[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 11 The Trematodes
Male
Female
Katayama fever is a systemic hypersensitivity
reaction to the schistosomulae migrating through
tissue. Rapid onset of fever, nausea, myalgia,
malaise, fatigue, cough, diarrhea, and eosinophilia
occur 1 to 2 months after exposure.
Although rare in chronically exposed persons, it
is common in people new to endemic areas, such
as tourists and travelers.
A number of associated conditions have been
identified in patients with Schistosoma. For
example, those infected with S. japonicum or S.
haematobium are also at risk of suffering from
nephrotic syndrome. Similarly, there appears to
be a connection between S. haematobium infection
and bladder cancer. In addition, S. mansoni
and S. japonicum may be associated with repeated
Salmonella infections.
Average length: females — 2 cm, males — 1.5 cm
FIGURE 11-12 Schistosomes in copula.
Clinical Symptoms
Asymptomatic. It is believed that most chronic
Schistosoma infections contracted in known
endemic areas remain asymptomatic. It is interesting
to note that a brown hematin pigment,
similar to the pigment seen in persons infected
with malaria, is present in the macrophages and
neutrophils (microphages is not used very often)
of these patients.
Schistosomiasis, Bilharziasis, Swamp Fever. The
first symptom experienced by most symptomatic
persons infected with Schistosoma is inflammation
at the cercaria penetration site. Symptoms
of acute infection include abdominal pain, fever,
chills, weight loss, cough, bloody diarrhea, and
eosinophilia. Painful urination and hematuria
may also occur in persons infected with S. haematobium.
The development of necrosis, lesions,
and granulomas is common and occurs in the
area(s) infected with the parasite. Obstruction of
the bowel or ureters, as well as secondary bacterial
infections and involvement of the central
nervous system and other tissues, may also result.
Treatment
Praziquantel is the drug of choice for the treatment
of schistosomal infections. Oxamniquine is
only used for S. mansoni. The antimalarial artemisinins,
artemether and artesunate, have proven
effective for schistosomal infections but, in areas
endemic for malaria, concern for resistance by
Plasmodium may limit their usefulness. Surgery
may be necessary for patients in whom obstruction
has occurred.
Prevention and Control
Older methods of preventing schistosomiasis
included proper human waste disposal and
control of the snail population, primarily their
breeding areas, prompt diagnosis and treatment
of infected persons, the avoidance of human
contact with potentially contaminated water, and
educational programs for the inhabitants of
known endemic areas. Current focus is on anthelminthic
chemotherapy with praziquantel because
of its low cost, few side effects, and rapid results.
The World Health Organization (WHO) has recommended
the following measures: mass treatment
of everyone in a community in which there
is a high prevalence and/or high risk of schistosomiasis
(7 of 15 or more children test positive),