Download (direct link):
Hypergammaglobulinemia, which has been attributed to polyclonal B cell activation, can be pronounced. Globulin levels as high as 9g/dl have been reported, and there is reversal of the albumin:globulin ratio. Elevated liver enzymes
Fig. 13-8 Visceral leishmaniasis due to L. (L.) chagasi in north-eastern Brazil. The child is wasted and has massive hepatosplenomegaly
and bilirubin are observed in some patients. Petechiae, ecchymoses and bleeding may develop late in the disease as a consequence of coagulopathy and thrombocytopenia.
Although the natural history of untreated visceral leishmaniasis has not been fully characterized, it progresses to death in the vast majority of cases. Secondary bacterial and viral infections are common (Andrade et al., 1990). Pneumonia, septicemia or measles are often the immediate cause of death. Even with chemotherapy, the mortality rate approaches 10% in the Sudan and Brazil (Evans et al., 1985; Jeronimo et al., 1994).
Visceral Leishmaniasis in Patients with HIV Infection
Visceral leishmaniasis is a well-recognized opportunistic disease in persons with AIDS. They can present in the classical manner with fever, constitutional symptoms, splenomegaly and hepatomegaly, but atypical presentations
are common (Datry et al., 1990; Montalban et al., 1990; Sendino et al., 1990; Abbas et al., 1992; Matheron et al., 1992; Chenoweth et al., 1993; Rosenthal et al., 1995; Alvar et al., 1997). Splenomegaly may be absent. Amastigote-infected macrophages may be encountered in the lungs, pleura, oral mucosa, esophagus, stomach or small intestine. Some persons present with aplastic anemia due to bone marrow involvement (Grau et al., 1989). Asymptomatic leishmanial infection has also been reported in persons with AIDS (Condom et al., 1989). Visceral leishmaniasis usually develops late in the course of HIV infection. The prognosis has been poor even with antileishmanial chemotherapy, but most of the reported experience antedates the introduction of highly active antiretroviral therapy.
A small group of American troops who served in the Persian Gulf War developed low-grade fever,
PRINCIPLES AND PRACTICE OF CLINICAL PARASITOLOGY
malaise, fatigue and lassitude as a consequence of visceralizing L. (L.) tropica infection (Magill et al., 1993). Although splenomegaly was observed in some, it was not massive. None of them progressed to classical visceral leishmaniasis. The diagnosis was confirmed by culturing L. (L.) tropica from bone marrow aspirates.
Post-kala-azar Dermal Leishmaniasis
Post-kala-azar dermal leishmaniasis develops after therapy in a subset of persons with visceral leishmaniasis in Africa and India. It is characterized by macular, papular or nodular lesions on the face, trunk or extremities that may be mistaken for leprosy. Amastigotes are present in macrophages in the lesions. In African post-kala-azar, dermal leishmaniasis lesions usually appear at the end of therapy or within a few months and persist for several months. In India they can appear up to 2 years after treatment and persist for many years. Persons with post-kala-azar dermal leishmaniasis may serve as reservoirs of infection in those areas.
DIAGNOSIS Parasite Identification or Culture
The diagnosis of leishmaniasis is suggested by the clinical syndrome and a history of exposure in an endemic area. It is confirmed by identifying amastigotes in tissue specimens or by isolating promastigotes in culture (Pearson et al., 1990). When biopsies, aspirates or touch preparations are stained with a Wright-Giemsa preparation (e.g. Diff-Quik), the cytoplasm of amastigotes appears light blue, the nucleus is eccentrically located and red, and the kinetoplast appears as an intensely stained, small, red rod (Figure
13.4). Amastigotes must be differentiated from Histoplasma capsulatum, which are of similar size but lack a kinetoplast.
Leishmania spp. can also be isolated in culture. Biopsies from persons with cutaneous leishmaniasis, splenic or bone marrow aspirates from those with visceral leishmaniasis, or other specimens can be cultured in Novy, Nicolle and MacNeal’s (NNN) medium, Schneider’s insect
medium or one of several alternatives to which fetal calf serum is added. Cultures are incubated at 22-26°C. Motile promastigotes are easily visualized in a hemocytometer at x400 magnification, but it may take several weeks for the concentration to reach detectable levels. Specia-tion of cultured promastigotes by isoenzyme analysis is available at a number of World Health Organization reference laboratories (Kreutzer et al., 1983). Species-specific monoclonal antibodies are also available (Grimaldi and McMahon-Pratt, 1996). PCR assays using genus- or species-specific probes are under development, but they are currently available only in research laboratories (Rodriguez et al., 1994; Nuzum et al, 1995).
The diagnosis of cutaneous leishmaniasis can be confirmed by identifying amastigotes in touch preparations or tissue, or by isolating promastigotes in culture. The sensitivity of these assays decreases in older or healing lesions. Parasite isolation and speciation is particularly helpful in persons acquiring cutaneous leishmaniasis in Latin America, since infection with L. ( V.) braziliensis and some other Leishmania ( V.) spp. associated with mucosal disease require systemic treatment, whereas infection with L. (L.) mexicana or other species that do not disseminate to the mucosa can be followed expectantly if the lesion is small, cosmetically unimportant or healing.