Ballistic Method of Wild Animal Vaccination

Ballistic Method of Wild Animal Vaccination

Alexander Denisov, Olga Karpova, Olga Rybakova, Svetlana Popova, Roman Borovick,

(RCT&HRB, Serpukhov, Moscow Region); Konstantin Salmakov (ARVI, Kazan, Tatarstan);

Oleg Sklyarov, Arkady Klimanov, Konstantin Shumilov (VGNKI, Moscow);

Mikhail Brynskykh (Prioksko-Terrasny Preserve, Danki, Serpukhov, Moscow Region)

For remote vaccine delivery a ballistic method with the use of 5.6 mm caliber bullet was developed. Live brucellosis vaccines B. abortus 82 and B. abortus 19 were used as model vaccines; control - hand-injection method. Field-testing of the ballistic method was conducted on live penned heifers and bison fired with vaccine-loaded bullets from distance of 80 - 100 meters. It was shown that the bullets were deformed (flatted or broken-up into small pieces) while passing through the hide and muscular tissues of animals, rapidly releasing Brucella cells and colonizing muscular tissues. They did not cause excess morbidity or wounds and did not greatly influence on animal behavior. The presence of vaccine strain cells and their distribution within the animal body was demonstrated using bacteriological method and PCR. The effective post-vaccinal immunological response from vaccines delivered with biobullets was demonstrated using serological tests (reaction of agglutination - RA, indirect reaction of haemagglutination – IHAR, complement fixation reaction - CFR, Rose-Bengal Test - RBT), as well as indices of humoral (high titers of R- and S-antibodies) and cellular (increase of lymphocyte proliferation) immunity. This immunological response was comparable to hand-injection of vaccines. The study has demonstrated potential of the B. abortus 82 strain as an effective vaccine as well as of the developed ballistic method for remote delivery of viable brucellosis vaccines and vaccination of wild animals.

Introduction

Prophylaxis of infectious diseases among wild animals is an urgent problem considering that they are a carrier of some infections (brucellosis, plague, tularemia, rabies, etc.) and a source of infection for farm animals and humans. That is why, in many countries worldwide the programs on eradication of these infections are mainly directed to wild animals.

One of the methods for wild animals’ infection control is specific prophylaxis using vaccines. A vaccine intended for use in the wildlife should be highly immunogenic and should induce strong immunologic responses in animals after a single vaccination [1]. Different types of vaccines have been developed and currently are being broadly used in many countries. Most of them are routinely used for immunization of domestic livestock. However, there are many obstacles when attempting to apply the current vaccines to free-ranging animals and one of the problems is a reliable delivery of vaccine.

For most wild animals the distance range necessary to safely deliver a vaccine is about 40-60 meters depending on animal species. However, it is not always possible to reach an animal so closely. At the same time, it is hardly possible to deliver vaccines to animal from longer distances.

Use of biobullets is one of most suitable methods for remote delivery of vaccines to wild animals. At present, .25 caliber degradable biobullets are being successfully used to treat and vaccinate farm and wild animals [2]. Many of the existing types of biobullets are intended for use with clip-fed, pump-operated, compressed-air-powered rifles. An external air tank which must be transported with a rifle is needed for firing such biobullets. That is very uncomfortable especially in field vaccination. In addition, maximum effective range of such biobullets is approximately 25-30 m, which is not quite enough [3, 4]. Therefore, development of a biobullet and suitable method of delivering vaccines and drugs to free-ranging animals at long ranges (about 80-100 m) still remains an urgent task, which needs to be fulfilled.

The purpose of the study was development and field testing of ballistic method for remote delivery of live vaccines to wild animals by the example of live brucellosis vaccine.

Results and discussion

Field testing of ballistic method was performed on live penned heifers (n=6) and bison (n=1). Remote delivery of vaccine was conducted by ballistic method using the developed 5.6 mm caliber bullets. Animals were vaccinated by B. abortus 82 and B. abortus 19 vaccine strains. Hand injection was used for control.

The studies demonstrated that all bullets fired from a distance of 80-100 meters reached the target animals, not causing excess morbidity or wounds and not sufficiently affecting animal behavior. The bullets were deformed (flatted or broken-up into small pieces) while passing through the hide and muscular tissues of animals rapidly releasing Brucella cells and colonizing muscular tissues.

Serological studies of heifer blood samples demonstrated that after ballistic delivery of vaccine from B. abortus 82 strain specific R-antibodies were detected after 7 days following vaccination (in complement fixation reaction - CFR and indirect heamagglutination reaction - IHAR). Their levels were comparable with those after hand-injection. R-antibody titers increased by 21 day and considerably increased after re-vaccination. Antibodies to S-antigen were not detected on the earlier stages of post-vaccinal immunity formation. They were found only on 14th day after re-vaccination (after 49 days following the first vaccination) in low titers. On the contrary, after ballistic and hand-injection of B. abortus 19 strain S-antibodies in high titers were detected on 7th day in all serological reactions (CFR, IHAP, reaction of agglutination - RA, and Rose Bengal Test -RBT) and maintained throughout the period of observation (Table 1).

Table 1

Antibody titers in heifer blood sera in RA with brucellosis S-antigen

Animal #	Strain/vaccination method	Days after vaccination
Animal #	Strain/vaccination method	0	7	14	21	28	42	49	56	63
526	B.abortus 82 /i.m.	0	0	0	0	0	0	0	1:100	1:100
531	B.abortus 82 / i.m.	0	0	0	0	0	0	1:100	1:100	1:200
529	B.abortus 82/ball.	0	0	0	0	0	0	1:100	1:200	1:200
530	B.abortus 82/ ball.	0	0	0	0	0	0	0	1:100	1:100
546	B.abortus 19/ i.m.	0	1:1600	1:1600	1:6400	1:800	1:400	1:400	1:400	1:400
534	B.abortus 19/ ball.	0	1:400	1:400	1:1600	1:200	1:200	1:200	1:400	1:800

Dynamics of brucellosis IgG type R- and S-antibody formation determined by ELIZA correlated with serological data. On the whole, the levels of specific R- and S-antibodies were higher after hand injections than after ballistic delivery of both B. abortus 82 and 19 vaccines.

Vaccination of heifers by B. abortus 82 and 19 vaccine strains using both hand injection and ballistic method induces cellular immunity and increases total amount of phagocytic cells in blood as well as their activity. No essential distinctions in the cellular immunity level as well as in the indices of phagocytic activity of blood cells isolated from vaccinated heifers were observed after vaccination with B. abortus 82 and B. abortus 19 strains by both ballistic and intramuscular methods.

Preliminary data from the studies on bison vaccination with B. abortus 82 vaccine using ballistic method proved high efficiency of the developed biobullet. Biobullet penetrated at right angle to the bison body making rounded entry holes thus proving their appropriate aerodynamic characteristics. The presence of vaccine strain cells in the bison body was demonstrated using bacteriological method and PCR. High level of cellular immunity (blast transformation reaction index =1.96, Fig.1), high titers of R-antibodies (in ELISA - 1: 1280000), as well as S-antibodies (in RA – 1:50) were found in bison blood serum.

Conclusion

Ballistic method for remote delivery of live brucellosis vaccines with the use of 5.6 mm caliber bullet was developed and its field trials on heifers and bison were conducted. Vaccines B. abortus 82 and B. abortus 19 delivered by ballistic method induced specific immune response in target animals similarly to hand injection and proved to be appropriate for wild animal vaccination.

AG

LPS

FHA

Fig. 1

Reaction of blast transformation of lymphocytes isolated from bison's blood

after ballistic vaccination with B.abortus 82 vaccine

- before vaccination; - after vaccination.

(FHA – phytohaemagglutinin; LPS – lypopolysaccharide; AG – brucellosis antigen)

References:

1. Olsen S.C., Elzer P.H. Wildlife vaccines: promises and the perils. In Kreeger TJ, editor. Brucellosis in Elk and Bison in the Greater Yellowstone Area. Cheyenne: Wyoming Game and Fish Department; 2002. p. 38-42.

2. Keith A, Kreeger T. J, Roffe T. J. Overview of delivery systems for the administration of vaccines to elk and bison of the Greater Yellowstone Area. In Kreeger T.J., editor. Brucellosis in Elk and Bison in the Greater Yellowstone Area. Cheyenne: Wyoming Game and Fish Department; 2002. p. 66-79.

3. McNeil HJ, Miller MW, Conion JA, Barker IK, and Schewen PT. Effects of delivery method on serological responses of bighorn sheep to multivalent Pastuerella Haemolyitica supernatant vaccine. J Wildl Dis 2000;36:79-85.

4. Jessup D., DeForge J.R., Sandberg S. Biobullet vaccination of captive and free-ranging bighorn sheep. Proceedings of the 2^nd International Game Ranching Symposium, 1992. p. 429-34.