In the Everglades, the disappearance of mammals is changing more than the animals that remain.
asserted
that → change → animals
Burmese pythons have spread through southern Florida and prey heavily on medium-sized and larger mammals, leaving a wildlife community that is less varied than it once was.
asserted
it → spread → community
That change may also be altering the way mosquitoes encounter the animals they feed on.
uncertain
they → alter → animals
Cotton rats are important hosts for Everglades virus, a mosquito-borne pathogen found in Florida.
asserted
rats → bear → Florida
As other mammals become scarcer, mosquitoes appear to be feeding on these rodents more often.
asserted
mosquitoes → become → rodents
The result is a chain of ecological changes in which an invasive predator may be influencing the circulation of a disease without carrying the pathogen itself.
uncertain
predator → influence → pathogen
How Burmese pythons changed the Everglades mammal community
asserted
pythons → change → community
Burmese pythons (Python bivittatus) are an introduced predator in southern Florida, where they have become established across parts of the Everglades.
asserted
they → introduce → Everglades
Their presence has been associated with steep reductions in several mammal populations, particularly among larger and medium-sized species.
asserted
presence → associate → species
That matters because mosquitoes do not feed on a single type of animal.
asserted
mosquitoes → matter → animal
Their blood meals can come from a range of mammals, and varied species available to them can affect how efficiently a pathogen moves through the ecosystem.
asserted
pathogen → come → ecosystem
When many potential hosts are present, a mosquito may feed on animals that do not support the pathogen particularly well.
uncertain
that → feed → pathogen
Those species can effectively divert some mosquito bites away from animals that are better at maintaining infection.
asserted
that → divert → infection
Disappearance of other mammals changed mosquito feeding habits
asserted
Disappearance → change → habits
The research examined areas of southern Florida where Burmese pythons were found at higher and lower densities.
asserted
pythons → examine → densities
The aim was not simply to measure how many animals were left behind, but to examine what happened to the relationships between wildlife, mosquitoes and Everglades virus.
asserted
what → measure → wildlife
Where there was greater diversity among non-rodent mammals, mosquitoes took fewer blood meals from cotton rats.
asserted
mosquitoes → be → rats
The issue was not simply whether cotton rats existed in an area.
asserted
rats → exist → area
Their importance to the mosquito population changed depending on what other mammals were available.
asserted
mammals → change → population
As the range of alternative hosts narrowed, cotton rats accounted for a greater share of mosquito feeding.
asserted
rats → narrow → feeding
Cotton rats play a different role in the disease cycle
asserted
rats → play → cycle
They are amplifying hosts for Everglades virus, meaning they can support the pathogen in a way that helps mosquitoes acquire it and pass it on during subsequent feeding.
asserted
mosquitoes → amplify → feeding
Everglades virus, or EVEV, is endemic to Florida and circulates naturally through a mosquito-rodent cycle.
asserted
virus → circulate → cycle
Mosquitoes become infected after feeding on an infected amplifying host.
asserted
Mosquitoes → become → host
The virus can then be carried to other animals through later blood meals.
asserted
virus → carry → meals
That makes the identity of a mosquito's meal significant.
asserted
identity → make → meal
A mosquito feeding on a mammal that does not contribute strongly to the virus cycle has a different epidemiological consequence from one feeding on a cotton rat capable of amplifying EVEV.
asserted
that → feed → EVEV
The Communications Biology 2021 study, titled ‘
Invasive Burmese pythons alter host use and virus infection in the vector of a zoonotic virus’ found that increasing use of cotton rats by mosquitoes was associated with increasing EVEV infection prevalence in the mosquito population.
asserted
pythons → title → population
How the python’s impact reaches mosquitoes and disease
Burmese pythons reduce the diversity of mammals in the landscape.
asserted
pythons → reach → landscape
With fewer non-rodent mammals available, mosquitoes shift some of their feeding towards cotton rats.
asserted
mosquitoes → shift → rats
Because cotton rats are important amplifying hosts for EVEV, that change in feeding behaviour is linked with greater infection prevalence among the mosquitoes.
asserted
change → amplify → mosquitoes
The python does not need to carry Everglades virus for this to happen.
asserted
this → need → virus
Its ecological influence can operate indirectly, through the wildlife community it leaves behind.
asserted
it → operate → community
That is what makes the finding relevant beyond the question of invasive snakes.
asserted
finding → make → snakes
Predator-driven changes in animal communities can alter disease dynamics even when the predator itself has no direct role in transmitting the pathogen.
asserted
predator → drive → pathogen
Why losing species can change disease transmission
The idea behind the dilution effect is relatively straightforward, although its effects can vary between ecosystems and diseases.
asserted
effects → lose → ecosystems
A mosquito looking for a blood meal encounters whatever suitable hosts are present.
asserted
hosts → look → meal
If the community contains many different mammals, some bites will fall on species that are poor hosts for a particular pathogen.
asserted
that → contain → pathogen
If those species disappear, the proportion of bites reaching competent hosts can rise.
asserted
proportion → disappear → hosts
In the Everglades, cotton rats appear to occupy that more important position for EVEV.
asserted
rats → appear → EVEV
…and 10 more, not listed.
The Aporia
