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210 Manual of basic techniques for a health laboratory
The primary stage is characterized by a painless genital ulcer (syphilitic chancre),
sometimes with enlargement of the lymph nodes in certain regions of the body. The
chancre heals spontaneously, even when untreated.
In some patients the disease progresses to the secondary stage.
The secondary stage results in:
— skin rash
— mouth ulcers
— genital warts
— generalized enlargement of lymph nodes.
The tertiary stage is very rare and is characterized by central nervous system involvement
and cardiac disease.
Secondary or tertiary syphilis may be transmitted to a fetus in utero (congenital
syphilis).
Yaws
Yaws is caused by a non-venereal treponeme (Treponema pertenue) and occurs in
humid tropical climates. It is characterized by granular papillomas on the skin.
T. pallidum and T. pertenue are delicate, tightly-coiled spirochaetes measuring 6–
12mm ¥ 0.2mm. They are indistinguishable under the microscope.
It is necessary to inspect samples suspected of being infected with spirochaetes by
dark-field microscopy as they do not stain easily for viewing by transmitted light.
5.6.1 Materials and reagents
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Microscope with dark-field attachment
Microscope slides
Coverslips
Gloves
Gauze
Sterile lancet or scalpel
● Sodium chloride, 0.85% solution (reagent no. 53).
Fig. 5.25 Collecting a chancre
specimen
5.6.2 Method
Collection of specimens
Important:
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Wear protective gloves for this procedure.
The chancre area should be clear of any ointment before attempting to collect
the specimens.
1. Collect the chancre specimen with gauze moistened with sodium chloride
solution.
2. If there is no obvious serous fluid, gently scrape the edge of the ulcer
with a sterile lancet or the flat edge of a scalpel blade (Fig. 5.25). Do not
draw blood.
3. Compress the ulcer gently with a gauze pad.
4. Using a coverslip, collect a drop of the serous exudate and invert it immediately
onto a slide.