It is a manifestation of falciparum malaria occurring in previously infected subjects and is characterised by sudden intravascular haemolysis followed by fever and haemoglobinuria.
Etiology. It is associated with infection by Plasnzodium falciparum, most commonly observed amongst the non-immune (non-indigenous) individuals who have resided in malarious countries for d months to 1 year and have had inadequate doses of quinine for both suppressive prophylaxis and treatment of repeated clinical attacks. In these cases quinine often acts as a precipitating factor. Other factors which have been known to precipitate an attack of blackwater fever are: cold, exposure to the sun, fatigue, trauma, pregnancy and parturition and X-ray treatment of the spleen.
Pathogenesis. Intravascular haemolysis.
Mechanism of Haemolysis. The exact mechanism of haemolysis in blackwater fever is not yet clearly known. There appears to be some haemolytic agent involved whereby the red blood cells undergo lysis and liberate a large quantity of oxyhaemoglobin into the blood stream. In falciparum malaria intravascular haemolysis occurs periodically at the time of schizogony. This probably stimulates the R.E. System to form antibodies of the nature of haemolysin and lecitholysin. Thus in repeated malarial attacks a hyper-sensitised state (pre-blackwater fever state) is produced which when stimulated by any factor, such as heavy P. falciparum infection of homologous or heterologous strain, administration of quinine and other precipitating factors leads to an explosive output of haemolysin resulting in the haemoclasic crisis of blackwater fever. Recent studies indicate that individuals having glucose-6-phosphate dehydrogenase deficient red blood cells are particularly susceptible to such haemolysis.
Effect of Intravascular Haemolysis. The excess of haemoglobin liberated in the circulating blood as a result of intravascular haemolysis is either catabolised into methaemalbumin, or converted by R.E. System into bilirubin and haemosiderin, or excreted through the kidneys. The following effects are observed:
(i) Methaemalbuminaemia. Oxyhaemoglobin in blood is broken down into globin and haematin (ferrous); the latter, after oxidation (ferric state), combines with serum albumin forming methaemalbumin which is not excreted in the urine (unable to pass through the renal glomeruli) but retained in the plasma causing methaemalbuminaemia.
(ii) Hyperbilirubinaemiu. The bilirubin formed by R.E. System is far in excess of what the liver can excrete and is thereby retained in the plasma, causing hyperbilirubinaemia.
(iii) Haemoglobinuria. An excess of haemoglobin remains in the circulating blood and when the haptoglobin, a protein of the plasma, is unable to bind the free haemoglobin, it is excreted through the kidneys causing haemoglobinuria. Oxyhaemoglobin may be converted into methaemoglobin in the renal tubules or deposited in the tubules as acid haematin.
Pigments in Blood and Urine: Blood. Oxyhaemoglobin, methaetnalbumin and bilirubin. Van den Bergh reaction gives an indirect positive. Methaemoglobin is not present in the blood.
Urine. Oxyhaemoglobin (gives red colour), methaemoglobin (gives dark brown or black colour), haematin, urobilin. Methaemalbumirz is not present in the urine.
Parasites in Blood. In the majority of cases the parasites (P. falciparum) are not detected in the peripheral blood either during or after the attack, as they are destroyed by the haemolytic crisis. Though the parasites disappear during the attack, they usually re-appear within a week or a fortnight after the haemolytic crisis.
Pathology. The morbid anatomy and histopathology of blackwater fever is practically the same as that of a severe type of falciparum malaria. The changes are specially noticeable in the kidneys and liver. The kidneys are large and dark in colour (due to congestion and pigmentation) and microscopically, degenerative changes are noticeable in the distal convoluted tubules which are blocked with eosinophilic granular debris (haemoglobin casts). Parasitised erythrocytes may or may not be detected inside the renal capillaries. The liver is enlarged and soft and is stained intensely yellow (due to haemosiderin); necrotic changes in the parenchyma cells are most marked in the central zone of the liver lobule. The gall bladder is filled with dark green viscid bile. The spleen is enlarged and coloured black due to the malarial pigment.
In blackwater fever there is excessive deposit of haemosidcrin pigment in the liver, spleen and kidneys.
Clinical Features. The attack begins with fever and rigor, followed by aching pains in the loins, haemoglobinuria, icterus, bilious vomiting, circulatory collapse and acute renal failure. The haemolytic episode is generally only one or two.
Cytology (Blood Picture). R.B.C. count is 1 to 2 millions per mm' (normocytic anaemia) and haemoglobin percentage drops down to 10. There may be normoblast; polychromasia and basophilic stippling of red blood cells. During recovery, reticulocytosis is marked. W.B.C:. count shows neutrophilic leucocytosis of a moderate degree.
Biochemical Alteration. Blood urea is increased and blood cholesterol is diminished. Plasma haptoglobin is very much lowered.
Parasites and Pigments. Vide. supra.
Urinary Changes. The colour of the urine varies from red to dark brown (port-wine) and is acid in reaction. When allowed to settle, there is a heavy brown amorphous deposit at the bottom. Albumin is excreted in large amounts; urobilin test shows a marked reaction. Microscopical examination shows haemoglobin casts and haematin crystals but no red blood cells. Haemoalobin pigments excreted in the urine (vide supra) are recognised by their characteristic absorption bands in the spectrum.
Complications. Renal failure (uraemia), acute liver failure and circulatory collapse.
Sequelae. Anaemia, pigment calculi.
Treatment. If parasites are detected in the peripheral blood, antimalarial chemotherapy should immediately be instituted and the drug of choice is chloroquine (for 6hloroquine resistant P. falciparum strain, as in South-East Asia, other drugs should be used). A fatal outcome in btackwater fever is often due to renal failure which is of the reversible renal anoxic type, hence it is treated with the help of artificial kidney or by peritoneal dialysis. Blood transfusion may be called for and care should be taken in cross-matching donor and recipient bloods. Both red blood cells and plasma are to be cross-matched for each specimen of blood transfused. Intravenous glucose saline was formerly used to replace lost fluid but it is risky in patients who have oliguria and anuria. Administration of large doses of alkalies was also given up because it was found to be harmful to kidney function.
Prophylaxis. With the advent of modern drugs for treatment and prophylaxis of malaria in place of quinine the indigenous inhabitants are protected from blackwater fever. If possible the subject of BWF should leave the endemic area and must not come back to it or reside in any malarial locality.
DR. FAIZUL HUQ
Similar of Blackwater Fever