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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.



Parásitos y enfermedades parasitarias de los animales domésticos
Dr. Colin Johnstone (autor principal)
Derechos de copia © Universidad de Pennsylvania