Epidemiology and control of rabies in bats in the Netherlands

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1 Rev. sci. tech. Off. int. Epiz., 1992, 11 (4), Epidemiology and control of rabies in bats in the Netherlands J. NIEUWENHUIJS *, J. HAAGSMA ** and P. LINA *** Summary: The first case of bat rabies in the Netherlands was recorded in Since then, 2,540 bats have been examined. In total, 186 bats belonging to two species were found positive for rabies: 182 Eptesicus serotinus and 4 Myotis dasycneme. The virus isolates from the two species were found to be different. Approximately 20% of the E. serotinus bats sent for examination were found positive. The epidemiological findings suggest a stable situation of infection north of the Rhine and the Meuse. A total of 174 humans received postexposure treatment after direct contact with a positive or suspected bat. The public has been warned not to touch bats and, if contact does occur, to send the bat for rabies examination. The authorities also advise post-exposure treatment for dogs and cats which have had contact with a rabies-positive bat. KEYWORDS: Chiroptera - Disease control - Epidemiology - Netherlands - Rabies. INTRODUCTION The occurrence of bat rabies was first recorded in Denmark in 1985, and bat zoologists in the Netherlands subsequently conducted a survey of all bats which were found dead or in very poor condition. To prevent illness, all the researchers received pre-exposure treatment for rabies. The survey began in September 1986, and the first case of bat rabies in the Netherlands was detected on 30 May 1987 (3). Rabies has been reported in bats in Europe since 1954 (1) but had never been reported as causing rabies in humans in Europe until 1977, when it was found to be the source of a human rabies infection in Voroshilovgrad in Russia (2). Two additional human cases were reported in 1985 (one in Belgorod, also in Russia, and the other in Helsinki, Finland) (2). There are no reported cases of transmission of bat rabies to other animals following a bite or natural contact. * Veterinary Public Health Inspectorate, Ministry of Welfare, Public Health and Cultural Affairs, P.O. Box 5406, NL-2280 HK Rijswijk, the Netherlands. ** Central Veterinary Institute, Bacteriology Department, P.O. Box 65, NL-8200 AB Lelystad, the Netherlands. *** National Reference Centre for Nature, Forests and Landscape (IKC-NBLF), P.O. Box 30, 6700 AA Wageningen, the Netherlands.

2 1156 Using monoclonal antibodies, the rabies strains isolated from bats have been characterised as being closely related to the Duvenhage virus, the prototype strain of serotype 4 of the genus Lyssavirus of the Rhabdoviruses. At the World Health Organisation (WHO) Consultation on Rabies held in Essen in July 1988 (4), it was agreed to refer to "European bat Lyssavirus" (EBL) until a detailed analysis could clarify the exact taxonomic position of virus isolates from European bats (10). In this report, information will be presented from research on bat rabies in the Netherlands. MATERIALS AND METHODS Diagnoses were based on the immunofluorescence test (IFT) and mouse inoculation test performed according to WHO Technical Reports (8, 9). RESULTS In May 1987, the first case of bat rabies in the Netherlands was found in the north of the country. Since then, 2,540 Eptesicus serotinus and Myotis dasycneme bats have been examined for rabies. Table I shows the numbers of each bat species examined from 1987 to Table II indicates the number of rabies-positive bats. A total of 186 bats were found positive and the virus isolates were characterised with monoclonal antibodies (239 and 187) from Tübingen. All the isolates were found to be related to serotype 4, the Duvenhage virus. TABLE I Bat species examined for rabies in the Netherlands from 1987 to 1991 Species Eptesicus serotinus Myotis dasycneme Myotis daubentonii Myotis mystacinus Myotis nattereri Nyctalus noctula Nyctalus leisleri Pipistrellus nathusii Pipistrellus pipistrellus Pipistrellus spp Plecotus auritus Plecotus spp Vespertilio murinus Not determined Total 1, Source: Central Veterinary Institute, Lelystad

3 1157 TABLE II Number of rabies-positive bats belonging to two species found in the Netherlands from 1987 to 1991, and the number of post-exposure treatments in humans after contact with rabies-positive bats Positive bats No. of human Year Eptesicus Myotis post-exposure serotinus dasycneme treatments Total Source: Central Veterinary Institute, Lelystad Figure 1 shows the geographical distribution of positive isolates in the Netherlands. Almost all positive bats are found north of the Rhine and the Meuse. The number of bats sent in for examination from this area is similar to the quantities received from other parts of the country, although the number of E. serotinus is smaller. The monthly distribution of the positive and negative bats received is shown in Figure 2. The percentage of rabies-positive bats is approximately 7% of the total number of examined bats; however, in E. serotinus this figure rises to approximately 20%. Table II also shows the number of post-exposure treatments administered to humans after direct contact with a rabies-positive bat. DISCUSSION The control of rabies in insectivorous bats is difficult, as rabies prevalence in these bats is usually low (although it was found to be as high as 20% in E. serotinus). The only control measure which can be employed in a colony infected with rabies involves covering entrance routes to buildings while the bats are absent, so as to prevent their return; this affords a more or less permanent solution. As bats are protected animals, the risk of human infection can be reduced only by making information available to the public. A special directive has been issued detailing the course of action to be followed in the event of contact with bats. Following direct contact with a bat, humans must receive post-exposure treatment as advised by the WHO. The public is warned, through general publicity, not to touch bats which appear to be sick or which are behaving in a strange manner. Following any contact with such a bat, the public is advised to send the bat for rabies examination. Natural transmission of rabies from insectivorous bats to other mammals has not been described in Europe (2). However, transmission to cats is possible, as they often catch bats. Research is being carried out on the sensitivity of other animals to EBL. Preliminary results demonstrate experimental infection in both dogs and cats (5). The

4 1158 Fig. 1 The geographical distribution of rabies-positive bats in the Netherlands from 1987 to 1991

5 1159 FIG. 2 Annual distribution of rabies-positive and rabies-negative bats in the Netherlands from 1987 to 1991 concentration of virus in the saliva of bats is not known and it is therefore very difficult to estimate the risk to these animals of acquiring rabies after contact with a rabiespositive bat. It is also advised that dogs and cats receive post-exposure treatment, given the frequency of contacts with bats (which are seldom recognised) and on account of the probable low infectivity to other animals. Post-exposure treatment consists of two injections with a one-week interval. Investigation by King (6) of two isolates from M. dasycneme bats demonstrated that these were similar but not identical to the serotype 5 virus from a human believed to have died of rabies in Finland. The three isolates were all markedly different from those of European serotine bats. Thus, it can be concluded that rabies in E. serotinus bats is distinct from rabies in the M. dasycneme species. E. serotinus bats do not fly over distances of more than about 50 km, while M. dasycneme are known to fly more than 1,000 km. Consequently, rabies in E. serotinus bats is of local importance. The control of bat rabies in the Netherlands is not yet possible and more research is required. However, successful control measures will be very difficult to achieve. * *

6 1160 ÉPIDÉMIOLOGIE ET PROPHYLAXIE DE LA RAGE CHEZ LA CHAUVE-SOURIS AUX PAYS-BAS. - J. Nieuwenhuijs, J. Haagsma et P. Lina. Résumé : Le premier cas de rage chez la chauve-souris aux Pays-Bas a été rapporté en Depuis lors, chauves-souris ont été examinées. Cent quatre-vingt-six, appartenant à deux espèces différentes, ont été reconnues enragées ; il s'agissait d'eptesicus serotinus dans 182 cas et de Myotis dasycneme dans 4 cas. Les souches de virus isolées des deux espèces étaient différentes. Environ 20 % des animaux de l'espèce E. serotinus examinés étaient enragés. Les données épidémiologiques tendent à indiquer une stabilisation de l'épidémie au nord du Rhin et de la Meuse. Au total, 174 personnes ont été traitées après contact direct avec une chauve-souris atteinte ou suspecte de rage. Il a été demandé au public de ne pas toucher les chauves-souris et, en cas de contact, de faire examiner l'animal. Les autorités recommandent également de traiter les chiens et les chats qui ont été en contact avec une chauvesouris atteinte. MOTS-CLÉS : Chiroptères - Epidémiologie - Pays-Bas - Prophylaxie - Rage. * * * EPIDEMIOLOGÍA Y PROFILAXIS DE LA RABIA EN MURCIÉLAGOS EN LOS PAÍSES BAJOS. - J. Nieuwenhuijs, J. Haagsma y P. Lina. Resumen: El primer caso de rabia en murciélagos registrado en los Países Bajos data de Desde entonces, se examinaron murciélagos. Ciento ochenta y seis, de dos especies diferentes, tenían rabia: Eptesicus serotinus en 182 casos y Myotis dasycneme en 4 casos. Las cepas de virus aisladas de cada especie eran distintas. Alrededor del 20% de los animales de la especie E. serotinus examinados estaban rabiosos. Los datos epidemiológicos tienden a indicar una estabilización de la epidemia al norte de los ríos Rin y Meuse. Se trató en total a 174 personas que habían tenido contacto directo con murciélagos rabiosos o sospechosos de serlo. Se pidió al público no tocar los murciélagos y, en caso de contacto, de hacer examinar el animal. Las autoridades recomiendan asimismo el tratamiento de perros y gatos que hubieran estado en contacto con murciélagos rabiosos. PALABRAS CLAVE: Epidemiología - Países Bajos - Profilaxis - Quirópteros - Rabia. * * REFERENCES 1. ANON. (1982). - WHO Collaborating Centre for Rabies Surveillance and Research, Tübingen, Federal Republic of Germany. Rabies Bulletin Europe, 6 (4). 2. ANON. (1986). - WHO Collaborating Centre for Rabies Surveillance and Research, Tübingen, Federal Republic of Germany. Rabies Bulletin Europe, 10 (4).

7 ANON. (1987). - WHO Collaborating Centre for Rabies Surveillance and Research, Tübingen, Federal Republic of Germany. Rabies Bulletin Europe, 11 (3). 4. ANON. (1988). - WHO Collaborating Centre for Rabies Surveillance and Research, Tübingen, Federal Republic of Germany. Rabies Bulletin Europe, 12 (4). 5. BITSCH V., WESTERGAARD J.M. & VALLE M. (1986). - Bat rabies. Europe. MMWR, 35, KING A., DAVIES P. & LAWRIE A. (1990). - The rabies viruses of bats. Vet. Microbiol., 230, LAFON M., HERZOG M. & SUREAU P. (1986). - Human rabies vaccines induce neutralising antibodies against the European bat virus (Duvenhage). Lancet, i, WHO (1973). - Laboratory techniques in rabies, 3rd Ed. (M.M. Kaplan & H. Koprowski, eds). Monogr. Ser., No. 23, WHO, Geneva, WHO (1984). - WHO Expert Committee on Rabies, Seventh Report. Tech. Rep. Ser., No. 709, WHO, Geneva, 104 pp. 10. WHO (1988). - Report of a WHO Consultation on Rabies. Essen, Federal Republic of Germany, 8 July. WHO/Rab. Res/88.30/Rev 1, 12 pp.

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