Tuberculosis control in Eurasian wild boar by parenteral vaccination with heat-inactivated M. bovis

by Mariana Boadella (Sabiotec. Camino de Moledores s/n. Ciudad Real. Spain), Christian Gortázar (SaBio – IREC. Ronda de Toledo, 12. Ciudad Real. Spain), Oscar Rodriquez (Rabat, Morocco, Iker A. Sevilla Neiker. Parque Tecnologico de Bizkaia, Derio Spain), Jacob Mwanzia (Abu Dhabi, United Arab Emirates)

in WDA-AME Newsletter 2021, Vol.5, issue 1

Tuberculosis (TB) caused by members of the Mycobacterium tuberculosis complex (MTC) is a major public and animal health challenge in Africa. However, test and cull schemes are usually not viable due to economic constraints. Hence, vaccination emerges as an alternative for the control of zoonotic TB in Africa.

Heat-inactivated vaccines are a well-established tool for the control of bacterial infections in livestock, including mycobacterial infections (Bastida and Juste 2011). Domestic ruminants are often vaccinated against Mycobacterium avium paratuberculosis (MAP) - the causal agent of Johne’s disease (Ott et al. 1999). Heat- inactivated MAP vaccinated goats and cattle showed cross-protection against MTC as compared to unvaccinated controls (Pérez-de-Val et al. 2012; Juste et al. 2014).

Heat-inactivated M. bovis (inactivated vaccine, IV) protects Eurasian wild boar and pigs (Sus scrofa) from generalized TB, both orally and parenterally, and both in the laboratory (Beltrán-Beck et al. 2014a) and in the field (Díez-Delgado et al. 2017, 2018). Being inactivated, this vaccine has the advantage of having no safety limitations as compared to live vaccines (Beltrán-Beck et al. 2014b).

In 2013, we started an ambitious wild boar TB control program in a wild boar farm by means of parenteral vaccination with IV. Postmortem inspection and sampling were performed on hunter-harvested wild boar (n=1771). The study site is dedicated to recreational wild boar hunting and has a breeding facility for re- stocking the hunting area. In the first three years (2013-2015), only part of the stock (two thirds) was vaccinated in order to maintain unvaccinated controls for study purposes. Since then (2016-2019) all new stock was vaccinated. Figure 1 shows the effects of vaccination on apparent TB prevalence as assessed by the presence of TB-compatible lesions. Since 2018, six years after starting the vaccination program, the farm remains TB-free.

We are interested in exploring similar approaches in other settings and even in other host species, since preliminary results in ruminants also suggest some protection conferred by heat-inactivated vaccines (e.g. in goats and in red deer, Cervus elaphus; (Thomas et al. 2017, Roy et al. 2018).

References

Bastida F, Juste RA (2011). Paratuberculosis control: A review with a focus on vaccination. J Immune Based Ther Vaccines 9: 8.

Beltrán-Beck B, De La Fuente J, (…..), Juste R, Gortazar C (2014). Oral vaccination with heat inactivated Mycobacterium bovis activates the complement system to protect against tuberculosis. PLoS One 9: e98048.

Beltrán-Beck B, Romero B, (…..), Gortázar C, Aranaz A (2014). Assessment of an oral mycobacterium bovis BCG vaccine and an inactivated M. bovis preparation for wild boar in terms of adverse reactions, vaccine strain survival, and uptake by nontarget species. Clin Vaccine Immunol 21: 12-20.

Diez-Delgado I, Rodriguez O, (…..), Dominguez L, Gortazar C (2017). Parenteral vaccination with heat-Inactivated Mycobacterium bovis reduces the prevalence of tuberculosis-compatible lesions in farmed wild boar. Transbound Emerg Dis 64: e18-e21.

Diez-Delgado I, Sevilla I, (…..), Aranaz A, Gortazar C (2018). Impact of piglet oral vaccination against tuberculosis in endemic free-ranging wild boar populations. Prev Vet Med 155: 11-20.

Juste RA (2014). Paratuberculosis vaccination confers partial protection against M. bovis infection in cattle. In Proceedings of the VI International M. bovis conference. Cardiff, UK.

Ott SL, Wells SJ, Wagner BA (1999). Herd-level economic losses associated with Johne’s disease on US dairy operations. Prev Vet Med 40: 179-92.

Roy A, Risalde MA, Bezos J, (…) Domínguez L (2018). Response of goats to intramuscular vaccination with heat- killed Mycobacterium bovis and natural challenge. Comparative Immunology, Microbiology and Infectious Diseases 60 (2018) 28–34

Thomas, J., Risalde, M.Á., Serrano, M., (...), Gortázar, C. (2017). The response of red deer to oral administration of heat-inactivated Mycobacterium bovis and challenge with a field strain. Veterinary Microbiology 208: 195-202.