Evidence of a high incidence of subclinically affected calves in a herd of cattle with fatal cases of Bovine Neonatal Pancytopenia (BNP)

Abstract

BackgroundBovine Neonatal Pancytopenia (BNP) is a disease of calves characterised by bone marrow trilineage hypoplasia, mediated by ingestion of alloantibodies in colostrum. Suspected subclinical forms of BNP have been reported, suggesting that observed clinical cases may not represent the full extent of the disease. However to date there are no objective data available on the incidence of subclinical disease or its temporal distribution. This study aimed to 1) ascertain whether subclinical BNP occurs and, if so, to determine the incidence on an affected farm and 2) determine whether there is evidence of temporal clustering of BNP cases on this farm. To achieve these aims, haematological screening of calves born on the farm during one calving season was carried out, utilising blood samples collected at defined ages. These data were then analysed in comparison to data from both known BNP-free control animals and histopathologically confirmed BNP cases. An ordinal logistic regression model was used to create a composite haematology score to predict the probabilities of calves being normal, based on their haematology measurements at 10–14 days old.ResultsThis study revealed that 15% (21 of 139) of the clinically normal calves on this farm had profoundly abnormal haematology (<5% chance of being normal) and could be defined as affected by subclinical BNP. Together with clinical BNP cases, this gave the study farm a BNP incidence of 18%. Calves with BNP were found to be distributed throughout the calving period, with no clustering, and no significant differences in the date of birth of cases or subclinical cases were found compared to the rest of the calves. This study did not find any evidence of increased mortality or increased time from birth to sale in subclinical BNP calves but, as the study only involved a single farm and adverse effects may be determined by other inter-current diseases it remains possible that subclinical BNP has a detrimental impact on the health and productivity of calves under certain circumstances.ConclusionsSubclinical BNP was found to occur at a high incidence in a herd of cattle with fatal cases of BNP.

Haematopoietic depletion in vaccine-induced neonatal pancytopenia depends on both the titre and specificity of alloantibody and levels of MHC I expression

“…Those Pregsure vaccinated cows which produced alloantibody (50%) had an average PRA score of 29%, indicating an expected incidence of subclinical disease in calves of 15%. This is consistent with our recent finding that approximately 15% of calves born in a Pregsure-vaccinated herd exhibited abnormal haematological values [37].…”

The risks of using allogeneic cell lines for vaccine production: the example of Bovine Neonatal Pancytopenia

“…Together, this suggests that the occurrence of BNP depends on the quantity and specificity of the alloantibody dose absorbed by the calf, implying that BNP is not a dichotomous disease but that calves fall within a continuum from unaffected to severe BNP cases depending on the effective cognate alloantibody dose. This is consistent with the identification of milder subclinical forms of BNP, where neonatal calves develop profoundly abnormal hematology, including depressed lymphocyte and monocyte counts but no clinical signs of the condition [36,37]. Results from other studies indicate that farms affected by BNP have increased levels of calf morbidity attributable to causes other than BNP [4,28] providing a credible basis for the suggestion that subclinical BNP could have an impact on calf health and productivity in situations where animals are exposed to pathogen challenge.…”

Bovine Neonatal Pancytopenia – correlation between clinical symptoms, hematological parameters and lifespan

“…On most affected farms the incidence of clinical BNP is low, often with only one case per farm, rarely up to 10% (5,12,16). The clinical stage of the disease is characterized by severe internal and external bleedings.…”

“…The lethal end of the disease occurs within 7 days after first clinical abnormalities have been reported. In spite of high mortality rates of up to 90% (13), some cases of recovery and subclinical courses were recorded even with leucopenia and thrombocytopenia (5,10,16). Also differences in the extent of bone marrow lesions and hematological parameters were stated (2,5,15).…”