Diseases & Parasites
Like all animals, seals are susceptible to diseases and parasites. Diseases that may affect seals include tuberculosis, distemper and brucella. Under normal conditions, diseases will influence only a few seals.
Diseases may mutate into different forms over time and become more damaging. Also, if seals are already fighting the effects of starvation or an injury the seals can become more vulnerable to diseases.
It’s the same situation for parasites. Most seals carry some parasites, like hook worm or tape worms in their stomachs and mites in their fur. The parasites don’t cause them too much stress usually, but can become a major burden if the seal is in poor condition.