I don’t see any reason why it should be.
Please also see this response:
Question:
Is a dog’s saliva najis? If a dog or its saliva touches your clothes, are we allowed to pray in that condition?
Answer:
By Tariq Mahmood Hashmi
assalaam o alaykum
Generally it is against the etiquette the believers have developed to keep such things easily and pray in the same clothes. However, it does not mean that saliva of dog is najas and impure and one cannot pray if it touches one’s garments. The reason is that the dogs killing the prey for us undoubtedly inflict the prey with their teeth. It entails that the saliva is mixed with the meat. Still we are allowed to eat it.