Neospora, BVD and Beyond: Understanding Infectious Causes of Bovine Perinatal Mortality

When a full-term calf dies before birth, during calving or within the first 48 hours of life, infectious disease is often one of the potential causes considered during the investigation. Although infections account for a smaller proportion of bovine perinatal mortality cases than non-infectious causes such as dystocia and asphyxia, they remain among the most important diagnosable causes of loss and can have significant herd-level implications. 

Understanding which pathogens are most commonly associated with bovine perinatal mortality can help guide diagnostic testing, herd investigations and preventive strategies. 

Neospora Caninum: A Frequently Identified Pathogen 

Among infectious agents linked to bovine perinatal mortality, Neospora caninum is one of the most commonly detected pathogens^1,2. 

The parasite is particularly important because infection can occur during pregnancy through vertical transmission. The timing of fetal infection plays a major role in determining the outcome. When infection occurs later in gestation, the fetus may be capable of suppressing the infection and survive to term, sometimes appearing clinically normal at birth¹. 

Seropositive heifers have been reported to be at greater risk of experiencing perinatal losses, and co-infection with other pathogens may further increase risk¹. 

Because the organism has a predilection for nervous tissue, brain examination can be particularly valuable during diagnostic investigations¹. 

Bovine Viral Diarrhoea Virus (BVDV) 

Bovine Viral Diarrhoea Virus is another important infectious cause of bovine perinatal mortality. 

Although it is generally detected in a relatively small percentage of perinatal mortality cases, BVDV has the potential to cause significant outbreaks and has historically been associated with weak calf syndrome¹. 

Detection rates can vary considerably depending on the diagnostic method used. Antigen detection ELISA and RT-PCR are considered more effective than some traditional diagnostic approaches¹. 

One challenge during investigations is that the prevalence of persistently infected calves is often low, meaning large numbers of cases may need to be tested before the true impact of the virus becomes apparent¹. 

For this reason, a negative result in a small number of cases should not automatically exclude BVDV from herd-level considerations. 

Leptospira Species 

Leptospira hardjo remains an important infectious agent associated with bovine perinatal mortality. 

Detection rates vary considerably between regions, partly because herd prevalence and vaccination practices differ between countries^1,2. 

Diagnosis can be challenging because leptospires are difficult to culture. As a result, molecular techniques such as PCR are increasingly used in diagnostic investigations³. 

An additional challenge is that fetal immune responses can vary greatly. Some infected fetuses may develop strong antibody responses, while others may have little or no detectable serological evidence despite infection¹. 

Consequently, interpretation of diagnostic findings often requires consideration of multiple laboratory and pathological findings rather than reliance on a single test. 

Bacillus Licheniformis: An Often Overlooked Threat 

Bacillus licheniformis is an important bacterial pathogen linked to bovine perinatal mortality, particularly in certain management environments¹. 

The organism is often associated with housed cattle and poor-quality conserved forage, especially mouldy or spoiled feed¹. 

Infected fetuses may develop severe lesions, including necrotizing placentitis, bronchopneumonia, and pericarditis¹. 

Because exposure is strongly influenced by feeding management, identifying this pathogen should prompt evaluation of forage quality, feed storage practices and environmental hygiene within the herd. 

Other Infectious Agents Worth Considering 

Several additional pathogens have been linked to bovine perinatal mortality, although they are detected less frequently. 

These include: 

• Coxiella burnetii⁴ 

• Listeria monocytogenes⁵ 

• Salmonella species, particularly Salmonella Dublin¹ 

• Trueperella pyogenes¹ 

• Bovine herpes viruses¹ 

• Fungal infections associated with mouldy forage¹ 

While these pathogens may occur sporadically, they can still cause significant losses under favourable conditions. 

Turning Diagnosis Into Prevention 

Identifying an infectious cause is only the first step. The greater value often lies in preventing future losses. 

Several important infectious causes of bovine perinatal mortality can be reduced through practical herd management measures, including: 

• Effective vaccination programs for pathogens such as BVDV and Leptospira hardjo 

• Improved biosecurity to reduce infectious disease introduction and spread 

• Control strategies for Neospora caninum 

• Proper forage conservation and storage to reduce exposure to feed-associated pathogens 

• Careful monitoring of reproductive performance and perinatal losses within the herd 

Bovine perinatal mortality rarely has a single explanation. However, understanding the major infectious agents involved allows clinicians to move beyond individual cases and implement preventive strategies that improve herd reproductive outcomes over time. 

References 

1. Mee JF, Jawor P, Stefaniak T. Role of infection and immunity in bovine perinatal mortality: Part 1. Causes and current diagnostic approaches. Animals. 2021 Apr 6;11(4):1033. https://www.mdpi.com/2076-2615/11/4/1033 

2. Jawor P, Król D, Mee JF, Sołtysiak Z, Dzimira S, Larska M, Stefaniak T. Infection exposure, detection and causes of death in perinatal mortalities in Polish dairy herds. Theriogenology. 2017 Nov 1;103:130-6. https://t-stor.teagasc.ie/bitstreams/4be6e30c-e479-4287-b528-f2c24e0753e6/download 

3. Vidal S, Kegler K, Greub G, Aeby S, Borel N, Dagleish MP, Posthaus H, Perreten V, Rodriguez-Campos S. Neglected zoonotic agents in cattle abortion: tackling the difficult to grow bacteria. BMC veterinary research. 2017 Dec 2;13(1):373. https://link.springer.com/content/pdf/10.1186/s12917-017-1294-y.pdf 

4. Mock T, Mee JF, Dettwiler M, Rodriguez-Campos S, Hüsler J, Michel B, Häfliger IM, Drögemüller C, Bodmer M, Hirsbrunner G. Evaluation of an investigative model in dairy herds with high calf perinatal mortality rates in Switzerland. Theriogenology. 2020 May 1;148:48-59. https://t-stor.teagasc.ie/bitstreams/6dae9bce-19ef-4563-8f17-8752c5865439/download 

5. Whitman KJ, Bono JL, Clawson ML, Loy JD, Bosilevac JM, Arthur TM, Ondrak JD. Genomic-based identification of environmental and clinical Listeria monocytogenes strains associated with an abortion outbreak in beef heifers. BMC veterinary research. 2020 Feb 22;16(1):70. https://link.springer.com/content/pdf/10.1186/s12917-020-2276-z.pdf