 Leeches may attach to the vent or sometimes the inside of the pouch.A study of the parasites of the American white pelican found 75 different species, including tapeworms, flukes, flies, fleas, ticks, and nematodes.Many of these do little harm, but flies may be implicated in the death of nestlings, particularly if they are weak or unwell, and the soft tick "Ornithodoros capensis" sometimes causes adults to desert the nest.