-text available
Northern Bobwhites (Colinus virginianus) have been in decline throughout the southeastern US. Prevalence of Trichomonas gallinae in wild bobwhites is unknown, although T. gallinae caused morbidity and mortality in experimentally infected bobwhites. Many species of Columbidae (pigeons and doves) in Texas are hosts to T. gallinae. Bobwhites potential...
Article
Full-text available
Trichomonas gallinae is a protozoan parasite commonly found in columbids, passerines, and several raptor species. Although T. gallinae is thought to spread between individuals and across species through shared water sources, little research has been conducted regarding the persistence of T. gallinae in the environment. To determine the persistence...
Article
Trypanosoma cruzi is a zoonotic parasite of humans and other mammalian hosts with distribution throughout the Americas. Domestic and wild canine species are reservoirs for human T. cruzi infections. The present study examined the prevalence of antibodies to T. cruzi in wild canids from the United States. Sera from 13 red foxes (Vulpes vulpes) and 2...
Chapter
Clinical parasitic disease in backyard poultry in general is less of an issue compared to commercially raised poultry due to the lower density of birds. When parasite-associated morbidity and mortality occurs in backyard poultry it is often a result of poor husbandry and nutrition, overcrowding, mixing of avian species, or mixing of multiple age gr...
Article
Full-text available
Formalin-fixed, paraffin-embedded tissues from elk (Cervus elaphus), goats, and camelids with case histories and lesions suggestive of Parelaphostrongylus tenuis were examined by histology to characterize lesions that could aid in definitively diagnosing P. tenuis infection. Additionally, sections of paraffin-embedded tissue were used in a nested p...
Article
Full-text available
Abstract We examined 31 free-ranging coyotes (Canis latrans) from central Georgia, USA, for select parasites and viral agents. Sixteen coyotes had adult heartworms (Dirofilaria immitis). Serum samples from 27 animals revealed antibodies against canine parvovirus (100%), canine distemper virus (48%), canine adenovirus (37%), and Trypanosoma cruzi (7...
Article
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Abstract A new method to amplify coccidia DNA by polymerase chain reaction (PCR) was developed by placing freeze-thawed oocysts in Ready-to-Go PCR bead tubes and using a 5-min initial heat denaturation step. Positive PCR reactions were found in 3/3 samples containing 20 or 50 oocysts; when < 5 oocysts were used, 1/3 was positive. This technique sho...
Article
Full-text available
Trichomonas gallinae is a ubiquitous flagellated protozoan parasite, and the most common etiologic agent of epidemic trichomonosis in columbid and passerine species. In this study, free-ranging Pacific Coast band-tailed pigeons (Patagioenas fasciata monilis) in California (USA) were found to be infected with trichomonad protozoa that were genetical...
Article
Full-text available
Visceral leishmaniasis (VL) is a zoonosis with worldwide distribution. Infections with the Leishmania donovani complex, including Leishmania infantum, cause the VL. Domestic dogs are the most important reservoir host for human VL, and wild canids are also susceptible. In the United States, infections with L. infantum are common in the foxhound dog...
Article
Full-text available
Trichomonas gallinae is a protozoan parasite commonly found in columbids, passerines, and raptors. In passerines and columbids, trichomonosis causes significant morbidity and mortality associated with contaminated bird feeders and waters. However, there has been little work on the persistence of T. gallinae in water to determine if artificial water...