Su di un caso di malformazione doppia (cefalotoracopagia) nel vitello

A case of double Malformation (Cephalothoracopagus) in a calf

Abstract

 The mechanism of the development of conjoined twins is not completely understood, and such far two main hypotheses can be considered: fission and fusion. The fission hypothesis proposes that conjoined twins arise from the incomplete division of a single fertilized ovum and thus they are the result of the failure of the separation of monozygotic twins; the fusion hypothesis proposes that conjoined twins arise from the re-fusion of two previously already separated monozygotic twins.

Various authors have described the teratogenic influence of genetics and environmental (viruses, plants, drugs) factors suspected of causing duplication defects.

The definition of the different aspects of this malformation is based on the localization of the conjunction: “craniopagus” is the conjunction of the heads, “cephalothoracopagus” of the entire upper part of the body, “thoracopagus” of the thorax, “omphalopagus” of the abdominal wall, “rachipagus” of the back, “pigopagus” of the sacral region, “ischiopagus” of the pelvic region. Parapagus is the term used to indicate a latero-lateral fusion.

The aim of this study is to present an interesting case of conjoined twins in bovine. Morphological aspects, etiopathogenetic and possible classification of the conjoined twinning are also discussed.

A stillborn female Holstein conjoined twins (twin 1 and twin 2) were referred for clinicopathological examination. External examination  showed a single head linked by a unique atlanto-occipital joint to two separated vertebral columns. An additional auricular pinna and a primitive stoma were also present. Upper part of the twins bodies were joined through the fusion of the thoracic walls resulting in a four-sided thorax with two sterna. Four forelimbs were linked to this thorax. The conjunction of the trunk extended until the umbilical region; caudally, two identical and symmetrical bodies presenting four hindlimbs, two tails, two ani and two vulve normally developed were noticed.

The dissection enabled to better understand the skeletal conformation. In particular, the left thoracic wall of twin 1 was linked to the right thoracic wall of twin 2 through one of the two sterna. The right  thoracic wall of twin 1 was linked to the left thoracic wall of twin 2 through the other sternum. 

Within the thorax, a single heart, two transposed unaerated lungs (situs inversus) and a severe megaesofagus, fused with the trachea, were present.

In the abdominal cavity a single but enlarged liver was present. Two umbilical veins, entering the body from a unique umbilical ring, divided before entering the liver. Each twin had its own rumen, reticulum, omasum and abomasum as well as its own jejunum, ileum, caecum, colon and rectum. The two mesojejunum were conjuncted. An ectopia of the spiral loops of the colon was also present in twin 2. Two spleens, two uteri, four kidneys and two bladders were also detected.

The lack of reliable information on the prevalence of such kind of malformation motivated the Authors to present this case. The reporting of malformed calves constitutes an indispensable step for improving the knowledge and recognize the etiology of these diseases.bovine, cephalothoracopagus, Octopus, conjoined twins, acardiac parasitic co-twin