Management of Snakebite and Research Management of Snakebite ...

Management of Snakebite and Research
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Local reactions following immunization in monkeys were: local swelling measuring 1
cm in diameter which lasted for 48 h was observed in (3/8), ulceration (1/8) after the first
injection and local swelling measuring 2 cm in diameter which lasted for 48 h was detected
in (1/8), regional lymph node enlargement (1/8) and abscess formation (1/8) after the
second. No reactions were observed in subsequent injections. Only one control showed
an induration of 1 cm on second injection.
Upset in general constitution symptoms was not observed in immunized monkeys
(Aye-Aye-Myint et al., 1998).
DISCUSSION
Formal toxoiding leads to decrease in toxicity far greater than that produced by gamma
irradiation (100 Krad) of venom (3-fold LD 50 , 1.75-fold MHD and 4.5-fold MND (Mandal
et al., 1993). The MCPI activity of the venom was not affected until four months of storage.
Further 44-folds decrease in the activity and two-fold reduction in haemorrhagic and
necrotic activities of the aged toxoid will further weaken the neutralizing properties of the
antivenom raised. The capillary permeability increasing activity is exclusively seen in Russell’s
viper (D.r. siamensis) bite cases of Myanmar and its presence signifies a bad prognosis.
Four to 22 folds reduction in biological activities of the toxoid at two months of storage
calls for use of either freshly prepared toxoid or toxoid stored up to two months in active
prophylactic immunization against Russell’s viper bite (Tun-Pe et al., 1995).
Peak antibody level observed 4-6 weeks after last injection in the present study (Aye-
Aye-Myint et al., 1998) was similar to that observed in our earlier study (Aye-Aye-Myint et
al., 1996) where intramuscular route of immunization was used. However antibody level
is short-lived and could not be maintained upto 24 wks after the first injection of the
toxoid. There was a slow induction of secondary response when booster doses were given
at 24 and 30 wks. Probably intramusclular route of administration induces a quicker
antibody response. Boosting at the decline of antibody level was found to induce a more
rapid response (Aye-Aye-Myint et al., 1996) than that given at a time where antibody level
is very low as in our present study.
The age of the toxoid has no influence on the pattern of antibody response. The
interval of boosting plays an important role in induction and maintenance of peak antibody
response. Frequent inoculation at weekly to two weekly intervals with venom or toxoid
have been used for active immunization in man against venom which yielded high level of
neutralizing antibody (Flowers, 1963, Weiner, 1960).
High resting antibody level is essential in immunized individual since immediate
neutralization of injected venom is required when a snake bites a man. It could be achieved
by boosting at six week intervals from eight week after the third injection of toxoid. The
feasibility and cost effectiveness of frequent injections at six week intervals to the risk
population needs to be studied.