Q: Are ticks and keds the same insect or are they different? Are both found on deer?
A: No, they are quite different, though both are found on deer and can be present at the same time. The tick we see in the UK (Ixodes ricinus) can be found on a variety of animals and birds and is most notorious for transmitting Lyme disease and tick-borne encephalitis, both of which can infect a range of species.
The deer ked (Lipoptena cervi) is a biting fly that is parasitic towards deer. Both ticks and keds will bite humans, and Lyme disease transmitted by ticks is a serious and debilitating condition.
Keds can be found with wings that they use to fly to their hosts. They then shed these before burrowing through the fur and feeding on their host. Ticks never have wings.
Keds can be fast-moving when disturbed; ticks are either attached to their hosts, in which case they are non-moving, or, if looking to latch on, relatively slow-moving.
Keds will bite humans, producing a painful result, but in general are considered less harmful than ticks.