Blackwater fever in Macedonia

Abstract

1. (1) A brief outline is given of some epidemiological findings regarding blackwater fever in Macedonia, a full report of which will be published later. 2. (2) Large numbers of cases of blackwater fever occur in Greece, probably not unrelated to the immigration of refugees from areas in Asia Minor where malaria was either absent or of negligible importance. 3. (3) Regression equations were calculated to define any relationship that existed between malaria and blackwater fever in M 0 M 1 and M 2 years with the result that a definite correlation was found to exist between the number of malaria cases in any year and the number of blackwater fever cases in the same year, in an already sensitized population. 4. (4) No correlation was established between the number of blackwater fever cases and the malaria cases occurring either 1 year or 2 years previously. 5. (5) No correlation existed between malaria and blackwater fever in an unsensitized population, no matter how severe the malaria. 6. (6) The susceptibility of the populations of Macedonia to blackwater fever has been steadily rising during the last 14 years, although somewhat irregularly. Susceptibility as measured by the ratio B M may in future tend to oscillate about an upper limiting value, instead of increasing irregularly as it has done in the past. 7. (7) The seasonal lag between the malaria and blackwater fever peaks is established; and the correlation found to be 0·93 when the blackwater fever peak is shifted forward 2 months. 8. (8) Blackwater fever appears to occur in a period that lies between an apparent malaria cure and relapse, as indicated by the seasonal distribution of malaria and blackwater fever, and the malaria relapse season in Macedonia. 9. (9) 40 per cent. of the cases of blackwater fever were found to be positive for malaria; 47 per cent. falciparum, 33 per cent. vivax, 14 per cent. mixed falciparum and vivax, 6 per cent. pigmented. This should not be taken to imply that falciparum is a “more potent producer” of blackwater fever than vivax, since falciparum is about 1 1 2 times more prevalent among the general population of Macedonia than is vivax. But parasite rates in blackwater fever should not be taken to have any great significance unless the following are known:— 9.1. ( i) Time and amount of quinine taken prior to first passage of black water. 9.2. ( ii) Magnitude and duration of the haemolytic process as measured by red blood cell counts, and bilirubin levels. 9.3. ( iii) Time elapsed between first passage of black urine and taking blood film. 10. (10) Charts and tables are given showing age distribution, sex ratio, death rates, family incidence, frequency of attack, etc.