Overview of pentastome life cycles

Pentastomes rely on multiple hosts during their life cycles, including intermediate hosts (where larval stages occur) and definitive hosts (where adult stages mature). In North America, native snake pentastomes typically have two-host life cycles. For example, Kiricephalus coarctatus uses diverse intermediate hosts includings amphibians, reptiles, mammals, and fish. While Porocephalus crotali has primarily been documented with mammals as intermediate hosts. The snakes that host adult pentastomes of these species are determined by their diet. In contrast, Raillietiella orientalis follows a three-host life cycle, involving both invertebrates and vertebrates. 

Life Cycle of Raillietiella orientalis

1. Eggs are ingested by coprophagous invertebrates, such as cockroaches, when they consume egg-laiden feces. The eggs molt and mature within the fat bodies of the invertebrates.
2. Small vertebrates, including anurans (toads and frogs), lizards, and potentially small mammals, consume the infected invertebrate. In the second host, the larvae develop throughout viscera.
3. The larvae are transferred to their final host when the snake or lizard consumes an infected vertebrate. The larvae bore through the viscera to get to the lung(s) where they molt to the reproductive stages, reproduce, and feed on the blood.

Individual impacts

Raillietiella orientalis is a long-lived parasitic crustacean that lives in the lungs of snakes. Infections in native snakes have been associated with inflammation, pneumonia, sepsis, and mortality. We currently lack a comprehensive understanding of the sublethal effects of infection and their implications for survivorship.

​Geographic spread

This parasite emerges as a substantial conservation issue for native snake populations, with evidence indicating its presence in at least 19 native snake species across 35 counties in Florida. Raillietiella orientalis exploits abundant and widely distributed intermediate hosts, which are frequently consumed by various snake species and are commonly transported by humans. Additionally, R. orientalis is present in the pet trade and has been linked to numerous fatalities among captive animals. Considering its presence in the pet trade and utilization of widespread hosts, R. orientalis is expected to further expand its range into the southeastern United States .

​Population & community declines

The initial discoveries of Raillietiella orientalis infections coincide with declines in snake populations in certain regions of south and central Florida (anecdotal + empirical evidence). However, it is crucial to gather evidence linking R. orientalis to these declines and mortality events to fully understand the threat posed by its increased prevalence and geographic spread.

 R. orientalis range in 2022 (pre-SLAM)

Miller et al., 2018; Metcalf et al., 2018; Farrell et al., 2019; Miller et al., 2020; Walden et al., 2020; Bogan et al., 2022.

R. orientalis range 2025

Palmisano et al., 2023; Palmisano et al., 2025; Unpublished data.