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Maternal immunity in rabbits: The first line of defense against highly virulent RHDV2 strains

17 February 2026
Disease

In this interview, Massimiliano Baratelli, researcher at HIPRA, explains the role of passive immunity and why understanding its duration is essential for effective vaccination.

Why Is Maternal Immunity So Important for the Protection Against RHDV2? 

Maternal immunity in rabbits plays a crucial role in protecting young rabbit kits against highly pathogenic viruses such as Rabbit Haemorrhagic Disease (RHD), particularly  when we refer to the RHDV2 strains.

Unlike classical RHDV strains, RHDV2 can cause mortality in very young rabbits, even when dealing with low-virulence variants, if maternal immunity is absent.

As highlighted in the discussion:

“Unlike classical RHDV virus, RHDV2, regardless of whether it is a low or highly virulent variant, can cause mortality in young rabbits in the absence of this specific immunity.” 

This makes maternal immunity especially important during the early stages of life.

Moreover, it is well known that mortality in young rabbits begins to increase precisely when maternal immunity starts to decline:

“Several studies also demonstrate that mortality in young rabbits starts to rise right and precisely when this immunity starts to wane.” 

That’s why understanding how maternal immunity works — and more importantly, how long it lasts — is essential for optimizing vaccination strategies and preventing immunity gaps in young rabbits.

 

The Risk of the Immunity Gap

Maternal immunity do not last indefinitely. As they decrease over time, a critical period can emerge in which:

  • Maternal protection is no longer sufficient. This can occur for different reasons: the rabbit may not have enough maternal immunity, may lack the specific antibodies need to fight highly virulent strains, or may not receive any maternal immunity at all.

     

  • The rabbit’s own immune system is not yet fully competent. At birth, rabbits are physiologically immature: they are hairless, their eyes remain closed until around day 10 of life and their lymphoid organs are not fully developed. Lymphatic follicles begin to form at about two weeks of age. As the animal matures, the number of follicles increases, and noticeable postnatal development occurs in the distribution of lymphocyte subsets in the spleen, lymph nodes, and peripheral blood. Therefore, during the first few weeks of life, the immune system may not be competent enough to generate strong and long-lasting immunity.

     

  • Vaccination timing may not have been optimized. Considering both the maturation of the immune system and the maternal immunity present, determining the best moment for vaccination can be challenging. Some vaccines allow administration at 30 days of age. However, it is essential to pay close attention to which vaccine will be used and at what age it is indicated for administration.

 

Final thoughts

Understanding maternal immunity in rabbits is not just a scientific concept — it has direct practical consequences:

  • Reducing mortality caused by RHDV2
  • Improving and optimizing vaccination protocols in rabbits.
  • Strengthening the individual immunity against rabbit haemorrhagic disease
  • Preventing RHD outbreaks

To prevent the immunity gap in young rabbits, it is essential to understand exactly when maternal immunity decreases, so that vaccination can be administered at the optimal time.

However, vaccination is not the only tool to prevent RHD infection. Biosecurity measures should also be applied to reduce the risk of infection. In suspected cases, isolation, cleaning and disinfection are highly recommended, as this virus is highly resistant in the environment.

In the second part of this interview with Massimiliano Baratelli, we will focus on how long maternal immunity lasts and how it is transmitted — two critical elements in optimizing vaccination in rabbits.