Registered Phenomena Code: 475

Containment Rating: Beta

Lethality Rating: Orange
h-biohazard.png Bio-Hazard h-mind-control.png Mind-Control h-microscopic.png Microscopic h-organic.png Organic

Containment Protocols:

All instances of RPC-475 are to be stored in their egg form inside cryopreservation chambers. Internal chamber temperature must not exceed -50°C and have no less than 3 (three) redundancies applied in the cooling system. Personnel qualified in pathology are to monitor the chamber's external integrity on a biweekly basis. Should any leakage be discovered, maintaining personnel are to wear full protective gear prior to entering the containment chamber, and any person who entered the chamber in the past week is to be quarantined for at least 14 days.

Experimentation with and research of RPC-475, RPC-475-A, and RPC-475-B instances must be supervised by personnel with security clearance of Level 4 or higher. All RPC-475-A and RPC-475-B remains must be incinerated after experimentation and the research chamber sterilized with a 70% alcohol mixture. The creation of new RPC-475-A and RPC-475-B instances must have prior approval by the acting Director of Pathology on-site.

In the case of RPC-475 containment breach in populated areas, a 5km perimeter is to be established from the point of contact and no living being may cross the perimeter until confirmation of recontainment. Should a breakout occur, a permanent 50km quarantine zone is to be established, and anyone exhibiting the symptoms is to be terminated immediately. If possible, all avian instances within the perimeter are to be exterminated; this applies to RPC-475-A breaches.

» Order 475/1A «

Any and all tools currently used in researching RPC-475, RPC-475-A, and RPC-475-B instances must be incinerated and/or destroyed, including protective gear. Any personnel who entered Research Chamber 019 from 02/10/2020 to 09/03/2022, and all personnel who made contact with Dr. Derrick Hewitt in the past 6 months are to be apprehended and quarantined, with their belongings thoroughly sterilized.

Research Chamber 019 is to be closed and thoroughly sterilized. Research and experimentation with RPC-475, RPC-475-A, and RPC-475-B instances are to be suspended until further notice. The eastern wing of Harmon Crossings Apartments, Las Vegas, NV is to be quarantined until further notice.


RPC-475 in its sporocyst form.


RPC-475 refers to a species of parasitic trematode worms from the Leucochloridium genus.1 RPC-475-A refers to avian hosts of RPC-475, and RPC-475-B refers to the human (H. sapiens) hosts.

RPC-475 is identical to other parasitic flatworms from the Leucochloridium genus, with members of that genus using snails as their primary and intermediate host with birds acting as its paratenic host. The most defining trait of RPC-475's species, however, is that RPC-475 uses human hosts in place of snails.

The Leucochloridium flatworms utilize aggressive mimicry in the host snail to encourage consumption by insectivorous birds. This is done through the worms sexually maturing inside the snail's eyestalks as swollen broodsacs, giving the appearance of an insect larva such as a caterpillar. The flatworms then reproduce inside the bird's alimentary tract and distribute themselves through the bird's feces.

However, because of the absence of tentacular appendages in humans, RPC-475 instead induces abnormal bone growth that emerges from the skin. RPC-475 achieves this by hijacking the host's osteoblasts to induce artificial bone growth, then forming crude blood vessels near the surface. The host's blood can then circulate around the growth at will, giving the pulsating appearance similar to that of snail's broodsacs.


Cut surface of a humerus bone from an RPC-475-B. Note the early onset growth along the right side of the head and the shaft of the bone.

RPC-475 only exhibit symptoms in RPC-475-B instances, as they sexually mature and parasitize in the blood capillaries of the host. Comprehensive detail of symptoms observed in RPC-475-B instances can be referred to in the following attachment:

As stated previously, RPC-475 instances begin their life cycle as miracidia, which mature into sporocysts inside the host's blood vessels. However, the sporocysts asexually produce cercariae, which then directly develop into metacercariae within the sporocyst itself. It is these metacercariae that will reproduce and lay eggs, with the sporocysts acting as the facilitator of their growth.

Such metacercariae then accumulate inside the "bone broodsac"3 of an RPC-475-B instance. Upon ingestion by a bird, the metacercariae pass along its alimentary tract and latch themselves onto the bird's cloaca. The species of bird which can facilitate RPC-475 reproduction is then classified as an RPC-475-A instance.4 The metacercariae then fully mature into adult distomes in the cloaca, and are hermaphroditic in nature. Adult RPC-475 distomes then spread themselves by releasing their eggs into the bird's feces.

RPC-475 flatworms exhibit similar reproductive methods to other flatworms of the Leucochloridium genus, meaning the only way of contracting RPC-475 is through direct consumption of RPC-475-A's feces. However, research suggests that an evolutionary stage is currently underway, and adult distomes have been observed to reproduce inside the flesh of an RPC-475-A. There are currently no other species known to act as primary and intermediate hosts of RPC-475, even various species of great primates.


RPC-475 was discovered as RPC-475-B instances in a secluded village deep in rural Germany. Fortunately, there were no instances of a containment breach, as the villagers were keen to quarantine the infected upon the first symptomatic sign. Authority personnel moved into the village on 20/04/2020 and secured all RPC-475-B instances while adhering to biohazard protocols.

The origin of RPC-475 remains unclear, with the most widely accepted theory stating that it might have recently evolved from the parasites that infected the snails. This theory is further reinforced as the phylogenetics of RPC-475 distomes indicate that it might have evolved somewhere in Europe in the past 200 years.

However, the Leucochloridium genus of which RPC-475 is a member of, and observations of other species of the same genus (such as L. paradoxum), were seen thriving in the local snail population with no danger of extinction. This contradicts the established wisdom that a species only evolves if met with certain life-threatening situations, such as if the snail population were to rapidly decline.

In addition, DNA sequencing found a DNA strand commonly found in bacteria species, most notably from the Porphyromonas genus. A specific species from the genus, the P. gingivalis, was linked to diseases that exhibit symptoms similar to that of RPC-475's bone growth-inducing trait. This suggests that RPC-475 may be a product of an artificially engineered bioweapon as opposed to a natural form of evolution.

Research Logs:

Autopsy Reports:

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