377
Problems have been recorded previously with the oral method, insofar as protection was short-lived although progress on oral delivery has been made. Thus in a
comparison of injection and oral methods of uptake with a chloroform inactivated
vaccine, Anderson and Nelson ( 1974 ) did not fi nd any antibody in fi sh fed with a
vaccine for 7 days; whereas a low titre of 1:16 and 1:32 resulted in trout which were
injected. Moreover, injected fi sh were protected for 12 weeks compared to only 6
weeks in the group which received the oral preparation. Similarly, a comparison of
injection, immersion, shower and spray methods showed that injection offered the
best protection against artifi cial challenge with Y. ruckeri (Johnson and Amend
1983a ). In a comparison of the effi cacy of injection, oral uptake and anal intubation,
Vigneulle ( 1990 ) favoured the fi rst mentioned in terms of protection. The nasal and
intraperitoneal delivery of a combined live attenuated infectious hematopoietic
necrosis virus (IHN) and inactivated whole cell ERM vaccine was evaluated in rainbow trout, and challenged after 7 and 28 days. The best protection was recorded
after 28 days in the i.p. vaccinated group, although early protection was demonstrated following nasal administration (LaPatra et al. 2015 ). Moreover, interestingly, antibodies were found in the serum of rainbow trout vaccinated by injection
and anal intubation, but not by the oral route. Oral administration of rainbow trout
with a commercial formalin-inactivated whole cell vaccine or a locally made experimental product was carried out (single and × 50 doses) with or without booster
doses 4 months later. A further group received a single dose anally. All groups were
challenged 6 months after the primary administration with heavy mortalities in
groups apart from the anally and orally (× 50 dose) vaccinated fi sh; all fi sh in these
groups survived challenge. Thus, anal uptake gave full protection as did the very
dose administered orally, which suggested that there is signifi cant degradation (=
digestion) of the antigens in the stomach before reaching the intestine where it is
available to the immune system, and specifi cally the lymphocytes (Villumsen et al.
2014 ). Unfortunately, it must be emphasised that injection is only feasible for large
and/or valuable fi sh and not for the millions of fry/fi ngerlings which abound on the
typical fi sh farm. However, ERM vaccines have been used successfully on fi sh
farms when administered by bathing (Tebbit et al. 1981 ). In one investigation,
22959239 rainbow trout were vaccinated by a 90 s dip in a commercial vaccine
preparation. The results were very encouraging with signifi cantly reduced losses
attributable to ERM. In this particular trial, the vaccine effected an 84 % reduction
in mortalities due to ERM (Tebbit et al. 1981 ). Of additional benefi t, there was a
concomitant decrease in the use of medication by 77 %, and an increase in food
conversion of 13.7 %. Analogous fi ndings have been reported by Amend and
Eschenour ( 1980 ) and Newman and Majnarich ( 1982 ).
Optical projection tomography and immunohistochemistry was used to visualize
the uptake and processing of a whole cell vaccine by bath in rainbow trout.
Tomography showed that vaccine was initially taken up via secondary gill lamellae
from within 30 s of vaccination. At 5 to 30 min, vaccine cells were found on other
mucosal surfaces, namely the skin and olfactory bulb; at 3-h, the digestive tract was
fi lled with a complex of vaccine and mucus, remaining there for >24 h. At 24 h,
vaccine cells were located in the blood, spleen and trunk kidney (Ohtani et al. 2015 ).
Yersinia ruckeri
Problems have been recorded previously with the oral method, insofar as protection was short-lived although progress on oral delivery has been made. Thus in a
comparison of injection and oral methods of uptake with a chloroform inactivated
vaccine, Anderson and Nelson ( 1974 ) did not fi nd any antibody in fi sh fed with a
vaccine for 7 days; whereas a low titre of 1:16 and 1:32 resulted in trout which were
injected. Moreover, injected fi sh were protected for 12 weeks compared to only 6
weeks in the group which received the oral preparation. Similarly, a comparison of
injection, immersion, shower and spray methods showed that injection offered the
best protection against artifi cial challenge with Y. ruckeri (Johnson and Amend
1983a ). In a comparison of the effi cacy of injection, oral uptake and anal intubation,
Vigneulle ( 1990 ) favoured the fi rst mentioned in terms of protection. The nasal and
intraperitoneal delivery of a combined live attenuated infectious hematopoietic
necrosis virus (IHN) and inactivated whole cell ERM vaccine was evaluated in rainbow trout, and challenged after 7 and 28 days. The best protection was recorded
after 28 days in the i.p. vaccinated group, although early protection was demonstrated following nasal administration (LaPatra et al. 2015 ). Moreover, interestingly, antibodies were found in the serum of rainbow trout vaccinated by injection
and anal intubation, but not by the oral route. Oral administration of rainbow trout
with a commercial formalin-inactivated whole cell vaccine or a locally made experimental product was carried out (single and × 50 doses) with or without booster
doses 4 months later. A further group received a single dose anally. All groups were
challenged 6 months after the primary administration with heavy mortalities in
groups apart from the anally and orally (× 50 dose) vaccinated fi sh; all fi sh in these
groups survived challenge. Thus, anal uptake gave full protection as did the very
dose administered orally, which suggested that there is signifi cant degradation (=
digestion) of the antigens in the stomach before reaching the intestine where it is
available to the immune system, and specifi cally the lymphocytes (Villumsen et al.
2014 ). Unfortunately, it must be emphasised that injection is only feasible for large
and/or valuable fi sh and not for the millions of fry/fi ngerlings which abound on the
typical fi sh farm. However, ERM vaccines have been used successfully on fi sh
farms when administered by bathing (Tebbit et al. 1981 ). In one investigation,
22959239 rainbow trout were vaccinated by a 90 s dip in a commercial vaccine
preparation. The results were very encouraging with signifi cantly reduced losses
attributable to ERM. In this particular trial, the vaccine effected an 84 % reduction
in mortalities due to ERM (Tebbit et al. 1981 ). Of additional benefi t, there was a
concomitant decrease in the use of medication by 77 %, and an increase in food
conversion of 13.7 %. Analogous fi ndings have been reported by Amend and
Eschenour ( 1980 ) and Newman and Majnarich ( 1982 ).
Optical projection tomography and immunohistochemistry was used to visualize
the uptake and processing of a whole cell vaccine by bath in rainbow trout.
Tomography showed that vaccine was initially taken up via secondary gill lamellae
from within 30 s of vaccination. At 5 to 30 min, vaccine cells were found on other
mucosal surfaces, namely the skin and olfactory bulb; at 3-h, the digestive tract was
fi lled with a complex of vaccine and mucus, remaining there for >24 h. At 24 h,
vaccine cells were located in the blood, spleen and trunk kidney (Ohtani et al. 2015 ).
Yersinia ruckeri