Horses suffer from a range of parasitic problems. Common parasites found on horses and ponies are biting and sucking lice, mites, midges, ticks, mosquitos, black flies and bot fly.
If left untreated parasites can cause serious health problems.
Bot eggs are the larvae of the adult bot fly. The adult flies lay eggs on the legs and around the chest and are visible as tiny yellow dots in late summer. As the eggs hatch, an itchy substance is distributed over the skin, encouraging the horse to lick and inadvertently ingest the larvae. Once in the stomach the larvae pupate and are passed in the faeces and hatched to complete the cycle.
Ticks tend to be a country problem, where infestations seem to be more of a problem in rough grazing, woodland areas.. Ticks have a very complicated life-cycle and so are quite difficult to get rid of. Adult female ticks lay groups of eggs, which hatch to form a colony of young ticks. These attach themselves to grass stems where they wait for a host to walk by. Ticks gorge themselves on the blood and bury their heads into the animal's skin taking on the appearance of a wart on the skin. Never be tempted to pick them off, as this can be very painful and often the head will come away and stay embedded in the skin.
These small wingless insects are present all year round and especially noticeable amongst housed animals. Because of its contagious nature, louse infestation spreads most rapidly when animals are in close contact. Female lice attach their eggs (nits) to the hair fibres and take about ten days to hatch into nymphs and a further two to three weeks before they develop into adults. It is just possible to see adult lice with the naked eye. By carefully parting the hair, movement can normally be seen at the base of the hair. They are grey/brownish in colour and the size of a pinhead. Biting lice are by far the most common, they feed on debris on the surface of the skin and their scavenging produces intense irritation causing crusty scurfy areas that the animal will bite and scratch in an effort to alleviate their discomfort. Sucking Lice can cause severe anaemia and infested animals can rapidly lose weight and become prone to other illnesses.
Flea eggs a mostly laid on the floor or bedding and very few on the body of the host from which they fall. Appearing as white specks they hatch when conditions of temperature and moisture are favourable, ranging from around two days in the summer to approx 12 days. When fully grown the larvae spins a cocoon, in which the pupa develops, but they can remain alive in this cocoon for up to 12 months, before hatching.
Although infestation is more common in small pets; horses and cattle are occasionally infected. They cause severe irritation and can also cause anaemia in young and debilitated animals. All bedding must be destroyed and all floors, cracks throoughly cleaned to stop re-infestation.
Animals may suffer from the allergic reaction to the saliva of the biting midge - a condition known medically as 'Sweet Itch.'
Harvest Mite, bracken bugs and harvest bugs are names given to the larvae of the mite - Trombicula autumnalis. The first active stage in the lifecycle is the six-legged larvae which attacks animals. They are orange/yellow in colour and around 0.2mm long and just visible to the naked eye. The larvae are present on vegetation and are active during the day, especially in dry, sunny condition through the summer until the end of September. They tend to swarm and congregate around any warm-blooded animal in areas where there is little hair and the skin is quite thin.
The larvae feeds by thrusting its small hooked fangs into the skin and injects a fluid which breaks down the cells underlying the horny layers of the skin. The larvae then sucks this liquid feed back into its digestive system. It continues to do this for three to four days over the same site until it increases in size three or four times.
To complete the lifecycle the larvae then drop to the ground burrow into the soil where they remain for approx six weeks until they become an eight legged nymph and then an adult. The fully grown adult feeds on insects and plants, lays its eggs during the spring and summer hatching into the six legged larvae (harvest mites) to start the cycle all over again.
The fluid injected into the skin causes skin reactions to sensitively skinned animals causing irritation and discomfort.
Living away from the animal: Lice and mites can live off the animal for up to 40 weeks and so it is very important to treat areas and bedding separately to avoid re-infestation.
From Horse Active