MALARIAL RELAPSES 



feature.' The reason is that the parasites are not all killed off by 

 the quinine. There are two different types of relapses: the first, 

 after a short interval, may be called the true relapse; the second, 

 after a longer interval, may be called the recurrence. Relapses and 

 recurrences are probably caused by parasites belonging to the cycle 

 of schizogony, and by the parthenogenesis of the macrogametocyte, 

 which belongs to the cycle of sporogony. 



Relapses of quartan fevers take place at irregular intervals, and 

 the suggestion that they are most usual at about the twentieth 

 day is not correct. Tertian fevers relapse most commonly from 

 the fifth to the eighteenth day, and subtertian about the end of a 

 week after the original attack, but these times are extremely vari- 

 able. These relapses are historically interesting, as they probably 

 represent the quintans, sextans, septans, octans, nonans, etc., of 

 ancient authors. 



Recurrences take place after long intervals without fever and 

 without reinfection. Exactly how long the parasites can lie dormant 

 in the human body and then wake to activity and cause fever is 

 not known. Intervals of two and three years are readily credited 

 nowadays, but it is in our experience certain that the length of 

 time may be much longer. 



Parasites can certainly be found in the blood of persons long 

 after they have left the tropics; thus, Ross mentions that they 

 were found in a case in Liverpool four years after absence from any 

 malarious locality, and also states that his own father suffered from 

 attacks once or twice a year, even after nine years' residence in 

 England. 



It is probable, then, that the old idea that the malarial parasite 

 can exist or lie dormant for years in the system, and awake to re- 

 newed activity when given a suitable opportunity, is true. During 

 the apyrexial intervals it must, of course, be going through a cycle 

 of schizogony, but not in sufficient numbers to cause disease. These 

 parasites will increase rapidly, and cause fever when the general 

 vitality of the body is lowered by any of the predisposing causes 

 already mentioned, but especially by a chill, coming into action. 



MALARIAL REINFECTIONS. 



In tropical countries where there are plenty of anophelines and 

 many inhabitants, European and native, adults and children, with 

 numerous gametocytes in their blood, reinfections are found to be 

 common. Many cases of apparent recurrence in these countries 

 must be reinfections, which, of course, may be with the same or a 

 different species of parasite from that causing the first fever. 

 Repeated infections are the great cause of the quotidian and irre- 

 gular fevers of the tropics. 



