Dot-ELISA based on recombinant Hypodermin C protein derived from
Przhevalskiana silenus for field diagnosis of goat warb
Abstract
Goat warble fly infestation (GWFI) is an economically important myiasis
caused by larvae of Przhevalskiana silenus (Diptera, Oestridae),
prevalent in countries of the Mediterranean Basin and Indian
subcontinent. GWFI is characterized by the presence of subcutaneous
warbles at the lumbar and sacral region of dorsum in the infested
animal. The early larval instars (L1 and L2) remain inaccessible to
physical detection due to their small size and subcutaneous presence
thus causing prolonged economic loss to animal productivity. The early
diagnostic intervention is needed during the disease monitoring and
prophylactic management for effective control of the disease. The
present study has developed an in-house dot-ELISA for the serodiagnosis
of GWFI based on recombinant Hypodermin C (rHyC) antigen of
Przhevalskiana silenus, expressed in E. coli. The purified
protein was used for optimizing dot-ELISA in a checkerboard titration
using goat warble fly infested serum as known positive. The optimized
conditions require 188 ng of protein/dot, 1:800 dilution of serum
sample, 1:4000 dilution of anti-goat IgG conjugate and 5% skim milk
powder in phosphate buffer saline as blocking buffer. The assay was
found to have a diagnostic sensitivity and specificity of 97.3% and
95.8%, respectively. The inter-rater reliability of dot ELISA with rHyC
indirect ELISA was found to be almost perfect with a Cohen’s kappa index
of 0.973. Further testing at ambient temperature (18
oC) and shorter incubation steps (30 min) supported
suitability of the assay for field diagnosis of GWFI. The rHyC protein
based Dot-ELISA was evaluated using random field serum samples suspected
for GWFI. The present study provides the first report of a sensitive and
specific dot-ELISA for early diagnosis of GWFI which is rapid and cost
effective. The test may provide an effective tool for sustainable
control of GWFI.