COVID-19 Report - 19

US$5.9-8.9

billion
global support (2014-2016 outbreak)
55

Bats and zoonotic disease emergence
Bats are frequently implicated in the emergence of
new zoonotic diseases. More than 200 viruses have
been associated with bats, and there have been six
major outbreaks of zoonotic diseases in the past 25
years that scientists suspect were caused by bat-borne
viruses, including the COVID-19 pandemic.70
Bats are natural reservoir hosts since they can carry
high viral loads and shed viruses without becoming
sick themselves.71 Bats also roost in colonies that can
contain tens of millions of individuals, enabling viruses
to spread rapidly. Because they are highly mobile, bats
can carry viruses to many types of habitats, including
urban areas, and potentially expose many other
species, including both domestic animals and humans.
Other animals can be infected in multiple ways through
exposure to the blood, saliva, urine or faeces of bats.72
Despite these risks, culling bats will not prevent future
zoonotic disease outbreaks and may even increase
the risk of a zoonotic disease spilling over to humans.
Previous culls have been unsuccessful, with culls in
Latin America failing to reduce rabies prevalence73 and
attempts to cull bats in Uganda leading to increased
prevalence of Marburg virus in the region.74,75 Culls
can drive bat populations to migrate to new areas,
facilitating the spread of disease. In addition, increased
physiological stress may increase the amount of virus
that bats shed.76 By culling bats, there is also a risk
of further disrupting ecosystems. In particular, bats
are essential for insect control and plant pollination,
with over 300 species of fruit dependent on bats for
pollination.

When land is cleared for agriculture, wildlife
and livestock risk coming into closer proximity,
creating conditions for disease transmission into
intermediate hosts. Since most land is converted
for agricultural and livestock production, there is also a
growing level of contact between wildlife and livestock
animals. If farms lack sufficient bio-safety regulations
to limit livestock contact with external species, these
animals risk becoming intermediate disease hosts. This
can assist with the genetic rearrangement of a virus into a
form that can be transmitted to humans, as was the case
during the 1997 Nipah virus outbreak (see case study
3).77,78 Intensified livestock farming practices can facilitate
the rapid spread of disease among animals, due to their
proximity. Small-scale or subsistence farming can also be
dangerous if not sufficiently regulated through bio-safety
protocols. Greater precautions must be taken with livestock
production to prevent these dangerous spillover events.

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COVID-19 Report

Table of Contents for the Digital Edition of COVID-19 Report
