The Successful Elimination of Sylvatic Rabies Using Oral Vaccination of Foxes in Slovenia

Abstract

Sylvatic rabies was present in Slovenia between 1973 and 2013, with the red fox as the main reservoir of the rabies virus. The first oral rabies vaccination (ORV) control program in foxes started in 1988, using the manual distribution of baits. Significant improvement of fox vaccination was achieved with the aerial distribution of baits, starting in 1995 and successfully finished with the final, fifty-ninth vaccination campaign in 2019. Between 1979 and 2019, a total of 86,471 samples were tested, and 10,975 (12.69%) rabies-positive animals were identified. Within the ORV, two different vaccines were used, containing modified live virus strain Street Alabama Dufferin (SAD) B19 and SAD Bern, while the last ORV campaigns were completed in 2019, with a vaccine containing a genetically modified strain of SPBN GASGAS. Molecular epidemiological studies of 95 rabies-positive samples, originating from red foxes, badgers, cattle, dogs, martens, cats, and horses, revealed a low genetic diversity of circulating strains and high similarity to strains from neighboring countries. During the elimination program, few vaccine-induced rabies cases were detected: three in red foxes and one case in a marten, with no epidemiological relevance. Slovenia has been officially declared a country free of rabies since 2016.

Research Advances on the Interactions between Rabies Virus Structural Proteins and Host Target Cells: Accrued Knowledge from the Application of Reverse Genetics Systems

“…In addition to the studies mentioned above, some rRABV vaccines have already been licensed and used in the immunization of dogs and wildlife animals in the field, including ERA 333 [95], SPBN GAS [96], SPBN GASGAS [97], SAD dIND [32], ORA-DPC [98,99], rLBNSE-DCBp [86], and LBNSE-CXCL13 [88]; only ERA 333 and SPBN GASGAS have been successfully tested in wildlife target species [100]. As a result, the oral RABV vaccine strain SPBN GASGAS has successfully eliminated Sylvatic Rabies in foxes in Slovenia [101].…”

Oral immunocontraceptive vaccines: A novel approach for fertility control in wildlife

“…70 RRV would offer the best option for an oral immunocontraceptive vaccine because of its good practice characteristics as a non-disseminating engineered virus and successful application in rabies elimination. 15,71 Canine herpesviruses are members of the alpha-herpesvirus subfamily, which are readily genetically modified, nontransmissible, relatively species-specific, and can be administered orally. 72,73 But, none of the foxes that received the first intravenous injection and two intranasal boosts produced anti-fZPC IgG antibodies.…”

“…In fact, the use of live vectors and microencapsulated antigens for the preparation of oral contraceptive vaccines has been prepared for years 10 . Although oral antigens face many challenges, such as biological and physicochemical barriers, and oral tolerance, 11,12 oral delivery systems for immunocontraceptive vaccines have made great progress in the last decades 13–16 . Current, there are a few orally‐delivered vaccines that have been approved for use in human and animal use.…”

“…However, after oral administration with RRV expressing the porcine and fox zona pellucida C protein (pZPC, fZPC), expression of the transgene was not sufficient to elicit a strong immune response against pZPC and fZPC as RRV replicated very poorly in foxes 70 . RRV would offer the best option for an oral immunocontraceptive vaccine because of its good practice characteristics as a non‐disseminating engineered virus and successful application in rabies elimination 15,71 . Canine herpesviruses are members of the alpha‐herpesvirus subfamily, which are readily genetically modified, nontransmissible, relatively species‐specific, and can be administered orally 72,73 .…”

“…10 Although oral antigens face many challenges, such as biological and physicochemical barriers, and oral tolerance, 11,12 oral delivery systems for immunocontraceptive vaccines have made great progress in the last decades. [13][14][15][16] Current, there are a few orally-delivered vaccines that have been approved for use in human and animal use. Oral vaccination provides a more convenient, cost-effective, practical solution of addressing human-wildlife conflict compared to parenteral administrations.…”