The transfer of maternal IgE and other immunoglobulins specific for Trichostrongylus colubriformis larval excretory/secretory product to the neonatal lamb.

The transference of immunoglobulins from six New Zealand Romney ewes to their lambs was examined. Immunoglobulin levels were determined in ewe plasma, colostrum and lamb plasma shortly after birth and before the lambs fed, in lamb plasma 2 days after birth, and lamb plasma, ewe plasma and milk 30 days after parturition. Levels of total IgE, and IgE, IgG1, IgG2, IgM, and IgA with specificity for Trichostronglus colubriformis third stage larval secretory/excretory products (TcL3E/S) were determined. Mean levels of total IgE were three times higher in colostrum than in parturient ewe plasma while only trace amounts were detected in milk at 30 days after birth (107.7, 34.3, and 0.2U ml(-1), respectively, differences between means P< or =0.01). Mean total IgE in lamb plasma rose from being undetectable before suckling to levels comparable to those of the ewes by 2 days after birth (21.7U ml(-1)) and then declined to low levels by 30 days (0.4U ml(-1)). Total IgE levels in lamb plasma were significantly correlated with levels in ewe plasma and colostrum (r=0.91, P< or =0.01; r=0.96, P< or =0.003, respectively). The transference of TcL3E/S-specific IgE, IgG1 and IgA was substantial with mean levels of these antibodies in lamb plasma at 2 days comparable to that in parturient ewe plasma (absorbance levels in lamb plasma of 0.283, 0.537, and 0.334, respectively). Proportionally less maternal IgM and IgG2 appeared to be transferred to the lambs (absorbance of 0.112 and 0.081, respectively). Levels of TcL3E/S-specific IgE and IgG1 in lamb plasma at 2 days were significantly correlated with levels in parturient ewe plasma and colostrum (r=0.89 and 0.82, 0.85 and 0.96; all P< or =0.05, respectively). These results indicate that IgE is concentrated in ewe colostrum and that substantial amounts of maternal IgE are transferred to lambs via colostrum. Further, the results suggest that humoral immunity against gastro-intestinal nematode parasites and potentially other parasites in colostrum-fed lambs may approximate that of the ewe. The implications of the transference of humoral immunity through colostrum in ruminants for the passive protection and the development of active immunity against parasites remains to be fully explored.

Detection of homocytotropic antibody in lambs infested with the louse, Bovicola ovis, using a basophil histamine-release assay.

The utility of a basophil histamine-release assay using washed whole blood cells was examined in lambs and was used to determine if homocytotropic antibody with specificity for Bovicola ovis was produced in response to infestation with the louse. Maximal histamine release in the assay in response to Concanavalin A, anti-ovine IgE monoclonal antibody and, in sensitized lambs, to B. ovis antigen ranged from 18 to 48%. Histamine release from blood cells in response to B. ovis antigen was significantly higher in louse-infested lambs than in louse-naive lambs and was significantly correlated with louse and cockle scores. Passive cutaneous anaphylaxis (PCA) tests were negative with sera obtained from the lambs at the same time as blood for the basophil histamine-release assay. Serum histamine levels also were significantly higher in the louse-infested lambs than in louse-naive lambs and were significantly correlated with louse and cockle scores. The present results support a role for B. ovis-specific homocytotropic antibody in the development of cockle and indicate that the basophil histamine-release assay is more sensitive than the PCA test.

Detection of dermatophilosis and lice (Bovicola ovis) on flayed pelts and cockle on the skin of live lambs.

Pelts from lambs submitted to an abattoir were obtained at monthly intervals from December to August. One half of each freshly flayed pelt was examined for cockle, lice (Bovicolu ovis) and dermatophilosis, and the observations compared with defects attributable to cockle and dermatophilosis in the corresponding pickled half-pelts. Formalin-fixed samples from pelts identified as having cockle were examined microscopically. Cockle was not detected macroscopically in flayed half-pelts despite being obvious in 4% of the pelts after pickling. Lice were detected in 17% of the flayed half-pelts. Dermatophilosis occurred in 12% of flayed half-pelts, presenting most commonly as small lesions in the dorsal midline regions of the lambs. However, only 4% of pickled half-pelts showed defects attributable to dermatophilosis. In other groups of lambs, cockle was detected in vivo by examining the skin over the upper shoulder region after close shearing of the wool. This method of detection showed sensitivity of 80% and specificity of 100%. The results of this work provide a basis for the monitoring of dermatophilosis and cockle in live lambs.

Comparison of local and systemic responsiveness of lymphocytes in vitro to Bovicola ovis antigen and concanavalin A in B. ovis-infested and naive lambs.

The in vitro proliferation assay was used to determine lymphocyte responsiveness to soluble antigen of B. ovis and to Concanavalin A (Con A) in peripheral blood, spleen and various lymph nodes from B. ovis-infested and naive lambs. From March to July, an assay of monthly blood samples showed generally higher proliferative responses to antigen and Con A in B. ovis-infested than naive lambs. The proliferative response of cells from the skin-draining prescapular lymph nodes to B. ovis antigen was significantly higher in B. ovis-infested than naive lambs. Responses of cells from the medial iliac, mediastinal and mesenteric lymph nodes (which do not receive lymph from the skin) and spleen showed no significant differences between groups. Within the B. ovis-infested lambs, the response of cells from the prescapular lymph node was significantly higher than that from any other lymphoid organ examined. Responsiveness of the prescapular, medial iliac and mesenteric lymph node and spleen cells to Con A was not significantly different between groups, while mediastinal lymph node cells showed a significantly higher response in B. ovis-infested lambs. The data indicate that the antigen-specific cellular immune response is operating mainly locally, at the level of the skin and draining lymph nodes. Responses to the T cell mitogen Con A did not support non-specific immunodepression as reported in other ectoparasite/host systems.

Proliferative responses of lymphocytes in Bovicola ovis-infested lambs.

Proliferative responses of peripheral blood and prescapular lymph node lymphocytes from 8 B. ovis-infested and 8 naive lambs to concanavalin A (Con A) and soluble antigen of B. ovis were examined in vitro. The numbers of lice and the extent of cockle were also assessed on each lamb. Prescapular lymph node lymphocytes from infested lambs showed significantly higher responses to B. ovis antigen than those from naive lambs. Only a marginal difference was observed between infested and naive lambs in the response of lymphocytes from peripheral blood. Proliferative responses to Con A by prescapular lymph node or blood cells were not significantly different between groups. The results indicated a relationship between the intensity of louse infestation and the proliferative response of prescapular lymph node lymphocytes to B. ovis antigen.

Hypersensitivity skin testing of lambs infested with the biting louse (Bovicola ovis).

Abstract Cockle, a defect of lamb's pelts, has recently been shown to be associated with infestation of lambs with the louse Bovicoh ovis. The mechanisms by which infestation with the louse leads to cockle are not known, but immunological hypersensitivity has been suggested. The objectives of our work are to determine if lambs respond immunologically to lice and, if so, whether hypersensitivity occurs. Preliminary results are presented here.