Pulmonary Parasites

Question 1

Provide an overview of the taxonomy off Dictyocaulidae

Answer 1

Phylum:
Nemathelminths
Class:
Nematoda
Sub-Class:
Secernentea
Order:
Strongyloides
Super Family:
Trichostrongyloidea

Question 2

Outline the three types of Dictyocaulus species

Answer 2

D. Viviparus
D. Filaria
D Arnfeldi

Question 3

Outline the life cycle of D. Viviparus

Answer 3

Eggs laid by females hatch in the airways and first stage larvae (L1) pass in the faeces

Develope into third stage larvae (L3) whilst in the environment

Infection occurs when cattle consume L3

Larvae migrate in the vasculature to the lungs, leave the branches of the pulmonary artery and migrate through the lung parenchyma to the airways, where they remain as adults

Question 4

Outline the pathology of D. Viviparus

Answer 4

Usually seen in cattle on permanent pastures used for seasonal grazing in the UK and Europe, but widespread throughout world

Cattle exposed to D. viviparus develop rapid immunity

Hypobiosis (dormancy) of larval stage has been demonstrated in adult cattle

L3 larvae may overwinter on pasture in enough numbers to cause disease the following spring but conditions need to be favourable

Question 5

List the clinical signs of D. Viviparus

Answer 5

Coughing

Respiratory rate

Lung auscultation

Other signs such as Respiratory distress (dyspnoea), gasping for air with head and neck outstretched. Salivation, loss of appetite, fever in severe infection

Question 6

Outline the diagnosis process for D. Viviparus

Answer 6

Baermann apparatus is used to detect L1 larvae in faeces

ELISA test (antibodies)

Post mortem -adults in lungs

Question 7

Outline what treatments are available for D. Viviparus

Answer 7

Anthelmintic treatment
Albendazole
Doramectin
Ivermectin
Moxidectin
Levamisole

Huskvac Vaccine
- Irradiated L3 larvae (2 oral doses given to calves in winter before turn out)

• Protective response against L4 (therefore response protects against the
  development of adults which produce eggs)

Question 8

What is Husk?

Answer 8

Parasites which live in the trachea and bronchi

Question 9

Outline the life cycle of D. Arnfeldi

Answer 9

Larvated eggs, and very rarely first-stage larvae, pass in the feces.

In the environment, the eggs hatch and the larvae released undergo two moults to the infective third stage.

Infection of the donkey is by ingestion of the infective larvae.

Larval migration in donkeys follows the same route a D. viviparus in cattle.

The pre-patent period of D. arnfieldi in donkeys is approximately 12 to 14 weeks. In horses, the infection very rarely becomes patent.

Question 10

List the clinical signs of D. Arnfieldi

Answer 10

In donkeys, D. arnfieldi is sometimes associated with clinical signs, although heavy infections may lead to coughing and respiratory distress. In horses, the pre-adult larvae, particularly if present in large numbers, can result in a range of respiratory symptoms, including coughing.

Question 11

Outline the diagnostic process for D. Arnifieldi

Answer 11

Bronchoalveolar/tracheal wash may reveal worms and large number of eosinophils

Question 12

Outline the treatments available for D. Arnfieldi

Answer 12

Ivermectin (eqvalan)
Fenbendazole (panacur)
Moxidectin has also been used

Question 13

Outline the taxonomy of lungworm in companion animals

Answer 13

Phylum:
Nemathelminths
Class:
Nematoda
Sub-Class:
Secernentea
Order:
Strongyloides
Super Family:
Metastrongyloidea

Question 14

List the common types of lungworm species and which animals they infect

Answer 14

Angiostrongylus vasorum - Dog
Aelurostrongylus abstrusus - Cat
Muellerius Capillaries
Protostrongylus
- Sheep and Goats
Metastrongylus - Swine

Question 15

Outline the life cycle of Angiostrongylus vasorum

Answer 15

Undergoes an indirect life cycle with gastropod (terrestrial snails/slugs) intermediate hosts.

Adult parasites live in the right ventricle and pulmonary arteries of the definitive host (canid).

They produce eggs which develop into first stage larvae which are coughed up, swallowed, and passed in faeces of the canid definitive host.

First-stage larvae from faeces enter gastropod intermediate hosts where they develop to infective third-stage larvae (L3).

Canid definitive hosts become infected when they consume a gastropod containing infective L3, or L3 that have emerged spontaneously from the gastropods.

Frogs and birds may serve as paratenic hosts, but their role in transmission is not clear.

The pre-patent period from ingestion of an L3 to production of L1 in faeces is 6-8 weeks.

Question 16

Outline the pathology of Angiostrongylus vasorum

Answer 16

Endemic in some areas of the UK
Cornwall, south wales, south east

Generally considered to be increasing

Increasingly widespread across country
Thought to be due to increased fox urbanisation

Adult worms in pulmonary arteries and larvae breaking out of capillaries into alveoli can cause respiratory problems.

Adults and larvae can block vessels, impeding circulation and leading to right heart failure.

Infection with the parasite has also been linked to disseminated intravascular coagulation and coagulopathies.

Rarely, larvae have been reported in the central nervous system in dogs in Europe.

Question 17

List the clinical signs of Angiostrongylus vasorum

Answer 17

May show no clinical signs, while others range from mild to severe clinical signs, and occasionally death. If clinically affected, dogs present with exercise intolerance, coughing, and dyspnoea, progressing to right heart failure in advanced cases

Question 18

Outline the diagnosis process of Angiostrongylus vasorum

Answer 18

Baermann apparatus (intermediate sampling)

Tracheal wash or bronchoalveolar lavage

Radiograph can sometimes show shift of heart axis to left suggesting right ventricular enlargement

Question 19

Outline the treatment for Angiostrongylus vasorum

Answer 19

Fenbendazole, moxidectin, milbemycin

Prevention: standard worming every 3 months is recommended

Question 20

Outline the life cycle of Aelurostrongylus abstrusus

Answer 20

First-stage larvae from the faeces.

These larvae must enter a slug or snail intermediate hosts, in which they develop to the third stage, which is infective for the definitive hosts.

If the infected gastropod is ingested by a suitable small mammal, or a frog or a lizard, these can serve as paratenic hosts.

Infection of the cat is by ingestion of an infected intermediate or paratenic host.

Following ingestion the larvae likely undergo a tracheal migration. The pre-patent period is 5-6 weeks.

Question 21

List the clinical signs of Aelurostrongylus abstrusus

Answer 21

Dyspnoea, wheezing and coughing

Question 22

Outline the diagnosis for Aelurostrongylus abstrusus

Answer 22

Baermann apparatus (intermediate sampling)

Tracheal wash or bronchoalveolar lavage

Radiographs

Question 23

Outline the treatment for Aelurostrongylus abstrusus

Answer 23

Fenbendazole, Ivermectin, Levamisole

Question 24

List the types of lungworm which reside in the intestine but migrate through the lungs

Answer 24

Ascaris Suum - Pigs
Toxocara Canis - Dog

Question 25

Outline the lifecycle for Ascaris Suum

Answer 25

Pig injects eggs

Eggs hatch i the intestine into L2

Migration to the HP vein and liver (develope into L3)

Migrate to heart and lungs (brief respiritory symptoms)

Coughed up and swallowed ( L4 Adult develops within the intestine)

Intestinal symptoms

Eggs in faeces

Question 26

Outline the life cycle for Toxocara Canis

Answer 26

In the environment eggs become infective

Eggs ingested by dog which hatch and release larvae which penetrate intestinal wall

Inn younger dogs the larvae migrate through the lungs and bronchial tree; larvae are coughed up, swallowed, and returned to the small intestine, where they mature

Adult female worms deposit eggs in the small intestine. Although older dogs may be infected in the same way, larvae are more likely to encyst in tissues.

Encysted stages are reactivated in female dogs during late pregnancy and infect the puppies via the transplacental or transmammary route.

As a result, adult worms become established in the small intestine of the puppies

T. canis can also be transmitted through ingestion of transport hosts. Eggs ingested by small mammals (eg, rabbits) hatch into larvae, which penetrate the intestinal wall and migrate into various tissues where they encyst.

The life cycle is completed when dogs eat these hosts, and the larvae develop into egg-laying adult worms in the small intestine.

Question 27

Explain the zoonotic effects of Toxocara canis

Answer 27

Humans are accidental hosts who become infected by ingesting infective eggs in contaminated soil or infected transport hosts. After ingestion, the eggs hatch into larvae

The larvae penetrate the intestinal wall and are circulated to various tissues (eg, liver, heart, lungs, brain, muscle, eyes).