Plasmodium: Clinical Features (Malaria)

Plasmodium: Clinical Features (Malaria)


 Antimalarial defence

  • Evolutionary – Survival
  • Inherited alterations in RBCsHbS, HbC, lack of Duffy antigen
  • Others – βThalasssaemia, G6PD, HLA Bw53 and HLA-DR

Genetic factors protecting against Malaria

  • Sickle cell anaemia – 
    • Sickle celled RBCs are removed by the spleen before the development of schizonts
  • Ovalocytosis –
    •  RBCs are rigid and they resist parasitic invasion
  • Duffy blood group negative individuals –
    •  Duffy blood group Ag is the receptor for the attachment of merozoites of P.vivax
  • Newborn infants – 
    • Natural protection for 1st few months of life due to high conc. of  HbF in their RBCs.
    • Para amino benzoic acid of breast milk prevent the infection
  • Beta thalassaemia –
    • Protects against severe falciparum infection

General mechanism of antimalarial defence

  • Cellular and Humoral response
  • Stimulation of immune response Antibodies and T lymphocytes
  • Antigenic variation of PfEMP1 Parasite also reduces antigen presentation
Clinical features

P. falciparum: 

  • Malignant tertian = Pernicious malaria
  • The most virulent plasmodium species.
  • P. Ovale: Ovale tertian
  • P. vivax: Benign tertian
  • P. malariae: Quartan malaria
Symptoms
  • Series of febrile paroxysms
    • Each paroxysm has 3 stages – cold stage (rigors), hot stage (high temp., body & joint pains, vomiting   & diarrhoea) and perspiration stage (fall in temp).
    • Fever is caused by the release of merozoites & toxins from ruptured erythrocytic schizont which in turn causes the release of cytokines.
  • Quartan malaria – every 72 hrs
  • Tertian malaria  – every 48 hrs
  • The major organs that are directly involved due to parasitic infestations are:
    • Spleen, Liver, Brain.
  • The organs which are involved secondarily 
    • Heart (Hypoxic lesions)
    • Lung (Pulmonary edema)

Falciparum Malaria

  • Most widespread
  • Accounts for 80% of malaria cases worldwide
  • Multiple infections of the red blood cell

    • More than one parasite (from 2 to 6) invading a single red blood cell is very common with P falciparum.

  • Most pathogenic of human malaria species
  • Untreated infections – severe disease & even death, particularly in young children, pregnant woman & non-immune adults.
  • Does not affect heart or lungs.
  • Severe falciparum malaria is associated with
  1. Pernicious malaria /cerebral malaria
  2. Blackwater fever
  3. Anaemia
  4. Hypoglycaemia
  5. Hypotension
  6. Complications in pregnancy

Black waters Fever

  • Sometimes seen in falciparum malaria
  • Particularly in patients who experienced repeated infections and inadequate quinine treatment
  • Clinical features include 
    • Bilious vomiting and prostration with Passage of dark red and blackish urine.
  • Pathogenesis includes
    • Massive intravascular hemolysis secondary to anti-erythrocyte antibodies.
  • Complications include
    • Renal failure, acute hepatic failure, and circulatory collapse

Algid Malaria

  • Malaria characterized by peripheral circulatory failure rapid thready pulse with low BP and cold clammy skin.

Septicemic Malaria

  • High continuous fever with the dissemination of parasite to various organs leading to multiorgan failure.

Falciparum malaria in Pregnancy

  • Can result in:
  • Severe anaemia
  • Low birth weight babies
  • The greatest risk in 1st pregnancy

Malaria caused by P.vivax, P.ovale & P.malariae

  • Rarely life-threatening
  • Relapses/ recurrences are a feature

Recurrences in Malaria

  • May result from – reinfection or  due to certain events related to the parasite’s life cycle
  • Two types of recurrences known in malaria:

1. Recrudescence

  • Seen in P. falciparum & P.malariae 
  • Recurrence of sexual parasitemia after completion of treatment
  • The numbers may increase later, leading to reappearance of clinical symptoms
  • Occur mostly up to one year or so but in P.malariae, it can occur even after decades

2. Relapse

  • Occurs due to a special form of parasites – hypnozoites.
  • Hypnozoites are the sporozoites that remain dormant after infecting liver
  • Seen in P. vivax
  • Activated from time to time to initiate pre-erythrocytic schizogony – Exoerythrocytic schizogony.

Exam Important

Genetic factors protecting against Malaria 

  • Sickle cell anaemia – 
    • Sickle-celled RBCs are removed by the spleen before the development of schizonts
  • Duffy blood group negative individuals –
    •  Duffy blood group Ag is the receptor for the attachment of merozoites of P.vivax
  • Newborn infants – 
    • Natural protection for 1st few months of life due to high conc. of  HbF in their RBCs.
    • Para amino benzoic acid of breast milk prevent the infection

Clinical features

P. falciparum: 

  • Malignant tertian = Pernicious malaria
  • The most virulent plasmodium species.

Symptoms

  • Quartan malaria – every 72 hrs
  • Tertian malaria  – every 48 hrs
  • The major organs that are directly involved due to parasitic infestations are
    • Spleen, Liver, Brain.
  • The organs which are involved secondarily 
    • Heart (Hypoxic lesions)
    • Lung (Pulmonary edema) 

Falciparum Malaria

  • Multiple infections of the red blood cell

    • More than one parasite (from 2 to 6) invading a single red blood cell is very common with P falciparum.

  • Most pathogenic of human malaria species
  • Does not affect heart or lungs.
  • Severe falciparum malaria is associated with
  1. Pernicious malaria /cerebral malaria
  2. Blackwater fever
  3. Anaemia
  4. Hypoglycaemia
  5. Hypotension
  6. Complications in pregnancy

Black waters Fever

  • Sometimes seen in falciparum malaria

Recurrences in Malaria

1. Recrudescence –

  • Seen in P. falciparum & P.malariae 
  • Recurrence of sexual parasitemia after completion of treatment

2. Relapse

  • Occurs due to a special form of parasites – hypnozoites.
  • Hypnozoites are the sporozoites that remain dormant after infecting liver
  • Seen in P. vivax
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