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An Epidemic of Sylvatic Rabies in Finland

En epidemi av sylvatisk rabies i Finland - deskriptiv epidemiologi samt resultat av oral vaccinering

Descriptive Epidemiology and Results of Oral Vaccination

Acta Veterinaria Scandinavica volume 33, pages 43–57 (1992)Cite this article

Abstract

When rabies reappeared in Finland in April 1988, the country had been rabies free since 1959. Soon a picture of sylvatic rabies become evident, its main vector and victim being the raccoon dog (Nyctereutes procyonoides). Between 8 April 1988 and 16 February 1989, 66 virologically verified cases were recorded (48 raccoon dogs, 12 red foxes, 2 badgers, 2 cats, l dog and 1 dairy bull) in an area estimated at 1700 km2 in south-eastern Finland. The greatest distance between recorded cases was 67 km. A positive reaction with monoclonal antibody p-41 indicated that the virus was an arctic-type strain.

A field trial on oral immunization of small predators was initiated in September 1988 using Tübingen fox baits according to the Bavarian model of bait distribution. Each bait contained 5*107 TCID50/ml modified live rabies virus (SAD-B19). The 6 months’ surveillance indicate a seroconversion rate of 72% (N=126) in the raccoon dog population, 67% (N=56) in the red foxes and 13% (N=16) in the badgers, when titers ≥1.0 IU/ml are considered seropositive. In the whole follow-up period, no statistically significant difference could be detected between the raccoon dogs and red foxes in the rate of seroconversion or in the uptake of tetracycline from the baits. Notably high antibody levels were recorded in both raccoon dogs and red foxes within 4–5 months after vaccination. Of the seropositive animals, the proportion of animals with titers 3.0 IU/ml or greater was higher in raccoon dogs (73%) than in red foxes (51%) (x2= 5.29, p< 0.05). The trial shows that raccoon dogs can be immunized against rabies in the field with vaccine baits originally developed for controlling sylvatic rabies in foxes.

Sammanfattning

Då rabies i april 1988 återuppträdde i Finland hade landet varit rabiesfritt sedan 1959. Bilden av sylvatisk rabies stod snart uppenbar. Dess främsta bärare och offer var mårdhunden (Nycrereutes procyonoides). Mellan 8.April 1988 och l6.Februari 1989 registrerades 66 virologiskt verifierade fall (48 mårdhundar, 12 rödrävar, 2 grävlingar, 2 katter, 1 hund och 1 ungtjur). Det till 17oo km2 uppskattade smittområdet ligger i sydöstra Finland. Det längsta avståndet mellan registrerade fall var 67 km. Med monoklonal antikroppsteknik visades virusstammen reagera positivi med Mab P-41 och således vara av arktisk typ.

I september 1988 inleddes ett fältförsök avseende oral immunicering av markrovjur mot rabies med s.k. Tübingen vaccinebeten för räv och distribution av betena enligt s.k. bayersk modeil. Varje bete innehöll modifierat, levande rabiesvirus (SAD B19) i en dos av 5 × 107 TCID50/ml. Under en 6 månaders uppföljningsperiod erhållna resultat visade serokonvation hos 72% av mårdhundarna (N=126), 67% av rödrävarna (N=56) och 13% av grävlingarna (N=16), då titer ≥1.0 IU/ml bedömes som seropositiva. Under hela uppföljningsperioden kunde ingen statistiskt signifikant skillnad påvisas mellan mårdhund och räv angående vare sig frekvens av serokonvation eller upptagning av tetracyklin från betena. Hos både mårdhundar och rävar påvisades anmärkningsvärt höga antikropps-titer under 4-5 månader efter vaccineringen. Proportionen av seropositiva individer med titer ≥3.0 IU/ml var högre bland mårdhundarna (73%) än bland rödrävarna (51%), x2=5.29, p< 0.05). Försöket visar, att mårdhunden kan immuniceras mot rabies i fält med vaccin och beten som ursprungligen utvecklats för bekämping av sylvatisk rabies hos rödräv.

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Authors and Affiliations

  1. Field Department and Department of Virology, National Veterinary Institute, P.O. Box 368, 00101, Helsinki, Finland

    Matti Nyberg, Katariina Kulonen, Erkki Neuvonen, Christine Ek-Kommonen, Marja Nuorgam & Bengt Westerling

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  1. Matti Nyberg
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  2. Katariina Kulonen
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Nyberg, M., Kulonen, K., Neuvonen, E. et al. An Epidemic of Sylvatic Rabies in Finland. Acta Vet Scand 33, 43–57 (1992). https://doi.org/10.1186/BF03546935

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Acta Veterinaria Scandinavica

ISSN: 1751-0147