Molecular detection and characterisation of Domestic Cat Hepadnavirus (DCH) from blood and liver tissues of cats in Malaysia

Abstract

Background A new domestic cat hepadnavirus (DCH, family Hepadnaviridae) was first reported from whole blood samples of domestic cats in Australia in 2018, and from cat serum samples in Italy in 2019. The pathogenesis of DCH is unknown, but it was reported in cats with viraemia (6.5–10.8%), chronic hepatitis (43%) and hepatocellular carcinoma (28%). Recent reports suggest that DCH resembles the human hepatitis B virus (HBV) and its related hepatopathies. This study aims to detect and characterize DCH among domestic cats in Malaysia. A cross-sectional study was performed on 253 cats, of which 87 had paired blood and liver samples, entailing whole-genome sequencing and phylogenetic analysis of DCH from a liver tissue sample. Results Among the 253 cats included in this study, 12.3% of the whole blood samples tested positive for DCH. The detection rate was significantly higher in pet cats (16.6%, n = 24/145) compared to shelter cats (6.5%, n = 7/108). Liver tissues showed higher a DCH detection rate (14.9%, n = 13/87) compared to blood; 5 out of these 13 cats tested positive for DCH in their paired liver and blood samples. Serum alanine transaminase (ALT) was elevated (> 95 units/L) in 12 out of the 23 DCH-positive cats (52.2%, p = 0.012). Whole-genome sequence analysis revealed that the Malaysian DCH strain, with a genome size of 3184 bp, had 98.3% and 97.5% nucleotide identities to the Australian and Italian strains, respectively. The phylogenetic analysis demonstrated that the Malaysian DCH genome was clustered closely to the Australian strain, suggesting that they belong to the same geographically-determined genetic pool (Australasia). Conclusions This study provided insights into a Malaysian DCH strain that was detected from a liver tissue. Interestingly, pet cats or cats with elevated ALT were significantly more likely to be DCH positive. Cats with positive DCH detection from liver tissues may not necessarily have viraemia. The impact of this virus on inducing liver diseases in felines warrants further investigation.

Emerging Hepatotropic Viruses in Cats: A Brief Review

“…DCH has a genome of approximately 3.2 kb of DNA, which similar to other hepadnaviruses, has four overlapping open reading frames (ORFs) encoding for the polymerase (L), surface (S), core (C) and X proteins. Genome sequences derived from DCH-positive domestic cats in Australia [ 18 ], Italy [ 20 ], and Malaysia [ 21 ], show 97.0–98.3% nucleotide similarity to each other. Recently a putative DCH recombinant strain was found in Thailand, suggesting a possible role of recombination in DCH evolution [ 22 ].…”

“…Subsequent screenings with molecular assays (degenerate PCR and real time PCR), carried out by independent research groups around the world, have revealed positivity rates of 6.5% (six in 54) in Australia [ 18 ], 10.8% (42 in 390) in Italy [ 20 ], 12.4% (26 in 209) in Thailand [ 22 ], and 12.3% (31 in 253) in Malaya [ 21 ] in whole blood and serum samples. Moreover, DCH DNA has been detected in liver tissue [ 21 , 23 ], with a higher positivity rate (14%; 13 in 84) than in blood/serum [ 21 ]. The formation and maturation of DCH particles in the nucleus and/or cytoplasm of infected hepatocytes suggests that hepatocytes are the initial localization of the virus as described in HBV infection [ 22 ].…”

“…DCH has been associated with feline retroviruses [ 18 , 20 , 21 , 22 ], since DCH prevalence is higher in FIV co-infected cats [ 21 ]. Since feline retroviruses cause impairment of the immune system [ 7 , 8 ], the detection of DCH in cats with retroviral infection could be related to the immunocompromised status, as observed for HBV [ 24 , 25 ].…”

“…Transmission of FIV/FeLV in cats occurs with similar modalities, as the virus is present in blood and body fluids [ 7 , 8 , 9 ]. Since DCH can be detected in serum and whole blood samples [ 18 , 20 , 21 , 22 ], similar modalities of transmission might also be hypothesized for DCH transmission [ 20 , 26 ]. However, in a longitudinal observational study in two cats naturally co-infected with DCH and feline retroviruses, oral, conjunctival, preputial, and rectal swabs repeatedly tested negative to DCH [ 26 ].…”

“…Cats older than two years have an approximately two-fold higher risk of DCH infection than younger cats [ 21 ]. In contrast, breed and gender are not risk factors for DCH infection, although male cats displayed higher prevalence rates than females [ 20 , 21 ]. Further investigations on the possible association of DCH with others risk factors is needed to elucidate the epidemiology of this virus.…”