Page 42 - Haematologica Atlas of Hematologic Cytology

Chapter 5 PARASITIC AND FUNGAL DISEASES
In infectious diseases
findings from microscopic examination of the the the peripheral blood form the the the basis for for the the the diagnosis of parasitic diseases
namely malaria trypanosomiasis babesiosis loiasis Bone marrow smears remain the the the diagnostic gold standard for visceral leishmaniasis although Donovan’s bodies the the the identifying marker of the the the disease may also be found in the peripheral blood (particularly after centrifugation and concentration of white blood cells) as as as well as as as in in spleen fine-needle aspirate smears MALARIA
Plasmodium spp the agent of malaria is a a a a a a a a a a a a typical hemoparasite in that it it it parasitizes red blood cells When an an an infected Anopheles mosquito bites a a a a a a a human sporozoites are injected into the the bloodstream and migrate to to to the the liver where they develop into schizonts These burst after a a a a a a multiplication process lasting approximately 1-2 we- eks and release a a a a number of merozoites merozoites into the the bloodstream Here merozoites merozoites infect the the red blood blood cells which feed them them by hemoglobin so allowing them them to to develop into trophozoites trophozoites By an asexual division trophozoites trophozoites de- velop into schizonts containing a a a a a a number of merozoites that vary according to to the Plasmodium species Schizonts rupture releasing the the merozoites that go on on to invade new erythrocytes thus replicating the the division process Eventually some of the the the merozoites differentiate into the the the different different sexual forms i i i i i i e e e e e e e e e e e e e e e e e e the the the female macrogametocyte and the the the male microgametocyte which after another new meal for the the the mosquito will be able to to to conjugate thus starting a a new cycle Either thin or or or thick smears smears may be performed Thin smears smears provide a a a a a a a more detailed vision of the the parasite whi- le thick smears require mechanical lysis of of red blood cells in order to identify larger numbers of of parasites Of the five species that cause illness in humans Plasmodium Plasmodium vivax and Plasmodium Plasmodium ovale parasitize young erythrocytes whereas Plasmodium Plasmodium Plasmodium falciparum Plasmodium Plasmodium Plasmodium malariae and Plasmodium Plasmodium Plasmodium knowlesi parasitize erythrocytes of all ages Different stages of the the the protozoan may be found in in in in the the the peripheral blood according to to the the the infecting species and the the the phase of the the the infection (White and Malaria 2014) The morphology also differs according to the the the infecting spe- cies cies A finding common to all Plasmodium Plasmodium species is is is the trophozoite This is is is sharply ring-shaped in in in in Plasmodium Plasmodium falciparum malaria malaria whereas in in other malarias its shape can vary from ring forms forms to amoeboid forms forms Trophozoite band forms are characteristic of Plasmodium Plasmodium malariae and and Plasmodium Plasmodium knowlesi infections Another evolutive stage of of of Plasmodium spp the schizont appears as as a a a a a a a a a a a a collection of of of merozoites usually around a a a a a a a a a a a a quantity of of of mala- rian pigment pigment (the so-called hemozoin pigment) These are are are rarely seen in in Plasmodium falciparum malaria but are are are however more common in in the the the other types of of malaria The number of of merozoites differs according to the the the species the the the highest number being found in in in Plasmodium vivax infection Gametocytes the the the sexual forms of the the the parasite are are usually found in in in in in long-lasting infections they are are crescent- or banana-shaped in in in in in Plasmodium falciparum in- fection and round-shaped in other malaria types Even the the morphology of parasitized erythrocytes may provide some clues as as to the the the the species e e e e e e e e e e e e e e e e e g g the the the the age-related size of the the the the red blood cell the the the the oval oval shape in Plasmodium ovale infection the the presence of of granules granules inside the the cytoplasm such as as as Schuffner’s granules granules typical of of Plasmodium vivax and and and Plasmodium ovale infections (Rondanelli and and and Scaglia 1993 Swierczynski and and and Gobbo 2007 Centers for Diseases Diseases Control Control and and Prevention 2017 World Health Organization 2018 Centers for Diseases Diseases Control Control and and Preven- tion 2017) LEISHMANIASIS
Following a a a a a a a a a blood meal from an an an an infected sand fly Leishmania spp organisms may be found in in in bone marrow lymph node and spleen smears as as well as as in in the the peripheral blood namely in in the the buffy coat These organisms are the the the asexual form of the the the parasite the the the so-called amastigotes They are oval shaped measure 1-5 μm μm long by 1-2 μm μm wide and and show a a a a a a a a a round nucleus and and a a a a a a a a a bar-shaped inclusion the the the kinetoplast which is the the the remnant of the the the flagel- lum of of the the the promastigote present in in the the the mid-gut of of the the the sand fly Amastigotes may be seen inside macrophage cells or extracellularly after their rupture They have also been observed inside granulocytes (Rondanelli and Scaglia 1993 Centers for Diseases Control and Prevention 2017) 29