Congenital goiter in an alpaca (Vicugna pacos) fetus concomitant with brain pathology in the dam: composing the puzzle

This study describes the congenital goiter in an alpaca (Vicugna pacos) fetus aborted in November 2021 with the clinical and pathological findings in the dam that was found dead on the farm three weeks after a miscarriage. The dam was a black coat alpaca bred in the Netherlands, imported in Italy in January 2021, and housed in a farm of central Italy for breeding purposes. Signalment and clinical data on dam and fetus were collected from the farmer and referring veterinarian. Necropsies and histopathological investigations on mother and conceptus were conducted at the Department of Veterinary Medicine, University of Perugia. The fetus was aborted at the 5th gestational month and at necropsy revealed bilateral thyroid gland enlargement. Microscopically the thyroid gland presented follicular cell hypertrophy and hyperplasia, follicles greatly varying in size, with macrofollicles lined by attenuated to atrophic epithelium and distended by eosinophilic colloid (colloid goiter). The dam presented a history of anorexia, wasting, dullness, severe weakness, incoordination, recurrent seizures, and, most recently, abortion. At necropsy, a cerebral focal loss of substance was found at the right parietal cortex, which histologically corresponded to laminar ischemic neuronal necrosis; most importantly, histological examination of cerebellum showed multifocal necrosis of the Purkinje cells associated with severe depletion of the granular layer neurons. These cerebellar findings in the dam combined with goiter in the conceptus suggest organomercurial poisoning as the likely cause of abortion followed by mother’s death. Mercury poisoning is hypothesized as the possible link between mother’s and fetus’ lesions.