Dictyocaulus in horses,donkeys and sheep
Dictyocaulus arnfieldi
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
- the
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.
