title: Letter: Incidence and prevalence.
mesh_terms: D000820:Animal Diseases / Q000453:epidemiology*; D000818:Animals; D001733:Bites and Stings; D004443:Echinococcosis / Q000453:epidemiology / Q000662:veterinary*; D004485:Eczema / Q000662:veterinary*; D004813:Epidemiology; D006734:Horse Diseases / Q000453:epidemiology; D006736:Horses; D012621:Seasons; D012871:Skin Diseases / Q000453:epidemiology / Q000662:veterinary; D009626:Terminology as Topic; D006113:United Kingdom; D014887:Weather