Abstract. Mycotic infection was diagnosed in 6.8% of 6,858 cases of bovine abortion and stillbirth examined during a 9-year period. Aspergilli were associated with approximately 5% of all abortion cases and 71% of 446 cases that were cultured for fungi and diagnosed as mycotic abortion. Aspergillusfumigatus was the most frequent isolate (62%), followed by A. terreus (6.7%), Emericella (Aspergillus) nidulans (3.0%), A. flaws (2.9%), and E. rugulosus (< 1.0%). Zygomycetes (Absidia, Mortierella, Rhizomucor, Rhizopus) accounted for 21% of the cases. Pseudallescheria boydii and yeasts (Candida, Torulopsis) were each identified in 2% of the cases. Fungi that uncommonly cause infection accounted for 2% of the cases and included CurvuZaria geniculata, Exophilia jeanselmei, Hendersonula toruloidea, Lecythosphora hoffmannii, Talaromyces jlavus var. flavus (Penicillium vermiculatus), T. (Penicillium) thermophilus, and WangieZZa dermatitidis. About 10% of the mycotic cases were mixed fungal infections involving A. fumigatus (87%), A. flavus (12.5%), or E. nidulans (12.5%) coexisting with Absidia corymbifera (72%), Rhizomucor pusillus (4.3%), or Rhizopus arrhizus (4.3%). In each mixed infection, both septate and nonseptate hyphae were observed in placental tissues. Twelve percent of the mycotic abortion cases were diagnosed by histologic examination alone because isolation attempts were negative or only formalinpreserved tissues were available.Mycotic placentitis is a major worldwide cause of abortion in cattle, generally occurring in the third trimester of pregnancy. 10,23,30 The disease is sporadic and rarely affects more than 1 or 2 animals in a herd. 2,12,134 In the Northern Hemisphere, the incidence of mycotic abortion is highest between November and April, which corresponds to the approximate time when gravid cows are housed indoors and fed hay and/or ensilage. 1,6,24 The disease can also occur in beef cattle confined to pens and fed hay as well as those on pasture. Furthermore, cows confined to sheds and fed in cubicals are at greater risk than those fed loose hay in an "open" barn.3,4,49 Previous reports indicated that > 60% of cases are caused by uncomplicated infection with Aspergillus fumigatus; zygomycetes (Absida, Mortierella, Rhizomucor, Rhizopus) accounted for about 20% of cases, and the remaining 20% were caused by a wide range of opportunistic filamentous fungi and yeasts.
