188 
MALARIA 
longer than non-pregnant females. While 
it has never occurred to anyone to inter¬ 
rupt a pregnancy because of an acute 
attack of benign tertian malaria, some 
physicians hesitate to use quinine during 
pregnancy lest an abortion or premature 
labor occur. It is the consensus of opinion 
that therapeutic doses of quinine have no 
oxytocic effect except, perhaps, at term. 
Congenital malaria. While there is no 
reason to believe that the incubation period 
of benign tertian malaria in infants is 
different from that of adults, we have no 
exact information on this point. Taking 
eight days as the shortest time after mos¬ 
quito inoculation that P. vivax can be 
demonstrated in blood smears of adults, 
we cannot with scientific accuracy classify 
under “congenital” malaria P. vivax in¬ 
fections observed in children more than 9 
or 10 days old. It is of the utmost im¬ 
portance to inquire if the infant received 
a blood transfusion, as in our own cases 
of “congenital malaria” this was their 
origin. Seemingly authentic instances of 
P. vivax infection in infants under 10 days 
old have been observed. In these cases the 
child was likely infected with maternal 
blood through an abrasion at birth and not 
infected in utero. 
Duration of infection and renewed clin¬ 
ical activity. The, duration of an infection 
with P. vivax is not accurately known. 
Data available from blood transfusion 
records are inconclusive, but it appears 
from the best authenticated cases wherein 
P. vivax malaria was transmitted by blood 
transfusion, that the parasite may still be 
present as late as 2 years after the primary 
clinical attack. In this circumstance the 
infection persists in a clinically inactive 
or latent status. It is difficult to appraise 
the effect produced on the host by the 
scanty parasites which persist. The period 
of latency or quiescence is frequently 
broken or interrupted by one or more in¬ 
tervals of renewed or secondary clinical 
activity. These secondary attacks manifest 
all of the symptoms, both subjective and 
objective, which characterised the primary 
attack. 
The likelihood of renewed clinical activ¬ 
ity, appears, according to Boyd and Kitchen 
(1937d) to be more likely with certain 
strains of P. vivax than with others. 
As the primary attack approaches termi¬ 
nation, not infrequently the hours when 
one or more paroxysms are due will be 
passed without clinical activity. Not until 
one such period of quiescence has attained 
a duration of from 2 to 3 weeks, is it likely 
that the termination of the primary attack 
has actually been observed. This practically 
includes any activity occurring within 60 
days of the onset. 
Renewed clinical activity was observed 
by Boyd and Kitchen in slightly more than 
50 per cent of the patients whose primary 
attack terminated spontaneously and who 
did not subsequently receive intensive 
therapy. When termination of the attack 
was followed by intensive therapy, cases 
of this character have not shown further 
activity. Patients whose primary attacks 
were interrupted by small doses of quinine 
have invariably had a return of clinical 
activity unless they subsequently received 
intensive therapy. 
According to Boyd and Kitchen, patients 
having primary attacks lasting for more 
than 48 days have not experienced renewed 
clinical activity, which has also but rarely 
been observed in persons whose primary at¬ 
tack lasted only from 7 to 34 days. The 
period of renewed activity is usually of 
shorter duration than the primary attack, 
but it may sometimes be longer. The first 
such period is usually longer than the sec¬ 
ond or later periods. Some may consist 
solely of a single isolated paroxysm. 
Variations with strains. Variations in 
the virulence of different strains of P. 
vivax, as judged by the severity of clinical 
symptoms and length of the acute clinical 
attack, have been reported. There is only 
a small amount of tangible evidence for 
these conclusions. It must be remembered 
that too few first-hand observations have 
been made by competent observers in an 
adequate number of patients with the same 
status of immunity under controlled con- 
