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
- Pernicious malaria /cerebral malaria
- Blackwater fever
- Anaemia
- Hypoglycaemia
- Hypotension
- 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
- Pernicious malaria /cerebral malaria
- Blackwater fever
- Anaemia
- Hypoglycaemia
- Hypotension
- 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
Don’t Forget to Solve all the previous Year Question asked on Plasmodium: Clinical Features (Malaria)