[Comparative evolution of blood antibodies in cattle infested with hypodermosis and treated with different...

Immunological response to hypodermosis is studied by a passive hemagglutination method in three groups of cattle naturally infested during the spring of 1972. In the autumn, one group was treated with fenthion and another with niclofolan, a drug generally used for distomatosis, but also efficient in hypodermosis and free from side-effects. The third group served as a control. Two kinds of immunological response are observed after use of the insecticide. In the group treated with fenthion, there is a rapid drop in antibodies during the 3 days following treatment; this increases for the next 2 months up to a very low level, which is stable for 3 months (fig. 3, 4, 5). During the same period, antibodies in the control group increase regularly to reach a maximum in April or May (fig. 1, 2). The immunological response of the host is closely related to the antigenic stimulation of the larvae. In the group treated with niclofolan, the slow drop in antibodies suggests that there is a parallel drop in the number of larvae during the month following treatment. A study of the other group shows that larvae are affected in the 24 hours following fenthion administration. This agent, as well as all organophosphorous compounds, are well-known to act efficiently on larvae and have anaphylactic-type side-effects on the host. The massive degradation of larvae should have induced an important antigenic reaction, but no increase in the antibodies of the host is observed; there is a even rapid drop in the number of larvae immediately after treatment. This fact is investigated further by experiments on guinea pig: the role of antigen-antibody complexes is studied by passive anaphylaxis. It appears that shock reactions, following use of organophosphorous insecticides, have a true-hyper-sensitivity origin, and are increased by the intrinsic toxicity of the first instar larvae.