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Lungworms (Dictyocaulus viviparus) are nematodes that cause parasitic bronchitis (husk or hoose) in cattle. Lungworm outbreaks in cattle can result in production losses from reduced weight gain, lowered milk yield and death in young calves.1 Lungworms may be controlled by the use of a live attenuated lungworm vaccine capable of stimulating extended immunity.2
Lungworm L3 larvae, which are crucial for transmission of lungworm, are harvested from calf faeces, irradiated and used to produce vaccines.3 These are screened for a range of diseases, including Leptospira, as part of stringent quality control checks to prevent vaccine contamination. Leptospira borgpetersenii serovar hardjo type hardjo-bovis is the most common Leptospira serovar in cattle.4 Transmission occurs via contaminated urine, and symptoms of infection are frequently subclinical. Leptospira can cause delayed breeding, abortions or weak calves, causing significant economic loss.5 All calves and lungworm used for vaccine production are screened for Leptospira using ELISA, where sensitivity and specificity vary, making diagnosis difficult.6 7 In this study, the authors describe the development of a molecular assay which may be used for the detection of pathogenic Leptospira in lungworm preparations.
A real-time assay was designed for use on the MX3005p (Stratagene). The 16S rRNA Leptospira-specific primers used are as described previously,8 9 with the exception of the reverse primer …