Lizards and Lyme disease risk Diana Erazo Luisa Carrillo Rodriguez - - PowerPoint PPT Presentation

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Lizards and Lyme disease risk Diana Erazo Luisa Carrillo Rodriguez - - PowerPoint PPT Presentation

Sep 09, 2022 622 likes •1.59k views

Lizards and Lyme disease risk Diana Erazo Luisa Carrillo Rodriguez Marilia Palumbo Gaiarsa Paula Ribeiro Prist Rodrigo Mazzei Carvalho Introduction It is an important public health issue in the US, where it is the most common

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Lizards and Lyme disease risk

  • Diana Erazo
  • Luisa Carrillo Rodriguez
  • Marilia Palumbo Gaiarsa
  • Paula Ribeiro Prist
  • Rodrigo Mazzei Carvalho
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Introduction

It is an important public health issue in the US, where it is the most common vector-borne disease

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Introduction

It is an important public health issue in the US, where it is the most common vector-borne disease

Black-legged tick (Ixodes scapularis) Western black-legged tick (Ixodes pacificus)

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Introduction

It is an important public health issue in the US, where it is the most common vector-borne disease

Western black-legged tick (Ixodes pacificus)

It’s transmitted to humans trough ticks’ bites

Black-legged tick (Ixodes scapularis)

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Introduction

It is an important public health issue in the US, where it is the most common vector-borne disease

Western black-legged tick (Ixodes pacificus)

It’s transmitted to humans trough ticks’ bites

Black-legged tick (Ixodes scapularis)

Borrelia burgdorferi

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Spring Winter Summer Fall

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Spring Fall Winter Summer

Eggs

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Spring Fall Winter Summer

Eggs Larvae

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Spring Fall Winter Summer

Eggs Larvae Nymph

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Spring Fall Winter Summer

Eggs Larvae Nymph

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Spring Fall Winter Summer

Eggs Larvae Nymph Adults

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Spring Fall Winter Summer

Eggs Larvae Adults Nymph Eggs

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Spring Fall Winter Summer

Eggs Larvae Adults Nymph Eggs

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Sceloporus occidentalis

Hosts

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California Kangaroo Rat (Dipodomys californicus) Dusky-footed Woodrat (Neotoma fuscipes) Western Grey Squirrel (Sciurus griseus) Deer Mouse (Peromyscus maniculatus)

Hosts

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Host competence: ability to sustain the tick population.

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Host competence: ability to sustain the tick population. Reservoir competence: ability of an infected host to infect a tick.

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Host competence

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Host competence

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Host competence Lizards hold up to 90 % of the ticks

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Reservoir competence

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Susceptible tick Infected tick Reservoir competence

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é Host competence ê Reservoir competence ê Host competence é Reservoir competence

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Objectives

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Objectives

To assess the impacts of experimentally reduced western fence lizard density on abundance and infection prevalence of Ixodes pacificus and on tick distributions

  • n the remaining hosts

Sceloporus occidentalis Ixodes pacificus ü Abundance ü Infection prevalence Other hosts

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Hypothesis

The presence of lizards may act as a barrier for the transmission of lyme disease, due to it high host competence and lower reservoir competence

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Hypothesis

The presence of lizards may act as a barrier for the transmission of lyme disease, due to it high host competence and lower reservoir competence 1) If ticks switch to other hosts when lizards are scarce, and feed with equal success, then tick abundance might not decline and infection prevalence would increase.

Predictions

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1) If ticks switch to other hosts when lizards are scarce, and feed with equal success, then tick abundance might not decline and infection prevalence would increase. 2) Alternatively, reduced lizard abundance might lower tick abundance if ticks generally fail to find alternative, high-quality hosts

Hypothesis Predictions

The presence of lizards may act as a barrier for the transmission of lyme disease, due to it high host competence and lower reservoir competence

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1) If ticks switch to other hosts when lizards are scarce, and feed with equal success, then tick abundance might not decline and infection prevalence would increase. 2) Alternatively, reduced lizard abundance might lower tick abundance if ticks generally fail to find alternative, high-quality hosts

If there is a strong preference for lizards – no switch to an alternate host

Hypothesis Predictions

The presence of lizards may act as a barrier for the transmission of lyme disease, due to it high host competence and lower reservoir competence

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Methods

MarinCounty,CA, north of San Francisco 14 long-term 1 ha plots

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Methods

MarinCounty,CA, north of San Francisco 6 experimental removal plots 8 control plots 14 long-term 1 ha plots

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Results

The effect of lizard removals on the density and infection prevalence of questing ticks was evaluated: ü Sampling larval ticks in the year of removals (time t) ü Nymphal ticks the year after the experimental manipulation

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Results

é Larvae ticks The effect of lizard removals on the density and infection prevalence of questing ticks was evaluated: ü Sampling larval ticks in the year of removals (time t) ü Nymphal ticks the year after the experimental manipulation Time t: were not able to immediately find an alternate blood meal host

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Results

é Larvae ticks were not able to immediately find an alternate blood meal host lizard removal elevated larval tick burden on female woodrats é Larval burdens

  • n female N. fuscipes

The effect of lizard removals on the density and infection prevalence of questing ticks was evaluated: ü Sampling larval ticks in the year of removals (time t) ü Nymphal ticks the year after the experimental manipulation Time t:

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Results

The year following lizard removal:

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Results

The year following lizard removal: ê Nymphal ticks ü 5.19% of larval I. pacificus did switch to a competent reservoir host (N. fuscipes)

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Results

The year following lizard removal: ê Nymphal ticks ü 5.19% of larval I. pacificus did switch to a competent reservoir host (N. fuscipes) ü The increased larval burden on N. fuscipes was not enough to absorb 94.81% of larvae that would have fed on lizards

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Results

The year following lizard removal: ê Nymphal ticks ü 5.19% of larval I. pacificus did switch to a competent reservoir host (N. fuscipes) ü The increased larval burden on N. fuscipes was not enough to absorb 94.81% of larvae that would have fed on lizards Results indicate that an incompetent reservoir for a pathogen may, in fact, increase disease risk through the maintenance of higher vector density and therefore, higher density of infected vectors

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L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible Larvae Nymph Tick fed hungry susceptible infected L N T

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Lf Las Lai Nfs Nfi Nas Nai T L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible L L N N N N T L

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Lf Las Lai Nfs Nfi Nas Nai T L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible L L N N L N N

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Lf Las Lai Nfs Nfi Nas Nai T L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible L L N N L N N

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Lf Las Lai Nfs Nfi Nas Nai T L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible L L N N L N N

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Lf Las Lai Nfs Nfi Nas Nai T L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible L L N N L N N

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Lf Las Lai Nfs Nfi Nas Nai T L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible L L N N L N N

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Lf Las Lai Nfs Nfi Nas Nai T L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible L L N N L N N

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µ1 Lf Las Lai Nfs Nfi Nas Nai T µ2 µ2 µ3 µ3 γ γ L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible L L N N L N N

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µ1 Lf Las Lai Nfs Nfi Nas Nai T µ2 µ2 µ3 µ3 γ γ L= Larvae N=Nymph T=Tick f = hungry a = fed i = infected s=susceptible L L N N L N N

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Larvae

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Larvae

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Larvae

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Larvae

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Larvae

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Larvae

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Larvae

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Nymph

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Nymph

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Nymph

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Nymph

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Nymph

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Nymph

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Nymph

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Nymph

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Hosts

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Hosts

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Hosts

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Hosts

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Hosts

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Hosts

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Hosts

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Hosts

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Hosts

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Humans

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Humans

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Humans

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Ticks

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Ticks Saturation term

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Ticks Saturation term Maintenance term

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Ticks Saturation term Maintenance term Eggs

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Final Remarks

  • Transient state;
  • Lizard = barrier
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Final Remarks

  • Transient state;
  • Lizard = barrier
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THANKS!!! ¡ ¡

  • Organizers
  • Professors
  • T.As
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