Page 2566 - Hematology_ Basic Principles and Practice ( PDFDrive )

Chapter 158 Hematologic Aspects of Parasitic Diseases 2289

are declining. Preventing malaria transmission through blood transfu- is increasingly seen in association with HIV infection, where infection
sion requires comprehensive, regularly reviewed, and effectively rates in HIV-infected people may be as high as 10%.
implemented guidelines for donor deferral and laboratory testing. VL is caused by a number of species of the Leishmania donovani
Even the best strategy is a compromise, and medical laboratory staff complex. 138,139 In the Mediterranean region and areas in the Middle
should be aware of the rare but potentially serious possibility of fever East and Central Asia through to China, Leishmania infantum pre-
after transfusion that could be caused by malaria. dominates, whereas L. donovani is more prevalent in India. Leishmania
tropica is a less common cause of VL in these areas. Throughout their
range in the Old World, parasites are transmitted by the female
VISCERAL LEISHMANIASIS sandfly of the Phlebotomus genus. Leishmaniasis is caused by different
parasites and vectors in the New World, where Leishmania chagasi
Leishmaniasis is a generic term for infection by 30 or so species of and Leishmania amazonensis are transmitted by the Lutzomyia genus
the obligate intracellular parasites from the genus Leishmania. Visceral of sandfly.
leishmaniasis (VL), or kala-azar, presents with a wide spectrum of Leishmania organisms are present in blood, and so the disease can
systemic and hematologic features. be transmitted by blood transfusion, as a sexually transmitted disease,
as a congenital infection, by needle sharing for intravenous drug
abuse, or within a laboratory by intradermal inoculation of L. don-
Epidemiology ovani promastigotes. 140,141 Very few cases of leishmaniasis have
occurred as transfusion-transmitted infections in Europe or North
VL occurs in all countries bordering the Mediterranean Sea and America, with under 10 cases in infants or immunocompromised
across the Middle East, including Saudi Arabia and Yemen. Indian patients reported over the last 50 years. In endemic areas, this problem
VL occurs in the eastern regions of India (particularly Assam, Bengal, represents a much greater but unquantified risk.
Bihar, Uttar Pradesh, Tamil Nadu, and Sikkim) and in Nepal and
Bangladesh. African kala-azar is endemic in Kenya, Ethiopia, and the
Sudan and sporadically elsewhere in tropical Africa. In the Americas, Parasitology
VL occurs in foci across Mexico, Central America, Colombia, Ven-
ezuela, Guyana, Brazil, Bolivia, and northern Argentina (Fig. 158.7). Leishmania amastigotes live and multiply within macrophages by
The total burden of disease is difficult to estimate but significant. binary fission. They are round or ovoid bodies, approximately 2 to
Leishmaniasis burden is endemic in 88 countries, with 200,000 to 3 µm in diameter. Occasional rupture of cells allows invasion of
400,000 new cases of VL per year, with the vast majority occurring uninfected monocytes and macrophages by free forms. Sandflies
in India, Bangladesh, Nepal, Northern Sudan, and northeastern ingest amastigotes within macrophages from blood or skin. In the
137
Brazil. VL is associated with poverty and undernutrition in endemic insect’s stomach, free amastigotes multiply and divide asexually,
areas, particularly in the hyperendemic foci of the southern part of becoming elongated and developing flagella as metacyclic promasti-
the Sudan and the Ganges river basin. In the Mediterranean area, it gotes. Within 2 weeks, such infective forms migrate through the

Key
L. chagasi
L. infantum variants
L. donovani

Fig. 158.7 EPIDEMIOLOGY OF VISCERAL LEISHMANIASIS (VL). VL caused by parasites of the
Leishmania donovani–Leishmania infantum complex occurs in the Mediterranean littorals, the Middle East,
and adjacent parts of the former Soviet Union, the Sudan, East Africa, the Indian subcontinent and China,
and South America (Leishmania chagasi). An arid, warm environment provides ideal ecologic conditions for
the breeding of many species of sandfly. Zoonotic kala-azar from L. infantum and L. chagasi is commonly
associated with dry, rocky, hill country, where cases are typically scattered. In India, L. donovani is essentially
an anthroponosis. This type of kala-azar may occur in severe epidemic fashion, as can kala-azar in the Sudan.