Schematic figure of the asexual and sexual reproduction of Cryptosporidium serpentis. Ingested C. serpentis oocysts release sporozoites (S), which invade the brush border of the gastric epithelial cells and develop into trophozoites (T) and type I meronts (M1) containing type I merozoites (Mz1). These merozoites can become trophozoites and reinfect the host cell or develop into a type II meront (M2), which release type II merozoites (Mz2) that develop into undifferentiated gamonts (G). Gamonts differentiate into macrogamonts (Ma) or microgamonts (Mi); the latter develop microgametes (g), which fertilize the macrogamonts. After two mitotic divisions, a zygote (Z) develops in either a one-layered, thin-walled oocyst (1) or a two-layered, thick-walled oocyst (2). The thin-walled oocyst will typically autoinfect the host and the thick-walled oocyst will be shed into the environment. Adapted from Bones et al. (2019).

Gastric mucosal hypertrophy with exaggerated, edematous longitudinal rugae and copious mucus at postmortem examination of a Louisiana pine snake (Pituophis ruthveni) with gastric cryptosporidisis. The snake is in right lateral recumbency, cranial is to the left. The stomach has been incised longitudinally and the stomach wall reflected laterally.

A black-tailed cribo (Drymarchon melanurus) infected with C. serpentis. This snake exhibited anorexia and regurgitation. Note the emaciation and midbody swelling (arrow).

Endoscopic view of a gastric mucosa biopsy with a 1.8-mm biopsy forceps in an Eastern indigo snake (Drymarchon couperi). Note the edematous, hypertrophic gastric mucosa. Image taken with a video gastroscope (VS-9215, MDS Inc., Valrico, FL).

Microscopic view of a gastric lavage direct wet mount cytology collected from a Florida pine snake (Pituophis melanoleucus mugitus) demonstrating Cryptosporidium oocysts. PCR and DNA sequencing confirmed C. serpentis. Magnification 400×, each line = 2.5 µm. Scale bar = 10 µm.

Microscopic view of gastric swab cytology collected from an Eastern indigo snake (Drymarchon couperi) demonstrating Cryptosporidium oocysts (arrows). The sample has been stained with Wright-Giemsa (Volu-Sol, Inc., Salt Lake City, UT). PCR and DNA sequencing confirmed C. serpentis. Magnification 1,000×, each line = 1.0 µm. Scale bar = 5 µm.

Microscopic view of gastric swab cytology collected from the same Eastern indigo snake (D. couperi) in Figure 5 demonstrating Cryptosporidium oocysts (arrows). The sample has been stained with acid fast stain (JorVet J-326AS, Jorgensen Laboratories, Inc., Loveland, CO), which color the oocysts pink to red. PCR and DNA sequencing confirmed C. serpentis. Magnification 1,000×, each line = 1.0 µm. Scale bar = 10 µm.

Gastroscopic images of the fundic region of the stomach in Eastern indigo snakes (D. couperi). (A) Normal stomach. There is no visible mucosal inflammation or edema and endoscopic insufflation will easily flatten the gastric rugae. (B) Mild changes associated with gastric cryptosporidiosis. Note the mild mucosal inflammation and increasing thickness of gastric rugae. Endoscopic insufflation will mostly flatten the gastric rugae. (C) Mild to moderate changes associated with gastric cryptosporidiosis. Note the mucosal inflammation and edema. The thicker gastric rugae will only partially flatten with endoscopic insufflation. (D) Severe changes associated with gastric cryptosporidiosis. Note the mucosal inflammation and marked edema. Because the gastric rugae are so thick and the gastric lumen narrowed, endoscopic insufflation cannot flatten the rugae. Images taken with a video gastroscope (VS-9215, MDS Inc., Valrico, FL).