The pathology of Psoroptes ovis infestation in cattle with a special emphasis on breed difference

In cattle, infestations with P. ovis are responsible for a severe dermatiti s. The disease is very common in some breeds of beef cattle whereas dairy c attle such as Frisian Holstein are considered as resistant. In order to inv estigate the factors responsible for this marked breed susceptibility, the immune response to P. ovis under experimental and field conditions has been studied using serology, lymphocyte transformation assay, intradermal tests and passive cutaneous anaphylaxis in susceptible Belgian White and Blue (B WB) and resistant Frisian Holstein (FH) cattle. The results of published st udies are reviewed in this paper; original data on specific hypersensitivit y reactions to P. ovisare also presented. The use of a sandwich ELISA allowed the detection of specific antibodies as early as 7 days post-infestation and very high titres were observed. There was a clear positive correlation between the antibody titre and the extent of lesions. This antibody response was associated with a marked in vitro l ymphocyte proliferation but there was no difference between susceptible and resistant cattle. The passive cutaneous anaphylaxis test revealed the pres ence of specific Ig E in actively infested animals irrespective of the bree d. Specific Ig E were detected fairly late during the course of an experime ntal infestation with P. ovis,The intradermal injection of P. cuniculi anti genic extract induced an immediate reaction in all animals including the co ntrols; in contrast, a delayed hypersensitivity reaction was observed in in fected BWB animals only. It is concluded that immunological as well as non- immunological factors may be responsible for the breed related susceptibili ty or resistance to P. ovis. (C)1999 Elsevier Science B.V. All rights reser ved.