Desenvolvimento do primeiro Imunobiológico contra ácaro hematófago Ornithonyssus bursa (Berlese, 1888) (Acari: Gamasida: Macronyssidae)

Abstract

Infestation by blood-sucking mites in poultry farming and egg production systems generates great economic loss. These aspects are mainly related to decrease in animal weight gain and reduced egg production, thus resulting in higher production costs, including expenses related to acaricides control. Therefore, blood-sucking mites have become a challenge for poultry production systems around the world and, consequently, require the search for new tools for their elimination or control in an effective and sustainable way. In this sense, vaccines are a viable option because they do not select resistant mite strains, do not contaminate the environment, do not pose a danger to animal and human health, and do not require waiting time before slaughtering the animal, in addition to being a long-term solution. Given this scenario, the objective of this study was to develop the first immunobiological against the hematophagous mite Ornithonyssus bursa, widely distributed throughout the country. A colony of O. bursa was obtained and maintained in chickens under laboratory conditions to extract biological material for vaccine formulation. Then, a clinical trial in birds was carried out to prove the concept with the immunizer, using three experimental groups: control, adjuvant + placebo and vaccine; n=4/group. The different inocula were administered to all groups, through three intramuscular applications, at intervals of 14 days (T0, T14 and T28). After 21 days of application of the third dose (TF), the animals were subjected to the challenge with the infestation of 20 mites/poultry in a feeding chamber fixed to the animal. During the clinical trial, the birds were clinically monitored and did not show local or systemic changes, with the formulation being considered harmless and safe. During the challenge, the mites fed for approximately 12 hours. Afterwards, they were collected and placed in 96-well flat- bottom plates individually to observe mortality, oviposition, fecundity, and larvae hatching. Observations were carried out for six days (0h, 24h, 48h, 72h, 96h, 120h). After analyzing the data obtained, it was found that the immunobiological agent against the mite O. bursa was able to demonstrate that it was: (i) harmless and safe; (ii) capable of inducing immunogenicity resulting in antigen-specific IgY levels; (iii) that it presents great potential due to interference in the biological cycle of the mites, resulting in a vaccine efficacy of 99.99%, interrupting the biological cycle of the mite. These results are compatible with the continuity of the study for the biotechnological improvement of the vaccine formulation.