1
Improving Malaria Transmission Risk Models Temitayo O. Adanlawo, Kerri L. Miazgowicz, and Dr. Courtney C. Murdock Temitayo O. Adanlawo Email: [email protected] Contact 1. Mordecai et. al, 2013 2. World Health Organization 3. Johnson et. al, 2014 References Introduction Methods and Materials This experiment demonstrates: Mortality, fecundity, and bite rate are all interconnected. Notably, longevity plummets as temperature increases Mortality and bite rate play significant roles in the overall population size of the mosquito vector, because those with decreased longevity have a smaller time span to bite, lay eggs, and reproduce. This alters the density of mosquitoes to humans which is a factor in the transmission risk equation. Conclusion: This experiment generated a robust data set comprising of important A. stephensi life history traits essential for generating improved malaria transmission risk models which incorporate a temperature dependent mechanistic framework and essentially filling the knowledge gap there once was about Anopheles spp. mosquitoes. Discussion Acknowledgements Current malaria transmission risk models predict that the relationship between malaria risk and temperature is both positive and linear. However, mosquito and parasite traits responsible for malaria transmission display a nonlinear trend with increasing temperature [1] . This has resulted in an inconsistency with malaria’s predicted incidence rates and disease actualization. Furthermore, this discrepancy can be linked to the lack of quality data across different temperatures for Anopheles stephensi. Past studies conducted; Used data substitutes (diff. species & pathogens) to generate thermal performance curves [1] . Found the largest uncertainty in risk prediction was associated with bite rate (a), fecundity(EFD), and daily probability of mortality (µ). [3] This experiment aims to enhance the data available for A. stephensi ( an important vector of malaria) across relevant temperatures, and thus, improve the transmission risk model. The R 0 equation is used to predict the number of resulting cases from a single infection. This experiment aims to improve the precision of the R 0 Equation using temperaturedependent functions for fecundity, mortality, and bite rate. Results R 0 = & ’( )*+ ./0 12/456 789 : Basic reproductive number 20 16 36 24 28 32 Fecundity Eggs per female per day (EFD) Mortality Survivorship Bite Rate Prop. of bloodmeals taken Future Directions 1. Generate thermallydependent function for three traits measured 2. Apply model to the ‘real’ world Better accuracy in determining risk of transmission in malaria susceptible areas. R 0 (T) = < & ’( )*+ ./0 12 > 456 789 < : Many thanks to the Murdock Lab, the Population Biology of Infectious Diseases at the University of Georgia, the Odum School of Ecology, and The College of Veterinary Medicine. Thank you to Howard University, my family, and friends. Funding is provided by the National Science Foundation & the National Institute of Health. NIH R01 1R01AI110793-01A1 Mosquitoes at higher temperatures have higher biting rates than those at lower temperatures. Mosquitoes at higher temperatures have higher mortality rates than those at lower temperatures. Mosquitoes at the mid temperatures (24°C, 28°C, and 32°C) had the highest EFD values. 16 20 24 28 32 36 Life Table Study (N = 180) Fecundity (Eggs per Female per Day) Mortality (# of dead & when at different temperature treatments) Bite Rate (# of occurrences mosquito takes a blood meal) Daily proportion surviving. Calculatedas 1 cumulative proportiondead.Cumulative proportiondead was calculated as the # mosquitoes dead divided by the total # alive. Gross reproductive rate. Calculated as the # of eggs laid on day x divided by the total # mosquitoesalive on dayx and compounded daily. Figure 1. Global Malaria Incidence Rates [2] x 30 Eggs per female per day. Calculated as the # of eggs laid on day x divided by the total # mosquitoesalive on day x and averaged across all days. Life expectancy. Calculated as the total area under the daily proportion survivalcurve. Bite rate. Calculated as the # of mosquitoesthat took a blood meal on day x divided by the total # of mosquitoes alive at temp on day x and compoundeddaily. Bite rate. Calculated as the average of the # of feeds for an individualmosquitodividedby the # of opportunities that mosquitohad to feed. 15 Minute Feeding Opportunity Nonlinear rates of measurement (Mordecai et. al, 2013)

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Improving  Malaria  Transmission  Risk  ModelsTemitayo  O.  Adanlawo,  Kerri  L.  Miazgowicz,  and  Dr.  Courtney  C.  Murdock

Temitayo O. AdanlawoEmail: [email protected]

Contact1. Mordecai et. al, 2013 2. World Health Organization 3. Johnson et.  al,  2014

References

Introduction

Methods and Materials

This  experiment  demonstrates:• Mortality,  fecundity,  and  bite  rate  are  all  interconnected.• Notably,  longevity  plummets  as  temperature  increases

Mortality  and  bite  rate  play  significant roles  in  the  overall  population  size  of  the  mosquito  vector,  because  those  with  decreased  longevity  have  a  smaller  time  span  to  bite,  lay  eggs,  and  reproduce.  This  alters  the  density  of  mosquitoes  to  humans  which  is  a  factor  in  the  transmission  risk  equation.

Conclusion:  This  experiment  generated  a  robust  data  set  comprising  of  important  A.  stephensi life  history  traits  essential  for  generating  improved  malaria  transmission  risk  models  which  incorporate  a  temperature-­‐dependent  mechanistic  framework  and  essentially  filling  the  knowledge  gap  there  once  was  about  Anopheles  spp.  mosquitoes.  

Discussion

Acknowledgements

Current malaria transmission risk models predict that the relationship betweenmalaria risk and temperature is both positive and linear. However, mosquito andparasite traits responsible for malaria transmission display a non-­‐linear trendwith increasing temperature[1]. This has resulted in an inconsistency with malaria’spredicted incidence rates and disease actualization.

Furthermore, this discrepancy can be linked to thelack of quality data across different temperatures forAnopheles stephensi. Past studies conducted;• Used data substitutes (diff. species & pathogens)to generate thermal performance curves[1].• Found the largest uncertainty in risk prediction was associated with bite rate (a),fecundity(EFD), and daily probability of mortality (µ). [3]

This experiment aims to enhance the data available for A. stephensi (animportant vector of malaria) across relevant temperatures, and thus, improve thetransmission risk model.

The R0 equation is used to predict the number of resulting cases from a singleinfection. This experiment aims to improve the precision of the R0 Equation usingtemperature-­‐dependent functions for fecundity, mortality, and bite rate.

Results

R0=  𝑬𝑭𝑫&'()*+𝒂𝟐./012/456

789:�Basic

reproductive number

2016

36

24

28 32

FecundityEggs  per  female  per  

day  (EFD)  

MortalitySurvivorship

Bite  RateProp.  of  bloodmeals

taken

Future Directions1. Generate  thermally-­‐dependent  function  for  three  traits  measured

2. Apply  model  to  the  ‘real’  world• Better  accuracy  in  determining  risk  of  transmission  in  malaria-­‐

susceptible  areas.  

R0 (T) =  𝑬𝑭𝑫

 <&'()*+𝒂𝑻𝟐./012>456

789  <:

Many  thanks  to  the  Murdock  Lab,    the  Population  Biology  of  Infectious  Diseases  at  the  University  of  Georgia,  the  Odum School  of  Ecology,  and  The  College  of  Veterinary  Medicine.Thank  you  to  Howard  University,  my  family,  and  friends.  

Funding  is  provided  by  the  National  Science  Foundation  &  the  National  Institute  of  Health.NIH R01 1R01AI110793-01A1

Mosquitoes  at  higher  temperatures  have  higher  biting  rates  than  those  at  

lower  temperatures.  

Mosquitoes  at  higher  temperatures  have  higher  mortality  rates  than  those  at  lower  temperatures.  

Mosquitoes  at  the  mid  temperatures  (24°C,  28°C,  and  32°C)  had  the  highest  

EFD  values.

16 20

24 28

32 36

Life  Table  Study  (N  =  180)  Fecundity  (Eggs  per  Female  per  Day)

Mortality  (#  of  dead  &  when  at  different  temperature  treatments)Bite  Rate  (#  of  occurrences  mosquito  takes  a  blood  meal)

Daily  proportion  surviving.  Calculated  as  1-­‐ cumulative  proportion  dead.  Cumulative  proportion  dead  was  

calculated  as  the  #  mosquitoes  dead  divided  by  the  total  #  alive.

Gross  reproductive  rate.  Calculated  as  the  #  of  eggs  laid  on  day  x  divided  by  the  total  #  mosquitoes  alive  

on  day  x  and  compounded  daily.

Figure  1.  Global  Malaria  Incidence  Rates[2]

x 30

Eggs  per  female  per  day.  Calculated  as  the  #  of  eggs  laid  on  day  x  divided  by  the  total  #  mosquitoes  alive  

on  day  x  and  averaged  across  all  days.

Life  expectancy.  Calculated  as  the  total  area  under  the  daily  proportion  survival  curve.

Bite  rate.  Calculated  as  the  #  of  mosquitoes  that  took  a  blood  meal  on  day  x  divided  by  the  total  #  

of  mosquitoes  alive  at  temp  on  day  x  and  compounded  daily.

Bite  rate.  Calculated  as  the  average  of  the  #  of  feeds  for  an  individual  mosquito  divided  by  the  #  of  opportunities  that  mosquito  had  to  feed.  

15-­‐ Minute  Feeding  Opportunity

Non-­‐linear  rates  of  measurement  (Mordecai  et.  al,  2013)