skin scraping

1. Collection and Examination of Skin Scraping to Study
Stephanofilaria assaensis
Introduction:
Skin scrapes are one of the most common dermatologic diagnostic tests. This
relatively simple and quick test can identify many types of parasitic infections.
Although not always diagnostic, the relative ease and low cost makes it an
essential test in a dermatological minimum data base. This is a simple and
effective technique to identify many types of parasitic skin infestations.
Skin of cattle is often affected by Stephano-filarial infection in the Indian
subcontinent and is commonly known as ‘Humpsore’. Nine species of the
Stephanofilarial parasites have been reported from different parts of the world,
but only Stephanofilaria assamensis has been reported as the causal agent of
hump sore in eastern Bangladesh. Though the name ‘Hump sore’ implies
appearance of sore in the hump region but the stephanofilarial dermatitis also
occurs in other parts of the body. The disease is transmitted by the fly Musca
conducens and is prevalent in tropical countries.
Objective:
 Skin scrapes are collected to examine parasitic infections such as
Stephanofilariasis, mange, mite etc
 To diagnose skin disease and to identify the causal agent
 To study the morphology of adult parasite, microfilaria, eggs anf larvae
 To study the life cycle of parasites such as Stephnofilaria assamensis
 To treat animals properly
 Research purpose
Instruments and appliances:
a) Scalpel
b) Scissors
c) Microscope
d) Glass slide
e) Cover slip
f) Mineral oil

2. g) Antiseptics solution
h) Poly bag
i) 10% KOH solution
General principles of skin scrapings collection and examination:
 A dulled scalpel blade or medical spatula is used to collect the material
from the skin surface.
 If these are to be reused on other animals then they need to be washed
and disinfected to prevent the potential spread of infectious diseases.
 If the area to be scraped is covered with hair then clipping is better to
access the skin surface.
 Put some mineral oil on the skin surface of the area to be scraped to
facilitate collection of the scraped sample material.
 Hold the blade or spatula perpendicular to the skin surface and scrape in
the direction of the hair.
 Be sure to pick up the entire scraped sample on the edge of the blade or
spatula. Don’t leave the material you just worked so hard to scrape on the
skin where it does no one any good.
 Transfer the sample to a drop or more of mineral oil on a glass slide and
be sure to wipe everything off the blade onto the slide. Again, if it stays
on the blade you can’t examine it.
 Spread the material around in the mineral oil to get an evenly distributed
sample.
 Potassium hydroxide 10% is added to the collected material to digest
unwanted tissue.
 Apply a cover slip and examine with the 10x microscope objective.
When examining a skin scraping versus a cytology slide, keep the sub-
stage condenser down to maximize contrast for better visualization of
parasites. This is especially important for small life stages such as
Demodex eggs.
 Occasionally, higher magnification may be needed but 10x is adequate
for most of the common skin parasites.
Deep skin scrapings:
Deep skin scrapings are used to examine for parasites that reside in the hair
follicles, especially Stephnofilaria assamensis, Demodex canis and Demodex cati.
Again, all of the general principles apply. Additionally,
 Since these mites are usually easier to find than some of those mentioned

3. above, smaller areas can be examined. However, multiple areas on the
body may still need to be examined such as the face, head, feet and other
lesional areas for Demodex.
 The two most important additional steps are
I. squeeze the area to be scraped to help extrude the mites from the
follicles to the surface and
II. Scrape with moderate pressure until blood oozes from the
superficial capillaries.
 In hard to scrape areas such as around the eyes, gently plucking hairs and
examining the shafts in mineral oil may help visualize mites.
 In scarred and edematous areas such as the feet and in certain breeds such
as Shar peis and Shih Tzu’s it may be impossible to find follicular mites
without a skin biopsy.
Superficial Skin Scrapings:
Superficial scrapings are used to examine for parasites that reside on or near the
skin surface such as Sarcoptes, Notoedres, Cheyletiella, Otodectes and chiggers.
All of the general principles apply. Additionally,
 Because some of the superficial mites are in small numbers and may be
hard to find, do a larger area of skin using several strokes with mild to
moderate pressure without the need for surface capillary bleeding.
 Do several areas and more than one slide for the hard to find parasites.
 Remember to put some mineral oil directly on the skin surface since dry
debris is hard to pick up and transfer to the microscope slide.
Obsevation:
Characteristics of Stephnofilaria assamensis:
Adult parasites and microfilariae are recovered from skin scrapings impression
smears of tissue sections.
Adult parasites:
 The adult worms appear as small, slender and whitish
 The male parasites ranged from 3 to 5 mm and females 7 to 11 mm
 Under light microscope, a crown like cephalic structure is noticed; at a

4. short below there is a row of cephalic spines
 Except the cephalic structures, the cuticle is finely serrated at regular
intervals throughout the body length and the serrations became gradually
faint towards the posterior region
 In males the body is almost of uniform thickness except the anterior end
and posterior end, which is slightly bent ventrally
 Whereas, both the ends of females remain tapered, but the thickness
increased gradually towards the posterior part and the tail is straight
Microfilaria:
The centrifuged sediment and extractives of tissues in physiological saline
revealed slender microfilaria.
 Anterior end is blunt and the posterior end is pointed
 Examination of impression smears revealed that most of the microfilariae
are sheathed; only a few are unsheathed
 Above to the nerve ring, the cephalic portion is narrow and ends
somewhat rounded; on the other hand towards the posterior end, the
microfilaria are narrow and tapered posteriorly
 Most of the microfilariae were in open ‘C’ posture or coiled, while
undulating forms and straight forms of the microfilariae were also
observed in few cases
 The length of the microfilaria varies between 120-150 μm
Adult parasite Microfilariae

5. Potential vectors fortransmissionofthe infectionin cattle:
In Bengaladesh Musca conducens and Stomoxys calcitrans flies feed on the
lesions of stephanofilaria. On dissection, unsheathed crescent shaped infective
larvae were recovered from the Musca conducens flies only and no larvae from
Stomoxyscalcitrans.
In North Bengal plenty Haematobia sp. and a few Stomoxys calcitrans were
caught from the body of the host. On dissection of both the flies and thorough
examination revealed a few larvae in the thorax and salivary gland of
Haematobia sp. but not in Stomoxys calcitrans.
Life cycle:
 Egg containing larvae are laid into the subcutaneous tissues by adult
worms
 Microfilaria is ingested by adult Musca conducens as they feed on the
open lesions
 Microfilaria migrate to mid gut and move towards the proboscis during
which they moult twice to become L3
 Development to stage L3 takes about 2-3 weeks and final host become
infected when the flies deposit larvae on the injured tissue of hump
region
 The larvae escape and invade the surrounding tissues and become adult
by 6-12 months and begin to reproduce again

6. Pthogenesis:
The gross and histopathological changes in different stages of stephanofilarial
dermatitis of cattle were almost same irrespective of the site involved. The
diameter of the gross lesions varied from 2 to 10 cm. Exudation of serum and
oozing of blood leading to crust formations, acanthosis, proliferation and annular
zones of leukoderma surrounding the lesions were noticed. Raw eroded ulcerated
red areas were observed at around the junction of skin and hoof. Scab, dry crust
formation and acanthosis were common. In dewclaw region, lesions with
excoriation proliferation and complete loss of hairs and tumorous growth up to
hen’s egg size were quite common.
Treatment:
6-10% Trichlorphan (organophosphate) in petroleum jelly of castor oil applied
daily or alternately after removal of crusts and necrotic tissues cures after a week.
Sumithion and Coumaphos are also used with success.
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