Diagnosis of Dog and Cat Parasites by Fecal Examination

1
Diagnosis of Dog and Cat Parasites by Fecal
Examination
2
.Ancylostoma egg. As one of the most commonly
encountered parasites of dogs and cats, hookworm
eggs are often used as a reference point for
size, much as the red blood cell is used in
hematology. A. caninwn, A. braziliense and A.
tubaefonne are about the same size and
appearance. (60 x 40u).
3
  Uncinaria stenocephala . Eggs of the
northern hookworm are distinguished by a larger
size (72 x 45). The size difference is readily
apparent in mixed hookworm infections, but
measurements are necessary for identification of
single species infections. Uncinaria is less
pathogenic than A.. caninwn.
4
Hookworm larvae and eggs . Very rapid development
time leads to the emergence of the hookworm L1
stage from eggs in as 1ittle as one day under
good conditions. The L3 develops in as 1ittle as
3 days. Larvae rather than eggs are often found
in fecal samples over 24 hours old which have not
been refigerated. Fresh fecal samples are
therefore necessary to prevent confusion with
other parasites such as Strongyloides, which is
shed as first-stage larva in dogs and cats.
5
Hookworms in situ At necropsy, hookworms are
small but grossly visible ( 1 2 cm.) on the
mucosal surface and in gut contents. Contents
may be examined in washings in a pan with a dark
background.
6
  Ancylostoma caninum transmission. This diagram
outlines the developmental and transmission
patterns of A. caninum. The oral, percutaneous,
and transmarnmary routes are the most common
source of infection. Larvae can be found for up
to 20 days in the milk of the bitch
7
Clinical feature of A. caninum. Numerous larvae
may be acquired by nursing pups (primarily in the
milk) with resulting .kennel anemia.. When larvae
are L4s (10 d) they begin sucking large volumes
of blood (0-01-0.2 m1/day) before eggs are
detectable in the stool. Immediate treatment is
indicated in conjunction with supportive therapy
(transfusion, fluids, hematenics, etc.). By the
time a pup is 6 months old it will have built a
fair immunity to severe or fatal clinical effects
of hookworms (assuming prior exposure).
8
Less pathogenic hookworms. Other hookworms of
dogs or cats suck only one- tenth to
one-hundredth the blood volume of A caninum and
are consequently of less clinical significance.
Transmammary or prenatal infection have not been
documented.
9
Cutaneous larval migrants. A. braziliense is well
adapted for percutaneous infection. After
accidental exposure of man, larvae do not mature,
but migrate in the skin for prolonged periods,
leading to .cutaneous larvae migrans.. Other
Ancylostoma species may penetrate the human skin,
leaving a whelp, but do not migrate.
10
Trichuris vulpis (alongside hookworm egg).
Whipworms are common in dog ( very rarely seen in
cats as T. campanula) over 3 4 months of age.
The egg is footbal shaped, reddish brown and has
a rounded polar cap at either end ( 80 x 38 u).
Like ascarids, they are quite resistant and may
survive for months after becoming infective in
204 weeks on the ground.
11
Trichuris characteristics. Clinical typhlitis
results from heavy Trichuris infections leading
to malaise, anorhexia, abdominal pain, anemia and
debility . Diarrhea is often scant, quite pungent
and .fatty. in appearance.  
12
Clinical Trichuris infection in site caecum
Thw whip-like anterior end is threaded through
the mucosa. Trichuris is a blood feeder.
13
Toxocara canis ova T. canis is a common
parasite of dogs between 4 weeks and 6 months of
age and is often found in very large numbers.
Note the dark nuclear mass and the rough
protective wall typical of ascarids ( 90 x 75 u).
14
Toxocara canis key characteristics Ingestion
of eggs, which are infective after 2 3 weeks
on the ground, leads to a hepatic-tracheal
migration pattern in young dogs and a somatic
migration pattern in older dogs with subsequent
prenatal transmission to pups by bitches.
Trans-colostral infections are negligable for T.
canis. visceral larva migrans or ocular larva
migrans may occur in children who eat dirt
contaminated with infective T. canis eggs.
15
Toxascaris leonina egg (80 x 67 u) Note the oval
shape, the lighter color, the incompletely
filled egg and that the egg wall is rough on
the interior wall. By contrast Toxocara eggs are
rounder, darker, fill the egg and the wall is
rough on the outside of the wall
16
Toxascaris leonina characteristics. Toxascaris is
first found in older pups or kittens because of
the long prepatent period. Complex migration does
not occur after infection. Toxascaris leonina is
far less common in this area than Toxocara. Some
local practitioners call it the northern
roundworm..
17
Toxocara cati egg. . T. cati eggs are very
similar in appearance to T. canis.
18
Toxocara cati characteristics. The life cycle
patterns of T. cati are similar to T. canis ,
but the prepatent period is longer and
transmammary versus transplacental transmission
is the primary mode of infection of young
kittens. Paratenic hosts may provide an important
source of reinfection of older cats with either
Toxascaris leonina or T.cati visceral larval
migrans in man may occur with Tcati as well as
T. canis .
19
Heavy ascarid infection. Young animals with this
level of infection might die of debility ,
diarrhea and vomiting with subsequent dehydration
and acid-base inbalance
20
Cervical alae. Ascarids may be identified as T.
leonina or Toxocara canis if necessary by the
presence of wing-like cervical alae at the
anterior end. T. cati has even broader alae,
leading to an arrow-head. appearance.
21
Physaloptera-cephalic collar .Physaloptera spp.
is an uncommon parasite of the stomach of dogs
and cats that resembles ascarids in gross
appearance. Ascarids are often found in the
stomach at necropsy. Physaloptera is found with
its head embedded in the mucosa and has a
prominent collar-like cephalic alae.
22
Physaloptera eggs. Physaloptera eggs, like most
spirurids, are small in size (54 x 32 u),
embryonated, and have a relatively thick wall.
23
Physaloptera characteristics. Physaloptera is
rare in dogs and cats, but in parts of the
Midwest prevalence may reach 15 .It is
transmitted by various arthropod I.H. (eg.
beetles, crickets) or by paratenic hosts
24
Spirocerca lupi egg. Spirocerca is another
spirurid which in recent years has been found in
dogs only very rarely in the Southeastern U.S.
Eggs are somewhat smaller than Physaloptera (34
x 13 u) and more rectangular , but have the
thick wall and embryonated state typical of
spirurids.
25
Spirocerca characteristics. The rare infection
with Spirocerca often leads to dramatic clinical
effects. Both the life cycle (dung
beetle-paratenic hosts) and migration pattern in
the canine hosts are complex. Esophageal wall
granulomas, vertebral spondylitis, and aortic
aneurisms occur. Fibrosarcoma or osteosarcoma may
be triggered with accompanying hypertrophic
pulmonary osteroarthropathy.
26
Strongyloides 1st stage larva . Strongyloides
steroralis appears in fresh feces as first stage
larvae and this finding is usually sufficient for
diagnosis. Note size in relation to hookworm egg.
Old stools may contain hookworm first stage
larvae which are difficult to distinguish from
Strongyloides .While larvae will float with sugar
or NaNo3 solution and are initially live and
motile, they quickly become crenated and
wrinkled, making them difficult to distinguish
from artifacts. A diagnosis of Strongyloides can
be confirmed by culturing feces in moist
vermiculite or charcoal and recovering typical
L3s (among the rhabditifarm larvae and adults)
by Baermannization examination of portions of the
culture daily for up to 10 days. Strongyloides
third stage larvae have a long filariform
esophagus which extends over 113 the body length
and they have a split tail (Caution L3s are
infective for man). Developing hookworm larvae
will have a short rhabditiform esophagus or a
short filariform esophagus if development has
progressed to the 3rd stage (usually 2 ½ - 3
days).
27
Strongloides characteristics. Both free-living
and parasitic generations occur in the very rapid
Strongyloides life cycle (10 days -2wk). Young
animals in crowded, moist conditions are most
susceptible. An effective immunity may reduce
clinical cases that allow carriers. (Note
Strongyloides tumaefaciens has been documented in
cats from Louisiana and Texas). TBZ is effective
at 25 mg/kg Sill 5 days with a repeat regime in 5
days.
28
Filaroides first stage larvae. Another
larvae shed in the feces of dogs is that of
Filaroides spp. of the lungworm group. It can be
distinguished from Strongyloides by the notched.
or S-shaped tail
29
Filaroides osleri lesions. Adult worms of
Filaroides osleri are found in wart- like nodules
at the bifurcation of the trachea. Larvae are
coughed up and shed in the feces
30
Filaroides milksi. And F. hirthi. Two other
Filaroides species occur in the lung paraenchyma
of dogs and also shed larvae in feces. F. hirthi
larvae are not notched and are most sensitively
found by flotation They are too sluggish for
Baermann sedimentation recovery .
31
Filaroides characteristics. Filaroides is
often asymptomatic but may cause a dry , chronic
cough and debility .It is most often seen in
outdoor dogs such as hounds. Ivomec, oxfendazole
and fenbendazole are reported effective in
treatment.
32
Capillaria aerophilia egg The fox lungworm
egg is easily confusible with Trichuris vulpis at
fecal examination. It is differentiated from
Trichuris by its smaller size (59-80 x 30-40 u),
lighter yellow color, a rougher wall and more
flattened. polar caps. Differentiate from C.
putorii a non-pathogenic intestinal species of
cats with smaller eggs. In dogs and cats,
differentiate also from C. boehmi, a cause of
nasal capillarlans adults reside in the nasal
mucous membranes in the ethmoid area.
33
Capillaria aerophilia characteristics C.
aerophila occurs in the trachea, bronchi and
bronchioles of the dog, cat and fox. Chronic
cough and debility may occur. Fenbendazole or
Albendazole (25 mgk/g Bill for 21 d) and Ivomec
at 3x the recommended dose are reported to be
effective treatments
34
Capillaria aerophila x-section Note adult
worms and surrounding eggs.
Adult worm
eggs
35
Aelurostrongylus abstrussus. This lungworm
of cats also sheds notch-tailed larvae in the
stool. They may be recovered with flotation
media, but as with other larvae, they lose
motility rapidly and become crenated. Baennann
recovery is preferrable.
36

• abstrussus gross lesion
• Cats develop chronic respiratory disease with
  this parasite which is self-limiting after a
  period of several months. The parasite is found
  in the deep lung parenchyma, often in diffuse,
  multifocal, subpleural nodules as seen here.

37

• asbtrussus characteritics.
• Larvae are found at maximum numbers during the
  first 2-3 months of infection and gradually drop
  off as immunity and clinical recovery occurs.
  Transmission is by garden snails or slugs or
  paratenic hosts. FBZ or Ivomec treatment is
  reported to be effective.
•  

38
Trematodes
Unlike trematodes of cattle in which
sedimentation techniques must be used, most fluke
eggs of dogs and cats can be recovered by fecal
flotation, although sedimentation is preferable.
Trematodes often have a distinct geographic
distribution limited by the presence of the snail
or second intermediate host in a particular area.
39
Paragonimus kellicotti egg. The eggs of this
lung fluke of dogs and cats is endemic in
Louisiana because of the prevalence of the
crawfish second intermediate host. Characteristic
eggs with a collar at the operculated end may
be recovered by fecal flotation (75-118 x 42-67
u).
40
. Paragonimus gross pathoogy. Adult flukes
are usually found in pairs in subpleural nodular
cysts which communicate with the bronchiolar tree
for egg release. Cysts are seen as signet rings
only 1/100 of the time.
41
Paragonimus characteristics Infection is
diagnosed by the chronic cough, clinically, by
the characteristic radiographic picture, and by
recovery of eggs by flotation or tracheal
washings. RX FBZ or ABZ (25 mg/kg Bill, 21
days), Praziquantel (25 mg/kg TID, 3 days).
42
Nanophytes salmincola. This intestinal fluke
(note very small size in relation to intestinal
mucosa here) and the disease agent (s) it carries
(Salmon-poison complex) are endemic to the
Pacific Northwest.
43
Nanophytes characteristics Salmon
poisoning disease is similar to distemper in
clinical appearance in many respects. An
enteritis from pylorus to anus occurs and
Nanophytes eggs can be recovered 5- 7 days after
infection during the early clinical disease.
Highly fatal unless treated early with
antibiotics. A generalized reticulo-endothelial
disease occurs characterized by reticular
hyperplasis of lymphoid tissues. Diarrhea is
scant and yellow and later may become bloody.
Bloody diarrhea. precedes death in fatal cases.
44
Nanophytes eggs are recoverable by flotation at
onset of disease (prepatent period 7d) are
light brown in color, rough shelled and have an
indistinct operculum at one end. (97 x 6Om)
45
Platvnosomum concinnum ( Fastosum) egg. This
liver fluke causes lizard poisoning in Florida
and the Caribbean. The egg is small (34-50 x
20-35 u), brownish and contains a mature
miracidia when passed.
46
Platynosomum characteristics. The life
cycle involves isopod (sowbug, pillbug) and
lizard (Anolischameleon) intermediate hosts. The
disease may lead to fatal liver disease. Rx
Praziquantel 25-50 mg/kg. .
47
Metorchis conjunctis characteristics This liver
fluke occurs in dogs in Canada and also has a
small, brownish embryonated egg.
48
Heterobilharzia americanum pathology This
fluke causes canine schistomiasis and has
been reported in Louisiana and Texas in dogs and
in wild animals. Flukes reside in the mesenteric
(seen here), portal or hepatic veins. RX
praziquantel 50 mg/kg.
49
Heterobilharzia -liver lesions Eggs are
released in the blood, and although most pass to
the intestine, penetrate the wall and are shed in
feces, some eggs are swept to the liver where
they cause micro-granulomas and eventually
cirrhosis.
50
Heterobilharzia ova Eggs are large (87 x 70
u) oval, and are difficult to diagnose because
the egg contains a mature miracicium that hatches
immediately on contact with water. Diagnosis is
by Formalin-ethyl acetate sedimentation or by use
of saline sedimentation ( to prevent hatching)
51
Alaria spp. Egg These large eggs of Alaria (122
x 76m) may be found in incidental finding by
fecal flotation, or adults may be found
incidentally in the intestine at necropsy. There
is new evidence that some Alaria spp can be
transmitted via the tranunmammary route to
letters.
52
.Alaria adults at necropsy Alaria is
non-pathogenic. Adults have a characteristic
waist unlike the oval shape of most other flukes.
53
Alaria characteristics.
54
Amphimeres pseudofilineus Has been diagnosed in
Louisiana cats several times in recent years. It
is a fluke inhabiting the bile ducts, gall
bladder , and sometimes the pancreatic ducts and
can be carcinogenic. Transmission is by
metacercariae ingested on fish. Asian species
infect dogs and man as a major public health
problem. Note small size and fully developed
miracidium in eggs. This is typical of most other
dog and cat liver flukes.
55
Acanthocephalan Oncicola canis adult. The
only acanthocephalan found in dogs is Oncicola
canis .Note the retractable spiny proboscis
characteristic of the group
56
Oncicola canis in situ coyote intestine. Rare
infection in dogs and other canidae are thought
to be acquired by ingestion of armadillos. Other
aspects of the life cycle are unknown. Eggs are
characteristic (65 x 45 u). (See Sloss )
57
Cestodes Cyclophyllidean tapeworms Characterist
ic of the tapeworms that occur in dogs and cats
are listed here. Eggs of cyclophyllidian
tapeworms all have a hexacanth embryo. All
parasites listed have a similar appearing egg
(taeniid) except for Dipylidium which produce egg
packets.
58
Taenia egg. These small eggs vary somewhat in
size (about 30-40 u) but are basically similar in
appearance for Taenia, Multiceps or Echinococcus.
Note the nearly round shape, the hexacanth embryo
and the radiating striation of the egg wall.
59
  Dipylidium caninum This parasite of dogs and
cats produces eggs similar to Taenia but retains
them in packets formed by pinching off the
uterus around several eggs.
60
Feces with segments of tapeworms Fecal
flotation is not a reliable way to diagnose
infection with cyclophyllidian tapeworms since
eggs are normally retained in gravid segments
which are shed from the posterior end of the
strobila. Infection is often diagnosed by finding
crawling, motile segments in the feces, on the
perinium of the host, or in the surroundings.
When segments dry on the perineum they lead to
rice grains which are also diagnostic.
Recovered segments or rehydrated rice grains
should be squashed between two slides and
examined for eggs to identify Dipylidiwn vs
Taenia.
61
Adult tapeworm identification. Adult worms which
are passed after worming with certain vermifuges
or found at necropsy may be identified by
characteristics of the scolex, the neck, the
segments and the strobila. Worms are best
examined after relaxing in cold water overnight
in the refrigerator .
62
Dipylidium caninum A heavy infection is shown
here in the small intestine
63
D. caninum. Note the shape of the segments (thus
the name cucumber tapeworm) and the small size of
the scolex and neck. Segments have two genital
pores.
Close-up of proglottid
64
D. caninum scolex. Note the four suckers and the
retractable, armed rostellum.
65
Taenia pisiformis in situ small intestine of a
dog. Note the larger, more robust appearance of
Taenia as compared to the fragile, lacey
appearance of Dipylidium.
66
Taenia segments. Note the square shape and
single lateral genital pore.
67
Taenia scolex. Taenia has four suckers and a
row of hooks (armed) on the scolex. Different
species of Taenia or Multiceps may be
differentiated by scolex morphology (i.e. hook
shape) or segment morphology after staining.
These procedures are usually impractical for
practitioners but specimens may be sent to a
diagnostic laboratory for identification.
68
Taenia pisiformis cvsticerci. This tapeworm is
acquired by ingestion of rabbits with peritoneal
cysticerci
69
Taenia hydatigena Is acquired by ingestion of
very large peritoneal cysticerci in sheep, cattle
or pigs
70
Multiceps serialis Is contracted by ingestion
of a Coenurus in the subcutaneous tissues of
rabbits (often the hock area). The multiple
scolices each produce a separate tapeworm.
71
Coenurus cerebralis. This coenurus has a
predilection for the CNS of sheep where it
causes gid. Ingestion of sheep brains leads to
Multiceps multiceps infection of dogs.
72
Taenia taeniaformis strobilocercus in rat
liver Cysticercus Pascio1arls is found in the
liver of rodents. Note strobilocercus after
removal from connective tissues cysts in liver.
Ingestion leads to Taenia taeniformis , the
no-neck tapeworm of cats.
Rat liver
Extracted from liver
73
Echinococcus. This tapeworm is rarely found in
dogs in the U.S. (especially in sheep raising
areas. Hydatid cysts are found in the liver,
lung or CNS of a variety of intermediate hosts,
including man.
hydatid cyst
adults
74
Pseudophyllidean tapeworms and Mesocestoides
characteristics. These tapeworms have
similarities to both flukes and cyclophyllidian
tapeworms.
75
Spirometra egg Pseudophyllidian tapeworm eggs
resemble fluke eggs with an operculum for
escape of the ciliated coracidium into water.
Spirometra mansonides is apparently more common
in Louisiana than thought, probably because of
the availability of water environments for
completion of the life cycle. (Water flea
-rodent -cat or dog). Spirometra eggs float well
and are almost identical in size to hookworms
but smaller than Paragonomus, probably leading
to many overlooked infections. Close
examination reveals a more diamond shape than
hookworms and an operculated end.
Pseudophyllidian eggs are continously shed by
individual segments of equal maturity (segments
are seldom shed).
76
Plerocercoid in subcutaneous tissue of a mouse.
Rodents serve as the second intermediate host
after swallowing infected cyclops.
77
Diphyllobothrium latum egg D. latum has been
described from dogs and cats as well as man,
although rare in the U.S. Eggs are more oval
than Spirometra. (70 x 45 u) and a posterior
knob is present opposite the operculated end.
78
Diphyllobothrium latum proglottid Pseudophyllidi
an tapeworm segments are of nearly uniform
maturity , are square or wider than long and
have a central genital pore.
79
D. latum scolex. Note the two cleft-like
bothria which serves as the hold- fast organ
for pseudophyllidian tapeworms. D. latum
tapeworms often attain a length of several feet.
Adult Spirometra are much smaller, thick
tapeworms.
bothria
bothria closeup
80
Intestinal Protozoa Isospora canis oocysts
Four Isospora species occur in dogs and two
occur in cats. Unsporulated oocysts (shown here)
are passed which become infective in about two
days. Isospora spp. are a clinical problem
mainly in young pups or kittens. Infections are
se1f-limiting and a good immunity develops with
age and exposure.
81
Coccidiosis of Dogs and Cats characteristics.
Species of Isospora that infect dogs or cats can
be differentiated by size. Toxoplasma oocysts may
be passed for approximately two weeks by infected
cats. Any oocysts of the size range of Toxoplasma
should be considered to be Toxoplasma for
handling purposes. Besnoitia, Banunondia, and
Sarcocystis are not pathogenic in the final host.
I. canis and I. felis are in the 30-40 u range,
I. ohioensis, I. bu"owsi, I. neorivolta and I.
rivota are in the 20-30 u range, and I. bigemina,
Sarcocystis, Besnoitia, Hanunondia, and
Toxoplasma are in the sulfas (eg albon), furadex
and recently, aprolium or decoquinate (Deccox).
Treatment is often after the fact and only act as
coccidiostats on new infections or by virtue of
their antibacterial effect. Supportive therapy
until the disease runs its course is indicated.
Immunity usually protects against future clinical
infection levels. Clinical Isospora infections
usually have sufficient oocyst numbers to be
picked up easily by direct smear.
82
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84
Sporulated oocyst Isospora felis . In 2-3
days coccidia have sporulated (two sporocysts
for Isospora
85
Size comparison of Isospora felis to
Ancylostoma (also I. rivolta)
Isospora
Ancylostoma
86
Size comparison of Feline Coccidia Isospora
felis (F), Isospora rivolta Sarcocystis (C) and
Toxoplasma gondii ('I') are shown here for size
comparison. Although some feel they can
differentiate Toxoplasma and Sarcocystis on
morphology, this is difficult and not practical
for practitioner to attempt with an ordinary
microscope
87
. Toxoplasma lung impression smear Acute
Toxoplasma infections can be sometimes diagnosed
by impression smears of lungs, lymph nodes,
brain, or other organs at necropsy or by biopsy
ante-mortum. Note banana shaped organisms here.
88
Giardia canis. In young pups or kittens
Giardia infections may cause chronic diarrhea.
In clinical cases large numbers of Giardia cysts
can be found on direct smears of feces. Iodine
staining should be done (with Lugol's solution)
to make them a more visible brownish color (as
seen here) rather than clear.
Giardia cysts
89
Giardia trophozoite Smears of fresh diarrhic
stools may show trophozoite of Giardia which are
easily seen because of their motility. Duodenum
or intestinal washescan be used to diagnose
Giardia because they are more easily seen as
motile trophozoites ( falling leaves motility).
Trophozoites encyst within a few minutes outside
the host or in the posterior intestinal tract.
90
Giardiosis characteristics
91
Trichomonas (stained trophozoites) Although
controversial, Pentatrichomonas has been
incriminated as a cause of diarrhea in young
puppies. A fresh direct smear is needed for
diagnosis since organism does not encyst and
loses its characteristic motility (jerky, spiral).
92
Trichomonas characteristics
93
Cryptosporidium spp. Is a newly recognized
coccidian important in AIDS patients. While
calves can transmit to man, it is unclear whether
significant numbers of cases occur in dogs and
cats to be important. The organism is ubiquitous
in low numbers in some water sources. It is an
emerging disease. Note the small size 4 6 u,
and the characteristic refractile body that is
best found by phase microscopy after Sheathers
Sugar flotation concentration. Differentiate
from yeasts by differential staining with Kinyons
acid-fast satin
Acid-fast stain
Phase contrast
94
Balantidium( trophozoite) Rarely dogs can
become infected ( via pig source usually) with
Balantidium. Usual diagnosis is by finding
motile ciliated, large trophozoites in direct
saline smears.