Cyclopia, cerebral aplasia and hydrocephalus in an equine foetus

Equine cyclopia

Abstract

Congenital anomalies of the central nervous system are quite common in domestic animals and can result from heredity or in utero exposure to teratogenic chemicals or to infectious agents. Among those is cyclopia, a congenital disease condition characterized by severe anomalies of the central nervous system and by striking skeletal malformations. Cyclopia is frequently observed in ruminants and pigs. In particular, epidemic outbreaks of cyclopia can occur in lambs in the western United States of America, due to the ingestion of Veratrum californicum during the early stage of pregnancy. On the other hand, cyclopia very rarely occurs in other animal species. The present report aims to describe the main pathological features of cyclopia, which has been recently observed in an equine foetus, aborted during the 8th month of gestation. At the external inspection, the foetus showed evident cranial and facial malformations, with a prominent maxillary brachygnathism. Remarkably, a single large median eye was present. After opening the cranial cavity, the brain hemispheres were totally absent, while a sketch of the cerebellum was still evident. The remaining part of the skeleton and all the internal organs appeared normally developed. Likewise, the foetal membranes were apparently healthy, prominent autolytic changes being only observed. Based on these pathological findings, a diagnosis of cyclopia associated with hydrocephalus and cerebral aplasia was made. To the best of our knowledge, this is the second case of equine cyclopia so far described worldwide, such malformation to be considered an extraordinary event in this animal species. The aetiology of sporadic cases of cyclopia remains often obscure; in human beings, it is heterogeneous with a high prevalence of chromosomal abnormalities, mainly trisomy 13. No data is currently available about the aetiology and pathogenesis of cyclopia in equids, incidental genetic defects representing the most plausible cause of such a rare disease condition.