The effect of parasitic infestation by Gasterophilus spp. on an undomesticated population of New Forest ponies
The study addresses problems associated with the infestation of of non-domesticated New Forest ponies by larvae of bot-flies (Gasterophilus spp), in the area of the New Forest Hampshire. The free living pony population is unique in Europe, is sufficiently large for meaningful statistical investigation and is accessible for sampling. Bot-flies are present in the area, and parasite the pony population extensively. There are no previous studies concerning the effects of such parasitism on a non-domesticated equine population. The extent to which the flying presence of adult flies affects pony behaviour is considered. Preferential host selection by ovipositing G. intestinalis is examined using data collected at the officially organised pony drifts and an association is made between the colour of the host animal and egg deposition. Data obtained from examination of pony cadavers are used to assess levels of larval infestation by Gasterophilus spp. and preferential host selection is again considered although no association is made between detected levels of larval infestation and sex, age or colour of host ponies. Tissue samples taken from the gastro-intestinal tracts of pony cadavers are examined for parasite damage and host tissue response detectable histologically. Conclusions are drawn concerning the overall effects of larval infestation on the organs of the digestive tract of the host animal. The possibility of establishing a direct connection between larval infestation by Gasterophilus spp. and the body condition of the host animal is investigated, but no association can be made, other factors precluding the establishment of a simple correlation. Finally, mechanisms are proposed for the development of a strategy for the elimination of the parasite from the indigenous New Forest population of native ponies.