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Effect of maternal immunity on the immune response to oral vaccination against rabies in young foxes

Thomas F. MüllerInstitute for Epidemiological Diagnostics, Institute for Epidemiology, Federal Research Centre for Virus Diseases of Animals, WHO Collaborating Centre for Rabies Surveillance and Research, 16868 Wusterhausen, Germany.

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Peter SchusterImpfstoffwerk Dessau-Tornau GmbH, PO Box 214, 06855 Rosslau, Germany.

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Ad C. VosImpfstoffwerk Dessau-Tornau GmbH, PO Box 214, 06855 Rosslau, Germany.

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Thomas SelhorstInstitute for Epidemiological Diagnostics, Institute for Epidemiology, Federal Research Centre for Virus Diseases of Animals, WHO Collaborating Centre for Rabies Surveillance and Research, 16868 Wusterhausen, Germany.

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Ulf D. WenzelFur Animal Breeding Station, Nerzfarm Gleinermühle, 06774 Söllichau, Germany.

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Andreas M. NeubertImpfstoffwerk Dessau-Tornau GmbH, PO Box 214, 06855 Rosslau, Germany.

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Abstract

Objective—To determine effect of maternal antibodies on immune response to oral vaccination against rabies in young foxes.

Animals—250 cubs from 48 vixens.

Procedure—Sera were obtained from cubs of 36 vaccinated (maternally vaccinated [MV+]) and 12 nonvaccinated (MV) vixens between 23 and 71 days of age and tested for neutralizing antibodies. Seventy-one MV+ cubs and 33 MV- cubs were vaccinated orally with modified-live virus vaccine SAD B19. Geometric mean titer (GMT) was determined in these cubs approximately 21, 39, and 57 days after vaccination. In a subsequent experiment, 10 vaccinated MV+ cubs, 6 vaccinated MV cubs, and 6 control cubs were challenge inoculated with virulent rabies virus approximately 100 days after vaccination.

Results—Serum GMT of nonvaccinated MV cubs (0.23 U/ml) was significantly greater than that of nonvaccinated MV cubs (0.15 U/ml). The GMT of vaccinated MV+ cubs 21, 39, and 57 days after vaccination were 2.85, 2.11, and 0.79 U/ml, respectively, and were significantly less than those of vaccinated MV cubs (12.19, 6.76, and 4.02 U/ml, respectively). All challenge-inoculated cubs with GMT < 0.5 U/ml succumbed to rabies.

Conclusion and Clinical Relevance—Partially impaired immune response in cubs < 8 weeks old from vaccinated vixens causes insufficient protection against rabies. Inhibition of the immune response persists longer than the period during which maternal antibodies are detectable. Thus, oral vaccination campaigns for young foxes in areas where vaccination has been performed need to be reconsidered. (Am J Vet Res 2001;62:1154–1158)

Abstract

Objective—To determine effect of maternal antibodies on immune response to oral vaccination against rabies in young foxes.

Animals—250 cubs from 48 vixens.

Procedure—Sera were obtained from cubs of 36 vaccinated (maternally vaccinated [MV+]) and 12 nonvaccinated (MV) vixens between 23 and 71 days of age and tested for neutralizing antibodies. Seventy-one MV+ cubs and 33 MV- cubs were vaccinated orally with modified-live virus vaccine SAD B19. Geometric mean titer (GMT) was determined in these cubs approximately 21, 39, and 57 days after vaccination. In a subsequent experiment, 10 vaccinated MV+ cubs, 6 vaccinated MV cubs, and 6 control cubs were challenge inoculated with virulent rabies virus approximately 100 days after vaccination.

Results—Serum GMT of nonvaccinated MV cubs (0.23 U/ml) was significantly greater than that of nonvaccinated MV cubs (0.15 U/ml). The GMT of vaccinated MV+ cubs 21, 39, and 57 days after vaccination were 2.85, 2.11, and 0.79 U/ml, respectively, and were significantly less than those of vaccinated MV cubs (12.19, 6.76, and 4.02 U/ml, respectively). All challenge-inoculated cubs with GMT < 0.5 U/ml succumbed to rabies.

Conclusion and Clinical Relevance—Partially impaired immune response in cubs < 8 weeks old from vaccinated vixens causes insufficient protection against rabies. Inhibition of the immune response persists longer than the period during which maternal antibodies are detectable. Thus, oral vaccination campaigns for young foxes in areas where vaccination has been performed need to be reconsidered. (Am J Vet Res 2001;62:1154–1158)