Nematodes Part 2 Flashcards
Thelazia californensis
- adult and egg characteristics
Adult
- males and females
Eggs
- embryonated, hatch in uterus of female worm
- larvae L1
Thelazia californensis
Lifecycle
Infective stage
- First stage larvae (L1 in tears) ingested by face fly
- Molts to L3 in fly
- L3 larvae are deposited when teh fly feeds around the eye
- Mature to adults in conjunctiva/lacrymal duct
- L3 larvae are the infective stage
Thelazia californensis
What pathology/Clinical signs looks like
Lesions result only from large number of worms
- conjunctivitis, keratitis
- photophobia
- excessive tearing
Thelazia californensis
Diagnosis
Observe parasits on eye surface, conjunctival sac
Lachrymal secretions may contain L1 larvae
Thelazia califonrnesis treatment
Remove parasites
- manual; brush or irrigation
Ivermectin
Control musca autumnalis (face fly)
Diotophyme renale
- common name
- where its found and in what species
- who is the DH
- IH and paratenic hosts if any
- giant kidney worm
- found in the kidney of dogs, wolves, mink, foxes, rarely found in cats, humans, pigs, cattle
- the DH = minkes
- IH = annelid, they live on the surface of crayfish
- paratenic hosts = fish, frogs
Dioctophyme renale
- adult and egg characteristics
Adults
- large
Eggs
- barrel shaped, bipolar plugs, rough shell
- nonembryonated
- found in urine
Dioctophyme renale
Lifecycle
Infective stage
- Eggs leave DH via urine - viable up to 5 years in environment
- Ingested by annelid=IH and develop to an L3
- Paratenic host may ingest annelid/crayfish where the L3s encyst
- DH ingests the annelid/crayfish or paratenic host
- L3 excysts and leaves the intestine, migrates to the kidney and matures
Infective stage = L3
Dioctophyme renale
- clinical signs and pathogencitiy
Clinical signs
- typically no clinical signs
- though adults can block the ureter, cause peritonitis and renal failure
Pathology: usually the right kidney only
Dioctophyme renale
Diagnosis and treatment
Diagnosis
- urine sedimentation - they sink
- adults (laparotomy, hysterectomy)
Treatment
- none
- remove adults or kidney?
Pearsonema plica and pearsonema feliscati
- common name
- where its found and in what species
- IH and paratenic hosts if any
- urinary bladder worm
- found in the urinary bladder and pelvis of kidney. P. Feliscati is found in cats, and p. Plica is found in dogs, wolves and foxes
- paratenic host = earthworm
Pearsonema spp.
Adult and egg characteristics
Adults are slender and filamentous
Eggs have bipolar ends
Pearsonema spp.
Lifecycle and infective stage
- Eggs leave DH via urine - larvate to L1
- Eggs with L1 ingested by earthworm - L1 in tissues of earthworm. So its a partentic host bc it does not develop within the earthworm
- DH ingests earthworm - larvae released in intestine
- L1 excysts - penetrates intestine, matures in mucosa of urinary bladder.
Pearsonema sp. clinical signs
- mostly asymptomatic
- irritation of bladder mucosa, cystitis
Pearsonema spp.
Diagnosis and treatment
Diagnosed in urine
Treatment: non approved
Febendazole, ivermectin, may need to repeat
Eucoleus aerophilus and eucoleus boehmi
- common name
- which worm is found where and in which species
- IH?
- lungworm
- E. Aerophilus found in respiratory tract of dogs, cats, foxes
- E. Boehmi found in the nasal cavity, paranasal sinuses of dogs and foxes
- direct lifecycle = no IH
Eucoleus spp.
- adult and egg characteristics
Adults: male and female
Eggs: main difference is aerophilus looks netted while boehmi shell looks pitted, there are little dots everywhere
Eucoleus spp.
Lifecycle and infective stage
- Adults in lungs, eggs leave DH via feces
- Eggs larvate to L2 once in environment
- DH ingests egg with L2 larvae released into intestine and penetrat mucosa of either a fox or a dog.
- Larvae migrate to lungs, mature in bronchioles, bronchi and trachea
Eucoleus spp.
Clinical signs and pathogenicity
- usually asymptomatic
- severe infections: coughing, nasal discharge, bronchitis, pneumonia, anorexia, dyspnea. Secondary infections possible
- mucosa edema, inflammation, hemorrhage
Eucoleus spp.
Diagnosis and treatment
Diagnosis
- fecal exam bc they are coughed up then swallowed
- differentiate from similar eggs
Treatment
- fenbendazole treat very well
- ivermectin
Identifying trichuris v. Pearsonema/eucoleus
Trichuris
- Much larger
- smooth shell
- very symmetrical plugs
- at 40x mag you will find rings on trichuris plugs and pearsonemas wont have that.
Pearsonema
- smaller
- slightly off-centered plugs
Filaroides hirthi and filaroides osleri
- common name
- which worm is found where and in which species
- IH?
- geographic distribution
- lungworm
- F. Hirthi found in lung parenchyma of dogs and coyotes
- F. Osleri is found in nodules at the bifurcation of the trachea also in dogs and coyotes
- direct lifecycle = no IH
- F. Osleri found in western, midwestern US and Canada
FIlaroides hirthi and filaroides osleri
Characteristics of adult and larva
Adults - filamentous
Larva - “kinky” tail, lacks dorsal spine
Filaroides spp. Lifecycle
- L1 larvae leave DH - feces, saliva, respiratory secretions
- new DH ingests L1
- Migrate to lungs via lymphatics or venous system
Filaroides spp.
Diagnosis
Can find in fecal floatation and fecal sedimentation
Can also do baermann on saliva material
- rads
- endoscope
- often misdiagnosed as kennel cough
Filaroides spp.
Treatment
- fenbendazole
- ivermectin
- inj. Doramectin
- remove nodules
Aelurostrongylus abstrusus
- common name
- where its found and in what species
- IH and paratentic hosts?
- feline lungworm
- found in the lung parenchyma of cats
- IH: land snails and slugs
- paratenic hosts: rodents, birds, amphibians, reptiles
Aelurostrongylus abstrusus
Adult and egg characteristics
Adults
- filamentous
Eggs
- ellipsoid in lungs, larvated
- “hatch” in lungs with a kindy tail and have a dorsal spine at the end of the tail
Aelurostrongylus
Lifecycle
Infective stage
- Eggs in nests in lung nodules - L1 hatch and leave DH via feces (coughed up and swallowed)
- L1 is ingested by land snail - IH develop to L3
- Paratenic host may ingst snail or slug and have the L3s encyst.
- DH ingests snail or slug or paratenic host. Usually its a paratenic host (roden or reptile) since cats dont eat snails often
- L3 excysts - leaves intestine, migrates to lungs, matures
Aelurostrongylus spp.
Clinical signs and pathogenicity
Clinical signs
- light infections: asymptomatic
- mod. Infections: coughing, anorexia
- heavy infections: chronic cough, dysnpea, diarrhea, wasting
Nodules on lung surface - milk fluid, eggs, larvae
Aelurostrongylus
Diagnosis and treatment
Diagnosis
- fecal exam: L1s
- thoracic rads
Treatment
- fenbendazole
- moxidectin
- emodepside
Angiostrongylus cantonensis
- common name
- where its found and in what species
- incidental hosts
- IH and paratenic hosts?
- rat lungworm
- found in the heart and pulmonary arteries of rats
- incidental hosts include humans, non-human primates, opossums, horses, dogs, birds
- IH = snails/slugs
- paratenic hosts = crabs, shrimp, fish, frogs
Angiostrongylus cantonensis
Adult and larva characteristics
Adults
- male and females
Larva
- L1: notch in tail
- L3: ensheathed, what you find in snails
A. Cantonensis
Used to be endemic in Hawaii now found in continental US and in parts of Asia, Pacific islands, caribbean
Angiostrongylus cantonensis
Lifecycle
Infective stage
- Eggs in lungs, hatch - L1 break thru respiratory tract, migrate up trachea, swallowed; shed in feces
- L1 ingested by land snail - IH; develop to infective L3
- rat (DH) or incidental host ingests the snail/slug or paratenic host.
- L3 migrate to brain and mature to L4/L5
- L5 migrate to heart/pulmonary arteries and develop into sexually mature adults
Infective stage = L3 larva
Angiostrongylosis
Diagnosis and treatment
Diagnosis
- IgG and CSF ELISA
Treatment
- prognosis is good
- prednisolone 4weeks - 3 months
Angiostrongylosis
Important factors
- initial infective dose, host has ability to keep larvae away from CNS
- vomiting (L3 penetration) precedes neuro signs 7 - 10 days; may also occur with neuro signs
Angiostrongylosis cantonensis
Clinical signs
- eosinophilic meningitis
- paralysis
- headache seen in humans
Thelazia Californensis
- common name
- where is it found and in what species
- IH and paratenic host if any
- eye worm
- found in the conjunctiva and tear ducts of dogs and cats, sheep, deer and humans
- IH = face fly
Dracunculus insignis
- common name
- where is it found and in what species?
- IH and paratenic host?
- serpent on a stick
- found in SQ tissue of dogs, foxes, cats, racoons, mink
- IH: copepod
- paratenic host: frog
Dracunculus insignis
Lifecycle
Infective stage
- Female in SQ blister releases L1s when contact water
- IH - copepod ingests L1 where it develops to an L3
- Possible parentenic host = frog
- DH ingests copepod or frog
- L3 penetrate intestine and migrate to SQ connective tissue
- Gravid females in skin blister
Infective stage = L3
Dracunculus insignis
Clinical signs and pathogenicity
Painful skin ulcers
Dracunculus insignis
Diagnosis and treatment
Diagnosis
- observe female under skin
- coax L1 from blister via water
Treatment
- fenbendazole
- ivermectin
- do not cut the worm if you are trying to remove from a blister bc it will induce an anaphylactic reaction. Better just to submerge in water and they will emerge.
Dirofilaria immitis
- common name
- where they are found and in what species
- heartworm
- right ventricle, pulmonary arteries of dogs, cats, ferrets, sea lions, seals and others
Dirofilaria immits
Adult and microfilariae characteristics
Adults
- long, slender, white nematodes
- females are very long
- the males are shorter with a corkscrew tail
Microfilaria
- they are PRE-larval stage; they are NOT larva!
- tapered at anterior end; tail may be straight or hooked though hooked artifact of formalin fixation
Differentiating microfilaria dirofilaria from acanthocheilonema
acanthocheilonema reconditum
- usually few
- motion is progressive; they go across your field of view and leave it
- body shape is curved, blunt head and curved tail
Dirofilaria immitis
- usually many
- they are STATIONARY
- body shape is straight body and tail with tapered head
Dirofilaria immits
Occult infections
- dogs harboring male and/or female adults in a “hidden infection”
- possible due to single sex infection, low numbers
- best diagnosed with Ag tests
Mff not detectable in peripheral blood
Dirofilaria immitis
Microfilarial periodicity: why are there variations of Mff that appear in blood over time
- Nocturnal periodicity** - Mff are present in blood during evening hours
- Incomplete periodicity** - Mff never disappear completely form peripheral blood during 24hr period
- Diurnal periodicity - Mff present in blood during daylight hours
- Complete periodicity - Mff disappear from peripheral blood at some time during 24hr period - no one knows where they go
Stages of dirofilaria immitis
- Adult heartworms
- Developed embryo within the uterus of females
- Pretzel stage within the uterus of females
- Stretch microfilaria within the uterus of females
- Circulating D. Immitis microfilariae
Life cycle of dirofilaria immitis in dogs
- Mff released by female worm - enter circulation, mosquito feeds on dog with circulating microfilariae
- Microfilariae develop to infective larvae L3 in the mosquito (temperature dependent)
- Infective larvae are deposited at the skin surface when mosquito takes another blood meal - L3s enter DH at the mosquito bite wound
- Larvae undergo several molts during theri migration tot he heart and lungs
- Adult worms mature in the heart or lungs, mate and produce Mff
INFECTIVE STAGE OF DIROFILARIA IMMITIS
L3!!!!
Do you get positive antigen test before or after seeing microfilaria in the blood? Why?
- you get positive antigen tests BEFORE you see microfilaria in the blood.
- you have mature adults before you have microfilaria. So the antigen test picks up antigen from adults.
Heartworm vectors
How many different species have L3s been found in?
How many species can transmit the heartworm?
How many are considered common vectors
The mosquito
- L3s have been found in 70 species
- 23 species can transmit the heartworm
- 14 species of mosquitos are common vectors
Dirofilaria immitis
Pathogenicity
Disease is primarily due to adults in RV and pulmonary artery
- “villous endarteritis” - irritate vessel walls, produce pro-inflammatory molecules that induce inflammation of vessels
- vascular resistance - inflammation increases cardiac workload, RV hypertrophy
- decrased cardiac output - decrased organ perfusionw ith blood leading to exercise intolerance and liver and kidney disease
- coughing and hemoptysis
Dirofilaria immitis
Clinical signs
- asymptomatic
- mild/moderate; mild radiographic signs, mild proteinuria, slight loss of condition, exercise fatigue, intermittent cough
- severe: clear rad signs, severe proteinuria, wasting, chronic fatigue, persistent cough, ascites
- vena cava syndrome: overrun with worms, infect atrium and vena cava, obstruct blood flow, interfere with tricuspid valve closure
Diagnosing heartworm
- Hx and CS
- detection of antigen (which detect adult worms): point of care tests, test annually!!
- detection of circulating microfilariae
- imaging techniques
When dogs become antigen positive
- you get antigen positive tests BEFORE you see microfilaria in the blood
- the earliest you can become antigen positive is 5 months, the latest is 7 months.
- so we average it out and say the earliest you can become antigen positive is 6.5 months
- if you have macrocyclic lactone prevention with missed doses may result in delayed HW maturation and patient conversion to antigen positive status and occur at 9 months
The gold standard test for diagnosing HW
The DiroCHEK canine HW antigen test
- this is the test to use if you are getting “iffy” results
- it is a serum or plasma well test.
Name a test for finding microfilariae and describe how it works
Knotts test - it lyses microfilaria and cells and stains purple so they are easy to see
Testing stratgies for dirofilaria immitus
Antigen testing ANNUALLY
- test dogs once they are 7 months of age
- test dogs 7 - 12 months after starting prophylaxis
- dogs missing doses of preventative medication for more than 3 months (7 - 12 months after restart)
- with seasonal prophylaxis
Reasoning for re-testing
- ANNUALLY
- when pets with signs consistent with HW disease test negative
- pets in low endemic areas or on preventive medication have weakly positive results
- product switch (4.5 months tells you if first product failed; 9 months tells you if 2nd product failed)
Problems/issues in diagnosis (canine)
Antigen test: positive
Microfilaria test: negative
- Brand new infection that has adults but not yet produced microfilaria
- They may be on preventative that can get rid of microfilaria but not adults
- Single sex infection - you get antigen positive but no males so cant produce microfilaria
- Dog is true immune-mediated occult
- Low numbers of microfilaria circulating and you just arent finding them in blood. This is when you should do concentrated knotts test.
Problems/issues in diagnosis (canine)
Antigen test: negative
Microfilariae test: positive
- Microfilaria are another species - this is when you should do a modified knots test
- Microfilaria were acquired transplacentally; rare but has been reported
- Adult worms were removed or have died but microfilaria present
- Contamination of test materials from previous samples
Problems/issues in diagnosis (canine)
Antigen test: variable
Microfilaria test: negative or positive
- Fluctuating antigen level due to number of female worms, ages of worms, quality of samples
Prevention/treatment gap
Preventatives target L3s and new L4s - tehy dont treat old L4s or L5s or adults. So once you get to a point in the lifecycle, the preventatives wont do anything.
Susceptibility Gap is in the center of the lifestage between larva - older L4s and L5s where nothing can touch them.
Treatment of heartworm:
Melarsomine dihydrochloride (immiticide)
- greater efficacy of killing adult worms
- NO activity against worms
Which dosage of melarsomine (immiticide) is more appropriate - standard dosage or split dosage?
Split dosage - it gets more worms and is easier for the animal to handle.
Treatment protocol for dirofilaria immitis after getting an antigen positive test result
- Do another test to confirm the positive.
- With 2 positives, start them on preventative (kills microfilaria) and give them some type of tetracycline over a 4 week period. This attacks the wolbachia (bacteria on HWs).
- In 60 days you give them their first injection of immiticide.
- 30 days after first injection, you give your double injection 24 hours apart.
- The entire time you have to keep them on strict cage rest.
Alternatives to immiticide
Continuous monthly use of preventives - which is NOT recommended in any way! You only use as a last resort.
Treatment alternative when arsenical therapy is contraindicated
Give doxycycline to kill wolbachia and help get rid of adults along with monthly preventives.
Restrict exercise for duration of treatment
Test every 6 months
What is wolbachia
- gram + or - ?
- where is it found?
- how does it effect HWs?
- does it contribute to clinical signs?
- gram (-) bacteria related to Ehlichia and anaplasma
- endosymbionts with filarial worms
- present in ALL LIFE CYCLE STAGES of dirofilaria immitis
- important in biological and repro functions
- contributes to pulmonary and renal inflammation
Should you remove microfilaria?
Yes bc even though they dont contribute to clinical signs, they serve as a reservoir for HW that dogs in surrounding area will be susceptible to. (They dont grow into adult worms in the dog)
Why would you omit microfilaricidal treatment?
- all preventives have microfilaricidal properties at their labeled doses
- high Mff counts - use IVM, milbemycin oxime at lower, marginal doses.
Heartworm-Associated Respiratory Disease (HARD)
What is it?
Vascular and airway disease caused by the early death of immature heartworms in cats
Stages of HARD
Stage 1 = immature adults in pulmonary arteries - inflammatory response; immune function suppressed; cats tolerate worms
Stage 2 = worms dying - pulmonary inflammation, thromboembolism** (often what cats die from)
Feline heartworm disease
Diagnosis
- difficult
- often dont see microfilaria bc they have immature infections
- may see increase in eosinophils but its transient
- Ab tests; all it tells you is if they were introduced to the parasite at some point
- Ag tests; tests for mature adults which are mostly females, but cats have mostly male HW infections.
- rads
- echo
Feline Heartworm
Prognosis
- cats with confirmed infections: 1.5 years
- if cats survive acute disease: 4 years is the median
- prevention is key! Variable tests, no cure, unpredictable outcomes
What are the differences between canine and feline heartworm
Canine
- highly susceptible to infection
- many worms
- disease depends on dog size, not worms
- worms are long lived
- usually mff
- heart and lungs affected
- easily diagnosed
- treatment available
- preventives available
Cats
- less susceptible to infection
- few worms
- few worms can cause disease
- worms are short lived
- usually no mff
- lungs most often affected
- diagnosis requires multiple tests
- only symptomatic treatment available
- preventives available
