Use of quantitative real-time RT-PCR to investigate the correlation between viremia and viral shedding of canine distemper virus, and infection outcomes in experimentally infected dogs

A recent distemper virus outbreak in the growing canine populations of Galapagos Islands: a persistent threat for the endangered Galapagos Sea Lion

Canine Distemper Virus (CDV) is a highly contagious virus that can cross mammalian species barriers and has widespread impacts on both domestic animals and wildlife populations. This study describes a recent outbreak of CDV in the Galapagos Islands in 2019. A total number of 125 dogs with clinical signs compatible with CDV were included in this study. Nasal swabs were taken and analyzed by RT-qPCR for the detection of CDV, resulting in a positivity rate of 74.4% (IC95%, 66-81%). Among the CDV positive dogs, 82.2% presented with respiratory signs, 48.8% neurological signs, and 28.9% gastrointestinal signs. CDV has been previously reported in the domestic canine population of the Galapagos Islands in 2001 and 2004. The current study shows how CDV is still a threat for the endemic and endangered Galapagos sea lion, despite recent policies for dog population control and CDV vaccination.

Prolonged persistence of canine distemper virus RNA, and virus isolation in naturally infected shelter dogs

Canine distemper virus remains an important source of morbidity and mortality in animal shelters. RT-PCR is commonly used to aid diagnosis and has been used to monitor dogs testing positive over time to gauge the end of infectious potential. Many dogs excrete viral RNA for prolonged periods which has complicated disease management. The goal of this retrospective study was to describe the duration and characteristics of viral RNA excretion in shelter dogs with naturally occurring CDV and investigate the relationship between that viral RNA excretion and infectious potential using virus isolation data. Records from 98 different humane organizations with suspect CDV were reviewed. A total of 5,920 dogs were tested with 1,393; 4,452; and 75 found to be positive, negative, or suspect on RT-PCR respectively. The median duration of a positive test was 34 days (n = 325), and 25% (82/325) of the dogs still excreting viral RNA after 62 days of monitoring. Virus isolation was performed in six dogs who were RT-PCR positive for > 60 days. Infectious virus was isolated only within the first two weeks of monitoring at or around the peak viral RNA excretion (as detected by the lowest cycle threshold) reported for each dog. Our findings suggest that peak viral RNA excretion and the days surrounding it might be used as a functional marker to gauge the end of infectious risk. Clarifying the earliest point in time when dogs testing positive for canine distemper by RT-PCR can be considered non-contagious will improve welfare and lifesaving potential of shelters by enabling recovered dogs to be cleared more quickly for live release outcomes.

Canine morbillivirus (CDV): a review on current status, emergence and the diagnostics

The increasing host range of canine morbillivirus (CDV) affecting important wildlife species such as Lions, Leopard, and Red Pandas has raised the concern. Canine distemper is a pathogen of dogs affecting the respiratory, gastrointestinal, and nervous systems. Seventeen lineages of CDV are reported, and the eighteenth lineage was proposed in 2019 from India. Marked genomic differences in the genome of wild-type virus and vaccine strain are also reported.The variations at the epitope level can be differentiated using specific monoclonal antibodies in neutralization tests. Keeping in mind the current status of the emergence of CDV, genetic and molecular study of circulating strains of the specific geographical region are the essential components of the disease control strategy. New target-based diagnostics and vaccines are in need to counter the effects of the emerging virus population. Control of CDV is necessary to save the endangered, vulnerable, and many other wildlife species to maintain balance in the ecological system. This review provides an overview on emergence reported in CDV, diagnostics developed till today, and a perspective on the disease control strategy, keeping wildlife in consideration.

In Vitro Growth, Receptor Usage and Pathogenesis of Feline Morbillivirus in the Natural Host

Feline morbillivirus (FeMV) is a recently discovered virus belonging to the genus Morbillivirus of the virus family Paramyxoviridae. Often, the virus has been detected in urine of cats with a history of urinary disease and has a worldwide distribution. Currently, it is unclear which receptor the virus uses to enter the target cells. Furthermore, many aspects of FeMV biology in vivo, including tissue tropism, pathogenesis, and virus excretion in the natural host remain unclear. In this study we analyzed the replication of FeMV in various cell lines. Secondly, we tested if the presence of feline SLAMF1 (Signaling Lymphocytic Activation Molecule family 1/CD150, principal entry receptor for other members of the Morbillivirus genus) improved FeMV replication efficiency in vitro. Finally, to elucidate in vivo biology in cats, as a natural host for FeMV, we experimentally infected a group of cats and monitored clinical symptoms, viremia, and excretion of the virus during the course of 56 days. Our study showed that FeMV shares some features with other morbilliviruses like the use of the SLAMF1 receptor. For the first time, experimental infection of SPF cats showed that FeMV does not induce an acute clinical disease like other morbilliviruses but can induce lesions in the kidneys, including tubulointerstitial nephritis. Further investigations are needed to confirm the site and dynamics of replication of FeMV in the urinary tract and the longer-term impact of FeMV-induced lesions on the renal function. Whether FeMV infection can result in chronic kidney disease will require the monitoring of cats over a longer period.