Rabbit Hemorrhagic Disease

The étiologie agents of rabbit hemorrhagic disease (RHD) are rabbit hemorrhagic disease viruses (RHDVs). These highly contagious viruses are members of the viral family Caliciviridae, genus Lagovinis (Schoch et al. 2020) and negatively affect various lagomorph species, often causing high mortality rates in select taxa. While other lagomorph-associated caliciviruses exist, we focus on RHDV (aJso known ais classical RHDV including subtype RHDVa) and RHDV2 (also know as subtype RHDVb and RHDV serotype 2) within this chapter, with a major emphasis on recent outbreaks of RHDV2 in wildlife in North America. Although the bulk of the research associated with environmental persistence, viral shedding, and transmission has been directed towards classical RHDV, RHDV2 is thought to have similar traits (USDA 2020a). As will be evident in this chapter, the environmental stability of RHDVs can be so long that the epidemiology of these viruses in wild populations can be quite complicated. This disease is a dassic example of the dangers associated with the introduction and establishment of a foreign animal pathogen transmitted from domestic animals into wildlife (Tom Gidlewski, personal observation)

Impact of Age and Sex of Rocky Mountain Elk (\u3ci\u3eCervus elaphus nelson\u3c/i\u3e) on Follicle Counts From Rectal Mucosal Biopsies for Preclinical Detection of Chronic Wasting Disease

To determine if the number of rectal lymphoid follicles decreases with respect to age and sex relative to diagnosis of chronic wasting disease (CWD), rectal biopsies (n = 1,361) were taken from captive Rocky Mountain elk (Cervus elaphus nelsoni) at 4 ranches in the western United States between 2005 and 2008. Rectal tissues were stained with a monoclonal antibody (F99/97.6.1), which selectively stains the abnormal isoform of the prion protein associated with CWD of elk. The number of lymphoid follicles obtained from typical biopsy tissues decreased with the age of the animal. The acceptable number of lymphoid follicles for detection of CWD was not considered to be a problem in elk up to 8.5 years of age, but in elk over 8.5 years of age, the follicle count was considered to be low. Sex of the animal had no effect on the number of lymphoid follicles observed in each age group. Rectal biopsies were an accurate test to diagnose preclinical stages of CWD in elk but may be best suited to elk that are less then 8.5 years of age

Impact of Age and Sex of Rocky Mountain Elk (\u3ci\u3eCervus elaphus nelson\u3c/i\u3e) on Follicle Counts From Rectal Mucosal Biopsies for Preclinical Detection of Chronic Wasting Disease

To determine if the number of rectal lymphoid follicles decreases with respect to age and sex relative to diagnosis of chronic wasting disease (CWD), rectal biopsies (n = 1,361) were taken from captive Rocky Mountain elk (Cervus elaphus nelsoni) at 4 ranches in the western United States between 2005 and 2008. Rectal tissues were stained with a monoclonal antibody (F99/97.6.1), which selectively stains the abnormal isoform of the prion protein associated with CWD of elk. The number of lymphoid follicles obtained from typical biopsy tissues decreased with the age of the animal. The acceptable number of lymphoid follicles for detection of CWD was not considered to be a problem in elk up to 8.5 years of age, but in elk over 8.5 years of age, the follicle count was considered to be low. Sex of the animal had no effect on the number of lymphoid follicles observed in each age group. Rectal biopsies were an accurate test to diagnose preclinical stages of CWD in elk but may be best suited to elk that are less then 8.5 years of age

Detection of prion protein in the cerebrospinal fluid of elk (\u3ci\u3eCervus canadensis nelsoni\u3c/i\u3e) with chronic wasting disease using protein misfolding cyclic amplification

Cerebrospinal fluid (CSF) has been examined as a possible source for preclinical diagnosis of prion diseases in hamsters and sheep. The present report describes the detection of chronic wasting disease (CWD) in the CSF of elk and evaluates its usefulness as an antemortem test for CWD. The CSF from 6 captive and 31 free-ranging adult elk was collected at necropsy and evaluated for the presence of the abnormal isoform of the prion protein that has been associated with CWD (PrPCWD) via protein misfolding cyclic amplification. Additionally, the obex from each animal was examined by immunohistochemistry (IHC). Four out of 6 captive animals were CWD-positive and euthanized due to signs of terminal CWD. The remaining 2 were CWD negative. None of the 31 free-range animals showed overt signs of CWD, but 12 out of 31 tested positive for CWD by IHC. Protein misfolding cyclic amplification detected PrPCWD from 3 of the 4 captive animals showing clinical signs of CWD and none of the nonclinical animals that were CWD positive by IHC. The data suggests that CWD prions can be detected in the CSF of elk, but only relatively late in the course of the disease

Vertebrate Host Susceptibility to Heartland Virus

Heartland virus (HRTV) is a recently described phlebovirus initially isolated in 2009 from 2 humans who had leukopenia and thrombocytopenia. Serologic assessment of domestic and wild animal populations near the residence of 1 of these persons showed high exposure rates to raccoons, white-tailed deer, and horses. To our knowledge, no laboratory-based assessments of viremic potential of animals infected with HRTV have been performed. We experimentally inoculated several vertebrates (raccoons, goats, chickens, rabbits, hamsters, C57BL/6 mice, and interferon-α/β/γ receptor–deficient [Ag129]) mice with this virus. All animals showed immune responses against HRTV after primary or secondary exposure. However, neutralizing antibody responses were limited. Only Ag129 mice showed detectable viremia and associated illness and death, which were dose dependent. Ag129 mice also showed development of mean peak viral antibody titers \u3e8 log10 PFU/mL, hemorrhagic hepatic lesions, splenomegaly, and large amounts of HRTV antigen in mononuclear cells and hematopoietic cells in the spleen

Disease Progression and Serological Assay Performance in Heritage Breed Pigs following Brucella suis Experimental Challenge as a Model for Naturally Infected Feral Swine

Invasive feral swine (Sus scrofa) are one of the most important wildlife species for disease surveillance in the United States, serving as a reservoir for various diseases of concern for the health of humans and domestic animals. Brucella suis, the causative agent of swine brucellosis, is one such pathogen carried and transmitted by feral swine. Serology assays are the preferred field diagnostic for B. suis infection, as whole blood can be readily collected and antibodies are highly stable. However, serological assays frequently have lower sensitivity and specificity, and few studies have validated serological assays for B. suis in feral swine. We conducted an experimental infection of Ossabaw Island Hogs (a breed re-domesticated from feral animals) as a disease-free proxy for feral swine to (1) improve understanding of bacterial dissemination and antibody response following B. suis infection and (2) evaluate potential changes in the performance of serological diagnostic assays over the course of infection. Animals were inoculated with B. suis and serially euthanized across a 16-week period, with samples collected at the time of euthanasia. The 8% card agglutination test performed best, whereas the fluorescence polarization assay demonstrated no capacity to differentiate true positive from true negative animals. Froma disease surveillance perspective, using the 8%card agglutination test in parallel with either the buffered acidified plate antigen test or the Brucella abortus/suis complement fixation test provided the best performance with the highest probability of a positive assay result. Application of these combinations of diagnostic assays for B. suis surveillance among feral swine would improve understanding of spillover risks at the national level

The Role of the National Wildlife Disease Program in Wildlife Disease Surveillance and Emergency Response

The National Wildlife Disease Program (NWDP), overseen by the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services (WS), was established in 2003 to develop a nationally coordinated wildlife disease surveillance and emergency response system. Since its inception, the NWDP has developed collaborations with over 200 national and international partners. The national partners include state, tribal, federal, and private organizations. These partnerships have resulted in surveillance and management of over 100 pathogens, toxins, and disease syndromes affecting wildlife, domestic animals, and humans. Several of these pathogens, including avian influenza, plague, tularemia, bluetongue, and 10 pathogens carried by feral swine, are monitored on a national or regional scale. The NWDP maintains an archive of select wildlife disease samples. Archived samples are available to scientists at universities and other entities with approved research protocols. The NWDP also serves as Wildlife Services’ primary emergency response unit. The program’s wildlife disease biologists are trained as all-hazard first responders, and the national office coordinates training and mobilization of these and other personnel. Internationally, the NWDP has worked with over 30 countries, developing close relationships with many organizations. This paper provides an overview of the NWDP structure and its activities. Programmatic efforts to address highly pathogenic avian influenza (HPAI) H5N1 are presented as an example of a coordinated national response when a disease risk posed by wildlife presents a potential threat to agriculture or humans

Pathogenesis And Epidemiology Of Brucellosis In Yellowstone Bison: Serologic And Culture Results From Adult Females And Their Progeny

Our objective in this prospective study was to determine the natural course of Brucella abortus infection in cohorts of seropositive and seronegative, female bison (Bison bison) and their offspring in Yellowstone National Park (YNP) for 5 yr. We collected specimens from 53 adult females and 25 calves at least once and from 45 adults and 22 calves more than once. Annual seroconversion rates (negative to positive) were relatively high (23% for calves and juvenile bison, 6% in the total sample of adult female bison in our study, and 11% in the adult females that began the study as seronegatives). Antibody was not protective against infection, even for calves that passively received antibody from an infected mother’s colostrum. Antibody levels stayed remarkably constant, with only a slow decline over time. We found only two seroconversions from a weak positive status to negative. Infected bison aborted and shed viable bacteria. Risk of shedding infective Brucella was highest for bison in the 2 yr following seroconversion from negative to positive. In one bison, we detected shedding for 3 yr following seroconversion. Regardless of serostatus of dams and neonates, most calves were seronegative by 5 mo of age. There was no relationship between the antibody status of the dam and the tendency of a calf to seroconvert to positive during the duration of the study

Vertebrate Host Susceptibility to Heartland Virus

Heartland virus (HRTV) is a recently described phlebovirus initially isolated in 2009 from 2 humans who had leukopenia and thrombocytopenia. Serologic assessment of domestic and wild animal populations near the residence of 1 of these persons showed high exposure rates to raccoons, white-tailed deer, and horses. To our knowledge, no laboratory-based assessments of viremic potential of animals infected with HRTV have been performed. We experimentally inoculated several vertebrates (raccoons, goats, chickens, rabbits, hamsters, C57BL/6 mice, and interferon-α/β/γ receptor–deficient [Ag129]) mice with this virus. All animals showed immune responses against HRTV after primary or secondary exposure. However, neutralizing antibody responses were limited. Only Ag129 mice showed detectable viremia and associated illness and death, which were dose dependent. Ag129 mice also showed development of mean peak viral antibody titers >8 log10 PFU/mL, hemorrhagic hepatic lesions, splenomegaly, and large amounts of HRTV antigen in mononuclear cells and hematopoietic cells in the spleen

Vertebrate Host Susceptibility to Heartland Virus

Heartland virus (HRTV) is a recently described phlebovirus initially isolated in 2009 from 2 humans who had leukopenia and thrombocytopenia. Serologic assessment of domestic and wild animal populations near the residence of 1 of these persons showed high exposure rates to raccoons, white-tailed deer, and horses. To our knowledge, no laboratory-based assessments of viremic potential of animals infected with HRTV have been performed. We experimentally inoculated several vertebrates (raccoons, goats, chickens, rabbits, hamsters, C57BL/6 mice, and interferon-α/β/γ receptor–deficient [Ag129]) mice with this virus. All animals showed immune responses against HRTV after primary or secondary exposure. However, neutralizing antibody responses were limited. Only Ag129 mice showed detectable viremia and associated illness and death, which were dose dependent. Ag129 mice also showed development of mean peak viral antibody titers >8 log10 PFU/mL, hemorrhagic hepatic lesions, splenomegaly, and large amounts of HRTV antigen in mononuclear cells and hematopoietic cells in the spleen