This document summarizes research on the effects of timing on interactions between Plasmodium parasites and their mosquito hosts. The studies show that: 1) The density of Plasmodium parasites varies depending on whether the light/dark cycle of the host mouse is matched or mismatched to the parasite's internal clock. 2) Infecting mosquitoes in the morning versus evening results in no difference in infection success but differences in fecundity and likelihood to lay eggs, with morning-infected mosquitoes more likely to lay eggs later. 3) Timing of infection is therefore important both directly for the parasites and indirectly by influencing mosquito reproduction, with implications for transmission potential depending on vector feeding times

1. THE
ECOLOGY
Probing The Particulars
Of Periodicity In
Plasmodium Parasites
OF TIMING
IN HOST-
PARASITE Aidan O’Donnell
Nicole Mideo
INTERACTIONS Sarah Reece

2. ~24 hours
Artificial Biological Clock by Cohen Van Balen

3. 3 Matched Mismatched
Parasite density x 109 / ml
2
1
0
Reversed Light Room
Reversed Cycle Normal Regime Room
Normal Cycle
Artificial Biological Clock et al Cohen VanSoc B.
O’Donnell
by 2011 Proc. R. Balen

4. 3 Matched Mismatched
Parasite density x 109 / ml
2
1
0
Reversed Room Normal Room
Reversed
Cycle Normal Cycle
O’Donnell et al 2011 Proc. R. Soc. B
Stage Route
3 3
Matched Mismatched Matched Mismatched
Parasite density x 109 / ml
2 2
1 1
0 0
Ring Troph IV IP
Artificial Biological Clock by Cohen Van Balen
2013

5. 10
Matched MisMatched
parasite density (x108 ml-1)
8
6 Infection
4
control
2
measure?
0
1 2 3 4 5 6 7
Day post infection 5
parasite density (x105 ml-1)
4
3
Barrier to 2
infection? 1
0
1 2

6. Timing matters in host
Timing & transmission
Does timing matter to
the mosquito?
Indirect consequences
to parasites?

7. What are
the fitness
consequences
of timing
to mosquitos?

8. Drosophila:
Periodicity in
susceptibility to
infection
Stone (2012) PLoS Pathog.
Activity of An. stephensi
Expected Unexpected
Rowland (1989) Physiol Entomol

9. Morning feed Evening feed
10am 8pm
7am 1pm 7pm 1am 7am 1pm 7pm
GMT Rowland (1989) Physiol Entomol
10 P. berghei
Cumulative parasite desnity
p = 0.75
(x 108 ml-1)
5
0
Matched Mismatched

10. Proportion infected :
~95% infection success
No difference between Eve/Morn
(p = 0.56)
Oocysts Evening
Morning
250
p = 0.15
200
Oocyst density
150
100
50
0
Evening Morning

11. Reduced fecundity in
Infected mosquitos
No effect of timing
Clutch size
80
21 = 5.12; P = 0.0271
mean clutch size
60
40
20
0
control infected

12. Timing effects likelihood to
lay
Infection reduces likelihood to
lay
Proportion that laid
0.8 control infected
proportion laying eggs
0.6
0.4
0.2
0.0
evening morning
Time: 21 = 3.39; P = 0.06567
Treatment: 21 = 5.46; P = 0.01944

13. Overall, uninfected
Morning fed
mosquitos more
mosquitos lay as
likely to lay & lay
soon as they can
later
Egg lay day 8+
First day of egg lay (day 5)
0.5
0.8 control infected
control
Proportion that lay
0.4
Proportion that lay
0.6 infected
0.3
0.4
0.2
0.2
0.1
0.0
0.0
evening
evening morning
morning
F(1,18) = 7.70; PP = 0.0008
F(1,16) 17.10; = 0.013

14. -No difference in mortality
of inf vs. uninf when no
egg lay
-Increased longevity
through reduced
fecundity
Vézilier (2012) Proc. R. Soc. B
Morning infected
Investing in
Immediate
reproduction

15. Timing matters directly to parasites
in the host
Timing also matters indirectly
through its effect on mosquitos
Transmission
potential could
depend on when
the vector is infected

16. Mosquito
adaptation
to bed-nets
-Moiroux (2012) J Infect Dis.
-Charlwood (1987) Med. Vet. Entomol.
Parasite
adaptation
to timing

17. Reece Group
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