After the outbreaks of Nipah encephalitis in Malaysia in 1998, DLD has conducted the surveillance program for Nipah encephalitis.
The target areas for surveillance were adjacent areas to Malaysia (Region 8 and 9), high density of pig population (Region 2 and 7) and high density of bats (Region 1). Sampling frame was designed with the purpose of detecting Nipah virus infection evidence with the 95 percent probability of detection if it is present in 5% of herds (farms or villages) in a stratum (5 regions). The sample size needed to give a 95% probability of detecting Nipah virus infection if the disease is present in 5% of herds in a stratum is to randomly select at least 60 herds. The number of samples collected in each herd was calculated by estimating the disease prevalence of the disease within farms (10%) with 95% confidence level. As a result, 60 pig farms were selected and 30 samples per farm were collected blood samples to detect antibody against Nipah viruses by ELISA.All samples were not found the antibody against Nipah virus.