Parasitic pulmonary disease

rapidcrimsonMechanics

Feb 22, 2014 (3 years and 5 months ago)

76 views

Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

1



Parasitic pulmonary disease



Parasitic pulmonary disease is caused by both lungworms and nonlungworms

o

Some intestinal worms, especially
Toxocara

(round worms) but also
Ancylostoma

(hookworms), undergo
pulmonary migration before the adult worm reaches its final destination in the intestine



Usually, pulmonary migration causes little disease and few (if any) respiratory signs



However, massive larval migration can result in both direct

and indirect inflammatory damage to
the lung, causing verminous pneumonia



Such profound infections typically occur in puppies who may present with cough and tachypnea



CBC is not often performed in young puppies with cough but eosinophilia would be
expecte
d



Fecal flotation may be negative because larval migration occurs before the mature worms
have reached the intestine

o

Empiric treatment is reasonable if pulmonary migration is suspected as a cause
of cough



Anthelmintics should be administered at least twice
, 2 weeks apart



A short course of an antiinflammatory dose of glucocorticoid may ameliorate severe cough but
should not be used before ruling out other causes of infectious pneumonia

o

Although intestinal worms migrate through the lungs on their way to a fin
al destination, for lungworms the
final destination is the respiratory tract



These parasites may reside primarily in the pulmonary parenchyma, in the airways, or both



Parasitic lung disease can be easily confused with other conditions such as bronchopneumo
nia,
eosinophilic pneumonia, asthma, pulmonary granulomatosis, or even pulmonary neoplasia



Unfortunately, intermittent fecal shedding of parasite ova or larvae after expectoration means that
fecal examination is an insensitive diagnostic method



High
-
dose
fenbendazole (50

mg/kg PO q24h for 10 to 14 days) or ivermectin are usually
used

o

Ivermectin must be used with caution in Collies and other breeds with a high
prevalence of MDR1 mutations

Although albendazole

is an effective therapy for lungworms, it has a greater potential for bone marrow toxicity than
fenbendazole

Infectious Parasites of the Airways

Oslerus osleri; Filaroides osleri



ETIOLOGY

o

Filaroides osleri,

renamed
Oslerus osleri,

is a worldwide parasitic disease in dogs younger than 2 years of
age

o

It can be seen in individual situations but is more often a kennel
-
related problem (especially in
Greyhounds)

o

Most commonly affects the region proximal to the tracheal carina



Typically,
affects the lumen and lining of the larger bronchi



Rarely does it extend deeper into the pulmonary system

o

Reports of direct transmission through larvae in the stool and saliva suggest that this metastrongyle may
not require an intermediate host to complete

its life cycle



First
-
stage larvae are directly transmitted through salivary and airway secretions

Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

2




These molt in the small bowel followed by migration of the larvae to the lungs and bronchi



Experimental and natural direct transmission have been demonstrate
d



Transmission to pups has also been reported to occur through parental food regurgitation
and licking and cleaning of pups by a nursing bitch



Prepatency is about 10 weeks (5 weeks for
F. hirthi

).




CLINICAL SIGNS AND DIAGNOSIS

o

Dogs usually present with chronic, mild to severe inspiratory wheezing sounds, dyspnea, coughing,
and/or debilitation



The severity of the clinical signs may be overplayed in the literature

o

Most dogs experience definite but mild, often nonprogressive

respiratory signs

o

Exercise intolerance does occasionally occur and coughing is typically characterized as a harsh
tracheobronchial sound associated with attempts at terminal retching



A small amount of white to blood
-
tinged mucus is common, but at times la
rger amounts of
exudate are brought up

o

Tracheal sensitivity occurs but physical palpation is normal

o

The radiographic examination is helpful if the disease process is extensive and the nodules are large

o

The tracheal lining may be diffusely thickened, interr
upted with indistinct solid masses, or show ill
-
defined,
2
-

to 10
-
mm semicircular lesions protruding into the lumen



Endoscopically, cream
-
colored nodules, 1
-

to 5
-
mm high and wide are usually diagnostic



The larvae are often seen peeking into the luminal ed
ge of the growth

o

Brushings and biopsies of the nodules provide a definitive diagnosis

o

Larvae are occasionally detected in the feces

o

Although some flotation methods dehydrate the larvae, zinc sulfate flotation techniques ARE AS
DIAGNOSTIC as is the Baermann

technique



Eggs, when seen, are 50 × 80

µm, thin shelled, colorless, and larvated



The larvae are 230

µm long with a distinct kinked tail

o

Both larvae and eggs may be visualized in the sputum and in washings from the trachea of an affected
dog


Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

3





THERAPY

o

Many drugs have been reported to be effective in treating lungworms



thiacetarsemide sodium, diethylcarbamazine, levamisole, fenbendazole, oral ivermectin, and
albendazole

o

Surgical removal is not recommended owing to the large number of nodules



Removal of a

large obstructing nodule may be potentially therapeutic in rare situations

Aelurostrongylus abstrusus



ETIOLOGY

o

A. abstrusus

is a common feline lungworm

o

In the United States, it is most common in the southern states




Indirect Transmission:

o

Eggs are deposited in alveoli or tissue. L1s hatch and are coughed up,
swallowed, and passed in feces

o

An intermediate host (snails or slugs) is required for development of l
arvae to infective L3s

o

Paratenic hosts (rodents, frogs, etc.) may become involved
b
y eating the intermediate host



It is possible that paratenic hosts
are the main route of infection

o

On being ingested, L3s enter the mucosa of esophagus, stomach, and/or intestine, and p
ass via the
blood to the lungs

o

Prepatency is 5
-
6 weeks.


Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

4




CLINICAL SIGNS

AND DIAGNOSIS

o

Although most infected cats remain well, infection can produce clinical signs that mimic feline
bronchopulmonary disease

o

Mature worms reside in the bronchioles



Inflammation of these small airways can result in cough, wheeze, and/or respirato
ry distress

o

Thoracic radiographs of parasitized cats may appear unremarkable and may demonstrate a diffuse
interstitial nodular and/or peribronchiolar pattern or sometimes an alveolar pattern

o

In endemic regions,
A. abstrusus

should be considered an importa
nt differential diagnosis for feline
“asthma,” especially in cats with outdoor exposure, which are more likely to ingest the mollusk
intermediate host of the parasite

o

Diagnosis is based on detection of larvae in either airway lavage samples or the feces vi
a Baermann
sedimentation

o

A very sensitive and specific diagnostic PCR using either feces or pharyngeal swab material has been
developed but is not currently commercially available




THERAPY

o

Fenbendazole (25 to 50

mg/kg PO q24h for 10 to 14 days),
ivermectin (300 to 400

µg/kg SC), and
selamectin (6

mg/kg applied topically) can each be used for treatment

o

Oral or inhaled antiinflammatory glucocorticoids may be useful during therapy, as may bronchodilators for
cats with increased respiratory effort

Crenosoma vulpis



ETIOLOGY

o

Dogs but not cats can be infected with
C. vulpis,

an airway nematode

o

Indirect infections follow ingestion of mollusk intermediate hosts

o

The infection is reported most often in the northeastern states of the United States and in ea
stern Canada
but also occurs in Europe

o

The parasite matures in the airways, where it produces larvated eggs that can be coughed out of the
respiratory tract and swallowed




CLINICAL SIGNS AND DIAGNOSIS

o

The majority of dogs infected with
C. vulpis

remain healthy but lower respiratory signs (e.g., cough) and
sometime upper respiratory signs (e.g., nasal discharge) can occur

Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

5


o

Diagnosis is accomplished by recognition of the immature parasites either on airway lavage or through
fecal Baermann sedimentat
ion or zinc sulfate centrifugal floatation techniques



THERAPY

o

Treatment usually involves administration of fenbendazole (50

mg/kg PO q24h for 3 days), but ivermectin
and milbemycin oxime (0.5

mg/kg PO, once) may also be effective

Eucoleus aerophilia



ETIOLOGY

o

This nematode respiratory parasite, also known as
Capillaria aerophilia,

has a worldwide distribution

o

The parasite infects the airway mucosa of both dogs and cats

o

E. aerophilia

becomes embedded in the tracheal and bronchial mucosa, sometime result
ing in
eosinophilic bronchitis



CLINICAL SIGNS AND DIAGNOSIS

o

most infections remain subclinical, chronic cough or even occasional respiratory distress may occur

o

As opposed to most lungworm infections
, fecal diagnosis is better accomplished by routine flotation
rather than Baermann technique

o

Airway lavage cytology may also aid identification of the double
-
operculated eggs similar to but smaller
than those of the intestinal whipworm
Trichuris vulpis


C
uterebrosis



ETIOLOGY

o

Cuterebriasis is caused by a fly called
Cuterebra



Cuterebra

are large non
-
feeding flies that lay eggs near animal burrows, nests, or vegetation

o

These opportunistic parasites do not seek out animals, but when an animal wanders by, the
eggs attach
and hatch in response to the host’s body heat



Infestation is most common in summer and fall

o

Infestations of the skin tend to occur around the head and neck because the animal has stuck its head
near a burrow that contains the eggs.



Once a larva

hatches, it can be licked and swallowed during grooming, enter the body via the
mouth or nostrils, or it may enter the body through an open wound



The larva causes a lesion in subcutaneous tissue



The host acts like an incubator



The larva opens a tiny breat
hing hole (a fistula) in the skin



It just lives there, it does not feed on the host



An advanced
-
stage larva is the size of the first joint of your thumb and is a light tan color



About a month after infestation, the
Cuterebra
larva crawls out of the skin an
d falls to the ground
and pupates as the life cycle begins all over again



The length of time it stays in the ground depends on seasonal factors

Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

6




CLINICAL SIGNS AND DIAGNOSIS

o

What pet owners typically see is the swelling at the air hole and matted hair from
the pet’s over
-
grooming

o

Cats often groom to the point of irritation

o

Sometimes the pet has pain at the site

o

Some sites become infected and pus can be seen

o

Several cats have been described with inspiratory dyspnea

o

Upon tracheoscopy,
Cuterebra

larvae were observed in the trachea, at or just cranial to its bifurcation

o

Diagnosis by visual inspection of the lesion



THERAPY

o

Successful treatment consisted of removal of the larva during tracheoscopy in one cat and by
thoracotomy and removal through a
tracheal incision

o

Removal of parasite



Parasitic pulmonary disease is caused by both lungworms and nonlungworms

o

Some intestinal worms, especially
Toxocara

(round worms) but also
Ancylostoma

(hookworms), undergo
pulmonary migration before the adult worm reaches its final destination in the intestine



Usually, pulmonary migration causes little disease and few (if any) respiratory signs



However, massive larval migration can result in both direct

and indirect inflammatory damage to
the lung, causing verminous pneumonia



Such profound infections typically occur in puppies who may present with cough and tachypnea



CBC is not often performed in young puppies with cough but eosinophilia would be
expecte
d



Fecal flotation may be negative because larval migration occurs before the mature worms
have reached the intestine

o

Empiric treatment is reasonable if pulmonary migration is suspected as a cause
of cough



Anthelmintics should be administered at least twice
, 2 weeks apart



A short course of an antiinflammatory dose of glucocorticoid may ameliorate severe cough but
should not be used before ruling out other causes of infectious pneumonia

o

Although intestinal worms migrate through the lungs on their way to a fin
al destination, for lungworms the
final destination is the respiratory tract



These parasites may reside primarily in the pulmonary parenchyma, in the airways, or both



Parasitic lung disease can be easily confused with other conditions such as bronchopneumo
nia,
eosinophilic pneumonia, asthma, pulmonary granulomatosis, or even pulmonary neoplasia



Unfortunately, intermittent fecal shedding of parasite ova or larvae after expectoration means that
fecal examination is an insensitive diagnostic method



High
-
dose
fenbendazole (50

mg/kg PO q24h for 10 to 14 days) or ivermectin are usually
used

o

Ivermectin must be used with caution in Collies and other breeds with a high
prevalence of MDR1 mutations



Although albendazole is an effective therapy for lungworms, it has a
greater potential for
bone marrow toxicity than fenbendazole





Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

7


Infectious Pulmonary Parenchymal Parasites

Paragonimus kellicotti



ETIOLOGY

o

The trematode lung fluke
Paragonimus kellicotti

infects dogs and cats

o

Found worldwide, in the United States lung
flukes are particularly endemic in the Great Lakes region, the
Midwest, and the South

o

As with most pulmonary parasites, an intermediate host is involved in transmission



Pets are infected after eating crayfish



The parasite migrates from the intestines into
the peritoneum, across the diaphragm,
and into the pleural space



Soon thereafter immature flukes invade the subpleural tissues, where they cause
eosinophilic and neutrophilic inflammation



Often, the parasites form bullae and cysts within the pulmonary pare
nchyma



The mature flukes have access through a series of communicating “tunnels” to the
bronchioles, allowing ova to eventually be coughed up and swallowed before fecal shedding




CLINICAL SIGNS AND DIAGNOSIS

o

Animals infected with
P. kellicotti

are usually well but may present with cough or even respiratory
distress

o

Rupture of cavitary pulmonary lesions can lead to hemoptysis or pneumothorax

o

Often the differential diagnosis is suspected when animals with respiratory signs have concurrent
eosinop
hilia or when it is based on radiographic findings



Although radiographic lesions are not uniformly identified, they can include nodular or cystic
lesions or bullae, especially involving the right caudal lung lobes

o

Serial CT from experimentally infected dog
s initially identified pleural effusion and a subpleural
ground
-
glass appearance along with linear opacities

Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

8




After 1 month, persistent peribronchial nodules, bronchial dilation, and cavitary changes were
observed

o

Ova can be demonstrated from either airway
lavage fluid or in feces

o

Fecal sedimentation techniques are preferred over other methods of fecal analysis for demonstration
of parasite ova





THERAPY

o

In addition to fenbendazole, praziquantel

(25

mg/kg PO q 8 hours for 3 days) has been successfully
used for treatment of
P. kellikotti

o

Efficacy of treatment should be assessed with repeated fecal examination for ova

o

Pneumothorax that results in respiratory embarrassment requires specific therapy

Filaroides



ETIOLOGY

o

Filaroides are relatively uncommon pulmonary parasites of dogs

o

Adult nematodes of both
Filaroides hirthi

and
Filaroides milksi

(a.k.a.
Andersonstrongulus milksi
)
species reside in the alveolar spaces and terminal bronchioles;
differentiation of these very similar
parasites is not necessary

o

Filaroides

has frequently been recognized as endemic in research dog colonies

o

The ovoviviparous parasite is transmitted directly via fecal
-
oral route allowing transmission between
an infected

dam and her pups, or between infected and uninfected pups

o

Repeat infection (autoinfection) of the host with larvae before they even leave the host is also
possible and increases the potential for “super” infections



CLINICAL SIGNS AND DIAGNOSIS

o

Dogs may re
main healthy while parasitized or may develop severe or even fatal disease

o

Severe disease is especially likely in young, small
-
breed dogs, immunosuppressed dogs, or dogs
with superinfections

o

Clinical signs, when they occur, may include cough and respirator
y distress

o

Diffuse bronchointerstitial and alveolar infiltrates result from granulomatous inflammation in reaction
to the dead or dying worms

o

Zinc sulfate centrifugation fecal flotation is used to identify larvae but lacks sensitivity due to
intermittent
shedding (a common feature of most lungworm infections)

o

Recognition of ova and/or larvae in airway lavage is an alternative method of diagnosis



THERAPY

o

A variety of anthelmintic treatments have been employed, but fenbendazole (25 to 50

mg/kg PO q24h
for 10

to 14 days) or ivermectin (0.4 to 1.0

mg/kg IV or SC) are used most often

o

An inflammatory reaction to dying worms may worsen disease severity shortly after treatment, a
complication that can be ameliorated by a short course of corticosteroids in antiinfla
mmatory doses

Other parasites of relevance to the lung

Dirofilaria immitis



ETIOLOGY

Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

9


o

D. immitis

is responsible for heartworm disease, an important cause of pulmonary and cardiac
pathology in temperate climates throughout the world

o

Although heartworm
infection of dogs has been well described for many decades, only recently have
we begun to understand heartworm infection in cats

o

The host
-
parasite interaction, clinical consequences, diagnosis, and treatment of
D. immitis

differ
greatly between dogs and c
ats ), but efficacious prophylactic mediations are readily available for use
in both species

Web Table



230
-
2



--

Comparison of
Dirofilaria immitis

Infection in Dogs vs. Cats
[66
-
68,327
-
331]



DOGS

CATS

Host
-
parasite
interaction







乡瑵ral⁨潳琮







P慲慳it攠e畲摥u⁶慲楡扬e⁢ 琠tf瑥t慮y
m慴ar攠e潲os⁰牥 敮琮







䵡瑵牥 w潲os⁰ rsis琠t
-
㜠y敡rs.







䵡瑵牥⁩湦散瑩潮 瑥t⁡ com灡湩敤⁢y
micr潦il慲敭i愮







Pr敶慬敮c攠v慲a敳 wit栠h敯杲慰gic⁲敧i潮.








Atypical⁨潳琮







P慲慳it攠e畲摥u⁴ypically‱
-
㌠w潲os.







䵡瑵牥 w潲os⁰ rsis琠t
-
㌠y敡rs.







䵡瑵牥⁩湦散瑩潮 v敲y⁲慲敬y⁡ c潭灡湩敤⁢y
micr潦il慲敭i愮







䱡rval⁦潲os 瑥t⁥ imi湡瑥t⁢y imm畮攠牥e灯湳攮







Prevalence of mature infection ≈10%
潦⁴ 慴ai渠n潧s
i渠n⁧ ve渠n敯杲g灨ic⁲敧io渮


Diagnosis







䑩慧湯sis 慴ar攠e湦散瑩潮⁳瑲慩杨瑦潲w慲搮







剥R潧ni瑩潮 潦 micr潦il慲楡 潮⁢l潯搠dm敡r爠
vi愠a潮c敮瑲慴a潮⁴散桮i煵e
攮e⸬.Kn潴os✠瑥'琬t
fil瑲慴ao渠n敳琩 潦瑥t⁡llows
di慧湯sis⸠
䵩cr潦il慲i愠are⁡ se湴ne慲ay i渠n湦散瑩潮, wit栠
low 睯wm⁢ r摥湳Ⱐ,r⁩渠no杳⁲散敩vin朠
桥慲aw潲o⁰牯灨yl慸is.







A湴i来渠牥n潧湩tio渠ni愠E䱉SA 潦f敲e⁥ c敬l敮琠
s敮si瑩vity 慮d⁳灥cificity⁦潲⁩湦散瑩潮 i渠摯杳⸠
A湴i来渠n散潭敳⁤ 瑥t瑡tle

≈5 months after
i湦散瑩潮.







T桯r慣ic⁲慤i潧ra灨s⁣慮⁢攠e畧g敳瑩v攠e畴u
湯琠tia杮潳tic ⁨ 慲a睯wm⁩湦散瑩潮⸠
剡摩潧ra灨s 瑥t 摥m潮s瑲慴a⁰牯 i湥n琠
灵lm潮慲y 慲瑥ay⁳e杭敮瑳Ⱐ,r瑥物慬⁴潲瑵潳ity
慮搠灲畮i湧,⁡ 搠d潭整emes⁲i杨琠v敮瑲ic畬慲a







䑩慧湯sis ⁩湦散瑩潮 摩ffic畬琮⁏t瑥t 愠a潭扩湡瑩潮
潦⁴ s瑳⁡牥⁲敱uir敤⁴漠o潮firm⁩湦散瑩潮⁩渠na瑳 wit栠
low 睯wm⁢ r摥渮







䵩cr潦il慲i愠ael摯m⁰牥 敮琮







S敮si瑩vity 潦⁅䱉SA 慮ti来渠n敳瑳⁩s low 摵攠瑯tlow
睯wm⁢ r摥測n慢se湣攠ef
a湴ng敮ic慬ly 摥t散瑡tl攠
fem慬攠睯rmsⰠ,r⁩mm慴ar攠睯rms⸠䡯.ev敲Ⱐ
慮瑩来n⁴ s琠t灥cificity is⁨i杨.







F敬i湥
-
s灥cific⁨ 慲aw潲o⁡ 瑩b潤y⁴ s瑳⁡牥
m潤敲慴敬y⁳e湳itiv攠e湤ayiss‱ ┠潲潲攠潦
i湦散瑩潮s.







F敬i湥
-
s灥cific⁨ 慲aw潲o⁡ t
ib潤y⁴ s瑳⁡牥
m潤敲慴敬y⁳p散ific⁡ 搠do湦irm ly 數灯s畲攠瑯t
Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

10




DOGS

CATS

enla
rgement. A variety of pulmonary
parenchymal abnormalities are also possible.







Echocardiography may demonstrate right
-
sided cardiomegaly, worms within the
pulmonary artery or right heart, or worms
within the right ventricular inflow tract.


parasite. They cannot confirm mature or active
infection.







Radiographic changes inconsistent, although
caudal lobar arterial enlargement and parenchymal

changes are sometimes identified.







Echocardiography may detect mature infection but
sensitivity and specificity are operator
-
dependent
(30%
-
100%). Useful when infection is suspected
despite negative ELISA antigen test.


Clinical
signs







Dogs remain well for prolonged periods during
infection.







When clinical signs do develop, the most
common are exercise intolerance and cough.







Right
-
sided congestive heart failure occurs
eventually in some untreated dogs.







Caudal caval syndrome is an uncommon
emergent complication of infection that occurs
when the adult worms obstruct the right
ventricular inflow tract. Caval syndrome
includes tricuspid murmur, intravascular
fragmentation hemolysis with hemoglobinuria,
right
-
sided congestive heart failure, and
disseminated intravascular coagulation.







Antigen
-
antibody complex deposition may
cause glomerulonephritis.







Rarely, aberrant migration leads to disease of
other organ systems (e.g., eyes, brain, spinal

cord, skin, liver).








Cats frequently remain well during
infection.







Cats may develop a syndrome
resembling feline asthma as a result of
larval infection without adult worm
burden (i.e., HARD).







Cats with mature worm burdens may
present with GI signs including
hypersalivation and vomiting or
respiratory signs including cough or
tachypnea.







Cats with mature worms may die
suddenly without prior clinical illness,
or may present with acute on
set
dyspnea and/or CNS signs.







Unlike dogs, right
-
sided congestive
heart failure is rare in cats.







Rarely, aberrant migration leads to
disease of other organ systems (e.g.,
eyes, brain, spinal cord, skin, liver).


Prophylaxis

• Chemoprophylaxis is extremely effective. Options
include ivermectin, milbemycin oxime, moxidectin,
and selamectin.

• As for dogs, chemoprophylaxis with the same
compounds is extremely effective.

Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

11




DOGS

CATS

Treatment







Adulticide treatment should be preceded

by
staging to identify comorbid conditions and
severity of disease.







Melarsomine dihydrochloride is the only
approved heartworm adulticide.







If not used beforehand, chemoprophylaxis
should be begun when adult infection is
identified. If
microfilaria are present, the dog
should be observed for anaphylaxis after the
first dose is administered.







Caval syndrome is treated via physical
removal of worms.







Complications of infection may require
specific therapy (e.g., treatment

of congestive
heart failure, treatment of glomerulonephritis).








Adulticide treatment in cats is not recommended
due to toxicity, lack of efficacy, and fatalities
associated with thromboembolism.







If not used beforehand, chemoprophylaxis

should
be begun when adult infection is identified.







Cats with bronchopulmonary disease may benefit
from corticosteroid therapy.







Bronchodilator therapy and oxygen may be useful
in cats with respiratory distress.







Surgical
removal of mature worms has been
described but entails risk.



Angiostrongylus vasorum



ETIOLOGY

o

Infection with this metastrongylid parasite of canids occurs in Europe, Asia, and Africa, as well as in
an endemic focus in Newfoundland, Canada

o

It has been dubbed “French heartworm” because, like
D. immitis,

the mature parasites reside in the
pulmonary artery, right heart, and pulmonary arterioles

o

Dogs are infected after consuming infected intermediate (i.e., mollusk) or paratenic

(i.e., frog) hosts



L3 larvae are liberated into the dog's intestine before eventually making their way to the
pulmonary vasculature



Ova from the mature worms are carried to the pulmonary capillaries, where they hatch



The L1 larvae then migrate into the al
veoli



The L1 larvae then migrate into the alveoli



Mollusks become infected through feces from the infected canid (foxes may be a reservoir
host), and the cycle is repeated when the intermediate host is then eaten by another canid



CLINICAL SIGNS AND DIAGNOS
IS

o

Infected dogs may appear healthy or have a range of clinical signs

o

The predominant syndromes associated with infection are respiratory disease related to an
inflammatory response to the parasite and a syndrome of bleeding diathesis



The cause of bleeding is poorly understood but may be related to a consumptive
coagulopathy initiated by the parasite, and bleeding may occur without respiratory signs



Neurologic signs have been reported in infected dogs as a consequence of central nervous

system hemorrhage

Medicine Rounds:
Parasitic pulmonary disease


January 13, 2012


Presented By: Kevin Kumrow

12


o

Severe pulmonary hypertension with resultant cor pulmonale and syncope are reported occasionally

o

Although cardiopulmonary disease related to thrombosing pulmonary arteritis can be severe and
even fatal, the most common findings are chron
ic cough and general unthriftiness

o

Unlike heartworm due to
D. immitis,

vascular changes are not appreciated on thoracic radiographs



Instead, some combination of bronchial, interstitial, and/or peripheral alveolar lung patterns is
described

o

Laboratory findi
ngs associated with infection may include anemia, eosinophilia, thrombocytopenia,
abnormalities of coagulation time, and often hypercalcemia

o

As for many pulmonary parasites, Baermann fecal examination is the diagnostic standard and
parasites may also be id
entified on airway lavage

o

Recently, a sensitive and specific
serologic antigen detection

test has been described



THERAPY

o

Appropriate diagnosis and treatment is generally associated with a good prognosis for recovery

o

The drug of choice for treatment of
A.
vasorum

is fenbendazole (25 to 50

mg/kg PO q24h 10 to 20
days), although other effective treatments (e.g., ivermectin [0.2

mg/kg SC each week for two doses],
milbemycin oxime [0.5

mg/kg orally each week for 4 weeks], imidacloprid 10%/moxidectin 2.5% spot
-
o
n solution, levamisole) have been described

o

Despite recovery of most dogs after treatment, posttreatment reactions including dyspnea, ascites,
and sudden death have been observed



Update: New Content

Pulmonary Artery Thrombosis in Experimental Angiostrongyl
us vasorum Infection Does Not Result in Pulmonary
Hypertension and Echocardiographic Right Ventricular Changes

Kranjc

A,

Schnyder

M,

Dennler

M,

et al

J Vet Intern Med

2010;

24(4):855
-
862



Summary




Dogs experimentally inoculated with Angiostrongylus
vasorum develop severe pulmonary parenchymal
lesions and arterial thrombosis at the time of patency.



Six healthy Beagles experimentally inoculated with A. vasorum had thoracic radiographs and arterial blood
gas analyses performed 8 and 13 weeks postinocul
ation (wpi) and 9 weeks posttherapy (wpt).
Echocardiography was done before and 2, 5, 8, 13 wpi and 9 wpt. Invasive pulmonary artery pressure (PAP)
measurements were obtained 8 wpi. Two untreated dogs were necropsied 13 wpi and 4 treated dogs 9 wpt.



All do
gs had patent infections at 7 wpi and clinical respiratory signs at 8 wpi. Moderate hypoxemia (median
PaO2 of 73 and 74 mmHg) present at 8 and 13 wpi had resolved by 9 wpt. Echocardiographically, no
evidence of PH and no abnormalities in cardiac size and f
unction were discernible at any time point. PAP
invasively measured at 8 wpi was not different from that of control dogs. Severe radiographic pulmonary
parenchymal and suspected thrombotic lesions at 13 wpi were corroborated by necropsy. Most
histopatholog
ic changes had resolved at 9 wpt, but focal inflammatory, thrombotic, and fibrotic changes still
were present in all dogs.



In experimentally infected Beagles, pulmonary and vascular changes induced by A. vasorum are reflected by
marked radiographic changes

and arterial hypoxemia. These did not result in PH and echocardiographic
changes in cardiac size and function