1. Analysis and interpretation of Entomological data
PMI AIRS Entomology Training
Dereje Dengela
PMI AIRS Project
July 17, 2015

2. Analysis and interpretation of Entomological data
Vector feeding habits
Vector resting habits
Longevity
Vector infection rate and Infectivity
Vectorial capacity

3. Vector feeding habits
It refers to feeding location , time, and host preference
Direct methods :HLC ( CDC light trap)
Indirect : PSC ( Prokopack ).
Hypothetical HLC data
Time
An .gambiae s.l.
An. funestus s.l.
indoor
outdoor
6-7 pm 1 4 2
7-8pm 6
8-9pm 10 18
9-10pm 16 14 12 8
10-11pm 20 40
11-12pm 13 26
12-1am
1-2am 11
2-3am 5 9
3-4am 15
4-5am 3
5-6am
Total
113
173
122 77

4. Feeding location Indoor VS outdoor biting An gambiae s.l. An funestus
in VS out In Vs out
113 vs Vs 77
113: :77
1: :1
Exophagic tendency Endophagic tendency
NB:- don’t make inference based on data from one day
collection
-No of baits( collectors) or CDC traps in & out
must be equal.
- Assume equally availability of human host indoor
and out door through out the night.

5. Feeding time

6. Human-Biting Rates
The average number of bites per person per night by a vector species.
Estimation involves the feeding habits of the vector and the night time habits of the local people.
it can be calculated directly from HLC (CDC light traps) or indirectly from PSC (prokopack) aspiraor

7. Direct estimation of MBR from HLC
Let us assume that:
Number of nights of catch=8
Number of baits/collectors =1 indoor and 1outdoor.
some residents stay indoors and others outdoors.
The MBR from the previous data would be;
Indoor MBR:
An. gambiae s.l.= 113/(8x1)=14.1 b/p/n
An. funestus s.l. = 122/(8x1)=15.25 b/p/n

8. Direct estimation of MBR from HLC
Outdoor:
An gambiae s.l.= 173/(8x1)=21.6 b/p/n
An funestus s.l. = 77/(8x1)= 9.6 b/p/n
Gambie is exo. and Funestus is endo.
In reality night time habit of the people differs from place to place.
Let us assume that residents of Dodowa on average spends:
3 hrs indoor and 2 hrs outdoor between 6-11pm.
All residents spend the remaining time of the night indoors (11pm to 6am)

9. Direct estimation of MBR from HLC
Time
An .gambiae s.l.
An. funestus s.l.
indoor
outdoor
6-7 pm 1 4 2
7-8pm 6
8-9pm 10 18
9-10pm 16 14 12 8
10-11pm 20 40
Total 49 82 42 27
11-12pm 13 26
12-1am
1-2am
2-3am 5 9
3-4am
4-5am
5-6am 64 80

10. Direct estimation of MBR from HLC
let us say M1 = MBR during 6-11pm and M2
MBR indoor from 11pm-6 am
M1 has indoor and outdoor components.
M1 outdoor component= Mo= is the average number of bites per bait outdoor in five hrs between 6-11pm;
Mo= 82 mosq/(8nightsx1bait)x5hrs=2.05 per hr
=2.05 per hr x 2 hrs= 4.1 bites
M1 indoor component= Mn=is the average number of bites per bait indoor in five hrs between 6-11pm:
Mn=49 mosq/(8nightsx1bait)x5hrs=1.22 bites per hr
=1.22 X3 hrs=3.7
Mnt= Mn+MBR indoor 11pm-6 am
Mnt= /(8x1)= = 11.7
Total MBR = M1+M2= b/p/n
nt= indoor total.

11. Indirect calculation of MBR from PSC
Obtained by dividing the total number of fed mosquitoes to the total number of human occupants who spent the night in the houses used for collection
For example: total number of An gambiae s.l. collected with PSC =100 and occupants =10
UF= 2, F= 60, HG=30 and G=8
MBR= ???
Assumptions:
all fed mosquitoes were in house until time of collection.
all fed mosq. took their blood meal from the occupants.

12. Host prefence
This is determined by analyzing the source of the mosquito blood meals.
HBI is the proportion of mosq. with human blood( anthropophagy)
HBI= No of mosq. with human blood
Total number of mosquitoes with blood.

13. Resting habit
Important index is the proportion of blood meal taken on human followed by resting indoors.
RD = kHD
MRiN
where,
k = a correction value of 1.16
H = Human-blood index
D = indoor resting density (total number of females collected divided by
number of houses used for the spray-sheet collection)
M = man-biting rate
Ri = duration of resting indoors after feeding, in days; Ri = 1 + G/F,
where : G = Gravid + half gravid mosquitoes (spray-sheet collections) and F is the number of freshly fed females (spray-sheet collections)
N = average number of persons per house (household size)

14. Resting habit Hypothetical data Description An gambiae s.l.
An. funestus s.l.
No houses surveyed 20
No of inhabitants
100
No female mosq. collected
1600
Fed
1000 40
HG( Half Gravid)
400 35
g(Gravid)
200 25
Ri( indoor resting post feeding)
1+600/1000= 1.6
1+60/40=2.5
M(MBR) 10
0.4
HBI (H)
0.7
0.96

15. Resting habit RDgambiae= kHD = 1.16X0.7X 80 10 X 1.6 X 5 =0.812
MRiN
= 1.16X0.7X 80
10 X 1.6 X 5
=0.812
RDfunestus = kHD
= 1.16X0.96X 5
5X 2.5 X 0.4
= 1.113

16. Longevity of the vector
Two other factors affect the likelihood of being bitten by an infective mosquito:
1. P= probability of surviving one day after blood meal and expectation of life for n days

17. Determine Longevity of the Vector
obtain proportion of parous(PR) =
no. of parous females
total no. of females examined
If GC is two days, the probability of surviving through one day (P) is
The expectation of life = = 1
1-p ln p

18. Determine Longevity of the Vector
For example: Then proportion of parous for the following species are:
A. gambiae s.l. 82/106 = , P=0.88
A. funestus s.l. 105/260 = ,p=0.64
Assume GC 2 days and compute the expectation of life?

19. Determine Longevity of the Vector
p is the probability of surviving one day,
pn is the probability of surviving n days.
For example, at an average daily temperature of 27oC, it would take about 10 days for P. falciparum
n = T/(t - tmin), where n = duration of sporogony; T = 111 for P. falciparum;
t = actual average temperature in degrees centigrade and tmin = 16 for P. falciparum.

20. Longevity of the vector
The probably that each of the species live through the sporogonic cycle is :
An. gambiae s.l. = pn = =0.28= 28%
An. funestus s.l. =pn = =0.012= 1.2%
The expectation of life is calculated as = = 1
1-p ln p
An. gambiae s.l. = 1/-lnp= 7.82 days.
An. funestus s.l s.l. = 1/-lnp= 2.2 days

21. Infection of the vector
Two methods available:
Dissection and examination of salivary glands for sporozoites
Enzyme-linked immunosorbent assay (ELISA) method or PCR.
- ELISA detects circumsporozoite protein either
from intact sporozoites or in soluble form within
the mosquito

22. Infection of the vector
The sporozoite rate(SR) of the female mosquitos
Sporozoite rate(%)= No of sporozoite positiveX100
No dissected and examined.
For example,
No of An. gambiae s.l. dissected = 1000
No of An. gambiae s.l. positive for sporozoite= 30
What is the SR?
What is infectivity of the An. gambiae s.l ?

23. Infectivity of An. gambiae s.l
EIR= The number of infective bites per person per night.
It is calculated as the product of SR and MBR.
For An. gambiae s.l:
MBR= 15.8
SR = 3%
EIR= MBRX SR= 15.8x 0.03= infective bites per person per night.
On average the villager receive one infective bites every 2.1 nights.

24. Vectorial Capacity
Vector capacity is defined as the capacity of a vector population to transmit malaria in terms of the potential number of secondary inoculations originating per day from an infective person.
Vectorial capacity (C) = ma2pn/-lnp
where,
m = density of vectors in relation to man
a = number of blood meals taken on man per vector per day (= human blood index X 0.5, if a gonotrophic cycle of two days is assumed)
p = daily survival probability (or proportion of vectors surviving per day)
n = incubation period in the vector (days)

25. Vectorial Capacity
The vectorial capacity is one of the most important concepts in the theoretical studies of the epidemiology and control of malaria.
For example, using this concept, it can be shown that halving the survival p (by IRS/LLINs) produces a much greater reduction in vectorial capacity than halving a, which is itself more effective than halving the density m.

26. Vectorial Capacity m a p n C(approx) 10 0.5 0.8 1.34 5 0.67 0.25 0.335
Vectorial capacity (C) = ma2pn/-lnp m a p n
C(approx) 10
0.5
0.8
1.34 5
0.67
0.25
0.335
0.4
0.0004

27. Thank you!