Data from: Viral transmission and infection prevalence in a cannibalistic host–pathogen system

Cannibalism, while prevalent in the natural world, is often viewed as
detrimental to a cannibal’s health, especially when they consume
pathogen-infected conspecifics. The argument stems from the idea that
cannibalizing infected individuals increases the chance of coming into
contact with a pathogen and subsequently becoming infected. Using an
insect pest, the fall armyworm (Spodoptera frugiperda), that readily
cannibalizes at the larval stage and its lethal pathogen, we
experimentally examined how cannibalism affects viral transmission at both
an individual and population level. Prior to death, the pathogen in the
system stops the larval host from growing, resulting in infected
individuals being smaller than healthy individuals. This leads to
size-structured cannibalism of infected individuals with the larger
healthy larvae consuming the smaller infected larvae, which is commonly
observed. At the individual level, we show that the probability of
cannibalism is relatively high for both infected and uninfected
individuals especially when the cannibal is larger than the victim.
However, the probability of the cannibal becoming infected given that a
pathogen-infected individual has been cannibalized is relatively low. On a
population level, when cannibalism is allowed to occur transmission rates
decline. Additionally, by cannibalizing infected larvae, cannibals lower
the infection risk for non-cannibals. Thus, cannibalism can decrease
infection prevalence and, therefore, may not be as deleterious as once
thought. Under certain circumstances, cannibalizing infected individuals,
from the uninfected host’s perspective, may even be advantageous, as one
obtains a meal and decreases competition for resources with little chance
of becoming infected.

同类相食在自然界中虽广泛存在，但通常被认为会对同类相食者的健康产生不利影响，尤其当其摄食了被病原体感染的同种个体时。该观点的核心依据为：取食受感染同类会提升接触病原体并进而感染的风险。
本研究以一种在幼虫期极易发生同类相食的农业害虫——草地贪夜蛾（Spodoptera frugiperda）及其致死性病原体为研究材料，通过实验探究了同类相食在个体与种群两个层面对病毒传播的影响。
在宿主幼虫死亡前，该病原体会抑制其生长，导致受感染个体的体型小于健康个体。这一特征使得同类相食呈现体型依赖结构：体型更大的健康幼虫会取食体型更小的受感染幼虫，这也是野外常见的观察现象。
在个体层面，研究结果显示：无论捕食者与猎物是否被感染，同类相食的发生概率均相对较高，尤其当捕食者体型大于猎物时。但在成功取食受感染个体后，捕食者自身被感染的概率相对较低。
在种群层面，允许同类相食发生时，病毒的传播速率会出现下降。此外，通过取食受感染幼虫，同类相食者可降低非同类相食者的感染风险。因此，同类相食可降低种群的感染率，其危害性或许并不如此前所想那般严重。
在特定条件下，从未感染宿主的视角来看，取食受感染个体甚至可能是有利的：既获得了食物来源，又减少了资源竞争，且自身感染的概率极低。