Animal: Charolais calf (Bos taurus), 12-days-old, male. The dam nor the calf received any BVD vaccinations.
Organ: Carcass as a whole (left) and sternal bone marrow (right)
Clinical history: Collapse and death, haematochezia noticed.
Main macroscopic findings: Diffuse, marked pallor of skeletal musculature and internal organs (anemic carcass), focally extensive mural acute haemorrhage in the dorsal rumen, and multifocal petechiae and ecchymoses in the omentum. There were also widespread petechiae and ecchymoses in the epicardium and thymus, suffusive haemorrhages in subcutaneous tissue/muscle fasciae surrounding joints and endocardium, and small and large intestines contained copious amounts of partially coagulated fresh blood (lesions not seen in this image).
Main histological features and diagnosis: The sternal bone marrow shows a diffuse and marked tri-lineage (lymphoid, erythroid and myeloid) hypocellularity and prominent pre-existing stromal cells, mature adipocytes and variably congested vasculature. Multifocal acute haemorrhages are observed (lower right corner). The morphological diagnosis in this case is a marked, severe, diffuse acute medullary aplasia.
Additional testing: BVDV PCR (thymus) – negative.
Disease: Bovine Idiopathic Pancytopenia
Comment: Based on macroscopic examination, a primary haemostatic disorder was suspected, and the histological examination of the bone marrow is diagnostic for a pancytopenia. A well described cause of pancytopenia in cattle in Europe is the Bovine Neonatal Pancytopenia (BNP), which has been linked to vaccination to the dams with a certain BVD vaccine (Pregsure® BVD). In this case the dam of this calf has never been vaccinated against BVD and there was no laboratorial evidence of natural BVDV infection in this calf, making the diagnosis of BNP unlikely. Therefore, the terminology ‘Bovine Idiopathic Pancytopenia’ instead is considered more appropriate by the contributors in this case. Interestingly, Chantillon et al. work describes an alloimmune mediated pancytopenia in 3 Belgian Blue suckler calves whose dams were not vaccinated against BVD either but were against other pathogens (bovine herpesvirus 1, parainfuenza-3 virus, bovine respiratory syncytial virus and bluetongue virus serotype 8). The initial antigenic trigger remains unknown, and a genetic component might be involved in the pathogenesis. In both cases, toxic causes were excluded on clinical grounds.
The rapid demise of this calf resulted from a marked enterorrhagia and systemic hemorrhaging leading to a hypovolemic shock originated from a medullary aplasia causing a pancytopenia.
Contributors: Bernat Marti Garcia, Sonja Jeckel, Pablo Diaz Santana, Alejandro Suárez-Bonnet, Pathology section, Pathobiology and Population Sciences, The Royal Veterinary College, United Kingdom
Bibliography:
Chantillon et al. Three cases of alloimmune mediated pancytopenia in calves resembling
bovine neonatal pancytopenia. BMC Vet Res. 2022 Jan 3;18(1):11. doi: 10.1186/s12917-021-
03117-z
Bell, Charlotte. Bleeding disorders in cattle. In Practice. 2011.