Review of Chronic Ovoretention in Rattlesnakes (Crotalus and Sistrurus spp.) at a Single Zoological Institution

Abstract

Chronic ovoretention, or egg binding, is a common cause of morbidity in captive female snakes. Both oviparous and viviparous species can be affected, but most literature is focused on management in oviparous species. The epidemiology and preferred treatment of chronic, unfertilized ovoretention in viviparous species, such as rattlesnakes, are not well described. This study reviewed the prevalence, morbidity, and mortality associated with ovoretention in Crotalus and Sistrurus rattlesnakes over 10 yr at a single institution. Period prevalence in mature female rattlesnakes (n = 63) was 15.9%. Ovoretention was the single most common clinical diagnosis for this cohort, comprising 32% of presentations (n = 25), and was the leading identified cause of death, with attribution in 20.8% of necropsies (n = 24). Data were abstracted from 10 cases, spanning eight crotalid species. Median age was 10 yr (range, 4–18 yr), and case fatality was 50%. Affected animals had variable parity and sperm exposure and presented with diverse clinical signs. Medical management alone was infrequently successful; most cases required procedural intervention. Salpingotomy had positive outcomes, including future reproductive success. Bacterial salpingitis, oophoritis, or both were detected in four cases. Serious comorbidities included uterine rupture, sepsis, and disseminated mycobacteriosis. Although prevalence of ovoretention in rattlesnakes likely varies across institutions, it can become a significant contributor to morbidity and mortality in rattlesnake collections. Cases may have a long subclinical period despite significant pathologic lesions, and conservative management may be unrewarding. A more proactive, evidence-based approach to ovoretention could potentially improve the survival, welfare, and fertility of female rattlesnakes in human care.