Lecture 5 dictyocalaus

Series of Presentations on Nematodes from Veterinary Parasitology By Urquhart, Jenning

1. Trichostrongyloidea

2. Dictyocaulus
Thisgenuslivinginthebronchiofcattle,sheep,
horsesanddonkeysisthemajorcauseof
parasiticbronchitisinthesehosts.
Hosts
Ruminants, horses and donkeys
Site
Trachea and bronchi

3. Species
D. viviparus cattle & deer
D. filaria sheep & goats
D. arnfieldi donkeys & horses

4. Identification
•The adults are thread like worms up to 8.0
cm in length.
•Their location in the trachea and bronchi
and their size are diagnostic.
•D. viviparusis the most pathogenic of the
three species

5. Dictyocaulus viviparus
D.viviparusisthecauseofparasiticbronchitisin
cattle,alsoknownas
•husk
•hoose
•verminouspneumonia
•dictyocaulosis.
•Thisdiseaseischaracterizedbybronchitisand
pneumonia.
•Thediseaseisprevalentintemperateareaswith
highrainfall.

6. Dictyocaulus viviparus
Cattle lung worm
Definitive Host Spectrum
•Cattle, buffalo, camel
Intermediate Host
None
Geographic Distribution
Worldwide, especially moist temperate regions

7. Morphology
–Adults -males 4-5.5 cm, females 6-8 cm, threadlike,
white
–Eggs -larvated, 82-88 x 33-38 microns (seldom
seen in feces)
–Larvae -300-360 microns (present in feces)

10. Life cycle
•Larvatedeggsarelaidbyfemales,mayhatchin
thelungsbutusuallyarecoughedup,swallowed
andhatchinthealimentarytract.
•L1areusuallyfoundinfecesandreachthe
infectiveL3stagein6daysormorewhenthey
aredispersedwiththefecesandmoveuponto
theforage.
•Larvae(L3)areingested,penetratethe
intestinalwallandarecarriedviathelymphatic
vesselstothemesentericlymphglands.

11. Life cycle
•Amolttakesplaceintheselymphglands,
thenthelarvaemigrateviathelymphand
bloodvesselstothelungs
•Larvae(L4)becomearrestedinthe
capillariesandbreakintotheairpassages,
wheretheymaturetoL5andadult
•Prepatentperiod-22days

12. Pathogenesis
Site of Infection
•Lumen of trachea, bronchi, bronchioles
Pathogenesis/Clinical Signs
•Blockage of bronchioles with an eosinophilic
exudate
•Atelectasis and emphysema
•Severe damage to the epithelium of the
trachea and bronchi may be caused by
inflammation with neutrophils, macrophages,
and eosinophils

13. Pathogenesis
•Eosinophilssecretemajorbasicprotein
(MBP)whichdamagesparasitemembranes
andistoxictonormaltissue
•Pulmonaryedemaand2ndbacterialinfection
•Clinicalsigns-coughing,dyspnea,polypnea,
rapidlossofcondition
•Onceexposed,protectiveimmunityis
establishedforthefollowingyear,butrequires
consistentexposureforimmunitytopersist

15. Aspirated DictyocaulusviviparusL1
surrounded by inflammatory cells

16. Diagnosis
•Eggs and larvae in nasal discharge
•Finding L 1 in feces using Baermann
technique can confirm an active infection but
may miss a light infection
•specific ELISA which demonstrates exposure

17. Treatment
•Albendazole
•Fenbendazole
•Ivermectin, doramectin, eprinomectinapproved
@ 200 mcg/kg
•Improvement should be observed after
approximately 24 hours

18. Other Control Measures
•Immunization with x-irradiated L 3 is
commercially available and used in Europe
•Effective in highly endemic areas, doesn’t
work well where there is a low year-round
infectivity
•Shelf life of irradiated larvae is 3-6 months
Public Health Significance
•None

19. Dictyocaulus arnfieldi
(LUNGWORM )
Definitive Host Spectrum
–Horse, mule, donkey, zebra
–Donkey is usually the source of infections in
horses and is the natural DH
Intermediate Host
–None
Geographic Distribution
–Worldwide

20. Dictyocaulus arnfieldi
Morphology
–Adults -males up to 36 mm, females up to 60
mm
–Eggs -larvated, 80-l00 x 50-60 microns

21. Life Cycle (Stages)
–Larvated eggs are coughed up, swallowed, passed
in feces, hatch within a few hours
–L 3 are the infective stage and are ingested
–Migration to the bronchi is via the lymph vessels
–Prepatent period
–12 to 14 weeks in donkeys
–6 to 8 weeks in horses

22. Pathogenesis
Site of Infection
–Bronchi, bronchioles
Pathogenesis/Clinical Signs
–Generally nonpathogenic in donkeys, even with
heavy infections
–Clinical signs in horses, appearing during the
prepatent period, include coughing, polypnea, nasal
discharge

23. Diagnosis
–For patent infections, eggs or L 1 in feces
–For horses with clinical signs described
above, co-grazing with donkeys is suggestive
of dictyocauliasis

24. Treatment & control
Treatment
–Moxidectin(Quest)
–Fenbendazole, 5mg/kg (single dose)
–Ivermectin@ 200 mcg/kg
Other Control Measures
–Graze donkeys and horses separately
Public Health Significance
–None

25. (Dictyocaulus filarial(THREAD
LUNGWORM OF SHEEP
Definitive Host Spectrum
–Sheep, goats, some wild ruminants
Intermediate Host
–None
Geographical Distribution
–Worldwide, especially important in eastern
Europe and India

26. Morphology
–Adults –thread like, males 3-8 cm, females 5-10 cm
long and fairly mobile
–Eggs -larvated, 112-138 x 69-90 microns
–Larvae -550-580 microns long, with a cuticular
knob at the anterior end, contains dark food
granules

27. Life Cycle (Stages)
–Larvated eggs are laid by females, may hatch
in the lungs but usually are coughed up,
swallowed and hatch in the alimentary tract
–L 1 are usually found in feces and reach the
infective L 3 stage in 6 days or more when
they are dispersed with the feces and move
up onto the forage
–Larvae (L 3 ) are ingested, penetrate the
intestinal wall and are carried via the
lymphatic vessels to the mesenteric lymph
glands

28. Life Cycle
–A molt takes place in these lymph glands,
then the larvae migrate via the lymph and
blood vessels to the lungs
–Larvae (L4) become arrested in the capillaries
and break into the air passages, where they
mature to L5 and adult
–Prepatent period -about 4 weeks

29. Pathogenesis
Site of Infection
–Mucosa of trachea, bronchi, bronchioles
Pathogenesis/Clinical Signs
–Catarrhal bronchitis, with exudate passing
back into the alveoli, causing atelectasis or
pneumonia
–2nd bacterial infections and more extensive
areas of pneumonia
–Clinical signs -dyspnea, polypnea, cough,
mucous exudate from the nostrils, abnormal
lung sounds on auscultation

30. Diagnosis & Treatment
Diagnosis
–Usually by finding larvae (L 1 ) in feces by use
of Baermann technique
–Eggs may be found in nasal discharge or
sputum, but their absence is insignificant
Treatment
–Levamisole, 7.5 mg/kg parenterally
–Ivermectin-approved as a drench,
eprinomectin
–benzimidazoles