| Description |
The production of hemagglutination inhibition (HI) and neutralizing antibodies in garter snakes (Thamnophis elegans) following infection with Western equine encephalitis (WEE) virus was investigated. The duration and magnitude of antibody produced and the effect of temperature on antibody formation were studied. Duration of antibody titers indicated that HI antibody was detectable for at least 20 months and neutralizing antibody for at least 12 months following virus infection. Temperature was shown to have an effect on antibody synthesis in reptiles. Snakes which were challenged with WEE virus and maintained at 26 C produced neutralizing antibody titers between 1:1,000 and 1:10,000 within 45 days post challenge. Snakes which were challenged with WEE virus and maintained at 5 C produced antibody titers of either 1:10 or no detectable antibody in 110 days. Correlation existed between the titers of neutralizing antibody and circulating WEE virus present in snakes. HI antibody titers did not show correlation with the amount of circulating virus. Data presented indicated that the plaque reducation test was the most sensitive and reliable test for the detection of antibody in reptiles. Studies conducted on the relative susceptibility of gharter snakes to WEE virus indicated that snakes were sensitive to as few as 13 infectious virus particles. When snakes were infected with a small amount of virus (10 to 1,000 plaque forming unites), the virus recovered from the infected snakes had an altered cytopathic effect on chick embryo cells. The WEE virus strain used to infect these snakes produced a plaque size of 7 to 8 mm. However, the virus recovered from these animals produced a plaque size of 0.5 to 1.0 mm. Newly hatched chicks proved to be more sensitive in detecting the altered virus than did the plaque virus than did the plaque assay on chick embryo cells. Virus was detected in chicks 48 hours before it was detected on plaque assay. Studies o the replication of WEE virus in snake embryo cells were carried out. Growth curves of WEE virus in snake and chick embryo cells were similar. However, maximum virus titer was delayed in snake cells. This was probably due to temperature since snake embryo cells were maintained at 23 C, whereas, chick embryo cells were maintained at 37 C. Plaquing of WEE virus in snake embryo cells was demonstrated. Plaques were visible 72 hours after infection and reached maximum size in 96 hour post infection. Field studies of the incidence of WEE infections of snakes in Utah were conducted. Three separate study areas were investigated during 1967 and 1968. A significant difference in the levels of neutralizing antibody in these areas was detected. This was possibly due to the difference in resident bird populations. |
