A 4-month-old intact, male, calf was found dead and submitted to the state diagnostic laboratory for necropsy. Per owner, he was acting weak for a while, but he seemed to gain strength after having hay, protein and sweet feed. A centrifugal fecal flotation revealed the following larva as well as high number of trichostrongyle type of eggs and Eimeria multiple species oocysts. Baermann test was also performed on the fecal sample and recovered the same larvae.
Dictyocaulus viviparus first-stage larva. Characteristic dark food granules are observed in the intestinal cells. Although D. filaria larvae have a small knob at the anterior end, D. viviparus larvae do not have it.
First-stage larvae are passed in the feces of the host, and infective third-stage larvae develop on pasture and are ingested while grazing.
Click on the following link to watch a video of a live D. viviparus adult worm and first-stage larvae!: www.youtube.com/watch?v=ZfitLJPpgjc
Reference: Zajac and Conboy, Veterinary Clinical Parasitology 8th edition.
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