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96 CHAPTER 4

If left untreated, the condition worsens and leads to well as transmission from a pregnant mother to the fetus,
death within weeks to months. occurs in rare instances. The reservoir hosts are most
Symptoms of those with West African trypanoso- likely wild game animals, particularly antelope, other un-
miasis include the development of a chancre, usually in a gulates (joint-footed), and domestic cattle.
slightly shorter time than in East African trypanosomia-
sis (1 to 2 weeks rather than 1 to 4 weeks) after the tsetse Laboratory Diagnosis
fly bite. Other symptoms occur several weeks later than
the East African strain, and include a fever, rash, swelling Diagnostic measures are similar for West African and
around the eyes and hands, severe headaches, fatigue, East African trypanosomiasis. Trypomastigotes in blood,
and painful muscles and joints. Some people develop lymph fluid, lymph node aspirates, and direct wet mounts
swollen lymph glands at the back of the neck. Weight are effective forms for identification. Centrifugation often
loss occurs as the illness worsens. Infection of the CNS leaves the organisms in the buffy layer (WBCs and plate-
also causes personality changes as does the East African lets) of a blood sample, where they are effectively con-
variety, characterized by irritability, loss of concentration, centrated and can be stained with Giemsa stain for the
confusion, slurred speech, seizures, and difficulty with presence of parasites. In patients with CNS involvement,
communicating and walking. As the common name im- CSF may be used to find the organisms. Some serologic
plies, a number of patients sleep during the day but con- techniques are designed for screening for the two strains
versely have trouble sleeping at night. Without treatment, of the organism but antibody detection by serological
the illness gets worse and results in death several months methodology has extreme sensitivity and specificity that
to years following the infection. West African trypano- may be too unpredictable for clinical decisions, provid-
somiasis usually runs a longer disease course than that ing false positive results in some instances.
found in the East African trypanosomiasis.
Treatment and Prevention
Life Cycle
Early patient management is vital for West African
The life cycle of both T. b. rhodesiense and T. b. gambiense trypanosomiasis. Avoiding CNS involvement greatly
in man is similar, with the Glossina vector transmitting the increases the prognosis for one infected by the organ-
organisms for both strains. Transfer of the organisms from ism. Some medications that are effective in the hemo-
host to host occurs when an infected tsetse fly who has taken lymphatic stage, in particular pentamidine isothionate
a blood meal from an infected mammal injects metacyclic usually cures the Gambian variety. In later stages with
trypomastigotes from its salivary gland into the skin tissue CNS involvement, the “blood-brain barrier” effectively
of its intended host. The parasites enter the lymphatic sys- prevents the medication from reaching the brain. Con-
tem and pass into the bloodstream and into the CSF if the trol, management, and avoidance of the tsetse fly is the
disease runs its course. Inside the host, they transform into most effective measure for preventing transmission of
bloodstream trypomastigotes and are carried to other sites the disease. Clearing of moist breeding grounds and
throughout the body. They reach other blood fluids (e.g., drainage of swampy areas helps to control the numbers
lymph, spinal fluid) as they are circulated and continue re- of flies and therefore minimizes the potential for trans-
production by means of binary fission. These trypomasti- mission. Travelers to endemic areas should wear deep
gotes then leave the midgut of the fly and are transformed but bright colors, avoiding pastels, and use bed nets
into epimastigotes. The epimastigotes reach the fly’s sali- and insect repellent.
vary glands and continue multiplication by binary fission in
preparation for infecting another host.
LYMPHATIC FILARIASIS

Disease Transmission Primarily three species of microfilarial parasites infect
the lymphatic system of the human host. But other sys-
Transmission of the disease is through the bite of an in- tems such as the circulatory system and related tissues
fected tsetse fly, of the two species of the genus Glossina. may also become involved. The three species that are
Blood transfusions and organ and tissue transplants, as considered as lymphatic filariforms are: Wuchereria