vCJD (Variant Creutzfeldt-Jakob Disease)
What is the variant form of CJD that the experts in the United Kingdom believe might be related to the BSE outbreak in cattle?
In contrast to the classic form of CJD, the variant form in the United Kingdom predominantly affects younger persons (median age at death around 29 years) and has atypical clinical features. These atypical features include prominent psychiatric symptoms or sensory symptoms at the time of clinical presentation or early in the course of the illness, delayed onset of neurologic abnormalities, duration of illness of at least 6 months, and a diffusely abnormal non-diagnostic electroencephalogram.
The characteristic neuropathologic profile of variant CJD includes, in both the cerebellum and cerebrum, numerous kuru-type amyloid plaques surrounded by vacuoles and prion protein (PrP) accumulation at high concentration indicated by immunohistochemical analysis. Recently published data indicate that the epidemic of variant CJD in the United Kingdom may have already reached a peak.
Is there evidence directly linking this newly recognized variant of CJD to BSE exposure?
There is strong epidemiologic and laboratory evidence for a causal association between variant CJD and BSE. The absence of confirmed cases of variant CJD in other geographic areas free of BSE supports a causal association.
In addition, the interval between the most likely period for the initial extended exposure of the population to potentially BSE-contaminated food and onset of initial variant CJD cases is consistent with known incubation periods for CJD.
An experimental study reported in June 1996 showed that three cynomologus macaque monkeys inoculated with brain tissue obtained from cattle with BSE had clinical and neuropathological features strikingly similar to those of variant CJD.
A study published in 1996 indicated that a Western blot analysis of infecting prions obtained from 10 variant CJD patients and BSE-infected animals had similar molecular characteristics that were distinct from prions obtained from patients with other types of CJD.
An experimental study involving inoculation of a panel of inbred mice with the agents causing BSE and variant CJD substantially increased the strength of the scientific evidence for a causal association between variant CJD and BSE. In this study, groups of inbred mice and a group of cross-bred mice inoculated with brain homogenates from variant CJD cases were reported to have had latency periods and lesion profiles consistent with the BSE pattern.
The latency period, neuropathology, and disease-causing PrP isoforms in transgenic mice expressing bovine PrP that were inoculated with variant CJD, BSE, and scrapie brain extracts provided additional evidence supporting the link between BSE and variant CJD.
Has CDC initiated increased surveillance efforts to determine whether the newly recognized variant of CJD (vCJD) occurs in the United States?
Yes. The possibility that BSE can spread to humans has focused increased attention on the desirability of enhancing national surveillance for Creutzfeldt-Jakob disease (CJD) in the United States.
The Centers for Disease Control and Prevention (CDC) monitors the trends and current incidence of CJD in the United States using several surveillance mechanisms. On a routine basis, CDC reviews the national multiple cause-of-death data taken from death certificates and compiled by the National Center for Health Statistics, CDC. In addition, with the support of the Council of State and Territorial Epidemiologists, CDC conducts follow-up review of clinical and neuropathology records of CJD decedents aged <55 years who are identified through the national mortality data analysis or reported by health care workers. This is the age group in which almost all of the vCJD cases worldwide have occurred to date.
In 1996-97, CDC established, in collaboration with the American Association of Neuropathologists, the National Prion Disease Pathology Surveillance Center at Case Western Reserve University, which performs special state-of-the-art diagnostic tests for prion diseases, including post-mortem tests for vCJD. These tests are provided free of charge to all U.S. physicians.
Currently, CDC works with selected state health departments on various enhanced CJD surveillance projects and education programs regarding the importance of autopsy to both the surveillance and diagnosis of CJD. In addition, CDC collects, reviews and when indicated, actively investigates specific reports by health care personnel or institutions in all states of possible iatrogenic CJD and variant CJD cases.
These surveillance methods for CJD enhance the ability to identify cases of variant CJD when such cases occur in the United States.
Have any cases of variant CJD (vCJD) been reported in the United States?
Yes, three cases of vCJD have been reported from the United States. By convention, variant CJD cases are ascribed to the country of initial symptom onset, regardless of where the exposure occurred. There is strong evidence that suggests that two of the three cases were exposed to the BSE agent in the United Kingdom and that the third was exposed while living in Saudi Arabia.
The first patient was born in the United Kingdom in the late 1970's and lived there until a move to Florida in 1992. The patient had onset of symptoms in November 2001 and died in June of 2004. The patient never donated or received blood, plasma, or organs, never received human growth hormone, nor did the patient ever have major surgery other than having wisdom teeth extracted in 2001. Additionally, there was no family history of CJD.
The second patient resided in Texas during 2001-2005. Symptoms began in early 2005 while the patient was in Texas. He then returned to the United Kingdom, where his illness progressed, and a diagnosis of variant CJD was made. The diagnosis was confirmed neuropathologically in early 2006 at the time of the patient's death. While living in the United States, the patient had no history of hospitalization, of having invasive medical procedures, or of donation or receipt of blood and blood products. The patient almost certainly acquired the disease in the United Kingdom. He was born in the United Kingdom and lived there throughout the defined period of risk for human exposure to the agent of bovine spongiform encephalopathy (BSE, commonly known as "mad cow" disease). His stay in the United States was too brief relative to what is known about the incubation period for variant CJD.
The third patient was born and raised in Saudi Arabia and has lived in the United States since late 2005. The patient occasionally stayed in the United States for up to 3 months at a time since 2001 and there was a shorter visit in 1989. The patient's onset of symptoms occurred in Spring 2006. In late November 2006, the Clinical Prion Research Team at the University of California San Francisco Memory and Aging Center confirmed the vCJD clinical diagnosis by pathologic study of adenoid and brain biopsy tissues. The patient has no history of receipt of blood, a past neurosurgical procedure, or residing in or visiting countries of Europe. Based on the patient's history, the occurrence of a previously reported Saudi case of vCJD attributed to likely consumption of BSE-contaminated cattle products in Saudi Arabia, and the expected greater than 7 year incubation period for food-related vCJD, this U.S. case-patient was most likely infected from contaminated cattle products consumed as a child when living in Saudi Arabia. The patient has no history of donating blood and the public health investigation has identified no known risk of transmission to U.S. residents from this patient.
Information Obtained From National Institute Of Health