Nipah virus infection among abattoir workers in Malaysia, 1998-1999

BACKGROUND: An outbreak of encephalitis primarily affecting pig farmers occurred during 1998-1999 in Malaysia and was linked to a new paramyxovirus, Nipah virus, which infected pigs, humans, dogs, and cats. Because five abattoir workers were also affected, a survey was conducted to assess the risk of Nipah infection among abattoir workers.

METHODS: Workers from all 143 registered abattoirs in 11 of 13 states in Malaysia were invited to participate in this cross-sectional study. Participants were interviewed to ascertain information on illness and activities performed at the abattoir. A serum sample was obtained to test for Nipah virus antibody.

RESULTS: Seven (1.6 %) of 435 abattoir workers who slaughtered pigs versus zero (0%) of 233 workers who slaughtered ruminants showed antibody to Nipah virus (P = 0.05). All antibody-positive workers were from abattoirs in the three states that reported outbreak cases among pig farmers. Workers in these three states were more likely than those in other states to have Nipah antibody (7/144 [4.86%] versus 0/291 [0%], P < 0.001) and report symptoms suggestive of Nipah disease in pigs admitted to the abattoirs (P = 0.001).

CONCLUSIONS: Nipah infection was not widespread among abattoir workers in Malaysia and was linked to exposure to pigs. Since it may be difficult to identify Nipah-infected pigs capable of transmitting virus by clinical symptoms, using personal protective equipment, conducting surveillance for Nipah infection on pig farms which supply abattoirs, and avoiding handling and processing of potentially infected pigs are presently the best strategies to prevent transmission of Nipah virus in abattoirs.