Page 2576 - Hematology_ Basic Principles and Practice ( PDFDrive )

Chapter 158 Hematologic Aspects of Parasitic Diseases 2299

meta-analysis has suggested that PCR is not more sensitive than increased. Surveys of blood donors in France have shown seropositiv-
ELISA for detection of T. cruzi in chagasic patients. The recom- ity of T. cruzi can be detected by PCR in about half the seropositive
mendation is to use two serologic tests, which may be supplemented donors and remain viable for at least 20 days, surviving cryopreserva-
by PCR-based assays in the immunocompromised patient, in whom tion and thawing. T. cruzi has been reported to be transmitted after
seroconversion may not occur in patent infection. 226 organ transplant 240,241 and after blood transfusion in seven patients
who were immunosuppressed. 242–246
Donors can be excluded by a medical questionnaire eliciting
Treatment obvious symptoms of acute or chronic disease. Prospective studies
have shown these questionnaires would miss many infected
249
The detailed treatment of Chagas disease is beyond the scope of this donors, 247,248 including those infected congenitally. Nevertheless, in
chapter. Treatment of the acute, intermediate, and chronic phases Europe screening for anti–T. cruzi antibodies is targeted at at-risk
requires expert supervision because parasitologic cure is achieved in blood donors who originate from an endemic area, donors with
only half the cases and monitoring progress requires specialist testing mothers originating from such an area, and individuals who have
and evaluation and where necessary treatment of end-organ damage. lived in or traveled to endemic areas. In France the seropositivity in
The current and potential future chemotherapy 227–229 have recently these selected donors was 1 : 32,000. 250
been reviewed. In the United States new tests have been requested by the Food
Nifurtimox is a synthetic nitrofuran that inhibits pyruvic acid and Drug Administration to combat this threat. A radioimmunopre-
synthesis by inhibition of lactic dehydrogenase. It is given for 30 to cipitation assay (RIPA) is the most sensitive method to detect anti–T.
251
120 days at 3 to 5 mg/kg three times per day. The most serious side cruzi antibodies, although RIPA cross-reactivity has been reported
252
effects are peripheral neuropathy, mental disturbance (including in patients with VL. It is unsuitable for mass screening, however.
psychosis), and hemolytic anemia associated with G6PD. An ELISA based in a concentrated extract of excretory-secretory
Benznidazole is widely available in Latin America and is given at antigens from either Brazil or Tulahuen strain T. cruzi trypomastigotes
5 mg per kilogram of body weight per day for 60 days. Severe (TESAs) 253,254 had an overall sensitivity of 100% and specificity of
hematologic complications are common, and bone marrow depres- more than 94%, and a prototype T. cruzi lysate–based ELISA has
sion is a serious side effect. Thrombocytopenia may be severe, and been developed that appears to be 97.7% sensitive and 100%
neutropenia may progress to agranulocytosis. Other serious complica- specific. 251
tions include photosensitivity, neuropathy, and weight loss. 230 It is only to be hoped that sensitive screening tests are consistently
Supportive therapy is required for heart failure and acute menin- applied to reduce transmission of Chagas disease by blood products
goencephalitis. Surgery may be required for alleviation of esophageal in endemic and nonendemic countries. On a more general note, it is
and chronic dysfunction. In the absence of effective or simple therapy, encouraging that the initiatives to control T. cruzi infection across
control of triatomine bugs and an improvement in the housing stock Latin America are showing real evidence of success. 213,255
are essential to prevent and control disease.
BABESIOSIS
American Trypanosomiasis as a Transfusion-
Transmitted Infection Babesiosis is an intraerythrocytic infection caused by parasites from
the order Piroplasmida and the family Babesiidae. It was first observed
Chagas disease may occur as a transfusion-transmitted infection and as causing parasitic inclusions in erythrocytes of cattle in Romania
256
represents a real threat to the safety of the blood supply in endemic by Victor Babes at the end of the 19th century. The infection is
areas. It is estimated that 1.5% to 50% of contaminated units cause zoonosis transmitted by hard-bodied ticks and causes fever and
infection in recipients, a wide range that may reflect the stage of hemolytic anemia. Several distinct Babesia spp. cause disease in dif-
infection in the donor, the type and processing of the component, ferent geographic areas. 257,258
and the immune status of the recipient. 231 There are two well-defined Babesia species that cause human
In endemic areas, seropositivity is high, reaching 50% in some infection. Babesia microti is a parasite of small rodents in the north-
areas of Bolivia and 1% to 2% in major areas in Brazil. Control of eastern United States and is spread by nymphs, larvae, and adult
blood transfusion–transmitted infection is part of the World Health forms of the hard-bodied ixodid ticks (Ixodes dammini). Infection of
Organization strategy for control of Chagas disease. 232–234 Serologic the white-tailed deer by ticks allows multiplication and spread of the
screening, tests using synthetic peptide antigens, or a mixture of infected ticks. Infections can be transferred to humans by all forms
recombinant antigens to detect anti–T. cruzi antibodies in chronically of the tick after prolonged feeding. The infection is therefore most
infected blood donors are more than 95% sensitive. 235,236 These common in people vacationing or working in forested areas of the
serologic tests, replacing those based on crude antigens, have allowed northeastern United States. The northeastern US offshore islands of
improved coverage of screening of blood donors throughout Latin Nantucket, Martha’s Vineyard, Block Island, and Shelter Island are
America and in the United States. 237,238 foci of the disease, but it also occurs in eastern states, particularly
It is possible to treat blood with gentian violet (0.25 g/L for 24 Connecticut, Rhode Island, Delaware, and New York State, as well
hours at 4°C) or with methylene blue to kill circulating organisms. as upper Midwestern states. Hundreds of cases have been recorded
It has also been shown that amotosalen or riboflavin plus ultraviolet since the first identified case in 1969. Visitors and workers in endemic
A photochemical inactivation technology is effective in inactivating areas should avoid tick bites by using appropriate clothing and
T. cruzi in platelet concentrates and plasma. 238,239 In addition, pro- repellents.
phylactic benznidazole can be given to immunosuppressed patients In Europe, Babesia divergens and the morphologically indistin-
receiving blood products in endemic areas. guishable parasite Babesia bovis are transmitted to humans by ticks
Outside Latin America, Chagas disease is an occasional cause of (Ixodes ricinus) from cattle. Fewer than 50 cases have been recorded.
transfusion-transmitted infection, mainly in immunosuppressed European cases of B. microti and Babesia canis infection have also
patients. It is possible that minor infections are not recognized in been reported.
healthy individuals. Clearly the high rates of seropositivity in indi- A handful of cases of infections with Babesia duncani in the
viduals from endemic areas suggest that recent immigrants may easily western United States have been reported. These organisms are
transmit the disease. morphologically indistinguishable from B. microti but are distin-
In the United Sates the overall seropositive rate among blood guished by molecular methods. The MO1-type piroplasm caused
donors is 1 : 250,000, with local incidence rates reaching 1 : 7500 or illness in an index case in Missouri in 1992, and the WA1-2 and
231
greater in Los Angeles and Miami. These rates are probably under- CA1-5 piroplasms caused disease in eight cases reported in Washing-
estimates because immigration from endemic areas has recently ton State and California. 259,260 A further B. microti–like organism, B.