Histoplasmosis in Animals

Histoplasma capsulatum is a dimorphic fungus that is widely distributed in the tropical or subtropical areas of the world and infects numerous mammalian hosts. The outcome of the disease depends on many factors including the immune status of the host, the inoculum size and the virulence of the isolate. The single species H. capsulatum is supposed to include three distinct subspecies which do not share exactly the geographical distribution and which are responsible for variable clinical signs in different animal species. Histoplasma capsulatum var. capsulatum may be found in many regions all over the world; it is responsible for pulmonary and systemic infections with small-sized yeast-form cells in humans and many animal species, including companion animals. Histoplasma capsulatum var. duboisii is reported in Western and Central Africa and develops as large-sized yeasts with lymphadenopathy and dissemination to the skin and bones in primates. Histoplasma capsulatum var. farciminosum develops in the skin and the subcutaneous lymphatic system. In horses, the disease is called epizootic lymphangitis. It has been eradicated from large areas of the world but is still a major cause of morbidity and mortality in various countries particularly in Africa. The condition has a serious effect on the health and welfare of severely affected animals.