Lungworms Flashcards
What are the 3 primary lungworms of ruminants?
Dictyocaulus
- Protostrongylus*
- Muellerius*
Dictyocaulus spp. is typically found in what climate?
Moist, temperate climates.
Tends to be found around the tropics.
Name the primary hosts for these species:
- Dictyocaulus viviparous*
- Dictyocaulus filaria*
- Dictyocaulus arnfieldi*
-
D. viviparous
- cattle, bison, camelids, wild ruminants
-
D. filaria
- sheep, goats, wild ruminants
-
D. arnfieldi
- donkey, horse
Is Dictyocaulus viviparous in fact viviparous?
(The answer…may surprise you)
Lol Nope.
D. viviparous is, in fact, ovoviviparous.
Recall that this means eggs are laid containing and L1 larva.
How would you describe these lips (other than sensuous)?
Pair of tri-lobe lips.
This is characteristic of Dictyocaulus adults.
What characteristic can you use to know that you are looking at a Dictyocaulus spp. larva?
Brown food granules in intestine.
Where do adult Dictyocaulus live?
Bronchi and bronchioles
Lay eggs, which are coughed up, swallowed, and passed in the feces.
Describe the larval migration of L3 Dictyocaulus once swallowed.
Gut, lymphatics, thoracic duct, blood, heart, lung, pulmonary capillaries, alveoli, bronchioles and bronchi.
So, like, if Dictyocaulus adults live in the lungs, how do the eggs get into the feces?
Eggs are coughed up, swallowed, and passed in the feces.
List the prepatent periods of each of the Dictyocaulus species.
-
D. viviparous
- 4-10 weeks
-
D. filariae
- 4-6 weeks in goats, 8 weeks in sheep
-
D. arnfieldi
- 4-5 weeks
What do larval Dictyocaulus feed on?
Trick question!
The larvae do not feed, but rely on stored food granules in the gut.
In what scientists are calling “rad” and “totally awesome,” Dictyocaulus larvae rely on this fungal species for dispersion.
Pilobolus
True or False:
The penetration phase with Dictyocaulus tends to be asymptomatic.
True
This phase involves L3 migration from the gut to the lungs via the lymphatics, then the blood stream.
What kind of exudate would you expect to find in the bronchioles of an animal infected with Dictyocaulus during the prepatent phase?
Eosinophilic exudate
What kind of pathology would you expect to see during the patent phase of a Dictyocaulus infection?
- Adults in the upper airway result in severe bronchitis and epithelial damage.
- Airways blocked by worms.
- Frothy mucus + cellular exudate.
- Emphysema and consolidation of lobules.
- Secondary infection, pneumonia.
These worms were found in the lung of a cow. What species do you suspect?
Dictyocaulus spp.
Whenever you see a mass of worms in the bronchi of a ruminant, you should think Dictyocaulus.
Because this is a cow, the species is probably Dictyocaulus viviparous
Wow look, cytology! And things are happening on it!
Dictyocaulus worms in bronchi. Note the inflammatory exudation and cellular infiltration.
These are lungs. But not normal lungs! What’s going on?
Interstitial emphysema.
In this case, this is parasitic bronchitis caused by infection with adult Dictyocaulus worms.
What happens in the post-patent phase of Dictyocaulus infections?
Worms are usually expelled due to the massive immune response.
Worms may not be completely expelled in the case of very large infections.
Some animals may have impaired pulmonary function even after expelling the worms.
When are Dictyocaulus infections most common?
Usually occur in the fall (Sept - Oct)
L3 larvae tend to prefer cool, wet weather
What factors affect the severity of Dictyocaulus infections?
Number of parasites
Size and location of parasites
Host response to parasites
What age of animals tend to be most affected by Dictyocaulus infections?
Calves and yearlings
(especially when exposed to a new pasture)
How can you diagnose Dictyocaulus infections?
Clinical signs (however, these are non-specific)
L1 in fresh feces (Baerman method)
Adult worms detected in necropsy
Why is it important to have a fresh fecal sample when trying to detect Dictyocaulus larvae?
You are most likely to find L1 Dictyocaulus larvae in the feces. However, if the animal happens to have a strongyle infection and you let the fecal sample sit for too long, the strongyle eggs may hatch and release their larvae. You may then mistake these larvae for Dictyocaulus.
GET FRESH POO!
What is the name of this test, and what is it used for?
Baerman test. Used to collect motile larvae from a FRESH fecal sample.
Editor’s note: this test REALLY looks like a poop martini.
What species is this?
L1 larva of Dictyocaulus viviparous. Note the food granules and rounded head.
What species is this?
L1 larva of Dictyocaulus filaria. Note the cephalic button and blunt tail.
Describe the vaccine for Dictyocaulus in ruminants.
Uses irradiated larvae, administered orally.
This vaccine is not available in the US.
INTERESTING STUFF: This was the first vaccine developed against a parasite.
What is the definitive host of Dictyocaulus arnfieldi?
Donkeys
Tends to be most pathogenic in horses
Describe the life cycle of Dictyocaulus arnfieldi
Adults mate and lay eggs in the bronchi.
Eggs coughed up and swallowed.
Hatch to L1 in the GI tract or a few hours after defecation.
L1 molts to L3 within a week.
L3 ingested by host, migrates to bronchi via lymphatics.
Pre-patent period: 4-5 weeks.
How would you diagnose a Dictyocaulus infection?
Clinical signs.
L1 in bronchial washings.
L1 in feces (make sure to get FRESH feces)
Note: Dictyocaulus arnfieldi infections are often not patent in horses and ponies.
You find this egg in FRESH feces from a horse. What species do you suspect?
This is Dictyocaulus arnfieldi.
It’s difficult to distinguish the species from the egg alone (except in D. filaria). You might guess that this was a Dictyocaulus based on the host, symptoms, and the fact that this is a larvated egg.
You find this specimen in the fresh feces of a horse. What characteristics can you use to help identify it?
Host species, sheathed L2, food granules in gut.
This is Dictyocaulus arnfieldi
How could you prevent and control D. arnfieldi infections?
Keep donkeys and horses separated.
Quarantine new animals and treat as needed.
The BIG 3 anthelmintics are effective as treatment.
What kind of life cycle does Protostrongylus sp. have?
Indirect
Oviviviparous. Eggs hatch in lungs -> L1 in fresh feces -> L1 infects snail intermediate host -> IH ingested by definitive host -> L3 migrates through lymph nodes then to heart and lungs.
List the intermediate and definitive host of Protostrongylus
IH: snail
DH: small ruminants (sheep and goats)
What is the prepatent period of Protostrongylus?
1 month
There is an additional mode of infection for Protostrongylus other than ingestion. What is it?
Transplacental transmission.
Larvae migrate to the fetal liver. After birth, they migrate to the lung.
Protostrongylus is a major problem in this wildlife species.
Bighorn sheep.
What are the clinical signs associated with Protostrongylus infection?
Local inflammation and exudate in the bronchioles.
Epithelial desquamation in alveoli and bronchioles.
Lobular pneumonia.
Infections are usually subclinical
Identify this L1
Protostrongylus
Note the sharp, tapered tail.
Name the intermediate and definitive hosts of Muellerius sp.
IH: terrestrial snails
DH: small ruminants
What are the prepatent and patent periods of Muellerius?
Prepatent: 4-6 weeks
Patent: 5-6 years
What are the clinical signs of heavy Muellerius infections?
Bronchopneumonia
Cough
Fibrinous pleuritis
How would you diagnose a Muellerius infection?
Baerman on fresh feces to identify L1
Identify this L1
(arrow is pointing to a diagnostic characteristic)
Muellerius
Note the dorsal spine on the tail
Tissue from a lung infected with Muellerius. Describe the lesions.
Sub-pleural granulomatous nodules
Young nodules contain adults, eggs, and L1
Older nodules calcified
Identify these larvae and name the features you used to identify them.
Left: Dictyocaulus filaria
- Cephalic button on head, food granules in gut, tail ends in sharp point
Middle: Protostrongylus
- Long tail tapers to a point
Right: Muellerius
- Tail has an undulating tip and a dorsal spine.
What drugs would you use to treat Protostrongylus and Muellerius infections?
Avermectins
Benzimidazoles
Levamisole
What is the definitive host of Metastrongylus?
Pigs
What is the distinct morphological feature of adult Metastrongylus males?
Reduced copulatory bursa
What is the intermediate host of Metastrongylus?
Earthworms
How does a pig become infected with Metastrongylus?
Ingestion of earthworm containing an L3 larva.
L3 then migrates through the lymphatics to the blood and then the lungs.
Prepatent period: 3-4 weeks.
What stage of Metastrongylus is shed into the environment?
L1 in eggs
Metastrongylus can live for years inside its earthworm intermediate host. Which other lungworm can do this?
Syngamus
What symptoms are associated with infection with Metastrongylus larvae and adults?
Larvae: petechial hemorrhages in lungs
Adults: bronchiolar obstruction, secondary pneumonia
Why is fecal flotation not a reliable method for detection of Metastrongylus? What method should you use instead?
Eggs do not float well, which can result in false negatives.
Some suggest floating with zinc or magnesium sulfate instead of sugar.
Clinical signs are suggestive.
Adults can be detected at necropsy.
Identify this egg found in the fresh feces of a pig.
Metastrongylus
Note the thick shell and larvated egg.
Do not confuse with Ascaris, which is not larvated at this point in time.
You find these in the bronchioles of a pig at slaughter check. What species is this?
Metastrongylus
How would you prevent Metastrongylus infections?
Prevent access of hogs to earthworms by:
raising on concrete or in confinement
use nose rings to prevent rooting in soil
What can you use to treat Metastrongylus infections?
Fenbendazole
Ivermectin
Levamisole
What is the definitive host of Crenosoma vulpis?
Canines and raccoons
What is the intermediate host of Crenosoma?
Gastropods
What is the prepatent period for Crenosoma vulpis?
19 days
Which stage of Crenosoma is infective?
L3 in intermediate host
Identify this species
Crenosoma vulpis
Note the crenations in the cuticle (hence the species name)
How would you identify a Crenosoma infection?
History of outdoor exposure
Clinical signs
Detection of L1 in feces or sputum (don’t confuse with Filaroides)
Broncho-interstitial pattern on radiograph
How would you distinguish Crenosoma L1’s from Filaroides?
Crenosoma does not have a kink in the tail
What drugs would you use to treat Crenosoma vulpis?
Fenbendazole
Milbemycin oxime
Prednisone (for inflammation)
Note: these are extra-label usage
