Longitudinal and Cross-Sectional Sampling of Serpentovirus (Nidovirus) Infection in Captive Snakes Reveals High Prevalence, Persistent Infection, and Increased Mortality in Pythons and Divergent Serpentovirus Infection in Boas and Colubrids

Abstract

The aim of this study of serpentovirus infection in captive snakes was to assess the susceptibility of different types of snakes to infection and disease, to survey viral genetic diversity, and to evaluate management practices that may limit infection and disease. Antemortem oral swabs were collected from 639 snakes from 12 US collections, including 62 species, 28 genera, and 6 families: Pythonidae (N = 414 snakes; pythons were overrepresented in the sample population), Boidae (79), Colubridae (116), Lamprophiidae (4), Elapidae (12), and Viperidae (14). Infection was more common in pythons (38%; 95% CI: 33.1–42.4%), and in boas (10%; 95% CI: 5.2–18.7%) than in colubrids (0.9%, 95% CI: <0.01–4.7%); infection was not detected in other snake families (lamprophiids 0/4, 95% CI: 0–49%; elapids 0/12, 95% CI: 0–24.2%; and vipers 0/14, 95% CI: 0–21.5%), but more of these snakes need to be tested to confirm these findings. Clinical signs of respiratory disease were common in infected pythons (85 of 144). Respiratory signs were only observed in 1 of 8 infected boas and were absent in the single infected colubrid. Divergent serpentoviruses were detected in pythons, boas, and colubrids, suggesting that different serpentoviruses might vary in their ability to infect snakes of different families. Older snakes were more likely to be infected than younger snakes (p-value < 0.001) but males and females were equally likely to be infected (female prevalence: 23.4%, 95% CI 18.7–28.9%; male prevalence: 23.5%, 95% CI 18–30.1%; p-value = 0.144). Neither age (p-value = 0.32) nor sex (p-value = 0.06) was statistically associated with disease severity. Longitudinal sampling of pythons in a single collection over 28 months revealed serpentovirus infection is persistent, and viral clearance was not observed. In this collection, infection was associated with significantly increased rates of mortality (p-value = 0.001) with death of 75% of infected pythons and no uninfected pythons over this period. Offspring of infected parents were followed: vertical transmission either does not occur or occurs with a much lower efficiency than horizontal transmission. Overall, these findings confirm that serpentoviruses pose a significant threat to the health of captive python populations and can cause infection in boa and colubrid species.

Python nidoviruses, more than respiratory pathogens

“…were of the genus Morelia . The results suggest increased susceptibility of snakes from this genus to nidovirus infection and/or disease, a finding also supported by recent epidemiologic studies (14). In support, the analysis of the viral genomes by NGS did not show differences in the viral genome that would explain the differences in the disease manifestation.…”

“…Since Serpentovirinae sp. isolate L1 was sequenced from a Python regius in the USA in 2015 (14), whereas the strains BH171/14-7, BH128/14-12 (33) and CH-F1 were isolated from a Morelia viridis in Germany (2015) and Switzerland (2018), it is likely that the recombination events have occurred between the ancestors of these lineages.…”

“…Thus far little is known about the intra- and interspecies transmission of python nidoviruses. However, recent studies demonstrated nidovirus RNA in oral and cloacal swabs and the intestinal content of diseased and healthy snakes, suggesting that both airborne and fecal-oral transmission may occur (7, 14, 9–11).…”

Presumptive heterophil extracellular traps recognized cytologically in nine reptile patients with inflammatory conditions

“…Hematological abnormalities were absent and plasma biochemistry was not performed. Oral mucosal swabs tested positive for serpentovirus and mycoplasma by polymerase chain reaction (PCR) and sequencing (Hoon-Hanks et al 2019 ). Due to the severe clinical condition and poor prognosis, the snake was euthanized.…”

Serpentovirus (Nidovirus) and Orthoreovirus Coinfection in Captive Veiled Chameleons (Chamaeleo calyptratus) with Respiratory Disease

“…However, further evidence of disease causation was not explored. Subsequently, related serpentoviruses have been discovered in additional snake species, turtles, with or without disease association [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Serpentoviruses are now regarded as significant respiratory pathogens of snakes, but their association with disease in other reptile species is less well established.…”