Pulmonary parasites

University of Nottingham

• Focus on Pulmonary Parasites

• Lecturer: Hany Elsheikha

Learning Objectives

• Students should be able to:

  • Discuss the life cycle of common species of lungworms.

  • Discuss the diagnosis of lungworm disease.

  • Recognize differences between lungworm disease (e.g. husk) and respiratory signs caused by nematode larvae through lungs (e.g. ascariasis).

Taxonomy of Lungworms

Phylum: Nemathelminths

• Broad taxonomy: Nematoda

• Subclasses:

  • Adenophera (Aphasmidea)

  • Secernentea (Phasmidea)

• Important Classes and Orders:

  • Class: Secernentea

    • Orders: Strongylida, Ascaridida, Rhabditida, Oxyurida, Spirurida, Metastrongyloidea, Ascaridoidea, Trichostrongyloidea, Rhabditoidea, Oxyuroidea, Filarioidea

  • True lungworms: Reside in lungs; Non-true lungworms reside elsewhere.

Class Nematoda (Roundworms)

Superfamilies

• Trichostrongyloidea

• Metastrongyloidea

Families of True Lungworms:

• Dictyocaulidae

  • Dictyocaulus viviparus (Cattle, deer)

  • Dictyocaulus filaria (Sheep, goats)

  • Dictyocaulus arnfieldi (Donkeys, horses)

• Protostrongylidae

  • Protostrongylus rufescens (I.H.)

  • Mullerius capilaris (Sheep, goats)

• Metastrongylidae

  • Metastrongylus apri (I.H.) (Swine)

Dictyocaulus spp. Overview

• Dictyocaulus viviparus (cattle, camelids, deer)

• Dictyocaulus filaria (sheep, goats)

• Dictyocaulus arnfieldi (donkeys, horses)

• Clinical effects include:

  • Parasitic bronchitis leading to "husk."

  • Possible development of parasitic pneumonia due to larvae deposition.

  • Morphology: Male up to 5 cm, female up to 8 cm with unique spicule.

Life Cycle of Dictyocaulus viviparus

• Lifespan: Direct life cycle with a prepatent period of 3 weeks.

• Found on permanent pastures throughout the UK and Europe.

• Develops rapid immunity in cattle; hypobiosis seen in larvae during adverse conditions.

Pathology and Detection of D. viviparus

• Clinical pathology includes:

  • Eosinophilia and adult worm presence in bronchi leading to emphysema and pneumonia.

  • Larval detection: Baermann apparatus for L1 in faeces, alongside ELISA tests for antibodies.

Clinical Signs of D. viviparus

• Mild Infection: Intermittent cough on exercise.

• Moderate Infection: Frequent cough, may present with mild respiratory rate.

• Severe Infection: Deep cough, high respiratory rate (over 80 breaths/min), signs of respiratory distress.

Outbreaks of Lungworms

• Factors for increased lungworm incidents include:

  • Reliance on anthelmintics over vaccinations.

  • Climate change fostering persistence of L3 larvae.

• Huskvac Vaccine: Introduced in 1965; uses irradiated L3 larvae for immune response.

Dictyocaulus arnfieldi (Horse Lungworm)

• Infections often come from pasture shared with donkeys. Treatment includes Ivermectin and Fenbendazole.

• Adult worms located in bronchi, with a different pre-patent period compared to D. viviparus.

Companion Animals and Lungworms

• Superfamily: Metastrongyloidea covers most canine and feline lungworms.

  • Notable species include:

    • Angiostrongylus vasorum (Dogs), demographic expansion noted.

    • Oslerus osleri (Dogs).

    • Aelurostrongylus abstrusus (Cats).

Lifecycle of Angiostrongylus vasorum

• Dog ingests intermediate hosts (slugs/snails); lifecycle includes indirect development affecting pulmonary health and resulting in clinicopathologic signs.

• Diagnosis can be conducted through imaging and detecting larvae in faeces or BAL fluid.

Larva Migrans in Humans

• Types:

  • Visceral larva migrans: through organs (Toxocara spp.).

  • Ocular larva migrans: through the eye.

  • Cutaneous larva migrans: through skin (hookworms).

Suggested Readings

• Various publications by notable authors discussing lungworm prevalence, pathology, and preventative measures.