A Novel Recombinant Canine Adenovirus Type 1 Detected from Acute Lethal Cases of Infectious Canine Hepatitis

E3 Gene-Based Genetic Characterization of Canine Adenovirus-2 Isolated from Cases of Canine Gastroenteritis in India Revealed a Novel Group of the Virus

Canine adenovirus (CAV) circulates as two distinct serotypes, CAV-1 and CAV-2, which are antigenically related but differ in their clinical manifestations. CAV is one of the important viral agents in the etiology of canine gastroenteritis. Here, we report the molecular surveillance and genetic characterization of CAV from clinical cases of canine gastroenteritis. A total of 302 fecal/rectal swabs were collected from dogs presented with gastroenteritis at various clinics in and around Hyderabad, India during 2018-19. These samples were tested for CAV using polymerase chain reaction with primers designed for the CAV E3 gene and the virus was isolated from positive samples. CAV-2 nucleic acid was present in 4.9% of the test samples. The partial sequence analyses of the E3 gene of the CAV-2 isolates revealed a frameshift mutation by insertion of nucleotide "G" at 1077 position of E3 gene, which resulted in an extension of the polypeptide chain by eleven amino acids. As a result, isolates from the current study formed a novel group, and the virus that was previously subdivided into two groups worldwide is now categorized under three. The study identifies a novel group of CAV-2 circulating in India providing an updated information regarding CAV-2.

Fowl Adenovirus (FAdV) Recombination with Intertypic Crossovers in Genomes of FAdV-D and FAdV-E, Displaying Hybrid Serological Phenotypes

After analyzing 27 new genomes from fowl adenovirus (FAdV) field isolates and so-far unsequenced prototypes, we report the first evidence for recombination in FAdVs. Recombination was confined to species FAdV-D and FAdV-E, accommodating the largest number of, and the intraspecies-wise most differentiated, types. The majority of detected events occurred in FAdV-E, involving segments with parental origin of all constitutive types. Together with the diversity of breakpoints, this suggests widespread recombination in this species. With possible constraints through species-specific genes and diversification patterns, the recombinogenic potential of FAdVs attains particular interest for inclusion body hepatitis (IBH), an important disease in chickens, caused by types from the recombination-prone species. Autonomously evolving, recombinant segments were associated with major sites under positive selection, among them the capsid protein hexon and fiber genes, the right-terminal ORFs 19, 25, and the ORF20/20A family. The observed mosaicism in genes indicated as targets of adaptive pressures points toward an immune evasion strategy. Intertypic hexon/fiber-recombinants demonstrated hybrid neutralization profiles, retrospectively explaining reported controversies on reference strains B3-A, T8-A, and X11-A. Furthermore, cross-neutralization supported sequence-based evidence for interdomain recombination in fiber and contributed to a tentatively new type. Overall, our findings challenge the purported uniformity of types responsible for IBH, urging more complete identification strategies for FAdVs. Finally, important consequences arise for in vivo studies investigating cross-protection against IBH.

Canine adenovirus type 1 causing neurological signs in a 5-week-old puppy

Background

Infectious canine hepatitis is a rarely encountered disease, that is caused by Canine Adenovirus-1. Clinical signs can vary dramatically, and neurological signs are rarely seen. Neurological manifestation of this disease is rarely reported in the veterinary literature.

Case presentation

A 5-week-old, male entire Husky cross puppy presented for a one-day history of abnormal neurological behaviour (circling, ataxia, vocalization and obtund mentation). The puppy was euthanized shortly after presentation due to rapid deterioration. Histopathology raised concerns for Canine Adenovirus 1 (CAdV-1) based on vasculitis in the brain and intranuclear inclusion bodies in endothelial cell and hepatocytes; immunohistochemistry on brain tissue confirmed CAdV-1 infection.

Conclusions

This report discusses possible routes of infection and manifestations of adenovirus infections causing neurologic signs. It also provides a timely reminder that CAdV-1 should be considered a differential in unvaccinated dogs that present with neurological signs. Further studies are required to better understand the neurotrophic tendencies of this virus.