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

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

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

Feeding location Indoor VS outdoor biting An gambiae s.l. An funestus in VS out In Vs out 113 vs 173 122 Vs 77 113:173 122:77 1:1.5 1.6:1 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.

Feeding time

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

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

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)

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

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= 3.7+ 64/(8x1)= 3.7 +8= 11.7 Total MBR = M1+M2= 15.8 b/p/n nt= indoor total.

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.

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.

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)

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

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

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

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 1-p -ln p

Determine Longevity of the Vector For example: Then proportion of parous for the following species are: A. gambiae s.l. 82/106 = 0.7735, P=0.88 A. funestus s.l. 105/260 = 0.404 ,p=0.64 Assume GC 2 days and compute the expectation of life?

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.

Longevity of the vector The probably that each of the species live through the sporogonic cycle is : An. gambiae s.l. = pn =0.88 10 =0.28= 28% An. funestus s.l. =pn =0.64 10 =0.012= 1.2% The expectation of life is calculated as = 1 = 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

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

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 ?

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= 0.474 infective bites per person per night. On average the villager receive one infective bites every 2.1 nights.

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)

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.

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

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