No 16 - 2010

Creutzfeldt-Jakob Disease (CJD)

Creutzfeldt-Jakob disease (CJD) is a fatal neurodegenerative condition comprising three subgroups: sporadic, hereditary and acquired (iatrogenic and variant CJD). The occurrence of sporadic CJD is approx. 1-2 cases per million and the corresponding numbers for the other subgroups are even lower. Variant CJD, which is associated with mad cow disease, has not been detected in Danish cases.

CJD diagnosis and classification

Post mortem brain autopsy or biopsy are the only methods to diagnose CJD with certainty. If the patient was not autopsied or is still alive, a combination of criteria may assist in reaching a probable or possible diagnosis, Table 1. Classification of sporadic CJD is outlined in Table 2.

CJD surveillance

In Denmark, CJD has been notifiable since May 1997, EPI-NEWS 10/97. Physicians treating a patient with suspected CJD must report the case using form 1515. On reception, the SSI Department of Epidemiology returns a specific CJD questionnaire (in Danish language) to the physician to gather information on clinical disease course and supplementary clinical measures. The questionnaire may also be downloaded at www.ssi.dk and forwarded to the Department of Epidemiology, SSI, along with form 1515.

14-3-3-protein and CJD

Finding 14-3-3-protein in the cerebrospinal fluids is one of several classification criteria. The presence of the protein demonstrates that brain neurons are damaged, and is considered one of the best biomarkers for sporadic CJD. However, the protein may also occur in association with other brain-related diseases, e.g. encephalitis. Consequently, a 14-3-3-protein finding will support a CJD diagnosis, but will neither confirm nor exclude such diagnosis.

Sporadic CJD in Denmark

Figure 1 shows the number of confirmed, probable and possible cases of sporadic CJD from 1997 to 2009. The figures are recorded by year of death. Occurrence of sporadic CJD has been relatively stable throughout the period, with an average of seven (range 4-11) annual cases. The M/F ratio was 1:1. The mean age at death was 66 years (range 40-89).

Commentary

As CJD is a rarely occurring disease which is difficult to diagnose, all signs of CJD should be investigated thoroughly. Furthermore, it is essential that autopsies be performed in all suspected CJD cases, as the final diagnosis may only be made by neuropathological examination.

(S. Gubbels, S. Bacci, S. Cowan, Dept. of Epid., M. Christiansen, Dept. of Clin. Biochem., H. Laursen, Dept. of Neuropathology, H. Høgenhaven, Dept of Clin. Neurophysiol., Copenhagen University Hospital)

Bovine spongiform encephalopathy (Mad cow's disease)

Surveillance of bovine spongiform encephalopathy (BSE) in Denmark comprises passive as well as active measures, EPI-NEWS 26-33/04. Since active surveillance was introduced, more than two million cattle have been tested, Table 3. In 2009, surveillance has been changed to include testing of all cattle above the age of four years, regardless of type.

In 2000, before active surveillance was initiated, the first case of BSE in Danish-born cattle was detected. So far, a total of 15 cases of BSE have been found in Danish-born cattle in Denmark, and in addition, three cases have been observed in exported cattle. The most recent notified case of BSE in Denmark was detected in November 2009.

Commentary

In 2004 the expectation was that Denmark would see a limited number of BSE in the following years, after which the disease would cease to occur here. Such expectation has proven to be exact as only two cases have been detected since 2004. These animals were born in 1995 and 1996, prior to the 1997 feed ban, EPI-NEWS 26-33/04.

Approx. 5,000 live cattle born before 1997 remain, and it is therefore not possible to exclude that BSE may occur among cattle with this age. BSE has a mean incubation period of 5-6 years. As the nine years after the 2001 feed ban have brought no BSE cases among cattle born after 2001, EPI-NEWS 26-33/04, the ban has been effective. The number of positives in the EU is decreasing rapidly which shows that BSE is becoming extinct in Denmark as well as in the rest of the EU. In future, surveillance may therefore be reduced further.

(H. Rugbjerg, Danish Veterinary and Food Administration)

Individually notifiable diseases and selected laboratory diagnosed infections  

21 April 2010