PERPETUATION OF NEWCASTLE DISEASE VIRUS AT DIFFERENT TEMPERATURE IN NATURAL WATER BODIES

Abstract

Survivability of Newcastle Disease virus (NDV) in environment depends on several physiochemical factors. The study was conducted aiming to investigate the effect of pH, bi-carbonate and hardness of water on NDV and the thermo-stability of the virus at different temperature (22°C, 30° and 37°C) in laboratory condition. Five water samples were collected from 5 different upazilla of Chittagong and Dhaka districts. Each sample was divided into two group; non-treated (NT) and treated (T). Water samples of treated group were boiled at 100°C for 15 minutes and then filtered using bacteriological filter. Later pH, bi-carbonate and hardness of each sample of both groups were analyzed. Between two groups of samples there was no significant difference in terms of pH and bi-carbonate except hardness of water. Viral inoculums were prepared from previously characterized velogenic NDV and mixed with water sample and treated at 22°C, 30° and 37°C. Every six hours interval 2 ml exposure virus samples were removed up to 96 hours. To know the survival period of virus in each sample (both in NT and T), 0.1ml virus suspension was inoculated to embryonated chicken egg for different temperature, time and categories and incubated at 37°C where allantoic fluid was harvested after 48 hours of inoculation. Slide hemagglutination test was performed to know the presence of virus in allantoic fluid. Later plate hemagglutination (HA) test was done to know the virus titre. In every sample, virus survived longer period in treated than the non-treated water samples. Highest viral survival period was seen 84 hours for T4 sample and lowest was 66 hours for NT1, NT2, NT5 (except NT4) samples at 22°C and the HA titre was 22. At 30°C it was highest 78 hours for T4 and lowest 48 hours for NT, with HA titre 22. Finally in case of 37°C virus survived lowest 24 hours for NT3 and highest 48 hours for T4 sample where HA titre was 22. The study revealed that higher the environmental temperature lower the viral survival period. Again hardness of water is an important factor that affects the survival of NDV in water. So, survivability of NDV in environment depends on geographical distribution.