Dicephalia in a Bovine
Background: Congenital defects consist of structural or functional abnormalities present at birth, which partially or globally affect the systems. Among the defects are the conjoined twins, a rare congenital anomaly caused by fusion of two monozygotic embryos which can be classified according to the different sites of union. The Siamese twins and embryonic duplication are represented by a progressive series of malformations, since partial duplication of part of the body to the training almost full two bodies. Siamese twins occur in humans and in several animal species. Dicephalia refers to two totally separate heads. The aim of this study was to report a case of dicephalia in a bovine fetus.
Case: A crossbred bovine fetus from a cow pregnant at. The animal was fixed by immersion in 10% formalin for sample collection. Muscles were dissected, with exposure of the bones of the right head, neck, forelimb, and hind limb. After dissection, the fetus was subjected to a preservation process by impregnation with glycerin. Next, internal organs were removed in bloc (from tongue to rectum) for evaluation of internal alterations. Additionally, radiographs of the spinal cord were performed to diagnose alterations by diagnostic imaging. Radiography revealed the presence of two skulls; two cervical spines, both with seven vertebrae; two thoracic spines, both with 13 vertebrae; and two lumbar spines, both with six vertebrae, however, fused at L4, i.e., connected in the final third part. Further information could not be obtained by the radiographs due to severe overlapping of structures, causing image subtraction. The findings are compatible with mineralized conjoined twin fetuses. After dissection, it was possible to see that each head exhibited normal development of tongue, trachea, and esophagus. In the thorax, there were two lungs with their typical lobes; however, there was atrophy of the lobes located medially. There was one pericardial sac surrounding two hearts. There was dextroposition of the aorta of the right heart, which would pass over the esophagus and trachea, and was connected to the aorta of the left heart in the cervical region. The ribs of the medial portion of the thorax were absent. The diaphragm had a central opening with protrusion of the diaphragmatic portion of the right lung lobe. The abdomen exhibited two rumens, one was blind-ended, and the other had normal prestomachs development, with connection to normal small and large intestines. There was a lung lobe close to the kidneys (pulmonary choristoma).
Discussion: The bovine fetus reported here can be classified as dicephalic, since it exhibited two well defined heads and only one body. That is different from diprosopia, which refers to the development of two faces in one skull. Such anomalies are rare and isolated in bovines, with few studies and information about them. The factors that trigger embryonic duplication are still unclear; however, the cause can be attributed to genetic defects in the germ cells, environmental influences, and heredity. The most important known causes are prenatal viral infection, ingestion of teratogens by the mother, vitamin A and folic acid deficiency, genetic factors, and/or a combination of these factors. No reports of rumen duplication in dicephalic bovines have been observed. Although the occurrence of such malformations is rare, they are relevant and cause economic losses to the farmers.
Keywords: siamese twins, malformations, radiography, ruminant.
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