Malaria Complications: Anemia and Hemolysis

Malaria

• Caused by four plasmodia species: Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, and Plasmodium falciparum
• Presents with abrupt onset of fever and chills, accompanied by headache, myalgia, and arthralgia, about 2 weeks after the mosquito bite
• Fever spike can reach 41°C, frequently accompanied by shaking chills, nausea, vomiting, and abdominal pain
• Splenomegaly and hepatomegaly are seen in most patients, with anemia being prominent
• Untreated malaria caused by P.falciparum is potentially life-threatening due to extensive brain (cerebral malaria) and kidney (black water fever) damage

Laboratory Diagnosis

• Diagnosis rests on microscopic examination of blood using both thick and thin Giemsa-stained smears
• Thick smear is used to screen for the presence of organisms, and the thin smear is used for species identification
• Ring-shaped trophozoites can be seen within infected red blood cells
• Gametocytes of P.falciparum are crescent-shaped ("banana-shaped"), whereas those of other plasmodia are spherical

Treatment

• The complete treatment of malaria requires the destruction of three parasitic forms: erythrocytic schizont, hepatic schizont, and erythrocytic gametocyte
• Chloroquine is the drug of choice for acute malaria, killing merozoites and reducing parasitemia
• Primaquine is used to kill hypnozoites of P.vivax and P.ovale in the liver, preventing relapses

Control and Prevention

• Insecticide spraying, improvements in land drainage, and removal of standing water, particularly in inhabited areas
• Chemoprophylaxis of malaria for travelers to areas where chloroquine-resistant P.falciparum is endemic consists of mefloquine or doxycycline
• Travelers to areas where other three plasmodia are found should take chloroquine starting 2 weeks before arrival and continuing for 6 weeks after departure

Toxoplasma

• Causes toxoplasmosis, an obligate intracellular sporozoan
• Differing from Plasmodium in that both sexual and asexual reproductive cycles occur within the gastrointestinal tract of felines (definitive host) and the disease is transmitted to other host species by the ingestion of oocysts passed in the feces of infected felines

Epidemiology

• Human infections are found in every region of the globe, with higher incidence in the tropics and lower in cold regions
• Transmission occurs through:
  • Congenital transmission from mothers to their fetus during pregnancy
  • Ingestion of contaminated food and water with sporulated oocysts from cat feces
  • Ingestion of bradyzoites (tissue cysts) in infective meat

Life Cycle

• Sexual reproduction of T.gondii occurs only in the intestinal tract of felines, most commonly in the domestic cat
• Ingested parasites enter the epithelial cells of the ileum, where they undergo schizogony
• Merozoites are released, infecting adjacent epithelial cells, and eventually differentiating into gametocytes, initiating sexual reproduction

Clinical Disease and Clinical Findings

• Acute toxoplasmosis: painful, swollen, lymph glands, fever, headache, anemia, muscle pain, and sometimes pulmonary complications
• Congenital toxoplasmosis: abortion, stillbirth, or neonatal disease with encephalitis, chorioretinitis, and hepatosplenomegaly
• In immunocompromised hosts: serious, often fatal disease, primarily encephalitis

Laboratory Diagnosis

• Serologic procedures are the primary method of diagnosis
• Immunofluorescence assay for IgM antibody is used for the diagnosis of acute and congenital infections

Treatment

• Acute toxoplasmosis in immunocompetent individuals is usually self-limited
• Congenital toxoplasmosis, whether symptomatic or asymptomatic, and disseminated disease in immunocompromised patients should be treated with a combination of sulfadiazine and pyrimethamine

Prevention

• Most effective means of preventing toxoplasmosis is to cook meat thoroughly to kill the cysts
• Pregnant women should be especially careful to avoid undercooked meat and contact with cats
• Cysts in meat can be destroyed by proper cooking (56°C for 15 minutes) or by freezing to –20°C