A survey on Dictyocaulus viviparus antibodies in bulk milk of dairy herds in Northern Germany.

Parasitic bronchitis caused by the bovine lungworm, Dictyocaulus viviparus, occurs worldwide in temperate areas. The parasite is found predominantly in calves and heifers, but dairy cattle can suffer from lungworms when they become infected for the first time or if they have lost immunity due to lack of exposure to lungworm larvae during the grazing season. The present study was performed to determine the D. viviparus bulk milk antibody prevalence in dairy herds in the East Frisian region of northwestern Germany, Lower Saxony, by analysing bulk milk samples collected in January (860 samples), September (866 samples) and November (860 samples) 2008, thereby representing 906 dairy farms. These samples were tested for antibodies against D. viviparus by a milk ELISA. This test detects patent infections only since it is based on recombinant major sperm protein as antigen. While in January 12.8% of dairy farms were positive for D. viviparus antibodies, the bulk milk samples collected in September and November revealed 6.9% and 6.6% positive dairy herds. From the 906 dairy farms included in the study, 191 (21.1%) tested positive at least once for antibodies against lungworm. From 810 dairy farms from which bulk milk samples were obtained during all three samplings, 146 (18.0%) farms were positive at one sampling date, 27 (3.3%) at two, and 4 (0.5%) on all three sampling dates. The majority of the farms represented in the study belonged to four districts of East Frisia, which showed no significant difference in the proportion of positive dairy farms.

Evaluation of a milk ELISA for the serodiagnosis of Dictyocaulus viviparus in dairy cows.

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against the bovine lungworm Dictyocaulus viviparus in milk was established. This test is based on recombinant major sperm protein (MSP) as the antigen and ELISA results are expressed as optical density ratio (ODR) values. The cut-off value of the milk ELISA was determined as the arithmetic mean of negative milk samples plus three standard deviations (SD). Specificity and sensitivity were 100% and 97.5%, respectively, using either milk or serum samples as positive control to calculate the ODR. Therefore, the presented recombinant antigen-based ELISA is suitable for routine veterinary diagnosis of exposure to bovine lungworms using milk samples instead of sera. To assess the course of antibody titres following lungworm infection, milk and serum samples from experimentally infected dairy cows were collected over a period of 23-30 weeks in three trials. The milk and serum antibody titre curves showed strong Pearson correlation coefficients in all three trials (Trial 1=0.85; Trials 2 and 3=0.93). In milk D. viviparus-specific antibodies exceeded the cut-off value 30-32 days post-infection (dpi) and remained above this value until day 112-138 post-infection (pi) with an overall detection period of 79-107 days. Treatment with eprinomectin during the pre-patent period prevented larval shedding and the antibody response was eliminated; treatment during patency similarly caused a cessation of larval shedding, but had no effect on the pattern of antibody responses compared to the untreated, infected controls.