No 5 - 2010

Rabies prophylaxis

In Denmark, being bitten by a bat is usually the only indication for prophylactic treatment against rabies. If, after being bitten by other animals, there is reason to suspect that the animal has rabies, the animal should be examined by a veterinary. The veterinary will, if necessary, destroy the animal and arrange further investigation.

In other parts of the world, rabies is more widespread. Transmission occurs through the penetrating bite of an animal infected with rabies, or on rare occasions through direct contact between infected saliva and mucous membranes or wounds.

Prophylactic treatment after possible exposure should be discussed with the Department of Epidemiology, and human rabies immunoglobulin (HRIG) and vaccine may be ordered by general practitioners at the expense of the National Health Service. Pre- as well as post-exposure prophylaxis recommendations are further described in EPI-NEWS 3/08.

Post-exposure vaccination

In 2009 a total of 116 patients received prophylactic rabies treatment following animal bites, Table 1.

A total of 65 persons were treated with HRIG in addition to vaccination.

Bat bites in Denmark were the reason why 16 persons received post-exposure prophylaxis. None of the bats were submitted for testing. One person was bitten by a dog which was destroyed and tested negative for rabies. Treatment was discontinued when the test results were known. One person, who was bitten by a fox, received prophylactic treatment. In retrospect, there was no indication for treatment in any of the outlined cases, as rabies does not occur in dogs or foxes in Denmark.

An additional 16 persons were exposed to rabies in the remaining parts of Europe (incl. Turkey), 70 in Asia, 9 in Africa, 2 in Central and South America, and in one case the country of exposure was unknown.

A total of 50 patients were treated following possible rabies exposure in Thailand, incl. 24 after being bitten by monkeys, 24 by dogs, one by a cat, and in one case the type of animal was not known. The age of the persons exposed in Denmark ranged from 9 to 84 years (median 48). The age of persons exposed abroad ranged from 1 to 72 (median 29).

Commentary

About 84% of the persons who received prophylactic treatment had been exposed to rabies abroad, more than half in Thailand. When giving advice prior to foreign travel, it is important to mention the risk of rabies associated with animal contact. Travellers should be advised to limit animal contact and see a physician without delay in case of a bite.

(A.H. Christiansen, S. Cowan, Department of Epidemiology)

Rabies in animals

Classic sylvatic rabies virus has not been observed in Denmark since 1982, but it is endemic in Greenland, where polar foxes regularly transfer the infection to sledge dogs and other mammals. In 2009, rabies was detected in five polar foxes and two sheep, Table 2.

Bats are a reservoir for EBLV (European Bat Lyssavirus). EBLV was first detected in Danish bats in 1985 and has subsequently been found every year. The number of positive detections as well as the number of animals tested has varied considerably. In 2009, EBLV was detected in one bat in Denmark, Table 2.

(T.B. Rasmussen, DTU National Veterinary Institute, Lindholm)

Gastroenteritis outbreak

In the course of Week 3, ten different gastroenteritis outbreaks comprising more than 250 symptomatic persons were notified to the Regional Veterinary and Food Administration, Region East. The outbreaks all occurred in groups of people who had received open or closed sandwiches from catering companies.

The clinical picture suggested norovirus and suspicions were subsequently confirmed by stool sample testing. The only probable common food source was green lettuce of the Lollo Bionda type. Trace-back showed that the lettuce was supplied to two packaging facilities by a French company via a Danish importer. The lettuce was withdrawn by 22 January at the request of the Veterinary and Food Administration. Subsequently, suspicions were confirmed as norovirus was detected in a packed head of lettuce from one of the catering companies.

A cohort investigation performed in a company where several types of food had been served pointed to sandwiches containing lettuce as the cause of disease. This finding was supported by case reports from smaller companies which also suggested that the cause was open or closed sandwiches containing lettuce.

In several cases, the proportion of diseased persons and the duration of symptoms exceeded what would be expected for norovirus, which gave rise to a suspicion that more infectious agents could be in play. Stool samples from the affected cases tested positive for enterotoxigenic E. coli (ETEC), Staphylococcus aureus, Clostridium perfringens and norovirus of the genogroups I as well as II. Microbiological, epidemiological and track-back investigations are in progress.

Commentary

The cause of the lettuce contamination is currently unknown, but the concurrent presence of numerous infectious agents may probably have been caused by irrigation or rinsing water contaminated with human stools, as norovirus and ETEC are not zoonoses. The lettuce was distributed widely in Denmark. It was primarialy used by catering companies, but has also been sold in retail stores. An increased occurrence of acquired ETEC cases in Denmark during the same period indicates that in addition to the currently known cases, more persons may have been exposed to infection.

(S. Ethelberg, Dept. of Epidemiology, M. Lisby, Regional Veterinary and Food Control Authority East, T. Jensen, Danish Veterinary and Food Administration)

Individually notifiable diseases and selected laboratory diagnosed infections  

3 February 2010