Botfly

Over the millennia, some Botfly species have adapted to hominids and their livestock of the Amazon Basin especially as their prime host prime host, creating several new genera of botfly. It evolved sometime before 20,000 BCE

Life-Cycle of the Pathogen
The pathogen as the name implies is the Botfly larvae, which finds its way into the body either through the skin or through food. There are three different genera that specialize in different ways of infecting hominids and livestock.

The first is the least divergent from OTL and is just a Botfly that tries to lay an Egg either on the skin or on the underside of an insect -- typically other flies -- likely to crawl upon the skin of the preferred host. The other also infects through skin almost always does so through an intermediate insect host, which the larvae has evolved to maipulate from the inside, similarly to how Leucochloridium worms control snails that infects. In the case of the botfly, the larvae is injected into the abdomen of a host insect -- typically something like butterflies that neither hominids nor their livestock would fear -- and the intermediate host, lands on hominids and livestock, from where the larvae emerges from the host and quickly pierces the skin of the main host.

The last genus is adapted to be laid on leaves and fruits most likely to be eaten by homonids and lifestock and are passed out in shit, where they have abundant resources to grow and pupate. But sometimes (especially when plenty are consumed) the larvae hatch in and destroy the large intestines. This happens more frequently in homonids as they take longer for food to pass thru their gut than most livestock. The eggs of this genus are numerous, hard and small to allow their safe passage through the gut.

Symptoms and Effects
The symptoms typically show up as boil like bumps on the skin; inability to control the bowels; a destruction of the large intestine, anal sphincter and colon; internal lesions; Destruction of muscle, skin and tendons.