Dog and Cat CVRS Nematodes + Linguatula

Dog and Cat CVRS Nematodes Summary

(lungworms and heart worms)

Metastrongyles (Lungworm)

• mollusc intermediate host

• not zoonotic

1. Angio-strongylus vasorum→ Dog lungworm

   • french heartworm/lungworm

2. Os-ler-us osleri

   • atypical (no intermediate host), dog,

3. Ae-leuro-strongylus ab-stru-sus→ Cat lungworm

Filaroidea (Heartworm)

4. Dirofilaria immi-tis- Dog and cat

   • indirect lifecycle

   • zoonotic mosquito intermediate host

   • no eggs → microfilaria (preL1)

   • imported in UK

Penta-sto-mid parasite

• infects adult nasal cavity and frontal sinuses of canids

• closely resembles arthropod (+ worm)

• zoonotic

Lingua-tula serrata

• have nymphs and adults

Angio-strongylus vasorum appearance

• Slender, <2.5cm

• Separate males/females

  • Females like Haemonchus contortus (ruminant GI nematode) → red barber’s pole (uterus + intestine)

Angio-strongylus vasorum hosts

• Final host: canid (dogs + foxes)

  • Young dogs more prone

  • Foxes wild reservoir

    • US- sporadic fox and coyote

• Intermediate host: mollusc

• (rat version is zoonotic)

Angio-strongylus vasorum target organs

• French lungworm → pulmonary arteries

• French heartworm → RHS heart

Angiostrongylus vasorum prepatent period

6-10 weeks

Angio-strongylus vasorum life cycle [7]

1. Mollusc eats L1 from canid faeces

2. L1 → L3 in mollusc

3. Dog eats mollusc or slime trail with infective L3

4. L3 travels to gut mesenteric lymph nodes → mature to L4

5. L4 lymph nodes → pulmonary artery/ right ventricle migration → mature to L5

6. L5 lay eggs → hatch to L1 in lung capillaries

7. L1 coughed up and swallowed → egestion in faeces

Angiostrongylus vasorum disease symptoms

• Can be subclinical

  • esp. foxes → natural host with resistance

• 3 clinical syndromes in dogs:

  1. Cardiorespiratory

     • Blockage of blood vessels by worms

     • Inflammation of lungs by L1 breaking into alveoli

  2. Coagulopathy

     • Reduced platelet numbers and clotting factors

     • Bleeding into skin, eyes, body cavity, lungs

  3. Neurological

     • Result of coagulopathy → bleed into brain

     • Rarely larvae in brain

Angiostrongylus diagnosis

• Clinical signs (if not subclinical) → e.g. subconjunctival haemorrhage due to coagulopathy

• Chest radiograph → enlarged RHS heart

• L1 detected faeces and sputum

• Blood tests

  • Lateral flow → subclinical infection

  • Coagulation test

Angiostrongylus vasorum treatment

• Anthelmintics

• Supportive care

  • Blood transfusion + oxygen

Angiostrongylus vasorum epidemiology

• Worldwide emerging disease

• Hotspots (endemic foci) → prophylactic treatment

  • SE England

  • S Wales

• Prevalent in W Europe

• Sporadic cases

  • Canada

  • North America

  • South America

Oslerus osleri hosts

• Special metastrongyle → NO INTERMEDIATE HOST → direct lifecycle

• Canid host

• Associated with breeding kennels and racing greyhounds

• L1 infective stage

Oslerus osleri organs

Adult worms form tracheal nodules

Oslerus osleri life cycle [4]

1. L1 (infective) transmitted in saliva from bitch to puppies when grooming

2. L1 → L2 in gut

3. L2 migrates gut → lungs

4. Matures into adult in lungs and trachea

Oslerus osleri disease symptoms

Usually asymptomatic but may have chronic dry debilitating cough

Ae-luro-strongylus ab-stru-sus hosts

• 1cm adult worm

• not very common

• Intermediate: mollusc → rodent host

  • rodent eats mollusc

• Final: cat

Ae-luro-strongylus ab-stru-sus target organ

Adults live in cat lung parenchyma and small bronchioles

Aelurostrongylus abstrusus life cycle [5]

1. L1 egested in cat faeces

2. L1 eaten by mollusc

3. Mollusc eaten by rodent

4. Rodent eaten by cat

   • Cats unlikely to directly eat mollusc → need rodent intermediate

5. Adult worm lives in lung parenchyma and small bronchioles

Aelurostrongylus abstrusus clinical signs

• Low pathogenicity, usually asymptomatic

  • More clinical effects in immunocompromised cats (e.g. FIV)

• Chronic mild cough possible

• Dyspnoea possible in heavy infection

Diro-filaria immi-tis appearance

• Long worms, females bigger

  • M 15cm, F 30cm

• Form mesh → may block blood vessels

• Female Dirofilaria → release microfilaria (preL1) into blood

  • no eggs

Dirofilaria immitis hosts

• Intermediate: mosquito

  • zoonotic (but rare)

• Final: dog

• (not natural: cat, ferret, human)

Dirofilaria microfilaria frequency in dogs

• Only 60% infected dogs

• 15% killed by host immunity

• 25% cannot reproduce

  • sexually immature

  • only 1 worm

  • all worms same sex

Dirofilaria immitis target organs

• Dog RHS heart

• Pulmonary arteries

• Posterior vena cava

Dirofilaria immitis life cycle [6]

1. Female mosquito feeds on host transmitting L3

2. L3 migrate from blood → subcutaneous tissue to mature

   • 4 month period

3. Young adult worms (from mosquito bite) migrate from subcutaneous tissue → heart and vessels

   • Can survive and build up for years

4. Worms mate and release microfilariae into blood

   • Microfilariae can survive ~2 years

5. Female mosquito ingests microfilariae from bloodstream

6. Microfilariae → L1 → L3 inside mosquito

   • Takes 2 weeks

Dirofilaria immitis dog clinical signs

• Clinical signs usually in dogs >2 years old

  • Long prepatent period

  • Worm buildup takes time

• Adult mesh obstructs blood flow in high numbers → congestive heart failure

  • Exercise intolerance

  • Acute collapse

  • Fatality

  • Abdominal ascites

Dirofilaria immitis cat clinical signs

• Not natural host → reduced susceptibility

• Adults shorter lifespan (<2 years)

  • Fewer adult worms present in heart

• Transient microfilaraemia

• Usually respiratory signs

  • Parasites in distal pulmonary arteries → pulmonary pneumonia

• Larvae in other tissue → eye

  • Potentially fatal (CNS)

Dirofilaria immitis zoonosis

• dead end host

  • Microfilaria enter subcutaneous tissue → right ventricle → die

  • Embolise pulmonary vessels

• Human infection rare

• small pulmonary infarction (pulmonary vessel embolism) = coin lesion

  • can be mistaken for neoplasia on radiographs due to nodular appearance

Dirofilaria immitis diagnosis

• Blood microscopy and serology for microfilaria

  • Only works for 60% dogs

• Ultrasound → adult worms

Dirofilaria immi-tis Treatment

1. Doxy-cycline

   • kills symbiotic intracellular Wol-ba-chia bacteria

   • inhibits embryogenesis and long term survival of parasite in body

2. Macro-cyc-lic lactones (treatment + prophylaxis)

Linguatula serrata (pentastomid) hosts

• NOT A NEMATODE

• imported to UK

• Intermediate: herbivores

• Final: canid (+ human → zoonotic)

Linguatula serrata target organ

Canid nasal cavity and frontal sinus

Linguatula serrata life cycle [4]

1. Raw offal of herbivore host (containing nymphs) eaten by canid

2. Nymphs migrate up oesophagus → nasopharynx for maturation

3. Mature adults lay eggs in nasopharynx

4. Eggs released in nasal secretions (e.g. sneezing) or faeces to infect intermediate hosts

Linguatula serrata clinical signs

Rhino-sinus-itis (sneezing, nasal discharge etc)

Linguatula serrata epidemiology

Tropical regions

• Central Asia

• N. Africa

• Middle East

• E. Europe

Imported into UK