Written by PJ, from VELD FIRST, KAROO DIREK, DIE VEEPOS and KAROO-KALAHARI VEEVOER & LOGISTIEK
Vaccination against foot-and-mouth disease (FMD) can cause temporary fever and inflammatory responses that lead to pregnancy loss or stillbirth, particularly when administered during early gestation.
Emerging mRNA FMD vaccines
- Development: recent advancements include synthetic mRNA vaccines for FMD developed through international collaborations, including institutions such as such as New South Wales and Tiba Biotech.
- Safety Profile: while novel mRNA platforms aim to bypass the biosafety risks of cultivating live or inactivated viruses in high-containment facilities, any systemic febrile (fever) response or acute-phase inflammatory reaction from livestock
vaccines carries a baseline risk of thermal stress to pregnant animals.
FMD vaccination and reproductive risks
- Fever-induced loss: rumino-reticular temperature spikes following FMD vaccination can trigger early embryonic loss,
miscarriages, premature birth, and stillbirths. - Gestational vulnerability: studies show that traditional FMD inoculations given before 45traditional FMD inoculations given before 45 days of gestation significantly increase pregnancy failure rates compared to non-vaccinated cattle, while administration later in pregnancy (after 45–90 days) generally shows no statistical difference in failure rates.
How does the mRNA vaccine for FMD cause stillbirths in cattle
As stated above, the mRNA Foot-and-Mouth Disease (FMD) vaccine can cause stillbirths in cattle as a result of severe, systemic inflammatory and febrile responses triggered by the animal’s own immune system. The underlying biological mechanisms that link the mRNA platform to reproductive failure in cattle include:
1. Severe hyperthermia (fever)
- Thermal stress: mRNA vaccines are designed to elicit a highly robust immune response. This reaction routinely triggers a spike in rumino-reticular and rectal temperatures.
- Foetal lethality: cattle are highly sensitive to heat stress. A post-vaccination fever exceeding 39.5°C disrupts cellular function in the placenta and is directly lethal to a developing embryo or foetus
2. Acute-Phase Inflammatory Cascade
- Cytokine Storm: the introduction of mRNA encapsulated in lipid nanoparticles causes an immediate release of pro-inflammatory
cytokines. - Haptoglobin surge: studies show a massive post-vaccination increase in acute-phase proteins like haptoglobin. This extreme
systemic inflammation compromises gestational maintenance.
3. Placental vascular disruption
- Prostaglandin Release: systemic inflammation stimulates the release of Prostaglandin F2-alpha
- Luteolysis: in cattle, Prostaglandin F2-alpha lyses the corpus luteum, which cuts off the progesterone required to sustain a
pregnancy, triggering immediate abortion or stillbirth. - Thrombosis: severe immune reactions can cause localized clotting or inflammation in the uterine lining, restricting oxygen and nutrient delivery across the placenta.
4. Vulnerability by gestational stage
- Early gestation risk: the risk is heavily concentrated in the first 45 days of pregnancy, during the critical window of maternal recognition and early embryonic
development. - Late gestation impact: while less frequent, an intense immune-mediated shock or high fever late in pregnancy can still result in premature labour or a stillborn calf.
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References for this paper include National Institutes of Health, MDPI, Journal of Veterinary Science, PMC, Science Direct, Friedrich-Loeffler Institute
- https://pubmed.ncbi.nlm.nih.gov/26812345/
- https://www.mdpi.com/2076-393X/9/11/1227
- https://vetsci.org/DOIx.php?id=10.4142/jvs.25267
- https://pmc.ncbi.nlm.nih.gov/articles/PMC8633299/
- https://www.fli.de/en/news/short-messages/short-message/the-first-mrna-vaccine-against-foot-and-mouth-disease-successfully-tested-in-cattle-by-fli-as-part-of-an-international-collaboration/
- https://www.sciencedirect.com/science/article/pii/S0264410X26006493
Contact PJ at 072 073 6805
