Antibody response in snakes with boid inclusion body disease

Abstract

Boid Inclusion Body Disease (BIBD) is a potentially fatal disease reported in captive boid snakes worldwide that is caused by reptarenavirus infection. Although the detection of intracytoplasmic inclusion bodies (IB) in blood cells serves as the gold standard for the ante mortem diagnosis of BIBD, the mechanisms underlying IB formation and the pathogenesis of BIBD are unknown. Knowledge on the reptile immune system is sparse compared to the mammalian counterpart, and in particular the response towards reptarenavirus infection is practically unknown. Herein, we investigated a breeding collection of 70 Boa constrictor snakes for BIBD, reptarenavirus viraemia, anti-reptarenavirus IgM and IgY antibodies, and population parameters. Using NGS and RT-PCR on pooled blood samples of snakes with and without BIBD, we could identify three different reptarenavirus S segments in the collection. The examination of individual samples by RT-PCR indicated that the presence of University of Giessen virus (UGV)-like S segment strongly correlates with IB formation. We could also demonstrate a negative correlation between BIBD and the presence of anti-UGV NP IgY antibodies. Further evidence of an association between antibody response and BIBD is the finding that the level of anti-reptarenavirus antibodies measured by ELISA was lower in snakes with BIBD. Furthermore, female snakes had a significantly lower body weight when they had BIBD. Taken together our findings suggest that the detection of the UGV-/S6-like S segment and the presence of anti-reptarenavirus IgY antibodies might serve as a prognostic tool for predicting the development of BIBD.

Prevalence of inclusion body disease and associated comorbidity in captive collections of boid and pythonid snakes in Belgium

“…The overall prevalence of IBD and/or reptarenavirus infection in the present study was 19.2% with a remarkably high prevalence of IBD in boa constrictors (34.0%). Although, a proportionally larger number of boid species other than boa constrictors and pythonids tested reptarenavirus positive in previous screening studies [1,21,24,25], the number of positive snakes that were detected in these studies largely complies to our results. It should be noted, however, that these studies focused on a smaller number of snakes belonging to a single (zoological) collection [21,24,25] or a more limited number of snake collections [1].…”

“…reptarenavirus infection in snakes (P<0.0001). Although immunocompromised snakes may be more susceptible to reptarenavirus infection, the development of comorbidities as observed in this study may also be facilitated by the immunosuppression resulting from arenavirus infection as previously described in other animals with arenavirus infection [26] and recently in reptarenavirus infected boa constrictors [21]. As previously reported [1,24,25], it should be noted that many boa constrictors showed subclinical infections at the moment of sampling and although long-term follow-up was based on a sampling of a limited number of collections, our findings indicate that it may take several years before infection becomes clinical in IBD + or reptarenavirus infected snakes.…”

“…boa constrictors demonstrated inconsistency in anti-reptarenavirus antibody formation in infected snakes [22] and an apparent negative correlation between IBD and anti-reptarenavirus antibodies [21], serological testing could be attempted to detect (non-viraemic) reptarenavirus infection [21]. The use of oral and cloacal swabs as well as sampling of the esophageal tonsils for RT-PCR testing has been described and could increase the sensitivity of reptarenavirus infection testing in combination with other testing modalities [24,25].…”

“…It remains unclear, however, what primary clinical signs or comorbidities are truly associated with natural reptarenavirus infection and it seems to become more and more obvious that the disease may remain subclinical or show a slowly progressive course in infected snakes [1,5]. The influence of reptarenaviruses on the adaptive immune system of infected snakes has been studied and is likely to play an important role in the disease progression and the development of comorbidities [21,22]. The prevalence of reptarenavirus infection and IBD and the percentage of these asymptomatically infected snakes that eventually will develop clinical signs as well as their role in the disease epidemiology, however, needs to be further elucidated [1,5].…”

Experimental Reptarenavirus Infection of Boa constrictor and Python regius

“…The high genetic diversity makes nucleic acid-based diagnostic approaches to BIBD challenging, and thus the detection of reptarenavirus antigen (nucleoprotein, NP) serves as an alternative (6). Additionally, increasing evidence indicates that reptarenavirus infection is not always associated with detectable IBs (6, 13, 14), suggesting that the BIBD pathogenesis may involve additional factors. For example, we demonstrated vertical transmission of co-infecting reptarenavirus L and S segments with concurrent presence of IBs (15), and thus congenital, peri- or neonatal infection could be a prerequisite for IB formation.…”