Dictyocaulus viviparus

Dictyocaulus viviparus
Class	Secernentea
Order	Strongylida
Super-family	Trichostrongyloidea
Family	Dictyocaulidae
Genus	Dictyocaulus
Species	D. viviparus

Also known as:

Bovine lungworm Husk Hoose

Introduction

Dictyocaulus viviparus is a bovine lungworm (a member of the Trichostrongyloidea). They are found in the trachea and larger bronchi and are responsible for parasitic bronchitis. There has been an increase in the incidence of husk in recent years; first season calves are particularly affected, although yearling and adult cattle may also succumb to the disease. Lungworm is responsible for reduced weight-gain and deaths in calves and yearlings and lowered milk-yield in dairy cows. A closely-related species is also responsible for one of the most important diseases of farmed deer. The parasite is of welfare importance if clinically affected animals are left untreated.

Hosts

Cattle, buffalo, deer and camels.

Identification

The adults are white thread-like worms, often less than 8cm in length.

Life Cycle

The adult worms are found in the trachea and the bronchi. The female lays embryonated eggs, which are later coughed up and swallowed. The eggs hatch during the passage through the intestinal system. First stage larvae are passed in the faeces of the host. Development into L2, and later L3, occurs within the faeces on the pasture.

A new host is infected by ingestion of infective larvae whilst grazing. These infective larvae are passed through the alimentary tract, where they penetrate the wall of the intestine. The larvae then migrate to the lungs, via the lymphatic system, or the blood circulation. These ascend the respiratory tree, where they mature into adult lungworms.

The prepatent period is 3.5 weeks.