Download Diagnosing Internal Parasites Power Point Presentation

Parasitology
Sample Collection and Handling
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
Parasite Detection
• Parasites infect the oral cavity, esophagus,
stomach, small and large intestine, and other
internal organs
•
•
Detected through microscopic examination of feces
Life stage found in feces
• Eggs, oocysts, larvae, segments (tapeworms), and adult
organisms
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
2
Collection of Fecal Samples
• Fresh samples are best
• If cannot be completed within a few hours
• Should be refrigerated or mixed with 10%
formalin
• Older samples – the appearance of eggs,
oocysts, or other life cycle stages may be
altered due to parasite development
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
3
Small Animal Fecal Samples
• Several methods
• Owner collection immediately after
defecation
• Stored in disposable container
• About 1 g (thimble-sized) is needed
• Labeled properly
• Collected directly from animal in hospital
• Gloved finger or fecal loop
• Fecal loop used for direct smear – small amount
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
4
Samples
• Sample should be as fresh as possible
• Label – client name, date of collection, species,
animal identification
• Examine samples within 24 hours
• Precautions
•
Wear gloves and protective outerwear
• Prevents contamination of samples
• Ensures personal health
•
•
Wash gloves frequently with soap and water
Clean and disinfect work areas and equipment
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
5
Records
•
•
Maintenance of good records are important
Records should include:
•
•
Identification information
•
Procedures performed
•
Results
Should also include:
•
•
•
•
•
•
•
•
Adequate history
Clinical signs
Duration of signs
Medications given
Environment
Vaccinations
Stocking density
Number of animals affected
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
6
Equipment
•
Microscope is the most reliable method of detection of
parasitic infections
•
•
•
•
•
•
•
•
Binocular microscope with x10, x40, and x100 objectives
Calibrated ocular micrometer
Stereo microscope is also helpful
Glass slides
View sample systematically
x10 objective to start
Many parasites in the same plane as air bubbles or at
the edge of the coverslip
Once a parasite is located, examine at higher
magnification
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
7
Evaluation of Fecal Specimens
• The choice of test to be performed is dependent
on clinical signs and patient history
• Begin with a gross examination of the sample
•
•
•
•
•
•
•
Consistency
Color
Presence of blood
Mucus
Odor
Adult parasites
Foreign bodies
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
8
Direct Smear
• Simplest
• Requires minimal equipment
• Allows for visualization of trophozoite
stages of protozoal parasites – Giardia
• Not adequate examination
• Disadvantages
• Small sample size
• Debris may be confused with parasitic
material
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
9
Direct Smear (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
10
Fecal Flotation
• Based on differences in specific gravity of
life cycle stages of parasites
• Flotation solutions have a higher specific
gravity then common ova
• Ova float to surface
• Fluke eggs have a higher S.G. and sink
• Too high an S.G. creates a plug of debris
that traps parasites, obscuring them from
view
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
11
Fecal Flotation (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
12
Fecal Flotation (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
13
Centrifugal Flotation
• Similar to flotation except once mixed the
sample is strained to remove excess debris
• Requires a tabletop centrifuge
• More sensitive than simple flotation
• Recovers more eggs and cysts in less time
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
14
Centrifugal Flotation (cont.)
• Giardia
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
15
Fecal Sedimentation
• Used when suspected ova are too large
to be recovered with standard flotation
• Fluke ova
• Laborious technique
• Most fluke eggs do not float or they are
distorted by flotation solutions, making
them difficult to recognize
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
16
Fecal Sedimentation (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
17
Cellophane Tape Preparation
• Often used to recover ova from Oxyuris –
pinworms and tapeworms
• Tape wrapped around a tongue depressor
with adhesive side out
• Animal’s tail raised and tongue depressor
pressed firmly against the anus
• Tape then removed and applied to a slide
with a small amount of water
• Examine microscopically
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
18
Baermann Technique
• Used to recover larvae from fecal
samples
• Requires the construction of a Baermann
apparatus
• Large funnel, tubing,
and collection tube
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
19
Baermann Technique (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
20
Baermann Technique (cont.)
• Routinely performed on feces of domestic
animals when lungworm infections are
suspected
• Fresh samples collected rectally
• In dogs and cats, Baermann technique is
used when Strongyloides are suspected
• Zoonotic potential
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
21
Miscellaneous Fecal Examinations
• Some parasites produce intestinal bleeding
•
•
Evident by frank blood in feces or darkened feces
Some intestinal bleeding can only be identified with
chemical testing
• Occult blood testing
• Many kits available
• Identify the presence of hemoglobin
• Vomitus can also aid in diagnosis of
parasites
• Toxocara canis
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
22
Miscellaneous Fecal Examinations
(cont.)
• Fecal culture
• Used to differentiate parasites whose eggs
or larvae are not easily distinguished by a
fresh fecal sample
• Because the life cycle, pathogenicity, and
epidemiology of some species differ,
identification may be necessary for proper
treatment and control
• May need an experienced helminthologist
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
23
Fecal Culture
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
24
Miscellaneous Fecal Examinations
(cont.)
• Modified McMasters technique
• Provides an estimate of the number of eggs
or oocysts per gram of feces
• Used mainly in livestock and horses
• Originally adapted from a technique used in
people infected with hookworms
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
25
Modified McMasters Technique
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
26
Staining Procedures
• Stains may be used to recognize certain
structural characteristics of trophozoites and cysts
• Lugol iodine and new methylene blue commonly
used with direct smear
•
•
Do not preserve the slide
Help with identification
• If protozoal parasites cannot be identified on
direct smears
•
Fecal smears with suspected trophozoites can be
dried and stained with Diff-Quik or Wright or Giemsa
stain and sent to a diagnostic laboratory
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
27
Staining Procedures (cont.)
• Acid-fast staining is used to identify
Cryptosporidium sp.
• Cryptosporidium is a parasite of the intestinal
tract of many animals including humans
• Diff-Quik stain can be used to aid in
identification of Isospora sp.
• Intestinal mucosal scrapings
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
28
Summary
• Methods to examine fecal specimens
include gross and direct microscopic
examinations
• Other examinations include fecal flotation,
centrifugal flotations, and sedimentation
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.
29