Dictyocaulus in horses,donkeys and sheep
This nematode is seen in the trachea and bronchi of horses and donkeys. It
appears to be is a relatively benign infection in donkeys since it is rarely associated
with clinically obvious disease. In horses, because the worm rarely reaches
maturity, infections are usually not patent.
life cycle is similar to D. viviparus except for the following:
The stage passed in feces is an
egg containing an L1 which hatches soon after leaving the host.
The prepatent period ranges from 2 to
4 months.Patent infections may be seen in donkeys of all ages but in horses are usually
only seen in foals and yearlings.
Pathogenesis - The lung lesions seen in both horses and donkeys consists of
raised areas in the caudal lobes each of which contain lungworms inside a small bronchus
and a mucopurulent exudate. The bronchial epithelium is usually hyperplastic, has an
increased number of mucus cells and is infiltrated with lymphocytes.
Clinical signs - Infections in donkeys may produce mild clinical signs of harsh lung
sounds on auscultation and a slight increase in respiratory rate. In horses clinical signs
are uncommon in foals and yearlings and in adult horses may be present as a persistent
cough and increased respiratory rate.
Epidemiology - It is believed that horses acquire their infections from pastures
contaminated by donkeys with patent infections. Donkeys are usually infected first
as foals and through re-exposure remain infected throughout their lives.
Diagnosis - First stage larvae are easily recovered from feces of infected donkeys.
These larvae are similar to the L1s of D. viviparus but are slightly larger and
have a sharply pointed tail.