SPOROZOA

• Plasmodium


  A genus of parasites that cause malaria
• Babesia


  A genus of parasites that cause babesiosis
• Plasmodium and Babesia belong to the class of parasites that have no obvious structures for the purpose of motility, known as sporozoa
• There are approximately 200 known species of Plasmodium, only 10 have demonstrated the ability to cause infection in humans
• There are over 100 known species of Babesia, 4 have been shown to cause human disease
• Most clinically relevant Plasmodium and Babesia organisms

  • Plasmodium vivax
  • Plasmodium ovale
  • Plasmodium malariae
  • Plasmodium falciparum
  • Plasmodium knowlesi
  • Babesia microti
  • Babesia divergens
• Morphological forms of Plasmodium

  • Ring form (early trophozoite)
  • Developing trophozoite
  • Immature schizont
  • Mature schizont
  • Microgametocyte
  • Macrogametocyte
• Life cycle of Plasmodium

  1. Sporozoites enter human body

  2. Schizogony in liver cells

  3. Merozoites infect red blood cells

  4. Asexual reproduction in red blood cells

  5. Gametocytes form

  6. Gametocytes ingested by mosquito

  7. Sexual reproduction in mosquito

  8. Sporozoites form in mosquito
• Malaria is transmitted to humans via a blood meal from Anopheles mosquitoes
• Malaria can also be transmitted through blood transfusions, needle sharing, and congenitally from mother to child
• Hypnozoites


  Dormant Plasmodium-infected liver cells that may cause relapses months or years after initial infection
• Giemsa-stained peripheral blood films are the specimens of choice for laboratory diagnosis of malaria
• Both thick and thin blood films should be examined to screen for and differentiate Plasmodium species
• Mainline malaria

  Malaria infection transmitted through the sharing of needles and syringes, a common practice among intravenous drug users
• Congenital malaria


  Passing of the malaria parasite from mother to child
• Giemsa-stained peripheral blood films


  Specimens of choice for the laboratory diagnosis of malaria
• Wright's stain


  May also be used and will result in an accurate diagnosis
• Giemsa is the recommended stain for all blood films submitted for parasite study
• Both thick and thin blood films should be made and examined
• Thick blood smears


  Serve as screening slides
• Thin blood smears


  Used in differentiating the Plasmodium species
• All blood films should be studied under oil immersion
• Mixed Plasmodium infections may occur, with the most frequently encountered being P. vivax and P. falciparum
• Careful and thorough screening of all smears is crucial to ensure the correct identification, reporting, and ultimately the proper treatment of all Plasmodium organisms present
• Timing of blood collection for the study of malaria

  Crucial to success in retrieving the malarial parasites
• The various morphologic forms of parasites visible at any given time depend on the stage of organism development at the time of specimen collection
• The greatest number of parasites is present in the blood in between characteristic bouts of fever and chills resulting from the release of merozoites and toxic waste products from infected RBCs, known as paroxysms
• Multiple sets of blood films, which consist of thick and thin smears, are necessary to rule out malarial infections
• It is recommended that blood be collected every 6 to 12 hours for up to 48 hours before considering a patient to be free of Plasmodium spp. parasites
• In addition to blood films, serologic tests and polymerase chain reaction (PCR) techniques for malaria are available
• Serologic testing can help rule out malaria in patients suffering from a fever of unknown origin, and PCR techniques can confirm the malarial speciation, but is usually not necessary
• Paroxysm


  A periodic episode characterized by fever, chills, sweats, and fatigue
• Paroxysms are considered in part as an allergic response of the body to the development of the schizonts and to the circulating parasitic antigens following the release of merozoites
• Patients may experience recrudescence or true relapse, where they become reinfected with rupturing hypnozoites months to years after the initial infection, as is often the case with P. vivax and P. ovale infections
• Additional malarial symptoms


  • Headache
  • Lethargy
  • Anorexia
  • Ischemia
  • Nausea
  • Vomiting
  • Diarrhea
  • Anemia
  • Central nervous system involvement
  • Nephrotic syndrome
• Malaria may mimic a number of other diseases, including meningitis, pneumonia, gastroenteritis, encephalitis, or hepatitis
• Erythrocyte structural abnormalities

  Heterozygous (Gd/Gd³) glucose-6-phosphate dehydrogenase (G6PD) deficiency and certain hemoglobinopathies (S, C, E, and thalassemia) tend to provide greater resistance to malarial infections
• Duffy blood group-negative individuals

  Also tend to show greater resistance to malarial infections than those who are positive for the antigens on their red blood cells
• Malaria belongs to the phylum Apicomplexa, class Aconoidasida, order Haemosporida, family Plasmodiidae, genus Plasmodium
• Plasmodium species found in the blood

  • Plasmodium vivax
  • Plasmodium ovale
  • Plasmodium malariae
  • Plasmodium falciparum
  • Plasmodium knowlesi