Transboundary animal diseases (TADs) are a major threat to livestock producers. They are transmitted by direct infection or through vectors like tsetse flies or ticks. Protection through vaccination is the most cost-effective means of avoiding losses but for many TADs no vaccine exists.
Irradiation as a way to inactivate pathogens was already tested 40 years ago, but due to technical and scientific limitations, alternative inactivation methods were preferred. Since the advent of smaller irradiators and advances in irradiation technology, molecular science and immunology interest in this approach has grown again. It was clear from past experiments that complete inactivation by irradiation does not result in a solid immune protection against bacteria and parasites but that cutting the genetic material of these pathogens leads to a metabolically active but replication incompetent microorganism, which should be able to induce solid immunity. Thus, this CRP aimed at evaluating the existing and new technologies on an array of different pathogens to describe rational approaches and tools for the development of a new generation of irradiated vaccines.
As part of a consultants’ meeting, the Joint FAO/IAEA Animal Production and Health Sub Programme developed a research framework and invited Member State research laboratories to apply with their ideas relating to irradiated vaccine research. Nine research contracts and two research agreements were awarded to institutions with extensive experience in vaccine development for bacterial pathogens, helminth and protozoan parasites. The fundamental aims were to establish a dose of irradiation for attenuation for each pathogen, to determine indicator(s) of attenuation of the pathogens as a means of quality control and to evaluate such experimental vaccines in animals and define immune response qualifiers for protection.
This CRP was extremely successful, establishing the inactivation data and attenuation indicators for all six selected pathogens, as well as developing experimental irradiated vaccines for three pathogens that were successfully tested in animals. The most promising results were obtained with the ruminant stomach parasite Haemonchus contortus, which leads to severe production losses worldwide.? The oral application of irradiated H.c. larvae led to a 99.9% inhibition of oral infections, keeping the animals healthy and growing in the same manner as the uninfected control herd. Similar good results were obtained for the fish fungus Ichthyophthirius multifiliis (I.m.), which affects trout farming worldwide.
Irradiated fungus spores were absorbed into alginate particles and dispersed with fish feed to the fish. Challenging trout with I.m. later reduced the infection dramatically and no ulceration of the skin remained visible. Finally, Fasciola Gigantica is a zoonotic liver parasite, which leads to severe metabolic complications.? Here, too, the oral application of irradiated larvae impeded further infections and reduced growth of these parasites so that liver enzymes were no longer affected.
This CRP was strongly supported by the Animal Production and Health Laboratory in Seibersdorf. They worked in parallel on the irradiation of protozoal parasites and discovered several critical hot spots in the genome of these pathogens.
Following the successful conclusion of the CRP, a second CRP was immediately initiated to help with process development for such vaccines and to expand support in immunology to better characterise the protective mechanisms.
Researchers from Argentina, China, Ethiopia, Georgia, India, Iran, Sri Lanka, Sudan and Turkey participated in this CRP.
For more information, please see the CRP description: