Fatal Degenerative Neurologic Illnesses in Men Who Participated in Wild Game Feasts --- Wisconsin, 2002
Creutzfeldt-Jakob disease (CJD) is a fatal neurologic disorder in humans. CJD is one of a group of conditions known as transmissible spongiform encephalopathies (TSEs), or prion diseases, that are believed to be caused by abnormally configured, host-encoded prion proteins that accumulate in the central nervous tissue (1). CJD has an annual incidence of approximately 1 case per million population in the United States (1) and occurs in three forms: sporadic, genetically determined, and acquired by infection. In the latter form, the incubation period is measured typically in years. Recent evidence that prion infection can cross the species barrier between humans and cattle has raised increasing public health concerns about the possible transmission to humans of a TSE among deer and elk known as chronic wasting disease (CWD) (2). During 1993--1999, three men who participated in wild game feasts in northern Wisconsin died of degenerative neurologic illnesses. This report documents the investigation of these deaths, which was initiated in August 2002 and which confirmed the death of only one person from CJD. Although no association between CWD and CJD was found, continued surveillance of both diseases remains important to assess the possible risk for CWD transmission to humans.
Case Reports
Case 1. In December 1992, a Wisconsin man aged 66 years with a history of seizures since 1969 sought treatment for recurring seizures, increasing forgetfulness, and worsening hand tremors. Electroencephalographic (EEG) examination demonstrated focal epileptiform activity and nonspecific diffuse abnormalities, but no specific diagnosis was made. In February 1993, he was hospitalized for increasing confusion, ataxia, and movement tremors of his extremities. A magnetic resonance image (MRI) demonstrated mild, nonspecific enhancement along the inferior parasagittal occipital lobe. A repeat EEG showed bifrontal intermittent, short-interval, periodic sharp waves, suggesting a progressive encephalopathy; a diagnosis of CJD was suspected. The man died later that month; neuropathologic examination of brain tissue during autopsy indicated subacute spongiform encephalopathy, compatible with CJD.
The man was a lifelong hunter who ate venison frequently. He hunted primarily in northern Wisconsin but also at least once in Montana. He hosted wild game feasts at his cabin in northern Wisconsin from 1976 until shortly before his death. Fixed brain tissue obtained during the autopsy was sent for analysis to the National Prion Disease Pathology Surveillance Center (NPDPSC) and reexamined at the institution where the autopsy was conducted. Histopathologic examination did not substantiate the diagnosis of prion disease. In addition, 27 brain tissue sections were negative for prions by immunostaining despite positive antibody reactions against other proteins (controls), which indicated that other epitopes in the tissue samples were preserved.
Case 2. In May 1999, a Minnesota man aged 55 years with no previous history of a neurologic disease sought evaluation and treatment following a 3-month history of progressive difficulty in writing and unsteadiness of gait. A computerized tomography (CT) scan and MRI examination of his head did not indicate any abnormality. In June 1999, he was hospitalized following onset of dementia, speech abnormalities, and myoclonic jerking. An EEG indicated left-hemispheric periodic sharp waves and moderate generalized background slowing; CJD was diagnosed clinically. In July 1999, following worsening symptoms and development of right upper extremity dystonia, the patient died. Neuropathologic evaluation of brain tissue during autopsy demonstrated widespread subcortical spongiform lesions, consistent with CJD.
The man was not a hunter but had a history of eating venison. He made an estimated 12 visits to the cabin where the wild game feasts were held, but he participated in only one feast during the mid-1980s. Sections of fixed and frozen brain tissue obtained during autopsy were analyzed at NPDPSC, and prion disease was confirmed by immunohistochemical and Western blot testing. The Western blot characteristics and prion disease phenotype in this patient were consistent with the most common form of sporadic CJD, classified as M/M (M/V) 1 (3). Subsequent genetic typing confirmed the presence of methionine homozygosity (M/M) at codon 129 of the patient's prion protein gene.
Case 3. In June 1992, a Wisconsin man aged 65 years sought treatment for progressive slowing of speech, worsening memory, and personality changes. By January 1993, his speech was reduced to one-word utterances. Neurologic examination showed a flat affect, decreased reflexes, and apraxia. A CT head scan showed mild atrophy, and an EEG was normal. Pick's disease was diagnosed. By May, he was unable to perform any daily living activities; he died in August 1993. Neuropathologic evaluation of brain tissue during autopsy showed symmetrical frontal lobe cerebral cortical atrophy and mild temporal lobe atrophy. No Pick's bodies or spongiform lesions were observed.
The man had a history of eating venison and participated regularly in wild game feasts held at the cabin owned by patient 1. He was a lifelong hunter and hunted mostly in Wisconsin but also in Wyoming and British Columbia. No game was brought to the wild game feasts from his hunting trips outside of Wisconsin. Examination of fixed brain tissue sent to NPDPSC demonstrated no lesions indicative of CJD, and immunohistochemical testing with antibody to the prion protein did not demonstrate the granular deposits seen in prion diseases.
Epidemiologic Investigation
Wild game feasts consisting of elk, deer, antelope, and other game that occurred at a cabin in northern Wisconsin owned by patient 1 began in 1976 and continued through 2002. These feasts typically involved 10--15 participants and usually occurred on weekends before or during hunting seasons in the fall and occasionally in the spring. Wild game brought to these feasts usually were harvested in Wisconsin, but three men who attended these feasts reported hunting in the western United States and bringing game back to Wisconsin. These activities took place in Colorado (near the towns of Cortez, Trinidad, Collbran, Durango, and Meeker), Wyoming (near the towns of Gilette and Cody), and Montana (near the town of Malta). CWD was not known to be endemic in these areas at the time that these hunting activities took place.
Information was obtained for 45 (85%) of 53 persons who were identified as possibly participating in the wild game feasts; all were male. Information was obtained by direct interview or from family members of decedents. Of the 45 persons, for whom information was obtained, 34 were reported to have attended wild game feasts. Seven of the 34 feast attendees were deceased, including the three patients. None of the four other decedents had a cause of death attributed to or associated with a degenerative neurologic disorder. None of the living participants had any signs or symptoms consistent with a degenerative neurologic disorder.
Reported by: JP Davis, MD, J Kazmierczak, DVM, M Wegner, MD, R Wierzba, Div of Public Health, State of Wisconsin Dept of Health and Family Svcs. P Gambetti, National Prion Disease Pathology Surveillance Center, Case Western Reserve University, Cleveland, Ohio. L Schonberger, MD, R Maddox, MPH, E Belay, MD, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; V Hsu, MD, EIS Officer, CDC.
Tularemia, or rabbit fever, is a bacterial disease associated with both animals and humans. Although many wild and domestic animals can be infected, the rabbit is most often involved in disease outbreaks.
