FeLV in a wild ocelot: proviral DNA detected without detectable RNA
Transboundary and emerging diseases · 2024
In plain language
A spleen sample from a wild ocelot contained feline leukaemia virus (FeLV) DNA, but no viral RNA was detected. The authors classified the infection as regressive, although there was no follow-up to establish whether that state continued. A fragment of the virus was similar to a sequence from a domestic cat, but this does not show how or in which direction transmission occurred. The finding comes from a single positive animal and cannot establish what happens in domestic cats.
Scientific detail
The study, published in Transboundary and emerging diseases in 2024 (doi: 10.1155/2024/3931047), initially sampled 30 individuals across five carnivoran families, including two ocelots. One jaguarundi spleen sample was excluded after failure of the β-actin mRNA control. The Results report one FeLV-positive ocelot as 1/29, although the Methods state that FeLV testing was restricted to felids. This is therefore not a felid-specific testing denominator and must not be interpreted as an estimate of prevalence among felids. The experiment type is not specified in the source object.
A spleen sample from a free-ranging ocelot tested positive for FeLV proviral DNA and negative for FeLV RNA. The authors classified the infection as regressive on the basis of this molecular profile. That classification does not provide longitudinal proof of persistent regression, permanent transcriptional silence or inability to reactivate. All three claims in the object carry evidence level D and concern a finding in a wild felid, not a domestic cat.
The ocelot-derived partial 569-nucleotide FeLV U3 (LTR)-gag sequence, OQ148669, showed 98.95% identity with sequence MT229941.1 from a domestic cat in Colombia. This value appears in the Results and Discussion and conflicts with the abstract's statement of 100% identity. The similarity is confined to the sequenced region: it does not establish whole-genome identity, equivalent promoter function, a specific FeLV subgroup or a demonstrated domestic-cat-to-ocelot transmission event.
The study does not report host–virus integration junctions, integration sites, proviral intactness, replication-competence assays or longitudinal measurements of viral expression. Its observations therefore do not establish a molecular mechanism of proviral persistence or the direction of transmission between domestic and wild felids. Detection of this viral region does not itself map chromosomal integration.
Limitations include a single FeLV-positive animal, no longitudinal follow-up, an unclear FeLV-specific denominator and the discrepancy in sequence-identity percentages. The authors state that rare encounters with these species and difficulty capturing ocelots hinder studies involving multiple individuals and restrict comprehensive conservation strategies; they also suggest that species-specific detection patterns may reflect the number of animals tested. Postmortem RNA degradation and limited viral RNA are described as possible obstacles to sequencing canine distemper virus (CDV), not as demonstrated explanations for the FeLV RNA-negative result.
What we know
At evidence level D, the study documents FeLV proviral DNA and no detectable FeLV RNA in a spleen sample from a wild ocelot. The authors classified this profile as regressive infection. A partial 569-nucleotide sequence showed 98.95% identity with a sequence from a domestic cat in Colombia, although the article's abstract states 100%. The 1/29 denominator cannot be used to estimate felid-specific prevalence.
What we don't know
It is not known whether the observed profile persisted over time, whether transcriptional silence was permanent or whether the infection could reactivate. Integration sites and junctions, proviral intactness, replication competence and a molecular mechanism of persistence were not determined. Whole-genome identity, equivalent promoter function, the FeLV subgroup and the direction of transmission were not established either. The study does not demonstrate why FeLV RNA was not detected and does not provide sufficient evidence to extrapolate this finding to domestic cats.
Evidence
EvidenceLevel D — Indirect evidence: other species or retrovirusConfidence 100/100
An ocelot spleen sample tested positive for FeLV proviral DNA and negative for FeLV RNA.
Excerpt verified in the source — verbatim, in the source's own language“A spleen sample (1/29; 3.45%) from an ocelot ( L. pardalis ) tested positive for FeLV proviral DNA and negative for RNA. The integrity of the sample was confirmed through the endogenous control test, utilizing RT-PCR for β -actin mRNA.”
This directly reports a DNA-positive/RNA-negative molecular finding in a wild ocelot, not a domestic cat. The reported 1/29 denominator must not be interpreted as felid-specific prevalence because FeLV testing was restricted to felids. Detection of the viral region does not itself map a chromosomal integration site or demonstrate an intact, replication-competent provirus. Level D follows the stipulated non-domestic-cat species cap; it does not mean that the ocelot observation is inferred.
EvidenceLevel D — Indirect evidence: other species or retrovirusConfidence 100/100
The authors classified the ocelot's FeLV infection as regressive on the basis of detected proviral DNA and absent RNA.
Excerpt verified in the source — verbatim, in the source's own language“FeLV infection in the present study was classified as regressive due to the presence of proviral DNA and the absence of RNA [ 92 ].”
This is the authors' classification of the observed molecular profile, not longitudinal proof of persistent regression, permanent transcriptional silence, or inability to reactivate. The observation concerns a wild ocelot; extrapolation to domestic cats would require separate evidence.
EvidenceLevel D — Indirect evidence: other species or retrovirusConfidence 100/100
The ocelot-derived 569-nucleotide FeLV U3 (LTR)-gag sequence OQ148669 showed 98.95% identity with domestic-cat sequence MT229941.1 from Colombia.
Excerpt verified in the source — verbatim, in the source's own language“The FeLV nucleotide sequence (569 nts) of the U3 (LTR)-gag gene obtained from ocelot ( OQ148669 ) showed 98.95% identity with a domestic cat from Colombia ( MT229941.1 ) ( Figure 3 ).”
This supports similarity in the sequenced viral region, not whole-genome identity, equivalent promoter function, a specific FeLV subgroup, or a demonstrated domestic-cat-to-ocelot transmission event. The Results and Discussion report 98.95%, conflicting with the abstract's 100% identity statement. The phylogenetic figure uses a 489-nucleotide alignment, distinct from the reported 569-nucleotide sequence.
Provenance
Source: Occurrence of Typical Domestic Animal Viruses in Wild Carnivorans: An Emerging Threat to the Conservation of Endangered Species.
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